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Mineral Tolerance of Animals: Second Revised
Edition
Committee on Minerals and Toxic Substances in Diets
and Water for Animals, National Research Council
ISBN:0-309-55027-0, 510pages, 8 1/2x11, (2005)
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THE NATIONAL ACADEMIES
Advisers to the Nation on Science, Engineering, and Medicine
MinemI Tnlemnce nf Animals- Sennnd Revised Edition
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MINERAL TOLERANCE
OF ANIMALS
SECOND REVISED EDITION, 2005
Committee on Minerals and Toxic Substances in
Diets and Water for Animals
Board on Agriculture and Natural Resources
Division on Earth and Life Studies
NATIONAL RESEARCH COUNCIL
OF THE NATIONAL ACADEMIES
THE NATIONAL ACADEMIES PRESS
Washington, D.C.
vnwN^.nap.edu
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THE NATIONAL ACADEMIES PRESS • 500 Fifth Street, N.W. • Washington, DC 20001
NOTICE: The project that is the subject of this report was approved by the Governing Board of the
National Research Council, whose members are drawn from the councils of the National Academy of
Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the
committee responsible for the report were chosen for their special competences and with regard for appro-
priate balance.
This study was supported by Contract/Grant No. 223-01-2460 between the National Academy of
Sciences and the Center for Veterinary Medicine of the U.S. Food and Drug Administration, Department
of Health and Human Services. Any opinions, findings, conclusions, or recommendations expressed in
this publication are those of the author(s) and do not necessarily reflect the views of the organizations or
agencies that provided support for the project.
Library of Congress Cataloging-in-Publication Data
Mineral tolerance of animals / Committee on Minerals and Toxic Substances, Board on Agriculture and
Natural Resources, Division on Earth and Life Studies. — 2nd rev. ed.
p. cm.
Rev. ed. of: Mineral tolerance of domestic animals / National Research Council (U.S.). Subcommittee on
Mineral Toxicity in Animals. 1980.
Includes bibliographical references and index.
ISBN 0-309-09654-5 (pbk.) — ISBN 0-309-55027-0 (pdf) 1. Veterinary toxicology. 2. Minerals in
animal nutrition. I. National Research Council (U.S.). Committee on Minerals and Toxic Substances. II.
National Research Council (U.S.). Subcommittee on Mineral Toxicity in Animals. Mineral tolerance of
domestic animals.
SF757.5M56 2005
636.089'59— dc22
2005024930
Additional copies of this report are available from the National Academies Press, 500 Fifth Street, N.W.,
Lockbox 285, Washington, DC 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropoli-
tan area); Internet, http://www.nap.edu
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Printed in the United States of America
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THE NATIONAL ACADEMIES
Advisers fo fhe Nation on Science, Engineering, and Medicine
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of
distinguistied schiolars engaged in scientific and engineering research, dedicated to the fur-
therance of science and technology and to their use for the general welfare. Upon the
authority of the charter granted to it by the Congress in 1863, the Academy has a mandate
that requires it to advise the federal government on scientific and technical matters. Dr.
Ralph J. Cicerone is president of the National Academy of Sciences.
The National Academy of Engineering was established in 1964, under the charter of the
National Academy of Sciences, as a parallel organization of outstanding engineers. It is
autonomous in its administration and in the selection of its members, sharing with the Na-
tional Academy of Sciences the responsibility for advising the federal government. The
National Academy of Engineering also sponsors engineering programs aimed at meeting
national needs, encourages education and research, and recognizes the superior achieve-
ments of engineers. Dr. Wm. A. Wulf is president of the National Academy of Engineering.
The Institute of Medicine was established in 1970 by the National Academy of Sciences to
secure the services of eminent members of appropriate professions in the examination of
policy matters pertaining to the health of the public. The Institute acts under the responsibil-
ity given to the National Academy of Sciences by its congressional charter to be an adviser
to the federal government and, upon its own initiative, to identify issues of medical care,
research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine.
The National Research Council was organized by the National Academy of Sciences in
1916 to associate the broad community of science and technology with the Academy's
purposes of furthering knowledge and advising the federal government. Functioning in
accordance with general policies determined by the Academy, the Council has become the
principal operating agency of both the National Academy of Sciences and the National
Academy of Engineering in providing services to the government, the public, and the scien-
tific and engineering communities. The Council is administered jointly by both Academies
and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Wm. A. Wulf are chair and vice
chair, respectively, of the National Research Council.
www.national-academies.org
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COMMITTEE ON MINERALS AND TOXIC SUBSTANCES IN
DIETS AND WATER FOR ANIMALS
KIRK C. KLASING, Chair, University of California, Davis
JESSE P. GOFF, U.S. Department of Agriculture, Agricultural Research Service,
Ames, Iowa
JANET L. GREGER, University of Connecticut, Storrs
JANET C. KING, Children's Hospital Oakland Research Institute, Oakland, California
SANTOSH P. LALL, Institute for Marine Biosciences, National Research Council of
Canada, Halifax, Nova Scotia
XINGEN G. LEI, Cornell University, Ithaca, New York
JAMES G. LINN, University of Minnesota, St. Paul
FORREST H. NIELSEN, U.S. Department of Agriculture, Agricultural Research Service,
Grand Forks, North Dakota
JERRY W. SPEARS, North Carolina State University, Raleigh
Staff
AUSTIN J. LEWIS, Study Director
JAMIE S. JONKER, Study Director*
DONNA LEE JAMEISON, Senior Program Assistant
PEGGY TSAI, Research Associate
*Througli June 2004
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BOARD ON AGRICULTURE AND NATURAL RESOURCES
MAY R. BERENBAUM, Chair, University of Illinois, Urbana-Champaign
SANDRA J. BARTHOLMEY, University of Illinois at Chicago
ROGER N. BEACHY, Donald Danforth Plant Science Center, St. Louis, Missouri
H. H. CHENG, University of Minnesota, St. Paul
W. R. (REG) GOMES, University of California, Oakland
ARTURO GOMEZ-POMPA, University of California, Riverside
PERRY R. HAGENSTEIN, Institute for Forest Analysis, Planning, and Policy,
Wayland, Massachusetts
JEAN HALLORAN, Consumer Policy Institute/Consumers Union, Yonkers, New York
HANS R. HERREN, Millennium Institute, Arlington, Virginia
DANIEL P. LOUCKS, Cornell University, Ithaca, New York
WHITNEY MACMILLAN, Cargill, Incorporated, Minneapohs, Minnesota
BRIAN W. MCBRIDE, University of Guelph, Guelph, Canada
TERRY L. MEDLEY, E. I. duPont de Nemours & Co., Wilmington, Delaware
OLE NIELSEN, Ontario Veterinary College, Spruce Grove, Canada
ROBERT PAARLBERG, Wellesley College, Watertown, Massachusetts
ALICE N. PELL, Cornell University, Ithaca, New York
BOBBY PHILLS, Florida A&M University, Tallahassee
PEDRO A. SANCHEZ, The Earth Institute at Columbia University, Pahsades, New York
SONY A B. SAL AM ON, University of Illinois, Urbana-Champaign
B. L. TURNER, II, Clark University, Worcester, Massachusetts
TILAHUN D. YILMA, University of California, Davis
JAW-KAI WANG, University of Hawaii, Honolulu
Staff
ROBIN A. SCHOEN, Director
CHARLOTTE KIRK BAER, Director*
KAREN L. IMHOF, Administrative Assistant
*Through October 2004
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Acknowledgments
The committee would like to thank Charlotte Kirk Baer
and Robin Schoen, board directors, and Austin Lewis and
Jamie Jonker, program officers, for their cheerful and expert
guidance during this project. The committee also wishes to
thank Gretchen Hill and Marcia Carlson Shannon for assis-
tance with the chapters on iron and zinc and Katherine
Mahaffey for helpful discussions on levels of minerals that
are of concern for human health. Finally, we greatly appreci-
ate the help of Donna Jameison, Marina Peunova-Conner,
and Peggy Tsai for their support of our communications,
meetings, and writings.
The sponsorship of this study by the Center for Veteri-
nary Medicine of the U.S. Food and Drug Administration
(FDA) is gratefully acknowledged. The support of the FDA
liaison, William D. Price, was especially appreciated.
This report has been reviewed in draft form by individu-
als chosen for their diverse perspectives and technical exper-
tise, in accordance with procedures approved by the NRC's
Report Review Committee. The purpose of this independent
review is to provide candid and critical comments that will
assist the institution in making its published reports as sound
as possible and to ensure that the report meets institutional
standards for objectivity, evidence, and responsiveness to
the study charge. The review comments and draft manu-
script remain confidential to protect the integrity of the de-
liberative process. We wish to thank the following individu-
als for their review of this report:
Clarence B. Ammerman, University of Florida,
Gainesville, FL
Dennis J. Blodgett, Virginia Tech University,
Blacksburg, VA
Gerry F. Combs, USDA, Grand Forks, ND
Gail L. Czarnecki-Maulden, Nestle Purina Research,
St. Joseph, MO
L. Wayne Greene, Texas A&M University,
Amarillo, TX
Pamela Henry Miles, University of Florida,
Gainesville, FL
Mark P. Richards, USDA, ARS, Beltsville, MD
Kristi Smedley, Center for Regulatory Services,
Woodbridge, VA
Patricia A. Talcott, University of Idaho, Moscow, ID
Duane E. Ullrey, Michigan State University, East
Lansing, MI
William P. Weiss, The Ohio State University,
Wooster, OH
Although the reviewers listed above provided many con-
structive comments and suggestions, they were not asked to
endorse the conclusions or recommendations nor did they
see the final draft of the report before its release. The review
of this report was overseen by Gary L. Cromwell, University
of Kentucky. Appointed by the National Research Council,
he was responsible for making certain that an independent
examination of the report was carried out in accordance with
institutional procedures and that all review comments were
carefully considered. Responsibility for the final content of
this report rests entirely with the authoring committee and
the institution.
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Preface
In 2003, the National Research Council's Committee on
Animal Nutrition convened an ad hoc committee to conduct
a thorough review of the scientific literature related to min-
erals and toxic substances in the diets and water for animals
and to update the 1980 edition of Mineral Tolerance of Do-
mestic Animals. In particular, the committee was asked to
provide recommendations on animal tolerances and toxic
dietary levels, and identify minerals that pose potential hu-
man health concerns. A nine-person committee of scientists
specializing in nutrition, toxicology, and veterinary medi-
cine accepted this task. Individual members brought to this
project diverse expertise and perspective on the impact of
nutrition on the health of fish, poultry, livestock, compan-
ion animals, and humans. The committee met three times
and had monthly teleconferences over a period of more than
a year.
The challenge of making recommendations on the toler-
able and toxic levels of close to 40 elements for a variety of
species is daunting. Each of these elements exists in many
chemical forms, each with differing properties and toxicity
profiles, further complicating the task. The toxicity profile
of some minerals is very well described, whereas the toxic-
ity of other minerals, especially to livestock and companion
animals, has received little attention. A wide variety of in-
formational sources, ranging from government surveys to
professional experiences, was considered for this report.
Expert reports on several minerals were also solicited. How-
ever, the backbone of this report is the primary literature of
peer-reviewed journal publications. The committee recog-
nized that much of the information in the 1980 publication
was still relevant, but that this historic foundation needed to
be reevaluated in the context of newer infonnation on the
methods of mineral analysis, mechanisms of homeostasis
and toxicity, and appropriate indices of animal health and
well-being. Consequently, a reanalysis of the historic litera-
ture is synthesized with the recent literature to form the rec-
ommendations in this report. This edition considers a greater
breadth of animal species than the past edition and expands
the coverage on the metabolism and mechanisms of toxicity
of minerals, methods and problems in mineral analysis, and
the relationships between mineral exposure of animals and
the mineral levels in animal products destined for human
consumption. New chapters provide additional focus on
acid-base balance, nitrates, and water quality. Finally, this
edition has placed increased emphasis on the safety of ani-
mal products in the human diet as criteria for setting maxi-
mum tolerable levels of minerals in the feed and water of
farm animals.
The recommendations in the 1980 report have been
widely cited and served as the basis of decisions made by
regulatory agencies and by practicing nutritionists respon-
sible for the formulation of animal diets. The previous report
has also been used extensively in teaching, research, and
veterinary practice. We hope that the utility of this new edi-
tion equals or surpasses its predecessor.
KIRK C. KLASING, Chair
Committee on Minerals and Toxic Substances in Diets
and Water for Animals
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Contents
SUMMARY 1
1 INTRODUCTION 7
2 MAXIMUM TOLERABLE LEVELS 10
3 ALUMINUM 15
4 ARSENIC 31
5 BARIUM 46
6 BISMUTH 54
7 BORON 60
8 BROMINE 72
9 CADMIUM 79
10 CALCIUM 97
11 CHROMIUM 115
12 COBALT 124
13 COPPER 134
14 FLUORINE 154
15 IODINE 182
16 IRON 199
17 LEAD 210
18 MAGNESIUM 224
19 MANGANESE 235
20 MERCURY 248
21 MOLYBDENUM 262
22 NICKEL 276
23 PHOSPHORUS 290
24 POTASSIUM 306
25 SELENIUM 321
26 SILICON 348
27 SODIUM CHLORIDE 357
28 SULFUR 372
29 TIN 386
30 VANADIUM 398
31 ZINC 413
32 OTHER MINERALS 428
33 MINERALS AND ACID-BASE BALANCE 449
34 NITRATES AND NITRITES 453
35 WATER AS A SOURCE OF TOXIC SUBSTANCES 469
ABOUT THE AUTHORS 477
INDEX 479
BOARD ON AGRICULTURE AND NATURAL RESOURCES PUBLICATIONS 495
xi
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Tables and Figures
TABLES
S-l Summary of Minerals Reviewed in This Report 6
2-1 Maximum Tolerable Levels of Minerals in the Feed (mg/kg or % of the DM) of Animals Based on
Indexes of Animal Health 13
2-2 Toxicity Assessments of Nutrients for Humans Based on Food and Nutrition Board Assessments 14
3-1 Effects of Aluminum Exposure in Animals 27
3-2 Aluminum Concentrations in Fluids and Tissues of Animals 30
4-1 Effects of Arsenic Exposure in Animals 42
4-2 Arsenic Concentrations in Fluids and Tissues of Animals 45
5-1 Effects of Barium Exposure in Animals 51
5-2 Barium Concentrations in Fluids and Tissues of Animals 53
6-1 Effects of Bismuth Exposure in Animals 58
6-2 Bismuth Concentrations in Fluids and Tissues of Animals 59
7-1 Effects of Boron Exposure in Animals 68
7-2 Boron Concentrations in Fluids and Tissues of Animals 71
8-1 Effects of Bromine Exposure in Animals 77
8-2 Bromine Concentrations in Fluids and Tissues of Animals 78
9-1 Effects of Cadmium Exposure in Animals 91
9-2 Cadmium Concentrations in Fluids and Tissues of Animals 94
10-1 Effects of Calcium Exposure in Animals 109
10-2 Calcium Concentrations in Fluids and Tissues of Animals 1 14
11-1 Effects of Chromium Exposure in Animals 121
11-2 Chromium Concentrations in Fluids and Tissues of Animals 123
12-1 Effects of Cobalt Exposure in Animals 130
12-2 Cobalt Concentrations in Fluids and Tissues of Animals 133
Xll
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TABLES AND FIGURES
13-1 Effects of Copper Exposure in Animals 147
13-2 Copper Concentrations in Fluids and Tissues of Animals 153
14-1 Effects of Fluorine Exposure in Animals 169
14-2 Fluorine Concentrations in Fluids and Tissues of Animals 181
15-1 Effects of Iodine Exposure in Animals 194
15-2 Iodine Concentrations in Fluids and Tissues of Animals 198
16-1 Effects of Iron Exposure in Animals 208
16-2 Iron Concentrations in Fluids and Tissues of Animals 209
17-1 Effects of Lead Exposure in Animals 221
17-2 Lead Concentrations in Fluids and Tissues of Animals 223
18-1 Effects of Magnesium Exposure on Animals 232
18-2 Magnesium Concentrations in Fluids and Tissues of Animals 234
18-3 Tissue Magnesium Concentrations in Steers Fed Different Dietary Levels of Magnesium 234
19-1 Effects of Manganese Exposure in Animals 243
19-2 Manganese Concentrations in Fluids and Tissues of Animals 247
20-1 Effects of Mercury Exposure in Animals 259
20-2 Mercury Concentrations in Fluids and Tissues of Animals 261
21-1 Effects of Molybdenum Exposure in Animals 271
21-2 Molybdenum Concentrations in Fluids and Tissues of Animals 274
22-1 Effects of Nickel Exposure in Animals 284
22-2 Nickel Concentrations in Fluids and Tissues of Animals 288
23-1 Effects of Phosphorus Exposure in Animals 300
23-2 Phosphorus Concentrations in Fluids and Tissues of Animals 303
24-1 Effects of Potassium Exposure in Animals 314
25-1 Effects of Selenium Exposure in Animals 337
25-2 Selenium Concentrations in Fluids and Tissues of Animals 344
26-1 Effects of Silicon Exposure in Animals 355
26-2 Silicon Concentrations in Fluids and Tissues of Animals 356
27-1 Single Oral Dose Salt Toxicity 367
27-2 Acute Salt Toxicity 368
27-3 Chronic Salt Toxicity 369
27-4 Sodium and Chloride Concentrations in Fluids and Tissues of Animals 371
28-1 Effects of Sulfur Exposure in Animals 381
28-2 Sulfur Concentrations in Tissues of Sheep 385
29-1 Effects of Tin Exposure in Animals 395
29-2 Tin Concentrations in Fluids and Tissues of Animals 397
30-1 Effects of Vanadium Exposure in Animals 405
30-2 Vanadium Concentrations in Selected Tissues of Animals 410
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xiv TABLES AND FIGURES
30-3 Vanadium Concentrations in Otlier Fluids and Tissues of Animals 412
31-1 Effects of Zinc Exposure in Animals 423
31-2 Zinc Concentrations in Fluids and Tissues of Animals 426
34-1 Effects of Nitrate or Nitrite Exposure in Animals 461
35-1 Sources and Normal Ranges of Minerals in Unpolluted Fresh Water 473
35-2 Range or Mean of Mineral Concentrations Found in Sea Water 473
35-3 Major Mineral Species Found in Fresh and Sea Water 474
35-4 Drinking Water Standards for Humans and Livestock 475
35-5 Range or Mean of Mineral Concentrations Found in Fresh and Salt Water 476
FIGURE
1-1 Mineral Concentrations and Animal Health 8
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Summary
BACKGROUND
Inorganic elements found in the Eartli's crust are often
referred to as minerals. Some minerals are essential for
health and productivity of animals and have well-defined
nutritional and biochemical roles. Many other minerals
naturally occur at trace levels in the foods and tissues of
animals but are not typically suspected to play a useful nu-
tritional purpose and are considered incidental contami-
nants. However, all minerals, whether essential or nones-
sential, can adversely affect an animal when amounts in the
diet and water become excessive, so the prevention of min-
eral toxicosis is a fundamental part of animal nutrition and
management. Establishing the levels at which each mineral
becomes toxic to animals aids nutritionists, veterinarians,
toxicologists, government regulators, and ranchers and other
animal owners to safeguard the feed that animals consume
and the water that they drink to optimize animal health and
minimize tissue residues.
In 1980, the National Research Council published Min-
eral Tolerance of Domestic Animals, which reviewed and
evaluated the literature relating to mineral tolerance of do-
mestic animals and set maximum tolerable levels of dietary
minerals in feeds. Since that time, there have been important
developments in nutrition and toxicology that compel a re-
evaluation of mineral tolerances of animals. These develop-
ments include the following:
• Improvements in the sensitivity and specificity of
analysis of mineral concentrations in feeds and animal
tissues;
• New information on the bioavailability, homeostasis,
and mechanism of toxicity of minerals;
• New understandings of appropriate indices of animal
health and well-being;
• Increased disposal of municipal and animal wastes on
crop lands and pastures, potentially resulting in greater ex-
posure of animals to certain minerals;
• Increased feeding of recycled animal by-products and
wastes that contain high levels of certain minerals;
• Emergence of the aquaculture industry;
• Increased evidence for potentially toxic levels of mer-
cury, cadmium, lead, and other minerals in the diet of hu-
mans and companion animals;
• Refinements in the Recommended Dietary Allowances
and the Tolerable Upper Intake Levels of minerals for hu-
mans that permit more precise evaluation of potentially toxic
mineral levels in foods of animal origin;
• New appreciation of the impact of minerals on environ-
mental quality.
Preventing adverse effects of minerals on the health of
animals, consumers, and the environment requires the appli-
cation of appropriate nutritional and toxicological principles
to set limits on mineral exposure to animals. To address this
need, the Food and Drug Administration of the U.S. Depart-
ment of Health and Human Services asked the National
Academy of Sciences to convene a committee of scientific
experts to make recommendations on animal tolerances and
toxic dietary levels. A subcommittee of the Committee on
Animal Nutrition undertook this task. The subcommittee
consisted of nine scientists specializing in nutrition, toxicol-
ogy, and veterinary medicine, with diverse expertise and
perspectives on the impact of nutrition on the health of fish,
poultry, livestock, companion animals, and humans.
COMMITTEE CHARGE AND APPROACH
The committee was given the following task: "An ad hoc
committee of the standing Committee on Animal Nutrition
will be convened to conduct a thorough review of the scien-
tific literature on trace elements and macro minerals, includ-
ing an analysis of the effects of exposure and toxic levels in
animal diets; provide recommendations on animal tolerances
and toxic dietary levels, and identify elements that pose po-
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MINERAL TOLERANCE OF ANIMALS
tential human health concerns. The report will address re-
cent research on tolerance and toxicity of minerals in animal
diets including the following areas: general considerations;
mineral sources, discrepancies and difficulties in methods of
analyses and evaluation of biological status; metabolic min-
eral interactions; assessments of form and species interac-
tions; supplementation considerations; bioavailability of dif-
ferent mineral forms and sources; maximal tolerable levels;
and effects of diet composition, stressors, and animal physi-
ological status on mineral utilization; and environmental
exposure considerations. The report will include all species
for which adequate information is available — updating the
previous report, greatly expanding the topics covered, and
increasing the usefulness of the report. Recommendations
will be provided on maximum tolerable and toxic dietary
levels of minerals in animal diets. Potential for toxic expo-
sure, toxicosis, factors affecting toxicity, and essentiality of
dietary minerals in various animal species will be discussed."
This report is based mostly on the primary literature of
peer-reviewed journal publications. The committee recog-
nized that much of the information in the 1980 publication
was still relevant, but that this historic foundation needed to
be reevaluated in the context of newer infonnation on the
methods of mineral analysis, mechanisms of homeostasis and
toxicity, and appropriate indices of animal health and well-
being. Consequently, a reanalysis of the historic literature is
synthesized with the recent literature to form the recommen-
dations in this report. In addition, this report considers a greater
breadth of animal species than the past edition and expands
the coverage on the metabolism and mechanisms of toxicity
of minerals, methods and problems in mineral analysis, and
the relationships between mineral exposure of animals and the
mineral levels in animal products destined for human con-
sumption. New chapters provide additional focus on acid-base
balance, nitrates, water quality, and rare earth metals.
ESSENTIALITY
The essential minerals are those that have well-defined bio-
chemical roles and must be in the diet of vertebrates for opti-
mum health and productivity. Minerals play many vital roles:
for example, they activate many proteins including enzymes,
maintain the ionic and pH balance, provide for the structural
rigidity of bones and teeth, and serve as regulatory signals in
metabolic homeostasis. Inadequate dietary concentrations of
essential minerals compromise animal growth, reproduction,
and health. As shown in Table S-1, the committee identified
• Seventeen minerals that are required by vertebrates:
calcium, chlorine, chromium, cobalt, copper, fluorine, io-
dine, iron, magnesium, manganese, molybdenum, phospho-
rus, potassium, selenium, sodium, sulfur, and zinc;
• Six additional minerals that may be required based on
experiments that indicate beneficial effects when supple-
mented to the diet: arsenic, boron, nickel, rubidium, silicon,
and vanadium. However, specific biochemical functions
have not been identified for these six, and there is not a con-
sensus among nutritionists that these minerals are essential.
EXPOSURE
Animals may be exposed to toxic levels of minerals from
a wide variety of sources. Feedstuffs, especially those de-
rived from plants, are a common source of potentially toxic
levels of minerals. Molybdenum and selenium occur natu-
rally in soils of some regions at concentrations sufficient to
cause certain plants to accumulate levels that can be toxic
for animals. High soil, and consequently plant, concentra-
tions of cadmium, lead, molybdenum, copper, and zinc are
the primary minerals of concern from the application of
municipal wastes and other biosolids to the land. Mining,
smelting, and other industries are often associated with local
areas of mineral contamination to the water, soil, and air,
and, ultimately, the plants grown in that area. Feedstuffs of
animal origin may also be sources of toxic levels of miner-
als. For example, some types of fishmeals may be high in
mercury because mercury bioconcentrates through the
aquatic food chain.
Mineral supplements are commonly added to animal di-
ets to correct deficiencies found in pastures, forages, and
other dietary ingredients. Some mineral supplements may
contain potentially toxic levels of contaminating minerals,
depending upon the source of the supplement and the method
of its processing. Toxic levels of minerals may accidentally
occur due to mistakes in feed formulation and manufactur-
ing, or from contamination during storage or transportation.
Such accidental administration can result in very high min-
eral levels and cause acute toxicosis and death, whereas most
other modes of introduction typically cause toxicosis only
after chronic exposure. Surface water and occasionally even
deep-well or domestic water supplies may contain excessive
levels of certain minerals due to naturally high levels in the
ground. Sulfur, sodium, manganese, selenium, and fluorine
are among the minerals most likely to reach toxic levels in
natural water supplies. Minerals may also be introduced into
water supplies from industrial wastes, pesticide contamina-
tion, and other sources of pollution. Finally, minerals such
as arsenic, bromine, bismuth, copper, lithium, magnesium,
silver, zinc, and some of the rare earths are sometimes added
to feed or water as therapeutics or for growth promotion.
Mistakes in use of these minerals have occasionally resulted
in toxicoses.
TOXICITY
The committee looked at two main aspects of the effects
of toxicity on animals: the mechanisms of toxicity of each
mineral and the maximum tolerable level that will not impair
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SUMMARY
animal health or performance. The individual chapters de-
scribe findings in each of these areas. Some general conclu-
sions are summarized below.
Mechanisms of Toxicity
The adverse effects of minerals depend on the dietary
concentration and length of exposure and range from subtle
effects on homeostatic processes, to impairments in animal
growth or reproductive rates, to specific pathologies and
death. An understanding of the biochemical or physiological
mechanism by which a mineral exerts its detrimental effect
is useful in diagnosing toxicity problems and in designing
research to identify the level at which that mineral becomes
toxic. Although the means by which minerals cause their
toxic effects are diverse, several general mechanisms are
common. Some minerals cause oxidative damage to cellular
macromolecules, either by their propensity to undergo redox
reactions or by binding to and deactivating antioxidant mol-
ecules or enzymes. This property contributes to the toxicity
of arsenic, cadmium, chromium, copper, cobalt, lead, iron,
mercury, nickel, selenium, and vanadium.
Many minerals antagonize chemically related minerals
that are nutritionally essential by impairing their absorption,
transport, excretion, or incorporation into active sites of
molecules. Aluminum, arsenic, bromide, cadmium, calcium,
copper, lead, manganese, mercury, molybdenum, nickel,
phosphorus, selenium, silver, strontium, sulfur, tin, tungsten,
and zinc antagonize the homeostasis of at least one other
mineral. Minerals that exert toxic effects by disturbing acid-
base homeostasis include calcium, chloride, magnesium,
phosphorus, potassium, sodium, and sulfur. Electrolyte bal-
ance can be disrupted by magnesium, potassium, sodium,
bromine, and chloride. The toxic effects of chromium and
vanadium are at least partly due to their ability to mimic or
potentiate the action of hormones.
Individuals are often most sensitive to toxicity during
embryonic development, growth, and periods of stress such
as infections or trauma. Tolerance to minerals usually in-
creases with age. Healthy, mature animals are often most
resistant to mineral toxicoses because they have passed im-
portant developmental events, their homeostatic mechanisms
are well developed, and their relative rates of feed intake are
low. However, cadmium and mercury are not easily excreted,
and they can accumulate during an animal's lifetime result-
ing in toxic effects in older animals.
IVIaximum Tolerable Levels
The "maximum tolerable level" (MTL) of a mineral is
defined as the dietary level that, when fed for a defined pe-
riod of time, will not impair animal health or performance).
Tolerable mineral levels are typically distinguished from
toxic levels in experiments that use incremental additions of
the mineral of concern to the diet or the water and measure
the impact on performance and pathological signs of toxico-
sis. The duration of exposure to the test mineral markedly
influences the level that causes toxicosis. The committee
considered three exposure durations: a single dose, acute
exposure, and chronic exposure. A single dose is defined as
exposure due to the consumption of a single meal or by a
single gavage of the mineral. Acute exposure is defined as
an intake of 10 days or less. Chronic exposure is set as an
exposure of 10 days or more but emphasis is given to the
studies that had the longest durations of exposure. In this
report, MTL recommendations for 38 minerals are provided,
which is seven more than included in the 1980 Mineral Tol-
erance of Domestic Animals. When information is available,
MTL are given for fish, rodents, and companion animals, in
addition to the poultry and livestock species considered in
the previous report. Research on mineral toxicities in do-
mestic animals conducted during the past 25 years has re-
sulted in adjustments to many of the MTL provided in the
1980 report. The previous report adjusted the MTL for lead
and mercury in order to decrease tissue residues, but those
recommendations were not based on animal health. Further-
more, the rationale for those adjustments was not provided.
The current MTL are based solely on considerations of ani-
mal health. As compared to the 1980 report, the recom-
mended MTL based on indices of animal health were
• Not changed appreciably for 8 minerals: boron, bro-
mine, iodine, silicon, silver, sulfur, tungsten, and vanadium;
• Increased for 13 minerals: aluminum (nonruminants),
barium, bismuth, cadmium, calcium (poultry), cobalt, fluo-
rine (cattle), lead (ruminants), magnesium, manganese (ru-
minants and swine), molybdenum (swine), nickel (ruminants
and swine), and selenium;
• Decreased for sodium chloride and 12 minerals: ar-
senic, calcium (ruminants), chromium, copper, iron (cattle
and poultry), lead (nonruminants), mercury, molybdenum
(ruminants), phosphorus (cattle and swine), potassium, stron-
tium (swine and poultry), and zinc (poultry).
The recommended MTL in this report do not include a
built-in safety factor. Consequently, the recommended val-
ues should be adjusted according to their intended use, and
each chapter contains relevant information on modifying fac-
tors for each mineral. Animals that are very young, old, re-
producing, sick, exposed to stressful environments, or con-
suming nutritionally imbalanced diets may be especially
sensitive to toxicoses, and each chapter provides additional
information on the impact of these factors. In practice, the
MTL is highly dependent upon the form of the mineral to
which the animal is exposed. Important chemical factors that
determine the bioavailability of the mineral sources include
the solubility of a mineral compound in the digestive tract,
its valence state, and whether the mineral is in an organic.
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MINERAL TOLERANCE OF ANIMALS
metallic, or other inorganic form. For some minerals, such
as silica, chromium, iron, tin, lead, aluminum, and barium,
the MTL may vary by several orders of magnitude depend-
ing upon the chemical form of the mineral. The individual
chapters provide further information on the bioavailabilities
of common sources of minerals. Each chapter contains a
table that summarizes the details on the levels, chemical
form, duration, animal ages, and signs of toxicosis used in
the studies reviewed to establish the recommendations. In
some cases, there is a wide interval between the MTL and
the levels that are toxic because research is insufficient to
make finer discrimination. The summary tables provided in
each chapter give insight into the level of uncertainty.
While all minerals can become toxic when exposure lev-
els are sufficiently high, the frequency that animals are ex-
posed to excessively high levels differs greatly for each min-
eral. As shown in Table S-1, the committee identified
• Some minerals where toxicosis is not normally of con-
cern because levels in feed and water are unlikely to be ex-
cessive: aluminum, antimony, barium, bismuth, chromium,
cobalt, germanium, iodone, lithium, magnesium, manganese,
nickel, rare earth elements, rubidium, silicon, silver, stron-
tium, tin, titanium, tungsten, and uranium;
• Eight minerals as being of occasional concern for ani-
mal toxicosis: arsenic, boron, bromine, calcium, iron, potas-
sium, phosphorus, and zinc;
• Sodium chloride and nine minerals as being of frequent
concern for animal toxicosis: cadmium, copper, fluorine,
lead, mercury, molybdenum (ruminants), selenium, sulfur
(ruminants), and vanadium (poultry).
ENVIRONMENTAL HEALTH
Although this report focuses predominantly on levels of
minerals that are toxic for animals, there are some cases
where environmental factors may be the primary consider-
ations that limit the acceptable levels of minerals in the feed
and water of animals. The concentration of some minerals in
excreta is greater than that in the feed consumed, and this
relationship is magnified by high dietary levels. In some situ-
ations, application of animal wastes to the land as fertilizer
can reduce crop yields, result in high residue levels in crops,
or cause environmental or human health concerns.
The committee identified 10 minerals that could be of
concern because of their potential effects on crop yields or
the environment: cadmium, copper, iron, mercury, phospho-
rus, potassium, sodium, selenium, sulfur, and zinc. Of these,
phosphorus is often the primary concern.
Depending upon manure management, location of dis-
posal, and climate factors, environmental considerations may
limit the levels of these minerals that can appropriately be
fed to animals. In some regions, environmental issues should
be considered along with levels that are tolerated by animals
in regulation of the concentrations of these minerals in the
feed and water of animals. However, the maximum tolerable
levels recommended in this report are based solely on indi-
ces of animal health and productivity.
HUMAN HEALTH
Meat, milk, and eggs are an important part of the human
diet, in part, because they supply highly bioavailable fonns
of minerals. Often animals can serve as an important buffer
for the high mineral concentrations found in some plants or
supplements, thereby reducing human exposure to poten-
tially toxic minerals. However, levels of some minerals may
accumulate in animal tissues intended for human consump-
tion to concentrations that might adversely affect human
health, even when animals are exposed to safe levels (i.e.,
levels at or below their respective MTL). Consequently, ac-
ceptable concentrations of minerals in feeds and water of
animals raised for food must consider the health of the hu-
man consumer as well as the health of the animal itself.
The committee identified minerals of concern for human
health by a three-step process. First, the amount of a mineral
that accumulates in meat, milk, bone, and eggs in animals
fed their MTL was estimated. Second, acceptable safety stan-
dards for mineral intake by humans were identified. Third,
the maximum concentrations in animal tissues were com-
pared to levels known to be safe for humans. Individual chap-
ters in this report provide information on the dose-response
relationship between feed mineral levels and tissue levels.
The committee relied on recent recommendations by the
Food and Nutrition Board of the National Academies and
other national or international organizations. Recent data on
food consumption trends in the United States were used to
estimate daily intake of animal meat, milk, and eggs. It was
assumed that all of the protein-rich foods consumed by an
individual came from animals consuming minerals at their
MTL. Using this process, the committee identified minerals
for which levels that are tolerated by animals could result in
unacceptably high mineral concentrations in tissues used for
human foods.
• Cadmium, lead, mercury, and selenium could accumu-
late to excessive levels in skeletal muscle. If it is assumed
that 5 percent of meat was bone fragments (due to inappro-
priate processing), barium, and fluorine might also be exces-
sive in some cases.
• Cadmium, iodine, lead, and mercury might, in some
cases, become excessive in milk.
• Arsenic, cadmium, copper, lead, mercury, selenium,
and possibly iron could become excessive in liver.
• Arsenic, bisrnuth, cadmium, chromium, cobalt, fluo-
ride, lead, mercury, and selenium could become excessive in
kidney.
Establishing specific recommendations for mineral lev-
els in animal feeds that are safe for human health was be-
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SUMMARY
yond the charge of the committee. However, for arsenic,
barium, bismuth, cadmium, chromium, cobalt, copper, fluo-
ride, iron, lead, mercury, and selenium, the MTL in this
report, while safe for animals, could result in unacceptably
high levels of the mineral in some types of foods derived
from these animals.
REMAINING QUESTIONS AND RESEARCH NEEDED
Finally, the committee was charged with identifying gaps
in knowledge that would benefit from further research. The
individual chapters fairly consistently highlight three main
areas across the minerals considered:
• The bioavailability of minerals that animals commonly
encounter in feedstuffs is not well characterized, especially
when fed at concentrations near the MTL. Identifying the
bioavailability of minerals in the form that animals would
likely be exposed to and at moderately toxic levels is needed
for nutritionists and veterinarians to use the MTL recom-
mendations in this report. The MTL are often based on
reagent-grade, highly available forms. Research on the
bioavailability of minerals at dietary levels near the MTL
would also permit refinement of the recommended MTL.
• The relationship between mineral concentrations in
feed and water and the levels in meat, milk, and eggs is not
well characterized for most minerals, particularly at levels
that are near the MTL of the animal. For most minerals, the
available information was determined during relatively
short-term studies using unrealistically high levels of expo-
sure. Information on mineral accumulation in tissues follow-
ing lifetime exposure to minerals is needed to evaluate tissue
residue levels and impacts on human health.
• Relevant information for predicting the MTL of miner-
als for aquatic and companion animals is relatively incom-
plete. Mineral absorption and excretion in aquatic animals is
often considerably different from that in terrestrial animals.
Studies designed specifically to determine the MTL in
aquatic species are needed. Companion animals have long
life spans and there are few studies on chronic mineral toxi-
coses in these species.
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MINERAL TOLERANCE OF ANIMALS
TABLE S-1 Summary of Minerals Reviewed in Ttiis Report
Element
Required
Nutrient"
Concern for
Animal Health
MTL Relative to 1980
Recommendations*
Aluminum ^^^^h
^^^ No Jl^^^^
^^H Low ^^^^^^^^H
^^H Increased (nonruminants) ^
^
Antimony
No
Low
New
Arsenic ^^^^|
^^^^P Possibly
Medium
Decreased''
Barium
No
Low
Increased''
Bismuth
No
Low
Increased^
J
Boron
Possibly
Medium
Similar
Cadmium
No
^^^^B Medium ^^^^^^H
High
Increased''
^^^^^^^B
^^H Yes ^^^1
1 Medium
Decreased (ruminants)"^
^^ft Increased (poultry)^ ^^H
^
Chromium
Yes
Low
Decreased''
Cobalt '^^^
^^^ Yes ^^^1
P Low
Increased^
Copper
Yes
High
Decreased'
Fluorine
Yes
Hiah
Increased (cattle')'
^J
Germanium
No
Low
New
^^^^^^^M
^^^ Low
Similar
^^
Iron
Yes
Medium
Decreased (cattle and poultry)'
^^^^^M
^^H ^^^H
^B
Increased (ruminants)''
Decreased (nonruminants)"^
t
Lithium
No
Low
New
Magnesium
Yes
Low
Increased'
Manganese
Yes
Low
Increased (ruminants, swine)"^
Mercury ^^^^^^^B
^^0 ^^B
^F High
Decreased'^
Molybdenum
Yes
High-'
Decreased (ruminants)"^
Increased (swine)'"
Nicliel
Possibly
Low
Increased (ruminants, swine)'
Phosphorus
Yes
Medium
Decreased (cattle, swine)'^
^^^^^^^H
^^^^^Yes ^^^B
^^^ Medium ^^^^^^
^^^ Decreased'
\
Rare earths
Possibly
Low
New
Rubidium
Possibly
Low
New ^^^^^H
^^
Selenium
Yes
High
Increased'
Silicon
Possibly
Low
^^^^^H
I
Silver
No
Low
Similar
Sodium Chloride ^^^^^
^^^ Yes ^^^
■■ High
Decreased' ^^^
^^
Strontium
No
Low
Decreased (swine, poultry)"^
Sulfur
Yes
High''
Similar
Tin
No
Low
New
Titanium
No
Low
New
Tungsten
No
Low
Similar
^^^^^^^H
^^^ Low ^^^^^^^^1
^^^ New ^^^^^^^^^^^H
^1
Vanadium
Probably
High^
Similar
Zinc
Yes
Medium
Decreased (poultry)'
''Possibly: Indicates that circumstantial data indicate the possibility that the mineral is essential but mechanistic information is lacliing. See specific chapters
for supportive information.
''Similar: Recommended Maximum Tolerable Levels for poultry and livestocl^ in this report are not appreciably different than in the 1980 report; Decreased:
Recommendations in this report are lower than the previous recommendations; Increased: Recommendations in this report are higher than the previous
recommendations: New: Mineral was not reviewed in 1980 or no recommendation was provided.
'MTL changed due to new information.
''MTL changed because the 1980 report was based on human health concerns and not on toxicity to animals.
■"Ruminants.
Poultry.
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1
Introduction
Inorganic elements found in the Eartli's crust are often re-
ferred to as minerals. The essential minerals are those that
have well-defined biochemical roles and must be in the diet of
vertebrates for optimum health and productivity. There are
more than a dozen essential minerals and, for each, the amount
needed for optimal health and productivity is referred to as the
dietary requirement. Close to a dozen other minerals are sus-
pected to be essential because they increase weight gain or
efficiency of feed use but definitive biochemical or physiologi-
cal roles have yet to be determined. Dozens of other minerals
naturally occur at trace levels in foods and tissues of animals
but are not typically suspected to play a useful nutritional pur-
pose and are considered incidental contaminants. However,
all minerals, whether essential or nonessential, can adversely
affect an animal when amounts in the diet and water become
excessive (Figure 1-1); so the prevention of mineral toxicoses
is a fundamental part of animal nutrition and management.
The concentration at which a specific mineral becomes toxic
varies greatly. The most highly toxic minerals, such as mer-
cury, can cause impairments in health and productivity of ani-
mals when present in the diet at concentrations of less than a
few milligrams per kilogram, whereas such low levels would
be well below the dietary requirement of most essential min-
erals. It is generally thought that those minerals that were en-
riched in the aquatic environment of early evolution became
essential and are tolerated at much higher levels than those
that are nonessential and were historically present at very low
concentrations.
EXPOSURE
Animals may be exposed to toxic levels of minerals from a
wide variety of sources. Feedstuffs derived from plants are a
common source of minerals. Levels of minerals in plant tis-
sues vary greatly due to the natural variation in soil minerals.
Molybdenum and selenium may naturally occur in soils of
some regions at levels sufficient to cause certain plants to ac-
cumulate levels that can be toxic for animals. High soil and
consequently plant concentrations of cadmium, lead, copper,
and zinc can occur from the application of municipal wastes
and other biosolids to the land. Mining, smelting, and other
industries are often associated with local areas of mineral con-
tamination to the water, soil, and air, and ultimately the plants
that grow in the area. Plants can accumulate toxic levels of
minerals by deposition into their tissues or as the result of
surface contamination with soil or dust. Some aquatic plants
accumulate iodine from seawaterto toxic levels. Feedstuffs of
animal origin may also be sources of toxic levels of minerals.
For example, some types of fish meal may be high in mercury
because it bioconcentrates through the aquatic food chain.
Mineral supplements are commonly added to animal diets to
correct deficiencies found in pastures, forages, and feed ingre-
dients. Some sources of mineral supplements may contain
potentially toxic levels of contaminating minerals, depending
upon the source of the supplement and the method of its pro-
cessing. For example, some rock phosphate deposits may be
naturally high in fluoride or vanadium and cause toxicosis
when supplemented in animal diets to meet their phosphorus
requirement. Toxic levels of minerals may accidentally occur
due to mistakes in feed formulation and manufacturing, or
from contamination during storage or transportation. Such
accidental administration can potentially result in very high
mineral levels and cause acute toxicosis and death, whereas
most other modes of introduction typically cause toxicosis
only after chronic exposure. Surface water and occasionally
even deep-well or domestic water supplies may contain ex-
cessive levels of some minerals due to naturally high levels in
the ground. Sulfur, sodium, iron, magnesium, selenium, and
fluoride are among the minerals most likely to reach toxic
levels in natural water supplies. Minerals may also be intro-
duced into water supplies from industrial wastes, pesticide
contamination, and other sources of pollution. Finally, miner-
als such as copper, zinc, bromine, bismuth, and some of the
rare earths are sometimes added to feeds or water as therapeu-
tics or growth promoters and their potential for toxicity is
accentuated.
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MINERAL TOLERANCE OF ANIMALS
Dietary Essential Minerals
Optimal
health
Death
Dietary IVIaximum
Requirement Tolerable Level
4-
■^
c
Optimal!
^ \
/ —
/ o
Level i
to
=3'
X \
o" \
Dietary concentration
High
Optimal
health
Death
Maximum
Tolerable Level
Nonessential Minerals
Dietary concentration
High
FIGURE 1-1 Mineral concentrations and animal health. The relationship between dietary mineral concentrations and animal health is very
different for essential versus nonessential minerals. For essential minerals (top graph), increasing amounts of a mineral in the diet are highly
beneficial up to a point (requirement), beyond which additional amounts have little additional value. At some point (maximum tolerable level),
higher dietary concentrations become detrimental to the animal's health. In the case of nonessential minerals (bottom graph), low levels are
tolerated without detrimental effects on the health of the animal. At some point, higher concentrations become detrimental to the animal.
Mineral exposure is commonly reported in several differ-
ent ways. Expressing exposure as an amount per day (e.g.,
mg mineral consumed/day or mg/kg BW/day) is very pre-
cise and especially useful when intake is variable, such as
the case when the mineral is delivered in water or in a free-
choice supplement. Expressing exposure as a proportion of
the feed or water (e.g., percent or mg/kg of feed) has many
obvious practical advantages in feed formulation and gov-
ernment regulation. These two methods of expression can be
interconverted when the rate of consumption is known. To
the extent possible, tables in this report express exposure as
the concentration in feed or water. Feeds that contain for-
ages or fresh feedstuffs have extremely variable moisture
contents, so their mineral contents are best expressed on a
dry matter (DM) basis whenever possible.
TOXICITY
The adverse effects of minerals are dependent on the in-
tensity of exposure, and they range from subtle effects on
homeostatic processes, to impairments in animal growth or
reproductive rates, to specific pathologies and death. An
understanding of the biochemical or physiological mecha-
nism by which a mineral exerts its detrimental effect is use-
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INTRODUCTION
ful in diagnosing toxicosis problems and in designing re-
searcii to identify the level at which that mineral becomes
toxic. For example, some minerals owe their toxicities to
displacing a nutritionally essential mineral from its normal
biochemical and physiological role. This is illustrated by
bromine, which has physical characteristics that are very
similar to those of chlorine, and which displaces chlorine
from its important functions as an electrolyte. Other ex-
amples of this phenomenon include the displacement of cop-
per by molybdenum, the displacement of sulfur by selenium,
and the ability of lead to displace zinc and calcium. Toxicity
experiments designed to exploit these relationships are most
infonnative.
The toxicity threshold of each mineral is dependent on its
chemical form, enteric absorption, metabolism, duration of
consumption by the animal, levels of other minerals in the
diet or water, and the species and physiological state of the
animal. Important chemical factors that determine the
bioavailability of the mineral sources include the solubility
of a mineral compound in the digestive tract, its valence state,
and whether the mineral is in an organic, metallic, or other
inorganic form. Although extensive research has described
the bioavailability of minerals in feedstuffs and supplements
when fed at concentrations below the dietary requirement,
much less research has been directed toward distinguishing
the bioavailability of different mineral sources at toxic di-
etary concentrations.
Characteristics of different animal species that are impor-
tant modifiers of toxicosis include the efficiency of homeo-
static mechanisms such as absorption or excretion pathways,
presence of a rumen containing microflora that modify the
chemical form of the mineral, and the rate of feed or water
consumption. For example, fish use their gills to both absorb
and excrete minerals and often have very different toxicosis
profiles than terrestrial animals. Among domestic animals,
certain ruminants are sometimes more tolerant of high levels
of dietary minerals than nonruminants. This has been attrib-
uted to their ruminal microflora as well as their relatively
low rate of feed intake.
Individuals are often most sensitive to toxicity during
embryonic development, growth, and periods of stress such
as infections or trauma. Some minerals, such as mercury and
lead, affect development of complex biological systems of
the brain and the immune system. Development of these or-
gans occurs in the late embryonic and early neonatal period,
which is when toxicoses of these minerals are often most
evident. Tolerance to minerals usually increases with age.
and healthy, mature animals are often most resistant to min-
eral toxicoses because they have passed important develop-
mental events, their homeostatic mechanisms are well de-
veloped, and their relative rates of feed intakes are low.
However, some minerals are not easily excreted and they
accumulate during an animal's lifetime, resulting in toxic
levels in older animals. Cadmium and mercury are two such
minerals, and their accumulation in tissues over time has
important implications for the safety of foods derived from
animals that have consumed high levels of these minerals.
ENVIRONMENTAL AND HUMAN HEALTH
Although this report focuses predominantly on levels of
minerals that are toxic for animals, there are some cases
where environmental factors or the wholesomeness of foods
for human consumption derived from animals are the pri-
mary considerations that limit the acceptable levels of min-
erals in the feed and water of animals. High levels of copper,
zinc, phosphorus, and heavy metals in animal excreta can
cause environmental damage. Depending upon manure man-
agement, location of disposal, and climate factors, environ-
mental considerations may limit the levels of these minerals
that can appropriately be fed to animals. The text of this
report provides additional information on environmental is-
sues and key references to allow a detailed assessment of
these concerns. However, the maximum tolerable levels rec-
ommended in this report are based solely on indexes of ani-
mal health and productivity.
Even at dietary levels that are apparently safe for animals,
some minerals accumulate in their tissues to concentrations
that are unsafe for human consumption. Liver, kidney, and
spleen are the tissues of maximal accumulation of cadmium,
lead, and mercury and limit the dietary concentrations that
can be safely fed to animals destined for human consump-
tion. Organic forms of selenium and mercury accumulate in
all tissues, including muscle. Health issues related to high
levels of these minerals in human foods have been consid-
ered in detail by many national and international commit-
tees, and their recommendations are referenced in this re-
port. Levels of cadmium, lead, and mercury in the feeds
consumed by animals are normally regulated based on con-
cerns related to human health. The recommendations for
maximum tolerable levels of these minerals in this report are
based solely on indexes of animal health and productivity
and would likely result in food products that exceed recom-
mendations for humans.
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Maximum Tolerable Levels
The "maximum tolerable level" (MTL) of a mineral is
defined as the dietary level that, when fed for a defined period
of time, will not impair animal health and performance. Toler-
able mineral levels are typically distinguished from toxic lev-
els by experiments that add incremental amounts of a mineral
to the diet or the water and measure the impact on perfor-
mance and pathological signs of toxicosis. The duration of
exposure to the test mineral markedly influences the level that
causes toxicosis. Long-term and multigenerational studies are
usually most informative, but, in practice, short-term studies
are most commonly conducted. The committee considered
three exposure durations: a single dose, acute exposure, and
chronic exposure. A single dose is defined as exposure due to
the consumption of a single meal or by a single gavage of the
mineral. Acute exposure is defined as an intake of 10 days or
less. Chronic exposure is set as an exposure of 10 days or
more. However, in making recommendations, emphasis was
given to the studies that had the longest durations of exposure.
A "toxic level" is defined as the minimal level that, when fed
for a defined period, impairs animal health or performance
(rate of production of milk, meat, or eggs; growth rate; repro-
ductive capacity; disease resistance). Table 2-1 summarizes
the committee's recommendations for MTL of dietary miner-
als for domestic animals following chronic consumption. Prior
to applying these recommendations, the accompanying text
should be consulted for exceptions and for additional infor-
mation on the ages of animals, their physiological state, and
the length of the studies used to establish these values. Each
chapter also provides information on the MTL following
single and acute exposures to minerals as well as exposure
through water. Information on the toxicity of minerals to dogs
and cats is generally lacking. In cases where information is
available, it is often a single study using only a single toxic
level. Providing a summary of the MTL for dogs and cats in
Table 2-1 without accompanying text would be misleading.
Individual chapters should be consulted for specific informa-
tion on mineral toxicities to dogs and cats, as well as addi-
tional species.
The MTL in Table 2-1 and in each individual chapter do
not include built-in safety factors because the magnitude of
the safety factor varies with each specific situation. Conse-
quently, the recommended values should be adjusted accord-
ing to their intended use, and each chapter contains relevant
information on modifying factors for each mineral. Animals
that are very young, old, reproducing, sick, exposed to stress-
ful environments, or consuming nutritionally imbalanced di-
ets may be especially sensitive to toxicoses, and individual
chapters provide additional information on the impact of these
factors. In practice, the MTL is highly dependent upon the
form of the mineral to which the animal is exposed. For some
minerals, such as silica, chromium, iron, tin, lead, and barium,
the MTL may vary by more than an order of magnitude de-
pending upon the chemical form of the mineral, and the indi-
vidual chapters provide further information on the relative tox-
icities (i.e., bioavailabilities) of common sources of minerals.
Each chapter contains a table that summarizes the details on
the levels, chemical form, duration, animal ages, and signs of
toxicosis used in the studies reviewed to establish the recom-
mendations. In some cases, there is a wide interval between
the MTL and levels that are toxic because research is insuffi-
cient to make finer discrimination. Inspection of the summary
tables presented in each chapter provides insight into critical
experiments and the level of uncertainty.
Research on mineral toxicoses in domestic animals con-
ducted during the past 25 years has resulted in adjustments
to many of the MTL provided in the NRC report Mineral
Tolerance of Domestic Animals, which was published in
1980. Also, an appreciation for the limitations and pitfalls
inherent in mineral analysis has changed interpretation of
some older studies. In some cases (e.g., aluminum, boron,
mercury, and vanadium), the dietary concentrations of min-
erals reported in older literature are suspect because of inad-
equacies in sample preparation or analytical procedures; thus
greater reliance is placed on more recent publications. For
some minerals, the previous report necessarily relied on in
vitro experiments or studies in which animals were injected
10
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MAXIMUM TOLERABLE LEVELS
11
with minerals, bypassing homeostatic digestive processes.
Newer information from feeding studies iias eliminated reli-
ance on injection studies and often resulted in marked
changes in recommendations.
HUMAN HEALTH
Meat, milk, and eggs are an important part of the human
diet because they supply highly bioavailable forms of miner-
als. Animals, via homeostatic control of gastrointestinal ab-
sorption, can often serve to diminish the high mineral con-
centrations found in some plants or supplements, thereby
reducing human exposure to potentially toxic minerals.
However, levels of some minerals may accumulate in ani-
mal tissues intended for human consumption to concentra-
tions that might adversely affect human health even when
animals are exposed to safe levels (i.e., levels at or below
their respective MTL). Consequently, in the case of animals
raised to supply human food, acceptable concentrations of
minerals in feeds and water must consider the health of those
consuming food products derived from these animals as well
as the health of the animal itself.
The committee identified minerals of concern for human
health by a three-step process. First, the amount of a mineral
that accumulates in meat, milk, bone, and eggs when ani-
mals are fed their respective MTL was estimated. Second,
acceptable safety standards for mineral intake by humans
were identified. Third, the maximum concentrations in ani-
mal tissues were compared to levels known to be safe for
humans. Individual chapters in this report provide informa-
tion on the dose-response relationship between feed mineral
levels and tissue levels. Recently the NRC (2000; 2001a,b)
has extensively reviewed the scientific literature on mineral
toxicosis in humans due to the ingestion of high levels of
minerals in foods. The human toxicological standards based
on these reviews and recent data on food consumption trends
in the United States were used to estimate the potential for
mineral toxicosis among humans consuming tissues and flu-
ids from animals exposed to mineral levels at their respec-
tive MTL based on animal health.
Toxicological Standards for Minerals in Humans
The NRC (2000; 2001a,b) set Tolerable Upper Intake
Levels (UL) for minerals that are nutritionally required for
humans (Table 2-2). The UL was defined as "the highest
average daily nutrient intake that is likely to pose no risk of
adverse effects to almost all (human) individuals in the gen-
eral population." The UL were based on lowest-observed-
adverse-effect levels (LOAEL) and no-observed-adverse-
effect levels (NOAEL) that were calculated using primarily
data from studies with humans.
In several cases, the NRC could not identify studies in
humans or sometimes even laboratory animals in which the
mineral as it occurred naturally in the diet was toxic. Thus,
the NRC did not set UL for several minerals (i.e., arsenic,
chromium, silicon), explicitly stated that the ULs applied
only to supplemental (not dietary) forms of two minerals
(i.e., magnesium, nickel), and based UL on data from only
laboratory animal studies for other minerals (i.e., boron,
molybdenum, nickel, vanadium). Furthermore, the NRC
noted in the text that the UL for iron and zinc were based on
studies with humans in which the primary source of the min-
eral was from supplements.
These decisions by the NRC (2000; 200Ia,b) reflect a
number of factors. One is that the form of minerals in food is
sometimes different from that in supplements (e.g., heme-
iron from meat versus supplemental inorganic iron). Another
is that the total milieu of factors (especially protein, phytate,
fiber, and other minerals) in foods can reduce the potential
of toxicosis of high levels of dietary minerals in those foods.
For example, there are no reports of adverse effects from
consuming high levels of calcium and phosphorus in milk or
manganese from cereal products.
The NRC did not set unacceptable levels of several other
minerals (aluminum, barium, bismuth, bromine, cobalt, and
tin). Generally, diet is a minor source of these elements as
compared to pharmaceuticals. The Food and Agriculture
Organization/World Health Organization (FAO/WHO)
Pesticide committees (1967) set the acceptable daily intake
of 1 mg bromide/kg BW/day. Minimal effects (i.e., reduc-
tions in the absorption of essential minerals) were the major
signs when human diets were supplemented with aluminum
salts (125 mg Al/day; Greger and Baier, 1983) or tin salts
(50 mg Sn/day; Johnson et al., 1982). Cadmium, mercury,
and lead are generally considered the elements most apt to
produce toxic effects when ingested. The minimum risk level
for mercury, which is the dose that can be ingested daily for
a lifetime without a significant risk of adverse effects, was
set at 0.0003 mg Hg/kg BW/day for a 70-kg person, based
on neuro-developmental outcomes in children exposed in
utero to methylmercury from maternal fish ingestion (ATSDR,
1999). For pregnant women the suggestion is not to con-
sume fish containing greater than 0.25 mg Hg/kg fresh
weight. Research has demonstrated that blood lead levels
>10 |Jg/dL whole blood were associated with adverse neuro-
logical and hematological effects in children and that blood
lead levels of two-year olds declined when dietary intake of
lead was reduced from 0.053 to 0.013 mg of lead per child
daily (NRC, 1993). The individual mineral chapters in this
report contain additional information on toxic levels of
specific minerals in human diets.
Maximum Exposure to Minerals from Consumption of
Animal Products
Americans consumed an average of 105.7 kg of meat,
fish, and poultry; 228.6 kg of milk and milk-derived prod-
ucts (on a calcium equivalent weight basis, which converts
cheese and other products into an equivalent amount of
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12
MINERAL TOLERANCE OF ANIMALS
milk); 14 kg of eggs; and 9.3 kg of legumes, nuts, and soy
(high-protein alternative to meat) per year during 1990-1999
(Gerrior and Bente, 2002). These data are based on USDA
figures on the disappearance of food available for human
consumption. Accordingly, the average American poten-
tially consumes 0.95 kg, fresh weight, of animal products
per day or 0.98 kg of "protein-rich" foods per day. The ac-
tual average consumption is likely to be considerably less
than 0.98 kg because this estimate is based on disappearance
values and not actual intakes. However, for the purposes of
identifying minerals that might be of concern for human
health, consumption data provide a reasonable margin of
safety. A more extensive risk analysis should be conducted
for those minerals that are identified below as being of con-
cern for human health.
The committee used this information to establish relative
risks. The first question asked was this: How much of a min-
eral would an individual ingest if the individual consumed
that entire kilogram of "protein-rich" food daily as the
muscles from an animal fed at the MTL for that mineral?
Based on the highest concentrations of minerals found in
muscles of livestock and fish fed at the respective MTL (see
individual mineral chapters for data on tissue levels), we
would not expect humans ingesting these muscles to con-
sume excessive amounts of minerals, except for cadmium,
lead, mercury, and selenium. If it is assumed that 5 percent
of the kilogram of "protein-rich" food were bone fragments
(due to incorrect processing), intake of barium and fluoride
might be excessive in some cases.
If the kilogram of "protein-rich" food consumed daily was
milk, intake of cadmium, iodine, lead, and mercury might in
some cases be excessive. The calculated exposures become
of greater concern if the kilogram of "protein-rich" food con-
sumed daily is from the livers or kidneys of livestock and
fish fed toxic levels of minerals. Potentially, humans ingest-
ing 1 kg of liver daily could ingest excessive amounts of
arsenic, cadmium, copper, iron (see below), lead, mercury,
and selenium. Potentially, humans ingesting 1 kg of kidney
daily could ingest excessive amounts of arsenic, bismuth,
cadmium, chromium, cobalt, fluoride, lead, mercury, and
selenium. Generally, the organic forms of arsenic and iron in
tissues are assumed to be relatively less toxic.
These calculations underscore the concerns of the FDA
about certain elements in animal products, namely iodine in
milk (Hemken, 1980), mercury in fish, cadmium in kidneys,
and lead and fluoride in bone. Establishing specific recom-
mendations for mineral levels in animal feeds that are safe
for human health was beyond the charge of the committee.
However, for arsenic, barium, bismuth, cadmium, chro-
mium, cobalt, copper, fluoride, iron, lead, mercury, and se-
lenium, the MTL in Table 2-1, while safe for animals, could
result in unacceptably high levels of the mineral in some
types of foods derived from these animals
REFERENCES
ATSDR (Agency for Toxic Substances and Disease Registry). 1999. Toxi-
cological profile for mercury. Atlanta, GA: U.S. Department of Health
and Human Services.
ATSDR (Agency for Toxic Substances and Disease Registry). 2000. Toxi-
cological profile for arsenic. Atlanta, GA: U.S. Department of Health
and Human Services.
FAOAVHO Pesticide Committees. 1967. Evaluation of some pesticide resi-
dues in food. Rome. Information about meeting available at http://
www.fao.org/docrepAV5897E/w5897e6a.htm
Gerrior, S., and L. Bente. 2002. Nutrient content of the U.S. food supply,
1909-99: a summary report. Home Economic Research Report No. 55.
USDA. Online. Available at http://www.usda.gov/cnpp/Pubs/
Food%20supply/foodsupply09_99.pdf. Accessed November 7, 2004.
Greger, J. L., and M. J. Baier. 1983. Effect of dietary aluminum on mineral
metabolism of aduh males. Am. J. Clin. Nutr. 38:41 1^19.
Hemken, R. W. 1980. Milk and meat iodine content: relation to human
health. J. Am. Vet. Med. Assoc. 176:1119-1121.
Johnson, M. A., M. J. Baier, and J. L. Greger. 1982. Effects of dietary tin on
zinc, copper, iron, manganese, and magnesium metabolism of adult
males. Am. J. Clin. Nutr. 35:1332-1338.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
NRC. 1993. Measuring Lead Exposure in Infants, Children, and Other Sen-
sitive Populations. Washington, D.C.: National Academy Press.
NRC. 2000. Dietary Reference Intakes for Vitamin C, Vitamin E, Sele-
nium, and Carotenoids. Washington, D.C.: National Academy Press.
NRC. 2001a. Dietary Reference Intakes for Calcium, Phosphorus, Magne-
sium, Vitamin D, and Fluoride. Washington, D.C.: National Academy
Press.
NRC. 2001b. Dietary Reference Intakes for Vitamin A, Vitamin K, Ar-
senic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybde-
num, Nickel, Silicon, Vanadium, and Zinc. Washington, D.C.: National
Academy Press.
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MAXIMUM TOLERABLE LEVELS
13
TABLE 2-1 Maximum Tolerable Levels of Minerals in the Feed (mg/kg or % of the DM) of Animals Based on Indexes of
Animal Health"'*
Element
Rodents
Poultry
Swine
Horse
Cattle
Sheep
Fish
Aluminum, mg/kg
200
1,000
(1,000)
(1,000)
1,000
1,000
—
Antimony, mg/kg
70-150
—
—
—
—
—
—
Arsenic, mg/kg"^
30
(30)
(30)
(30)
(30)
(30)
5
Barium, mg/kg"^
250
100
(100)
(100)
—
—
—
Bismuth, mg/kg''
(500)
1,000
500
(500)
—
—
—
Boron, mg/kg
150
(150)
(150)
(150)
150
(150)
—
Bromine, mg/kg
300 ^^
^ 2,500
200
(200)
200
(200)
—
Cadmium, mg/kg''
10
10
10
10
10
10
10
Calcium, %<> ^^M
^H
^H 1.5, growing
H birds; 5,
^^ laying hens
^^H
1 1.5
1.5
0.9
Chromium, mg/kg^
soluble Cr+++
CrO
100
30,000
500
3,000
(100)
(3,000)
(100)
(3,000)
(100)
(3,000)
(100)
(3,000)
3,000
Cobalt, mg/kg^ ^^^^H
■ 25
25
100
(25)
25
25
Copper, mg/kg'^
500
250"^
250
250
40''
15"
100
Fluorine, mg/kg''
150
150
150
(40)
40
60
—
Germanium, mg/kg
30
—
—
—
—
—
—
Iodine, mg/kg'^
—
300
400
5
50
50
—
Iron, mg/kg'"
(500)
500
3,000
(500)
500
500
—
Lead, mg/kg'' ^^^|
^pio
10
10
10
100
100
10
Lithium, mg/kg
(25)
25
25
(25)
25
25
—
Magnesium, %
0.5
0.5, growing
birds; 0.75,
^^^ laying hens
0.24
0.8
0.6
0.6
0.3
Manganese, mg/kg
2,000
2,000
1,000
(400)
2,000
2,000 ^
Mercury, mg/kg"^
inorganic
organic/^
0.2
1
0.2
1
(0.2)
(2)
(0.2)
(1)
2
- ■
2
1
Molybdenum, mg/kg
7
100
(150)
(5)
5
5
10
Nickel, mg/kg
50
250
250
(50)
100
(100)
50
Phosphorus, %''
0.6
1, growing
birds; 0.8,
laying hens
1.0
1
0.7
0.6
1
Potassium, %
1
1
1
1
2
2
- 1
Rare earth mineral, mg/kg
100
—
—
—
—
—
—
Rubidium, mg/kg
200
—
—
—
—
-^^^1
i -
Selenium, mg/kg'^
(5)
3
4
(5)
5
5
(2)
Silicon, %
—
—
—
—
(0.2)
0.2
—
Silver, mg/kg
—
100
(100)
—
—
—
>3
Sodium chloride, %
4
1.7
3
6
4.5, growing
4
—
animals
3.0, lactating
cows
Strontium, mg/kg
1,000
2,000
2,000
(2.000)
2,000
(2.000)
—
Sulfur, %
(0.5)
0.4
0.4
(0.5)
0.30, high-
concentrate
diet; 0.50,
high-forage
diet
0.30, high-
concentrate
diet; 0.50,
high-forage
diet
Tin, mg/kg
100
(100)
(100)
(100)
(100)
(100)
—
Titanium, mg/kg
—
—
—
—
—
—
—
Tungsten, mg/kg
(20)
20
(20)
(20)
(20)
(20)
—
Uranium, mg/kg
100
—
—
—
—
—
< 100
continued
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14
MINERAL TOLERANCE OF ANIMALS
TABLE 2-1 Continued
Element
Rodents
Poultry
Swine
Horse
Cattle
Sheep
Fish
Vanadium, mg/kg
—
25, growing
birds; <5,
laying hens
(10)
(10)
50
50
—
Zinc, mg/kg
(500)
500
1,000S
(500)
500
300
250
"The accompanying text must be consulted for additional details about factors that might increase or decrease the tolerable levels. The levels in parentheses
were derived from interspecies extrapolation. Dashes indicate that data were insufficient to set a maximum tolerable level (MTL). Individual chapters provide
further information on human safety and environmental problems related to feeding high levels of the mineral.
''The MTL are based on highly soluble forms of the mineral and other forms may have lower bioavailabilities. MTL are also based on the assumption that
exposure of the animal to minerals from water and other environmental sources is minimal and that the diet is nutritionally complete, especially in regard to
other minerals that might be antagonized.
''The MTL provided for this nutrient is based on animal health and not human health. Lower levels ai'e necessaiy to avoid excessive accumulation in edible tissues.
'^'The MTL are based on diets with phosphorus levels at, but not above, the animal's requirement. Considerably higher levels can be tolerated if phosphorus
levels are increased sufficiently to maintain an appropriate calcium:phosphorus ratio.
Tor ducks the MTL for copper is 100 mg/kg diet.
fA margin of safety should be added for pregnant animals to assure normal neurodevelopment of the fetus.
^Higher levels of zinc as zinc oxide (2,000 to 3,000 mg/kg diet) are tolerated for several weeks and may provide growth promotion in weanling piglets.
''Assuming normal concentrations of molybdenum (1-2 mg/kg diet) and sulfur (0.15-0.25%). At molybdenum and sulfur concentrations below these, copper
may become toxic at lower levels.
TABLE 2-2 Toxicity Assessments of Nutrients for Humans Based on Food and Nutrition Board Assessments (NRC, 2000;
NRC, 2001a,b)
Lowest (or No)-Observed-
Adverse-Effect Level
(LOAEL/NOAEL)
Tolerable Upper
Intake Level
(UL)
Arseni"
Not set
Not set
I
Boron''
9.6 mg/kg/d
20 mg/d
^^^^^^^H
^^^f 2,500 mg/d
Chromium'^'
Not set
Not set
Copper""
10 mg/d
10 mg/d
Fluorid f
0.10 mg/kg/d
10 mg/d
J
Iron«
70 mg/d (primarily for inorganic
salt supplement)
45 mg/d
Magnesium'' ^^^^H
^^^^^^V 360 mg from non food sources/d ^^^M
^^^^V 350 mg/d from supplement
1
Manganese""
1 1 mg/d
1 1 mg/d
Molybdenum'' ^^^^^^^^
^^^^^B 2.0 mg/d
Nickel''
5 mg/kg/d
1.0 mg/d of soluble nickel salts
Phosphorus' ^^^^^H
^^^^1 g/d ^^^^^^^^B
^^^ g/d
Selenium''
800 ng/d
400 ng/d
Silicoiy
Not set
Not set
Vanadium*
7.7 mg/kg/d
1.8 mg/d
^^^^^^^H
^^^^^^^^^V 60 mg/d (primarily for inorganic ^^^^^^H
^^^^^V 40 mg/d ^^^^^^^H
1
"Chronic intake of 10 |jg/kg/d of inorganic arsenic produces arsenicism with skin changes in humans (ATSDR, 2000).
''NOAEL based on data in rodents or humans (selenium); UL for >19 years of age.
"LOAEL for adults: UL for 19-70 years of age.
''Insufficient data to establish a UL for soluble chromium III salts. Concern only for Cr in supplements.
""NOAEL for adults: UL for >19 years of age.
tOAEL for children through 8 years: UL for >8 years of age.
SLOAEL for adults: UL >19 years of age.
''LOAEL for adults: UL >8 years of age.
'NOAEL for adults: UL for 19-70 years of age.
JNo evidence that Si naturally occurring in food or water produced adverse health effects.
*LOAEL based on data in rats: UL for >19 years of age.
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Aluminum
INTRODUCTION
Aluminum (Al) has an atomic number of 13 and is one of
the lightest metals. It has two oxidation states: Al (0) and Al
(+3). However, aluminum does not occur naturally in the el-
emental state, but rather in combination with oxygen, silicon,
and fluorine primarily. The most important raw material for
the production of aluminum metal is bauxite, which contains
40 to 60 percent alumina (aluminum oxide) (ATSDR, 1999).
Aluminum is the third most abundant element in the
Earth's crust after oxygen and silicon. Although it has been
produced in commercial quantities for just over 100 years, it
is used more today than any other metal, except iron. In 2000,
the United States' estimated consumption of aluminum was
7.5 million metric tons (Plunkert, 2002). Aluminum recov-
ered from discarded aluminum products accounts for about
20 percent of estimated consumption of aluminum in the
United States (Plunkert, 2002).
Aluminum is used industrially because it is malleable,
ductile, durable, and easily machined and cast, and has ex-
cellent corrosion resistance. The following areas constitute
the major uses of aluminum in the United States: transporta-
tion, 35 percent; packaging, 25 percent; building, 15 per-
cent; consumer durables, 8 percent; electrical, 7 percent; and
other, 10 percent (Plunkert, 2002).
ESSENTIALITY
Horecker et al. (1939) suggested that aluminum promoted
the reaction between cytochrome C and succinic dehydroge-
nase in vitro. The activation of purified guanine nucleotide
binding protein, the regulatory component of adenylate cy-
clase, by fluoride was shown to require the presence of Al"^-'
in vitro (Sternweis and Oilman, 1982; Kahn, 1991). The sig-
nificance of these observations in vivo is not known. No
conclusive evidence exists to suggest that aluminum is es-
sential for growth, reproduction, or survival of animals
(Alfrey, 1986;Ganrot, 1986;Greger, 1993). However, it may
be a cariostatic agent by itself and in combination with fluo-
ride (Kleber and Putt, 1984).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Monitoring the tissue levels of aluminum and the absorp-
tion and excretion of aluminum is very difficult for a variety
of methodological reasons (Kostyniak, 1983; Ganrot, 1986;
Savory and Wills, 1988; Greger and Sutherland, 1997;
ATSDR, 1999). Estimated amounts of aluminum in plasma
decreased by more than 50-fold between 1950 and 1980 be-
cause of improvements in methodology (Versieck and
Cornells, 1980). Accordingly, this review emphasizes litera-
ture published after 1980.
One reason for the analytical problems is that aluminum
is ubiquitous in the environment and contamination of bio-
logical samples is difficult to prevent. When contamination
from anticoagulants and glassware was prevented, serum
aluminum concentrations were between 1 to 5 |Jg/L
(Kostyniak, 1983; Ganrot, 1986; Savory and Wills, 1988).
A second limitation is that flame atomic absorption spec-
troscopy is not sensitive enough for analyses of biological
samples. Matrix effects decrease the sensitivity of several
methods and hence preparation of samples is often time-con-
suming (ATSDR, 1999). The most commonly used method
is graphite furnace atomic absorption spectrometry. Re-
searchers must correct for interfering interaction with phos-
phorus and silicon when using neutron activation analysis to
determine aluminum because all three produce ^^Al when
activated. A major problem with inductively coupled
plasma-atomic emission spectrometry is that calcium in the
sample raises the limit of detection for aluminum. Two other
techniques have improved sensitivity, but are expensive and
require highly trained personnel. Inductively coupled
plasma-mass spectrometry has sensitivity down to 1 mg/L
of aluminum in blood. Laser ablation microprobe mass
75
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16
MINERAL TOLERANCE OF ANIMALS
analysis (LAMM A) has been used for analyses of aluminum
in brains where sensitivity and location are important.
A third methodological limitation is the lack of useful-
ness of aluminum isotopes for metabolic studies (Greger and
Sutherland, 1997). Most aluminum isotopes have very short
half-lives; ^^A[, ^^Al, ^^A[, ^^Al, and ^OAI have half-lives of
less than 6.6 minutes (Bureau of Radiological Health and
Training Institute, 1970). Thus they cannot be used in vivo
to monitor absorption and excretion processes. The only alu-
minum isotope with a biologically usable half-life is ^^Al
(7.2 X 10^ years), but it is very scarce and hence the study
designs and replicates are often limited (Jouhanneau et al.,
1993; Priest et al., 1995; Schonholzer et al., 1997; Yokel et
al., 2001). Other investigators attempted to use ^^Ga (a type
Ilia element like aluminum) as a marker for aluminum
(Greger et al., 1994, 1995; Priest et al., 1995). These investi-
gators concluded that "^^Ga was an unacceptable marker for
aluminum because ^^Ga did not distribute in tissues like alu-
minum and was more sensitive to iron intake and status than
was aluminum.
Finally, absorption of aluminum is difficult to quantitate
because absorption is generally <1 percent (Alfrey 1989;
Greger and Sutherland, 1997). In response to this method-
ological quandary, Ganrot (1986) suggested that urinary alu-
minum excretion could be assumed to equal aluminum ab-
sorption. This assumption is faulty because animals
accumulate aluminum in tissue with continued oral expo-
sure to aluminum; this would not occur if absorption and
urinary excretion were equal. Moreover, the relative percent-
age of absorbed aluminum retained (not excreted in urine)
has been found to vary with a variety of factors, including
renal function, age, and disease states (Ecelbarger et al.,
1994a; Greger and Radzanowski, 1995). Thus one alternate
(but time-consuming and difficult) way to estimate relative
aluminum absorption from diet is to compare tissue accumu-
lation of aluminum in relation to the dose in animals fed
aluminum and in animals matched for age and weight that
are injected with aluminum (Greger and Powers, 1992).
Another alternate (but also time-consuming and difficult)
way to estimate absorption from a single large dose is to sum
all aluminum in the carcass, urine, and bile (Sutherland and
Greger, 1998).
equal doses of aluminum were ingested and injected, and
summation of the increase in aluminum excretion and tissue
retention after a dose), aluminum absorption has been esti-
mated to be 0.01 to 0.8 percent of intake when aluminum
was ingested in diet (Ganrot, 1986; Greger and Powers,
1992; Jouhanneau et al. 1993) and 0.3 percent from water
(Yokel et al., 2001). However, fasted rats absorbed 2 to 5
percent of the small amounts of aluminum administered by
gavage in a citrate solution (Froment et al., 1989a;
Schonholzer et al., 1997; Sutherland and Greger, 1998).
Aluminum absorption occurs to the greatest extent in the
proximal intestine. Plasma aluminum and labeled plasma
glucose levels peaked simultaneously 45 minutes and 30
minutes after aluminum citrate and glucose were adminis-
tered together by gavage to rats (Froment et al., 1989a,b) and
humans (Nagy and Jobst, 1994), respectively.
The mechanisms of aluminum absorption include both
paracellular passage of aluminum through tight junctions by
passive processes (Provan and Yokel, 1988b; van der Voet,
1992) and transcellular passage through enterocytes, involv-
ing passive, facilitated, and active transport processes (van
der Voet, 1992). The active transcellular processes involved
in aluminum absorption are saturable (Feinroth et al., 1982).
At least some of the active processes (particularly the trans-
port of aluminum into the serosal fluid) are shared with pro-
cesses for active absorption of calcium (Feinroth et al., 1982;
Provan and Yokel, 1988a). Some of these processes are de-
pendent on vitamin D metabolites (Ittel et al., 1988, 1990).
Aluminum did not appear to affect the ability of calbindin-
D9K (the diffusional translocator of calcium across mucosal
cells) to bind calcium in rats (Adler et al., 1991) but reduced
the transcription and/or stability of calbindin-D28K in chicks
(Cox and Dunn, 2001).
Adler and Berlyne (1985) perfused in situ guts with alu-
minum chloride at pH 2 and estimated that 23 percent of
aluminum absorption in rats was due to non-saturable pro-
cesses and the rest was due to active processes. However,
the relative importance of absorptive processes varies with
the concentration and speciation of aluminum in the gut and
other dietary factors (van der Voet, 1992; Greger and
Sutherland, 1997). These factors are discussed in the section
further below on Bioavailability.
REGULATION AND METABOLISM
Absorption
The gastrointestinal tract is the most important body sys-
tem that protects mammals against accumulating aluminum
in tissues. As noted in the previous section on Difficulty in
Methods of Analysis and Evaluation, absorption of alumi-
num is difficult to determine, partially because fecal losses
approximate intakes. Using a variety of alternate method-
ologies (measurement of aluminum in urine, usage of iso-
topes, comparison of tissue aluminum accumulation when
Urinary Excretion
Urinary excretion of aluminum is proportional to alumi-
num intake under controlled conditions (Ganrot, 1986;
Greger and Powers, 1992). Approximately half of the ab-
sorbed aluminum is estimated to be excreted in urine
(Jouhanneau et al., 1993). Thus humans with normal renal
function who consume typical diets with no medications
excrete less than 50 |Jg/day of aluminum in urine (Ganrot,
1986; Alfrey, 1986; Greger, 1993). This primarily reflects
the protective effect of the gut. When patients were infused
with parenteral solutions contaminated with aluminum, sub-
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ALUMINUM
17
jects excreted 0.1 to 3.8 mg/day of aluminum (Klein et al.,
1982).
The importance of renal excretion of aluminum has been
demonstrated many times in humans with reduced renal
function, even in the absence of parenteral exposure to alu-
minum (King et al., 1981; Committee on Nutrition, 1986;
Hewitt et al., 1990; Strong et al., 1996; ATSDR, 1999).
Alfrey et al. (1980) found that patients with undialyzed ure-
mia had 12-fold more aluminum in bone, and more than 6-
fold more aluminum in liver and spleen than renally compe-
tent patients. Rats given unilateral nephrectomies (that
reduced renal excretion only moderately as might occur natu-
rally with age) accumulated more aluminum in bone and
liver than sham-operated rats (Ecelbarger and Greger, 1991;
Ecelbarger et al., 1994a). Some of this increased accumula-
tion of aluminum by uremic animals could reflect increased
gut permeability to aluminum in uremic animals (Ittel et al.,
1988, 1992).
Biliary Excretion
Biliary excretion is less important than urinary excretion
in preventing accumulation of aluminum in tissues. Dogs
and rats given intravenous doses of aluminum excreted from
0.1 to 7 percent of the doses in bile (Kovalchik et al., 1978;
Klein etal., 1988; Xu et al., 1991). In contrast, biliary alumi-
num excretion sometimes exceeded urinary excretion of alu-
minum in humans whose main source of aluminum expo-
sure was diet (Ishihara and Matsushiro, 1986). Although rats
exposed to low (6.9 to 10.3 |Jg/g diet of aluminum) levels of
aluminum in diet excreted more aluminum in bile than in
urine, rats given moderate (0.25 to 1 mmole/kg BW of alu-
minum) amounts of aluminum by gavage excreted more alu-
minum in urine than bile (Sutherland and Greger, 1998). This
reflected that the biliary excretion of aluminum was rapid
(within 15 minutes after a gavage dose in rats) and saturated
by doses as low as 0.2 mmole of aluminum (Sutherland et
al., 1996; Sutherland and Greger, 1998).
SOURCES AND BIOAVAILABILITY
Dietary Sources
Grain and vegetable products contain more aluminum
naturally than animal products (Schlettwein-Gsell and
Mommsen-Straub, 1973; Sorenson et al., 1974; Greger,
1985; Greger et al., 1985b; Pennington and Jones, 1989). A
few plants, such as tea and herbs (e.g., bay, oregano, and
thyme) often "accumulate" more than 500 mg/kg dry weight
of aluminum. The aluminum content of vegetable and grain
products varies with plant varieties and soil conditions, in-
cluding pH (Hopkins and Eisen, 1959; Eden, 1976).
Water is generally not a major source of aluminum. The
amount of aluminum in surface and ground water varies
from <12 mg to 2.25 mg/L of aluminum in the rivers of
North America (Jones and Bennett, 1986). Platen (1995)
estimated that average aluminum concentrations of water
supplies in Europe ranged from 6 to 60 |Jg/L of aluminum.
Miller et al. (1984) estimated that there was a 40-50 per-
cent chance that aluminum containing flocculants added to
clarify municipal water supplies increased the aluminum
concentration of finished water above that naturally present
in water. They reported that the median concentration of
aluminum in "finished" water supplied by water utilities
was 17 |Jg/L of aluminum (range <14 |Jg/L to 2.67 mg/L of
aluminum). However, very high concentrations (30-620
mg/L) of aluminum have been found in "finished" water
when processing plants made serious errors in England
(Eastwood et al., 1990).
The biggest source of aluminum in the diets of most
Americans is food additives, although aluminum-contain-
ing additives are present in only a limited number of foods
(i.e., chemically leavened baked goods and processed
cheese) (NRG, 1984; Greger, 1985; Pennington and Jones,
1989). It is unlikely that aluminum-containing food addi-
tives are intentionally added to the diets of livestock and
pets. However, aluminum contamination of some additives
used in livestock and pet feed is possible. For example,
aluminum concentrations were found to be 3- to 10-fold
higher in soy-based infant formulas than in milk-based in-
fant formulas (Committee on Nutrition, 1986). Calcium and
phosphate additives (with unintentional aluminum con-
tamination) were likely sources of the aluminum in the soy
formulas (Burgoin, 1992).
Packaging and utensils can also be a source of dietary
aluminum to humans. Most foods stored or cooked in alumi-
num pans, trays, or foil accumulated less than 2 mg/kg food
of aluminum when frozen, refrigerated, and stored at ambi-
ent temperature (Ondreicka etal., 1971; Greger etal., 1985b;
Liukkonen-Liija and Piepponen, 1992). A few acidic foods
(e.g., tomato products, applesauce), when cooked for long
periods of time, accumulated as much as 17 mg/100 g serv-
ing of aluminum. However, packaging is probably not an
important source of aluminum in the diets of livestock or
even pets, as aluminum cans are lined to prevent seepage of
aluminum into foods.
Ptiarmaceutical and Otiier Sources
Lione (1983, 1985) estimated that humans could ingest as
much as 5 g/day of aluminum in pharmaceuticals such as
antacids, buffered analgesics, antidiarrheals, and certain an-
tiulcer drugs. Only the antidiarrheals (e.g., kaolin,
attapulgite, and aluminum magnesium silicate) are apt to be
used in veterinary practice.
Aluminum hydroxide, aluminum phosphate, aluminum
potassium sulfate (alum), and aluminum silicates (zeolite)
are used in the preparation of a number of vaccines and other
injectants to adsorb antigenic components and to serve as
adjuvants that enhance immune response (Lione, 1985). The
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MINERAL TOLERANCE OF ANIMALS
importance of adjuvants as a source of aluminum is debat-
able (Malakoff, 2000). Keith et al. (2002) estimated that the
body burden of aluminum for human infants is greater from
vaccinations than from dietary sources, but is still at a safe
level. More aluminum was absorbed into blood by rabbits
injected intramuscularly with aluminum phosphate than with
aluminum hydroxide adjuvant (Hem, 2002). It is unlikely
that injectables are a major source of aluminum exposure to
livestock or even most pets.
Feed or water for livestock could be contaminated with
aluminum when aluminum sulfate and zeolite are applied to
litter and waste lagoons to reduce phosphorus run-off from
lands fertilized with these wastes and to reduce ammonia
volatilization in facilities (Moore et al., 1999, 2000; Codling
et al., 2002). Alum has also been added to dairy slurry to
reduce ammonia emissions (Lefcourt and Mesinger, 2001).
Bioavailability
A variety of dietary factors affect absorption of
aluminum.
Speciation and Solubility
Speciation of aluminum in water is complex and changes
dramatically with pH (Martin, 1991). The net result is that
aluminum is less soluble between pH 5 to 7 than at higher or
lower pHs. Accordingly, rats absorbed more aluminum from
in situ perfusions at pH 4 than at pH 7 (van der Voet, 1992).
The solubility of aluminum compounds also affects their
efficiency of absorption. Patients' serum aluminum levels
tended to be higher after they were dosed with sucralfate in
suspension rather than in tablet or granular form (Conway et
al., 1994; Schiitze et al., 1995). Berthon and Dayde (1992)
noted that aluminum phosphate was less toxic than alumi-
num hydroxide because aluminum phosphate is virtually in-
soluble at acidic pHs. However, Yokel and McNamara
(1988) found no correlation between the percent
bioavailability of aluminum from eight aluminum-contain-
ing compounds to rabbits and the compounds' solubility.
Citric Acid
Citrate in diet and pharmaceuticals has been repeatedly
found to increase aluminum absorption in humans (Slanina
et al., 1986; Greger and Sutherland, 1997). Citrate has been
found to increase aluminum retention in tissues of labora-
tory animals when administered in drinking water (Fulton et
al., 1989; Fulton and Jeffery, 1990), diet (Ecelbarger et al.,
1991, 1994b; Greger and Powers, 1992; Owen et al., 1994),
or gavage solutions (Slanina et al., 1984, 1985; Yokel and
McNamara, 1988; Froment et al., 1989 a,b; Quartley et al.,
1993). Generally animals fed aluminum and citrate in diets
retained more aluminum than animals given citrate with alu-
minum in drinking water, but less aluminum than animals
dosed with only citrate and aluminum by gavage. The pres-
ence of other substances (i.e., fluoride, phosphorus, calcium)
in the gut, as occurs when aluminum and citrate were added
to feed and water, may have moderated the effect of citrate
on aluminum absorption (Greger, 1993; Glynn et al., 1995).
Other Organic Acids and Anions
Although the interaction of citrate and aluminum is prac-
tically important, the uniqueness of the interaction has been
overstated. A variety of organic acids found in food beside
citric acid (including ascorbic, gluconic, lactic, malic, ox-
alic, and tartaric acids) have been found to increase the solu-
bility of aluminum and to increase tissue retention of alumi-
num in rats orally dosed with aluminum (Domingo et al.,
1991, 1994). Limited data indicate that dietary factors (e.g.,
phytate and polyphenols) that reduced the absorption of other
minerals also reduced the absorption of aluminum (Powell
and Thompson, 1993; Powell et al., 1993).
Several investigators have compared the biological ef-
fects of various aluminum salts. Large (aluminum as 0.5 per-
cent of diet) oral doses of aluminum as acetate, chloride,
nitrate, and sulfate salts were more toxic to chicks than simi-
lar doses of aluminum as phosphate salt (Storer and Nelson,
1968). Similarly, human subjects had less aluminum in se-
rum and urine after being dosed with 2.2 g aluminum daily
as aluminum phosphate than after being dosed with alumi-
num hydroxide, aluminum carbonate, or dihydroxyalumi-
num aminoacetate (Kaehny et al., 1977). Rabbits dosed with
aluminum nitrate or citrate experienced greater increases in
serum aluminum than those dosed with aluminum as borate,
hydroxide, chloride, glycinate, sucralfate, and acetate salts
(Yokel and McNamara, 1988). No differences in tissue alu-
minum concentrations were noted when rats were dosed with
moderate levels (205 to 278 mg/kg diet of aluminum) of
various aluminum hydroxide compounds (reagent and
dessicated gel) and aluminum as lactate, palmitate, and phos-
phate (Greger et al., 1985a). However, bone phosphorus lev-
els were only affected by aluminum hydroxide.
Silicates
Dietary silicates may reduce the absorption of aluminum
because silicates replace phosphates as the primary
complexors of aluminum in solutions that are more alkaline
than pH 6.6 (Birchall and Chappell, 1988; Birchall, 1992).
Edwardson et al. (1993) noted that plasma ^^Al concentra-
tions one hour after ingestion of ^®A1 and silicon in orange
juice were only 15 percent of those observed when silicon
was not consumed with aluminum. Quartley et al. (1993)
demonstrated that oral consumption of silicic acid previously
to and concurrently with aluminum reduced tissue alumi-
num concentrations in rats four hours after dosing.
Jugdaohsingh et al. (2000) demonstrated that oligomeric
silica, but not monomeric silica, reduced dietary aluminum
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ALUMINUM
19
bioavailability by 67 percent in humans. The oligomeric
silica was not absorbed; the monomeric silica was. Addition
of silicon (6.5 mg/L of silicon) to water containing 527 |jgl/
L of aluininum resulted in the formation of hydro xyl-alumi-
nosilicates and decreased lysosomal accumulation of alumi-
num by freshwater snails, presumably due to poorer absorp-
tion of aluminum (Desouky et al., 2002).
Desouky et al. (2002) hypothesized that the interaction of
aluminum and silica may extend beyond absorption because
snails exposed to aluminum (without supplemental silicon)
accumulated more silica in their lysosomes as hydroxyl-alu-
minosilicates.
Calcium and Magnesium
Aluminum may share some of the active processes in-
volved in calcium absorption (Feinroth et al., 1982; Provan
and Yokel, 1988a). Accordingly, several investigators have
attempted to determine whether calcium- and magnesium-
deficient animals were more sensitive to oral aluminum ex-
posure. Yasui et al. (1991) found that rats deficient in cal-
cium and magnesium retained more aluminum in tissues.
Ecelbarger and Greger (1991) found that increasing the di-
etary calcium levels 4-fold (67 to 250 mmol/g diet of cal-
cium) resulted in reduced bone aluminum concentrations in
rats. However, Yokel et al. (2001) suggested that the pres-
ence of calcium and magnesium in the gut delayed but did
not reduce the absorption of aluminum.
Iron
Interactions between aluminum and iron theoretically
occur in a variety of tissues because aluminum is at least
partially transported in plasma by transferrin. The impor-
tance and the mechanism(s) of the interactions are contro-
versial. The stability constants for transferrin binding to Al"''-'
are 10 log scales lower than for iron (i.e., log K of 22 versus
12, respectively) (Martin et al., 1987). Fatemi et al. (1991)
estimated that 60 percent of the aluminum in human plasma
(at pH 7.4 with 5 |jM aluminum and 25 mM HCO3") would
be bound to transferrin, 34 percent to albumin, and the re-
mainder to citrate.
It is unlikely that aluminum and iron compete directly for
absorption. The addition of equimolar quantities of iron to a
gavage dose of aluminum did not affect tissue aluminum
levels of rats (Greger et al., 1995). The presence of Fe III in
in situ perfusion systems did not affect the luminal disap-
pearance or the intestinal absorption of aluminum (van der
Voet and de Wolff, 1987). However, the presence of Fe II
decreased the intestinal absorption of aluminum by decreas-
ing the release of aluminum into the blood from mucosal
cells.
Fernandez-Menendez et al. (1991) proposed that in iron
deficiency the decreased saturation of transferrin resulted in
greater aluminum absorption. In two studies, anemic rats
orally administered aluminum for 30 to 42 days excreted
more aluminum in urine and retained more aluminum in tis-
sues than normal rats (Cannata et al., 1991; Brown and
Schwartz, 1992). However, the ingestion of ferrofumarate
with aluminum aminoacetate for 90 days by renal patients
did not decrease plasma aluminum levels (Andersen et al.,
1987). Moreover, transferrin receptors are not present on the
apical surfaces of mucosal cells (Anderson et al., 1990).
An alternate explanation for the effect of dietary iron on
tissue aluminum levels involves the effect of iron deficiency
on the tissue turnover of aluminum. The half-lives of alumi-
num in liver (56 versus 17 days), muscle (33 versus 16 days),
spleen (29 versus 24 days), and serum (12 versus 8 days)
were longer in iron-deficient anemic rats than in controls
following a single oral aluminum dose (Greger et al., 1994).
TOXICOSIS
There are no practically important studies reporting the
toxic effects of a single oral dose of aluminum (ATSDR,
1999). The toxic effects of chronic (>2 weeks) oral expo-
sure to aluminum in livestock appear to be related to alumi-
num effects on general growth and longevity or on the
utilization of essential elements (NRG, 1980). Hence the
studies are presented accordingly. Table 3-1 summarizes
their findings.
Growth and Longevity
Few gross changes have been observed in normal animals
exposed to aluminum orally in long-term ( 6 months) stud-
ies in which nothing was done to enhance aluminum absorp-
tion. The longevity of rats exposed to aluminum (5 mg/L of
aluminum) in their drinking water throughout their life was
unaffected (Schroeder and Mitchener, 1975). Rabbits admin-
istered aluminum in water (5 mg/L of aluminum) for 12
months gained weight more slowly than controls but demon-
strated no histological changes except for elevation of tissue
aluminum concentrations (Wills et al., 1993). The food in-
take and weights of dogs were not adversely affected when
sodium aluminum phosphate (up to 3 percent of diet was
sodium aluminum phosphate) was added to their diets for six
months (Katz et al., 1984).
Similarly, Berlyne et al. (1972) observed that adding 1
percent or 2 percent aluminum chloride or aluminum sulfate
to the drinking water or administering aluminum hydroxide
(150 mg/kg BW/day of aluminum) by gavage to rats had no
adverse effects on the growth or organs of normal rats, ex-
cept to elevate tissue aluminum concentrations. However,
the administration of the same doses of aluminum to rats that
had five-sixths nephrectomies increased the death rate of
animals (Berlyne et al., 1972).
Neonatal animals may be more sensitive to aluminum.
Administration of aluminum chloride or aluminum lactate
(100 and 200 mg/kg BW/day of aluminum) by gastric
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MINERAL TOLERANCE OF ANIMALS
intubation to young (5- to 14-day-old) rats reduced body
weight and decreased plasma protein and albumin but in-
creased al globulins (Cherroret et al., 1995).
Bone Metabolism
More than 100 papers have been published on the impor-
tance of aluminum in the etiology of dialysis osteodystrophy
in human patients with uremia. There are two etiologies for
the osteodystrophy: contamination of dialysates with alumi-
num and the use of pharmaceutical levels of aluminum to
treat the hyperphosphatemia associated with renal failure,
especially in children (Alfrey, 1986; Committee on Nutri-
tion, 1986; Hewitt et al., 1990; Jeffery et al., 1996; ATSDR,
1999). Neither of these practices is important in the treat-
ment of uremic livestock, and references to the studies in
humans will not be included here.
Animal models (e.g., rats, dogs, mice) for renal osteodys-
trophy were generally created by injecting aluminum into
animals. In those cases, aluminum was deposited at osteoid
bone interfaces (Quarles et al., 1985) and inhibited osteo-
blast and osteoclast activities (Jeffery et al., 1996). Feeding
aluminum (37.6 pmol/g diet of aluminum) to normal rats for
6 or 9 months did not affect urinary excretion of hydrox-
yproline (a marker of bone resorption), but feeding alumi-
num to rats that had one kidney removed elevated hydrox-
yproline excretion (Ecelbarger et al., I994a,b). This suggests
that reductions in kidney function (as occurs with age) may
cause animals to be more sensitive to aluminum exposure in
terms of bone metabolism.
Phosphorus Metabolism
Many of the symptoms associated with aluminum toxic-
ity in bone and the occasional effects of aluminum on growth
reflect the effects of oral aluminum exposure on phosphorus
utilization. A series of case studies demonstrated that the
chronic ingestion of aluminum in antacids (as aluminum
hydroxide gels or magnesium aluminum hydroxide)
caused phosphorus depletion (with hypophosphatemia,
hypophosphaturia, hypercalciuria) and osteomalacia (bone
loss of calcium and phosphorus, fractures, bone pain, el-
evated alkaline phosphatase levels) in non-uremic human
patients (Bloom and Flinchum, 1960; Lotz et al., 1968;
Insogna et al., 1980). The symptoms appeared in only a small
number of subjects ingesting pharmaceutical levels of antac-
ids (0.5 to 9.6 g/day of aluminum) chronically (more than 6
months). Moreover, healthy adult males fed 125 mg/day of
aluminum as aluminum lactate experienced only a transient
(first 12 days) decrease in phosphorus absorption with no
other changes in phosphorus or calcium utilization (Greger
and Baler, 1983a).
Aluminum (>200 mg/kg of aluminum diet as aluminum
sulfate or hydroxide salts) has been shown to depress phos-
phorus utilization by rats (Ondreicka et al., 1966, 1971;
Greger et al., 1985). Ingestion of 2,000 mg/kg of aluminum
diet as aluminum chloride depressed growth, feed intake,
plasma phosphorus levels, and phosphorus absorption in
lambs, especially those fed low levels of phosphorus
(Valdivia et al., 1982). Chicks fed 0. 15 or 0.3 percent alumi-
num had depressed growth, reduced feed efficiency, and
decreased bone ash. Only the higher level of aluminum re-
duced plasma phosphorus levels and reduced egg production
(Wisser et al., 1990).
Another source of exposure to aluminum is when alum is
applied to poultry litter or dairy slurry. Moore et al. (1999,
2000) reported that broilers grown on alum-treated poultry
litter were significantly heavier than control (1.73 versus
1.66 kg) and had less mortality than controls (3.9 versus 4.2
percent). Not only did the application of the alum not ad-
versely affect the livestock, but also it had minimal negative
effects on crops grown on the land. Tall fescue yields on
fertilized fields were improved due to increased nitrogen
availability presumably because of less ammonia volatiliza-
tion (Moore et al., 1999). Soluble reactive phosphorus run-
off from treated pastures were greatly reduced (Codling et
al., 2002; Moore et al., 2000) without severely impacting
soil fertility, although phosphorus concentrations in plants
were progressively reduced during the three-year study (Co-
dhng et al., 2002).
Fluoride Utilization
The oral administration of high (1.8 g/day of aluminum
as antacids) and moderate (125 mg/day of aluminum as alu-
minum lactate) amounts of aluminum has been found to de-
press serum and urinary fluoride levels in healthy adult hu-
mans (Spencer et al., 1981; Greger and Baler, 1983a).
Similarly rabbits given aluminum in their drinking water
(100 and 500 mg/g water of aluminum as aluminum chlo-
ride) accumulated less fluoride in their tissues (Ahn et al.,
1995). However, rabbits accumulated more aluminum in
bone when the fluoride content of the drinking water was
increased.
Animal scientists have used knowledge of the interaction
between aluminum and fluoride to reduce fluoride toxicity.
Aluminum has been intentionally added to the diets of sheep
(3.3 g aluminum chloride/day) to reduce the symptoms of
fluorosis (mottling of teeth) in animals provided with 30 mg/
kg water of fluoride (Said et al., 1977). Although the inges-
tion of aluminum increased fecal fluoride and reduced uri-
nary and tissue fluoride levels, the incidence and severity of
mottling of teeth was not reduced. Similarly, aluminum (295
or 550 mg/kg diet of aluminum) was added to the diets of
turkeys fed fluoride-contaminated phosphate fertilizers as a
phosphorus source (Cakir et al., 1977). The aluminum par-
tially prevented the toxic effects of the fluoride (i.e., reduced
bone fluoride concentrations and increased weight gain). The
addition of aluminum ( 1 ,040 mg/kg diet of aluminum as alu-
minum sulfate) to diets reduced the toxic effects (i.e..
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ALUMINUM
21
reduced feed intake, reduced egg production, and increased
tissue fluoride levels) of dietary fluoride (1,300 mg/kg of
fluoride) in laying hens (Hahn and Guenter, 1986).
Calcium and Other Minerals
The effect of dietary aluminum on the utilization of other
minerals is less consistent in livestock. Lambs fed aluminum
(> 1,450 mg/kg diet aluminum as aluminum chloride) had
reduced calcium absorption, but no changes in tissue cal-
cium concentrations; lower concentrations of magnesium in
some tissues; and minor changes in tissue iron and copper
concentrations in two studies (Valdivia et al., 1982; Rosa et
al., 1982). Although cows with clinical grass tetany had el-
evated concentrations of aluminum in their ruminal dry mat-
ter than did control cows or asymptomatic, hypomagnesemic
cows, the administration of aluminum orally to lactating
cows did not reduce plasma magnesium concentrations
(Kappel et al., 1983). Similarly, dietary aluminum had small
inconsistent effects on tissue concentrations of calcium, mag-
nesium, and trace elements in rats fed generally balanced diets
(Greger et al., 1985; Ecelbarger and Greger, 1991; Ecelbarger
et al., 1994b; Belles et al., 2001; Yasui et al., 1990).
Neurological Symptoms
Aluminum is known to be part of the etiology of dialysis
dementia and hypothesized to be part of the etiology of a
progressive dementing encephalopathy reported in occa-
sional industrial workers and in patients with amyotrophic
lateral sclerosis with Parkinson's dementia in Guam. Brain
accumulation of aluminum has also been associated with the
development of Alzheimer's disease in some patients (King
et al., 1981; Committee on Nutrition, 1986; Ganrot, 1986:
Strong et al., 1996; Savory et al., 1996). Injection of alumi-
num, especially intracisternally, will induce neurological
changes in animal models (Wisniewski et al., 1980; ATSDR,
1999). The effects of orally administered aluminum on the
brain are more debatable. Only those studies in which alumi-
num was provided orally are cited here.
Administration of aluminum (0.3 percent Al as aluminum
sulfate) in drinking water for 30 days resulted in impairment
of both consolidation and extinction of passive avoidance
tasks in rats with a slight increase in hippocampal muscar-
inic receptor numbers (Connor et al., 1988). Rats orally ad-
ministered aluminum (100 mg/ kg BW/day of aluminum)
for 90 days accumulated more aluminum in their brains, were
slower to learn a labyrinth, had increased brain acetylcho-
linesterase activity, and had decreased brain choline-
acetyltransferase activity (Bilkei-Gorzo, 1993).
Mice fed high aluminum levels (1,000 mg/kg diet of alu-
minum as aluminum lactate) were less active than controls
after 6 weeks (Golub et al., 1989) and were less active, had
decreased grip strength, and increased startle responses after
90 days (Golub et al., 1992). When mice were fed aluminum
(500 or 1,000 mg/kg diet of aluminum as aluminum lactate
to dam and then offspring) from conception to weaning or to
adulthood, mice attained training faster but had reduced grip
strength (Golub et al., 1995). The effects were not greater in
mice fed aluminum to adulthood than just to weaning.
Other research groups fed animals diets that maximized
the bioavailability of aluminum to potentially increase the
absorption and accordingly the neurological toxicity of di-
etary aluminum. For example, Oteiza et al. (1993) observed
that mice fed diets containing 1 ,000 mg/kg diet of aluminum
as aluminum chloride with sodium citrate accumulated more
aluminum in the brain nuclear fraction and spinal cord, had
lower grip strength, and greater startle responsiveness after
5 and 7 weeks. Old (18 months of age) rats exposed to alu-
minum (100 mg/kg BW/day of aluminum) in drinking water
with citrate (356 mg/kg BW/day of citrate) had decreased
numbers of synapses and a greater percentage of perforated
synapses than controls, but no changes in behavior
(Colomina et al., 2002).
Several groups fed low calcium levels to increase ani-
mals' sensitivity to aluminum. Garruto etal. (1989) observed
that cynomolgus monkeys fed a low calcium (3,200 mg/kg
diet) diet with aluminum (125 mg/day of aluminum) and
manganese (50 mg/day of manganese) for 41 to 46 months
had more degenerative changes (that were consistent with
early Alzheimer's disease or Parkinson's dementia in Guam)
in the central nervous system than control monkeys. Golub
andGermann (2001) observed growth depression and poorer
performance on standardized motor tests in mice as adults
when dams were exposed to aluminum (1,000 mg/kg diet of
aluminum as aluminum lactate) with marginal levels of cal-
cium and magnesium during pregnancy and lactation. Kihira
et al. (2002) observed that mice fed a low rather than recom-
mended levels of calcium (2,500 versus 5,000 mg/kg diet of
calcium) with aluminum (15,600 mg/kg diet of aluminum
hydroxide) for 11 to 25 months accumulated more
hyperphosphorylated tau protein in the cortical neurons and
had more atrophic neurons in the central nervous system.
Pratico et al. (2002) reported that transgenic mice that
over-expressed human amyloid precursor protein (but not
wild-type littermates) had increased brain isoprostane levels
and more amyloid b peptide formation and deposition when
aluminum was added to their diets. The effects of aluminum
were reversed by additional dietary vitamin E.
In general, experimental animals did not exhibit large
behavioral changes because of oral aluminum exposure even
when fed diets that augmented the bioavailability of alumi-
num. It is unlikely that aluminum is part of any neurological
syndromes in livestock.
Fish and Mollusks
The effects of aluminum on fish and mollusks appear to
be unique and worthy of a separate discussion. Acidification
of the aquatic environment often causes aluminum to be
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22
MINERAL TOLERANCE OF ANIMALS
mobilized into tiie aqueous environment. Atlantic salmon
(Salmo salar) exposed to acidified water (pH 5.2) with alu-
minum (50 |Jg/L of aluminum as aluminum chloride) for 36
days reduced their feed consumption at first but lost weight
and increased their swimming activity throughout the test
period (Brodeur et al., 2001). Rainbow trout fry avoided alu-
minum at concentrations as low as 1 |imole/L of aluminum
at pH 5 but were insensitive to aluminum at pH 6 (Exiey,
2000).
Temperature may also affect the sensitivity of fish to alu-
minum. Graylings (Thymallus thymallus) were exposed to
water containing 1 mg/L of iron and 100 (ig/L of aluminum
as aluminum sulfate at pH 5.5 and at pH 6.9 (control). Fifty
percent of the fish exposed to the aluminum at pH 5.5 died
after 2 weeks when the temperature was 13°C but none died
at 3°C. Surviving fish at both test temperatures suffered gill
damage (adherence of lamellae), increased hematocrits, re-
duced plasma chloride levels, and reduced oxygen consump-
tion. The fish exposed to aluminum at the higher tempera-
ture recovered more completely than those exposed at the
lower temperature (Peuranen et al., 2003).
Acclimation to aluminum may also affect the severity of
sjTTiptoms when fish are exposed to toxic levels of alumi-
num. Juvenile rainbow trout {Oncorhynchus mykiss) were
exposed to a pulse of aluminum (36 |Jg/L of aluminum at pH
5.2) for 4 days. One group was exposed to a lower level of
aluminum (24 pg/L of aluminum) for 16 days before and 10
days after the pulse; another was acclimated only to the pH.
Fish became hypoactive upon exposure to the lower level of
aluminum but recovered after 4 days. Exposure to the higher
level of aluminum by the acclimated fish resulted in
hypoactivity, but they quickly recovered normal swimming
behavior during the 4-day pulse; mortality was 4 percent. In
contrast, the fish not acclimated to the lower level of alumi-
num became hypoactive when exposed to 36 |Jg/L of alumi-
num and did not recover in the 6 days after the pulse; mortal-
ity was 26 percent (Allin and Wilson, 2000).
Mollusks appear to have several ways to avoid exposure
to aluminum. Freshwater mussels (Anodonta cygnea L) re-
duced their filtering activity by reducing shell opening by 50
percent when exposed to 500 |Jg/L of aluminum as alumi-
num nitrate at neutral pH for 15 days (Kadar et al., 2001).
Freshwater snails (Lymnaea stagnalis) accumulated alumi-
num, silicon, phosphorus, and sulfur in non-absorbable gran-
ules in their digestive cells when exposed to aluminum
(Elangovan et al., 2000).
TISSUE LEVELS
Humans do not accumulate large body burdens of alumi-
num because of oral exposure to dietary aluminum from a
variety of undefined sources. Total body aluminum loads for
healthy adults have been estimated to range from 30 to 300
mg aluminum (Skalsky and Carchman, 1983; Ganrot, 1986).
Alfrey (1986) estimated that normal tissue (bone and soft
tissue, except lungs) levels are 1 to 4 mg/kg dry weight of
aluminum. Concentrations of aluminum in serum are lower
than in other tissues; 1 to 5 |Jg/L of aluminum are typical for
serum samples drawn from fasted, normal human subjects
(Versieck and Cornells, 1980; Greger and Baler, 1983b;
Savory and Wills, 1988).
Rodents exposed to aluminum (as aluminum sulfate, chlo-
ride, hydroxide, palmitate, lactate, phosphate, or citrate)
orally accumulated more aluminum in bone than soft tissues
(Ondreicka et al., 1966, 1971; Greger et al., 1985, 1986;
Slanina et al., 1984, 1985). Rats fed purified control diets
(that contained less than 15 mg/kg diet of aluminum) re-
tained less than 0.3 pg/g wet tissue of aluminum in their soft
tissues (kidneys, livers, brains, and muscles) and less than
0.9 |ig/g wet tissue of aluminum in bone (Greger and Pow-
ers, 1992; Ecelbarger et al., 1994a,b; Sutherland and Greger,
1998). When rats were fed 1,000 mg/kg diet of aluminum in
these studies, the concentrations of aluminum in soft tissues
sometimes increased significantly but were generally less
than 0.7 |jg/g wet tissue of aluminum and in bone were less
than 2.0 |Jg/g wet tissue of aluminum.
Similarly steers (Valdivia et al., 1978), sheep (Valdivia et
al., 1982), and chickens (Wisser et al., 1990) fed 800-3,000
mg/kg diet of aluminum accumulated aluminum in their tis-
sues, but the concentrations of aluminum in their tissues were
still <1 1 |jg/g dry tissue of aluminum.
The amounts of aluminum in tissues were much greater if
kidney function of the rats had been reduced or aluminum
had been given orally by gavage to fasted animals. In those
cases, soft tissues and bone concentrations of aluminum were
as great as 6 and 27 |ig/g wet tissue of aluminum, respec-
tively (Greger and Powers, 1992; Domingo et al., 1994;
Greger etal., 1994).
Table 3-2 summarizes the effect of aluminum on selected
tissues.
MAXIMUM TOLERABLE LEVELS
The Agency for Toxic Substances and Disease Registry
(ATSDR, 1999) noted that toxicity to aluminum had been
reported many times in patients with reduced kidney func-
tion, but limited data were available about toxic responses to
aluminum in normal humans. They suggested a LOAEL
(lowest-observed-adverse-effect level) of 130 mg/kg/day of
aluminum on the basis of the observation that adult mice
exposed to dietary aluminum lactate for 6 weeks decreased
their spontaneous motor activity (Golub et al., 1989). This
would mean a 70-kg human should be unaffected by inges-
tion of 9.1 g of aluminum daily (18,000 mg/kg dry diet of
aluminum if 0.5 kg dry diet is consumed daily). The occa-
sional case histories of adverse responses to aluminum-con-
taining antacids among adults with normal kidney function
suggest that this LOAEL is too high.
Ingestion of 2,000 and 1,450 mg/kg diet of aluminum
depressed growth, feed intake, plasma phosphorus levels.
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ALUMINUM
23
and/or phosphorus absorption in lambs (Valdivia et al., 1982;
Rosa et al., 1982, respectively). Laying hens (White Leg-
horn) fed 1,500 mg/kg diet of aluminum had depressed
growth production (Wisser et al., 1990). Thus, a cautious
maximum tolerable level of aluminum in the diets of live-
stock would be 1,000 mg/kg diet of aluminum.
The NRC (1982) considered the minimum toxic effect
dose of aluminum in water for rats to be 1,000 mg/kg/day of
aluminum. If 200-g rats consumed 20 ml water daily, the
maximum toxic level would be 10,000 mg/L water of alumi-
num (which exceeds the solubility of aluminum in non-acidic
solutions). Brodeur et al. (2001) observed toxic effects in
fish exposed to 36 |Jg/L water of aluminum at pH 5.2. These
data suggest that fish are more sensitive to aluminum expo-
sure than are mammals.
FUTURE RESEARCH NEEDS
Research on the role of aluminum in the etiology of dis-
ease syndromes in humans has little significance to livestock
production industry but could be of interest to veterinarians
treating old and/or diseased pets. The relationship of tissue
aluminum concentration and neurological problems in pets,
especially those with reduced renal function, deserves con-
sideration.
The effects of acid rain and the resulting aluminum con-
tamination of aquatic environments will continue to deserve
further study. In both cases, the mediation of the effects of
aluminum exposure by other dietary elements is likely to be
important and worthy of further study.
SUMMARY
Aluminum is a ubiquitous element that is not essential to
mammals. Livestock are occasionally exposed to high levels
of aluminum, but toxicity to orally administered aluminum
is not a problem as long as gut and kidney functions are
normal. The first signs of aluminum toxicity in normal ani-
mals reflect the adverse effect of dietary aluminum on phos-
phorus utilization. On the other hand, fish are very sensitive
to aluminum in acidic water.
REFERENCES
Adler. A. J., and G. M. Berlyne. 1985. Duodenal aluminum absorption in
tlie rat: effect of vitamin D. Am. J. Physiol. 249:0209-213.
Adler, A. J., C. Caruso, and G. M. Berlyne. 1991. Effect of aluminum on
calcium binding to bovine intestinal calcium-binding protein. Mineral
Electrolyte Metab. 17:141-146.
ATSDR (Agency for the Toxic Substances and Disease Registry). 1999.
Toxicological profile for aluminum. Atlanta, GA: U.S. Department of
Health and Human Services, Public Health Service. Available at: http:
//www. atsdr.cdc.gov/toxprofiles/tp22. html. Accessed January 24, 2004.
Ahn, H. W., B. Fulton, D. Moxon, and E. H. Jeffery. 1995. Interactive
effects of fluoride and akiminum uptake and accumulation in bones of
rabbits administered both agents in their drinking water. J. Toxicol.
Environ. Health 44:337-350.
Alfrey, A. C. 1986. Aluminum. Pp. 399^13 in Trace Elements in Human
and Animal Nutrition, Vol. 2, W. Mertz, ed. New York: Academic Press.
Alfrey, A. C. 1989. Physiology of aluminum in man. Pp. 101-124 in Alu-
minum and Health: A Critical Review. New York: Marcel Dekker.
Alfrey, A. C, A. Hegg, and P. Craswell. 1980. Metabolism and toxicity of
aluminum in renal failure. Am. J. Clin. Nutr. 33:1509—1516.
AUin C. J., and R. W. Wilson. 2000. Effects of pre-acclimation to alumi-
num on the physiology and swimming behavior of juvenile rainbow
trout (Oncorhynchus mykiss) during a pulsed exposure. Aquatic Toxicol.
51:213-224.
Andersen, J. R., H. Blaehi', E. S. Johansen, and S. Madesen. 1987. The
impact of iron on the intestinal absorption of aluminum in chronic renal
insufficiency. Trace Elem. Med. 4'A2-A4.
Anderson, G. S., L. W. Powell, and A. W. Halliday. 1990. Transferrin re-
ceptor distribution and regulation in the rat small intestine: effect of iron
stores and erythi'opoiesis. Gastroenterology 98:576-585.
Belles, M., M. L. Albina, D. J. Sanchez, J. Corbella, and J. L. Domingo.
200 1 . Effects of oral aluminum on essential trace element metabolism
during pregnancy. Biol. Trace Elem. Res. 79:67-81.
Berlyne, G. M., J. Ben, E. Knoff R. Yagil, G. Weinberger, and G. M.
Danovitch. 1972. Aluminum toxicity in rats. Lancet 1:564-568.
Berthon, G., and S. Dayde. 1992. Why aluminum phosphate is less toxic
than aluminum hydroxide. J. Am. Coll. Nutr. 11:340-348.
Bilkei-Gorzo, A. 1993. Neurotoxic effect of enteral aluminum. Food Chem.
Toxicol. 31:357-361.
Birchall, J. D. 1992. The interrelationship between silicon and aluminum in
the biological effects of aluminum. Pp. 50-61 in Aluminum in Biology
and Medicine. Ciba Found. Symp. 169, Chichester, UK: John Wiley
and Sons.
Birchall, J. D., and J. S. Chappell. 1988. The chemistry of aluminum and
silicon in relation to Alzheimer's disease. Clin. Chem. 34:265-267.
Bloom, W., and D. Flinchum. 1960. Osteomalacia with pseudo fractures
caused by the ingestion of aluminum hydroxide. J. Am. Med. Assn.
174:1327-1330.
Brodeur, J. C, F. 0kland, B. Finstad, D. G. Dixon, and S. R. S. McKinley.
2001. Effect of subchronic exposure to aluminum in acidic water on
bioenergetics of Atlantic salmon (Salmo salar). Ecotoxicol. Environ.
Safety 49:226-234.
Brown, T. S., and R. Schwartz. 1992. Aluminum accumulation in serum,
liver and spleen of Fe-dependent and Fe- adequate rats. Biol. Trace Elem.
Res. 34:1-10.
Bureau of Radiological Health and Training Institute. 1970. Pp. 237-238 in
Radiological Health Handbook. Rockville, MD: U.S. Department of
Health.
Burgoin, B. P. 1992. Alumino-silicate content in calcium supplements de-
rived from various carbonate deposits. Bull. Environ. Contam. Toxicol.
48:803-808.
Cakir, A., T. W. Sullivan, and F. J. Struwe. 1977. Effect of supplemental
aluminum on the value of fertilizer phosphates in turkey diets. Poult.
Sci. 56:544-549.
Cannata, J. B., I. Fernandez-Soto, M. J. Fernandez-Menendez, K.
Fernandez-Martin, S. J. McGregor, J. H. Brock, and S. D. Hall. 1991.
Role of iron metabolism in absorption and cellular uptake of aluminum.
Kidney Int. 39:799-803.
Cherroret, G., B. Capolaghi, M. F. Hutin, D. Burnel, D. Desor. and P. R.
Lehr. 1995. Effects of postnatal aluminum exposure on biological pa-
rameters in the rat plasma. Toxicol. Lett. 78:119-125.
Codling, E. E., R. L. Chaney, and C. L. Mulchi. 2002. Biomass yield and
phosphorus availability to wheat grown on high phosphorus soils
amended with phosphate inactivating residues. I. Drinking water treat-
ment residue. Commun. Soil Sci. Plant Anal. 33:1039—1061.
Colomina, M. T., J. L. Roig, D. J. Sanchez, and J. L. Domingo. 2002. Influ-
ence of age on aluminum-induced neurobehavioral effects and morpho-
logical changes in rat brain. Neurotoxicol. 23:775—781.
Committee on Nutrition. 1986. Aluminum toxicity in infants and children.
Pediatrics 78:1150-1154.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
24
MINERAL TOLERANCE OF ANIMALS
Connor. D. J., R. S. Jope, and L. E. Harrell. 1988. Chronic, oral aluminum
administration to rats: cognition and cholinergic parameters. Pharmacol.
Biochem. Behav. 31:467^74.
Conway, E. L., C. O'Callaghan, O. H. Drummer, L. G. Howes, and W. J.
Louis. 1994. A single-dose comparison of the bioavailability of alumi-
num from two formulations of sucralphate in normal volunteers.
Biopharm. Drug Dispos. 15:253-261.
Cox, K. A., and M. A. Dunn. 200 1 . Aluminum toxicity alters the regulation
of calbinden-D28K protein and on RNA expression in chick intestine. J.
Nutr. 131:2007-2013.
Desouky, M., R. Jugdaohsingh, C. R. McCrohan, K. N. White, and J. J.
Powell. 2002. Aluminum-dependent regulation of intracellular silicon
in the aquatic invertebrate Lymnaea stagnalis. Proc. Natl. Acad. Sci.
USA 99:3394-3499.
Domingo, J. L., M. Gomez, J. M. Llobet, D. del Castillo, and J. Corbella.
1994. Influence of citric, ascorbic and lactic acids on the gastrointesti-
nal absorption of aluminum in uremic rats. Nephron 66:108-109.
Domingo, J. L., M. Gomez, J. M. Llobet, and J. Corbella. 1 99 1 . Influence of
some dietary constituents on aluminum absorption and retention in rats.
Kidney Int. 39:598-601.
Donald, J. M., M. S. Golub, M. E. Gershwin, and C. L. Keen. 1989.
Neurobehavioral effects in offspring of mice given excess aluminum in
diet during gestation and lactation. Neurotoxicol. Teratol. 11:345-351.
Eastwood, J. B., G. E. Levin, M. Pazianas, A. P. Taylor, J. Denton, and A.
J. Freemont. 1990. Aluminum deposition in bone after contamination of
drinking water supply. Lancet 336:462^64.
Ecelbarger, C. A., and J. L. Greger. 199 1 . Dietary citrate and kidney function
affect aluminum, zinc and iron utilization in rats. J. Nutr. 1 2 1 : 1 755-1 762.
Ecelbarger, C. A., G. G. MacNeil, and J. L. Greger. 1994a. Importance of
kidney function and duration of exposure on aluminum accumulation in
mature rats. Nutr. Res. 14:577-586.
Ecelbarger, C. A., G. G. MacNeil, and J. L. Greger. 1994b. Tissue alumi-
num accumulation and toxic consequences in rats chronically fed alu-
minum with and without citrate. J. Agric. Food Chem. 42:2220-2224.
Eden, T. 1976. Tea. London: Longman, pp. 8-15.
Edwardson, J. A., P. B. Moore, 1. N. Ferrier, J. S. Lihey, G. W. A. Newton,
J. Barker, J. Templar, and J. P. Dey. 1993. Effect of silicon on gas-
trointestinal absorption of aluminum. Lancet 342:21 1-212.
Elangovan, R., C. R. McCrohan, S. Balance, J. J. Powell, and K. N. White.
2000. Localization and fate of aluminum in the digestive gland of the
freshwater snail Lymnaea stagnalis. Tissue & Cell 32:79-87.
Exley, C. 2000. Avoidance of aluminum by rainbow trout. Environ. Toxicol.
Chem. 19:933-939.
Fatemi, S. J. A., D. J. Williamson, and G. R. Moore. 1991. A -^Al NMR
investigation of A1+' binding to small carboxylic acids and the proteins
albumin and transferring. J. Inorg. Biochem. 46:35^0.
Feinroth, M., M. V. Feinroth, andG. M. Berlyne. 1982. Aluminum absorp-
tion in the rat everted gut sac. Mineral Electrolyte Metab. 8:29—35.
Fernandez-Menendez, M. J. F., G. S. Fell, J. H. Brock, and J. B. Cannata.
1991. Aluminum uptake by intestinal cells: effect of iron status and
precomplexation. Nephrol. Dial. Transplant. 6:672-674.
Flaten, T. P. 1995. Components of drinking water and risk of cognitive
impairment in the elderly. Am. J. Epidemiol. 141:173.
Froment, D. H., B. Buddington, N. L. Miller, and A. C. Alfrey. 1989a. Effect
of solubility on the gastrointestinal absorption of aluminum from various
aluminum compounds in the rat. J. Lab. Clin. Med. 1 14:237-242.
Froment, D. H., B. A. Mohtoris, B. Buddington, N. Miller, and A. C. Alfrey.
1989b. Site and mechanism of enhanced gastrointestinal absorption of
aluminum by citrate. Kidney Int. 36:978-984.
Fulton, B., and E. H. Jeffrey. 1990. Absorption and retention of aluminum
from drinking water. 1. Effect of citrate and ascorbic acids on aluminum
tissue levels in rabbits. Fundam. Appl. Toxicol. 14: 788—796.
Fulton, B., S. Jaw, and E. H. Jeffery. 1989. Bioavailability of aluminum
from drinking water. Fundam. Appl. Toxicol. 12:144-150.
Ganrot, P. O. 1986. Metabolism and possible health effects of aluminum.
Environ. Health Perspect. 65:363^441.
Garruto. R. M.. S. K. Shankar, R. Yanagihara, A. M. Salazar, H. L. Amyx,
and D. C. Gajdusek. 1989. Low-calcium, high-aluminum diet-induced
motor neuron pathology in cynomolgus monkeys. Acta Neuropathol.
78:210-219.
Glynn, A. W., A. Sparen, L. G. Danielsson, G. Haegglund, and L. Jorhem.
1995. Bioavailability of labile aluminum in acidic drinking water: a
study in the rat. Food Chem. Toxicol. 33:403^08.
Golub, M. S., and S. 1. Germann. 2001. Long-term consequences of de-
velopmental exposure to aluminum in a suboptimal diet for growth
and behavior of Swiss Webster mice. Neurotoxicol. Teratol. 23:
365-372.
Golub, M. S., J. M. Donald, M. E. Gershwin, and C. L. Keen. 1989. Effects
of aluminum ingestion on spontaneous motor activity of mice.
Neurotoxicol. Teratol. 11:231-235.
Golub, M. S., B. Han, C. L. Keen, and M. E. Gershwin. 1992. Effects of
dietary aluminum excess and manganese deficiency on neurobehavioral
endpoints in adult mice. Toxicol. Appl. Pharmacol. 112:154—160.
Golub, M. S., B. Han, C. L. Keen, E. Gershwin, and R. P. Tarara. 1995.
Behavioral performance of Swiss Webster mice exposed to excess di-
etary aluminum during development or during development and as
adults. Toxicol. Appl. Pharmacol. 133:64—72.
Greger, J. L. 1985. Aluminum content of the American diet. Food Technol.
9:73, 74, 76, 78-80.
Greger, J. L. 1993. Aluminum metabolism. Ann. Rev. Nutr. 13:43-63.
Greger, J. L., and M. J. Baler. 1983a. Effect of dietary aluminum on mineral
metabolism of aduh males. Am. J. Clin. Nutr. 38:41 1-419.
Greger, J. L., and M. J. Baier. 1983b. Excretion and retention of low or
moderate levels of aluminum by human subjects. Food Chem. Toxicol.
21:473^77.
Greger, J. L., and C. F. Powers. 1992. Assessment of exposure to parental
and oral aluminum with and without citrate using a desferrioxamine test
in rats. Toxicol. 76:119-132.
Greger, J. L., and G. M. Radzanowski. 1995. Tissue aluminum distribution
in growing mature and aging rats: relationship to changes in gut, kidney
and bone metabolism. Food Chem. Toxicol. 33:867-875.
Greger, J. L. and J. E. Sutherland. 1997. Aluminum exposure and metabo-
lism. Crit. Rev. Clin. Lab. Sci. 34:439^74.
Greger, J. L., E. N. Bula, and E. T. Gum. 1985a. Mineral metabolism of rats
fed moderate levels of various aluminum compounds for short periods
of time. J. Nutr. 115:1708-1716.
Greger, J. L., M. M. Chang, and G. G. MacNeil. 1994. Tissue turnover of
aluminum and Ga-67: effect of iron status. Proc. Soc. Exp. Biol. Med.
207:89-96.
Greger, J. L., M. M. Chang, and G. M. Radzanowski. 1995. Comparison of
tissue retention of aluminum and Ga-67: effects of iron status in rats.
Toxicol. 100:1-9.
Greger, J. L., W. Goetz, andD. Sullivan. 1985b. Aluminum levels in foods
cooked and stored in aluminum pans, trays and foil. J. Food Prot.
48:772-777.
Hahn, P. H., and W. Guenter. 1986. Effect of dietary fluoride and aluminum
on laying hen performance and fluoride concentration in blood, soft
tissue, bone and egg. Poult. Sci. 65:1343—1349.
Hem, S. 1. 2002. Elimination of aluminum adjuvants. Vaccine 20 (suppl.
3):S40^3.
Hewitt, C. D., J. Savory, and M. R. Wills. 1990. Aspects of aluminum
toxicity. Clin. Lab. Med. 10:403-422.
Hopkins, H., and J. Eisen. 1959. Mineral elements in fresh vegetables from
different geographic areas. J. Agric. Food Chem. 7:633-638.
Horecker, B. L., E. Stotz, and T. R. Hogness. 1939. The promoting effect of
aluminum, chromium, and the rare earths in the succinic dehydroge-
nase-cytochrome system. J. Biol. Chem. 128:251—256.
Insogna, K. L., D. R. Bordley, S. F. Caro, and D. H. Lockwood. 1980.
Osteomalacia and weakness from excessive antacid ingestion. J. Am.
Med. Assn. 244:2544-2546.
Ishihara, N., and T. Matsushiro. 1986. Biliary and urinary excretion of met-
als in humans. Arch. Environ. Health 41:324—330.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
ALUMINUM
25
Ittel, T. H., R. Kluge, and H. G. Sieberth. 1988. Enhanced gastrointestinal
absorption of aluminum in uraemia: time course and effect of vitamin
D. Nephrol. Dial. Transplant. 3:617-623.
Ittel, T. H., B. K. Koppe, and H. G. Sieberth. 1990. Differential effect of
steroids and chloroquine on the intestinal absorption of aluminum and
calcium. Nephrol. Dial. Transplant. 5:860-867.
Ittel, T. H., C. P. Paulus, S. Handt, F. Hofstadter, and H. G. Sieberth. 1992.
Induction of intestinal mucosal atrophy by difluoromethylornithine: a
nonuremic model of enhanced aluminum absorption. Miner. Electrolyte
Metab. 18:15-23.
Jeffery, E. H., K. Abreo, E. Burgess, J. Cannata, and J. L. Greger. 1996.
Systemic aluminum toxicity: effects on bone, hematopoietic tissue, and
kidney. J. Toxicol. Environ. Health 48:649-665.
Jones, K. C., and B. G. Bennett. 1986. Exposure of man to environmental
aluminum — an exposure commitment assessment. Sci. Total Environ.
52:65-82.
Jouhanneau, P., B. Lacour, G. Raisbeck, F. Yiou, H. Banide, E. Brown,
and T. Drtieke. 1993. Gastrointestinal absorption of aluminum in rats
using -^Al and accelerator mass spectrometry. Clin. Nephrol. 40:
244-248.
Jugdaohsingh, R., D. M. Reffitt, C. Oldham, J. P. Day, L. K. Fifield, and R.
P. H. Thompson. 2000. Oligomeric but not monomeric silica prevents
aluminum absorption in humans. Am. J. Clin. Nutr. 71:9444—9449.
Kadar, E., J. Salanki, R. Jugdaohsingh, J. J. Powell, C. R. McCrohan, and
K.N. White. 2001. Avoidance response to aluminum in the freshwater
bivalve Anodonta cygnea. Aquatic Toxicol. 55:137-148.
Kaehny, W. D., A. P. Hegg, and A. C. Alfrey. 1977. Gastrointestinal absorp-
tion of aluminum containing antacids. N. Engl. J. Med. 296:1389—1390.
Kahn, R. A. 1991. Fluoride is not an activator of the smaller (20-25 kDa)
GTP-binding proteins. J. Biol. Chem. 266:15595-15597.
Kappel, H., H. Youngberg, R. H. Ingraham, F. G. Hembry, D. L. Robinson,
and J. H. Cherney. 1983. Effects of dietary aluminum on magnesium
status of cows. Am. J. Vet. Res. 44:770-773.
Katz, A. C, D. W. Frank, M. W. Sauerhoff, G. M. Zwicker, and R. I.
Freudenthal. 1984. A 6-month dietary toxicity study of acidic sodium
aluminum phosphate in beagle dogs. Food Chem. Toxicol. 22:7-9.
Keith, L. S., D. E. Jones, and C. H. Chou. 2002. Aluminum toxicokinetics
regarding infant diet and vaccinations. Vaccine 20 (suppl. 3):S13-17.
Kihira, T., S. Yoshida, Y. Yase, S. Ono, and T. Kondo. 2002. Chronic low-
Ca/Mg high-Al diet induces neuronal loss. Neuropathol. 22:171-179.
King, S. W., J. Savory, and M. R. Wills. 1981. The clinical biochemistry of
aluminum. CRC Crit. Rev. Chn. Lab. Sci. 14:1-20.
Kleber, C. J., and M. S. Putt. 1984. Aluminum and dental caries. A review
of the literature. Clin. Prev. Dent. 6:14-25.
Klein, G. L., M. B. Heyman, T. C. Lee, N. L. Miller, G. Marathe, W. K.
Gourley, and A. C. Alfrey. 1988. Aluminum-associated hepatobiliary
dysfunction in rats: relationships to dosage and duration of exposure.
Pediatr. Res. 23:275-278.
Klein, G. L., S. M. Ott, A. C. Alfrey, D. J. Sherrard, T. K. Hazlet, N. L.
Miller, N. A. Maloney, W. F. Berguist, M. E. Ament, and J. W. Coburn.
1 982. Aluminum as a factor in the bone disease of long-term parenteral
nutrition. Trans. Assoc. Am. Physicians. 95:155—164.
Kostyniak, P. J. 1983. An electrothermal atomic absorption method for alu-
minum analysis in plasma: identification of source contamination in
blood sampling procedures. J. Anal. Toxicol. 7:20-23.
Kovalchic, M. T., W. D. Kaehny, A. P. Hegg, J. T. Jackson, and A. C.
Alfrey. 1978. Aluminum kinetics during hemodialysis. J. Lab. Clin.
Med. 92:712-720.
Lefcourt, A. M., and J. J. Mesinger. 2001. Effect of adding alum or zeolite
to dairy slurry on ammonia volatilization and chemical composition. J.
Dairy Sci. 84:1814-1821.
Lione, A. 1983. The prophylactic reduction of aluminum intake. Food
Chem. Toxicol. 21:103-109.
Lione, A. 1985. Aluminum toxicity and the aluminum-containing medica-
tions. Pharmac. Ther. 29:255-285.
Liukkonen-Lilja, H., and S. Piepponen. 1992. Leaching of aluminum from
aluminum dishes and packages. Food Addit. Contam. 9:213—223.
Lotz, M., E. Zisman, and F. C. Bartter. 1968. Evidence for a phosphorus-
depletion syndrome in man. N. Engl. J. Med. 278:409^15.
Malakoff, D. 2000. Aluminum is put on trial as a vaccine booster. Science
288:1323-1324.
Martin, R. B. 1991. Fe*-^ and Al*' hydrolysis equilibria. Cooperatively in
A1+' hydrolysis reactions. J. Inorganic Biochem. 44:141—147.
Martin, R. B., J. Savory, S. Brown, L. Berholf, and M. R. Wills. 1987.
Transferrin binding of Al+3 and Fe+\ Clin. Chem. 33:405^07.
Miller, R. G., F. C. Kopfler, K. C. Kelty, J. A. Stober, and N. S. Ulmer.
1984. The occurrence of aluminum in drinking water. J. Am. Water
Assoc. 76:84-91.
Moore, Jr., P. A., T. C. Daniel, and D. R. Edwards. 1999. Reducing phos-
phorus runoff and improving poultry production with alum. Poult. Sci.
78:692-698.
Moore, Jr., P. A., T. C. Daniel, and D. R. Edwards. 2000. Reducing phos-
phorus runoff and inhibiting ammonia loss from poultry manure with
aluminum sulfate. J. Environ. Qual. 29:37^9.
NRC (National Research Council). 1980. Aluminum. Pp. 8-23 in Mineral
Tolerance of Domestic Animals. Washington, D.C.: National Academy
Press.
NRC. 1982. Drinking Water and Health. Vol. 4. Washington, D.C.: Na-
tional Academy Press.
NRC. 1984. 1982 Poundage Update of Food Chemicals. Washington, D.C.:
National Academy Press.
Nagy, E., and K. Jobst. 1994. The kinetics of aluminum-containing antacid
absorption in man. Eur. J. Clin. Chem. Clin. Biochem. 32:1 19-121.
Ondreicka, R.,E. Ginter, and J. Kortus. 1966. Chi'onic toxicity of aluminum
in rats and mice and its effects on phosphorus metabolism. Br. J. Ind.
Med. 23:305-312.
Ondreicka, R., J. Kortus, and E. Ginter. 1971. Aluminum, its absorption,
distribution and effects on phosphorus metabolism. Pp. 293—305 in In-
testinal Absorption of Metal Ions, Trace Elements and Radionuclides,
S. C. Skoryna and D. Waldron-Edward, eds. Oxford: Pergamon.
Oteiza, P. I., C. L. Keen, B. Han, and M. S. Golub. 1993. Aluminum accu-
mulation and neurotoxicity in Swiss- Webster mice after long-term di-
etary exposure to aluminum and citrate. Metabolism Clin. Exper.
42:1296-1300.
Owen, L. M. W., H. M. Crews, N. J. Bishop, and R. C. Massey. 1994.
Aluminum uptake from some foods by guinea pigs and the characteriza-
tion of aluminum in in vivo intestinal digesta by SEC-ICP-MS. Food
Chem. Toxicol. 32:697-705.
Pennington, J. A. T., and J. W. Jones. 1989. Dietary intake of aluminum.
Pp. 67-100 in Aluminum and Health: A Critical Review, H. J. Gitelman,
ed. New York: Marcel Dekker.
Peuranen, S., M. Keinanen, C. Tigerstedt, and P. J. Vuorinen. 2003. Effects
of temperature on the recovery of juvenile grayling (Thymallus
thymallus) from exposure to Al-hFe. Aquatic Toxicol. 65:73-84.
Plunkert, P. A. 2002. Aluminum. In U.S. Geological Survey Minerals Year-
book. Available at http://minerals.usgs.gov/minerals/pubs/commodity/
aluminum/. Accessed December 29, 2003.
Powell, J. J. and R. P. H. Thompson. 1993. The chemistry of aluminum in
the gastrointestinal lumen and its uptake and absorption. Proc. Nutr.
Soc. 52:241-253.
Powell, J. J., S. M. Greenfield, H. G. Parkes, J. K. Nicholson, and R. P. H.
Thompson. 1993. Gastro-intestinal availability of aluminum from tea.
Food Chem. Toxicol. 31:449^54.
Pratico, D., K. Uryu, S. Sung, S. Tang, J. Q. Trojanowski, and V. M. Lee.
2002. Aluminum modulates brain amyloidosis through oxidative stress
APP transgenic mice. FASEB J. 16:1138-1140.
Priest, N. D., D. Newton, J. P. Day, R. J. Talbot, and A. J. Warner. 1995.
Human metabolism of aluminum- 26 and gallium-67 injected as citrates.
Human Exp. Toxicol. 14:287-293.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
26
MINERAL TOLERANCE OF ANIMALS
Provan, S. D., and R. A. Yokel. 1988a. Influence of calcium on aluminum
accumulation by the rat jejunal slice. Res. Commun. Chem. Pathol.
Pharmacol. 59:79-92.
Provan, S. P., and R. A. Yokel. 1988b. Aluminum uptake by the in situ rat
preparation. J. Pharmacol. Exp. Ther. 245:928-931.
Quarles, L. D., H. J. Gitelman, and M. K. Drezner. 1985. Induction of de
novo bone formation in the beagle. J. Clin. Invest. 81:1056-1066.
Quartley, B., G. Esselmont, A. Taylor, and M. Dobrota. 1993. Effect of oral
aluminum citrate on short-term tissue distribution of aluminum. Food
Chem. Toxicol. 31:543-548.
Rosa, I. v., P. R. Henry, and C. B. Ammerman. 1982. Interrelationship of
dietary phosphorus, aluminum and iron on performance and tissue min-
eral composition in lambs. J. Anim. Sci. 55:1231—1240.
Said, A. N., P. Slagsvold, H. Bergh, and B. Laksesvela. 1977. High fluoride
water to wether sheep maintained in pens: aluminum chloride as a pos-
sible aUeviator of fluorosis. Nord. Vet. Med. 29:172-180.
Savory, J., and M. R. Wills. 1988. Analytical techniques for the analysis of
aluminum. Pp. 1—24 in Aluminum and Health: A Critical Review, H. J.
Gitelman, ed. New York: Marcel Dekker.
Savory, J., C. Exley, W. F. Forbes, Y. Huang, J. G. Joshi, T. Kruck, D. R. C.
McLachlan, and I. Wakayama. 1996. Can the controversy of the role of
aluminum in Alzheimer's be resolved? What are the suggested ap-
proaches to this controversy and methodological issues to be consid-
ered? J. Toxicol. Environ. Health 48:615-635.
Schlettwein-Gsell, D., and S. Mommsen-Straub. 1973. Aluminium. Int. Z.
Vitamin Ern. Forschung. 43:251-263.
Schijnholzer, K. W., R. A. L. Sutton, V. R. Walker, V. Sossi, M. Schulzer,
C. Orvig, E. Venczel, R. R. Johnson, D. Vetterli, B. Dittrich-Hannen, P.
Kubik, and M. Sutter. 1997. Intestinal absorption of trace amounts of
aluminum in rats studied with ^^ aluminum and accelerator mass spec-
trometry. Clin. Sci. 92:379-383.
Schroeder, H. A., and M. Mitchener. 1975. Life-term studies in rats: effects
of aluminum, barium, beryllium, and tungsten. J. Nutr. 105:421^27.
SchUtze, K., E. Hentschel, P. Happonen, and J. Akkila. 1995. Sucralfate
effervescent tablet: treatment of peptic ulcer disease and change in se-
rum aluminum concentration. Hepato-Gastroenterol. 42:240-245.
Skalsky, M. L., andR. A. Carchman. 1983. Aluminum homeostasis in man.
J. Am. Coll. Toxicol. 2:405-423.
Slanina, P., Y. Falkeborn, W. Freeh, and A. Cedergren. 1984. Aluminum
concentrations in the brain and bone of rats fed citric acid, aluminum
citrate or aluminum hydroxide. Food Chem. Toxicol. 22:391-397.
Slanina, P., W. Freeh, A. Bernhardson, A. Cedergren, and D. Mattsson.
1985. Influence of dietary factors on aluminum absorption and retention
in the brain and bone of rats. Acta Pharmacol. Toxicol. 56:331-336.
Slanina, P., W. Freeh, L. G. Ekstrom, L. Loof, S. Slorach, and A. Cedergren.
1986. Dietary citric acid enhances absorption of aluminum in antacids.
Clin. Chem. 32:539-541.
Sorenson, J. R. J., I. R. Campbell, L. B. Tepper. and R. D. Long. 1974.
Aluminum in the environment and human health. Environ. Health
Perspect. 8:3-95.
Spencer, H., L. Kramer, C. Norris, and E. Wiatrowski. 1981. Effect of alu-
minum hydroxide on plasma fluoride and fluoride secretion during a
high fluoride intake in men. Toxicol. Appl. Pharmacol. 56:140—144.
Sternweis, P. C, and A. G. Gilman. 1982. Aluminum: a requirement for
activation of the regulatory component of adenylate cyclase by fluoride.
Proc. Natl. Acad. Sci. USA 79:4888-4891.
Storer, N. L., and T. S. Nelson. 1968. The effect of various aluminum com-
pounds on chick performance. Poult. Sci. 47:244—247.
Strong, M. J., R. M. Garruto, J. G. Joshi, W. R. Mundy, and T. J. Shafer.
1996. Can the mechanisms of aluminum neurotoxicity be integrated
into a unified scheme? J. Toxicol. Environ. Health 48:599-613.
Sutherland, J. E., and J. L. Greger. 1998. Effect of the size of an oral dose of
aluminum on the relative importance of biliary v. urinary aluminum
excretion in conscious rats. Food Chem. Toxicol. 36:505-512.
Sutherland, J. E., G. M. Radzanowski, and J. L. Greger. 1996. Bile is an
important route of elimination of ingested aluminum by conscious male
Sprague-Dawley rats. Toxicol. 109:101-109.
Valdivia, R., C. B. Ammerman, C. J. Wilcox, and P. R. Henry. 1978. Effect
of dietary aluminum on animal performance and tissue mineral levels in
growing steers. J. Anim. Sci. 47:1351-1356.
Valdivia, R., C. B. Ammerman, P. R. Henry, J. P. Feaster, and C. J. Wilcox.
1982. Effect of dietary aluminum and phosphorus on performance, phos-
phorus utilization and tissue mineral composition in sheep. J. Anim.
Sci. 55:402-410.
van der Voet, G. B. 1992. Intestinal absorption of aluminum. Pp. 107-1 17
in Aluminum in Biology and Medicine. Ciba. Found. Symp. 169.
Chichester, UK: John Wiley and Sons.
van der Voet, G. B., and F. A. de Wolff. 1987. The effect of di- and trivalent
iron on the intestinal absorption of aluminum in rats. Toxicol. Appl.
Pharmacol. 90:190-197.
Versieck, U., and R. Cornells. 1980. Measuring aluminum levels. N. Engl.
J. Med. 302:468.
Wills, M. R., C. D. Hewitt, J. Savory, andM. N. Herman. 1993. Long-term
oral aluminum administration in rabbits, II. Brain and other organs. Ann.
Clin. Lab. Sci. 23:17-23.
Wisniewski. H. M., J. A. Sturman, and J. W. Shek. 1980. Aluminum chlo-
ride induced neurofibrillary changes in the developing rabbit: a chronic
animal model. Annals Neurol. 8:479-490.
Wisser L. A. A., B. S. Heim-ichs, and R. M. Leach. 1990. Effect of alumi-
num on performance and mineral metabolism in young chicks and lay-
ing hens. J. Nutr. 120:493^98.
Xu, Z. X., S. M. Pai, and S. I. Melethil. 1991. Kinetics of aluminum in rats.
II. Dose dependent urinary and biliary excretion. J. Pharm. Sci. 80:
946-951.
Yasui, M., I. Yano, Y. Yase, and K. Ota. 1990. Distribution of magnesium
in central nervous system tissue, trabecular and cortical bone in rats fed
with unbalanced diets of minerals. J. Neurol. Sci. 99:177-183.
Yasui, M., Y. Yase, K. Ota, andR. M. Garruto. 1991. Evaluation of magne-
sium, calcium and aluminum metabolism in rats and monkeys main-
tained on calcium-deficient diets. Neurotoxicol. 12:603—614.
Yokel, R. A., and P. J. McNamara. 1988. Influence of renal impairment,
chemical form, and serum protein binding in intravenous and oral alu-
minum kinetics in the rabbit. Toxicol. Appl. Pharmacol. 95:32^3.
Yokel R. A., S. S. Rhineheimer, R. D. Brauer, P. Sharma, D. Elmore, and P.
J. McNamara. 2001. Aluminum bioavailability from drinking water is
very low and is not appreciably influenced by stomach contents or wa-
ter hardness. Toxicol. 161:93-101.
Copyright © National Academy of Sciences. All rights reserved.
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29
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30
MINERAL TOLERANCE OF ANIMALS
TABLE 3-2 Aluminum Concentrations in Fluids and Tissues of Animals (mg/kg)
Species
Quantity"
Source
Duration
Route Tissue Concentrations (mg/kg)''
Reference
Humans
Humans
Rats
Cliicisens
Steers
Sheep
Uniinown
5 mg/d
125 mg/d
Unknown
Unknown
Al lactate
Lifetime Diet All tissues; 1^ (dry weight)
20 d Diet Serum: 4 ng/L
20 d Diet Serum: 7 ng/L
11
1,005
160
1,500
3,000
210
510
810
1,410
168
2,168
Unknown
Al hydroxide
with and without
citrate
Unknown
Al sulfate
Al sulfate
Unknown
Al chloride
Al chloride
Al chloride
Unknown
Al chloride
6-7 mo
6—7 mo
17 wk
17 wk
17 wk
84 d
84d
84 d
84d
56 d
56 d
Diet
Diet
Diet
Diet
Diet
Diet
Diet
Diet
Diet
Diet
Diet
Liver: <0.3; muscle: <0.4;
bone: <0.8
Liver: <0.3; muscle: <0.7;
bone: 1-1.4
Bone: <2 (di-y weight)
Bone: 6 (dry weight)
Bone: 10 (dry weight)
Soft tissues: 4—8 (dry weight)
Soft tissues: 4—8 (dry weight)
Soft tissues: 5—10 (dry weight)
Soft tissues: 5— ll(dry weight)
Soft tissues: 2—5 (dry weight)
Soft tissues: 4—6 (dry weight)
Alfrey, 1986
Greger and Baier, 1983b
Mice
25
Unknown
=50 d
Diet
Liver: 0.01; bone: 3
Donald et al., 1989
500
Al lactate
«50d
Diet
Liver: 0.03; bone: 5
1,000
Al lactate
=50 d
Diet
Liver: 0.05; bone: 6
Ecelbarger and Greger,
1994b
Wisser et al., 1990
Valdivia et al., 1978
Valdivia et al, 1982
"Quantity of exposure reported as mg/kg diet of aluminum unless noted otherwise.
''Concentrations reported as mg/kg wet tissue unless noted otherwise.
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Arsenic
INTRODUCTION
Arsenic (As) is a solid, brittle metalloid and thus has both
metallic and nonmetallic properties. The most common
stable form of arsenic at room temperature is metallic or
gray arsenic. Another form of elemental arsenic, yellow ar-
senic, occurs when arsenic vapors are cooled suddenly to
below 0°C (Stoeppler, 2004). It is unstable and more volatile
than gray arsenic. Arsenic is the 20th most common element
in the Earth's crust with an average natural abundance of
about 1.5-3 mg/kg (Mandal and Suzuki, 2002). Arsenic natu-
rally occurs in over 200 different forms with approximately
60 percent as arsenates, 20 percent as sulfides and sulfur-
salts, and the remainder as arsenides, arsenites, oxides, sili-
cates, and the elemental form (Mandal and Suzuki, 2002).
The most common arsenic mineral is arsenopyrite. Other
common minerals of arsenic are orpiment and realgar
(natural sulfides) and arsenolite. However, arsenic in its most
recoverable form is found in various types of metalliferous
minerals (Mandal and Suzuki, 2002) such as iron pyrite,
galena, chalcopyrite, and sphalerite. Arsenic trioxide
(AsjOj), the common commercial form of arsenic, is pro-
duced as a by-product of roasting various ores.
For more than 50 years, chromated copper arsenate
(CCA) has been the main preservative for wood products
used outdoors. In response to consumer concerns about ar-
senic toxicity, a voluntary phase-out of CCA-treated wood
for certain residential uses, such as play structures, picnic
tables, decks, and fencing, was to be completed before 2004.
Industrial-use wood products, such as marine pilings, utility
poles, roofing shakes, and shingles, still can be treated with
CCA. Because of reduced use of CCA, the demand for ar-
senic, as AsjOj, has markedly dropped. Still, about 90 per-
cent of arsenic trioxide produced is used to make CCA. The
balance of arsenic trioxide is mainly used in agricultural
chemicals such as insecticides, herbicides, and coccidiostats.
Uses of other arsenic compounds and metallic arsenic in-
clude electronics, pigments, metal alloys, and as a bubble
dispersant or decoloring agent in glassmaking (Brooks,
2002).
Arsenic exists predominantly in nature as an oxyanion
with an oxidation state of either 3"*" or S"*", but arsenic also
forms compounds where it has an oxidation state of 3"
(Hindmarsh et al., 2002). Arsenic binds covalently with
most metals and nonmetals, and forms stable organic com-
pounds. In animals, arsenic occurs mainly as inorganic
arsenate [0=As(0H)3; H2ASO4I-;
arsenite [OH-As(OH)2; H2ASO3
HASO42-;
ASO43-]
and
1 • HAsO,--; AsO 3],
'3 ' ^='-'3
and in the methylated form, mainly dimethylarsinic acid
[(CH3)2AsO(OH)] and monomethylarsonic acid
[CH3AsO(OH2)]. The major arsenic species in fish, crusta-
ceans, and mollusks apparently have the tetraalkylarsonium
structure (R4AS"'"), and in marine algae and bivalves the ma-
jor arsenic species have the trialkylarsine oxide structure
(R3ASO) (McSheehy et al., 2003). Thus, arsenobetaine
[(CH3)3As+CH2-COO-] and arsenocholine [(CH3)3As+CH2-
CH,-OH] are found in sea animals and arsenosugars are
found in marine algae and seaweeds.
ESSENTIALITY
Arsenic is generally not accepted as an essential nutrient
for higher animals. However, the large number of responses
to apparent arsenic deprivation (e.g., <12 |Jg/kg diet for rats
and chicks; <35 |Jg/kg diet for goats) reported for a variety of
animal species by more than one research group suggests
that it may have an essential or beneficial function in ultra
trace amounts (Anke, 1986; Uthus, 1994; Nielsen, 1998). In
the goat, pig and rat, the most consistent signs of apparent
arsenic deprivation have been depressed growth and abnor-
mal reproduction characterized by impaired fertility and in-
creased perinatal mortality. Other notable signs include de-
pressed serum triglyceride concentrations and death with
myocardial damage during lactation in goats (Anke, 1986),
and depressed hepatic S-adenosylmethionine and elevated
S-adenosylhomocysteine in rats and hamsters (Uthus, 1994).
31
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32
MINERAL TOLERANCE OF ANIMALS
Many of the responses of experimental animals to arsenic
deprivation and other in vitro or cell culture findings suggest
that arsenic affects the utilization of labile methyl groups
arising from methionine in higher animals. Thus, arsenic
may affect the methylation of metabolically or genetically
important molecules, whose functions are dependent on or
influenced by methyl incorporation. It has been suggested
that rats and chicks have an arsenic requirement that is
greater than 12 but less than 50 |Jg/kg diet (Nielsen, 1998).
In vitro findings suggest that arsenic also has an essential
or beneficial action in low amounts. For example. Snow et
al. (2001) found that sub-toxic arsenite induces a multi-com-
ponent protective response against oxidative stress in cul-
tured human keratinocytes and fibroblasts.
Some forms of arsenic have beneficial effects in
supranutritional amounts. Some organic arsenicals, because
of their antibiotic and anticoccidial properties, were used
extensively in the past as growth promoters for swine and
poultry (Anderson, 1983); this use has been largely sup-
planted by newer antibiotics. However, roxarsone (3-nitro-
4-hydroxyphenylarsonic acid; CgHgAsNOg) is still used ex-
tensively in the feed of broiler poultry to control coccidial
intestinal parasites, improve feed efficiency, and promote
rapid growth. Also, melarsoprol {2-[4-[(4,6-diamino-l,3,5-
triazin-2-yl)amino]phenyl]-l,3,2dithiarsolane-4-methanol;
CpHijAsNgOSj} is still used to treat trypanosomiasis in hu-
mans. High doses of arsenic trioxide recently have been
found to be an effective treatment for acute promyelocytic
leukemia through apototic, not necrotic, mechanisms (Chen
et al., 2001). Arsenic trioxide also apparently is an effective
treatment for other malignancies including megakaryocytic
leukemia (Tallman, 2001) and lymphoma (Dai et al., 1999).
Organic arsenicals such as melarsomine dihydrochloride
given by intramuscular or intravenous injection are used to
treat heartworm infection in dogs.
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
The most common methods for determining total arsenic
in biological samples after decomposition to mineral ash in
solution are hydride atomic absorption spectrometry (AAS),
inductively coupled plasma mass spectrometry, and graphite
furnace AAS (Stoeppler, 2004). However, the silver
diethyldithiocarbamate colorimetric method, which results
in a very stable red color, is still in use to determine total
arsenic, after conversion into arsine, in polluted ground wa-
ter (Tareq et al., 2003). Converting biological samples to ash
that can be solubilized has been accomplished by a number
of different methods including dry ashing, wet or micro-
wave-assisted ashing with acid mixtures, or ashing with ni-
tric acid alone in open and closed (often pressurized) sys-
tems (Stoeppler, 2004). An optimal sample decomposition
method that avoids loss of analyte is high-pressure ashing.
This method uses concentrated nitric acid in closed quartz
vessels at temperatures up to 320° C (Wijrfels, 1989; Knapp,
1990). A microwave-assisted procedure attaining >300° C
also has been found to result in complete sample decomposi-
tion (Goessler and Pavkov, 2003). Complete decomposition
is of utmost importance when the hydride AAS method of
analysis is used because traces of organic compounds inter-
fere with the analysis.
Because of the widely varying toxicities of different ar-
senic species, the development of analytical methods to de-
termine the chemical forms of arsenic and their concentra-
tions in biological and environmental samples have become
of interest. Collection of samples for arsenic speciation must
be done with care and kept at a low temperature to prevent
the modification of arsenic species by contaminating bacteria
or inherent biological activity of the sample. The methods
used to determine arsenic species require an extraction step.
Tissues with high fat content may need to be defatted with a
solvent, such as ether or acetone, before the extraction of
arsenic. Most arsenic species in biological tissues are water
soluble and thus can be extracted with water alone or with a
mixture of water and methanol (McSheehy et al., 2003). Af-
ter extraction, arsenic species are determined by a combina-
tion of separation techniques such as high-performance liq-
uid chromatography and capillary zone electrophoresis, and
detection techniques that are specific and highly sensitive for
arsenic such as inductively-coupled plasma mass spectrom-
etry and electrospray mass spectrometry with tandem mass
spectrometry (McSheehy et al., 2003). The difficulties en-
countered in the determination of arsenic species in biologi-
cal samples have been reviewed (McSheehy et al., 2003) and
include incomplete extraction, retention time irrepro-
ducibility, co-elution of species, presence of unidentified spe-
cies, the lack of standards, and detection interference. An
example of arsenic species detennination in the domestic ani-
mal situation is that of Pavkov and Goessler (200 1), who iden-
tified and quantified organoarsenic compounds in finishing
chicken feed and chicken litter.
REGULATION AND METABOLISM
Absorption and Metabolism
There apparently are two components to the absorption of
arsenic (Fullmer and Wasserman, 1985). Initially, arsenate
becomes sequestered primarily in or on the mucosal tissue.
Eventually the sites of sequestration become filled, with con-
comitant movement down a concentration gradient into the
body. In rats, some forms of organic arsenic are absorbed at
rates directly proportional to their intestinal concentration
over a 100-fold range (Hwang and Schanker, 1973). This
finding suggests that organic arsenicals are absorbed mainly
by simple diffusion. The absorption and metabolism of ar-
senic may be influenced by intestinal bacteria that can me-
thylate arsenic or metabolize methylated arsenic (Hall et al.,
1997; Kurodaetal., 2001).
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ARSENIC
33
Once absorbed, inorganic arsenic is transferred to various
tissues including thie liver and testis where arsenic is methy-
lated with S-adenosylmethionine as the methyl donor (Healy
et al., 1999). Before arsenate is methylated, it is reduced to
arsenite; this reduction is facilitated by glutathione (Vahter,
1994). The conversion of arsenate into arsenite may also be
accomplished in the animal gastrointestinal tract by bacteria
with arsenate reductase activity (Herbel et al., 2002). Arsen-
ite methyltransferase methylates arsenite to form mono-
methylarsonic acid, which is then reduced to monomethyl-
arsonous acid [CH3As(OH)2]. Monomethylarsonous acid, a
relatively toxic form of arsenic, is rapidly methylated by a
methyltransferase to form dimethylarsinic acid; in humans,
monomethylarsonous acid is found in the urine only when
excessive inorganic arsenic is consumed (Aposhian et al.,
2001). Dimethylarsinic acid can be reduced to dimethyl-
arsinous acid [(CH3)2AsOH], which is a relatively toxic form
of arsenic. However, the formation of dimethylarsinic acid
usually is the final step in the metabolism of arsenic in hu-
mans and most animals, and thus is the major form of ar-
senic in urine. Inorganic and methyl arsenic compounds ap-
parently are protein-bound when they are substrates for
enzymatic biomethylation (Styblo and Thomas, 1997). Preg-
nancy increases arsenic methylation, especially late in gesta-
tion; dimethylarsinic acid is the main form of arsenic trans-
ferred to the fetus (Vahter et al., 2000). In addition to the
methylated forms, inorganic arsenic bound to transferrin is
found in plasma (Zhang et al., 1998). Trimethylated organic
forms of arsenic stay trimethylated after absorption. Arseno-
betaine passes through the body into urine without biotrans-
formation. Some orally ingested arsenocholine appears in
the urine, and some can be incorporated into body phospho-
lipids in a manner similar to choline; however, most is trans-
formed into arsenobetaine before being excreted in the urine.
Absorbed tetramethylarsonium also is not biotransformed
before excretion (Yoshida et al., 1998). Unlike arsenobetaine
and tetramethylarsonium, arsenosugars are transformed to
many different arsenic species after absorption. Francesconi
et al. (2002) found at least 12 arsenic metabolites in the urine
of humans after they ingested an oral dose of a synthetic
arsenosugar. The metabolism of arsenic in some animal spe-
cies is quite unusual. For example, unlike other mammals,
rats concentrate arsenic in their erythrocytes. Chimpanzees,
marmosets, squirrel monkeys, tamarins, and guinea pigs are
unable to methylate arsenic. These species apparently have
other mechanisms for facilitating arsenic excretion (Vahter,
1994; Healy et al., 1999; Vahter et al., 2000).
Excretion of ingested arsenic is rapid, principally in the
urine. In some species, significant amounts of arsenic are
excreted in the bile in association with glutathione (Vahter,
1994; Kala et al., 2000). The usual proportions of the forms
of arsenic in human urine are about 20 percent inorganic
arsenic, 15 percent monomethylarsonic acid, and 65 percent
dimethylarsinic acid (Vahter et al., 2000). The proportions
are quite different, however, with consumption of organic
arsenic in forms found in seafood (mostly trimethylated ar-
senic, e.g., arsenobetaine). For example, the urine of Japa-
nese students who consumed high amounts of organic ar-
senic in seafood contained 9.4 percent inorganic arsenic, 3.0
percent monomethylarsonic acid, 28.9 percent dimethyl-
arsinic acid, and 58.2 percent trimethylated arsenic com-
pounds (Yamato, 1988).
Metabolic Interactions
Both arsenic deprivation and toxicity are influenced or
affected by factors that change labile methyl metabolism.
Generally, factors that reduce the availability of labile me-
thyl groups exacerbate arsenic deprivation and toxicity. For
example, methionine or choline deficiency, excessive dietary
arginine, and dietary guanidoacetic acid supplementation
enhanced the response to arsenic deprivation in chicks and
rats (Uthus, 2003). Treatment with periodate-oxidized ad-
enosine, a methylation inhibitor, exacerbated the toxic ef-
fects of inorganic arsenic on development in mice (Lammon
et al., 2003). Arsenic toxicity is also influenced by factors
that affect reactive oxygen metabolism. For example, ascor-
bic acid and a-tocopherol alleviated arsenic toxicosis signs
in rats of lipid peroxidation and enzyme inhibition in mito-
chondria of rats fed 100 mg As/L drinking water as sodium
arsenite (Ramanathan et al., 2003). Other nutrient deficien-
cies that can affect arsenic toxicity or deficiency through
affecting labile methyl or oxidative metabolism include cys-
teine (Siewicki and Leffel, 1980; Czarnecki et al., 1984),
folic acid (McDorman et al., 2002), pyridoxine (Uthus and
Poellot, 1991-1992), and zinc (Uthus, 1994).
A well-established metabolic interaction is the multifac-
eted and complex interaction between arsenic and selenium.
Both methylation and oxidation could be involved in the in-
teraction, possibly through competition for the methyl do-
nor, S-adenosylmethionine, and competition for the antioxi-
dant, glutathione (Kenyon et al., 2001). Interaction at the
level of methylation is plausible because arsenite inhibits
selenium methylation both in vivo and in vitro, and selenium
is a potent inhibitor of arsenic methylation in vitro (Kenyon
et al., 2001). However, most findings indicate that selenium
deficiency (not excess) exacerbates arsenic toxicity and im-
pairs arsenic metabolism. Also, supplementing with arsenic
as arsenite or arsenate alleviates the toxicity of most forms
of selenium (e.g., selenate, selenite, selenocysteine, seleno-
methionine) (Levander, 1977), and selenium supplementa-
tion as sodium selenate apparently can alleviate the toxicity
of arsenic as arsenate (Biswas et al., 1999). These actions are
opposite of those expected if there was a competition for
factors involved in the metabolism and excretion of methy-
lated arsenic and selenium. Possible mechanisms for the ap-
parent dichotomy involve metabolism and distribution an-
tagonism and effects on oxidative metabolism. Levander
(1977) suggested that arsenic enhances the biliary excretion
of selenium via the formation of a detoxification conjugate.
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34
MINERAL TOLERANCE OF ANIMALS
The identification of tlie seleno-bis(S-glutatfiionyl) arsinium
ion in tfie bile of rabbits injected with selenite followed by
arsenite (Gailer et al., 2000) supports this suggestion. Also,
arsenic and selenium can combine directly to form AsjSe,
which becomes concentrated and precipitated in renal lyso-
somes (Berry and Galle, 1994). The oxidative metabolism
suggestion is based on selenium, in the form of seleno-
cysteine, being a critical component of several enzymes that
maintain intracellular redox balance, including thioredoxin
reductase and glutathione peroxidase. Selenium deficiency
would decrease the antioxidant capacity to antagonize the
oxidative stress induced by excessive arsenic, and thus exac-
erbate arsenic toxicity (Kenyon et al., 2001).
Another established interaction is between arsenic and
copper. Pharmacologic or toxicological amounts of arsenic
50 mg/kg diet as sodium arsenate and 100 mg/kg diet as
sodium arsenite induce copper accumulation in the kidney
of rats (Mahaffey et al., 1981; Uthus, 2001; Yu and Beynen,
2001), chicks (100 mg roxarsone/kg diet) (Czarnecki and
Baker, 1985), and guinea pigs, but not in mice (100 mg/kg
diet as sodium arsenate) (Hunder et al., 1999). High dietary
arsenic does not increase liver copper, but may slightly re-
duce it (Yu and Beyen, 2001). High dietary arsenic decreases
plasma copper concentrations (Yu and Beynen, 2001;
Schmolke et al., 1992). High dietary arsenic also exacer-
bates copper deficiency in rats (Uthus, 2001), and high di-
etary roxarsone (3-nitro-4-hydroxyphenylarsonic acid) en-
hances copper toxicity in pigs (Edmonds and Baker, 1986).
On the other hand, low-dose roxarsone administration ap-
parently ameliorates copper toxicity (Edmonds and Baker,
1986). The mechanism through which arsenic affects copper
distribution in the body has not been established. However,
Yu and Beynen (2001) suggested that arsenic toxicosis de-
creases the excretion of copper through the predominant site
of excretion, the bile, by reducing hepatic copper. Biliary
copper excretion is detennined by the copper concentration
in liver. As a result of the change in biliary excretion, copper
is directed to the renal cortex where it accumulates.
Mechanisms of Toxicity
As indicated above, three mechanisms of action through
which arsenic may be toxic are oxidative stress, altered me-
thylation, and altered metabolism of other essential miner-
als. Oxidative stress and altered methylation are the bases
for arsenic being categorized as a human carcinogen
(Kitchin, 2001; Thomas et al., 2001; Hughes, 2002). Other
mechanisms of toxicity are more specific to pentavalent and
trivalent forms of arsenic. Arsenate apparently can replace
phosphate in some biochemical reactions because they have
similar structure and properties (Hughes, 2002). This re-
placement uncouples oxidative phosphorylation and thus can
result in the depletion of adenosine triphosphate (ATP).
However, the toxicity of arsenate may be mainly the result
of its conversion into arsenite. Trivalent arsenic (e.g., arsen-
ite) readily binds with thiols and vicinal sulfhydryls that are
specific functional groups within enzymes, receptors, and
co-enzymes (Thomas et al., 2001; Hughes, 2002). This bind-
ing can result in the inhibition of critical biochemical func-
tions or reactions. It should be noted, however, that the bind-
ing of arsenite at nonessential sites in proteins may be a
detoxification mechanism (Aposhian, 1989).
SOURCES AND BIOAVAILABILITY
Sea plant and fish products and supplemental minerals
supply most of the arsenic found in animal feeds. The con-
centration of arsenic has been found to range between 1 and
180 mg/kg dry weight for various marine macro algae, <2
and 170 mg/kg fresh weight in marine fish and bivalves, and
<0. 1 and 3 mg/kg fresh weight for freshwater fish (Stoeppler,
2004). The arsenic content of commercial fishmeals used for
livestock was found to range between 2.9 and 9.1 mg/kg dry
weight (Lunde, 1968). Most arsenic in fish and algae is in
the relatively nontoxic organic form (e.g., arsenobetaine,
arsenosugars). Grains have measurable amounts of arsenic;
reported mean concentrations (in |Jg/kg fresh weight) include
oats, 189; barley, 67; and wheat, 45 (Wiersma et al., 1986).
Grass species contain about 100 |Jg/kg dry weight (Stoeppler,
2004). Grass from areas close to industrial sites, or grown on
high-arsenic soils, can be markedly higher (up to 62 mg/kg
dry weight near a lead smelter) (Woolson, 1983). Some of
the arsenic in plants growing near mining and smelting op-
erations comes from aerial deposition, but much comes from
root uptake (Woolson, 1983). Straw from rice grown in a
greenhouse in pots flooded with water containing 8 mg As/L
accumulated about 100 mg As/kg, mostly in the inorganic
form (Abedin et al., 2002). Interestingly, arsenic increased
only slightly in the rice grain (from 0.15 mg/kg to 0.42 mg/
kg) with the arsenic treatment, and thus did not exceed the
food hygiene limit of 1 mg/kg. Sheep and cattle do not find
arsenic distasteful and actually may develop a taste for it
(Clarke and Clarke, 1975). Ruminants apparently will graze
selectively on contaminated forage. The arsenic content in
muscle of terrestrial animals (e.g., cattle, swine, and poultry)
is generally below 20 |Jg/kg fresh weight (Michels, 1986).
Drinking water can be a major source of arsenic, especially
in the inorganic form. Arsenic concentrations in unpolluted
fresh waters, mainly as arsenate, generally range between 1-
10 |Jg/L. However, the arsenic content can be much higher in
waters in some geochemical environments. These include
aquifers under strongly reducing conditions; aquifers under
oxidizing, high-pH (>8) conditions; areas of sulfide mineral-
ization and mining; and geothermal areas (Smedley et al.,
2001). Waters that may be used for drinking purposes have
been found to be as high as 0.1-5 mg As/L (Smedley et al.,
2001; Mandal and Suzuki, 2002).
The bioavailability of inorganic arsenic from the gas-
trointestinal tract correlates well with the solubility of the
compound ingested (Vahter, 1983; Marafante and Vahter,
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ARSENIC
35
1987). In humans and most laboratory animals, >90 percent
of inorganic arsenate and arsenite in a water solution is ab-
sorbed. However, only 20-30 percent of arsenic in arsenic
trioxide and lead arsenate, which are only slightly soluble in
water, is absorbed by hamsters, rats, and rabbits. In a dog
study, the bioavailability, or the amount absorbed, of inor-
ganic arsenic from bog ore-containing soil was found to be
only 8.3 percent (Groen et al., 1994). Other studies found
similar low bioavailability of soil arsenic. Rabbits absorbed
24 percent and cynomolgus monkeys absorbed 19 percent of
the arsenic in soils near smelters (Freeman et al., 1993,
1995). About 60-75 percent of inorganic arsenic ingested
with food is absorbed by humans (Hopenhayn-Rich et al.,
1993).
The form of organic arsenic also determines it
bioavailability. When orally dosed, >90 percent of arseno-
betaine was recovered in the urine of hamsters; 70-80 per-
cent of arsenocholine was recovered in the urine of mice,
rats, and rabbits; and 45 percent of dimethylarsinic acid was
recovered in the urine of hamsters (Marafante et al., 1984;
Yamauchi and Yamamura, 1984; Yamauchi et al., 1986). In
contrast, >90 percent of an oral dose of sodium-/?-N-
glycolylarsenilate was recovered in the feces of rats or hu-
mans within 3 days of administration; urinary excretion ac-
counted for only 4-5 percent of the dose (McChesney et al.,
1962). The bioavailability of organic arsenic as found in fish
is highly available. Rats absorbed 98-99 percent of the ar-
senic in flounder (Siewicki and Sydlowski, 1981), and hu-
mans absorbed 66-86 percent of arsenic in fish cakes and
flounder (Freeman et al., 1979; Tam et al., 1982). The
bioavailability of arsenosugars as found in seaweeds has not
been well established. Shiomi (1994) found that in mice,
orally administered partially purified arsenosugars from the
red alga Porphyra yezoensis were excreted mainly through
the feces; this suggests that the arsenosugars were not very
bioavailable. In contrast, Francesconi et al. (2002) found that
80 percent of an orally administered synthetic arsenosugar
to humans was excreted in the urine within 4 days. Further
evidence that arsenosugars in seaweed are absorbed and
metabolized is that sheep living largely on seaweed have
elevated wool, blood, and urinary arsenic concentrations and
no arsenosugars in the urine (Feldmann, 2000).
TOXICOSIS
Considering its reputation as a poison, it may be surpris-
ing to some individuals that arsenic has a low order of toxic-
ity, especially when it is in the pentavalent oxidation state.
The ratio of the toxic to the apparent nutritional dose of inor-
ganic arsenic for rats is near 1,250 (Nielsen, 1996). The le-
thal dose in domestic animals ranges from 1 to 25 mg/kg
body weight as sodium arsenite, which is 3-fold to 10-fold
more toxic than arsenic trioxide (Stoeppler, 2004). Some
forms of organic arsenic, particularly those found in sea-
food, are virtually nontoxic; for example, a 10 g/kg BW dose
of arsenobetaine depressed spontaneous motility and respi-
ration in male mice, but these signs disappeared within one
hour (Kaise et al., 1985). Arsenocholine is slightly more
toxic than arsenobetaine; a dose of 5.8 g/kg BW caused death
in some rats, but a dose of 4.8 g/kg BW did not (Kaise et al.,
1992).
Acute
The acute toxicity of arsenic is determined by its chemi-
cal form and oxidation state. Generally, the acute toxicity of
trivalent arsenic is greater than pentavalent arsenic (Thomas
et al., 2001). Most pentavalent organic arsenic species are
relatively nontoxic. In contrast, some organic forms of triva-
lent arsenic (e.g., monomethylarsonous acid) are more toxic
than inorganic arsenite, and the toxicity of some others (e.g.,
dimethylarsinous acid) is similar to inorganic arsenite (Tho-
mas et al., 2001; Hughes, 2002). As a result, providing one
LDjg value for arsenic cannot be done. This is demonstrated
by the reported LDjq for various forms of arsenic in mice (in
mg As/kg body weight): arsenic trioxide, 26; mono-
methyarsonic acid, 916; dimethylarsinc acid, 648; tri-
methylarsine oxide, 5,500; arsenocholine, 6,500; and
arsenobetaine, >4,260 (Kaise et al., 1985, 1989, 1992). The
reported LD^q of arsenic trioxide for the rat is 15 mg/kg body
weight (Harrison et al., 1958). The lethal range of inorganic
arsenic (i.e., arsenic trioxide) for humans has been estimated
to be 1-3 mg/kg body weight (Ellenhorn, 1997). The signs
of acute arsenic toxicosis include intense abdominal pain,
vomiting, diarrhea, weakness, staggering gait, hypothermia,
and death (Stoeppler, 2004).
Fish also have a fairly high tolerance to arsenic in their
environment. In a study testing seven fish species, the 96-hr
LCjQ values ranged from 13.3 mg/L for rainbow trout to 41.5
mg/L for bluegill (National Research Council of Canada,
1978). The LCjq values for tilapia were determined to be (in
mg/L pond water) at 24 hr, 69; 48 hr, 51; 72 hr, 38; and 96
hr, 28 (Liao et al., 2003).
Chronic
Chronic oral arsenic toxicosis in domestic animals is sel-
dom reported. The reason for this may be the fact that ar-
senic is relatively nontoxic to domestic animals. For ex-
ample, sheep chronically consuming about 35 mg daily in
the form of seaweed (mostly dimethylated arsenoribosides)
exhibited no abnormalities or signs of arsenic toxicosis
(Hansen et al., 2002). The fatal dose of arsanilic acid for
horses and cows was reported to be 40 mg/kg BW and 6-12
mg/kg BW for sheep. Horses and cattle ingested 2.66 to 4
mg arsanilic acid per kg BW daily for 18 months without
any discernible injury (Reeves, 1925). The National Toxi-
cology Program (1989) reported no significant toxic effects
in mice fed 200 mg roxarsone (57 mg As)/kg diet for two
years. Table 4-1 summarizes some reported doses that cause
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36
MINERAL TOLERANCE OF ANIMALS
arsenic toxicosis and thie effects of chronic consumption of
these high amounts of arsenic by various animals. Signs of
chronic arsenic intoxication usually reported were depressed
growth, feed efficiency, feed intake, and, for some species,
convulsions, uncoordinated gait, and decreased hemoglobin.
Chronic high exposure to arsenic can induce numerous bio-
chemical changes. For example, in rats and guinea pigs,
dosing the drinking water with 10 or 25 mg of As^+/L for 16
weeks resulted in reduced blood 5-amino-levulinic acid
dehydratase activity, increased urinary 5-aminolevulinic
acid, and significant changes in whole-brain concentrations
of neurotransmitters, 5-hydroxytryptamine, dopamine, and
norepinephrine (Kannan et al., 2001). In humans, chronic
exposure to arsenic has been associated with various fonns
of cancer (Wang et al., 2002). Animal models showing that
arsenic promotes or induces cancer have been difficult to
establish; special strains of experimental rodents, non-oral
routes of administration, and stressors such as a carcinogen
generally have to be employed (Wang et al., 2002). Because
arsenic carcinogenicity apparently is not an issue for domes-
tic animals, it will not be reviewed here.
Prenatal death, malformation, and inhibition of growth
can result from exposure to arsenite, arsenate, dimethyl-
arsinate, and monomethylarsonate in hamsters, mice, and
rats (Hood, 1983). Such effects generally are seen only at
doses causing maternal toxicity including death. To induce
malformation in animals, the arsenic typically has to be ad-
ministered intraperitoneally or intravenously rather than
orally (Hood, 1983; Thomas et al., 2001; DeSesso, 2001). A
few studies have shown that extremely high single oral doses
of inorganic arsenic (40-125 mg/kg BW as sodium arsenate)
will cause some fetal stunting and malformations (Hood,
1983). Male mice fed 40 mg As/L of drinking water as so-
dium arsenite for 35 days exhibited decreased sperm count
and motility and increased abnormal sperm; no effect was
seen at 20 mg/L (Pant et al., 2001). Published reproductive
findings do not appear practically relevant; thus, reproduc-
tive toxicity of arsenic under natural conditions is unlikely.
Factors Influencing Toxicity
In addition to those indicated in the metabolic interac-
tions section, other factors that may affect arsenic toxicity
include vitamin Bjj status (Zakharyan and Aposhian, 1999)
and nutritional factors affecting the 5'-adenosylmethionine-
mediated transmethylation/transulfuration pathway, includ-
ing niacin, riboflavin, folate, and iron (Donohue and
Abernathy, 2001). Age, sex, and pregnancy apparently af-
fect arsenic toxicity. Vahter et al. (2000) reported findings
indicating that children are more sensitive to arsenic toxicity
than adults, and that pregnancy may increase the ability to
metabolize or detoxify arsenic. Even when not pregnant,
women may be less susceptible to arsenic toxicity. Dose
level, ethnicity, and genetic polymorphism also are factors
influencing arsenic toxicity (Vahter et al., 2000).
TISSUE LEVELS
If the ingestion of arsenic is low, no tissue significantly
accumulates arsenic; most tissues contain less than 50 |-ig/kg
wet weight. However, high intakes of arsenic can markedly
increase the arsenic content of tissues; this is indicated by
the data in Table 4-2. Arsenic is widely distributed in the
body with the highest amounts in skin, hair, and nails, prob-
ably the result of arsenite binding to SH groups of proteins
such as keratin that are relatively plentiful in these tissue.
Organs highest in arsenic are kidney and liver; these organs
also accumulate the highest amount of arsenic when exces-
sive amounts are ingested (see Table 4-2). Although tissue
arsenic can be increased to relatively high amounts in sea-
food (e.g., shrimp) and fish, the toxicity of the organic forms
of arsenic found in the edible parts of these animals is essen-
tially nontoxic. Even with high intakes of arsenic, the data in
Table 4-2 suggest that no domestic animal tissue, except
perhaps liver and kidney, used as a food will contain enough
arsenic to be of toxicological concern for humans.
MAXIMUM TOLERABLE LEVELS
The highest dietary level at which arsenic has no adverse
effect, and the lowest level that induces toxicosis, varies with
species. The data in Table 4-1 indicate that, in the inorganic
form, 50 mg As/kg diet is toxic to rats and 100 mg As/kg diet
is toxic to chicks; other animals are apparently more tolerant
to inorganic arsenic. Pigs fed roxarsone may be the best indi-
cator of a species sensitive to organic arsenic; 187.5 mg/kg
diet of roxarsone (53.4 mg As/kg) was toxic to pigs (Rice et
al., 1985; Kennedy et al., 1986). The preceding indicates
that the maximum tolerable levels set for domestic animals
in the previous edition of this book (NRC, 1980) of 50 mg/
kg diet for inorganic arsenic and 100 mg/kg diet for organic
arsenic may be too high. Because a 12.5 mg As/kg diet ap-
parently is not toxic to rats (Hisanaga, 1982), a more appro-
priate maximum tolerable limit for arsenic would be between
12.5 and 50 mg/kg diet; the midpoint, or 30 mg/kg diet, may
be a reasonable maximum tolerable level for domestic ani-
mals. Based on the data in Table 4-1, fish are less tolerant to
dietary inorganic arsenic than mammals; diets as low as 10
mg As/kg induced toxicosis in rainbow trout. Thus, a maxi-
mum tolerable level for inorganic arsenic of 30 mg/kg diet
for fish is inappropriate. A maximum tolerable limit for fish
may be in the range of 5 mg As/kg diet.
The European Communities (2002) issued a directive that
set the maximum arsenic contents allowable in products in-
tended for animal feed with a moisture content of 12 percent
at much lower levels than 30 mg/kg diet. The scientific basis
for setting these low values was not given in the directive.
The level set for animal feeds was 2 mg/kg, with the excep-
tion of meals made from grass, dried lucerne, dried clover,
dried sugar beet pulp, and dried molasses sugar beet pulp
(set at 4 mg/kg), as well as phosphates and feedstuffs ob-
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ARSENIC
37
tained from the processing of fish or other marine animals
(set at 10 mg/kg). The maximum for complete feedstuffs for
fish was set at 4 mg/kg, which is near the maximum toler-
able limit of 5 mg/kg suggested above. The maximum for
complementary feedstuffs for fish was set at 4 mg/kg with
the exception of complementary mineral feedstuffs (set at 12
mg/kg).
HUMAN HEALTH
Generally, in human health, arsenic is considered only as
a toxicant and it is classified as a carcinogen. Thus, recent
efforts have been directed towards decreasing the ingestion
of arsenic, particularly through drinking water. Under the
authority of the Safe Drinking Water Act, the U.S. Environ-
mental Protection Agency (EPA) in 200 1 reduced the drink-
ing water standard from 50 |-ig/L to 10 |ig/L; public water
systems have until January 2006 to comply (Brooks, 2002).
There are epidemiological findings showing that some can-
cer is correlated with markedly decreased serum arsenic con-
centrations (Mayer et al., 1993). Also, it has been noted that
the incidence of some forms of cancer were higher when
drinking water contained very low amounts of arsenic than
when it contained reasonable amounts of arsenic (Guo et al.,
1995). These findings are consistent with the report that an
exposure to drinking water containing 20 to 50 |-ig/L appar-
ently does not affect mortality (Buchet and Lison, 1998).
Biochemical evidence suggesting that low dietary arsenic
can increase cancer susceptibility includes the finding that
low and excessive amounts of arsenic, compared to control
amounts, significantly decreased global methylation of DNA
in cultured Caco-2 cells (Davis et al., 2000). DNA hypo-
methylation is associated with some types of cancer (Dizik
et al., 199 1 ; Zapisek et al., 1992). This finding, in addition to
those described in the essentiality and metabolic interactions
sections above, suggests that an inadequate arsenic status
may cause hypomethylation because of a depressed methy-
lation function and excessive arsenic may cause hypo-
methylation through an increased need for methyl groups for
its elimination, and thus making less available for DNA me-
thylation. In both cases, the hypomethylation could result in
an increased susceptibility to cancer.
FUTURE RESEARCH NEEDS
Although the toxicity of arsenic, especially its carcino-
genic properties, for humans has been extensively studied,
there are some research needs. Establishing the basis for
the apparent essential or beneficial action of arsenic, and
the intake below which this action is compromised, would
be helpful in setting the lower limits of toxicity standards
for arsenic. Mechanisms through which the various forms
of arsenic are absorbed need to established. Speciation of
arsenic found in animal feedstuffs would help in determin-
ing the toxicity potential of those containing relatively high
amounts of arsenic. The toxicity of arsenic to some domes-
tic animals (e.g., cattle, goats) need to be better defined.
The basis for the apparent difference in arsenic toxicity for
humans (cancer, heart disease, diabetes, etc., thought to oc-
cur at relatively low intakes) and domestic animals (lim-
ited signs of toxicosis at relatively high intakes) should be
determined.
SUMMARY
Arsenic is widely distributed in the biosphere and exists
predominantly as an oxyanion in an oxidation state of 3+ or
5+. In animals, arsenic occurs mainly as inorganic arsenate
or arsenite, monmethylarsonic acid, and dimethylarsinic
acid. The major form of arsenic in sea animals is arseno-
betaine. In seaweeds, arsenic is found in arsenosugars. Ar-
senic generally is not accepted as an essential element, but
studies with goats, chicks, hamsters, and rats suggest that it
may have an essential or a beneficial function in ultra trace
amounts (micrograms per kg diet). Some organic arsenicals
(e.g., roxarsone) are still used for antibiotic or anti-coccidial
purposes in poultry. Arsenic trioxide has been found to be an
effective treatment for some forms of cancer in humans.
Soluble inorganic arsenic and organic arsenic as found in sea
foods are highly absorbed and excreted mainly in the urine.
Most inorganic arsenic is enzymatically methylated before
being excreted. Arsensobetaine is not, but arsenosugars are
transformed before being excreted. Sea plant and fish prod-
ucts are sources of arsenic for animal feeds; this arsenic is
relatively nontoxic. Contaminated drinking water and foli-
age are major sources of inorganic arsenic. Mechanisms
through which arsenic may be toxic are altered methyl me-
tabolism, oxidative stress, altered metabolism of other es-
sential minerals, replacement of phosphate in biochemical
reactions, and inhibition of critical biochemical functions by
binding thiols and vicinal sulfhydryls. Arsenic is relatively
nontoxic to domestic animals. The toxic dietary concentra-
tions of arsenic are generally between 500 and 1,000 times
greater than the concentrations normally found in animal
feeds. Signs of chronic arsenic intoxication include de-
pressed growth, feed intake, feed efficiency, and, for some
species, convulsions, uncoordinated gait, and decreased he-
moglobin. The suggested maximum tolerable level for do-
mestic animals is 30 mg/kg diet. The suggested maximum
tolerable level for fish is 5 mg/kg diet. Thus, except for lo-
calized areas where arsenic is extremely high in drinking
water, major arsenic contamination by mining and smelting
industries has occurred, or old arsenic pesticides or ashes of
CCA lumber are accessible, arsenic toxicosis is not a con-
cern for domestic animals.
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38
MINERAL TOLERANCE OF ANIMALS
REFERENCES
Abedin, M. J., M. S. Cresser, A. A. Meharg, J. Feldman, and J. Cotter-
Howells. 2002. Arsenic accumulation and metabolism in rice (Oryza
sativa L). Environ. Sci. Technol. 36:962— 968.
Anderson, C. E. 1983. Arsenicals as feed additives for poultry and swine.
Pp. 89—98 in Arsenic: Industrial., Biomedical., Environmental Perspec-
tives, W.H. Lederer and R.J. Fensterheim, eds. New York: Van Nostrand
Reinhold.
Anke, M. 1986. Ai'senic. Pp. 347-372 in Trace Elements in Human and
Animal Nutrition, Vol. 2, W. Mertz, ed. Orlando, FL: Academic Press.
Anke, M., M. Seifert, L. Angelow, G. Thomas, C. Drobner, M. Miiller, M.
Glei, H. Freytag, W. Arnhold, G. Kiihne, C. Rother, U. Kreuter, and S.
Holzinger. 1996. The biological importance of arsenic — toxicity, essen-
tiality, intake of adults in Germany. Pp. 103—120 in New Perspectives in
the Research of Hardly Known Trace Elements and Their Role in Life
Processes, I. Pais, ed. Budapest: University of Horticulture and Food
Industry.
Aposhian, H. V. 1989. Biochemical toxicology of arsenic. Pp. 265-299 in
Reviews in Biochemical Toxicology, E. Hodgson, J. R. Bend, and
R. M. Philpot, eds. New York: Elsevier.
Aposhian, H. V., E. S. Gurzau, C. Le, A. Gurzau, R. A. Zakharyan, W. R.
Cullen, S. M. Healy, D. Gonzalez-Ramirez, D. L. Morgan, A. Sampayo-
Reyes, E. Wildfang, T. R. Radabaugh, J. S. Petrick, E. A. Mash, Jr., R.
B. Aavula, and M. M. Apsohian. 2001. The discovery, importance and
significance of monomethylarsonous acid (MMA'^') in urine of humans
exposed to inorganic arsenic. Pp. 305—313 in Arsenic Exposure and
Health Effects IV, W. R. Chappell, C. O. Abernathy , and R. L. Calderon,
eds. Oxford: Elsevier Science.
Benes, B., and V. Bencko. 1981. Content of lipids and esterfied fatty acids
in the liver of mice exposed to arsenic in drinking water. J. Hyg.
Epidemol. Microbiol. Immunol. 25:384-392.
Berry, J. P., and P. Galle. 1994. Selenium-arsenic interaction in renal cells:
role of lysosomes. Electron microprobe study. J. Submicrosc. Cytol.
Pathol. 26:203-210.
Biswas, S., G. Talukder, and A. Sharma. 1999. Prevention of cytotoxic
effects of arsenic by short-term dietary supplementation with selenium
in mice in vivo. Mutat. Res. 441:155-160.
Brooks, W. E. 2002. Arsenic. Pp. 7. 1-7.3 in U.S. Geological Survey Miner-
als Yearbook. Available at http://minerals.usgs.gov/minerals/pubs/
commodity/arsenic/. Accessed on April 2, 2005.
Buchet, J. P., and D. Lison. 1998. Mortality by cancer in groups of the
Belgian population with a moderately increased intake of arsenic. Int.
Arch. Occup. Environ. Health 71:125-130.
Bucy, L. L., U. S. Garrigus, R. M. Forbes, H. W. Norton, and W. W. Moore.
1955. Toxicity of some arsenicals fed to growing-fattening lambs. J.
Anim. Sci. 14:435^145.
Carmignani, M., P. Boscolo, and N. Castellino. 1985. Metabolic fate and
cardiovascular effects of arsenic in rats and rabbits chronically exposed
to trivalent and pentavalent arsenic. Arch. Toxicol., Suppl. 8:452^55.
Chen, Z., G. Q. Chen, Z. X. Shen, S. J. Chen, and Z. Y. Wang. 2001. Treat-
ment of acute promyelocytic leukemia with arsenic compounds: in vitro
and in vivo studies. Semin. Hematol. 38:26-36.
Clarke, E. G. C, and M. L. Clarke. 1975. P. 477 in Veterinary Toxicology,
3rd edition. Baltimore, MD: Williams & Wilkins.
Cockell, K. A., and J. W. Hilton. 1988. Preliminary investigations on the
comparative chronic toxicity of four dietary arsenicals to juvenile rain-
bow trout (Salmo gairdneri R.). Aquatic Toxicol. 12:73-82.
Cockell, K. A., J. W. Hilton, and W. J. Bettger. 1991. Chronic toxicity of
dietary disodium arsenate heptahydrate to juvenile rainbow trout
(Oncorhynchus mykiss). Arch. Environ. Contam. Toxicol. 21:518-527.
Czarnecki, G. L., and D. H. Baker. 1985. Reduction in liver copper concen-
tration by the organic arsenical, 3-nitro-4-hyrdroxyphenylarsonic acid.
J. Anim. Sci. 60:440^50.
Czarnecki, G. L., D. H. Baker, and J. E. Garst. 1984. Arsenic-sulfur amino
acid interactions in the chick. J. Anim. Sci. 59:1573-1581.
Dai, J., R. S. Weinberg, S. Waxman, and Y. Jing. 1999. Malignant cells can
be sensitized to undergo growth inhibition and apoptosis by arsenic tri-
oxide through modulation of the glutathione redox system. Blood
93:268-277.
Dang, H. S., D. D. Jaiswal., and S. Somasundaram. 1983. Distribution of
arsenic in human tissues and milk. Sci. Total Environ. 29:171-175.
Davis, C. D., E. O. Uthus, and J. W. Finley. 2000. Dietary selenium and
arsenic affect DNA methylation in vitro in Caco-2 cells and in vivo in
rat liver and colon. J. Nutr. 130:2903-2909.
DeSesso, J. M. 2001. Teratogen update: inorganic arsenic. Teratology
63:170-173.
Dickinson, J. O. 1972. Toxicity of the arsenical herbicide monosodium acid
methanearsonate in cattle. Am. J. Vet. Res. 33:1889-1892.
Dizik, M., J. K. Christman, andE. Wainfan. 1991. Alternatives in expres-
sion and methylation of specific genes in livers of rats fed a cancer
promoting methyl-deficient diet. Carcinogenesis 12:1307-1312.
Donohue, J. M., andC. O. Abernathy. 2001. Arsenic methylation and the 5-
adenosylmethionine-mediated transmethylation/transsulfuration path-
way. Pp. 367-379 in Arsenic Exposure and Health Effects IV, W. R.
Chappell, C. O. Abernathy, and R. L. Calderon, eds. Oxford: Elsevier
Science.
Edmonds, M. S., and D. H. Baker. 1986. Toxic effects of supplemental
copper and roxarsone when fed alone or in combination to young pigs.
J. Anim. Sci. 63:533-537.
EUenhorn, M. J. 1997. P. 1540 in EUenhorn's Medical Toxicology: Diagno-
sis and Treatment of Human Poisoning, 2nd ed. Baltimore, MD: Will-
iams & Wilkins.
European Communities. 2002. Directive 2002/32/EC of the European Par-
liament and the Council. Off. J. European Comm. L140/I0-L140/21.
Feldman, J. 2000. Metabolism of arsenic from seaweed by man and ani-
mals. Pp. 165-168 in Trace Elements in Man and Animals 10, A. M.
Roussel, R. A. Anderson, and A. E. Favier, eds. New York: Kluwer
Academic/Plenum Publishers.
Francesconi, K. A., R. Tanggaard, C. J. McKenzie, and W. Goessler. 2002.
Arsenic metabolites in human urine after ingestion of an arsenosugar.
Clin. Chem. 48:92-101.
Freeman, H. C, J. F. Uthe, R. B. Fleming, P. J. Odense, R. G. Ackman, G.
Landry, and C. Musial. 1979. Clearance of arsenic ingested by man
from arsenic contaminated fish. Bull. Environ. Contam. Toxicol.
22:224-229.
Freeman, G. B., J. D. Johnson, J. M. Killinger, S. C. Liao, A. O. Davis, M.
V. Ruby, R. I. Chaney, S. C. Lovre, and P. D. Bergstrom. 1993.
Bioavailability of arsenic in soil impacted by smelter activities follow-
ing oral administration in rabbits. Fundam. Appl. Toxicol. 21:83-88.
Freeman, G. B., R. A. Schoof, M. V. Ruby, A. O. Davis, J. A. Dill, S. C.
Liao, C. A. Lapin, and P. D. Bergstrom. 1995. Bioavailability of arsenic
in soil and house dust impacted by smelter activities following oral
administration in cynomolgus monkeys. Fundam. Appl. Toxicol.
28:215-222.
Fullmer, C. S., andR. H. Wasserman. 1985. Intestinal absorption of arsen-
ate in the chick. Environ. Res. 36:206—217.
Gailer, J., G. N. George, I. J. Pickering, R. C. Prince, S. C. Ringwald, J. E.
Pemberton, R. S. Glass, H. S. Younis, D. W. DeYoung, and V. H. Aposhian.
2000. A metabolic link between arsenite and selenite: the seleno-bis(S-
glutathionyl) ai'sinium ion. J. Am. Chem. Soc. 19:4637—4639.
Goessler, W., and M. Pavkov. 2003. Accurate quantification and transfor-
mation of arsenic compounds during wet ashing with nitric acid and
microwave assisted heating. Analyst 128:796-802.
Groen, K., H. A. M. G. Vaessen, J. J. G. Kliest, J. L. M. de Boer, T. van
Ooik, A. Timmerman, and R. F. Vlug. 1994. Bioavailability of inor-
ganic arsenite from bog ore-containing soil in the dog. Environ. Health
Perspect. 102:182-184.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
ARSENIC
39
Guo, H. R., S. R. Lipsitz, H. Hu, and R. R. Monson. 1995. Using ecological
data to estimate a regression model for individual data: the association
between arsenic in drinking water and incidence of skin cancer (a work-
ing copy of a presentation given in EUicott City, MD, May 31-June 2,
1995). In Arsenic Workshop — Health Effects Notebook. Denver, CO:
American Water Works Association Research Foundation.
Hall, L. L., S. E. George, M. J. Kohan, M. Styblo, and D. J. Thomas. 1997.
In vitro methylation of inorganic arsenic in mouse intestinal cecum.
Toxicol. Appl. Pharmacol. 147:101-109.
Hansen, H. R., A. Raab, and J. Feldmann. 2002. Uptake, biotransformation,
accumulation and excretion of arsenic by ruminants chronically exposed
to organoarsenicals. P. 51 (Abstract) in 11th International Symposium
on Trace Elements in Man and Animals Conference Schedule and Ab-
stracts. Berkeley, CA.
Harrison, J. W. E., E. W. Packman, and D. D. Abbott. 1958. Acute oral
toxicity and chemical and physical properties of arsenic trioxides.
A.M.A. Arch. Ind. Health 17:118-123.
Healy, S. M., E. Wildfang, R. A. Zakharyan, and A. V. Aposhian. 1999.
Diversity of inorganic arsenitie transformation. Biol. Trace Elem. Res.
68:249-266.
Herbel, M. J., J. S. Blum, S. E. Hoeft, S. M. Cohen, L. L. Arnold, J. Lisak,
J. F. Stolz, and R. S. Oremland. 2002. Dissimilatory arsenate reductase
activity and arsenate-respiring bacteria in bovine rumen fluid, hamster
feces, and the termite hindgut. FEMS Microbiol. Ecol. 41:59-67.
Hermayer, K. L., P. E. Stake, and R. L. Shippe. 1977. Evaluation of dietary
zinc, cadmium, tin, lead, bismuth and arsenic toxicity in hens. Poult.
Sci. 56:1721 (Abstr.).
Hindmarsh, J. T., C. O. Abernathy, G. R. Peters, and R. F. McCurdy. 2002.
Environmental aspects of arsenic toxicity. Pp. 217—229 in Heavy Met-
als in the Environment, B. Sarkar, ed. New York: Marcel Dekker.
Hisanaga, A. 1982. Chronic toxicity of arsenous acid in rats with special
reference to dose-response. Fukuoka Acta Med. 73:46-63.
Hoffman, D. J., C. J. Sanderson, L. J. LeCaptain, E. Cromartie, and G. W.
Pendleton. 1992. Interactive effects of arsenate, selenium, and dietary
protein on survival, growth, and physiology in mallard ducklings. Ai'ch.
Environ. Contam. Toxicol. 22:55-62.
Hood, R. D. 1983. Toxicology of prenatal exposure to arsenic. Pp. 134—
150 in Arsenic: Industrial, Biomedical, Environmental Perspectives,
W. H. Lederer and R. J. Fensterheim, eds. New York: Van Nostrand
Reinhold.
Hopenhayn-Rich, C, A. H. Smith, and H. M. Goeden. 1993. Human studies
do not support the methylation threshold hypothesis for the toxicity of
inorganic arsenic. Environ. Res. 60:161—177.
Hughes, M. F. 2002. Arsenic toxicity and potential mechanisms of action.
Toxicol. Lett. 133:1-16.
Hunder, G., J. Schaper, O. Admuyiwa, and B. Elsenhans. 1999. Species dif-
ferences in arsenic-mediated renal copper accumulation: a comparison
between rats, mice and guinea pigs. Hum. Exp. Toxicol. 18:699-705.
Hwang, S. W., and L. S. Schanker. 1973. Absorption of organic arsenical
compounds from the rat small intestine. Xenobiotica 3:351—355.
Kaise, T., S. Watanabe, and K. Itoh. 1985. The acute toxicity of arseno-
betaine. Chemosphere 14:1327-1332.
Kaise, T., H. Yamauchi, Y. Horiguchi, T. Tani, S. Watanabe, T. Hirayama,
and S. Fukui. 1989. A comparative study on acute toxicity of methyl-
arsonic acid, dimethylarsinic acid and trimethylene arsenic oxide in
mice. Appl. Organomet. Chem. 3:273-277.
Kaise, T., Y. Horiguchi, S. Fukui, K. Shiomi, M. Chino, and T. Kikuchi.
1992. Acute toxicity and metabolism of arsenocholine in mice. Appl.
Organomet. Chem. 6:369—373.
Kala, S. v., M. W. Neely, G. Kala, C. 1. Prater, D. W. Atwood, J. A. Rice,
and M. W. Lieberman. 2000. The MRP2/cMOAT transporter and ar-
senic-glutathione complex formation are required for biliary excretion
of arsenic. J. Biol. Chem. 275:33404-33408.
Kannan, G. M., N. Tripathi, S. N. Dube, M. Gupta, and S. J. Flora. 2001.
Toxic effects of arsenic (111) on some hematopoietic and central nervous
system variables in rats and guinea pigs. J. Toxicol. Clin. Toxicol.
39:675-682.
Kennedy, S., D. A. Rice, and P. F. Cush. 1986. Neuropathology of experi-
mental 3-nitro-4-hydroxyphenylarsonic acid toxicosis in pigs. Vet.
Pathol. 23:454-461.
Kenyon, E. M., M. F. Hughes, L. M. Del Razo, and O. A. Levander.
2001. The impact of selenium status on the metabolism and disposi-
tion of arsenic and its implications for epidemiologic investigations.
Pp. 315-323 in Arsenic Exposure and Health Effects IV, W. R.
Chappell, C. O. Abernathy, and R. L. Calderon, eds. Oxford: Elsevier
Science.
Kitchin, K. T. 2001. Recent advances in arsenic carcinogenesis: modes of
action, animal model systems, and methylated arsenic metabolites.
Toxicol. Appl. Pharmacol. 172:249-261.
Knapp, G. 1990. Mechanized methods of sample decomposition in trace
and ultra-trace analysis. Anal. Proc. 27:112-114.
Kuroda, K., K. Yoshida, A. Yasukawa, H. Wanibuchi, S. Fukushima, and
G. Endo. 2001. Enteric bacteria may play a role in mammalian arsenic
metabolism. Appl. Organometal. Chem. 15:548-552.
Lammon, C. A., X. C. Le, and R. D. Hood. 2003. Pretreatment with
periodate-oxidized adenosine enhances developmental toxicity of inor-
ganic arsenic in mice. Birth Defects Res. (Part B) 68:335—343.
Ledet, A. E., J. R. Duncan, W. B. Buck, and F. K. Ramsey. 1973. Clinical,
toxicological, and pathological aspects of arsanilic acid poisoning in
swine. Clin. Toxicol. 6:439^67.
Levander, O. A. 1977. Metabolic inteiTelationships between arsenic and
selenium. Environ. Health Perspect. 19:159—164.
Liao C. M., B. C. Chen, S. Singh, M. C. Lin, C. W. Liu, and B. C. Han.
2003. Acute toxicity and bioaccumulation of arsenic in tilapia
(Oreochromis mossambicus) from a blackfoot disease area in Taiwan.
Environ. Toxicol. 18:252-259.
Lunde, G. 1968. Activation analysis of trace elements in fishmeal. J. Sci.
Food Agric. 19:432^34.
Mahaffey, K. R., S. G. Capar, B. C. Gladen, and B. A. Fowler. 1981. Con-
current exposure to lead, cadmium, and arsenic: effects on toxicity and
tissue metal concentrations in the rat. J. Lab. Clin. Med. 98:463^81.
Mandal, B. K., and K. T. Suzuki. 2002. Arsenic round the world: a review.
Talanta 58:201-235.
Marafante, E., and M. Vahter. 1987. Solubility, retention, and metabolism
of intratracheally and orally administered inorganic arsenic compounds
in the hamster. Environ. Res. 42:72-82.
Marafante, E., M. Vahter, and L. Dencker. 1984. Metabolism of arseno-
choline in mice, rats and rabbits. Sci. Total Environ. 34:223-240.
Mayer, D. R., W. Kosmus, H. Pogglitsch, D. Mayer, and W. Beyer. 1993.
Essential trace elements in humans. Serum arsenic concentrations in
hemodialysis patients in comparison to healthy controls. Biol. Trace
Elem. Res. 37:27-38.
McChesney, E. W., J. O. Hoppe, P. McAuliff, and W. F. Banks, Jr. 1962.
Toxicity and physiological disposition of sodium p-N-
glycolylarsanilate. 1. Observations in mouse, cat, rat, and man. Toxicol.
Appl. Pharmacol. 4:14-23.
McDorman, E. W., B. W. Collins, and J. W. Allen. 2002. Dietary folate
deficiency enhances induction of micronuclei by arsenic in mice.
Environ. Mol. Mutagen. 40:71-77.
McSheehy, S., J. Szpunar, R. Morabito, and P. Quevauvillere. 2003. The
speciation of arsenic in biological tissues and the certification of refer-
ence materials for quality control. Trends Anal. Chem. 22:191-209.
Michels, S. 1986. Natural occurrence of arsenic in food (in German). Wiss.
Umw. 3^:118-122.
Morrison, L. L., and E. R. Chavez. 1983. Selenium-arsenic interaction in
the weanling pig. Can. J. Anim. Sci. 63:239-246.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
40
MINERAL TOLERANCE OF ANIMALS
NRC (National Research Council). 1977. Medical and Biologic Effects of
Environmental Pollutants; Arsenic. Washington, D.C.: National Acad-
emy Press.
NRC. 1980. Arsenic. Pp. 40-53 in Mineral Tolerance of Domestic Ani-
mals. Washington, D.C.: National Academy Press.
National Research Council of Canada. 1978. Effects of Arsenic in the Ca-
nadian Environment, Report NRCC 15391, Ottawa.
National Toxicology Program. 1989. NTP Toxicology and carcinogenesis
studies of roxarsone (CAS No. 121-19-7) in F344/N rats and B6C3F1
mice (feed studies). Natl. Toxicol. Program Tech. Rep. Ser. 345:1-198.
Neiger, R. D., and G. D. Osweiler. 1989. Effect of subacute low level di-
etary sodium arsenite on dogs. Fundam. Appl. Toxicol. 13:439^51.
Nielsen, F. H. 1996. Other trace elements. Pp. 353—377 in Present Knowl-
edge in Nutrition, 7th ed., E. E. Ziegler and L. J. Filer, Jr., eds. Washing-
ton, D.C.: ILSI Press.
Nielsen, F. H. 1998. Ultratrace elements in nutrition: cun'ent knowledge
and speculation. J. Trace Elem. Exp. Med. 1 1:251—274.
Oladimeji, A. A., S. U. Qadri, and A. S. W. deFreitas. 1984. Long-term
effects of arsenic accumulation in rainbow trout, Salmo gairdneri. Bull.
Environ. Contam. Toxicol. 32:732-741.
Pant, N., R. Kumar, R. C. Murthy, and S. P. Srivastava. 2001. Male repro-
ductive effect of arsenic in mice. Biometals 14:113—117.
Pavkov, M., and W. Goessler. 2001. Determination of organoarsenic com-
pounds in finishing chicken feed and chicken litter by HPLC-ICP-MS.
Pp. 125-134 in Arsenic Exposure and Health Effects IV, W. R.
Chappell, C. O. Abernathy, and R. L. Calderon, eds. Oxford: Elsevier
Science.
Pedlar, R. M., M. D. Ptashynski, R. Evans, and J. F. Klaverkamp. 2002.
Toxicological effects of dietary arsenic exposure in lake whitefish
(Coregonus clupeaformis). Aquatic Toxicol. 57:167-189.
Ramanathan, K., S. Shila, S. Kumaran, and C. Panneerselvam. 2003. Ascor-
bic acid and a-tocopherol as potent modulators on arsenic induced tox-
icity in mitochondria. J. Nutr. Biochem. 14:416^20.
Reeves, G. I. 1925. The arsenic poisoning of livestock. J. Econ. Entomol.
18:83-90.
Rice, D. A., S. Kennedy, C. H. McMurray, and W. J. Blanchflower. 1985.
Experimental 3-nitro-4-hydroxyphenylarsonic acid toxicosis in pigs.
Res. Vet. Sci. 39:47-51.
Santra, A., A. Maiti, S. Das, S. Lahiri, S. K. Charkaborty, and D. N.
Mazumder. 2000. Hepatic damage caused by chronic arsenic toxicity in
experimental animals. J. Toxicol. Clin. Toxicol. 38:395^05.
Schmolke, G., B. Elsenhans, C. Ehtechami, and W. Forth. 1992. Arsenic-cop-
per interaction in the kidney of the rat. Hum. Exp. Toxicol. 11:315-321.
Shiomi, K. 1994. Arsenic in marine organisms: chemical forms and toxico-
logical aspects. Pp. 261-282 in Ai'senic in the Environment, Part 11:
Human Health and Ecosystem Effects, J. O. Nriagu, ed. New York:
Wiley.
Siewicki, T. C, and E. C. Leffel. 1980. Effects of dietary cysteine on ar-
senic toxicity in the rat. Nutr. Rep. Int. 22:123-133.
Siewicki, T. C, and J. S. Sydlowski. 1981. Excretion of arsenic by rats fed
witch flounder or cacodylic acid. Nutr. Rep. Int. 24:121-127.
Smedley, P. L., D. G. Kinniburgh, I. Huq, L. Zhen-dong, and H. B. NicoUi.
200 1 . International perspective on naturally occurring arsenic problems
in groundwater. Pp. 9-25 in Arsenic Exposure and Health Effects IV,
W. R. Chappell, C. O. Abernathy, and R. L. Calderon, eds. Oxford:
Elsevier Science.
Snow, E. T., M. Schuliga, S. Chouchane, and Y.Hu. 2001. Sub-toxic arsen-
ite induces a multi-component protective response against oxidative
stress in human cells. Pp. 265-275 in Arsenic Exposure and Health
Effects IV, W. R. Chappell, C. O. Abernathy, and R. L. Calderon, eds.
Oxford: Elsevier Science.
Stibilj, v., A. Holcman, and M. Dermelj. 1997. Distribution of arsenic in
the tissues of laying hens fed a diet containing AsjO,. Pp. 195—196 in
Trace Elements in Man and Animals- 9: Proceedings of the Ninth Inter-
national Symposium on Trace Elements in Man and Animals, P. W. F.
Fischer, M. R. L'Abbe, K. A. Cockell, and R. S. Gibson, eds. Ottawa:
NRC Research Press.
Stoeppler, M. 2004. Arsenic. Pp. 1321-1364 in Elements and Their Com-
pounds in the Environment: Occurrence, Analysis and Biological Rel-
evance, 2nd ed.. Vol. 3, Nonmetals, Particular Aspects, E. Merian, M.
Anke, M. Ihnat, and M. Stoeppler, eds. Weinheim: Wiley- VCH.
Styblo M., and D. J. Thomas. 1997. Binding of arsenicals to proteins in an
in vitro methylation system. Toxicol. Appl. Pharmacol. 147:1-8.
Tallman, M. S. 2001. Arsenic trioxide: its role in acute promyelocytic leu-
kemia and potential in other hematologic malignancies. Blood Rev.
15:133-142.
Tam, G. K., S. M. Charbonneau, F. Bryce, and E. Sandi. 1982. Excretion of
a single oral dose of fish-arsenic in man. Bull. Environ. Contam.
Toxicol. 28:669-673.
Tareq, S. M., S. SafiuUah, H. M. Anawar, M. M. Rahman, and S. Ishizuka.
2003. Arsenic pollution in groundwater: a self-organizing complex
geochemical process in the deltaic sedimentary environment,
Bangladesh. Sci. Total Environ. 313:213-226.
Thomas, D. J., M. Styblo, and S. Lin. 2001. The cellular metabolism and
systemic toxicity of arsenic. Toxicol. Appl. Pharmacol. 176:127-144.
Uthus, E. O. 1994. Arsenic essentiality and factors affecting its importance.
Pp. 199-208 in Arsenic. Exposure and Health, W. R. Chappell, C. O.
Abernathy, and C. R. Cothern, eds. Northwood, UK: Science and Tech-
nology Letters.
Uthus, E. O. 200 1 . High dietary arsenic exacerbates copper deprivation in
rats. J. Trace Elem. Exp. Med. 14:43-55.
Uthus, E. O. 2003. Arsenic essentiality: a role affecting methionine metabo-
lism. J. Trace Elem. Exp. Med. 16:345-355.
Uthus, E. O., and R. Poellot. 1991-1992. Effect of dietary pyridoxine on
arsenic deprivation in rats. Magnesium Trace Elem. 10:339-347.
Vahter, M. 1983. Metabohsm of arsenic. Pp. 171-198 in Biological and
Environmental Effects of Arsenic, B. A. Fowler, ed. Amsterdam:
Elsevier.
Vahter, M. 1994. Species differences in the metabolism of arsenic. Pp. 171—
179 in Arsenic. Exposure and Health, W. R. Chappell, C. O. Abernathy,
and C. R. Cothern, eds. Northwood, UK: Science and Toxicology Letters.
Vahter, M., G. Concha, and B. Nermell. 2000. Factors influencing arsenic
methylation in humans. J. Trace Elem. Exp. Med. 13:173—184.
Valkonen, S., H. Savolainen, and J. Jarvisalo. 1983. Arsenic distribution
and neurochemical effects in peroral sodium arsenite exposure in rats.
Bull. Environ. Contam. Toxicol. 30:303-308.
Wang, J. P., L. Qi, M. R. Moore, and J. C. Ng. 2002. A review of animal
models for the study of arsenic carcinogenesis. Toxicol. Lett. 133:17—31.
Wiersma, D., B. J. van Goor, and N. G. van der Veen. 1986. Cadmium,
lead, mercury, and arsenic concentrations in crops and corresponding
soils in The Netherlands. J. Agric. Food Chem. 34:1067-1074.
Woolson, E. A. 1983. Emissions, cycling and effects of arsenic in soil eco-
systems. Pp. 51-139 in Biological and Environmental Effects of Ar-
senic, B. A. Fowler, ed. Amsterdam: Elsevier.
Wurfels, M. 1989. Voltammetric determination of metal traces in marine
samples after nitric acid decomposition. Marine Chem. 28:259-264.
Yamato, N. 1988. Concentrations and chemical species of arsenic in human
urine and hair. Bull. Environ. Contam. Toxicol. 40:633-640.
Yamauchi, H., and Y. Yamamura. 1983. Concentration and chemical
species of arsenic in human tissue. Bull. Environ. Contam. Toxicol.
31:267-270.
Yamauchi, H., and Y. Yamamura. 1984. Metabolism and excretion of orally
administered dimethylarsinic acid in the hamster. Toxicol. Appl.
Pharmacol. 74:134-140.
Yamauchi, H., T. Kaise, and Y. Yamamura. 1986. Metabolism and excre-
tion of orally administered arsenobetaine in the hamster. Bull. Environ.
Contam. Toxicol. 36:350-355.
Yoshida, K., Y. Inoue, K. Kuroda, H. Chen, H. Wanibuchi, S. Fukushima,
and G. Endo. 1998. Urinary excretion of arsenic metabolites after long-
term oral administration of various arsenic compounds to rats. J.
Toxicol. Environ. Health, Part A 54:179-192.
Yu, S., and A. C. Beynen. 2001. High arsenic intake raises kidney copper
and lowers plasma copper concentrations in rats. Biol. Trace Elem. Res.
81:63-70.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
ARSENIC 41
Zakharyan, R. A., and H. V. Aposhian. 1999. Arsenite methylation by Zhang, X., R. Cornelis, J. De Kimpe, J. Mees. and N. Lameire. 1998. Study
methylvitamin B p and glutathione does not require an enzyme. Toxicol. of arsenic-protein binding in serum of patients on continuous ambula-
Appl. Pharmacol. 154:287-291. tory peritoneal dialysis. Clin. Chem. 44:141-147.
Zapisek, W. F., G. M. Cronin, B. D. Lyn-Cook, and L. A. Poirier. 1992. The
onset of oncogene hypomethylation in the livers of rats fed methyl-
deficient amino acid-defined diets. Carcinogenesis 13:1869-1872.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
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Barium
INTRODUCTION
Barium (Ba) is a dense alkaline metal in Group IIA of the
periodic table and is the 16th most abundant element of the
Earth's crust, constituting about 0.04 percent of it. Barium
occurs as a divalent cation in combination with other ele-
ments and is chiefly found in underground ore deposits of
barite and witherite. Barite is predominantly BaSO^ and
witherite is predominantly BaCOj. Barite occurs in abun-
dance in Alaska, Arkansas, California, Georgia, Missouri,
Nevada, and Tennessee, as well as in Canada and Mexico
(USGS, 2000). Worldwide, China leads in barite ore mining
followed by the United States, with production predominat-
ing in Nevada and Georgia. BaS04 is used as raw material
for producing BaClj, BaOH, and other compounds.
The primary use of BaSO^ is by the oil and gas industries
as drilling muds. Additionally, barium compounds are used
to make ceramics, brake linings, paints, bricks, tiles, glass,
rubber, inks, adhesives, additives for fuels and oils, and ro-
denticides. Barium nitrite and sulfide are used in fireworks
and depilatories, respectively. Medically, BaS04is used as a
radiocontrast medium for x-rays of the gastrointestinal tract.
The natural forms of barium have poor water solubility:
0.001 g/L for BaS04 and 0.025 g/L for BaCOj. Commer-
cially produced salts are usually much more soluble in wa-
ter. For example, BaCU has a solubility of 375 g/L and con-
sequently exhibits a very different toxicological profile than
BaS04.
ESSENTIALITY
Barium is not considered as an essential nutrient for
plants or animals. The primary beneficial action attrib-
uted to barium is reduction of dental carries (Zdanowicz
et al., 1989). Several thorough reviews are available on
barium and its toxicological profile in human and envi-
ronmental health (ATSDR, 1992; NTP, 1994; EPA, 1998;
IPCS, 2001).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Total barium concentrations in water, feed, and tissues
can be determined by atomic absorption spectrophotometry
(AAS) after preparing samples by digestion with acid (Sharp
and Knevel, 1971; EPA, 1974). Graphite furnace AAS has
detection limits below one part per billion, but flame AAS is
sufficiently sensitive for biological samples that have toxic-
ity potential. Inductively coupled plasma-atomic emission
spectrometry is also a sensitive method for measuring barium
in biological samples; however there is potential for interfer-
ence from spectral bands from other compounds, such as
boric acid or sodium borate (IPCS, 2001). Standard tech-
niques for barium determination give total barium concen-
tration in the sample. However, measuring soluble barium
concentrations is more meaningful for toxicological evalua-
tion because the common but insoluble BaS04 form is rela-
tively nontoxic compared to soluble forms such as BaClj or
barium acetate. Unfortunately, standardized techniques for
extracting soluble compounds have yet to be developed.
REGULATION AND METABOLISM
Due to its insolubility, BaS04 is poorly absorbed from
the gastrointestinal tract. In chickens with free access to feed
and given a single oral dose of BaS04, 97.8 percent of the
dose was recovered from the feces within 48 hours (Vohra
and Kratzer, 1967). Healthy humans absorb a similarly small
proportion of BaS04 even when a high dose is given (Mauras
et al., 1983). A very wide range (0.7 to 85 percent) of ab-
sorption efficiencies of soluble barium compounds have been
reported in animals dosed orally, depending upon the chemi-
cal form, species, age, and fasting status of the animal. In
rats, young animals (22 days old) absorb about 10 times more
barium chloride than older animals. Consumption of barium
following fasting increases absorption by about 20 percent
(ATSDR, 1992; IPCS, 2001).
46
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BARIUM
47
Barium in blood is quickly transported into cells where it
blocks potassium channels and in some systems has Ca++
agonist properties. When barium is transported into muscle
cells, it blocks the exit of potassium, causes depolarization,
and stimulates muscle contraction. Barium can substitute for
calcium ions in stimulating nitric oxide production in the
endothelium of blood vessels and changes vascular tone
(Yamazaki et al., 1995). These effects on calcium and potas-
sium metabolism appear to mediate the toxic effects of
barium.
About 90 percent of total body barium is found in bone
and teeth. The efficiency of bone uptake of barium is 1.5 to
5 times higher than uptake of calcium or strontium (IPCS,
2001). Barium is primarily excreted in the feces after oral,
inhalation, or parenteral exposure. Bile is not an important
mechanism of excretion and other routes of loss into the in-
testines must be important in elimination of systemic barium
(Edel et al., 1991). In humans, sweat accounts for a greater
proportion of the daily loss than urine (Schroeder et al.,
1972). The biological half-time of BaClj in beagle dogs was
estimated to be 12.8 days (Cuddihy and Griffith, 1972).
SOURCES AND BIOAVAILABILITY
Barium is not typically supplemented to the diets of ani-
mals, and intake is due to background levels in feed ingredi-
ents and water. Some commercially available sources of cal-
cium phosphate used in animal production may have high
levels of barium (Fernandes et al., 1999), but levels of this
mineral are not typically monitored because of its low toxic-
ity profile. The form of barium in calcium phosphate sources
has not been determined, but would likely be present as
BaS04 and BaCOj.
Barium concentrations in surface waters are extremely
variable and depend on local geography, depth that the
sample was taken, and water hardness (NRC, 1977). Con-
centrations between 43 and 58 mg/L are typical in U.S. sur-
face waters although levels as high as 1,000 mg/L have been
reported. Water from deep rock and drift wells may have
barium levels that exceed 20 mg/L. Seawater contains be-
tween 0.02 and 25 mg/L depending upon the ocean, latitude,
and depth. High levels of barium in water are often due to
the presence of insoluble barium attached to suspended par-
ticles, which are typically removed during water purifica-
tion. Domestic drinking water supplies normally contain less
than 1 mg/L barium. In seawater, the limit of soluble barium
is about 1 mg/L because above this level BaS04 forms and
precipitates out of solution (Spangenberg and Cherr, 1996).
Barium levels in soils range from 50 to 3,000 mg/kg
(IPCS, 2001). Soils formed from limestone, feldspar, and
biotite are highest in barium, which is mostly in the barium
sulfate form. In general, the relationship between soil barium
level and plant barium level is not very strong, but the corre-
lation is greatly increased if soil levels are expressed as ex-
changeable barium (Robinson et al., 1950). An average
bioconcentration factor (BCF = barium in organism/barium
in soil) of 0.4 was found for a large variety of plant species
living at a site with a soil barium concentration of 104 mg/kg
(Hope et al., 1996). In the same environment, insects and
rodents had a BCF factor of 0.02. Wheat stalks, wheat grain,
corn grain, and alfalfa have BCFs of 0.31, 0.01, 0.03, and
0.93 of the extractable barium, respectively (Robinson et al.,
1950). Leaves from red ash {Fraxinus pennsylvanica), black
walnut (Juglans nigra), and hickory {Carya sp.) have BCFs
above 1.0. Brazil nuts from regions with high soil levels of
barium have the highest plant barium concentrations mea-
sured at 1,500 to 3,000 mg/kg (Smith, 1971).
Few studies have examined the bioavailability of barium
in foodstuffs or water. In one study, rats fed a diet containing
Brazil nuts supplying 249 mg/kg barium for 29 days had
bone barium levels that were 78 percent of control rats fed
an equal level of BaClj (Stoewsand et al., 1988). This sug-
gests that most of the barium in Brazil nuts is considerably
more bioavailable than BaS04. Nutritional bioavailability
tests have not been done for any other food or water source.
TOXICOSIS
The toxicity of barium is dependent upon its solubility.
Barium sulfate is practically insoluble and virtually nontoxic
so it has been used for decades in human and animal medi-
cine as a radiocontrast medium. Toxicity of more soluble
barium salts is due to their calcium agonist properties and
their ability to block potassium transport. Consequently,
therapy includes administration of calcium antagonists and
potassium. Other toxic mechanisms have not been found and
barium salts are not currently considered genotoxic, carcino-
genic, or teratogenic, though extensive research has yet to be
conducted (NTP, 1994; IPCS, 2001).
Single Dose
Barium sulfate is routinely dosed at up to 8 g/kg BW to
adult humans prior to gastrointestinal x-rays and is generally
considered safe. In humans, ingestion of soluble barium
compounds (e.g., BaClj) causes vomiting, diarrhea, abdomi-
nal pain, hypokalemia, cardiac arrhythmias, respiratory
weakness, renal failure, and skeletal muscle paralysis
(ATSDR, 1992; IPCS, 2001). In dogs, intravenous infusion
of BaClj causes salivation, diarrhea, hypertension, ventricu-
lar tachycardia, skeletal muscle paralysis, and, finally, respi-
ratory arrest and ventricular fibrillation (Roza and Berman,
1971). Potassium administration prevents all of these effects
except hypertension. In rats, a single gavage of 300 mg Ba/
kg BW as BaClj causes ocular discharge, fluid in the tra-
chea, darkened liver, and intestinal inflammation (Borzelleca
et al., 1988). The LDjq of BaClj in adult rats after a single
dose was 132 mg Ba/kg BW in one experiment, but about
twice this level in two other experiments (Table 5-1).
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MINERAL TOLERANCE OF ANIMALS
The relative toxicity of different soluble barium com-
pounds has received little attention. BaCOj is considerably
less soluble than BaClj, but is only slightly less toxic when
administered in water to rats (Schwartze, 1920). However,
toxicity of BaCOj is decreased considerably if it is provided
in alkaline bicarbonate buffer (McCauley and Washington,
1983) or in feed (Schwartze, 1920).
Acute
In a 10-day acute toxicity experiment using rats, daily
oral gavage of 209 mg Ba/kg BW as BaCl, in water did not
cause changes in body weight, tissue weights, histopathol-
ogy, or clinical chemistry except a decrease in blood urea
nitrogen (Borzelleca et al., 1988). Barium at 300 mg/kg BW
resulted in increased mortality in females, but not in males.
The acute LD^q of BaCOj in the diet of rats is about 10,000
mg/kg (Schwartze, 1920).
Chronic
Rats and mice given water with up to 1,318 mg/L of
barium as BaCU for 13 weeks were clinically, behaviorally,
and histopathologically normal, but those fed 2,636 mg/L
exhibited increased mortality (Dietz et al., 1992; NTP, 1994).
This indicates that the NOAEL of highly soluble barium
from BaClj in rodents is 1,318 mg/L, although a reanalysis
of the organ weight data suggest a NOAEL of 659 mg/L
(EPA, 1998). Similar results were found in a 2-year study in
rats and mice (NTP, 1994).
The primary clinical signs of chronic barium intake at high
levels are cardiomyopathies and hypertension that mimic the
effect of digitalis. Rats chronically exposed via the water to
100 mg/L of barium from BaClj for 1 month or 10 mg/L for 8
months develop a modest increase in systolic pressure (Perry
et al., 1989). The lower level did not have functional conse-
quences on the heart but 100 mg/L resulted in depressed rates
of cardiac contraction and electrical excitability. The kidney
is also sensitive to barium and very high levels of BaCL (2,636
mg Ba/L in water) cause nephrosis in rodents characterized by
tubular dilation and deposition of refractile crystals in the lu-
men of the tubules (Dietz et al., 1992).
Chronic toxicity studies using barium delivered in the diet
at toxic levels are not available. Rats fed diets containing
249 mg/kg of barium from BaClj or the same amount from
Brazil nuts did not cause observable effects (Stoewsand et
al., 1988), but a toxic level has not been established.
The toxicity of barium in livestock and poultry has re-
ceived little attention and the few studies that have been con-
ducted used insufficient dosage levels to establish a toxicity
threshold (Table 5-1). Similarly, aquatic systems have had
little study. The 30-day LCjg values for two species of cray-
fish {Austropotamobius pallipes pallipes and Orconectes
limosus) were 46 and 78 mg/L of barium as BaClj, respec-
tively (Boutet and Chaisemartin, 1973). Highly soluble
barium acetate interferes with calcification of the shell and
delayed development of marine mussel larvae (Mytilus
calif ornianus). Interestingly, this developmental defect was
observed only at levels between 200 and 800 |Jg/L because
additions of 1 mg/L and above caused precipitation of
BaS04, which apparently resulted in the formation of crystal
seeds that rapidly precipitated virtually all of the barium from
the seawater (Spangenberg and Cherr, 1996). Exposure of
unspecified species of marine fish, crustaceans, and mollusks
to drilling mud containing 7,500 mg/kg of barium as BaSO^
did not cause mortality (Daugherty, 1951).
Factors Influencing Toxicity
The toxicity of barium is dependent upon its solubility. It
has been hypothesized that insoluble BaSO^ can be solubi-
lized by the acid conditions of the stomach, especially if
given in unbuffered water to fasted animals (McCauley and
Washington, 1983). The water solubility of BaCOj and its
toxicity when dosed in buffered water depend on the pH.
Barium competes with calcium for uptake into bone, but
it is not clear if high dietary levels of calcium decrease the
toxicity of barium. Barium blocks potassium transport across
cell membranes, and potassium administration decreases
many of the signs of barium toxicosis (Roza and Berman,
1971).
TISSUE LEVELS
Barium is found predominantly in the bone and teeth,
where it substitutes for calcium. Muscle levels of barium are
below dietary levels regardless of the level or type of barium
salt consumed (Table 5-2), and bioaccumulation of barium
through the food chain is not expected to be a problem.
Barium levels in meat, milk, and eggs of poultry and live-
stock exposed to high levels of barium by diet or water have
not been determined. However levels in soft tissues (e.g.,
muscle, kidney, heart, liver) of rats fed high levels of BaClj
are low (<1 mg/kg fresh weight) (Perry et al., 1989; Tardiff
etal., 1980).
There has been concern that the buildup of barium in the
aquatic environment from use of oil drilling muds high in
BaS04 could result in high levels of barium in aquatic or-
ganisms harvested for human consumption. However,
barium in clams (Maritrix maritrix) collected from oil fields
in the Arabian Gulf averaged only 0.99 mg/kg wet weight
and the concentration was not significantly correlated with
the level in the sediment (Sadiq et al., 1990). Presumably,
this is because of the very low solubility of barium in seawa-
ter due to its high sulfate content.
MAXIMUM TOLERABLE LEVELS
The Maximum Tolerable Level (MTL) of barium is de-
fined as the dietary level that, when fed for a defined period
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BARIUM
49
of time, will not impair accepted indices of animal health or
performance. The MTL of barium is highly dependent upon
its chemical form, which is not known for most foodstuffs or
water supplies. The most common form in the environment,
BaS04, is very poorly absorbed and very high levels ( 1 g/kg
BW/d) in the diet or drinking water are tolerated by rodents
and humans. Soluble forms of barium, such as barium chlo-
ride, acetate, or nitrate have a much different toxicity pro-
file. In rats, the level at which BbCLt becomes toxic is simi-
lar for acute and chronic exposure. The cardiovascular
system is the most sensitive indicator of barium toxicosis in
rats, and modest but measurable functional changes occur at
barium levels of 100 mg/L water as BaCl, (Perry et al.,
1989). However giving 1,250 mg/L for 2 years does not re-
sult in observable pathology to any organ system (NTP,
1994). In rats and mice, organ pathology occurs at barium
levels of 2,500 mg/L. A dietary barium level of 249 mg/kg
diet from BaClj does not cause an observable effect on rats
(Stoewsand et al., 1988), but 218 mg/kg decreases the rate of
weight gain of chicks (Taucins et al., 1969). As BaClj does
not occur naturally in foods or water, these levels are most
applicable to barium arising from accidental contamination
of water or feed with soluble forms of barium. Estimates of
the bioavailability of intrinsic barium in feedstuffs and water
are needed in order to determine the MTL arising from nor-
mal dietary sources. Based on only one study in rats, a di-
etary barium level of 249 mg/kg diet from Brazil nuts does
not cause observable toxic effects (Stoewsand et al., 1988).
The NOAEL for barium salts or natural forms of barium is
not known for poultry or livestock but, based on rodent stud-
ies, it is unlikely that barium naturally found in feedstuffs
reaches sufficiently high levels to be toxic. Based primarily
on rodent studies, the MTL for poultry, swine, and horses is
set at 100 mg/kg diet.
HUMAN HEALTH
The relationship between dietary barium levels and the
levels in edible tissues of animals is not known. However,
the levels in soft tissues (e.g., muscle, kidney, heart, liver) of
rats fed high levels of BaClj, which is a highly bioavailable
form of barium, are low (<1 mg/kg fresh weight) (Tardiff et
al., 1980; Perry et al., 1989). This level would not be ex-
pected to be of concern for human health (ATSDR, 1992;
NTP, 1994; EPA, 1998; IPCS, 2001). However, barium ac-
cumulates in bone, and bones from animals fed at their MTL
could have excessive levels of barium.
FUTURE RESEARCH NEEDS
Future research on the toxicity of barium should focus on
two areas. First, the bioavailability of barium that naturally
contaminates water and feedstuffs should be determined be-
cause it is not known if the bioavailability in these sources is
similar to that of insoluble salts (e.g., BaS04), soluble salts
(e.g., BaClj), or is intermediate to these salts. Second, the
NOAEL of barium to poultry, livestock, companion animals,
and aquatic species needs to be determined. At this time rec-
ommendations must be based on toxicity experiments done
in rats and mice that use salts not normally found in nature.
SUMMARY
There are no known essential biochemical functions of
barium, and it is not usually considered as an essential nutri-
ent. The natural forms of barium have poor water solubility
and have very low toxicity. Commercially produced barium
salts, such as BaClj, are usually much more soluble in water
and are considerably more bioavailable and toxic. Once ab-
sorbed, barium is deposited predominantly in bone and teeth.
Toxic properties of barium are attributed to blocking potas-
sium channels and Ca++ agonist properties. Barium is not
typically supplemented to the diets of animals. Dietary lev-
els result from background levels in feed ingredients and by
accidental contamination.
REFERENCES
ATSDR (Agency for Toxic Substances and Disease Registry). 1992. Public
Health Statement for Barium and Compounds. CAS# 7440-39-3.
Agency for Toxic Substances and Disease Registry. Atlanta, GA: U.S.
Department of Health and Human Services, Public Health Service.
Available at http://www.atsdr.cdc.gov/toxprofiles/tp24.html. Accessed
on November 20, 2003.
Borzelleca, J. F., L. W. Condie, and J. L. Egle. 1988. Short-term toxicity
one and ten-day gavage of barium chloride in male and female rats. J.
Am. Coll. Toxicol. 7:675-686.
Boutet, C, and C. Chaisemartin. 1973. Proprietes toxiques specifiques des
sets metalliques chez Austropotamobius pallipes pallipes et Orconectes
limosus. C. R. Seances Soc. Biol. Fit. 167:1933-1938.
Cuddihy, R. G., and W. C. Griffith. 1972. A biological model describing
tissue distribution and whole-body retention of barium and lanthanum
in beagle dogs after inhalation and gavage. Health Phys. 23:621-633.
Daugherty, F. M. J. 1951. Effects of some chemicals used in oil well drill-
ing on marine animals. Sewage Ind. Wastes 23:1282-1287.
Dietz, D. D., M. R. Elwell, W. E. Davis, Jr., and E. F. Meirhenry. 1992.
Subchronic toxicity of barium chloride dihydrate administered to rats
and mice in the drinking water. Fundam. Appl. Toxicol. 19:527-537.
Edel, J., A. Di Nucci, E. Sabbioni, L. Manzo, M. Tonini, C. Minnoia, and S.
Candedoli. 1991. Biliary excretion of barium in the rat. Biol. Trace Ele.
Res. 30:267-276.
EPA (U.S. Environmental Protection Agency). 1974. Methods for chemical
analysis of water and wastes. EPA 625/6- 74-003a. Washington, D.C.:
U.S. Environmental Protection Agency.
EPA. 1998. Toxicological review of barium and compounds. Washington,
D.C.: U.S. Environmental Protection Agency. Available at http://
www.epa.gov/ngispgm3/iris/subst-fl.htm. Accessed on November 20,
2003.
Esser, A. 1935. Clinical, anatomical and spectrographic investigation of the
central nervous system in acute metal poisoning with particular consid-
eration of their importance for forensic medicine and tissue pathology.
Dtsch. Z. Gesamte Gerichtl. Med. 25:239.
Fernandes, J. 1., F. R. Lima, C. X. Mendonca, Jr., 1. Mabe, R. Albuquerque,
and P. M. Leal. 1999. Relative bioavailability of phosphorus in feed and
agricultural phosphates for poultry. Poult. Sci. 78:1729-1736.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
50
MINERAL TOLERANCE OF ANIMALS
Healy, W. B., and T. G. Ludwig. 1968. Barium content of teetti, bone and
kidney of twin slieep raised on pastures of differing barium content.
Arcli. Oral Biol. 13:559-563.
Hope, B.,C. Loy, and P. Miller. 1996. Uptake and trophic transfer of barium
in a teiTestrial ecosystem. Bull. Environ. Contam. Toxicol. 56:683-689.
IPCS (International Programme on Chemical Safety). 2001. Barium and
Barium Compounds: Concise International Chemical Assessment Docu-
ment 33. Geneva: World Health Organization. Available at http://
www.inchem.org/documents/cicads/cicads/cicad33.htm. Accessed on
November 20, 2003.
Mauras, Y., P. Allain, M. A. Roques, and C. Caron. 1983. Digestive absorp-
tion of barium after oral administration of barium sulfate for a radio-
logic study. Therapie 38:109-111.
McCauley, P. T., and 1. S. Washington. 1983. Barium bioavailability as the
chloride, sulfate, or carbonate salt in the rat. Drug Chem. Toxicol.
6:209-217.
NRC (National Research Council). 1977. Drinking Water and Health.
Washington, D.C.: National Academy Press.
NTP (National Toxicology Program). 1994. NTP Toxicology and Carcino-
genesis Studies of Barium Chloride Dihydrate (CAS No. 10326-27-9)
in F344/N Rats and B6C3F1 Mice (Drinking Water Studies). Natl.
Toxicol. Program Tech. Rep. Ser. 432:1-285.
Perry, H. M., Jr., S. J. Kopp, E. F. Perry, and M. W. Erlanger. 1989. Hyper-
tension and associated cardiovascular abnormalities induced by chronic
barium feeding. J. Toxicol. Environ. Health 28:373-388.
Robinson, W. O., R. R. Whetstone, and G. Edgington. 1950. The occur-
rence of barium in soils and plants. Technical bulletin, 1013:1-36.
Washington, D.C.: U.S. Department of Agriculture.
Roza, O., and L. B. Berman. 1971. The pathophysiology of barium: hy-
pokalemic and cardiovascular effects. J. Pharmacol. Exp. Ther.
177:433^39.
Sadiq, M., T. H. Zaidi, and H. al-Mohana. 1990. Barium bioaccumulation
in clams collected from different salinity regimens along the Saudi coast
of the Arabian Gulf. Bull. Environ. Contam. Toxicol. 45:329-335.
Schroeder, H. A., 1. H. Tipton, and A. P. Nason. 1972. Trace metals in man:
strontium and barium. J. Chronic Dis. 25:491-517.
Schwartze, E. W. 1920. Toxicity of barium carbonate to rats. Bulletin No.
915. Washington, D.C.: U.S. Depai'tment of Agriculture.
Sharp, R. A., and A. M. Knevel. 1971. Analysis of barium in barium sulfate
and diagnostic meals containing barium sulfate using atomic absorption
spectroscopy. J. Pharm. Sci. 60:458-460.
Smith, K. A. 1971. The comparative uptake and translocation of calcium,
strontium, barium and radium. 1. Bertholletia excelsa (Brazil nut tree).
Plant Soil 34:369-379.
Spangenberg, J. V., and G. N. Cherr. 1 996. Developmental effects of barium
exposure in a marine bivalve (Mytilus Californianus). Environ. Toxicol.
Chem. 15:1769-1774.
Stoewsand, G. S., J. L. Anderson, and M. Tutzke. 1988. Deposition of
barium in the skeleton of rats fed Brazil nuts. Nutr. Rep. Int. 38:
259-262.
Tardiff, R. G., M. Robinson, and N. S. Ulmer. 1980. Subchronic oral toxic-
ity of BaCl, in rats. J. Environ. Pathol. Toxicol. 4:267-275.
Taucins, E., A. Svilane, A. Valdmains, A. Buike, R. Zarina, and E.
Fedorova. 1969. Barium, strontium, and copper salts in chick nutrition.
Fiziol. Akt. Komp. Pitan. Zhivotn. 199:1.
USGS (U.S. Geological Survey). 2000. Subject: Commodity Statistics and
Information. Available at http://minerals.usgs.gov/minerals/pubs/
commodity. Accessed on November 20, 2003.
Vohra, P., and F. H. Kratzer. 1967. Absorption of barium sulfate and chro-
mic oxide from the chicken gastrointestinal tract. Poult. Sci. 46:1603—
1604.
Yamazaki, J., F. Ohara, Y. Harada, and T. Nagao. 1995. Barium and stron-
tium can substitute for calcium in stimulating nitric oxide production
in the endothelium of canine coronary arteries. Jpn. J. Pharmacol. 68:
25-32.
Zdanowicz, J. A., S. A. Mundorff, J. D. Featherstone, and H. M. Proskin.
1989. Inhibitory effect of barium on caries formation in rats. Caries Res.
23:65-69.
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53
TABLE 5-2 Barium Concentrations in Fluids and Tissues of Animals (mg/kg or mg/L)
Animal
Quantity Source
Duration
Route
Muscle Kidney
Bone
Reference
Rat
Omg/L
10 mg/L
50 mg/L
250 mg/L
BaClj
13 wk
Drinking
water
0.19° —
0.48
0.58
0.44
9. 1°
14.5
50.5
220
Tardiff et al.,
1980
Sheep (wethers) 7 mg/kg
Pasture
Weaning to
30 months
Feed
0.15"
60*
Healy andLudwig, 1968
35 mg/kg Pasture
0.61
250
"Data are on a fresh tissue basis.
*Data are on a dry tissue basis.
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Bismuth
INTRODUCTION
Bismuth (Bi) is a pinkishi-white, lustrous, soft mineral and
is widely distributed in small quantities throughout the
world. Although it has the crystal structure of a semi-metal,
bismuth is often considered a metal. Of all the metals, bis-
muth has the widest range between melting and boiling
points, the lowest thermal and heat conductivity, the highest
diamagnetic index, and the lowest absorption for neutrons.
Its crystal structure along with several of its other physical
properties makes it a substitute for lead in some applica-
tions. Bismuth forms compounds in oxidation states +3 and
+5, and its chemistry is diverse and poorly understood
(Briand and Burford, 1999). Bismuth nitrate is the initial
material used for the production of many bismuth com-
pounds used in industry and medicine.
World reserves of bismuth are usually associated with
lead deposits, except in Asia, where economically recover-
able bismuth is found with tungsten ores and some copper
ores, and in Australia, where bismuth is found with copper-
gold ores. Currently, bismuth is not refined in the United
States. Worldwide production is dominated by China,
Mexico, Peru, and Canada (USGS, 2003).
In 2002 about 42 percent of the bismuth used in the United
States was in fusible alloys, solders, and cartridges; 37 per-
cent in pharmaceuticals and chemicals; 19 percent in metal-
lurgical additives; and 2 percent in other uses (USGS, 2003).
Bismuth is used in several applications designed to provide
nontoxic substitutes for lead, including shot for waterfowl
hunting, fishing weights, plumbing fixtures, solders, and lu-
bricating greases. Other applications of bismuth chemicals
and compounds include uses in superconductors and pearl-
colored pigments for cosmetics and paints. Pharmaceuticals
based on trivalent bismuth have been used for more than a
century and include a variety of compounds to treat gas-
trointestinal ailments including diarrhea, upset stomach (bis-
muth subsalicylate, bismuth subnitrate, and bismuth subcar-
bonate), and ulcers and gastritis caused by Helicobacter
pylori (bismuth subcitrate).
ESSENTIALITY
Bismuth is not considered an essential nutrient for plants
or animals and has no known essential biochemical func-
tions in normal metabolism.
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Bismuth can be measured by atomic absorption spectro-
photometry (AAS). Graphite furnace AAS has greater sensi-
tivity than flame AAS. The primary difficulty in analysis is
volatilization, but this can be prevented by use of a platinum
matrix modifier (Slikkerveer et al., 1993). Sample prepara-
tion by acid digestion is necessary due to evaporation of bis-
muth during ashing. Other methods of analysis include
particle-induced x-ray emission (Canena et al., 1998), in-
ductively coupled plasma-mass spectrometry, and atomic
fluorescence spectrophotometry (Cava-Montesinos et al.,
2003). These other methods are rarely used because expen-
sive equipment is needed.
REGULATION AND METABOLISM
Bismuth compounds are very poorly absorbed in the in-
testinal tract. In rats and humans, greater than 99 percent of
an oral dose of a variety of bismuth compounds is lost in the
feces without absorption (Dresow et al., 1992; Slikkerveer et
al., 1995). This poor absorption is probably due to poor solu-
bility in both gastric juice (pH 1.2) and duodenal juice (pH
6.8). Bismuth citrate is more soluble at neutral pH (35 pmol/
L) than bismuth salicylate, gallate, aluminate, chloride, or
nitrate (<2 |jmol/L) and is slightly better absorbed. In dogs,
absorption in the small intestine appears to be greater than
absorption from the stomach (Hespe et al., 1993).
Once absorbed, bismuth binds to transferrin at specific
iron binding sites (70 percent) and to albumin (30 percent).
Presumably, these transport proteins deliver bismuth to tis-
sues (Sun and Szeto Ka, 2003). The tissue distribution of
54
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BISMUTH
55
absorbed bismuth is kidney»bone>red blood cells»liver,
heart, spleen, muscle » serum, and fat. Because of this dis-
tribution, bismuth concentrations in whole blood are a much
better indicator of bismuth exposure than levels in serum.
Bismuth is excreted relatively quickly by the kidney and to a
lesser extent in bile (Dresow et al., 1991).
SOURCES AND BIOAVAILABILITY
Bismuth is a rare element, occurring at about 200 to 350
|jg/kg in soils and 20 |Jg/L in fresh water and below 1 |Jg/L in
seawater (Lee, 1982). Bismuth levels in plants grown on
uncontaminated land are usually less than 60 |Jg/kg dry
weight, and levels in plants grown on contaminated soils do
not usually exceed 200 |Jg/kg dry weight (Bowen, 1979).
Levels in leaves are higher than in fruits or seeds (Jung et al.,
2002).
Bismuth is not normally added to the diet of animals and
is not typically a quantitatively important contaminant of
feedstuffs or additives. Consequently, the primary exposure
of animals is use of bismuth-based medications or accidental
contamination. A variety of over-the-counter and prescribed
preparations of bismuth compounds (e.g., Pepto Bismol®)
are used to treat animals for intestinal disorders ranging from
ulcers, gastritis, irritable colon, and constipation, to diarrhea
(Lambert, 1991; Roussel and Brumbaugh, 1991). They are
also used to improve the consistency and odor of stools.
TOXICOSIS
A characteristic sign that high levels of trivalent bismuth
compounds have been consumed is dark- or black-colored
feces, which is due to bismuth sulfide produced in the large
intestine. Toxic levels of bismuth may affect several target
organs depending upon dose, duration, and type of com-
pound (Table 6-1). In humans, encephalopathy is the most
life-threatening consequence of long-term exposure to bis-
muth subnitrate or subgallate, whereas bismuth subcitrate
results in nephrotoxicity. The nephrotoxicity is character-
ized by necrotic death of proximal tubular epithelial cells,
apparently because bismuth destabilizes the cell membrane
(Leussink et al., 2002). Bismuth compounds are not thought
to be carcinogens (Preussmann and Ivankovic, 1975).
Bismuth toxicities due to high levels in drinking water
have not been reported. Most bismuth compounds are not
sufficiently soluble in water to result in toxic levels. Suspen-
sions or colloids of bismuth compounds administered as
pharmaceuticals can be toxic if consumed at relatively high
levels.
Single Dose
Clinical signs of acute bismuth toxicosis in rats consist of
erect hairs and hunched posture within 6 hours of adminis-
tration of 627 mg/kg BW of bismuth as bismuth subcitrate;
at 48 hours rats have swollen ceca filled with gas and black
fluid (Leussink et al., 2001). Rats gavaged with 314 mg/kg
as bismuth subcitrate appeared visually normal but had im-
paired kidney function, which returned to normal within 48
hours. Absorption and toxicity of bismuth is enhanced when
it is complexed with cysteine. Such complexes have an LD^q
of 156 mg Bi/kg BW in rats (Chaleil et al., 1981).
Shot designed for waterfowl hunting given as a single
oral dose of 460 mg of bismuth metal to adult mallards did
not adversely affect food intake, body weight gain, hematol-
ogy, clinical chemistry, and histopathology (Ringelman et
al., 1993). Furthermore, bismuth levels in tissues were low
and not different from control birds.
Chronic
In humans the primary behavioral symptoms of chronic
consumption of bismuth subgallate or subnitrate is apathy,
mild ataxia, and headaches. More severe cases present with
dysarthria, confusion, hallucinations, epileptic seizures, and
occasionally death (Tillman et al., 1996). In the majority of
cases of bismuth toxicosis in humans, symptoms occurred
after consumption of doses that often exceeded 10 g of bis-
muth per day for 2 to 20 years. The pathogenesis of bismuth-
induced neurotoxicity is unknown, although it has been sug-
gested that the conversion of the original compounds into
more soluble or more toxic forms by intestinal bacteria is
involved (Bader, 1987). This is supported by the observation
that patients taking bismuth because of intestinal bacterial
overgrowth were most likely to suffer toxicosis. Bismuth
subcitrate and subsalicylate do not usually result in severe
neurological symptoms, but cause nephrotoxicity (Gorbach,
1990).
Pigs fed 333 mg/kg BW daily of bismuth from bismuth
subnitrate, and chickens fed diets containing 1 g/kg bismuth
from bismuth trioxide, did not display signs of toxicosis af-
ter exposure for 8 or 9 weeks, respectively (Hermayer et al.,
1977; PoUet et al., 1979). Bismuth subcitrate is the most
bioavailable of the common forms of bismuth and appears to
be the most toxic. Rats fed 314 mg/kg BW daily of bismuth
as bismuth subcitrate displayed functional and histopatho-
logical signs of toxicosis (Leussink et al., 2001).
Factors Influencing Toxicity
Absorption of bismuth in rats is increased by compounds
containing sulfhydryl groups, such as cysteine, and by
complexing agents, such as EDTA or citrate (Allain et al.,
1991; Chaleil et al., 1981). Cysteine increases the acute tox-
icity of bismuth (Chaleil et al., 1981; Krari et al., 1995).
Selenium affects the metabolic fate of bismuth
(Szymanska et al., 1978), and bismuth affects selenium me-
tabolism (Gregus et al., 1998), but the impact on toxicity is
not clear. In rats, bismuth diminishes both the biliary excre-
tion of selenium and its accumulation in erythrocytes. Bis-
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56
MINERAL TOLERANCE OF ANIMALS
muth also induces the expression of metallotliionein in tlie
liver and especially the kidney (Szymanska et al., 1993).
Bismuth also can displace zinc and cadmium from existing
metallothionein (Sun et al., 1999) and augments the excre-
tion of zinc and copper (Szymanska et al., 1993). However,
the effect of bismuth on the toxicity or the requirement of
these metals is not known.
TISSUE LEVELS
Normal bismuth levels in tissues are low, typically below
0.2 mg/kg (AUain et al., 1991). Although the relationship
between bismuth intake and bismuth accumulation in tissues
of production animals is not known, this metal is not
bioaccumulated in rats or dogs (Table 6-2). Even at high
daily doses of bismuth, well above therapeutic levels, muscle
levels are relatively low (<1 mg/kg). The kidney is the pri-
mary organ that accumulates bismuth. Dogs dosed daily with
108 mg/kg BW daily of bismuth ammonium citrate, which is
a relatively soluble form, accumulated 58 mg/kg bismuth
(wet weight) in their kidneys. Such levels in animal products
would not be expected to be of concern for human health.
MAXIMUM TOLERABLE LEVELS
The MTL of bismuth is defined as the dietary level that,
when fed for a defined period of time, will not impair ac-
cepted indices of animal health or performance.
Acute
Dogs can tolerate a daily dose of 108 mg/kg BW daily of
bismuth from bismuth subcarbonate or bismuth ammonium
citrate for 2 weeks without clinical signs of toxicosis (Hall
and Farber, 1972). Similarly, rats can tolerate 157 mg/kg
BW daily of bismuth from bismuth subcitrate for 2 weeks
(Leussink et al., 2001).
Chronic
Pigs tolerate 333 mg/kg BW daily of bismuth from bis-
muth subnitrate (Pollet et al., 1979), and chickens tolerate
1,000 mg/kg diet of bismuth from bismuth trioxide
(Hermayer et al., 1977).
Via Water
Most bismuth compounds are not sufficiently soluble in
water to cause toxicity.
FUTURE RESEARCH NEEDS
Little is known about the relationship between bismuth
intake and the levels in edible products, such as meat, milk,
and eggs. Very high levels of bismuth are sometimes admin-
istered to farm animals, and research is needed to determine
if food residue problems could occur.
SUMMARY
Bismuth is a rare element that normally occurs at low lev-
els in soil and water and is not bioaccumulated by plants or
animals. It is not normally added to the feed of animals and
occurs at very low levels in feedstuffs and mineral supple-
ments. Bismuth metal and its compounds are poorly absorbed
by the gastrointestinal tract and are relatively nontoxic. Toxi-
cosis is likely only if pharmaceutical preparations containing
bismuth are chronically administered at high doses.
REFERENCES
Allain, P., N. Krari, D. Chaleil, G. Lagier, and J. Jouglard. 1991. Effects of
some clielating agents on bismuth absoiption in the rat. Fund. Clin.
Pharmacol. 5:39^5.
Bader, J. P. 1987. The safety profile of De-Nol. Digestion 37 (Suppl. 2):
53-59.
Bowen, H. J. M. 1979. Environmental Geochemistry of the Elements. New
York: Academic Press.
Briand, G. G., and N. Burford. 1999. Bismuth compounds and preparations
with biological or medicinal relevance. Chem. Rev. 99:2601-2658.
Canena, J., J. Reis, A. S. Pinto, A. M. Santos, J. Leitao, T. Pinheiro, and M.
G. Quina. 1998. Distribution of bismuth in the rat after oral dosing with
ranitidine bismuth citrate and bismuth subcitrate. J. Pharm. Pharmacol.
50:279-283.
Cava-Montesinos, P., M. L. Cervera, A. Pastor, and M. de la Guardia. 2003.
Determination of ultratrace bismuth in milk samples by atomic fluores-
cence spectrometry. J. AOAC Int. 86:815-822.
Chaleil, D., F. Lefevre, P. Allain, and G. J. Martin. 1981. Enhanced bismuth
digestive absorption in rats by some sulfhydryl compounds: NMR study
of complexes formed. J. Inorg. Biochem. 15:213-221.
Dresow, B., R. Fischer, E. E. Gabbe, J. Wendel, and H. C. Heinrich. 1992.
Bismuth absorption from 205Bi-labelled pharmaceutical bismuth com-
pounds used in the treatment of peptic ulcer disease. Scand. J.
Gastroenterol. 27:333-336.
Dresow, B., P. Nielsen, R. Fischer, J. Wendel, E. E. Gabbe, and H. C.
Heimlich. 1991. Bioavailability of bismuth from 205Bi-labelled phar-
maceutical oral Bi-preparations in rats. Arch. Toxicol. 65:646-650.
Gorbach, S. L. 1990. Bismuth therapy in gastrointestinal diseases. Gastro-
enterology 99:863-875.
Gregus, Z., A. Gyurasics, andL. Koszorus. 1998. Interactions between se-
lenium and group Va-metalloids (arsenic, antimony and bismuth) in the
biliary excretion. Environ. Toxicol. Pharmacol. 5:89-99.
Hall, R. J., and T. Farber. 1972. Determination of bismuth in body tissues
and fluids after administration of controlled doses. J. Assoc. Off. Anal.
Chem. 55:639-642.
Hermayer, K. L., P. E. Stake, and R. L. Shippe. 1977. Evaluation of dietary
zinc, cadmium, tin, lead, bismuth and arsenic toxicity in hens. Poult.
Sci. 56:1721-1722.
Hespe, W., H. Kamsteeg, A. R. Harmsen, D. W. Hall, and L. G. De Leede.
1993. The mechanism of bismuth absorption. Gastroenterology
104:1242-1243.
Jung, M. C, I. Thornton, and H. T. Chon. 2002. Arsenic, Sb and Bi con-
tamination of soils, plants, waters and sediments in the vicinity of the
Dalsung Cu-W mine in Korea. Sci. Total Environ. 295:81-89.
Krari, N., Y. Mauras, and Allain. 1995. Enhancement of bismuth toxicity
by i-cysteine. Res. Commun. Mot. Pathol. Pharmacol. 89:357-364.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
BISMUTH
57
Lambert, J. R. 1991. Ptiarmacology of bismuth-containing compounds. Rev.
Infect. Dis. 13 (Suppl. 8):S691-695.
Lee, D. S. 1982. Determination of bismuth in environmental samples by
flameless atomic absorption spectrometry with hydride generation.
Anal. Chem. 54:1682-1686.
Lee, S. P., T. H. Lim, J. Pybus, and A. C. Clarke. 1980. Tissue distribution
of orally administered bismuth in the rat. Clin. Exp. Pharmacol. Physiol.
7:319-324.
Leussink, B. T., A. Slikkerveer, M. R. Engelbrecht, G. B. van der Voet, E.
J. Nouwen, E. de Heer, M. E. de Broe, F. A. de Wolff, and J. A. Bruijn.
2001. Bismuth overdosing-induced reversible nephi'opathy in rats. Arch.
Toxicol. 74:745-754.
Leussink, B. T., J. F. Nagelkerke, B. van de Water, A. Slikkerveer, G. B.
van der Voet, A. Srinivasan, J. A. Bruijn, F. A. de Wolff, and E. de
Heer. 2002. Pathways of proximal tubular cell death in bismuth nephro-
toxicity. Toxicol. Appl. Pharmacol. 180:100-109.
PoUet, S., S. Albouz, F. Le Saux, N. Baumann, and R. Bourdon. 1979.
Bismuth intoxication: bismuth level in pig brain lipids and in subcellu-
lar fractions. Toxicol. Eur. Res. 2:123-125.
Preussmann, R., and S. Ivankovic. 1975. Absence of carcinogenic activity
in BD rats after oral administration of high doses of bismuth oxychlo-
ride. Food Cosmet. Toxicol. 13:543-544.
Ringelman, J. K., M. W. Miller, and W. F. Andelt. 1 993. Effects of ingested
Tungsten-Bismuth-Tin shot on captive mallard. J. Wildlife Manage.
57:725-732.
Roussel, A. J., Jr., and G. W. Brumbaugh. 1991. Treatment of diarrhea of
neonatal calves. Vet. Clin. N. Am. Food Anim. Pract. 7:713-728.
Slikkerveer, A., R. B. Helmich, and F. A. de Wolff. 1993. Analysis for
bismuth in tissue by electrothermal atomic absorption spectrometry.
Clin. Chem. 39:800-803.
Slikkerveer, A., R. B. Helmich, G. B. van Der Voet, and F. A. de Wolff.
1995. Absorption of bismuth from several bismuth compounds during
in vivo perfusion of rat small intestine. J. Pharm. Sci. 84:512-515.
Sun, H., and Y. Szeto Ka. 2003. Binding of bismuth to serum proteins:
implication for targets of Bi(lll) in blood plasma. J. Inorg. Biochem.
94:114-120.
Sun, H., H. Li, 1. Harvey, and P. J. Sadler. 1999. Interactions of bismuth
complexes with metallothionein(ll). J. Biol. Chem. 274:29094-29101.
Szymanska, J. A., J. Chmielnicka, A. Kaluzynski, and W. Papierz. 1993.
Influence of bismuth on the metabolism of endogenous metals in rats.
Biomed. Environ. Sci. 6:134-144.
Szymanska, J. A., M. Zychowicz, A. J. Zelazowski, and J. K. Piotrowski.
1978. Effect of selenium on the organ distribution and binding of bis-
muth in rat tissues. Arch. Toxicol. 40:131-141.
Tillman, L. A., F. M. Drake, J. S. Dixon, and J. R. Wood. 1996. Review
article: safety of bismuth in the treatment of gastrointestinal diseases.
Aliment Pharmacol. Ther. 10:459-^67.
USGS (U.S. Geological Survey). 2003. Mineral Commodity Summaries:
Bismuth. Available at http:/minerals. usgs.gov/minerals/pubs/
commodity /bismuth/. Accessed November 25, 2003.
Zommer-Urbanska, S., E. Bulska, R. Pawlaczyk, and M. Kuklinski. 1994. De-
termination of bismuth in rabbit blood serum and tissues after administra-
tion of pharmaceuticals containing BijO,. Acta. Pol. Pharm. 51:7-10.
Copyright © National Academy of Sciences. All rights reserved.
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inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
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Boron
INTRODUCTION
Elemental boron (B) is a relatively inert metalloid ttiat
exists as either black monoclinic crystals or yellow-brown
amorphous powder when impure at room temperature.
However, boron as an element does not occur in nature; it is
always found bound to oxygen or in the borate form. The
most common commercial compounds of boron are anhy-
drous, pentahydrate and decahydrate (tincal) forms of
disodium tetraborate (borax, Na2B407), colemanite
(2CaO-3B203-5H20), ulexite (Na20-2CaO-5B203l6H20),
boric acid (H3BO3), and monohydrate and tetrahydrate
forms of sodium perborate (NaB03) (Woods, 1994). The
borate industry began in 1865 with the mining of borate
pandermite (priceite, 4CaO-5B,03-7H20) in Turkey.
Shortly thereafter, several borate deposits were found in
California and Nevada, including ulexite and colemanite in
Death Valley. Subsequently, tincal, colemanite and kernite
(Na,0-2B203-4H20) were found and mined in the Mojave
Desert (Woods, 1994). In addition to Turkey and the United
States, other countries producing borates are Peru, Chile,
Russia, and China. Sodium perborates are hydrolytically
unstable compounds containing boron-oxygen-oxygen
bonds; they are used as bleaches in detergents. The end uses
of boric acid and borates are diverse and include glass,
enamel, and synthetic gems manufacturing; wood and
leather preservatives; flame retardants; cosmetics; medical
products; detergents; insecticides; fertilizers; and neutron
absorbers for the nuclear industry. Boron halides and hy-
drides are used as catalysts and in jet and rocket fuels. El-
emental boron and its carbides and nitrides are used in high-
temperature abrasives and in steelmaking (Larsen, 1988).
Boric acid is thought to be the most prevalent form of
boron in animals and humans. Boric acid is colorless and
odorless with either a white granular powder or transparent
crystalline form, which are readily soluble in water. It is a
weak Lewis acid, accepting OH to form the tetrahedral,
tetrahydroxy borate anion at a pK^^ of 9.2 (Coughlin, 1996).
ESSENTIALITY
In 1923, signs of boron deficiency for several leguminous
plants were reported (Warington, 1923). Shortly thereafter,
Sommer and Lipman (1926) reported that boron was essential
for the completion of the life cycle of a number of plants. This
evidence was enough for wide acceptance of boron essentiality
for plants. More than 70 years elapsed before a biochemical
function for boron in plants was described. Boron cross-links
two dimers of rhamnogalacturonan-II, a small structurally com-
plex pectic polysaccharide found in primary cell walls of plants
(Matoh and Kobayashi, 2002). This function is not adequate to
explain all boron deficiency signs in plants, which most often
occur in dicotyledons raised on light-colored sands and silt
loams in humid regions of the world including the eastern
United States (Sprague, 1972). Boron stimulates the growth of
yeast (Saccharomyces cerevisiae) (Bennett et al., 1999) and is
an essential component of the sensor protein of autoinducer-2,
an extracellular signaling molecule used for cell-to-cell com-
munication by some bacteria (Chen et al., 2002). Boron has
been found to be essential for frogs (Fort et al., 1999a,b) and
zebrafish (Eckhert and Rowe, 1999) to complete their life cycle.
Substantial evidence from experiments comparing very low in-
takes (<100 Mg/kg diet for animals, 0.25 mg/d for humans) with
physiological intakes (1-3 mg/kg diet) of boron suggests that
boron is needed for optimal bone health, brain function, and
immune function in higher animals and humans (Nielsen, 1996,
2002a). However, although the evidence is similar, boron is not
consistently accepted as an essential nutrient for higher animals
as it is for plants. Apparently, the lack of a clearly defined spe-
cific biochemical function is a major obstacle to wide accep-
tance of boron essentiality by animal and human nutritionists.
60
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BORON
61
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Less modern methods involving colorimetric, gravimet-
ric, and titrametric tecliniques can adequately determine bo-
ron in materials that contain high amounts such as fertilizer,
soils, and some botanical materials. The spectrophotometric
method whereby the colored complex of Azomethine-H and
boron is measured is an international standard method and
still used (Lopez et al., 1993). Accurate analysis of boron in
amounts found in most biological materials requires more
modern techniques and instrumentation, which indicate that
boron concentrations reported in the older biological and
food composition literature often may be too high. Analyti-
cal techniques that utilize inductively-coupled plasma, such
as inductively-coupled argon plasma spectrometry (ICAP),
inductively-coupled plasma mass spectrometry (ICP-MS,
probably the most sensitive technique), and inductively-
coupled plasma emission spectroscopy (ICP-ES) have be-
come the instruments of choice for boron analysis. How-
ever, other methods including neutron-activation-mass
spectrometry and prompt gamma-activation analysis have
been used to accurately measure boron in biological materi-
als. Most of the difficulties encountered in boron analysis
occur during sample preparation (Downing et al., 1998).
Because boron is so prevalent in the environment, contami-
nation is a major problem in analysis of boron in low
amounts. Sources of this contamination have been listed
(Downing et al., 1998). Among those listed are sample con-
tact with borosilicate glass and ashing procedures using the
same digestion vessels for both high and low boron-contain-
ing samples, which can result in cross contamination because
of the difficulty in removing all boron that has bound to or
migrated into the vessel surface. Another significant con-
cern in boron analysis is its volatility and mobility. Because
some boron in biological materials is water soluble, it is
mobile and could be lost if a sample is slowly frozen for
storage or freeze-drying; quick freezing in liquid nitrogen
will reduce the redistribution or loss of boron. Many boron
compounds volatilize at temperatures far below those re-
quired for dry ashing (Hunt and Shuler, 1989). Ashing a neu-
tral or acidic sample requires boron to be quickly converted
into a nonvolatile compound. This can be accomplished by
ashing at low temperatures or by making the sample basic
(Downing et al., 1998). Because of the contamination and
loss concerns, the validity of any boron analysis can only be
assured by the use of quality control procedures such as the
concomitant analysis of standard reference materials.
REGULATION AND METABOLISM
Absorption and Metabolism
About 85-90 percent of ingested borax, boric acid, and,
apparently, dietary boron is rapidly absorbed and excreted
mostly in the urine shortly after ingestion (Jansen et al., 1984;
Hunt et al., 1997; Nielsen and Penland, 1999; Sutherland et
al., 1999). Because there is no usable radioisotope of boron,
the study of its metabolism is difficult. It is likely, however,
that most ingested boron is converted into boric acid, the
dominant species of boron compounds hydrolyzed at the pH
of the gastrointestinal tract, and then absorbed and excreted
mainly in that form. Absorption of boron through the intact
skin is negligible, and, thus, is not a toxicological concern
(Wester et al., 1998). However, toxic amounts can be ab-
sorbed through damaged skin (Nielsen, 1970; Draize and
Kelley, 1959). Several cases of boron toxicosis, some result-
ing in death, have been reported in humans who had open
skin lesions treated with medications containing high
amounts of boric acid (Pfeiffer et al., 1945); such medica-
tions are no longer in use. The boron hydrides (boranes),
which are highly toxic, can be absorbed by the lungs (NRC,
1980). Inhaled borates also can be absorbed by the lung but
are relatively nontoxic.
IVIetabolic Interactions
The most relevant property of boric acid, the prevalent
form of boron in vivo, is its ability to form complexes with
substances containing c«-hydroxyl groups (Hunt, 2002).
During transport in the body, boric acid most likely is weakly
attached to organic molecules containing cw-hydroxyl
groups. The interaction with organic compounds containing
hydroxyl groups most likely also affects the response to de-
ficient and toxic intakes of boron. For example, boron toxic-
ity is alleviated by riboflavin (Roe et al., 1972). It is also
hypothesized that boron can enhance the function of other
nutrients and hormones acting at the cell membrane level
(Nielsen, 2002a). Thus, changes in the status of some nutri-
ents and hormones that act at the cell membrane level appar-
ently can affect the response to various intakes of boron.
Among the nutrients that affect the response to dietary boron
are vitamin D, magnesium, molybdenum, calcium, selenium,
protein, and omega-3 fatty acids (Hoffman et al., 199 1 ; Hunt,
1994; Nielsen, 2002b). Estrogen status apparently affects the
response to boron deficiency: postmenopausal women on
hormone replacement therapy showed changes in plasma
copper and serum I7p-estradiol concentrations when de-
prived of boron, but those not on hormone replacement
therapy did not (Nielsen et al., 1992). High intakes of boron
have been investigated as antidotes to fluoride toxicity in
rabbits (Baer et al., 1977; Elsair et al., 1980), pigs (Seffner
and Teubener, 1983), and sheep (Wheeler et al., 1988).
IVIechanisms of Toxicity
The mechanism of toxicity for boron has not been firmly
established. Ku and Chapin (1994) studied the possible
mechanisms through which boric acid causes toxicologic
manifestations in testicular function of the rat. Their find-
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MINERAL TOLERANCE OF ANIMALS
ings indicated ttiat boron toxicosis did not occur througli in-
ducing a riboflavin deficiency or impairing pliospfiorus, cal-
cium, and zinc metabolism or utilization. They did obtain
findings suggesting that boron toxicosis may be the result of
an impairment of energy metabolism through the inhibition
of some enzymes that produce utilizable energy substrates.
Also, they suggested that toxic amounts of boric acid af-
fected the DNA synthetic activity of both mitotic (sper-
matogonial) and meiotic (post-spermatogonial) germ cells
of the rat.
SOURCES AND BIOAVAILABILITY
Sources of exposure to boron have been reviewed (Howe,
1998; IPCS, 1998). Boron enters the environment mainly
through the weathering of rocks; volatilization from seawa-
ter; burning of oil, coal, and wood; industrial and household
use of boron-containing products (especially soaps and de-
tergents); fertilizers; and sewage and sludge disposal. Bo-
ron-containing vitreous materials such as fiberglass, boro-
silicate glass, enamels, frits, and glazes are not significant
sources of exposure because the boron is tightly bound in the
glassy structure. Significant amounts of boron are not present
in the atmosphere (average of 20 ng/m-' over continents).
The Earth's crust contains about 10 mg B/kg, ranging from 5
mg/kg in basalts to 100 mg/kg in shales. Boron occurs in
soils at concentrations ranging from 10 to 300 mg/kg (aver-
age 30 mg/kg). Concentrations in surface waters range
widely from 0.001 to 150 mg/L (Coughhn, 1998). The aver-
age boron concentration in the oceans is 4.6 mg/L. Most
freshwater concentrations of boron (mostly in the boric acid
form) are below 0.4 mg/L and not lowered by treatment for
drinking water. Boron accumulates in aquatic and terrestrial
plants but does not magnify through the food chain. On a dry
weight basis, boron concentrations range between 26 and
382 mg/kg in submerged aquatic freshwater plants, 11 and
57 mg/kg in freshwater emergent vegetation, and 2 and 95
mg/kg in terrestrial plants (IPCS, 1998). Among plants,
monocotyledons generally contain less boron than dicotyle-
dons. Boron deficiency occurs in a wide variety of plants
when their dry matter concentrations are less than 10 mg/kg
(Bell, 1997). A rough method of diagnosing boron toxicity
in plants is determining boron in plant components; dry tis-
sue boron concentrations exceeding 250 mg/kg often indi-
cate boron toxicity (Nable et al., 1997). On a wet weight
basis, boron concentrations in marine invertebrates and fish
are similar to their environment, or between 0.5 and 4 mg/kg
(IPCS, 1998). The preceding values indicate that diet and
sometimes drinking water are the major sources of exposure
to boron. For example, the daily boron intakes for humans
were estimated to be 0.44 |jg from ambient air, 0.5 \ig from
soil, 0.1 mg from consumer products, 0.2-0.6 mg from drink-
ing water, and 1.2 mg from the diet (IPCS, 1998).
Boron supplements for the alleviation of arthritis in hu-
mans appeared in 1976 (Newnham, 1994). Shortly after bo-
ron was indicated as being beneficial to postmenopausal
women (Nielsen et al., 1987), the presence of boron in over-
the-counter supplements increased markedly. Most supple-
ments provide boron in amounts that would not be toxic for
humans, usually 3 mg or less daily. Although boron supple-
ments for animals are not approved in the United States, one
report (Newnham, 2002) indicates that they have been used
in other parts of the world. Boron supplements reportedly
are effective in the treatment of arthritic dogs, horses, and
cattle; the dose administered was 3 mg B/day per 25 kg BW
for 2 to 4 weeks (Newnham, 2002). It would not be surpris-
ing to find that boron supplementation to poultry may be
considered because of reports showing that this improved
bone strength and growth (Rossi et al., 1993; Wilson and
Ruszler, 1997; Kurtoglu et al., 2001). Boron supplementa-
tion of pigs may be considered because it may increase body
weight, bone strength, and immune function (Armstrong et
al., 2002; Armstrong and Spears, 2003).
As indicated in the absorption discussion above, boron in
foods, feeds, water, and supplements are generally highly
available.
TOXICOSIS
Single Dose
The oral LD^q for boron (provided as boric acid and bo-
rax) varies among animal species. Values in mg B/kg BW
are in the range of 400-700 for mice and rats (Pfeiffer et al.,
1945; Weir and Fisher, 1972); 210 for guinea pigs
(Verbitskaya, 1975); and 250-350 for dogs, rabbits, and cats
(Pfeiffer etal., 1945; Verbitskaya, 1975). The signs of toxic-
ity in rats, mice, and guinea pigs upon administration of large
single doses of borax and boric acid used to determine the
LDjQ were depression, ataxia, occasional convulsions, de-
creased body temperature, and violet-red color of skin and
all mucous membranes (Pfeiffer et al., 1945; Weir and
Fisher, 1972). Goats dosed with 2 g soluble borate fertilizer
had increased cerebrospinal fluid monoamine metabolites
and exhibited seizure-like activity suggesting a central ner-
vous system effect (Sisk et al., 1990). Necropsy signs of
boron toxicity in mice, rats, and dogs included glomerular
damage (altered permeability of capillaries) and tubular dam-
age (cellular vacuolization and shedding of cells into the tu-
bular lumen) in the kidney, and an increase in small dark
cells (probably microglia) in the spinal cord and in the gray
matter of the brain cortex (Pfeiffer et al., 1945). The reported
single toxic dose of boric acid for humans varies from 20 to
45 g (3.5 to 7.9 g boron) for adults (Potter, 1921) and 1 to
6 g (0.175 to 1.05 g boron) for infants (McNally and Rust,
1928; Young et al., 1949). However, these values are based
on old reports and may be questionable. Of the 784 poison-
ing cases examined by one group (Litovitz et al., 1988), no
deaths or severe manifestations of toxicity were found in
patients ingesting boric acid in single doses ranging from 10
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BORON
63
mg to 88.8 g (1.75 mg to 15.54 g boron); 88 percent did not
exhibit any toxicity symptoms in this group whose median
age was 2 years. In the patients that showed symptoms, the
most common were vomiting, abdominal pain, and diarrhea.
Lethargy, headache, lightheadedness, and atypical rash were
seen less frequently. Similar findings were obtained from
the records of another 300 cases of single, acute ingestions
of 10 to 297 g of boric acid (1.75 to 52 g of boron) (Linden,
et al., 1986). The initial responses to the lethal doses re-
ported in the older literature included nausea, vomiting
(sometimes with blood), abdominal pain, and diarrhea.
Shock with low blood pressure, tachycardia, and cyanosis
sometimes occurred. Death apparently was the result of cen-
tral nervous system depression. Autopsy signs of toxicity
included a cloudy swelling of the kidneys, centrolobular he-
patic necrosis, and hemorrhagic enteritis. It should be noted
that no human deaths from large single dose boric acid in-
gestion were reported between 1928 and 1988 (Litovitz et
al., 1988).
Acute
The topic of the first publication in the American Journal
of Physiology was boron toxicity in dogs (Chittenden and
Gies, 1898). This study found that daily doses of 3 g of boric
acid or 5 g of borax for 8-10 days had no physiological or
pharmacological effect in adult dogs weighing 8 to 12 kg.
However, doses of 5 to 10 g B/d resulted in an increase in
urinary nitrogen, sulfur and phosphorus excretion, and doses
of borax and boric acid equal to 1.5-2.0 percent of daily diet
intake induced nausea and vomiting. Rabbits orally adminis-
tered 800 mg boric acid/kg BW/day for 4 days exhibited
anorexia, weight loss, and diarrhea; 850 and 1,000 mg boric
acid/kg BW resulted in 100 percent mortality (Draize and
Kelley, 1959). Cattle consuming water containing 150 or
300 mg B/L as boric acid for 30 days exhibited lethargy,
inflammation, and edema in the legs and around the dew-
claws; occasional diarrhea; and decreased food consump-
tion, weight gain, hematocrit, and hemoglobin concentration
(Green and Weeth, 1977). Rats fed 262.5 mg B/kg BW/day
as boric acid or borax in the diet exhibited reduced weight
gain and died within 3 to 6 weeks (Weir and Fisher, 1972).
Administration of 250 mg boric acid/kg BW on gestational
days 6-19 to rabbits resulted in increased prenatal mortality,
decreased litter size, and malformed fetuses (primarily
cardiovascular defects) (Price et al., 1996). Fish are not
especially sensitive to boron as borate or boric acid. The
concentration of borate acutely toxic to freshwater fish (le-
thal to 50 percent in 1 to 6 days) ranges from 14 to 3,400 mg/
L of water (ECETOC, 1996). Rainbow trout and zebra fish
are the most sensitive species tested to date. The LCjq for
most fish ranged between 200 and 1,000 mg/L of water.
Eleven infants fed formulae that were accidentally prepared
with a 2.5 percent boric acid solution for 1 to 5 days (2 to
14.06 g boric acid, or (0.350 to 2.458 g boron total) exhib-
ited diarrhea, vomiting, erythema, exfoliation, desquamation
of the skin, and central nervous system irritation; five of the
infants died (Wong et al., 1964).
Chronic
Table 7-1 summarizes the doses and effects of a chronic
consumption of high or nonphysiologic amounts of boron by
various animals and humans. Table 7-1 indicates that intakes
of boron in the form of boric acid and borates that are approxi-
mately 100- to 1,000-fold greater than normal are needed to
induce reproductive and developmental toxicity in animals.
Thus, other than waterfowl in specific habitats, it is unlikely
that boron toxicity under normal environmental conditions is
a concern for animals. High concentrations of boron have been
found in irrigation drainwaters and food consumed by water-
fowl in certain areas of the western United States, such as the
San Joaquin Valley and Kesterson National Wildlife Refuge
in California. Reported waterfowl food boron concentrations
(mg/kg dry weight) in these regions include aquatic insects,
150; algae, 400; wetland plants, up to 1,860; and seeds, up to
3,500 (ECETOC, 1996). An excellent summary of the fairly
extensive human toxicity reports has been given by Culver
and Hubbard (1996). Prolonged consumption of boric acid by
humans has been reported to result in mild gastrointestinal
irritation, anorexia, disturbed digestion, nausea, vomiting, and
an erythematous rash. Seven infants provided soothers dipped
in a proprietary borax and honey mixture containing about 3 g
B/28 mL (23 mg boron/mL) for 4 to 10 weeks (calculated to
be about 30 to 90 mg B/day) suffered from seizures that
stopped upon cessation of use of the mixture (O'Sullivan and
Taylor, 1983).
Factors Influencing Toxicity
Interaction with polyhydroxyl compounds can affect the
response to high intakes of boron. Substances possessing cis-
hydroxyl groups on adjacent carbons fonn very stable diesters
with boron that are almost undissociable in water. This indi-
cates why supplementing the diet with riboflavin, a dihydroxy
compound, protects chickens against boric acid toxicity (Roe
et al., 1972). The toxicity of boron to fish is increased with
increasing water hardness (Birge and Black, 1977). High di-
etary selenium (15 and 60 mg/kg diet) and low dietary protein
(7 percent compared to 22 percent of the diet) increased the
toxicity of boron in mallard ducklings. Feeding 1 g B/kg diet
to ducks enhanced the accumulation of toxic amounts of sele-
nium in liver caused by low dietary protein when dietary sele-
nium was high (Hoffman et al., 1991).
TISSUE LEVELS
Boron is distributed throughout the soft tissues and fluids
at concentrations mostly between 0.015 and 2.0 mg/kg wet
weight. Table 7-2 shows representative values in various
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64
MINERAL TOLERANCE OF ANIMALS
organs and fluids from various animals and humans. The
values show that tissues from animals fed nontoxic amounts
of boron are not of potential concern for human boron toxic-
ity. As with other mineral elements, overcoming homeostatic
mechanisms by high boron intakes will elevate tissue and
blood boron concentrations. However, the values in Table 7-
2 indicate that no animal tissue or fluid used as a food will
accumulate boron to the extent that it would be of potential
toxicological concern for humans. The uptake and retention
of boron are highest in bone.
MAXIMUM TOLERABLE LEVELS
The most sensitive indicators of boron toxicity in animals
have been decreased weight and rib anomalies in the devel-
oping rat fetus which occurs with intakes of about 13 mg
B/kg BW/day (IPCS, 1998). Thus, 10 mg B/kg BW/day may
be a reasonable MTL for animals; this translates into about
135 mg/kg diet. Other effects of boron toxicity and the dose
at which they occur in mg/kg BW/day include further rib
anomalies in fetuses and testicular pathology in growing rats
at about 25; decreased fetal body weight and increased fetal
cardiovascular malformations in the rabbit, and severe tes-
ticular pathology in the rat at about 40; testicular atrophy
and sterility in the rat at about 55; and decreased fetal body
weight in the mouse at 80 (IPCS, 1998). Mallard duckling
growth was adversely affected with dietary boron concentra-
tions of 30 and 300 mg/kg, and survival was reduced at 1,000
mg/kg (IPCS, 1998). Based on studies with reconstituted
water, the NOAEL concentration for early life stages of rain-
bow trout, considered the most sensitive fish species, has
been found to range from 0.009 to 0.103 mg B/L. However,
studies using natural water collected from three sources con-
taining a variety of boron concentrations, including 0.75 mg/
L in the Firehole River in Yellowstone National Park,
showed no adverse effects on embryo-larval stages of rain-
bow trout (Black et al., 1993). Lowest observed effect (de-
tectable change in embryo-larval morphology or survival)
concentrations ranged from 1.10 to 1.73 mg B/L for the three
sources of natural water. Therefore, under natural conditions,
the no-effect-level for fish is apparently around 1 mg B/L
(ECETOC, 1996).
HUMAN HEALTH
Based on developmental effects in rats, mice, and rabbits,
the acceptable upper limit of daily intake of boron has been
estimated to be in the range of 1 1 to 20 mg/day for adults
(Murray, 1996; WHO, 1996; NRC, 2001). However, the
NOAEL for humans can be established at 1 g boric acid (175
mg B)/day for adults, or about 2.5 mg B/kg BW/day, and the
chronic-adverse-effect level is 5 mg B/kg BW/day (Culver
and Hubbard, 1996). These relatively high values indicate
why boric acid and borates were used for many years as food
preservatives without apparent widespread toxicity. This
practice stopped when boric acid and borates became con-
sidered as poisons because of numerous reports of toxic ef-
fects after accidental and inappropriate domestic and medi-
cal misuse of these compounds. Thus, intakes of boron at or
below the MTL suggested above for animals would not be
expected to result in tissue boron concentrations that would
be of concern for human health. The guide level for drinking
water in Europe of 1 mg B/L is considered conservative with
an ample safety margin (ECETOC, 1994). Respiratory ex-
posure to boron in industry has not caused chronic pulmo-
nary effects, and skin exposure does not cause dermatitis
(Culver and Hubbard, 1996).
FUTURE RESEARCH NEEDS
The toxicity of boron for captive animals has been rela-
tively well studied. However, there is a need to more clearly
define the mechanisms of boron toxicity. Also, more needs
to be known about the effects of boron at low levels of in-
take, including establishing the basis for its apparent essen-
tial or beneficial actions, and the intake below which these
actions are compromised. The mechanisms through which
boron is absorbed from the gastrointestinal tract need further
definition. Further knowledge in these areas should help
identify interactions with other nutrients and the environ-
ment that could modify the toxic and beneficial actions of
boron.
SUMMARY
Boron is always found in nature bound to oxygen or as
borates. Boric acid is the prevalent form of boron in animals
and humans. It is a weak Lewis acid that forms complexes
with biological substances containing c«-hydroxyl groups.
Boron is accepted as essential for plants because it is re-
quired to complete their life cycle. To date, only one essen-
tial function has been found for boron in plants; it cross-
links two dimers of rhamnogalacturan-II, a small structurally
complex pectic polysaccharide found in primary cell walls.
Although boron has been found essential to complete the life
cycle of some animals (frog, zebrafish), it is not generally
accepted as essential, apparently because it lacks a defined
biochemical function, for higher animals and humans. Ana-
lytical techniques that utilize inductively-coupled plasma
have become preferred for the analysis of boron in biologi-
cal materials. Ashing of samples is a critical step in the accu-
rate analysis of boron in low amounts because of contamina-
tion and volatilization concerns. About 85-90 percent of
dietary boron is rapidly absorbed and excreted mostly in the
urine. Toxic amounts of boron can be absorbed through dam-
aged, but not intact, skin. The diet and sometimes drinking
water are the major sources of exposure to boron. Boron is a
relatively nontoxic element. Reported oral LD^q values for
boron in mg/kg BW are in the range of 400-700 for mice and
rats, 210 for guinea pigs, and 250-350 for dogs. Cattle con-
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BORON
65
suming water containing 150-300 mg B/L exhiibited toxicity
signs including decreased food consumption and weigtit.
Boron concentrations found lethal to 50 percent of tested
freshwater fish ranged from 14 to 3,400 mg/L of water. This
large range occurred because rainbow trout and zebrafish
were much more sensitive than most other fish tested, and
one species was very nonsensitive. The LC^q for most fish
ranged between 200 and 1,000 mg/L of water. Chronic tox-
icity studies indicate that intakes of boron in the form of
borates and boric acid approximately 100- to 1,000-fold
greater than normal are needed to induce reproductive and
developmental toxicity in animals. The most sensitive indi-
cators of boron toxicity in animals have been decreased
weight and rib anomalies in the developing rat fetus which
occurs with intakes of about 13 mg/kg BW/day. Thus, other
than for waterfowl and fish in some specific habitats, it is
unlikely that boron toxicity under nonnal environmental con-
ditions is a concern for animals.
REFERENCES
Anderson, D. L., W. C. Cunningham, and T. R. Lindstrom. 1994. Concen-
trations and intaites of H, B, S, K, Na, CI, and NaCl in foods. J. Food
Comp. Anal. 7:59-82.
Armstrong, T. A., and J. W. Spears. 2003. Effect of boron supplementation
of pig diets on the production of tumor necrosis factor-a and interf eron-
y. J. Anim. Sci. 81:2552-2561.
Armstrong, T. A., W. L. Flowers, J. W. Spears, and F. H. Nielsen. 2002.
Long-term effects of boron supplementation on reproductive char-
acteristics and bone mechanical properties in gilts. J. Anim. Sci.
80:154-161.
Baer, H. P., R. Bech, J. Franise, A. Grunewald, W. Kochmann, F. Melson,
H. Runge, and W. Wiedner. 1977. Ergebnisse tierexperimenteller
Untersuchungen an Kaninchen mit Natriumfluorid unter Einwiritung
von Gegenmitteln. Z. Gesamte Hyg. Grenzgeb. 23:14—20.
Bai, Y., and C. D. Hunt. 1996. Absorption and distribution of boron in rats
following a single oral administration of boron. Proc. N. D. Acad. Sci.
50:53.
Bell, R. W. 1997. Diagnosis and prediction of boron deficiency for plant
production. Plant Soil 193:149-168.
Bennett, A., R. 1. Rowe, N. Soch, and C. D. Eckhert. 1999. Boron stimu-
lates yeast (Saccharomyces cerevisiae) growth. J. Nutr. 129:2236-2238.
Birge, W. J., and J. A. Black. 1977. Sensitivity of vertebrate embryos to
boron compounds. Report No. EPA 560/1-76-008. Washington, D.C.:
Environmental Protection Agency, Office of Toxic Substances.
Bu-ge, W. J., J. A. Black, A. G. Westerman, T. M. Short, S. B. Taylor, and
M. C. Parekh. 1984. Toxicity of boron to embryonic and larval stages of
Rainbow trout (Salmo gairdneri) exposed in reconstituted and natural
waters. Cincinnati. OH: Completion Report prepared for the Proctor &
Gamble Company.
Black, J. A., J. B. Barnum, and W. J. Birge. 1993. An integrated assessment
of the biological effects of boron to the Rainbow trout. Chemosphere
26:1383-1413.
Chapin, R. E., and W. W. Ku. 1994. The reproductive toxicity of boric acid.
Environ. Health Perspect. 102(Suppl 7):87-91.
Chen, X., S. Schauder, N. Potier, A. V. Dorsselaer, 1. Pelczer, B. L. Bassier,
and F. M. Hughson. 2002. Structural identification of a bacterial quo-
rum-sensing signal containing boron. Nature 415:545-549.
Chittenden, R. H., and W. J. Gies. 1898. The influence of borax and boric
acid upon nutrition with special reference to protein metabolism. Am. J.
Physiol. 1:1-39.
Coughlin, J. R. 1996. Inorganic borates: chemistry, human exposure, and
health and regulatory guidelines. J. Trace Elem. Exp. Med. 9:137-151.
Coughlin, J. R. 1998. Sources of human exposure. Overview of water sup-
plies as sources of boron. Biol. Trace Elem. Res. 66:87—100.
Culver, B. D., and S. A. Hubbard. 1996. Inorganic boron health effects in
humans: an aid to risk assessment and clinical judgement. J. Trace Elem.
Exp. Med. 9:175-184.
Dixon, R. L., R. J. Sherins. and 1. P. Lee. 1979. Assessment of environmen-
tal factors affecting male fertility. Environ. Health Perspect. 30:53—68.
Downing, R. G., P. L. Strong, B. M. Hovanec, and J. Northingtion. 1998.
Considerations in the determination of boron at low concentrations. Biol.
Trace Elem. Res. 66:3-21.
Draize, J. H., and E. A. Kelley. 1959. The urinary excretion of boric acid
preparations following oral administration and topical applications to
intact and damaged skin of rabbits. Toxicol. Appl. Pharmacol. 1 :
267-276.
ECETOC (European Centre for Ecotoxicology and Toxicology of Chemi-
cals). 1994. Technical Report 65. Reproductive and General Toxicol-
ogy of Some Inorganic Borates and Risk Assessment for Human Be-
ings. Brussels: ECETOC.
ECETOC (European Centre for Ecotoxicology and Toxicology of Chemi-
cals). 1996. Special Report No. 11. Ecotoxicology of some Inorganic
Borates, Interim Report. Brussels: ECETOC.
Eckhert, C. D., and R. 1. Rowe. 1999. Embryonic dysplasia and adult retinal
dystrophy in boron-deficient zebrafish. J. Trace Elem. Exp. Med.
12:213-219.
Elsair, J., R. Merad, R. Denine, M. Reggabi, B. Alamir, S. Benali, M.
Azzouz, and K. Khelfat. 1980. Boron as a preventive antidote in acute
and subacute fluoride intoxication in rabbits: its action on fluoride and
calcium-phosphorus metabolism. Fluoride 13:129-138.
Fail, P. A., J. D. George, J. C. Seely, T. B. Grizzle, and J. J. Heindel. 1991.
Reproductive toxicity of boric acid in Swiss (CD-I) mice: assessment
using the continuous breeding protocol. Fund. Appl. Toxicol. 17:
225-239.
Fort D. J., T. L. Propst, E. L. Stover, F. J. Mumiy, and P. L. Strong. 1999a.
Adverse effects from low dietary and environmental boron exposure on
reproduction, development, and maturation in Xenopus laevis. J. Trace
Elem. Exp. Med. 12:175-185.
Fort, D. J., E. L. Stover, P. L. Strong, and F. J. Murray. 1999b. Effect of
boron deprivation on reproductive parameters in Xenopus laevis. J.
Trace Elem. Exp. Med. 12:187-204.
Green, G. H., M. D. Lott, and H. J. Wieth. 1973. Effects of boron-water on
rats. Proc. West. Sec. Am. Soc. Anim. Sci. 24:254.
Green, G. H., and H. J. Weeth. 1977. Responses of heifers ingesting boron
in water. J. Anim. Sci. 46:812-818.
Hoffman, D. J., M. B. Camardese, L. J. LeCaptain, and G. W. Pendleton.
1990. Effects of boron on growth and physiology in mallard ducklings.
Environ. Toxicol. Chem. 9:335-346.
Hoffman, D. J., C. J. Sanderson, L. J. LeCaptain, E. Cromartie, and G. W.
Pendleton. 1991. Interactive effects of boron, selenium, and dietary pro-
tein on survival, growth, and physiology in Mallard ducklings. Ai'ch.
Environ. Contam. Toxicol. 20:288-294.
Howe, P. D. 1998. A review of boron effects in the environment. Biol.
Trace Elem. Res. 66:153—166.
Hunt, C. D. 1989. Dietary boron modified the effects of magnesium and
molybdenum on mineral metabolism in the cholecalciferol-deficient
chick. Biol. Trace Elem. Res. 22:201-220.
Hunt, C. D. 1994. The biochemical effects of physiologic amounts of di-
etary boron in animal nutrition models. Environ. Health Perspect.
102(Suppl. 7):35^3.
Hunt, C. D. 2002. Boron-binding-biomolecules: a key to understanding the
beneficial physiologic effects of dietary boron from prokaryotes to hu-
mans. Pp. 21-36 in Boron in Plant and Animal Nutrition, H. E.
Goldbach, B. Rerkasem, M. A. Wimmer, P. H. Brown, M.Thellier, and
R. W. Bell, eds. New York: Kluwer Academic/Plenum Publishers.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
66
MINERAL TOLERANCE OF ANIMALS
Hunt, C. D., andT. R. Sliuler. 1989. Open- vessel, wet-ash, low-temperature
digestion of biological materials for inductively coupled argon plasma
spectroscopy (ICAP) analysis of boron and other elements. J. Micronutr.
Anal. 6:161-174.
Hunt, C. D., J. L. Herbel, and F. H. Nielsen. 1997. Metabolic responses of
postmenopausal women to supplemental dietary boron and aluminum
during usual and low magnesium intake: boron, calcium, and magne-
sium absorption and retention and blood mineral concentrations. Am. J.
Clin. Nutr. 65:803-813.
IPCS (International Programme on Chemical Safety). 1998. Environmental
Health Criteria 204. Boron. Geneva: World Health Organization.
Jansen, J. A., J. S. Schou, and B. Aggerbeck. 1984. Gastro-intestinal ab-
sorption and in vitro release of boric acid from water-emulsifying oint-
ments. Food Chem. Toxicol. 22:49-53.
Ku, W. W., and R. E. Chapin. 1994. Mechanism of the testicular toxicity of
boric acid in rats: in vivo and in vitro studies. Environ. Health Perspect.
102(Suppl. 7):99-105.
Ku, W. W., R. E. Chapin, R. F. Moseman, R. E. Brink, K. D. Pierce, and K.
Y. Adams. 1991. Tissue disposition of boron in male Fischer rats.
Toxicol. Appl. Pharmacol. 111:145-151.
Ku, W. W., R. E. Chapin, R. N. Wine, and B. C. Gladen. 1993. Testicular
toxicity of boric acid (B A): relationship of dose to lesion development
and recovery in the F344 rat. Reprod. Toxicol. 7:305—319.
Kuiloglu, v., F. Kurtoglu, and B. Coskun. 2001. Effects of boron supple-
mentation of adequate and inadequate vitamin Dj-containing diet on
performance and serum biochemical characters of broiler chickens. Res.
Vet. Sci. 71:183-187.
Lanoue, L., P. L. Strong, and C. L. Keen. 1999. Adverse effects of a low
boron environment on the preimplantation development of mouse em-
bryos in vitro. J. Trace Elem. Exp. Med. 12:235-250.
Larsen, L. A. 1988. Boron. Pp. 129-141 in Handbook on Toxicity of Inorganic
Compounds, H. G. Seller and H. Sigel, eds. New York: Marcel Dekker.
Lee. 1. P., R. J. Sherins, and R. L. Dixon. 1978. Evidence for induction of
germinal aplasia in male rats by environmental exposure to boron.
Toxicol. Appl. Pharmacol. 45:577-590.
Linden, C. H., A. H. Hall, K. W. Kulig, and B. H. Rumack. 1986. Acute
ingestions of boric acid. Clin. Toxicol. 24:269-279.
Litovitz, T. L., G. M. Oderda, and B. F. Schmitz. 1988. Clinical manifesta-
tions of toxicity in a series of 784 boric acid ingestions. Am. J. Emerg.
Med. 6:209-213.
Lopez, F. J., E. Gimenez, and F. Hernandez. 1993. Analytical study on the
determination of boron in environmental water samples. Frensenius J.
Anal. Chem. 346:984-987.
Matoh, T., and M. Kobayashi. 2002. Boron function in plant cell walls.
Research progress since 1997. Pp. 143-155 in Boron in Plant and Ani-
mal Nutrition, H. E. Goldbach, B. Rerkasem, M. A. Wimmer, P. H.
Brown, M. Thellier, and R. W. Bell, eds. New York: Kluwer Academic/
Plenum Publishers.
McNally, W. D., and C. A. Rust. 1928. The distribution of boric acid in
human organs in six deaths due to boric acid poisoning. J. Am. Med.
Assoc. 90:382-383.
Murray, F. J. 1996. Issues in boron risk assessment: pivotal study, uncer-
tainty factors, and ADls. J. Trace Elem. Exp. Med. 9:231-243.
Nable, R. O., G. S. Baiiuelos, and J. G. Paull. 1997. Boron toxicity. Plant
Soil 193:181-197.
Naghii, M. R., and S. Samman. 1996. The effect of boron supplementation
on the distribution of boron in selected tissues and on testosterone syn-
thesis in rats. J. Nutr. Biochem. 7:507-512.
Newnham, R. E. 1994. Essentiality of boron for healthy bones and joints.
Environ. Health Perspect. 102(Suppl. 7):83-85.
Newnham, R. E. 2002. How boron is being used in medical practice. Pp.
59—62 in Boron in Plant and Animal Nutrition. H. E. Goldbach, B.
Rerkasem, M. A. Wimmer, P. H. Brown, M. Thelher, and R. W. Bell,
eds. New York: Kluwer Academic/Plenum Publishers.
Nielsen, F. H. 1996. Evidence for the nutritional essentiality of boron. J.
Trace Elem. Exp. Med. 9:215-229.
Nielsen, F. H. 1998. The justification for pro viding dietary guidance for the
nutritional intake of boron. Biol. Trace Elem. Res. 66:319-330.
Nielsen, F. H. 2002a. The nutritional importance and pharmacological po-
tential of boron for higher animals and human. Pp. 37^9 in Boron in
Plant and Animal Nutrition, H. E. Goldbach, B. Rerkasem, M. A.
Wimmer, P. H. Brown, M. Thellier, and R. W. Bell, eds. New York:
Kluwer Academic/Plenum Publishers.
Nielsen, F. H. 2002b. Does boron have an essential function similar to an
omega-3 fatty acid function. Pp. 1238-1250 in Macro and Trace Ele-
ments, Mengen-und Spurenelemente, M. Anke, R. Muller, U. Schafer,
and M. Stoeppler, eds. Leipzig: Schubert- Verlag.
Nielsen, F. H., and J. G. Penland. 1999. Boron supplementation of peri-
menopausal women affects boron metabolism and indices associated
with macromineral metabolism, hormonal status and immune function.
J. Trace Elem. Exp. Med. 12:251-261.
Nielsen, F. H., C. D. Hunt, L. M. Mullen, and J. R. Hunt. 1987. Effect of
dietary boron on mineral, estrogen, and testosterone metabolism in post-
menopausal women. FASEB J. 1:394—397.
Nielsen, F. H, S. K. Gallagher, L. K. Johnson, and E. J. Nielsen. 1992.
Boron enhances and mimics some effects of estrogen therapy in post-
menopausal women. J. Trace Elem. Exp. Med. 5:237-246.
Nielsen, G. H. 1970. Percutaneous absorption of boric acid from boron-
containing preparations in rats. Acta Pharmacol. Toxicol. 28:413^24.
NRC (National Research Council). 1980. Boron. Pp. 71-83 in Mineral Tol-
erance of Domestic Animals. Washington, D.C.: National Academy
Press.
NRC. 2001. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic,
Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum,
Nickel, Silicon, Vanadium, and Zinc. Washington, D.C.: National Acad-
emy Press.
O'SuUivan, K., and M. Taylor. 1983. Chronic boric acid poisoning in in-
fants. Arch. Dis. Child. 58:737-749.
Owen, E. C. 1944. The excretion of borate by the dairy cow. J. Dairy Sci.
13:243-248.
Pfeiffer, C. C, L. F. Hallman, and 1. Gersh. 1945. Boric acid ointment. A
study of possible intoxication in the treatment of burns. J. Am. Med.
Assoc. 128:266-274.
Potter, C. 1921. A case of borax poisoning. J. Am. Med. Assoc. 76:378.
Price, C. J., M. C. Man-, C. B. Myers, J. C. Seely, J. J. Heindel, and B. A.
Schwetz. 1996. The development of toxicity of boric acid in rabbits.
Fund. Appl. Toxicol. 34:176-187.
Price, C. J., P. L. Strong, F. J. Murray, andM. M. Goldberg. 1998. Develop-
mental effects of boric acid in rats related to maternal blood boron con-
centrations. Biol. Trace Elem. Res. 66:359-372.
Roe, D. A., D. B. McCormick, and R. T. Lin. 1972. Effects of riboflavin on
boric acid toxicity. J. Pharm. Sci. 61:1081-1085.
Rossi, A. F., R. D. Miles, B. L. Damron, and L. K. Flunker. 1993. Effects of
dietary boron supplementation on broilers. Poult. Sci. 72:2124—2130.
Seal, B. S., and H. J. Weeth. 1980. Effect of boron in drinking water on the
male laboratory rat. Bull. Environ. Contam. Toxicol. 25:782—789.
Seffner, W., and W. Teubener. 1983. Antidotes in experimental fluorosis on
pigs morphological studies. Fluoride 16:33-37.
Shuler, T. R., P. Pootrakul, P. Yarnsukon, and F. H. Nielsen. 1990. Effect of
thalassemia/hemoglobin E disease on macro, trace, and ultratrace ele-
ment concentrations in human tissue. J. Trace Elem. Exp. Med. 3:
31^3.
Sisk, D. B., B. M. Colvin, A. Merrill, K. Bondari, and J. M. Bowen. 1990.
Experimental acute inorganic boron toxicosis in the goat: effects on
serum chemistry and CSF biogenic amines. Vet. Hum. Toxicol. 32:
205-211.
Smith, G. J., and V. P. Anders. 1989. Toxic effects of boron on mallard
reproduction. Environ. Toxicol. Chem. 8:943-950.
Sommer, A. L., and C. B. Lipman. 1926. Evidence of the indispensable na-
ture of zinc and boron for higher green plants. Plant Physiol. 1 :23 1-249.
Sprague, R. W. 1972. The ecological significance of boron. Los Angeles:
Anderson. Ritchie & Simon: The Ward Ritchie Press.
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BORON
67
Sutherland, B., L. R. Woodliouse, P. Strong, and J. C. King. 1999. Boron
balance in humans. J. Trace Elem. Exp. Med. 12:271-284.
Verbitskaya, G. V. 1975. Experimental and field investigations concerning
the hygienic evaluation of boron-containing drinking water. Gig. Sanit.
7:49—53 (in Russian with English summary).
Ward, N. I. 1993. Boron levels in human tissues and fluids. Pp. 724—728 in
Trace Elements in Man and Animals -TEMA 8, M. Anke, D. Meissner,
and C. F. Mills, eds. Gersdorf: Verlag Media Touristik.
Warington, K. 1923. The effect of boric acid and borax on the broad bean
and certain other plants. Ann. Bot. 37:629-672.
Weir, R. J., and R. S. Fisher. 1972. Toxicologic studies on borax and boric
acid. Toxicol. Appl. Pharmacol. 23:351-364.
Wester, R. C., X. Hui, T. Hartway, H. I. Maibach, K. Bell, M. J. Schell, D.
J. Northington, P. L. Strong, and B. D. Culver. 1998. In vivo percutane-
ous absorption of boric acid, borax, and disodium octaborate
tetrahydrate in humans compared to in vitro absorption in human skin
from infinite and finite doses. Toxicol. Sci. 45:42-51.
Wheeler, S. M., A. D. Turner, and K. J. Ellis. 1988. The effects of sodium
borate and sodium bicarbonate upon fluoride retention and serum cal-
cium and phosphate in sheep. J. Trace Elem. Electrolytes Health Dis.
2:185-189.
WHO (World Health Organization). 1996. Boron. Pp. 175-179 in Trace
Elements in Human Nutrition and Health. Geneva: World Health Orga-
nization.
Wilson, J. H., and P. L. Ruszler. 1997. Effects of boron on growing pullets.
Biol. Trace Elem. Res. 56:287-294.
Wilson, J. H., and P. L. Ruszler. 1998. Long term effects of boron on layer
bone strength and production parameters. Br. Poult. Sci. 39:1 1-15.
Wong, L. C, M. D. Heimbach, D. R. Truscott, and B. D. Duncan. 1964.
Boric acid poisoning: report of 11 cases. Can. Med. Assoc. J. 90: 1018-
1023.
Woods, W. G. 1994. An introduction to boron: history, sources, uses, and
chemistry. Environ. Health Perspect. 102 (Suppl. 7):5-ll.
Young, E. G., R. P. Smith, and O. C. Mackintosh. 1949. Boric acid as a
poison. Can. Med. Assoc. J. 61:44.
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8
Bromine
INTRODUCTION
Bromine (Br) is a lialogen and thie only nonmetallic ele-
ment that is a liquid at ambient temperature and pressure.
Naturally occurring bromine is found bound to metals in the
form of inorganic salts — the bromides. Seawater is the great-
est reservoir for bromine on Earth and contains 65 mg/L.
The concentration in brine or salt lakes may be enriched by
up to 100-fold. Bromine is abundant in saline deposits origi-
nating from evaporated lakes. Bromine levels in soils typi-
cally range from 1 to 20 mg/kg, although some volcanic soils
have considerably higher levels.
Bromine-containing compounds have a variety of agri-
cultural, medicinal, and industrial uses (Lyday, 2002). Me-
thyl bromide is used to fumigate the soil for controlling in-
sects, nematodes, weeds, and pathogens in more than 100
food crops and in forest and ornamental nurseries. This gas-
eous form of organic bromide is also used for postharvest
protection and quarantine treatments of foods, feedstuff s, and
wood products in warehouses, ship holds, freight cars, and
other areas of storage. Methyl bromide was defined by the
Montreal Protocol of 1991 as a chemical that contributes to
depletion of the Earth's ozone layer, so most countries have
agreed to phase out its use. Potassium bromate is used in the
baking industry to help bread rise in the oven and to create a
good texture in the finished product. Bromine is also used in
the production of brominated vegetable oils that are used as
emulsifiers in some soft drinks and fruit drinks.
Many bromide-containing drugs were developed in the
early 20th century and used as sedatives and anticonvulsants,
but they have mostly been replaced by other drugs. How-
ever, bromide salts are still commonly used to treat epilepsy
in dogs (March et al., 2002). Bromine is used to estimate the
extracellular space in physiology research. Industrial uses of
bromine-containing compounds include drilling fluids, fuel
additives, photographic chemicals, rubber additives, and
polybrominated biphenyls used as flame retardants. These
industrial compounds are not expected to be found in feed
ingredients or water consumed by animals and are not con-
sidered in this analysis.
ESSENTIALITY
Several studies have demonstrated improved growth in
chicks and mice fed diets supplemented with bromide, but
evidence is conflicting and not robust. There are no known
essential biochemical functions of bromine and it is not usu-
ally considered as an essential nutrient (NRC, 1980).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Total bromide in foods is usually measured following
ashing in alkali (Greve, 1983) and determining the bromide
ion content using gas chromatography or high performance
liquid chromatography (HPLC). Ashing converts organic
forms of bromine into inorganic salts.
Bromine introduced into foodstuffs by fumigation with
methyl bromide is unstable and converts to inorganic forms
rapidly over time. However, some conditions may result in
trace levels of unconverted fumigant. Given the differing
toxicological profiles of organic and inorganic forms, their
analytical differentiation may be desirable. Procedures for
the separation of organic bromides by extraction permit the
measurement of both organic and inorganic bromide con-
centrations (Getzendaner, 1975).
REGULATION AND METABOLISM
Bromide has very similar physiochemical properties as
chloride and has a comparable metabolic profile (reviewed
by van Leeuwen and Sangster, 1987). Like chloride, bro-
mide is very efficiently absorbed from the gastrointestinal
tract and found predominantly in the extracellular fluids,
gastric secretions, and saliva. Urine is the primary excretory
pathway for bromide (Pavelka et al., 2000). The glomerulus
72
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BROMINE
73
filters bromide, which competes with chloride for reabsorp-
tion in the tubules. Most of the bromide in saliva and gastric
juices is reabsorbed in the small intestine, and little bromide
is found in the feces.
Steady state pharmokinetics of bromide can be described
by a simple one-compartment model with a linear relation-
ship between plasma bromide concentrations and the in-
gested dose (van Logten et al., 1973; van Logten et al., 1974;
Rauws, 1975). The half-life of bromide at normal dietary
chloride levels is 10-12 days in humans (van Leeuwen and
Sangster, 1987), 15 days in dogs (March et al., 2002), and 3
days in rats (Rauws and Van Logten, 1975). The half-life is
strongly dependent upon the dietary chloride level and is
increased IG-fold by a chloride deficiency and decreased
similarly by dosing chloride. Thus, sodium chloride is used
to treat bromide toxicosis.
Bromide replaces chloride in intra- and extracellular flu-
ids, and hypochloremia is diagnostic of bromide toxicity.
The hydrated bromide ion is slightly larger than the hydrated
chloride ion and has slightly different transport kinetics
across the cell membrane. Bromide causes hyperpolariza-
tion of nerve cell membranes, which is thought to be the
basis of its pharmacological properties on the central ner-
vous system.
The thyroid gland partially discriminates between iodine
and bromide, but bromide levels are often higher in this tis-
sue than others, especially during an iodine deficiency. Thy-
roid peroxidase does not oxidize bromide, and bromine does
not substitute for iodine in thyroxine (Hosoya, 1963). How-
ever, high levels of bromide decrease iodine uptake by the
thyroid and may exacerbate an iodine deficiency (Pavelka et
al., 2002). Conversely, dietary bromide reduces the toxicity
of iodine in chicks (Baker et al., 2003).
SOURCES AND BIOAVAILABILITY
Bromine is not typically supplemented to the diets of ani-
mals. Dietary levels result from background levels in feed
ingredients and contaminating levels introduced by the use
of bromine-based fumigants and disinfectants.
Natural bromine levels in crops range from approximately
8 to 50 mg/kg dry matter (summarized in van Leeuwen and
Sangster, 1987). Marine plants are the exception and some
types of algae can concentrate very high levels of bromine.
Fishmeal has the highest natural bromide level (12.6 mg/kg)
of feedstuffs normally used in animal diets (Greve, 1983).
Fruits, grains, and vegetables grown in soils fumigated
with methyl bromide may have higher levels of bromide.
Bromide residues are especially high when planting occurs
closely after soil fumigation (Roughan and Roughan, 1984)
and can reach levels up to 4,037 mg/kg dry weight in foliage
vegetables (Maw and Kempton, 1982). However, when good
agricultural practices are followed, most foods have levels
below 40 mg/kg (Greve, 1983).
Postharvest fumigation of foods and feed ingredients can
result in high levels of bromide residues. Fumigation of feed
grains and hay, especially during shipment or storage, is cur-
rently a common practice. Residue levels in fumigated wheat
of 70 mg/kg (Corvi et al., 1977) and in corn fumigated in a
ship's hold of 200 mg/kg have been reported (Thompson
and Hill, 1969).
Other dietary sources of bromine include salt that has
been prepared from brines containing high levels of bromide.
Bakery wastes may contain trace levels of potassium bro-
mate added in the baking process. Polybrominated biphe-
nyls and other industrial chemicals have contaminated ani-
mal feeds due to mislabeling or mishandling; these isolated
events are increasingly rare due to improvements in material
handling practices (Reich, 1983).
Bromide salts are presumed to be rapidly and completely
absorbed in the gastrointestinal tract using transport systems
for the chloride ion. Bioavailability studies have not been
formally conducted, but 96 percent of an oral bromide dose
is absorbed in humans (Vaiseman et al., 1986).
TOXICOSIS
The toxicological profile of bromine depends on its form.
Currently, most toxic studies on bromine concern inhalation
toxicity of methyl bromide gas to human applicators. Though
this gas is highly toxic, it is not a known contaminant of
animal feeds or water and is not currently of concern for
animal safety. Inorganic bromide salts that results from the
decomposition of methyl bromide following fumigation of
hay, feed ingredients, or occasionally complete feeds is the
primary source of bromine in animal diets (Knight and
Costner, 1977; Knight and Reina-Guerra, 1977). Data on
which to base the toxicity of bromide in animal feeds come
mostly from studies in humans and laboratory animals, with
only a few studies available with production or companion
animals (Table 8-1). The historical medical use of bromide
salts at relatively high levels compelled extensive research
in the first half of the 20th century on bromide intoxication
(bromism). Toxicity of bromide depends on its replacement
of chloride in body fluids. Because of the large pool size of
body chloride, expression of bromide toxicosis typically oc-
curs only after chronic exposure to relatively high levels of
bromide (Trump and Hochberg, 1976).
Potassium bromate is more toxic than bromide salts due
to its oxidizing properties. It also is a carcinogen (Kurokawa
etal., 1986; lARC, 1986; DeAngelo etal., 1998), but it is not
a known contaminant of animal feeds. Polybrominated bi-
phenyls are known liver carcinogens in rats at levels of
around 10 mg/kg (NTP, 1993).
Single Dose
Bromide salts irritate the gastric mucosa and cause nau-
sea and vomiting (Trump and Hochberg, 1976). The result-
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74
MINERAL TOLERANCE OF ANIMALS
ing feed refusal coupled with the pharmokinetics of bromide
in the body make it unlikely that systemic toxicosis would
occur when animals are presented with a single meal of a
feed containing very high levels of bromine.
Acute
The acute (48-hour) NOAEL for bromide as sodium bro-
mide in water for guppies and medaka is 78 and 250 mg/L
(Canton et al., 1983). Lethality (LC,,,) occurs at 16,000 and
25,000 mg/L, respectively. Orally dosed bromide salts have
very low acute toxicity in rodents and an LDjq of 3.5 to 7 g
Br/kg BW has been reported (Smith and Hambourger, 1925;
Vossetal., 1961).
Chronic
In humans, symptoms of chronic bromide intoxication are
apathy, headaches, ataxia, memory loss, drowsiness, and loss
of emotional control. Dermal symptoms, including acne or a
nodular rash, may also occur. Tremors, hallucination, stupor,
and coma occur in severe cases (reviewed in van Leeuwen and
Sangster, 1987). Shifts in EEG activities, increased circulating
thyroxine, and other endocrine changes are the primary physi-
ological disruptions of a chronic toxicosis (Sangster et al.,
1983). A summary of studies in humans indicates that the daily
NOAEL for bromide in humans is 4 mg/kg BW (van
Leeuwen and Sangster, 1987). The Food and Agriculture
Organization/World Health Organization (FAO/WHO
Pesticide Committees, 1967) applied a margin of safety and
set the acceptable daily intake of bromide at 1 mg/kg.
The most sensitive indicators of bromide toxicosis in ro-
dents are changes in behavior and weight gain (Hansen and
Hubner, 1983). In mice, the NOAEL is between 400 and
1,200 mg/kg diet (Hansen and Hubner, 1983). In rats, distur-
bances in thyroid and renal function occur at dietary levels
between 1,200 and 19,200 mg/kg diet (Loeber et al., 1983)
and a decrease in fertility occurs at 1,200 mg/kg (van
Leeuwen et al., 1983). A chronic 2-year study using feed
fumigated with methyl bromide found that residual bromide
levels of 500 mg/kg diet were not toxic to rats as indicated
by normal livability and normal histopathology, but this level
did cause a small reduction in body weight; 200 mg/kg had
no effect on body weight (Mitsumori et al., 1990).
Potassium bromide is frequently used as therapy for epi-
leptic dogs, and toxicosis occurs occasionally (Yohn et al.,
1992; Podell, 1998). Characteristic clinical signs are ataxia
and lameness, especially of the pelvic limbs, but the maxi-
mum tolerable level has not been determined.
Bromide toxicity is treated by removal of the bromide
source and administering sodium chloride. In humans, com-
plete recovery follows normalization of blood bromide levels.
Factors Influencing Toxicity
The primary factor affecting toxicity of bromide is the
dietary chloride level because high dietary chloride increases
the renal excretion of both chloride and bromide. For ex-
ample, the daily bromine intake needed to maintain near
toxic levels of serum bromide is about twice as high for dogs
fed 1.3 percent dietary chloride as those fed 0.4 percent and
three times as high as those fed 0.2 percent (Trepanier and
Babish, 1995). In rats the biological half-life of bromide in-
creases from 3 days at normal dietary chloride levels to 25
days when sodium chloride is excluded from the diet (Rauws
and Van Logten, 1975).
TISSUE LEVELS
In rats, plasma and tissue bromine levels increase linearly
with dietary levels. Bromide replaces about half of the chlo-
ride in plasma and tissues at a dietary level of 19,200 mg/kg
(van Logten et al., 1974). Lynn et al. (1963) found that dairy
cows fed 9.5 to 38 mg/kg dietary bromide as NaBr have milk
levels ranging from 1 to 12 mg/kg on a wet weight basis
(Table 8-2). Bromide in cow's milk was proportional to the
level in the blood, which was proportional to the level in the
feed. More recently, Vreman et al. (1985) reexamined the
relationship between dietary and milk bromide levels. Diets
contained 22, 69, or 115 mg/kg inorganic bromide residue
that resulted from the decomposition of methyl bromide fu-
migate and were fed for 5 weeks. Milk bromide increased
linearly with dietary bromide, and the average ratio between
dietary bromine concentration and milk bromine concentra-
tion was 0.27. At the end of the study, tissues were sampled
and muscle bromide concentrations increased linearly with
dietary bromide, with the 115 mg/kg dietary level giving
20.8 mg/kg fresh muscle.
MAXIMUM TOLERABLE LEVELS
The MTL of bromine is defined as the dietary level that,
when fed for a defined period of time, will not impair ac-
cepted indices of animal health or performance. Bromide is
the mostly likely form of bromine that animals are exposed
to through their feed and water. No adverse effects of bro-
mide at levels of 300 mg/kg diet or below have been re-
ported in chronic feeding studies in rodents, and levels of
500 mg/kg slightly reduce growth but do not cause pathol-
ogy. Hatchling chicks tolerate 5,000 mg/kg for 4 weeks with-
out impaired growth or efficiency of feed conversion. Dogs
tolerate 20 mg/kg BW/day with no adverse effects. Maxi-
mum tolerable levels have not been determined for other
animal species.
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inemi Tnlemnce nf Animals- Sennnd Revised Edition
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BROMINE
75
HUMAN HEALTH
Tissue levels of bromine in farm animals have not been
determined at dietary levels that are toxic. However, extrapo-
lation of muscle bromine concentrations known to occur in
animals fed subtoxic levels to animals fed maximum toler-
able levels indicates that residue levels would not be of con-
cern for human health. The daily NOAEL for bromide in
humans is 4 mg/kg BW (van Leeuwen and Sangster, 1987).
FUTURE RESEARCH NEEDS
Bromine toxicity has not been a problem in animal nutri-
tion so very little research has been done. Accurate estimates
of maximum tolerable dietary levels cannot be made for any
species except rodents, and more research is needed. Resi-
due levels in meat, milk, and eggs of animals fed maximum
tolerable dietary levels of bromide are also needed. Finally,
there are insufficient data available to estimate maximum
tolerable bromide levels in water of any species.
SUMMARY
Bromine is widely distributed in nature and is found al-
most exclusively as bromide salts. There are no known es-
sential biochemical functions of bromine, and it is not usu-
ally considered as an essential nutrient. Bromine is not
typically supplemented to the diets of animals and dietary
levels result from background levels in feed ingredients and
contaminating levels introduced by the use of bromine-based
fumigants and disinfectants. Bromide has very similar
physiochemical properties as chloride and has a comparable
metabolic profile and tissue distribution. Bromide competes
with chloride in metabolism and causes hyperpolarization of
nerve cell membranes, which is thought to be the basis of its
pharmacological properties on the central nervous system.
Because of the large pool size of body chloride, expression
of bromide toxicosis typically occurs only after chronic ex-
posure to relatively high levels of bromide. It is rapidly ex-
creted, primarily in the urine, so toxic levels decline quickly
after the source has been removed.
REFERENCES
Baker, D. H., T. M. Pan', and N. R. Augspurger. 2003. Oral iodine toxicity
in ctiiciis can be reversed by supplemental bromine. J. Nutr. 133:2309—
2312.
Barber, R. S., R. Braude, and K. G. Mitchell. 1971. Arsanilic acid, sodium
salicylate and bromide salts as potential growth stimulants for pigs re-
ceiving diets with and without copper sulfate. Br. J. Nutr. 25:381-389.
Bosshardt, D. K., J. W. Huff, and R. H. Barnes. 1956. Effect of bromide on
chicii growth. Proc. Soc. Exp. Biol. Med. 92:219-224.
Canton, J. H., P. W. Wester, and E. A. Mathijssen-Spiekman. 1983. Study
on the toxicity of sodium bromide to different freshwater organisms.
Food Chem. Toxicol. 21:369-378.
Corvi, C, I. Dallmayr, M. Meyer, and I. Vogel. 1977. Bromine residues in
foods after use of methyl bromide. Mitt. Geb. Lebensmittelunters. Hyg.
68:431^t41.
DeAngelo, A. B., M. H. George, S. R. Kilburn, T. M. Moore, and D. C.
Wolf. 1998. Carcinogenicity of potassium bromate administered in the
drinking water to male B6C3F1 mice and F344/N rats. Toxicol. Pathol.
26:587-594.
Doberenz. A. R., A. A. Kurnick, B. J. Hulett, and B. L. Reid. 1965. Bromide
and fluoride toxicities in the chick. Poult. Sci. 67:32-37.
FAOAVHO Pesticide Committees. 1967. Evaluation of some pesticide resi-
dues in food. Rome: Food and Agriculture Organization of the United
Nations.
Getzendaner, M. E. 1975. A review of bromine determination in foods. J.
Assoc. Off. Anal. Chem. 58:711-716.
Greve, P. A. 1983. Bromide-ion residues in food and feedstuffs. Food Chem.
Toxicol. 21:357-359.
Hansen, K., andH.Hubner. 1983. Effectsof bromide on behaviour of mice.
Food Chem. Toxicol. 21:405^08.
Hosoya. T. 1963. Effect of various reagents including antithyroid com-
pounds upon the activity of thyroid peroxidase. J. Biochem. 53:381.
lARC. 1986. Potassium bromate. lARC Monogr. Eval. Carcinog. Risk
Chem. Hum. 40:207-220.
Knight, H. D., and G. C. Costner. 1977. Bromide intoxication of horses,
goats, and cattle. J. Am. Vet. Med. Assoc. 171:446^148.
Knight, H. D., and M. Reina-Guerra. 1977. Intoxication of cattle with so-
dium bromide-contaminated feed. Am. J. Vet. Res. 38:407^09.
Kurokawa, Y., S. Aoifi, Y. Matsushima, N. Taiiamura, T. Imazawa, and Y.
Hayashi. 1986. Dose-response studies on the carcinogenicity of potas-
sium bromate in F344 rats after long-term oral administration. J. Nat.
Cancer Inst. 77:977-982.
Loeber, J. G., M. A. Franken, and F. X. van Leeuwen. 1983. Effect of
sodium bromide on endocrine parameters in the rat as studied by immu-
nocytochemistry and radioimmunoassay. Food Chem. Toxicol. 21:
391^04.
Lyday, P. A. 2002. Bromine. USGS, Minerals Yearbook. Available at http:
//minerals. usgs.gov/minerals/pubs/commodity /bromine/index. html.
Lynn, G. E., S. A. Shrader, O. H. Hammer, and C. A. Lassiter. 1963. Occur-
rence of bromides in the milk of cows fed sodium bromide and grain
fumigated with methyl bromide. J. Agric. Food Chem. 1 1:87-92.
March, P. A., M. Podell, and R. A. Sams. 2002. Pharmacokinetics and tox-
icity of bromide following high-dose oral potassium bromide adminis-
tration in healthy beagles. J. Vet. Pharmacol. Ther. 25:425^32.
Maw, G. A., and R. J. Kempton. 1982. Bromine in soils and peats. Plant and
Soil 65:103-110.
Mitsumori, K., K. Maita, T. Kosaka, T. Miyaoka, and Y. Shirasu. 1990.
Two-year oral chronic toxicity and carcinogenicity study in rats of diets
fumigated with methyl bromide. Food Chem. Toxicol. 28:109— 1 19.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
NTP (National Toxicology Program). 1993. Toxicology and Carcinogen-
esis Studies of Polybrominated Biphenyls. NTP TR 398. Research Tri-
angle Park, NC: U.S. Department of Health and Human Services.
Pavelka, S., A. Babicky, M. Vobecky, and J. Lener. 2000. Bromide iiinetics
and distribution in the rat. II. Distribution of bromide in the body. Biol.
Trace Elem. Res. 76:67-74.
Pavelka. S., A. Babicky, J. Lener, and M. Vobecky. 2002. Impact of high
bromide intake in the rat dam on iodine transfer to the sucklings. Food
Chem. Toxicol. 40:1041-1045.
Podell, M. 1998. Antiepileptic drug therapy. Clin. Tech. Small Anim. Pract.
13:185-192.
Rauws, A. G. 1975. Bromide pharmacokinetics: a model for residue accu-
mulation in animals. Toxicology 4:195-202.
Rauws, A. G., and M. J. Van Logten. 1975. The influence of dietary chlo-
ride on bromide excretion in the rat. Toxicology 3:29-32.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
76
MINERAL TOLERANCE OF ANIMALS
Reich, M. R. 1983. Environmental politics and science: the case of PBB
contamination in Michigan. Am. J. Public Health 73:302-313.
Sangster, B., J. L. Blom, V. M. Sekhuis, J. G. Loeber, A. G. Rauws, J. C.
Koedam, E. 1. Kiajnc, and M. J. van Logten. 1983. The influence of
sodium bromide in man: a study in human volunteers with special em-
phasis on the endocrine and the central nervous system. Food Chem.
Toxicol. 21:409^19.
Smith, P. K., and W. E. Hambourger. 1925. Antipyretic toxic effects of
combinations of acetanilide with sodium bromide and with caffeine. J.
Pharmacol. Exp. Ther. 55:200-206.
Thompson, R. H., and E. G. Hill. 1969. Pesticide residues in foodstuffs in
Great Britain. X. Bromide residues in maize, pulses and nuts. J. Sci.
Food Agric. 20:287-292.
Trepanier, L. A., and J. G. Babish. 1995. Effect of dietary chloride content
on the elimination of bromide by dogs. Res. Vet. Sci. 58:252-255.
Trump, D. L., and M, C. Hochberg. 1976. Bromide intoxication. Johns
Hopkins Med. J. 138:119-123.
Vaiseman, N., G. Koren, and P. Pencharz. 1986. Pharmacokinetics of oral
and intravenous bromide in normal volunteers. J. Toxicol. Clin. Toxicol.
24:403-413.
vanLeeuwen, F. X., andB. Sangster. 1987. The toxicology of bromide ion.
Crit. Rev. Toxicol. 18:189-213.
van Leeuwen, F. X., E. M. den Tonkelaar, and M. J. van Logten. 1983.
Toxicity of sodium bromide in rats: effects on endocrine system and
reproduction. Food Chem. Toxicol. 21:383-389.
van Logten, M. J., M. Wolthuis, A. G. Rauws, and R. Kroes. 1973. Short-
term toxicity study on sodium bromide in rats. Toxicology 1:321-327.
van Logten, M. J., M. Wolthuis, A. G. Rauws, R. Kroes, E. M. den
Tonkelaar, H. Berkvens, and G, J, van Esch. 1974. Semichronic toxicity
study of sodium bromide in rats. Toxicology 2:257—267.
Voss, E., A. R. Haskell, and L. Gartenberg. 1961. Reduction of tetramicine
toxicity by sedatives and anticonvulsants. J. Pharm. Sci. 50:858—562.
Vreman, K., A. H. Roos, and G. M. Tuinstra. 1985. The excretion of inor-
ganic bromide into milk of dairy cows after oral administration. Neth.
MilkDairy J. 39:173-181.
Yohn, S. E., W. B. Morrison, and P. E. Sharp. 1992. Bromide toxicosis
(bromism) in a dog treated with potassium bromide for refractory sei-
zures. J. Am. Vet. Med. Assoc. 201:468^70.
Copyright © National Academy of Sciences. All rights reserved.
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inemi Tnlemnce nf Animals' Sennnd Revised Edition
ttp7/www nap edij/ratalng/1 1 rina htmll
77
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MINERAL TOLERANCE OF ANIMALS
TABLE 8-2 Bromine Concentrations in Fluids and Tissues of Animals (mg/kg or mg/L)"
Animal
Quantity'' Source
Duration
Route
Plasma/
Serum
Muscle
Liver Kidney Milk Reference
Dogs
Rats
20 mg/kg/d KBr
300
1,200
4,800
19,200
NaBr
115d
28 d
Diet
Diet
200
16
160
647
1,998
4,474
Cattle,
10
NaBr
22 d
lactating.
19
19 d
dairy
43
28 d
10
Inorganic
39 d
19
bromide"^
39 d
43
39 d
Diet
15
33
68
8
56
van Logten et al.
96
112
1973
248
415
719
1,278
1,678
2,716
Rats
NaBr
28 d
Diet
16
' ■
^^^^ van Logten et al..
75
48
24 ■
H 1974
300
168
■
^^^^^^^^^^^^^
1,200
615
336 H
^^^^^^^^^^^^^
4,800
1,998
H
^^^^^^^^^^^1
19,200
^
^^^^
4,075 ^^^_
^^^_ 2,397
^^^^^^^^^
3
5
12
7
8
15
Lynn et al., 1963
Cattle,
22 ^M
H NaBr
30 d
Diet
21
3
4
14
6
Vreman et al.,
lactating.
69 ^^
^v
58
9
12
31
17
1985 ,
dairy
115
95
2
27
88
31
^™
"Values are on a wet weight basis.
''Quantity in mg Br/kg of feed (dry matter basis) unless otherwise noted.
"^Inorganic salts from the decomposition of methyl bromide used to fumigate the feed.
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Cadmium
INTRODUCTION
Cadmium (Cd) is a soft metal with a silver-white color. It
has an atomic number of 48, a molecular weight of 1 12.41,
and eight naturally occurring isotopes. It is a divalent 4d
transition metal with chemical properties that are similar to
zinc. The pure metal crystallizes in distorted but closely
packed structures with relatively weak bonding. Conse-
quently, it is soft enough to cut with a knife and for a metal
has a low melting point of 321°C. Cadmium has a relatively
high vapor pressure, and the vapor released from cadmium
metal quickly forms a surface oxide layer when exposed to
air. Cadmium is reactive with halides, sulfur, oxygen, and
phosphorus, but is unreactive toward carbon, hydrogen, or
nitrogen (Butterman and Plachy, 2004).
Cadmium is the 63rd most abundant element in the
Earth's crust (0.000016 percent) and is naturally found in
association with zinc and, to a lesser extent, with lead and
copper. It is extracted mainly as a by-product of zinc min-
ing and processing. In 2000, it was refined in 27 countries,
with production dominated by Asia, followed by Europe
and then North America. World production in 2000 was
19,700 metric tons, but production is declining due to an
increase in the recovery of cadmium by recycling and lower
demand because of regulatory pressure to find less toxic
substitutes (Plachy, 2002).
Cadmium forms numerous alloys and compounds with
other elements and is used in batteries, solders, semiconduc-
tors, solar cells, plastic stabilizers, and to plate iron and steel.
Cadmium salts have a wide spectrum of vivid colors and are
used as pigments in a variety of applications such as color-
ing plastics and ceramics. However, this use is declining
because of replacement by less toxic pigments. End uses for
cadmium in 2002 were batteries, 78 percent; pigments, 12
percent; coatings and platings, 8 percent; all other, 2 percent
(Plachy, 2002). Cadmium can enter the environment from a
variety of anthropogenic sources including by-products from
zinc refining, coal combustion, mine wastes, electroplating
processes, iron and steel production, pigments, fertilizers,
and sewage sludges.
Sulfate, nitrate, chloride, and acetate salts of cadmium
are very soluble in water. Cadmium oxide, hydroxide, and
sulfide have very low solubilities. Organo-cadmium com-
pounds are not known to occur in nature; however, cadmium
readily forms complexes with proteins, organic acids, and
other organic compounds.
ESSENTIALITY
Cadmium is not considered an essential nutrient for ani-
mals. However, a number of studies with rodents, chickens,
and livestock have reported increased weight gain when low
levels of cadmium were added to the diets (Bokori and
Fekete, 1995). The bases for these effects are unknown and
may be the result of antibiotic or pharmacologic actions.
Cadmium is an essential nutrient for Thalassiosira
weissflogii, a common marine diatom. In this organism cad-
mium is a cofactor for an isoform of carbonic anhydrase that
is needed under conditions of low zinc, which are typical of
many marine environments (Lane and Morel, 2000). Higher
plants have not been shown to need cadmium.
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Cadmium levels in feeds and tissues are most commonly
measured by atomic absorption spectrophotometry or
inductively-coupled atomic emission spectroscopy. Both of
these techniques have sufficient sensitivities to monitor cad-
mium levels of concern in toxicosis (ATSDR, 1999). Atomic
absorption spectrometry can detect cadmium in foods and
tissues at approximately 10 |Jg/kg. Samples are usually pre-
pared by digestion with nitric acid and microwave digestion
techniques give excellent recoveries. Dry ashing is also com-
monly used for preparing foods for cadmium analysis and little
loss of cadmium occurs at temperatures below 450°C (IPCS,
79
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MINERAL TOLERANCE OF ANIMALS
1992a). Cadmium is a relatively ubiquitous element and care-
ful attention to possible contaminating sources is needed. In
particular, colored plastics such as pipet tips can be a source of
cadmium contamination. Determining low levels of cadmium
in biological specimens requires special attention to back-
ground detection (Cerny and Bhattacharyya, 2003).
Cadmium concentrations in tissue of living animals can
be measured by neutron activation analysis or x-ray fluores-
cence. These techniques take advantage of the capture char-
acteristics of the thermal neutrons of the naturally occurring
stable isotope I'^Cd (IPCS, 1992a).
REGULATION AND METABOLISM
Absorption
Cadmium can be absorbed in toxicologically relevant
amounts from oral or inhalation exposure. Absorption by
dermal exposure is relatively insignificant unless exposure
time is very long (Wester et al., 1992). Intestinal absorption
of cadmium is relatively low compared to similar divalent
cations such as zinc and iron. Absorption of an experimental
dose of cadmium after dosage of soluble salts is about 1-2
percent in mice and rats, 0.5-3.0 percent in monkeys, 2 per-
cent in goats, 5 percent in pigs, 5 percent in lambs, and 16
percent in cattle (ATSDR, 1999). Cadmium is absorbed pre-
dominantly in the duodenum and proximal jejunum. Spe-
cific cellular importers for cadmium have not been identi-
fied, and inadvertent uptake through pathways intended for
the essential nutrients iron, zinc, manganese, and cysteine
seem to mediate cadmium transport across the brush border
(Zalups and Ahmad, 2003). For example, cadmium can be
absorbed by the divalent metal transporter- 1, which nonnally
mediates dietary iron absorption (Bressler et al., 2004). Cad-
mium bound to peptides and proteins may also enter the
enterocyte via endocytosis.
The proportion of cadmium absorbed by the intestines is
dependent on the dose, with higher doses being absorbed
more efficiently (Matsuno et al., 1991a). High levels of cad-
mium disrupt tight junctions between intestinal enterocytes
and impair epithelial barrier function (Duizer et al., 1999).
Thus, cadmium may increase its own bioavailability by caus-
ing disruption of the intestinal paracellular barrier. Absorp-
tion decreases markedly with chronic exposure (Muller et
al., 1986), apparently due to the induction of protective
mechanisms such as intraepithelial metallothionein.
The bioavailability of cadmium appears to be related to
its solubility in the digestive tract. Highly soluble salts of
cadmium, such as chloride, nitrate, acetate, and sulfate, are
absorbed much better than poorly soluble forms, such as cad-
mium sulfide and cadmium sulfoselenide pigments
(ATSDR, 1999). Cadmium bound to metallothionein or the
cadmium incorporated into pig liver is absorbed by rats less
efficiently than cadmium chloride, indicating that cadmium
in foods of animal origin may be less available than soluble
salts (Groten et al., 1990, 1994), although at low levels,
inorganic and organic forms appear to be absorbed at similar
efficiencies.
The efficiency of cadmium absorption increases with iron
or calcium deficiency (Brzoska and Moniuszko-Jakoniuk,
1998). High dietary levels of calcium, chromium, magne-
sium, or zinc decrease cadmium uptake (Foulkes, 1985).
Cadmium can also decrease the absorption of calcium and
exacerbate a deficiency (Fullmer et al., 1980).
Transport and Distribution
After absorption, cadmium is transported in the blood
bound primarily to albumin, with lesser amounts bound to
globulins, metallothionein, cysteine, glutathione, or directly
to cells (Zalups and Ahmad, 2003). It distributes throughout
the body with highest concentrations in the kidney and liver,
which account for more than half of the total body burden.
Initially, the liver takes up the highest amount of cadmium,
but over a few days cadmium in the liver is released and
taken up by the kidney. Thus, the kidney usually has the
highest concentration of cadmium of any tissue in the body.
Blood cadmium levels are indicative of recent exposure to
cadmium but are not especially indicative of total body bur-
den. Urine levels are a better indicator of total body burden
(ATSDR, 1999).
Cadmium is not transported efficiently into milk or eggs.
Little cadmium is incorporated into hair, and levels in hair
are not sensitive indicators of exposure (Combs et al., 1983).
The transport of cadmium across the placenta is also ineffi-
cient and fetal levels are considerably lower than maternal
levels (Smith et al., 1991a). Pregnant goats fed diets with
high levels of cadmium do not pass on sufficient levels of
cadmium to their kids during gestation and lactation to raise
their offsprings' tissue cadmium levels above normal
(Telford et al., 1984b).
Cadmium (+2) readily complexes to anionic groups, es-
pecially sulfhydryl groups, in proteins and other molecules.
Metallothionein, a low molecular weight protein that is very
high in cysteine, is capable of binding up to seven cadmium
atoms per molecule. Cadmium is a strong inducer of
metallothionein synthesis and cadmium also decreases the
degradation rate of this intracellular chelator (Laurin and
Klasing, 1990). Cadmium displaces zinc and copper from
previously synthesized metallothionein. Metallothionein is
important in modulating the fate of cadmium in tissues by
affecting the duration of its retention in tissues and reducing
its cellular toxicity (Klaassen and Liu, 1998). The kidney is
a major site of metallothionein synthesis and consequently
accumulates cadmium.
Excretion
Absorbed cadmium is excreted slowly with daily losses
of approximately 0.009 percent of the total burden via the
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CADMIUM
81
urine and 0.007 percent via feces. Most of the cadmium loss
into ttie intestines is derived from iiepatocellular secretion of
cadmium into bile. Circulating cadmium-protein complexes
are filtered at the glomerulus and then resorbed from the
glomerular filtrate by the cells in the SI and S2 segments of
the proximal convoluted tubules (Dorian et al., 1995). This
region of the renal cortex concentrates cadmium and is sus-
ceptible to necrosis. The half-life of cadmium in rodents is
very long and estimates vary from several months to a year or
more (ATSDR, 1999). In beagles, the biological half-life of
cadmium fed at either 1, 3, 10, or 50 mg/kg diet is between 1
and 2 years (Matsuno et al., 1991b). Because of this low excre-
tory rate, cadmium accumulates with age, and older animals
have significant levels of cadmium in their kidneys even if the
levels in their diets and water were consistently low.
Mechanism of Toxicity
The toxic effects of cadmium are thought to be caused by
free cadmium ions, and cadmium bound to metallothionein
is usually less active (Goyer et al., 1989). Specific mecha-
nisms of toxicity vary according to cadmium concentration
and cell type but generally are linked to cadmium's disrup-
tion of the cellular redox state and to its structural similari-
ties with zinc, calcium, and other divalent cations (Pinot et
al., 2000). The redox activity of cadmium depletes antioxi-
dants and glutathione, causes oxidative stress, enhances lipid
peroxidation, and perturbs the lipid composition of mem-
branes (Gill et al., 1989; Xu et al., 2003). Cadmium affects
the function of glomerular membranes by depleting
polyanions and interfering with membrane charge (Cardenas
et al., 1992). Cadmium-induced reactive oxygen intermedi-
ates can lead to decreased DNA synthesis and strand breaks.
Cadmium ions displace zinc and other metals from the
binding sites of many metalloproteins, perturbing their ar-
chitecture and functions. In the testes, cadmium interferes
with zinc -protein transcription factors leading to apoptosis
(Xu et al., 1999). Cadmium binding to metal transcription
elements induces expression of a variety of genes including
metallothionein, heme oxygenase, and heat shock proteins.
Cadmium also has estrogenic effects by binding to the estro-
gen receptor (Stoica et al., 2000), causing reproductive dis-
ruption and accelerated puberty in mammals (Johnson et al.,
2003). Cadmium may permeate or block calcium channels
and acts to mobilize free-calcium in the cell, causing cell-
specific disregulation in function.
Mitochondria are especially susceptible to cadmium tox-
icity. Cadmium binds to thiol groups of proteins in the mem-
brane of this organelle. Thiol group inactivation leads to
oxidative stress and membrane depolarization. Impairment
in mitochondrial function results in ATP depletion and ne-
crotic death of the cell. In some cell types, cadmium-induced
leakage of mitochondrial enzymes leads to apoptotic death
(Pinot et al., 2000). Thus, depending on the cell type, cad-
mium may cause either necrotic or apoptotic cell death.
SOURCES AND BIOAVAILABILITY
Sources
Cadmium is sparsely distributed in the environment and
normally ranges in concentrations between 0.1 and 1 mg/kg
in the Earth's crust (Blinder, 1992). Levels 10- to 20-fold
higher may accumulate in some types of sedimentary rocks.
Levels in the oceans range from 0.001 to 0.1 |Jg/L, with
higher levels found in phytoplankton-rich areas. Levels in
natural surface and ground water are usually less than 1 |Jg/L
(ATSDR, 1999; Pinot et al., 2000). However, spillage or
leaching of water from mines can contaminate surface or
ground waters, resulting in much higher levels. Levels in
topsoil are usually higher than in subsoils due to atmospheric
fallout and contamination. Unpolluted soils in the United
States contain an average of 0.25 mg/kg (EPA, 1985). Higher
concentrations of cadmium usually result from human ac-
tivities such as mining, smelting, fuel combustion, and dis-
posal of batteries and other cadmium-containing products.
For example, soil levels within 1 kilometer of a smelter were
72 mg/kg, compared with 1.4 mg/kg between 18 and 60 ki-
lometers away. In 1998, there were 776 hazardous waste sites
in the United States with focally high levels of cadmium
contamination; animals grazing near these sites may con-
sume high levels of cadmium via food or water.
The most likely source of high cadmium exposure for
most animals kept in captivity is the mineral supplement used
in the feed. In particular, phosphate and zinc sources can be
important contributors (King et al., 1992; Linden et al., 1999;
Nicholson et al., 1999; Sapunar-Postruznik et al., 2001; Lin-
den et al., 2003). Natural cadmium levels found in phos-
phates from sedimentary rocks range from 3 to 100 mg/kg,
depending upon their location (Singh, 1994). Phosphates
from the southeastern United States have approximately 35
mg/kg (IPCS, 1992a). Analysis of 16 calcium phosphates
used in animal feeds in the United States found cadmium
levels ranging from <1 to 67.3 mg/kg (Sullivan et al., 1994).
Calcium phosphate is often added to animal feeds at levels
greater than 1 percent of the diet, which can result in dietary
cadmium levels that are high enough to cause unacceptably
high levels in livers and kidneys intended for human
consumption.
Cadmium accumulates in plants grown in high-cadmium
soils. Its mobility and bioavailability to plants is highest in
acid soils. Cadmium taken up by plants is concentrated in
the leaves with lower levels in seeds and roots (He and Singh,
1994), so grazing animals receive the highest exposure
(Hansen and Hinesly, 1979). Application of manure, sewage
sludge, or phosphate fertilizers can enrich soils in cadmium.
Consequently, limits on the maximum cadmium concentra-
tion in fertilizers and biosolids applied to land, the maximal
loading rate (kg/ha/y) of cadmium applied to land, and moni-
toring procedures are set by the EPA and many state agen-
cies (ATSDR, 1999; NRC, 2002).
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MINERAL TOLERANCE OF ANIMALS
In aquatic and benthic environments, cadmium concen-
trations are relatively uniform tliroughiout tlie food web and
cadmium does not appear to biomagnify as it moves up the
food chain. In freshwater, the cadmium level in animals is
dependent on their ability to absorb it from the water rather
than their trophic level (IPCS, 1992b).
Cadmium levels in human foods are highest in shellfish,
oysters, salmon, and fungi, and are lowest in fruits, dairy
products, legumes, meat, and poultry, with the exception of
liver and kidney products . Potatoes and leafy vegetables have
higher cadmium levels than most other foods of plant origin
(ATSDR, 1999).
The toxicity of cadmium is well recognized, and its con-
centrations are monitored and regulated by a wide variety of
government agencies (ATSDR, 1999). Cadmium is consid-
ered a hazardous waste, and the EPA regulates levels in in-
dustrial and municipal wastewaters, sewage sludge, and air
emissions. State public health departments or departments
of natural resources monitor cadmium levels in fish and wild-
life that are potentially consumed and issue advisories to
limit or prevent consumption of species of concern found in
contaminated environments. The World Health Organization
has set a 1 mg/kg upper limit for cadmium in complete feeds
for animals in order to prevent high levels in food products
(IPCS, 1992a).
Bioavailability
The bioavailability of various chemical forms of cadmium
is dependent upon its chemical form. Cadmium is likely to
be in the free ionic form in fresh water, whereas in foods it
generally exists in a complex with a variety of ligands, in-
cluding proteins such as metallothionein. The toxicological
properties of cadmium ions do not seem to be dependent on
the anion present. Cadmium chloride is the most common
form used in animal experimentation because it is highly
soluble and has a high bioavailability. In general, the
bioavailability of cadmium chloride supplemented to water
is similar to that supplemented to food (Ruoff et al., 1994).
The cadmium found in a commercial calcium phosphate was
found to be somewhat less bioavailable than cadmium chlo-
ride to pigs (King et al., 1992). The bioavailability of cad-
mium in animal tissues is usually less than that of cadmium
chloride. For example, cadmium-metallothionein and cad-
mium in pig liver have lower bioavailabilities and toxicities
than cadmium chloride (Groten et al., 1990, 1994). The
bioavailability of cadmium in horse kidney is lower than that
of cadmium chloride and is not affected by cooking (Lind et
al., 2001). The cadmium in the hepatopancreas of crab has
lower bioavailability than cadmium chloride (Lind et al.,
1995). The decreased bioavailability of cadmium associated
with high protein foods may be due to the ability of undi-
gested oligopeptides to decrease the amount of free cadmium
available to be absorbed from the intestine by complexing
cadmium (Kojima et al., 1985). The bioavailability of
cadmium in foods of plant origin such as mushrooms and
lettuce is similar to that in cadmium salts (McKenna et al.,
1992; Lind et al., 1995). Phytate, which decreases the
bioavailability of many divalent cations, appears to increase
cadmium bioavailability to rats (Rimbach et al., 1995).
The bioavailability of cadmium in water to aquatic organ-
isms decreases with increasing organic carbon and oxygen-
ation. Dissolved organic matter and particulates may absorb
and render unavailable substantial amounts of cadmium. For
these reasons, the effective cadmium content of water is of-
ten expressed as the dissolved metal concentration, which is
defined as the amount of metal in solution that passes through
a 0.45 pm filter (EPA, 2001). Bioavailability of cadmium to
aquatic organisms in freshwaters decreases with increasing
water hardness and especially calcium content. In saltwaters
with salinities above 10 g/kg, insoluble complexes of cad-
mium chloride predominate and these are of considerably
lower availability than ionic cadmium (Kramer et al., 1997).
Thus, toxicity thresholds for aquatic animals must be inter-
preted in the context of the characteristics of the water.
TOXICOSIS
Repeated exposure of humans to excessive levels of
cadmium-containing dust or fumes, found usually at
cadmium-producing and/or -consuming factories, can have
irreversible effects on kidneys and lead to reduced lung ca-
pacity and emphysema. High levels of cadmium in dust and
soils found in or near toxic waste sites may also pose an
inhalation threat, but this route of exposure is not likely to be
of concern in animal husbandry and is not considered in this
report. Toxicological profiles following exposure by this
route have been extensively reviewed (IPCS, 1992a; Jarup et
al., 1998; ATSDR, 1999).
Virtually all major organ systems are affected by chronic
consumption of foods or water containing high levels of cad-
mium, with the kidney and the liver as the primary target or-
gans in most species (Swiergosz-Kowalewska, 2001). Usu-
ally, nephrotoxicity is the primary pathology leading to initial
signs of toxicosis. Cadmium causes damage to proximal tu-
bule cells and interstitial fibrosis in the kidney cortex, result-
ing in proteinuria, glycosuria, amino aciduria, and polyuria. In
dogs, mesangium cells of the glomerulus also become necrotic
and the glomerular basement membrane thickens in rats. Cad-
mium causes renal damage in rats when its concentration in
the kidney is 10 mg/kg regardless of the type of cadmium
complex that is administered (Min et al., 1986).
Histopathological changes in the liver induced by chronic
cadmium exposure include intralobular fibrosis, cirrhosis,
focal mononuclear infiltration, and proliferation of the
smooth endoplasmic reticulum. A mild osteomalacia has fre-
quently been reported after chronic cadmium exposures. This
may be due to direct effects on the turnover of bone matrix
by stimulation of bone remodeling pathways (Regunathan et
al., 2002), though it can also be secondary to decreased cal-
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CADMIUM
83
cium and phosphorus absorption (Sugawara and Sugawara,
1974). The effect on bone is exacerbated by multiparity
(Whelton et al., 1994). In multiparous mice, decreased bone
calcium is a more sensitive indicator of cadmium toxicosis
than changes in renal function, but this is not seen in
nonreproducing females (Bhattacharyya et al., 1988a). Ane-
mia is also a commonly reported sign of cadmium toxicosis,
though it may be secondary to decreased iron absorption.
Cadmium causes decreased hematopoiesis and the resulting
anemia is often one of the first detectible changes in toxico-
sis. Cadmium-induced infertility, pancreatic necrosis, and
decreased immunocompetence also contribute to the toxic-
ity profile of cadmium. After withdrawal of cadmium, tissue
cadmium levels decay only very slowly, and the signs of
toxicosis require a half year or more to resolve (Nomiyama
and Nomiyama, 1984).
Because cadmium is poorly excreted and builds up over
time, animals with higher rates of food intake appear to be
affected at lower levels of dietary cadmium than animals
with lower food intakes. Thus, the dietary concentration at
which cadmium becomes toxic appears to be higher in small
animals, such as rodents and quail, than in larger animals,
such as monkeys and pigs, because mass-specific metabolic
rate and food intake decrease with body size.
In experimental animals, cadmium is carcinogenic after
oral exposure. This is due to cadmium's prooxidant proper-
ties, effects on cell proliferation, differentiation, and
apoptosis, aberrant activation of protooncogenes, and inhi-
bition of DNA repair and DNA methylation (Waalkes, 2003;
Waisberg et al., 2003). In humans, occupational exposure by
inhalation of cadmium dusts and fumes has been related to
lung cancer; however, carcinogenic activity in human popu-
lations exposed to high dietary levels of cadmium is not well
documented by epidemiological studies (Pinot et al., 2000;
Satoh et al., 2002). In 1993, cadmium was classified as a
human carcinogen by the International Agency for Research
on Cancer. Cadmium is teratogenic in birds and mammals
(ATSDR, 1999; Kertesz and Fancsi, 2003).
The rate of cadmium accumulation in the kidney and liver
of rats is very similar for soluble cadmium delivered via the
feed versus the water. When cadmium dosage is expressed
on a daily intake basis (mg/kg BW/day), toxicity does not
differ between food and water exposure (Ruoff et al., 1994).
Because the data on the toxicity of cadmium in water are
very limited in terrestrial animals other than rodents, it is
useful to assume that intakes determined to be toxic when
consumed in feeds are appropriate for estimating toxicity of
cadmium in water.
Toxicity of cadmium to fish and aquatic invertebrates is
variable across species. Among fish, salmonids are particu-
larly sensitive (EPA, 2001). Cadmium interferes with cal-
cium uptake from water and causes hypocalcemia, malfor-
mations of the spine, and infertility. The most sensitive life
stages are the embryo and early larva. The EPA has con-
ducted an extensive review of the published literature on
cadmium toxicity to 125 species of aquatic animals (EPA,
2001). Table 9-1 includes data from some of the studies on
economically important species; however, the EPA docu-
ment should be consulted for additional information. The
acute toxicity of cadmium to freshwater fish is highly depen-
dent on the hardness of the water. For example, the LC 50 of
cadmium chloride to rainbow trout is 0.83 |Jg/L of cadmium
at 30 mg/L hardness, but 5.23 pg/L at 90 mg/L hardness
(Hansen et al., 2002a). Water used in aquaculture normally
has a hardness considerably >50 mg/L. Because water hard-
ness has such a marked impact on cadmium toxicity in
aquatic environments, EPA toxicity criteria are standardized
to a hardness of 50 mg/L and include a regression equation
to adjust for other water hardness values.
Studies on cadmium toxicity to animals since 1979 are
listed in Table 9-1. Studies before 1980 are summarized in
the previous version of this publication (NRC, 1980). Only
selected studies in mice and fish are provided in Table 9-1,
but thorough reviews of this extensive literature are avail-
able elsewhere ( IPCS, 1992a,b; ATSDR, 1999; EPA, 2001).
Single Dose
Numerous human and animal studies indicate that a single
oral dose of cadmium causes severe irritation to the gas-
trointestinal epithelium (Andersen et al., 1988). Symptoms
include nausea, vomiting, salivation, abdominal pain, and
diarrhea (ATSDR, 1999). Desquamation and necrosis of the
gastric and intestinal mucosa and dystrophy of the liver,
heart, and kidneys are the primary pathological indications
(Tarasenko et al., 1974). The single oral dose LD^q for cad-
mium in rodents is dependent on the solubility of the source.
Cadmium oxide and the highly soluble sulfate, chloride,
nitrate, and iodide salts of cadmium have an LD^q of about
50 mg Cd/kg BW, whereas insoluble cadmium metal and
cadmium sulfide have an LD^q of about 900 mg/kg BW in
mice (ATSDR, 1999). A single oral dose of 15.7 mg Cd/kg
BW as cadmium chloride in water to mice does not cause
histopathology of the stomach or liver (Andersen et al.,
1988).
Acute
In rats, an acute dose of cadmium (30 mg/kg BW/day)
administered by gavage causes severe necrosis, hemorrhage,
and ulcers in the gastrointestinal epithelium (Andersen et al.,
1988; Basinger et al., 1988). The pain of the gastroenteritis
induced by high cadmium intake usually limits consumption
and limits toxicity. In Japanese quail, feeding a diet contain-
ing 75 mg/kg cadmium as cadmium sulfate results in de-
creased egg production within 10 days of exposure (Bokori
et al., 1995). In chickens, 50 mg/kg cadmium in the diet as
cadmium chloride impairs egg production and egg weight
(Hennig et al., 1968).
The EPA (2001) has summarized all studies that examined
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MINERAL TOLERANCE OF ANIMALS
the acute toxicity of cadmium for more tfian 100 species of
aquatic animals and then calculated the geometric mean toxic-
ity for individual species (Species Mean Acute Value, or
SMAV). These SMAV for cadmium are based on mortality
(LC 50) and range from 1 1,859 |Jg/L for crayfish to 1.6 |ig/L
for brown trout. The SMAV for other economically important
freshwater animals are tilapia, 10,633; channel catfish, 5,055;
common carp, 4,238; coho salmon, 6.2; rainbow trout, 2.1;
striped bass, 2.9; and brook trout, 1 .8 |Jg/L. All of these values
are adjusted to a water hardness of 50 mg/L. Tolerance to
cadmium increases with increasing hardness with a slope of
1.01; consequently fish in water with a hardness of 200 mg/L
will be about four times less sensitive (EPA, 2001).
Cadmium is much less toxic in saltwater than freshwater,
and coho salmon have a SMAV of 1 ,500 |Jg/L when raised in
saltwater compared to 6.2 |ig/L in freshwater. The SMAV
for other saltwater species are sheepshead minnows, 50,000;
striped mullet, 7,079; blue crab, 2,594; Pacific oyster, 228;
American lobster, 78; and striped bass, 75 |Jg/L.
Chronic
Ruminants including cattle, sheep, and goats have been
fed crops grown in high-cadmium soils or diets supple-
mented with sewage sludge resulting in dietary cadmium
levels of up to 13 mg/kg dry matter (Tables 9-1 and 9-2). In
these studies, decreased performance was not reported and
in some cases performance increased. Goats fed 28.5 mg/kg
cadmium as cadmium chloride did not have significant
changes in growth, feed intake, feed efficiency, or organ
weights (Combs et al., 1983). A diet containing 10 mg/kg
cadmium from cadmium chloride did not influence milk pro-
duction in Holstein cows, but only four animals were used
per treatment level (Sharma et al., 1979). A diet containing
40 mg/kg cadmium from cadmium chloride did not influ-
ence feed intake of calves, but 160 mg/kg resulted in de-
creased feed intake (Powell et al., 1964). Unfortunately, sen-
sitive measures of toxicosis, such as renal pathology or
proteinuria, have not been measured in ruminants so a
LOAEL cannot be accurately determined, but 10 mg/kg dry
matter seems to be well tolerated using growth and general
health as criteria. Several experiments have examined the
effects of cadmium chloride in the water on sheep. In one
experiment, cadmium at 3 mg/kg BW resulted in decreased
testes weight, decreased semen volume, and lesions in the
Sertoli cells, seminiferous tubules, and primary and second-
ary spennatocytes (Lymberopoulos et al., 2000). Cadmium
at 2.6 mg/kg BW given in water to lactating ewes resulted in
pathological changes in the liver, kidney, and mammary
gland.
Among nonruminants, pigs fed 10 mg/kg cadmium from
cadmium chloride have normal growth rates, but those fed
50 mg/kg develop anemia (Cousins et al., 1973, Sharma et
al., 1979). Dogs given 5 mg/L cadmium in water for 4 years
develop signs of glomerular and tubular pathology, but those
given 2.5 mg/L are normal (Anwar et al., 1961). Functional
indications of cadmium toxicosis in rats and mice, such as
increased blood pressure, have been observed at levels as
low as 1 mg/kg diet, although most studies do not report
changes at this level. Indications of pathology in the kidney
or other tissues occur at 5 mg/kg diet, and decreased growth
rates occur at about 30 mg/kg diet or 30 mg/L water (IPCS,
1992a,b; ATSDR, 1999). In monkeys, a diet containing 3
mg/kg cadmium did not cause any pathological or histo-
pathological effects after 9 years, but 10 mg/kg resulted in
decreased body weights (Masaoka et al., 1994). In another
study, rhesus monkeys given 5 mg/kg cadmium BW/day
orally developed renal failure and increased urinary excre-
tion of total protein if they concurrently suffered from pro-
tein calorie malnutrition (Prasad and Nath, 1995). Dogs fed
cadmium at 1,3, 10, and 30 mg/kg from cadmium chloride
for 3 months were clinically normal and did not have histo-
pathological evidence of hepatic or renal damage (Loeser
and Lorke, 1977). However, dogs fed 50 mg/kg of dietary
cadmium from cadmium chloride for 8 years had renal atro-
phy and renal tubule degeneration (Hamada et al., 1994) and
diminished renal function (Kodama et al., 1992). Cadmium
at 15 mg/L in the drinking water of ovariectomized beagles
induced bone loss over a 7-month period (Bhattacharyya et
al., 1992; Sacco-Gibson et al., 1992).
Diets containing cadmium at 10 mg/kg do not decrease
gain or cause anemia when fed to chickens, ducks, or quail.
A diet containing cadmium at 20 mg/kg resulted in anemia
and increased serum glutamic-pyruvate transaminase in mal-
lards (Cain et al., 1983). Laying hens fed 3 mg/kg cadmium
as cadmium sulfate had increased egg production, whereas
those fed 12 mg/kg had decreased egg production in one
experiment and decreased egg shell thickness in a second
experiment (Leach et al., 1979). Broiler chickens fed 25 mg/
kg cadmium from cadmium sulfate develop focal fatty infil-
tration of the liver, histiocytic infiltration of the jejunal mu-
cosa, focal lymphohistiocytic interstitial infiltration, and fi-
brosis of the kidney (Bokori et al., 1996).
In fish, growth rate is not a good indicator of chronic
toxicity. For example, female rainbow trout grow at a nor-
mal rate when exposed to high levels of cadmium in the
water, but their sexual development is markedly impaired
and any eggs that are produced are sterile (Brown et al.,
1994). Unfortunately, the majority of toxicity studies in fish
use growth rate and mortality as the primary endpoints.
Based on the available literature, EPA has calculated mean
chronic toxicity levels for a variety of aquatic animals (Mean
Chronic Value, or MCV). The MCV for freshwater fish are
tilapia, >23.6; smallmouth bass, 8.1; Atlantic salmon, 7.9;
brook trout, 2.6; coho salmon, 4.2; and rainbow trout, 1.3
|jg/L. All of these values are adjusted to a water hardness of
50 mg/L. In these chronic studies, tolerance to cadmium in-
creases with increasing hardness with a slope of 0.74. Con-
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CADMIUM
85
sequently, fish in water with a hardness of 200 mg/L will be
about three times less sensitive (EPA, 2001).
Factors Influencing Toxicity
The toxicity of cadmium is affected by the nutritional and
physiological state of an animal. In Japanese quail, deficien-
cies of zinc, iron, copper, calcium, or protein increase the
tissue accumulation and toxicity of cadmium (Fox et al.,
1979, 1984). In rodents, physiological states that induce an
increase in iron absorption, such as a fast growth rate or preg-
nancy, increase cadmium absorption and toxicity (Schafer et
al., 1990, Waalkes 1986). In humans, adult females absorb
more cadmium than males, and this is at least partially due to
higher incidence of anemia in females (Choudhury et al.,
2001). Low dietary calcium increases cadmium absorption
and accumulation in tissues leading to cadmium toxicosis at
lower levels than in well-nourished animals (Brzoska and
Moniuszko-Jakoniuk, 1998). Furthermore, cadmium inter-
feres with the metabolic functions of calcium, magnifying
the deficiency. A similar situation occurs with zinc (Brzoska
and Moniuszko-Jakoniuk, 2001). Age also is an important
factor: in rats, cadmium is absorbed at higher rates in im-
mature animals than in adults (Foulkes et al., 1991). Kidney
damage from causes unrelated to cadmium toxicity, such as
diabetes and old age, are expected to increase the sensitivity
to nephrotoxicity caused by cadmium (Buchet et al., 1990).
Cadmium toxicity can be markedly (>80 percent) reduced
by high levels of several minerals, especially calcium, phos-
phate, zinc, or iron (Groten et al., 1991). For example, a high
level of dietary calcium decreases absorption and decreases
the toxicity of absorbed cadmium (Brzoska and Moniuszko-
Jakoniuk, 1998). Zinc protects against cellular toxicity of
cadmium by reducing the accumulation of cadmium in cells
and also by inducing metallothionein (Kaji et al., 1988). High
levels of dietary zinc ameliorate the inhibition in egg pro-
duction caused by cadmium in the diet of laying hens (Nolan
and Brown, 2000). High intakes of vitamin E also reduce the
development of toxicosis in growing chickens (Gupta and
Kar, 1999), as does cysteine (Czarnecki and Baker, 1982).
For aquatic organisms, the toxicity of cadmium decreases
with increasing salinity of the water. The complexing of ionic
cadmium with chloride and the high level of calcium in sea-
water decrease cadmium absorption (Engel and Fowler,
1979). Thus, the accumulation and toxicity of cadmium for a
given species can be several orders of magnitude lower in
ocean environments than freshwater environments. The pro-
tective effect of calcium has been attributed to the lower
toxicity of cadmium in hard water than in soft water (Gill
and Epple, 1992; Brzoska and Moniuszko-Jakoniuk, 1998).
Consequently, animals in saltwater environments receive
most of their cadmium from their food, whereas those in
freshwater obtain important amounts of cadmium from both
food and water (IPCS, 1992b).
TISSUE LEVELS
Cadmium accumulation is greatest in the kidney, fol-
lowed by liver, testes, pancreas, and spleen. Muscle and bone
do not accumulate cadmium at high levels (Table 9-2). There
are no major differences in the amount of cadmium that ac-
cumulates across different types of muscles. Tissue levels
increase with the time of exposure; when dietary levels are
high, tissue levels eventually reach a plateau. For example,
in ducks fed 20 mg/kg cadmium, muscle cadmium increases
from 0.006 to 0.025 mg/kg fresh tissue during the first 30
days and then further increases to 0.077 mg/kg during the
next 30 days, but does not increase further thereafter (White
et al., 1978). The plateau in muscle usually occurs relatively
rapidly (months), but cadmium in kidney and liver accumu-
lates over a much longer period of time. Once elevated lev-
els of cadmium have accumulated, the withdrawal of cad-
mium from the feed for a month or more does not result in
appreciable loss of cadmium from tissues (White and Finley,
1978; Sharma et al., 1979; Baxter et al., 1982).
Phosphate sources used in animal diets are likely sources
of cadmium contamination. In one study with pigs, a rock
phosphate that contained an exceptionally high level of natu-
ral cadmium contamination (100.3 mg/kg) was incorporated
into growing and finishing feeds to provide 1.2 mg/kg cad-
mium final feed. Pigs fed this diet to a 90-kg slaughter weight
did not have detectable levels of cadmium in their muscle or
fat (<0.3 mg/kg dry weight), but their livers and kidneys
contained 0.35 and 1 .68 mg/kg, respectively (King et al., 1992).
The relationship between cadmium intake and the con-
centration in the liver and kidneys of rats is linear over a
very wide range (Ruoff et al., 1994). At realistic levels of
intake (<10 |Jg/kg BW/day), the slope of the relationship be-
tween intake and tissue cadmium (wet weight) is 0.11 for
kidney cortex and 0.04 for liver. Several dietary factors can
modify the amount of cadmium that accumulates in tissues.
High levels of dietary zinc, calcium, or cysteine decrease
accumulation (Czarnecki and Baker, 1982; Lamphere et al.,
1984).
In fish, the deposition of cadmium is usually highest in
the gills and kidney, with lower levels in the liver. More than
90 percent of the total whole body cadmium in rainbow trout
exposed to high levels of cadmium is found in these three
tissues (Kay et al., 1986). Experiments examining cadmium
accumulation from the water typically use water with suffi-
cient hardness to prevent acute toxicity and mortality in
the fish.
Cadmium transfer from the laying hen to the egg is very
inefficient. Hens with very high cadmium burdens (100 mg/
kg in liver) lay eggs with undetectable levels of cadmium in
the albumen and approximately 0.1 mg/kg dry weight in the
yolk (Sato et al., 1997; Leach et al., 1979). Cadmium trans-
fer to milk is similarly inefficient (Sharma et al., 1979; Smith
et al., 1991b). Feeding heifers a diet containing 5 mg/kg cad-
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86
MINERAL TOLERANCE OF ANIMALS
mium for more than a year before parturition and tlirougfiout
lactation did not result in significantly elevated milk cad-
mium levels during any part of lactation. Using radioactive
cadmium, it was found that most cadmium in milk is bound
to casein, with lesser amounts bound to albumin and lactose,
and none detectable in fat (Van Bruwaene et al., 1982).
Regardless of the level of cadmium fed, the concentration
of cadmium in meat, milk, and eggs is always lower than the
level in the diet that the animal consumed (on a dry matter
versus dry matter basis). Thus, foods derived from these
products decrease exposure of humans to environmental cad-
mium. However, levels in kidney and liver are always con-
siderably higher than the levels in the diet and these tissues
magnify environmental cadmium (Morcombe et al., 1994).
Kidneys can make their way into a variety of human
foods. The kidneys of poultry are located in recesses of the
sacrum and ilium and remain with the carcass after the rest
of the viscera are removed during processing. After egg pro-
duction ceases, hens are usually more than 1 year old and
have kidney cadmium levels of 0.80 mg/kg (Murphy et al.,
1979). In the United States, mechanically deboned meat
made from the frames of spent hens was found to contain
0.02 mg/kg (Murphy etal., 1979). However, if only the back,
which contains the kidneys, was used to make mechanically
deboned poultry meat, the cadmium concentration would be
0.096. Consequently, a regulation was issued by the Food
Safety and Inspection Service requiring the removal of kid-
neys from mature chickens and turkeys at slaughter. How-
ever, the value of this requirement has been questioned based
on surveys of cadmium levels in products (Vos et al., 1990).
Mechanically deboned meat from broilers should not be a
problem. Broilers, which are usually marketed at approxi-
mately 6-7 weeks of age, have 0.05 mg/kg cadmium in their
kidneys and <0.005 mg/kg fresh weight in their muscle
(Murphy et al., 1979).
MAXIMUM TOLERABLE LEVELS
The MTL of cadmium is defined as the dietary level that,
when fed for a defined period of time, will not impair ac-
cepted indices of animal health or performance. Animals are
able to tolerate acute exposure to 25 mg/kg cadmium in the
diet for a few days. Subtle histological signs of toxicosis in
rodents occur after chronic consumption of 1 mg cadmium/
kg diet for several months. Dietary levels of 10 mg/kg are
tolerated chronically by poultry and livestock species, but
these levels result in unacceptable levels of cadmium in kid-
neys, livers, and, in some cases, muscles of animals. Rhesus
monkeys can tolerate 3 mg/kg diet for 9 years without signs
of pathology. Dogs can tolerate 10 mg/kg diet for 8 years.
The toxicity of cadmium in water appears to be very similar
to that in feeds. For this reason, the total daily intake of both
feed and water sources should be considered. The toxicity of
cadmium to fish is extremely variable with trout being the
most susceptible. Cadmium at a level of 1 |Jg/L is tolerated
by all species in all water conditions. With hard water, trout
and all other species tested can tolerate 4 |Jg/L.
HUMAN HEALTH
Animals are able to tolerate levels of cadmium in their
diet that result in accumulation of cadmium in their kidneys
and livers at concentrations that are of concern for humans
consuming foods made from these organs. Consequently,
maximum dietary levels in the feed of animals used for
human food should be set on the basis of human health and
not animal health.
Based on residue levels, the World Health Organization
has set a 1 mg/kg upper limit for cadmium in complete feeds
for animals (IPCS, 1992a).
FUTURE RESEARCH NEEDS
The level of cadmium in the diet of agriculturally impor-
tant animals should be based on cadmium content of tissues
used as human foods and not on the maximum tolerable level
for the animal itself. Few studies have examined the dose-
response relationship between dietary cadmium and tissue
cadmium in production animals at levels <1 mg/kg diet.
Better definition of the dose-response relationship is required
to establish the maximal tolerable levels of cadmium in ani-
mal feeds based on residue levels. Because cadmium accu-
mulates over many years, examining this relationship in rela-
tively long-lived animals such as dairy cattle and laying hens
is especially needed.
Toxicity of cadmium to aquatic species has mainly uti-
lized growth rate and mortality as endpoints. Use of more
sensitive criteria such as pathological changes in kidneys,
gills, and liver is needed to define more precisely chronic
toxicities. Cadmium tolerance and signs of toxicosis in com-
panion animal species have not been investigated. Given the
high proportion of kidney and liver tissues in meat meals
that are commonly fed to these species, investigation is
warranted.
SUMMARY
Cadmium is industrially valuable for batteries, pigments,
and coatings. It enters the environment by a wide variety of
anthropogenic means and may also be high in phosphate and
zinc supplements fed to animals. Cadmium is known to be
essential in diatoms, but essentiality has not been established
in animals. Cadmium is not absorbed very efficiently, but
once it enters the body, it is excreted very slowly and accu-
mulates according to lifetime exposure. The bioavailability
of cadmium is mostly similar across feed types and is also
similar between feed and water. High intakes of cadmium
from the feed or from water can cause decreased growth
rates, anemia, kidney damage, osteomalacia, infertility, and
hypertension. High dietary cadmium can also interfere with
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CADMIUM
87
the absorption and metabolism of other nutrients, especially
zinc and calcium. Cadmium accumulates to very high lev-
els in the kidney and liver. This accumulation limits the
safe levels of cadmium that can be fed to animals destined
for human consumption. Cadmium is not transferred effi-
ciently to milk or eggs, and these foods have much lower
levels of cadmium than those found in the diet of the cow
or hen. Levels in muscle are also lower than dietary levels.
Further research is needed to determine the dose-response
relationship between dietary cadmium at low levels of
supplementation and the levels in tissues destined for hu-
man consumption.
REFERENCES
Allen, P. 1995. Clironic accumulation of cadmium in the edible tissues of
Oreochromis aureus (Steindachner): modification by mercury and lead.
Arch. Environ. Contam. Toxicol. 29:8-14.
Andersen, O., J. B. Nielsen, and P. Svendsen. 1988. Oral cadmium chloride
intoxication in mice: effects of dose on tissue damage, intestinal absorp-
tion and relative organ distribution. Toxicology 48:225-236.
Anwar, R. A., R. F. Langham, C. A. Hoppert, B. V. Alfredson, and R. U.
Byerrum. 1961. Chronic toxicity studies. III. Chronic toxicity of cad-
mium and chromium in dogs. Arch. Environ. Health 3:456^60.
ATSDR (Agency for Toxic Substances and Disease Registry). 1999. Toxi-
cological profile for cadmium. Atlanta, GA: U.S. Department of Health
and Human Services, Public Health Service.
Bache, C. A., G. S. Stoewsand, and D. J. Lisk 1986. Cadmium in tissues of
Japanese quail fed oat grain grown on municipal sludge-amended soil.
J. Toxicol. Environ. Health 18:315-319.
Basinger, M. A., M. M. Jones, M. A. Holscher, and W. K. Vaughn. 1988.
Antagonists for acute oral cadmium chloride intoxication. J. Toxicol.
Environ. Health 23:77-89.
Baxter, J. C, B. Barry, D. E. Johnson, and E. W. Klienholz. 1982. Heavy
metal rention in cattle tissues from infestation of sewage sludge. J.
Environ. Quaf 11:616-620.
Bentley, P. J. 1991. Accumulation of cadmium by channel catfish (Ictalurus
punctatus): influx from environmental solutions. Comp. Biochem.
Physiol. C. 99:527-529.
Berry, N. R., R. F. E. Axford, I. Ap Dewi, P. C. Chiy, and C. J. C. Phillips.
1999. The effect of a to w dose of cadmium on spermatogenesis in rams.
Small Ruminant Res. 31:97-102.
Bhattacharyya, M. H., B. D. Whelton, D. P. Peterson, B. A. Carnes, M. S.
Guram, and E. S. Moretti. 1988a. Kidney changes in multiparous mice
fed a nutrient- sufficient diet containing cadmium. Toxicology 50:
205-215.
Bhattacharyya, M. H., B. D. Whelton, D. P. Peterson, B. A. Carnes, E. S.
Moretti, J. M. Toomey, and L. L. Williams. 1988b. Skeletal changes in
multiparous mice fed a nutrient- sufficient diet containing cadmium.
Toxicology 50:193-204.
Bhattacharyya, M. H., N. A. Sacco-Gibson, and D. P. Peterson. 1992. Cad-
mium-induced bone loss: increased susceptibility in female beagles af-
ter ovariectomy. lARC Sci. Publ. 279-286.
Bokori, J., and S. Fekete. 1995. Complex study of the physiological role
of cadmium. I. Cadmium and its physiological role. Acta Vet. Hung.
43:3^3.
Bokori, J., S. Fekete, I. Kadar, and M. Albert. 1995. Complex study of the
physiological role of cadmium. II. Effect of cadmium load on the cad-
mium content of eggs. Acta Vet. Hung. 43:45—62.
Bokori, J., S. Fekete, R. Glavits, I. Kadar, J. Koncz, and L. Kovari. 1996.
Complex study of the physiological role of cadmium. IV. Effects of
prolonged dietary exposure of broiler chickens to cadmium. Acta Vet.
Hung. 44:57-74.
Bray, B. J., R. H. Dowdy, R. D. Goodrich, and D. E. Pamp. 1983. Trace
metal accumulation in tissues of goats fed silage produced on sludge-
amended soil. J. Environ. Qual. 14:114—118.
Bressler, J. P., L. Olivi, J. H. Cheong, Y. Kim, and D. Bannona. 2004.
Divalent metal transporter 1 in lead and cadmium transport. Ann. N. Y.
Acad. Sci. 1012:142-152.
Brown, V., D. Shurben, W. Miller, and M. Crane. 1994. Cadmium toxicity
to rainbow trout Oncorhynchus mykiss Walbaum and brown trout Salmo
trutta L. over extended exposure periods. Ecotoxicol. Environ. Saf.
29:38^6.
Brzoska, M. M., and J. Moniuszko-Jakoniuk. 1998. The influence of cal-
cium content in diet on cumulation and toxicity of cadmium in the or-
ganism. Arch. Toxicol. 72:63-73.
Brzoska, M. M., and J. Moniuszko-Jakoniuk. 2001. Interactions between
cadmium and zinc in the organism. Food Chem. Toxicol. 39:967—980.
Buchet, J. P., R. Lauwerys, H. Roels, A. Bernard, P. Bruaux, F. Claeys,
G. Ducoffre, P. de Plaen, J. Staessen, A. Amery, P. Linjen, L. Thijs,
D. Ronda, F. Sartor, A. Saint Remy, and L. Nick. 1990. Renal ef-
fects of cadmium body burden of the general population. Lancet
336:699-702.
Butterman, W. C, and J. Plachy. 2004. Mineral Commodity Profiles: Cad-
mium. Washington, DC: U.S. Geological Survey.
Cain, B. W., L. Sileo, J. C. Franson, and J. Moore. 1983. Effects of dietary
cadmium on mallard ducklings. Environ. Res. 32:286—297.
Cardenas, A., A. Bernard, and R. Lauwerys. 1992. Incorporation of
[35S]sulfate into glomerular membranes of rats chronically exposed to
cadmium and its relation with urinary glycosaminoglycans and pro-
teinuria. Toxicology 76:219-231.
Cerny, E. A., and M. H. Bhattacharyya. 2003. Low-volume, high-sensitiv-
ity assay for cadmium in blood and urine using conventional atomic
absorption spectrophotometry. Anal. Biochem. 314:180-193.
Choudhury, H., T. Harvey, W. C. Thayer, T. F. Lockwood, W. M. Stiteler,
P. E. Goodrum, J. M. Hassett, and G. L. Diamond. 2001. Urinary cad-
mium elimination as a biomarker of exposure for evaluating a cadmium
dietary exposure — biokinetics model. J. Toxicol. Environ. Health A.
63:321-350.
Combs, D. K., R. D. Goodrich, and J. C. Meiske. 1983. Influence of dietary
zinc or cadmium on hair and tissue mineral concentrations in rats and
goats. J. Anim. Sci. 56:184-193.
Cousins, R. J., A. K. Barber, and J. R. Trout. 1973. Cadmium toxicity in
growing swine. J. Nutr. 103:964-972.
Czarnecki, G. L., and D. H. Baker. 1982. Tolerance of the chick to excess
dietary cadmium as influenced by dietary cysteine and by experimental
infection with Eimeria acervulina. J. Anim. Sci. 54:983-988.
Di Giulio, R. T., and P. F. Scanlon. 1984. Sublethal effects of cadmium
ingestion on mallard ducks. Arch. Environ. Contam. Toxicol. 13:
765-771.
Dorian, C, V. H. Gattone 2nd, and C. D. Klaassen. 1995. Discrepancy
between the nephrotoxic potencies of cadmium-metallothionein and
cadmium chloride and the renal concentration of cadmium in the proxi-
mal convoluted tubules. Toxicol. Appl. Pharmacol. 130:161-168.
Dowdy, R. H., B. J. Bray, and R. D. Goodrich. 1983. Trace metal and min-
eral composition of milk and blood from goats fed silage produced on
sludge-amended soil. J. Environ. Qual. 12:473^77.
Duizer, E., A. J. Gilde, C. H. Versantvoort, and J. P. Groten. 1999. Effects
of cadmium chloride on the paracellular barrier function of intestinal
epithelial cell lines. Toxicol. Appl. Pharmacol. 155:1 17-126.
Elinder, C. G. 1992. Cadmium as an environmental hazard. lARC Sci. Publ.
123-132.
Engel, D. W., and B. A. Fowler. 1979. Factors influencing cadmium accu-
mulation and its toxicity to marine organisms. Environ. Health Perspect.
28:81-88.
EPA (U.S. Environmental Protection Agency). 1985. Cadmium Contami-
nation of the Environment, EPA-440/4-85-023. Washington, DC: U.S.
Environmental Protection Agency.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
MINERAL TOLERANCE OF ANIMALS
EPA. 200 1 . 200 1 Update of Ambient Water Quality Criteria for Cadmium.
Washington, DC: Office of Science and Tectinology.
Fitzgerald, P. R., J. Peterson, and C. Lue-Hing. 1985. Heavy metals in tis-
sues of cattle exposed to sludge-treated pastures for eight years. Am. J.
Vet. Res. 46:703-707.
Floris, B., G. Bomboi, P. Sechi, S. Pirino, and M. L. Marongiu. 2000. Cad-
mium chronic administration to lactating ewes: reproductive perfor-
mance, cadmium tissue accumulation and placental transfer. Ann. Chim.
90:703-708.
Foulkes, E. C. 1985. Interactions between metals in rat jejunum: implica-
tions on the nature of cadmium uptake. Toxicology 37:117-125.
Foulkes, E. C, T. L. Mort, and C. R. Buncher. 1991. Intestinal cadmium
permeability in mature and immature rats. Proc. Soc. Exp. Biol. Med.
197:477-481.
Fox, M. R., R. M. Jacobs, A. O. Jones, and B. E. Fry, Jr. 1979. Effects of
nutritional factors on metabolism of dietai^y cadmium at levels similar
to those of man. Environ. Health Perspect. 28: 107— 1 14.
Fox, M. R., S. H. Tao, C. L. Stone, and B. E. Fry, Jr. 1984. Effects of zinc,
iron and copper deficiencies on cadmium in tissues of Japanese quail.
Environ. Health Perspect. 54:57-65.
Fullmer, C. S., T. Oku, and R. H. Wasserman. 1980. Effect of cadmium
administration on intestinal calcium absorption and vitamin D-depen-
dent calcium-binding protein. Environ. Res. 22:386—399.
Giles, M. A. 1988. Accumulation of cadmium by rainbow trout during ex-
tended exposure. Can. J. Fish. Aquat. Sci. 45:1045-1053.
Gill, K. D., R. Pal, and R. Nath. 1989. Effect of cadmium on lipid
peroxidation and antioxidant enzymes in undernourished weanling rat
brain. Pharmacol. Toxicol. 65:73—77.
Gill, T. S., and A. Epple. 1992. Impact of cadmium on the mummichog
Fundulus heteroclitus and the role of calcium in suppressing heavy metal
toxicity. Comp. Biochem. Physiol. C 101:519-523.
Goyer, R. A., C. R. Miller, S. Y. Zhu, and W. Victery. 1989. Non-
metallothionein-bound cadmium in the pathogenesis of cadmium neph-
rotoxicity in the rat. Toxicol. Appl. Pharmacol. 101:232-244.
Groten, J. P., E. J. Sinkeldam, J. B. Luten, and P. J. van Bladeren. 1990.
Comparison of the toxicity of inorganic and liver-incorporated cad-
mium: a 4-wk feeding study in rats. Food Chem. Toxicol. 28:435^141.
Groten, J. P., E. J. Sinkeldam, T. Muys, J. B. Luten, and P. J. van Bladeren.
1991. Interaction of dietary Ca, P, Mg, Mn, Cu, Fe, Zn and Se with the
accumulation and oral toxicity of cadmium in rats. Food Chem. Toxicol.
29:249-258.
Groten, J. P., J. H. Koeman, J. H. van Nesselrooij, J. B. Luten, J. M. Fentener
van Vlissingen, W. S. Stenhuis, and P. J. van Bladeren. 1994. Compari-
son of renal toxicity after long-term oral administration of cadmium
chloride and cadmium-metallothionein in rats. Fundam. Appl. Toxicol.
23:544-552.
Gupta, P., and A. Kar. 1999. Cadmium induced thyroid dysfunction in
chicken: hepatic type I iodothyronine 5'-monodeiodinase activity and
role of lipid peroxidation. Comp. Biochem. Physiol. C Pharmacol.
Toxicol. Endocrinol. 123:39^14.
Hamada, T., A. Tanimoto, S. Iwai, H. Fujiwara, and Y. Sasaguri. 1994.
Cytopathological changes induced by cadmium-exposure in canine
proximal tubular cells: A cytochemical and ultrastructural study. Neph-
ron 68:104-111.
Hansen, J. A., P. G. Welsh, J. Lipton, D. Cacela, and A. D. Dailey. 2002a.
Relative sensitivity of bull trout (Salvelinus confluentus) and rainbow
trout (Oncorhynchus mykiss) to acute exposures of cadmium and zinc.
Environ. Toxicol. Chem. 21:67-75.
Hansen, J. A., P. G. Welsh, J. Lipton, and M. J. Suedkamp. 2002b. The
effects of long-term cadmium exposure on the growth and survival of
juvenile bull trout (Salvelinus confluentus). Aquat. Toxicol. 58:165—
174.
Hansen, L. G., and T. D. Hinesly. 1979. Cadmium from soil amended with
sewage sludge: effects and residues in swine. Environ. Health Perspect.
28:51-57.
He, Q. B., and B. R. Singh. 1994. Crop uptake of cadmium from phospho-
rus fertilizers. Water Air Soil PoUut. 74:251-265.
Heffron, C. L., J. T. Reid, D. C. Elfving, G. S. Stoewsand, W. M. Haschek,
J. N. Telford, A. K. Furr, T. F. Parkinson, C. A. Bache, W. H.
Gutenmann, P. C. Wszoiek, and D. J. Lisk. 1980. Cadmium and zinc in
growing sheep fed silage corn grown on municipal sludge amended
soiL J. Agric. Food Chem. 28:58-61.
Hennig, A., G. Hartmann, K. Gruhn, and M. Anke. 1968. Contraceptive
action of cadmium in laying hens. Naturwissenschaften 55:551.
Hinesly, T. D., L. G. Hansen, D. J. Bray, and K. E. Redborg. 1985. Transfer
of sludge-borne cadmium through plants to chickens. J. Agric. Food
Chem. 33:173-180.
Hogue, D. E., J. J. Parrish, R. H. Foote, J. R. Stouffer, J. L. Anderson, G. S.
Stoewsand, J. N. Telford, C. A. Bache, W. H. Gutenmann, and D. J.
Lisk. 1984. Toxicologic studies with male sheep grazing on municipal
sludge-amended soil. J. Toxicol. Environ. Health 14:153—161.
Hollis, L., J. C. McGeer, D. G. McDonald, and C. M. Wood. 2000. Effects
of long term sublethal Cd exposure in rainbow trout during soft water
exposure: implications for biotic ligand modelling. Aquatic Toxicol.
51:93-105.
Hollis, L., C. Hogstrand, and C. M. Wood. 2001. Tissue-specific cadmium
accumulation, metallothionein induction, and tissue zinc and copper lev-
els during chronic sublethal cadmium exposure in juvenile rainbow
trout. Ai'ch. Environ. Contam. Toxicol. 41:468^74.
IPCS (International Programme on Chemical Safety). 1992a. Environmen-
tal Health Criteria 134: Cadmium. Geneva: World Health Organization.
IPCS. 1992b. Environmental Health Criteria 135: Cadmium — Environmen-
tal Aspects. Geneva: World Health Organization.
Jarup, L., M. Berglund, C. G. Elinder, G. Nordberg, and M. Vahter. 1998.
Health effects of cadmium exposure — a review of the literature and a
risk estimate. Scand. J. Work Environ. Health 24 (Suppl. I):I-51.
Johnson, D. E., E. W. Kienholz, J. C. Baxter, E. Spangler, and G. M. Ward.
1981. Heavy metal retention in tissues of cattle fed high cadmium sew-
age sludge. J. Anim. Sci. 52:108-114.
Johnson, M. D., N. Kenney, A. Stoica, L. Hilakivi-Clarke, B. Singh, G.
Chepko, R. Clarke, P. F. Sholler. A. A. Lirio, C. Foss, R. Reiter, B.
Trock, S. Paik, and M. B. Martin. 2003. Cadmium mimics the in vivo
effects of estrogen in the uterus and mammary gland. Nature Med.
9:1081-1084.
Kaji, T., M. Takata, T. Hoshino, T. Miyahara, H. Kozuka, Y. Kurashige,
and F. Koizumi. 1988. Role of zinc in protection against cadmium-
induced toxicity in formation of embryonic chick bone in tissue culture.
Toxicol. Lett. 44:219-227.
Kay, J., D. G. Thomas, M. W. Brown, A. Cryer, D. Shurben, J. F. Solbe, and
J. S. Garvey. 1986. Cadmium accumulation and protein binding pat-
terns in tissues of the rainbow trout, Salmo gairdneri. Environ. Health
Perspect. 65:133-139.
Kertesz. V., and T. Fancsi. 2003. Adverse effects of (surface water pollut-
ants) Cd, Cr and Pb on the embryogenesis of the mallard. Aquatic
Toxicol. 65:425-433.
King, R. H., W. G. Brown, V. C. M. Amenta, B. C. Shelley, P. D. Handson,
N. B. Greenhill, and G. B. Willcock. 1992. The effect of dietary cad-
mium intake on the growth performance and retention of cadmium in
growing pigs. Anim. Feed Sci. Technol. 37:1-7.
Klaassen, C. D., and J. Liu. 1998. Metallothionein transgenic and knock-
out mouse models in the study of cadmium toxicity. J. Toxicol. Sci. 23
(Suppl. 2):97-102.
Kodama, Y., K. Matsuno, T. Kawamoto, F. Kayama, and K. Tsuchiya. 1992.
Chronic health effects of orally administered cadmium in dogs. J.
Environ. Sci. Health A. 27:165-198.
Kojima, S., M. Kiyozumi, M. Mishima, T. Honda, and M. Nakagawa. 1985.
Effects of three proteins on absorption of cadmium in rats. Toxicology
34:161-171.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
CADMIUM
89
Kramer, J. R., H. E. Allen, W. Davison, K. L. Godtfredsen, J. S. Meyer, E.
M. Perdue, F. Tipping, D. Van de Meent, and J. C. Westall. 1997.
Chemical speciation and metal toxicity in surface waters. Pp. 57-70 in
Reassessment of Metals Criteria for Aquatic Life Protection, H. L.
Bergman and E. J. Dorward-King, eds. Pensacola, FL: SETAC Press.
Lamphere, D. N., C. R. Dorn, C. S. Reddy, and A.W. Meyer. 1984. Re-
duced cadmium body burden in cadmium-exposed calves fed supple-
mental zinc. Environ. Res. 33:1 19-129.
Lane, T. W., and F. M. Morel. 2000. A biological function for cadmium in
marine diatoms. Proc. Natl. Acad. Sci. USA 97:4627-4631.
Laurin, D. E., and K. C. Klasing. 1990. Roles of synthesis and degradation
in the regulation of metallothionein accretion in a chicken macrophage-
cell line. Biochem. J. 268:459^63.
Leach, R. M., Jr., K. W. Wang, and D. E. Baker. 1979. Cadmium and the
food chain: the effect of dietary cadmium on tissue composition in
chicks and laying hens. J. Nutr. 109:437-M-3.
Lee, J., N. D. Grace, and J. R. Rounce. 1994. Cadmium accumulation in
liver and kidney of sheep grazing ryegrass/white clover pastures. Proc.
N. Z. Soc. Anim. Prod. 54:31-33.
Lefevre, M., H. Heng, and R. B. Rucker. 1982. Dietary cadmium, zinc and
copper: effects on chick lung morphology and elastin cross-linking. J.
Nutr. 112:1344-1352.
Lind, Y., A. Wicklund Glynn, J. Engman, and L. Jorhem. 1995.
B ioavailability of cadmium from crab hepatopancreas and mushi'oom in
relation to inorganic cadmium: a 9- week feeding study in mice. Food
Chem. Toxicol. 33:667-673.
Lind, Y., J. Engman, L. Jorhem, and A. W. Glynn. 2001. Cadmium absorp-
tion in mice: effects of broiling on bioavailability of cadmium in foods
of animal origin. J. Toxicol. Environ. Health A. 62:269-280.
Linden, A., I. M. Olsson, and A. Oskarsson. 1999. Cadmium levels in feed
components and kidneys of growing/finishing pigs. J. AOAC Int.
82:1288-1297.
Linden, A., I. M. Olsson, I. Bensryd, T. Lundh, S. Skerfving, and A.
Oskarsson. 2003. Monitoring of cadmium in the chain from soil via
crops and feed to pig blood and kidney. Ecotoxicol. Environ. Saf.
55:213-222.
Lisk, D. J.. R. D. Boyd, J. N. Telford, J. G. Babish, G. S. Stoewsand, C. A.
Bache, and W. H. Gutenmann. 1982. Toxicologic studies with swine
fed corn grown on municipal sewage sludge-amended soil. J. Anim.
Sci. 55:613-619.
Loeser, E., and D. Lorke. 1977. Semichronic oral toxicity of cadmium. 2.
Studies on dogs. Toxicology 7:225-232.
Lymberopoulos, A. G., V. P. Kotsaki-Kovatsi, A. Taylor, N. Papaioannou,
and P. Brikas. 2000. Effects of cadmium chloride administration on the
macroscopic and microscopic characteristics of ejaculates from Chios
ram-lambs. Theriogenology, 54:1 145-1 157.
Masaoka, T., F. Akahori, S. Aral, K. Nomiyama, H. Nomiyama,
K. Kobayashi, Y. Nomura, and T. Suzuki. 1994. A nine-year chronic
toxicity study of cadmium ingestion in monkeys. I. Effects of dietary
cadmium on the general health of monkeys. Vet. Hum. Toxicol. 36:
189-194.
Matsuno, K., Y. Kodama, T. Kawamoto, F. Kayama, and K. Tsuchiya.
1991a. Absorption of cadmium after a long-term oral administration of
cadmium to dogs. Biol. Trace Elem. Res. 28:99-108.
Matsuno, K., Y. Kodama, and K. Tsuchiya. 1991b. Biological half-time and
body burden of cadmium in dogs after a long-term oral administration
of cadmium. Biol. Trace Elem. Res. 29: 1 1 1-123.
McKenna, I. M., R. L. Chaney, S. H. Tao, R. M. Leach Jr., and F. M.
Williams. 1992. Interactions of plant zinc and plant species on the
bioavailability of plant cadmium to Japanese quail fed lettuce and spin-
ach. Environ. Res. 57:73-87.
Min, K. S., K. Kobayashi, S. Onosaka, N. Ohta, Y. Okada, and K. Tanaka.
1986. Tissue distribution of cadmium and nephropathy after adminis-
tration of cadmium in several chemical forms. Toxicol. Appl.
Pharmacol. 86:262-270.
Morcombe, P. W.. D. S. Petterson, P. J. Ross, and J. R. Edward. 1994. Soil
and agronomic factors associated with cadmium accumulations in kid-
neys of grazing sheep. Aust. Vet. J. 71:404-406.
MuUer, L., J. Abel, and F. K. Ohnesorge. 1986. Absorption and distribution
of cadmium (Cd), copper and zinc following oral subchronic low level
administration to rats of different binding forms of cadmium (Cd-ac-
etate, Cd-metallothionein, Cd-glutathione). Toxicology 39:187—195.
Murphy, E. W., C. R. Brewington, B. W. Weiss, and M. A. Nelson. 1979.
Health and safety aspects of the use of mechanically deboned poultry.
Food Safety and Quality Services. Washington, D.C.: U.S. Departmentt
of Agriculture.
Nguyen, L. T., and C. R. Janssen. 2002. Embryo-larval toxicity tests with
the African catfish (Clarias gariepinus): comparative sensitivity of end-
points. Arch. Environ. Contam. Toxicol. 42:256—262.
Nicholson, F. A., B. J. Chambers, J. R. Williams, and R. J. Unwin. 1999.
Heavy metal contents of livestock feeds and animal manures in England
and Wales. Bioresour. Technol. 70:23-31.
Nolan, T. D., and D. Brown. 2000. The influence of elevated dietary zinc,
selenium, and their combination on the suppressive effect of dietary and
intraperitoneal cadmium on egg production in laying hens. J. Toxicol.
Environ. Health A. 60:549-565.
Nomiyama, K., andH. Nomiyama. 1984. Reversibility of cadmium-induced
health effects in rabbits. Environ. Health Perspect. 54:201-211.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
NRC. 2002. Biosolids Applied to Land. Washington, D.C.: National Acad-
emy Press.
Om, A. S., K. W. Chung, and H. S. Chung. 2002. Effect of cadmium accu-
mulation on renal tissues in broilers. Bull. Environ. Contam. Toxicol.
68:297-301.
Osuna, O., G. T. Edds, and J. A. Popp. 1981. Comparative toxicity of feed-
ing dried urban sludge and an equivalent amount of cadmium to swine.
Am. J. Vet. Res. 42:1542-1546.
Papoutsoglou, S. E., and P. D. Abel. 1988. Sublethal toxicity and accumu-
lation of cadmium in Tilapia aurea. Bull. Environ. Contam. Toxicol.
41:404-411.
Pinot, F., S. E. Kreps, M. Bachelet, P. Hainaut, M. Bakonyi, and B. S. PoUa.
2000. Cadmium in the environment: sources, mechanisms of biotoxicity,
and biomarkers. Rev. Environ. Health 15:299-323.
Plachy, J. 2002. Cadmium. In U.S. Geological Survey Minerals Yearbook:
Cadmium. Available at http://minerals.usgs.gov/minerals/pubs/com-
modity/cadmium/cadmmyb02.pdf.
Powell, G. W., W. J. Miller, and C. M. Clifton. 1964. Effect of cadmium on
the palatability of calf starters. J. Dairy Sci. 47:1017-1 122.
Prasad, R., and R. Nath. 1995. Cadmium-induced nephrotoxicity in rhesus
monkeys (Macaca mulatta) in relation to protein calorie malnutrition.
Toxicology 100:89-100.
Pribilincova, J., M. Maretta, I. Janotikova, and E. Marettova. 1995. The
effect of cadmium treatment on breeding hens and cocks and early vi-
ability of their chickens. Vet. Med. (Praha) 40:353-357.
Rani, A. U. 2000. Cadmium-induced bioaccumulation in the selected tis-
sues of a freshwater teleost, Oreochi'omis mossambicus (Tilapia). Ann.
N.Y. Acad. Sci. 919:318-320.
Regunathan, A., E. A. Cerny, J. Villarreal, and M. H. Bhattacharyya. 2002.
Role of fos and src in cadmium-induced decreases in bone mineral con-
tent in mice. Toxicol. Appl. Pharmacol. 185:25^0.
Rimbach, G., K. Brandt, E. Most, and J. Pallauf. 1995. Supplemental phytic
acid and microbial phytase change zinc bioavailability and cadmium
accumulation in growing rats. J. Trace Elem. Med. Biol. 9:1 17-122.
Ruoff, W. L., G. L. Diamond, S. F. Velazquez, W. M. Stiteler, and D. J.
Gefell. 1994. Bioavailability of cadmium in food and water: a case study
on the derivation of relative bioavailability factors for inorganics and
their relevance to the reference dose. Regul. Toxicol. Pharmacol.
20:139-160.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
90
MINERAL TOLERANCE OF ANIMALS
Sacco-Gibson, N., S. Chaudhry, A. Brock, A. B. Sickles, B. Patel, R.
Hegstad, S. Johnston, D. Peterson, and M. Bhattacharyya. 1992. Cad-
mium effects on bone metabolism: accelerated resoiption in ovariecto-
mized, aged beagles. Toxicol. Appl. Pharmacol. 113:274—283.
Sanson, D. W., D. M. Hallford, and G. S. Smith. 1984a. Effects of dietary
sewage solids on feedlot performance, carcass characteristics, serum
constituents and tissue elements of growing lambs. J. Anim. Sci.
59:425^31.
Sanson, D. W., D. M. Hallford, and G. S. Smith. 1984b. Effects of long-
term consumption of sewage solids on blood, milk and tissue elemental
composition of breeding ewes. J. Anim. Sci. 59:416^24.
Sapunar-Postruznik. J., D. Bazulic, M. Grubelic, H. K. Drincic. and B. Njari.
200 1 . Cadmium in animal feed and in foodstuffs of animal origin. Food
Technol. Biotechnol. 39:67-71.
Sato, S., M. Okabe, T. Emoto, M. Kurasaki, and Y. Kojima. 1997. Restric-
tion of cadmium transfer to eggs from laying hens exposed to cadmium.
J. Toxicol. Environ. Health 51:15-22.
Satoh, M., H. Koyama, T. Kaji, H. Kito, and C. Tohyama. 2002. Perspec-
tives on cadmium toxicity research. Tohoku J. Exp. Med. 196:23-32.
Schafer, S. G., U. Schwegler, and K. Schumann. 1990. Retention of cad-
mium in cadmium-naive normal and iron-deficient rats as well as in
cadmium-induced iron-deficient animals. Ecotoxicol. Environ. Saf.
20:71-81.
Sharma, R. P., J. C. Street, M. P. Verma, and J. L. Shupe. 1979. Cadmium
uptake from feed and its distribution to food products of livestock.
Environ. Health Perspect. 28:59-66.
Sharma, R. P., J. C. Street, J. L. Shupe, and D. R. Bourcier. 1982. Accumu-
lation and depletion of cadmium and lead in tissues and milk of lactat-
ing cows fed small amounts of these metals. J. Dairy Sci. 65:972-979.
Singh, B. R. 1994. Trace element availability to plants in agricultural soils,
with special emphasis on fertilizer inputs. Environ. Rev. 2:133-146.
Smith, R. M., L. C. Griel, Jr., L. D. MuUer, R. M. Leach, and D. E. Baker.
1991a. Effects of dietary cadmium chloride throughout gestation on
blood and tissue metabolites of primigravid and neonatal dairy cattle. J.
Anim. Sci. 69:4078-4087.
Smith, R. M., R. M. Leach, L. D. Muller, L. C. Griel Jr., and D. E. Baker.
1991b. Effects of long-term dietary cadmium chloride on tissue, milk,
and urine mineral concentrations of lactating dairy cows. J. Anim. Sci.
69:4088-^096.
Stoewsand, G. S., J. G. Babish, J. N. Telford, C. Bahm, C. A. Bache, W. H.
Gutenmann, and D. J. Lisk. 1986. Response of Japanese quail fed seed
meal from sunflowers grown on a municipal sludge- amended soil: el-
evation of cadmium in tissues. J. Toxicol. Environ. Health 17:91-100.
Stoica, A., B. S. Katzenellenbogen. and M. B. Martin. 2000. Activation of
estrogen receptor-alpha by the heavy metal cadmium. Mol. Endocrinol.
14:545-553.
Sugawara, N., and C. Sugawara. 1974. Cadmium accumulation in organs and
mortality during a continued oral uptake. Arch. Toxicol. 32:297-306.
Sullivan, T. W., J. H. Douglas, and N. J. Gonzalez. 1994. Levels of various
elements of concern in feed phosphates of domestic and foreign origin.
Poult. Sci. 73:520-528.
Swiergosz-Kowalewska, R. 2001. Cadmium distribution and toxicity in tis-
sues of small rodents. Microsc. Res. Tech. 55:208—222.
Szebedinszky, C, J. C. McGeer, D. G. McDonald, and C. M. Wood. 2001.
Effects of chronic Cd exposure via the diet or water on internal organ-
specific distribution and subsequent gill Cd uptake kinetics in juvenile
rainbow trout (Oncorhynchus mykiss). Environ. Toxicol. Chem.
20:597-607.
Tarasenko, N. Y., R. S. Vorobeva, V. S. Spiridinova, and L. P. Shabalina.
1974. Experimental investigation of toxicity of cadmium and zinc
caprylates. J. Hyg. Epidemiol. Microbiol. Immunol. 18:144—153.
Telford, J. N., M. L. Thonney, D. E. Hogue, J. R. Stouffer, C. A. Bache, W.
H. Gutenmann, D. J. Lisk, J. G. Babish, and G. S. Stoewsand. 1982.
Toxicologic studies in growing sheep fed silage corn cultured on munici-
pal sludge-amended acid subsoil. J. Toxicol. Environ. Health 10:73-85.
Telford, J. N., J. G. Babish, P. B. Dunham, D. E. Hogue, K. W. Miller, G. S.
Stoewsand, B. H. Magee, J. R. Stouffer, C. A. Bache, and D. J. Lisk.
1984a. Toxicologic studies with lambs fed sugar beets grown on mu-
nicipal sludge-amended soil: lowered relative hemoglobin in red blood
cells and mutagens in blood and excreta. Am. J. Vet. Res. 45:2490-
2494.
Telford, J. N., J. G. Babish, B. E. Johnson, M. L. Thonney, W. B. Currie, C.
A. Bache, W. H. Gutenmann, andD. J. Lisk. 1984b. Toxicologic studies
with pregnant goats fed grass-legume silage grown on municipal sludge-
amended subsoil. Arch. Environ. Contam. Toxicol. 13:635-640.
Thomas, D. G., M. W. Brown, D. Shurben, J. F. Solbe, A. Cryer, and J. Kay.
1985. A comparison of the sequestration of cadmium and zinc in the
tissues of rainbow trout (Salmo gairdneri) following exposure to the
metals singly or in combination. Comp. Biochem. Physiol. C 82:55—62.
Van Bruwaene, R., G. B. Gerber, R. Kirchmann, and J. Colard. 1982. Trans-
fer and distribution of radioactive cadmium in dairy cows. Int. J.
Environ. Studies 19:47-52.
Vos, G., H. Lammers, and C. A. Kan. 1990. Cadmium and lead in muscle
tissue and organs of broilers, turkeys and spent hens and in mechani-
cally deboned poultry meat. Food Addit. Contam. 7:83—91.
Waalkes, M. P. 1 986. Effect of dietary zinc deficiency on the accumulation
of cadmium and metallothionein in selected tissues of the rat. J. Toxicol.
Environ. Health 18:301-313.
Waalkes, M. P. 2003. Cadmium carcinogenesis. Mutat. Res. 533:107-120.
Waisberg, M., P. Joseph, B. Hale, and D. Beyersmann. 2003. Molecular
and cellular mechanisms of cadmium carcinogenesis. Toxicology
192:95-117.
Wester, R. C, H. I. Maibach, L. Sedik, J. Melendres, S. DiZio, and M.
Wade. 1992. In vitro percutaneous absorption of cadmium from water
and soil into human skin. Fundam. Appl. Toxicol. 19:1-5.
Whelton, B. D., M. H. Bhattacharyya, B. A. Carnes, E. S. Moretti, andD. P.
Peterson. 1988. Female reproduction and pup survival and growth for
mice fed a cadmium-containing purified diet through six consecutive
rounds of gestation and lactation. J. Toxicol. Environ. Health 24:
321-343.
Whelton, B. D., M. H. Bhattacharyya, D. P. Peterson, E. S. Moretti, J. M.
Toomey, and L. L. Williams. 1994. Skeletal changes in multiparous and
nuUiparous mice fed a nutrient-deficient diet containing cadmium. Toxi-
cology 91:235-251.
White, D. H., and M. T. Finley. 1978. Uptake and retention of dietary cad-
mium in mallard ducks. Environ. Res. 17:53-59.
White, D. H., M. T. Finley, and J. F. Ferrell. 1978. Histopathologic effects
of dietary cadmium on kidneys and testes of mallard ducks. J. Toxicol.
Environ. Health 4:551-558.
Xu, G., G. Zhou, T. Jin, T. Zhou, S. Hammarstrom, A. Bergh, and G.
Nordberg. 1999. Apoptosis and p53 gene expression in male reproduc-
tive tissues of cadmium exposed rats. Biometals 12:131-1 39.
Xu, J., D. Maki, and S. R. Stapleton. 2003. Mediation of cadmium-induced
oxidative damage and glucose-6-phosphate dehydrogenase expression
through glutathione depletion. J. Biochem. Mol. Toxicol. 17:67-75.
Zalups, R. K., and S. Ahmad. 2003. Molecular handling of cadmium in
transporting epithelia. Toxicol. Appl. Pharmacol. 186:163-188.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
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10
Calcium
INTRODUCTION
Calcium (Ca) atoms do not exist in their free state — but
calcium-containing minerals are common in nature. Fairly
pure deposits of calcium carbonate in the form of limestone
are common and are a major source of calcium used in ani-
mal diet formulation. Nearly pure calcium sulfate is also
found in the form of gypsum that is used in Portland cement,
drywall, and plaster production as well as animal feeds. Cal-
cium hydroxide (lime) is not commonly used as a dietary
supplement but is often used as an astringent to reduce bac-
terial loads during disinfection of animal pens. Calcium
phosphate salts are used for the manufacture of certain types
of glass, but they are more commonly used as a source of
calcium and phosphate in animal feeds. Calcium chloride is
used in animal feeds when acidification of blood and urine is
desired. Calcium polysulfide (lime sulfur, "wettable sulfur")
is used as a fungicide, especially in orchards and around or-
namental shrubbery.
Calcium is a positively charged alkaline Earth metal with
an atomic weight of 40.08 and an equivalent weight of 20.04.
Calcium is a divalent cation. Chloride and sulfate salts of
calcium are water soluble; most other inorganic calcium salts
are only slightly soluble in water. Organic salts of calcium,
such as calcium propionate, are very soluble and are increas-
ingly being used in diets for man and animals.
ESSENTIALITY
Extracellular calcium is essential for formation of skel-
etal tissues, transmission of nervous tissue impulses, excita-
tion of skeletal and cardiac muscle contraction, blood clot-
ting, eggshell formation, and as a component of milk.
Intracellular calcium, while 1/10,000 the concentration of
extracellular calcium, is involved in the activity of a wide
array of enzymes and serves as an important "second mes-
senger" conveying information from the surface of the cell
to the interior of the cell.
About 98 percent of the calcium in the body is located
within the skeleton where calcium, along with phosphate
anion, serves to provide structural strength and hardness to
bone. The other 2 percent of the calcium in the body is found
primarily in the extracellular fluids of the body. Plasma cal-
cium concentration is normally 90-110 mg/L or 2.25-2.75
mM. The ionized calcium concentration of the plasma of
mammals and birds must be maintained at a relatively con-
stant value of 1-1.25 mM to ensure normal nerve membrane
and muscle end plate electrical potential and conductivity,
forcing vertebrates to evolve an elaborate system to main-
tain calcium homeostasis. This system attempts to maintain
extracellular calcium concentration constant by increasing
calcium entry into the extracellular fluids whenever there is
a loss of calcium from the extracellular compartment. When
dietary calcium is inadequate this system may sacrifice bone
calcium stores in an attempt to maintain nonnal blood cal-
cium concentration.
Most farm species will require diets that are between 0.5
and 1 percent calcium. Optimal growth and reproduction,
including lactation, will require more calcium than mainte-
nance of the adult animal. Hens laying eggs require about
3.5 percent calcium in the diet to maintain quality of the
eggshell.
Cold-blooded species can vary greatly in their require-
ment for dietary calcium. Softshell turtles raised for meat
grew best when their diet was 5.7 percent calcium (and 3
percent phosphorus) (Huang et al., 2003). Some fish species
reared in fresh water or seawater can obtain all the calcium
they need from the water in which they reside. In freshwater
species, the gills can absorb calcium from the water. Brook
trout, for example, can obtain as much as 80 percent of their
skeletal calcium requirement from water (McCay, 1936). Sea
fish drink enough seawater to obtain much if not all of their
calcium needs. However some freshwater and saltwater fish
also require calcium supplementation for optimal growth
(about 0.2 percent calcium added to the diet) as they cannot
obtain enough calcium from the water alone (Robinson et
97
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MINERAL TOLERANCE OF ANIMALS
al., 1986; Chavez-Sanchez et al., 2000; Hossain and
Furuichi, 2000).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Determination of calcium in feeds and tissues is best ac-
complished by wet or dry ashing of the sample followed by
resuspension of the ash in an acidic solution for analysis by
atomic absorption spectrophotometry. Atomic absorption is
conducted at a wavelength of 422.7 nm and can detect as
little as 0.01 mg Ca/L. Phosphate, sulfate, and aluminum
that might be in the sample can interfere with calcium absorp-
tion spectra, but their effect is masked by the addition of
lanthanum to the standards and samples being analyzed.
Since low calcium values result if the pH of the sample is
above 7, both standards and samples are prepared in dilute
hydrochloric acid solution. Concentrations of magnesium
greater than 1,000 mg/L can also cause low calcium values.
Concentrations of up to 500 mg/L each of sodium, potassium,
and nitrate cause no interference. Anionic chemical interfer-
ences can be expected if lanthanum is not used in samples
and standards (EPA, 1983). The nitrous oxide-acetylene
flame will provide two to five times greater sensitivity than
an air-acetylene flame, but is not necessary for routine
analysis of feeds or biological samples. Near-infrared spec-
trophotometry is not a satisfactory method of determining
calcium content of feedstuffs and forages, though it is often
used for that purpose.
Calcium concentrations can also be measured to ppb (ug/L)
levels using inductively coupled plasma optical emission
spectrophotometry (ICP-OES). ICP-OES uses radio fre-
quency-generated plasma to excite the electrons of the
calcium atoms, which then produce photons unique to
calcium. Photomultiplier tubes detect and quantitate the
photons emitted by the excited calcium atoms, allowing
quantitation of the calcium concentration. An inductively-
coupled plasma source atomizes and excites even the most
refractory elements with high efficiency, so there is less
interference and about 10-fold greater sensitivity using
ICP-OES than using atomic absorption spectrometry.
REGULATION AND METABOLISM
When calcium loss exceeds entry, hypocalcemia can oc-
cur. This results in loss of nerve and muscle function which
can, in some instances, lead to recumbency (milk fever in
cows) or tetany (lactating dogs, cows, pigs). During vitamin
D intoxication, calcium can enter the extracellular compart-
ment faster than it leaves, resulting in hypercalcemia, which
can lead to soft tissue deposition of calcium and then eventu-
ally necrosis of the tissues.
Calcium leaves the extracellular fluids during bone for-
mation, in digestive secretions, sweat, and urine. An espe-
cially large loss of calcium occurs during lactation or egg-
shell formation. Calcium lost via these routes can be replaced
from dietary calcium, from resorption of calcium stored in
bone, or by resorption of a larger portion of the calcium fil-
tered across the renal glomerulus (i.e., reducing urinary cal-
cium loss). Whenever calcium loss from the extracellular
fluids exceeds the amount of calcium entering the extracel-
lular fluids, plasma calcium concentration decreases. The
parathyroid glands monitor carotid artery blood calcium con-
centration and secrete parathyroid hormone when they sense
a decrease in blood calcium concentration. Parathyroid hor-
mone immediately increases renal calcium reabsorption
mechanisms to reduce urinary calcium loss. This will suc-
ceed in returning blood calcium concentration to normal if
the loss from the extracellular compartment is small, because
normally only small amounts of calcium are excreted in the
urine each day. For example, a 600-kg cow typically ex-
cretes 0.5-2 g calcium in her urine each day. When calcium
losses are larger, parathyroid honnone will stimulate pro-
cesses to enhance intestinal calcium absorption and resorp-
tion of bone calcium stores.
Bone is a living tissue that is constantly undergoing for-
mation and resorption. In young animals the rate of forma-
tion exceeds the rate of resorption, resulting in net bone ac-
cretion. In mature animals, portions of the skeleton,
presumably those traumatized with microfractures during
normal wear and tear, are resorbed and reformed constantly.
In humans it is estimated that the entire adult skeleton is
rebuilt every 7 years (Frost, 1964). Parathyroid hormone can
uncouple bone resorption from bone formation, stimulating
resorptive mechanisms of bone osteoclasts while inhibiting
formation mediated by bone osteoblasts. The net result is an
efflux of calcium from bone to extracellular fluids. When
excessive calcium enters the blood, another hormone, calci-
tonin, produced within the thyroid gland, is secreted. Calci-
tonin inhibits osteoclastic bone resorption and stimulates re-
nal excretion of calcium.
Ultimately dietary calcium must enter the extracellular
fluids to permit optimal performance of the animal. Calcium
absorption can occur by passive transport between epithelial
cells across any portion of the digestive tract whenever ion-
ized calcium concentration in the digestive fluids directly
over the mucosa exceeds 6 mM (Bronner, 1987). These con-
centrations are reached when calves are fed all-milk diets
and when cows are given oral calcium drenches for preven-
tion of hypocalcemia (Goff and Horst, 1993). In nonruminant
species, studies suggest that as much as 50 percent of dietary
calcium absorption can be passive (Nellans, 1988). It is
unknown how much passive absorption of calcium occurs
from the diets typically fed to ruminants, but the diluting
effect of the rumen would likely reduce the degree to which
passive calcium absorption would occur. Active transport of
calcium appears to be the major route for calcium absorption
in mature animals and this process is controlled by 1,25-
dihydroxy vitamin D, the hormone derived from vitamin D.
Vitamin D, produced within the skin or provided in the diet.
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CALCIUM
99
is converted to 25-hydroxyvitamin D in tlie liver and can be
further metabolized to 1,25-dihydroxyvitamin D in the kid-
neys. Parathyroid hormone indirectly stimulates intestinal
calcium absorption because it is the primary regulator of re-
nal production of 1,25-dihydroxyvitamin D. The 1,25-
dihydroxyvitamin D is released to the circulation and inter-
acts with nuclear receptors within the intestinal epithelium,
primarily in the small intestine, causing transcription and
translation of calcium transport proteins. Vitamin D-depen-
dent calcium-binding protein captures calcium at the apical
surface of epithelial cells and ferries the calcium to the
basolateral side of the cell. There it is pumped into the extra-
cellular space against a concentration gradient by a 1,25-
dihydroxyvitamin D-dependent calcium pump (Wasserman,
1981; Bronner, 1987). By carefully regulating the amount of
1,25-dihydroxyvitamin D produced, the amount of dietary
calcium absorbed can be adjusted up or down to maintain
constant extracellular calcium concentration.
Freshwater fish can obtain calcium from the water across
their gills. If the water in which they are reared is high in
calcium, they have little need for dietary calcium and little
need for vitamin D as intestinal calcium absorption is not
critical to meeting their calcium requirement. However,
when water calcium content is low the diet must supply cal-
cium, and the fish require vitamin D to use intestinal calcium
absorption efficiently (Lovell and Li, 1978). When freshwa-
ter fish must rely on their diet to meet calcium needs, they
also face another problem that terrestrial animals do not en-
counter: many do not possess gastric glands and cannot se-
crete hydrochloric acid into the ingesta. Therefore the in-
ability to solubilize dietary calcium can reduce absorption of
calcium incorporated into feed. Saltwater fish drink seawa-
ter where the calcium is already in a soluble form, so the
calcium is readily available for intestinal absorption.
SOURCES AND BIOAVAILABILITY
Calcium content of grains and high-starch feedstuffs is
very low and generally of low importance as a source of
calcium that might cause toxicity in an animal. Legumes can
be an important source of calcium for herbivores but the
bioavailability of calcium in plants is generally lower than
that of mineral sources (Martz et al., 1990). Common min-
eral sources of calcium used to supplement diets of animals
include calcium carbonate, calcium sulfate, mono- and di-
basic calcium phosphate, and calcium chloride. Bone meal
and oyster shells are also good sources of calcium. In rumi-
nants, calcium carbonate may have low bioavailability due
to its poor solubility. However, if finely ground, the calcium
in calcium carbonate becomes readily solubilized upon con-
tact with the acid of the abomasum and availability can be
quite high. In pigs, particle size of calcium carbonate had no
effect on calcium bioavailability (Ross et al., 1984). Cal-
cium from these mineral sources can be from 70-90 percent
available. During positive calcium balance, intestinal mecha-
nisms for absorption are shut down in most species. Notable
exceptions are the horse and rabbit (and possibly other hind
gut fermenters). In these species calcium absorption appears
to be independent of vitamin D and a large proportion of
dietary calcium is always absorbed (Bourdeau et al., 1986;
Brommage et al., 1988; Maenpaa et al., 1988).
Water can supply a small portion of the dietary calcium
requirement of birds and mammals but does not contain
enough calcium to cause toxicosis. Many freshwater fish
thrive in the hardest waters (hardness up to 300 mg calcium
carbonate/L) as it reduces the difference between the osmo-
larity of the fish's body and the water and reduces the energy
required by the fish to osmoregulate (Boyd, 1979).
TOXICOSIS
Single Dose
If a large bolus dose of calcium is given to an animal
orally it is possible for the concentration of calcium directly
over the mucosa of the intestinal tract to rise to the level at
which passive absorption of calcium occurs by paracellular
transport (Bronner, 1987). This pathway is not regulated by
the calcium homeostatic mechanisms. As a result, very large
amounts of readily soluble calcium administered as a single
dose can cause hypercalcemia for several hours (Goff and
Horst, 1994) (Table 10-1). Moderate hypercalcemia (plasma
calcium between 120 and 150 mg/L or 3-3.75 mM) causes
increased urine excretion (diuresis) and depresses feed in-
take. Severe hypercalcemia (plasma calcium between 150
and 250 mg/L or 3.75-6.25 mM) will begin the process of
metastatic calcification of soft tissues, which may or may
not be reversible. In some cases blood calcium can increase
to the point that the heart stops during systole (plasma cal-
cium above 280 mg/L or 7 mM) (Littledike et al., 1976).
These definitions of hypercalcemia do not apply to laying
hens — their total plasma calcium content is typically 200-
400 mg/L or 5-10 mM. However, their ionized calcium con-
tent is 40-50 mg/L or 1-1.25 mM, similar to other animals
(Puis, 1994).
In cattle, oral calcium drenches are used to prevent and/or
treat the hypocalcemia that is common in dairy animals
around the time of calving and the onset of lactation. Cal-
cium chloride and calcium propionate are very soluble cal-
cium salts that have been used widely for this purpose
(Jonsson and Pehrson, 1970; Goff et al., 1996). Administer-
ing a concentrated solution that supplied 50 g of calcium
from calcium chloride into the oral cavity increased plasma
calcium by 30-40 mg/L or 0.75-1.0 mM, which was main-
tained for 4-6 hours. Administering 100 g of calcium from
calcium chloride increased plasma calcium by 60-80 mg/L
(1.5-2.0 mM), which stayed elevated for 6-8 hours. These
doses did not cause the toxic effects associated with severe
hypercalcemia (Jonsson and Pehrson, 1970; Goff and Horst,
1994). However, it was noted that repeated doses of the
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MINERAL TOLERANCE OF ANIMALS
higher quantities of calcium chloride induced a life-threatening
metabolic acidosis, a result of the chloride anion being
absorbed along with the calcium (Goff and Horst, 1993).
The use of chloride salts of calcium has also been associated
with erythema and necrosis of the abomasum and rumen
(Wentink and van den Ingh, 1992). Using calcium propi-
onate as the source of calcium has similar effects on plasma
calcium concentration but does not cause metabolic acidosis
(Goff and Horst, 1994; Pehrson et al., 1998). Placement of
the calcium into the back of the pharynx can elicit closure of
the esophageal groove in cattle, allowing a proportion of the
solution being administered to bypass the rumen. This causes
a greater increase in blood calcium than occurs if the cal-
cium is placed into the rumen via use of a tube or hose end-
ing in the rumen (Goff and Horst, 1993). Cows receiving
146 g calcium as a drench delivered into the esophagus (be-
yond the pharynx) on the day of calving as calcium propi-
onate had rapid increases in plasma calcium, with no delete-
rious effects noted. Cows receiving 219 g calcium as calcium
propionate also had rapid increases in plasma calcium. The
hypercalcemia was not considered severe and lasted less than
24 hours. However, it was accompanied by profound hypo-
magnesemia, which was considered an undesirable effect.
Calcium propionate delivered into the esophagus at a quan-
tity of 1.36 kg (supplying 285 g calcium) caused severe hy-
percalcemia in one of four cows given this dose at calving.
The same dose given to two steers was found to be lethal in
both (Goff et al., 2002), suggesting the calcium demands of
lactation offered some protection from the development
of acute severe hypercalcemia following oral administration
of calcium.
Administering 50 g calcium from calcium carbonate to
dairy cows did not alter blood calcium concentration, sug-
gesting that the more soluble the form of calcium adminis-
tered in a single oral dose the greater the risk of hypercalce-
mia developing (Goff and Horst, 1993).
Calcium polysulfide (lime sulfur), used to control fungal
diseases in trees and shrubs, has the potential for accidental
incorporation into diets as a calcium source. The animals
could become sick from the metabolic acidosis induced by
the anionic portion of the calcium polysulfide molecule. The
calcium itself is not the toxic moiety (Horowitz et al., 1997).
Acute
In animals with intact calcium homeostatic mechanisms,
short-term increases in dietary calcium are very well toler-
ated. The production of 1, 25 -dihydroxy vitamin D will be
downregulated to decrease intestinal calcium absorption of
dietary calcium. If kidneys are functioning properly, any
excess calcium that is absorbed will be rapidly excreted with
the urine. In the horse and rabbit the intestine is not a regula-
tory point of calcium homeostasis. Intestinal calcium absorp-
tion mechanisms are always turned on in these species, and
feeding high dietary calcium increases the amount of cal-
cium that enters the blood. Instead, these species use renal
calcium excretion to control blood calcium concentration.
During renal failure these species are in danger of develop-
ing hypercalcemia even when dietary calcium is within nor-
mal limits.
Young growing pigs may be more likely than other spe-
cies to develop hypercalcemia with increasing dietary cal-
cium (Reinhart and Mahan, 1986; Hall et al., 1991). In one
case report, a 5.62 percent calcium diet was accidentally fed
to piglets after weaning (the requirement was about 0.8 per-
cent diet calcium). Several of the piglets were severely hy-
percalcemic with blood calcium greater than 200 mg/L
(5 mM). All grew poorly and had severely reduced feed in-
take. They were dehydrated, had markedly dry and hard fe-
ces, and were drowsy (Kamphues et al., 1989). In this case,
dietary calcium concentration was high enough to permit cal-
cium to be absorbed by the paracellular, vitamin-D indepen-
dent pathway at a greater rate than the kidneys could excrete
the calcium.
Chronic
Feeding excessive dietary calcium long term is generally
not associated with any specific calcium-based toxicity. Hy-
percalcemia generally does not occur if calcium homeostatic
mechanisms are intact. The main effect directly attributable
to calcium is a reduction in feed intake as more calcium min-
eral is added to the diet. This may simply be a palatability
issue or it could be mediated by calcitonin, a hormone pro-
duced in the gut following a meal, and by thyroid C-cells, in
response to even slight elevations of calcium concentration.
Excessive calcitonin can inhibit feed intake (Freed et al.,
1979). A second common effect of calcium in the diet is to
reduce the availability of other minerals in the diet, such as
phosphorus or zinc, especially if the animal is receiving a
diet that is marginally adequate in these other minerals.
Rabbits can be fed as much as 4.5 percent calcium diets
with no ill effects (Chapin and Smith, 1967). Horses fed di-
ets that were 2.5 percent calcium for four years exhibited no
ill effects provided the diets also had adequate phosphorus
(Jordan et al., 1975). Renal excretion of calcium increases
with increased dietary calcium concentration in rabbits and
horses to prevent development of hypercalcemia and its at-
tendant problems (Schryver et al., 1974).
Feed intake in dogs and cats is largely dictated by energy
content of the diet and therefore feeding standards for dogs
and cats often express calcium and phosphorus contents of
diets in terms of g/1,000 kcal metabolizable energy. For this
report, the diet calcium levels will be expressed as g/kg diet
DM. If the original literature cited expressed diet calcium
only in terms of diet energy, the assumption was made that
typical dog and cat diets are 4,000 kcal ME/kg DM. For
puppies, the dietary calcium and phosphorus allowances are
12 g Ca and 10 g P/kg DM (NRC, 2006). For kittens, the
dietary calcium and phosphorus allowances are 8 g Ca and
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CALCIUM
101
7.2 g P/kg DM (NRC, 2006). These allowances decrease
with age as growth slows in the animals.
In large-breed dogs, bone growth is especially rapid the
first three months of life. Disturbances in endochondral ossi-
fication are a frequent cause of clinical problems in the giant
breed dogs, particularly in Great Danes. Giant breed dogs
fed high calcium diets may be at greater risk of developing
osteochondrosis, rickets, and other bone problems than dogs
fed lower calcium diets, especially if the diet provides
enough energy and protein to support rapid growth, or is
marginal in phosphorus. Ad libitum feeding may increase
the risk of osteochondrosis over feed restriction, where
growth is slowed (Hedhammer et al., 1974). Feeding Great
Dane puppies diets that were 2.72 percent calcium and 0.9
percent phosphorus greatly increased the incidence of osteo-
chondrosis and skeletal problems and caused significant hy-
pophosphatemia in some animals (Hazewinkel et al., 1985;
Goedegebuure and Hazewinkel, 1986). If dietary phospho-
rus is increased along with the dietary calcium, the negative
effects of dietary calcium are largely, but not entirely, nulli-
fied (Weber et al., 2000; Lauten et al., 2002). Schoenmakers
et al. (2000) concluded that feeding increased diet calcium
alone decreased the amount of phosphorus available for bone
formation, which resulted in rachitic lesions, while increas-
ing both diet calcium and phosphorus increased the risk of
osteochondrosis lesions in fast-growing Great Danes. When
the diet calcium to phosphorus ratio exceeds 2: 1 there is risk
of increased osteochondrosis in the Great Dane breed
(Hazewinkel et al., 1991; Schoenmakers et al., 2000). The
Great Dane breed may be rather unique in its sensitivity to
dietary calcium concentration, as Giant Schnauzers fed simi-
lar diets show no osteochondrosis bone lesions (Weber et al.,
2000). Miniature poodles fed diets that were as high as 3.3
percent calcium and just 0.9 percent phosphorus still man-
aged to grow well and had no bone problems, though they
did have a temporary decrease in feed intake at 11 weeks of
age when compared to poodle pups fed a 1.1 percent cal-
cium, 0.9 percent phosphorus diet (Nap et al., 1993). A sum-
mary of trials performed by a commercial pet food manufac-
turer demonstrated that puppies across a variety of breeds
exhibited no skeletal problems when fed up to 2.0 percent
calcium on a DM basis — even if diet phosphorus was not
increased. When diet calcium exceeded 2.3 percent, feed in-
take and growth were depressed in many breeds (Laflamme,
2000).
Few studies have examined the effects of elevated diet
calcium in cats. Howard et al. (1998) observed reduced feed
intake and growth in kittens fed 2.3 percent calcium diets.
The kittens also exhibited pronounced hypomagnesemia.
Calves are typically fed milk (whole milk is approxi-
mately 0.95 percent calcium on a DM basis) or milk replacer
that is 0.9-1 . 1 percent calcium. At weaning, the diet calcium
is generally reduced to 0.6-0.7 percent. Maintenance diets
for adult cattle are typically 0.45-0.6 percent calcium. In
lactating cows the diet calcium is increased to 0.7-0.9 per-
cent calcium to accommodate lactational demands for cal-
cium. In cattle, dietary calcium concentrations greater than 1
percent have been associated with reduced DM intake and
lower performance (Miller, 1983). The amount of mineral
added to some of these rations to achieve the higher calcium
levels is often unpalatable and also replaces energy or pro-
tein that could be used by the animal for growth or other
functions. Beede et al. (2001) fed 0.47, 0.98, 1.52, and 1.95
percent calcium diets to cows in late gestation that were re-
ceiving a high-chloride diet to prevent milk fever. Cows fed
1.5 percent calcium diets tended to eat less than cows of-
fered 0.98 percent or 0.47 percent calcium diets, while those
fed the 1 .95 percent calcium diet had significantly lower feed
intake. Dietary calcium did not influence the degree of hy-
pocalcemia experienced at calving or milk production in the
subsequent lactation.
When diets suitable for lactating cows (0.85 percent cal-
cium) were fed to mature bulls for prolonged periods, the
bulls were reported to have developed osteopetrosis of the
bone and ultimo branchial tumors of the thyroid gland, pre-
sumably from excessive calcitonin production (Krook et al.,
1969). Similarly, high calcium diets fed to cows in late ges-
tation were thought to lead to benign hyperplasia of the thy-
roid gland and excessive secretion of calcitonin. The high-
calcium diets were also found to depress secretion of
parathyroid hormone prior to calving (Black et al., 1973;
Yarrington et al., 1977). Other experiments demonstrated
that very low calcium diets fed in late gestation could pre-
vent milk fever, a condition of severe hypocalcemia experi-
enced by some cows at the onset of lactation (Boda and Cole,
1954; Goings et al., 1974; Green et al., 1981). These obser-
vations gave rise to the theory that high calcium diets fed to
the late gestation dairy cow caused milk fever to develop.
Studies now suggest milk fever is instead caused by exces-
sive dietary potassium or sodium, not calcium (Ender et al.,
1971; Goff and Horst, 1997). The high cation diets induce a
metabolic alkalosis in the cow, which interferes with par-
athyroid hormone function, predisposing the cow to hypo-
calcemia (Gaynor et al., 1989; Phillippo et al., 1994).
Calcium, fed in the form of limestone, has some rumen
buffering activity in cattle. Wheeler and Noller (1976) fed
lactating cows up to 1 .48 percent calcium diets. Though there
was a small decrease in feed intake with the higher calcium
diets, there was no effect on fat-corrected milk production
and there was more efficient use of dietary starch. Similar
observations were made by Clark et al. (1989). However, in
their study, feeding a diet that was 3.5 percent calcium car-
bonate (estimated to be 1 .7 percent calcium) did significantly
decrease feed intake, though fat-corrected milk production
was not affected.
Very high diet calcium concentration can reduce digest-
ibility of the diet. Ammerman et al. (1963) found that diets
that were 4.4 percent calcium reduced protein and energy
digestibility of the ration of beef steers. In another study,
veal calves aged 8 weeks were fed iso-energetic amounts of
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MINERAL TOLERANCE OF ANIMALS
0.71 percent or 1.16 percent calcium milk replacers for a
period of 10 weeks. The extra calcium was added in the form
of calcium formate. Feces were collected during the final
week of the trial. The high calcium diet raised the amount of
energy contained in excreted feces by 70 percent. The extra
fecal energy output was mostly in the form of crude fat, pre-
sumably from formation of insoluble calcium soaps of the
fatty acids in the diet. The high versus low calcium intake
not only depressed apparent digestibility of total lipids but
also that of crude protein, carbohydrates, and ash (lower ash
digestibility was largely a result of dietary calcium that was
not absorbed). However, the final body weight of the two
dietary groups was similar, so it is difficult to use these data
to suggest that 1.16 percent calcium (DM) in milk replacer is
necessarily excessive (Xu et al., 1999). When weaned calves
were fed diets that were 0.34 percent phosphorus and either
0.17, 0.67, 1.31, or 2.35 percent calcium, all grew normally
during the four-week trial, suggesting little effect on diet
digestibility. However, in those calves fed the 1.31 or 2.35
percent calcium diets, there was a reduction in soft tissue
levels of trace minerals such as zinc, manganese, and cop-
per. The 2.35 percent calcium diet also depressed blood
phosphorus concentration to levels that might ultimately
have led to rickets had the study gone on longer (Alfaro et
al., 1988). Fontenot et al. (1964) demonstrated that diets con-
taining 1.2 percent calcium could induce zinc deficiency in
lambs receiving no supplemental zinc. However, if zinc were
added to the diets, the lambs could be fed 2.4 percent cal-
cium diets with no effects on growth.
In pigs, feed intake and growth are markedly reduced
whenever the dietary calcium:phosphorus ratio exceeds 3: 1
(Reinhart and Mahan, 1986). Thus, starting pigs requiring
0.60 percent dietary phosphorus would be expected to suffer
reduced feed intake and growth when dietary calcium ex-
ceeds 1.8 percent, and finishing pigs requiring 0.45 percent
dietary phosphorus would suffer reduced growth rate when
dietary calcium exceeds 1.35 percent, unless diet phospho-
rus was also increased. High calcium content is reported to
reduce diet digestibility in pigs. Zimmerman et al. (1963)
and Combs et al. (1966) found that addition of calcium to the
diet of baby pigs reduced growth, feed efficiency, DM di-
gestibility, and bone mineralization, especially when the cal-
cium level exceeded 1 .0 percent of the diet. These effects
were observed even though the dietary calcium to phosphorus
ratios were less than 2:1. The experiments of Zimmerman et
al. (1963) and Combs et al. (1966) suggest that the maximal
tolerable dietary calcium level is 1.0 percent, although the
study by Reinhart and Mahan (1986) demonstrated that
increasing dietary phosphorus could increase the tolerable
dietary calcium level.
Fangauf et al. (1961) and Urbanyi (1960) in separate ex-
periments fed chicks diets that ranged from 1.2 to 6.5 per-
cent calcium. Levels above 2 percent depressed feed intake
and weight gain and increased mortality rate. Shane et al.
(1969) report that visceral gout and nephrosis occurred in
growing pullets fed a 2.5 percent calcium diet from 8-20
weeks of age. Hurwitz et al. (1995) fed chicks of fast-grow-
ing (Cobb) and slow-growing (Leghorn) breeds diets that
were 0.4, 0.6, 0.8, 1.0 (considered the required level of di-
etary calcium), 1.5, and 2.0 percent calcium with 0.7 percent
phosphorus (considered the required phosphorus level).
Chicks of the slow-growing breed grew equally well with
1.0, 1.5, and 2.0 percent calcium diets. However, chicks of
the fast-growing breed fed 2 percent dietary calcium weighed
significantly less than fast-growing chicks fed the 1.0 per-
cent calcium diet. When dietary phosphorus was increased
to 0.9 percent the negative effect of the 2 percent calcium
diet on growth was greatly ameliorated, but not eliminated.
For hens consuming 100 g feed/day the dietary calcium
requirement is 3.25 percent (NRC, 1994). The 1980 NRC
Mineral Tolerance of Domestic Animals set 4 percent diet
calcium as a maximum tolerable level in laying hens based
largely on the work of Gutowska and Parkhurst (1942), who
reported that laying hens fed a 3.95 percent calcium diet suf-
fered reduced egg production and feed efficiency, though
eggshell strength was not affected. However, in another
study, laying hens fed diets as high as 5 percent calcium
showed no ill effects (Harms and Waldroup, 1971). In fact,
recent studies with modern high-producing hens suggest the
calcium requirement of laying hens may be closer to 5 per-
cent calcium (Bar et al., 2002).
The greater potential risk from high-calcium diets is in-
terference with absorption of other minerals, causing defi-
ciency of these minerals, despite their inclusion in the diet at
levels that would ordinarily be considered sufficient. High-
calcium diets can interfere with the absorption of phospho-
rus, which is of particular concern in nonruminant animals.
Much of the phosphorus of plant seed origin fed to these
animals is bound to an inositol backbone. Up to 6 phosphate
molecules can be bound to each inositol molecule, forming
inositol 1,2,3,4,5,6-hexakis dihydrogen phosphate, also
known as phytate. Nonruminant animals vary in their ability
to digest phytate to free up the phosphorus. Poultry can, un-
der some extreme circumstances, use as much as 50 percent
of dietary phytate phosphorus. However, in general, swine
and poultry hydrolyze only a small portion of the phytate
phosphorus they are fed. The endogenous phytase of most
nonruminant animals exists primarily in the mucosa of the
small intestine and the phytate must be soluble at the pH
found in the small intestine for the phytase to effectively
hydrolyze the phytate. Phytases originating from feed ingre-
dients or microbial synthesis are also most active when the
phytate is soluble. Unfortunately the phytate molecule, with
its protruding phosphate, is a highly negatively charged par-
ticle. Cations (and in some cases proteins or starches) can
then form bonds with the phosphate moieties. The propen-
sity to form bonds with a cation is so great that much of the
feedstuff phytate ingested is already chelated to cations, such
as potassium, iron, calcium, magnesium, zinc, and copper.
Phytate bound to divalent cations, especially calcium, is rela-
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CALCIUM
103
lively insoluble at the pH of the small intestine and is there-
fore resistant to intestinal mucosa phytase digestion. Phytate
bound to calcium is soluble at the acidic pH of the stomach
and will be digested by phytases of microbial origin that are
active at low pH. Calcium, being the most prevalent divalent
cation in many diets, is commonly chelated to phytate, but
other divalent and trivalent minerals can also become bound
to phytate. A single phytate molecule can bind more than
one divalent cation. The more cations attached to the phytate
the lower the solubility of the complex and the less prone it
is to hydrolysis by phytases (Wise, 1983). For this reason,
therefore, the greater the calcium content of the diet the less
available phytate phosphorus is to the nonruminant animal.
In ruminants the activity of microbial phytase, either within
the rumen or as the ingesta passes through the abomasum or
true stomach, does a thorough job of digesting phytate and
freeing the bound minerals. Therefore high calcium diets fed
to ruminants do not interfere with phosphorus and trace min-
eral absorption to the same extent as in nonruminants
(Kincaid, 1979).
In nonruminants only small amounts of phytate are di-
gested by the endogenous phytases of the gastrointestinal
tract. Dietary calcium reduces the efficacy of intestinal
phytase and also the efficacy of phytase of fungal origin
added to the diet. In poultry and swine, the ability of calcium
to interfere with phytase activity occurs even at dietary cal-
cium concentrations considered essential to meet the calcium
needs of the bird (0.9 percent calcium diets) (Atia et al.,
2000; Applegate et al., 2003) or pigs (0.8 percent calcium
diets) (Sandberg et al., 1993; Lei et al., 1994). However,
inhibition of phytate digestion becomes more critical at di-
etary calcium levels that exceed the requirement of the ani-
mal. For example, in fast-growing broilers, increasing di-
etary calcium from 0.8 to 2.0 percent reduced growth rate
and caused pronounced hypophosphatemia. This effect
seemed to be due to decreased absorption of phosphate from
the diet of the birds (Hurwitz et al., 1995). It was also noted
that increasing diet calcium in broilers using calcium car-
bonate caused hypophosphatemic rickets, while the same
level of diet calcium achieved by supplementation with
dicalcium phosphate did not. This suggests that the bone
problems arose because calcium carbonate interfered with
phosphorus metabolism rather than as a direct effect of cal-
cium toxicity (Ogura, 1981).
Feeding excessive calcium could interfere with trace min-
eral absorption (especially zinc and other trace minerals bound
to phytate) and replaces energy or protein the animal might
better use for increased production. In swine, excess calcium
greatly reduces zinc availability, especially if phytate is high
(Morgan et al., 1969). A diet containing 1.71 percent calcium
and 68 mg Zn/kg fed to growing boars induced parakeratosis
(abnormal keratinization of the skin) due to zinc deficiency.
The dietary zinc requirement of boars at this age is 50 mg/kg
diet, so this diet would otherwise have been considered more
than adequate in zinc (Beilage et al., 1992).
High dietary calcium may also increase the requirement
for vitamin K. Pigs fed a 2.7 percent calcium diet based on
corn and soybean meal with no supplemental vitamin K de-
veloped internal hemorrhaging and died within 28 days.
Supplementing the diet with 5 mg menadione prevented fur-
ther problems (Hall et al., 1991).
In fish, dietary calcium can also interfere with trace min-
eral absorption and retention (Hardy and Shearer, 1985;
Kaushik, 1995). For example, Redlip mullet (Liza
haematocheila) fed a 2.5 percent calcium diet were reported
to have reduced bone zinc, manganese, and iron content
when compared to fish fed a 0.2 percent calcium diet
(Hossain and Furuichi, 2000). High water calcium concen-
tration also reduces gill uptake of zinc from the water. Al-
though this effect might induce a secondary zinc deficiency,
it may be used as a means of protecting fish when water is
contaminated with excessive zinc or other heavy metals
(Barron and Albeke, 2000).
Female rats given 0.50, 0.75, 1.00, or 1.25 percent dietary
calcium as calcium carbonate in AIN-76A diets for 6 weeks
before mating, during mating, and for 20 days of gestation
had dose-related linear decreases in the iron content of the
liver, and in the zinc, iron, and magnesium contents of the
kidney. Even though the highest calcium diet represents only
a moderate increase in calcium above requirement, the fe-
tuses from these rats had dose-related decreases in their
whole-body contents of phosphorus, iron, copper, and mag-
nesium (Shackelford et al., 1994).
Factors Influencing Toxicity
One factor that can upset calcium homeostasis is exces-
sive (toxic) intake of vitamin D, or ingestion of plants con-
taining glycosides of 1, 25 -dihydroxy vitamin D. In this case
the intestinal calcium absorption mechanisms are fully en-
gaged and diets high in calcium are more rapidly able to
induce hypercalcemia and metastatic calcification than low
calcium diets.
In the horse and the rabbit, compromised renal function
will not allow excretion of excess calcium absorbed from the
diet and hypercalcemia will develop.
TISSUE LEVELS
Normal total plasma or serum calcium concentrations are
between 90 and 1 10 mg/L or 2.25-2.75 mM for many mam-
mals and growing birds. Horses and rabbits tend to be
slightly higher, and up to 1 30 mg Ca/L plasma or serum may
be considered normal (Table 10-2). The rabbit, in particular,
will exhibit higher blood calcium concentration as dietary
calcium content increases. Laying hens have a special cal-
cium binding protein circulating in their blood, allowing
them to rapidly deposit calcium into the oviduct during egg-
shell formation, and they will normally have total plasma or
serum calcium concentrations ranging from 180-360 mg/L
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104
MINERAL TOLERANCE OF ANIMALS
or 4.5-9 mM. Ionized calcium concentration — which is cal-
cium that is not bound to proteins or other organic moieties
in the blood — is relatively constant in all species, including
poultry that are laying eggs, and is usually 40-60 mg Ca/L
(1-1.5 mM) plasma or serum.
Elevations in blood calcium concentration are common
in cases of acute calcium toxicity. Plasma total calcium con-
centrations exceeding 280 mg/L will cause cardiac arrest in
many species, since this often means ionized calcium con-
centration is also greatly increased. Typically these high
blood calcium values are only encountered when animals
are receiving intravenous calcium treatments at too high a
dose or too rapid a rate of administration. Blood calcium
concentrations exceeding 150 mg/L (3.75 mM) for more than
12-24 hours will begin to cause metastatic calcification of
soft tissues, particularly the kidneys, stomach, and vascula-
ture, which would severely compromise renal function
within 1-2 weeks. Chronically elevated blood calcium con-
centrations above 120 mg/L (3 mM) can also cause meta-
static calcification of soft tissues but the process is slower
and would occur over weeks to months. Normal liver and
kidney calcium content is generally below 200 mg/kg wet
weight or about 800 mg/kg on a dry weight basis. Kidney or
liver tissue calcium contents greater than 300 mg/kg wet
weight would indicate metastatic calcification. Chronically
elevated blood calcium concentrations can occur with ex-
tremely high calcium diets, but this is rare. More commonly
it is a sequelae of vitamin D intoxication, primary hyperpar-
athyroidism, or, in some species such as the horse and rabbit,
a consequence of renal failure. Urine calcium concentrations
are a poor indicator of dietary calcium excess. Bone ash and
bone calcium are sensitive to calcium deficiency states but
do not reflect a calcium toxicity situation.
Cow's milk contains approximately 1.2 g Ca/L. Sheep
milk contains approximately 2.0 g Ca/L and goat milk about
1 .5 g Ca/L. These values change with breed slightly but they
are not impacted by dietary calcium. Sow's milk is about
1.3 g Ca/L. Because sow's milk is about 20 percent dry
matter, a pig that is consuming only sow's milk is receiving
a diet that is approximately 0.65 percent calcium on a dry
matter basis.
MAXIMUM TOLERABLE LEVELS
Single Dose
The criteria used to determine the maximum tolerable
single oral dose of calcium is that quantity of calcium that is
not expected to cause severe hypercalcemia, defined as
plasma calcium greater than 150 mg/L (3.75 mM) for more
than 12 hours, as this degree of hypercalcemia appears to
have severe consequences on feed intake, renal function, and
hydration state. The maximum tolerable dose of calcium that
can be given once to adult cattle as a drench without causing
life-threatening hypercalcemia is 150 g calcium. This would
be approximately equivalent to 0.25 g Ca/kg BW per os.
Data for making a recommendation for any other species do
not exist, and the safety of 0.25 g Ca/kg is likely reduced in
nonruminant animals. In adult ruminants, the rumen fluids
tend to dilute the calcium administered so that the concentra-
tion of calcium overlying intestinal mucosa is lower, render-
ing passive transport of calcium as less efficient (Goff and
Horst, 1994). In nonruminants, the lack of dilution of the
administered calcium before it reaches the small intestine
would allow a greater portion of the administered calcium
available for passive absorption.
In some cases, the anion accompanying the calcium will
prove more toxic (due to induction of metabolic acidosis or
caustic damage to tissues) than the calcium in the salt, reduc-
ing the tolerable amount of that particular calcium salt. For
instance, the chloride of calcium chloride can induce a meta-
bolic acidosis at a dose below the level where the calcium
causes life-threatening hypercalcemia.
Acute
The criteria used to determine the maximum tolerable
acute dietary calcium level is that quantity of calcium that is
not expected to cause severe hypercalcemia, defined as
plasma calcium greater than 150 mg/L (3.75 mM), for more
than 1 2 hours when animals are introduced to the diet.
Very high concentrations of dietary calcium are tolerated
by all species for short periods, provided the animal's kid-
neys are functioning or there is not excessive stimulation of
1, 25 -dihydroxy vitamin D receptors in the intestine of the
animal (vitamin D intoxication, ingestion of plants contain-
ing glycosides of 1,25 -dihydroxy vitamin D) causing uncon-
trolled absorption of calcium across the gut. It is likely that
there is a dietary calcium level that will cause acute toxicosis
from excessive hypercalcemia in every species if animals
could be induced to consume these diets. However, for most
species, acute toxicosis due to hypercalcemia has not been
reported and a maximal tolerable level based on this crite-
rion cannot be supported by data. This likely reflects the
observation that feed intake decreases as the concentration
of calcium increases in the diet (as in the studies of Reinhart
and Mahan, 1986, and of Beede et al., 2001). Feed intake
often declines quickly once diet calcium levels exceed 2-3
percent (though laying hens routinely consume 4.5 percent
calcium diets with no ill effects). This is well below the 5
percent calcium diet level associated with acute toxicity
when fed to piglets, which is the only documented instance
of a high calcium diet causing acute toxic hypercalcemia in
any species (Kamphues et al., 1989).
Chronic
If feed intake is significantly reduced by addition of cal-
cium to the diet, animal growth will suffer. In assessing the
maximum tolerable level of chronic dietary calcium expo-
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CALCIUM
105
sure, a reduction in feed intake accompanied by a reduction
in performance (growtti, milk or egg production, reproduc-
tion) will be considered the criteria comprising evidence of
calcium toxicosis. More stringent criteria could have been
used based on the evidence that addition of calcium to diets
reduces the availability of phosphorus and trace minerals to
nonruminants. Unfortunately, this effect occurs even at cal-
cium concentrations in the diet that are suggested to be the
required concentrations of calcium in the diet of
nonruminants. Under these criteria, any time the calcium
content of the diet exceeds the amount required to meet the
calcium needs of the body there is a detrimental effect, be-
cause the amount of phosphorus and trace mineral required
by the animal may be increased. Though these effects are
generally of negligible consequence, there is a point at which
these effects of calcium excess become intolerable and
should be reduced. In nonruminant animals with fast growth
rates (broilers, turkey poults, pigs, rats) the maximum toler-
able calcium would be considered, by this criteria, to be very
close to the calcium requirement of the animal because of
the effect diet calcium has on use of phytate-bound minerals.
These effects were generally not considered in determining
the maximum tolerable levels, since most practical diets pro-
vide enough excess phosphorus or trace mineral to allow the
animal to tolerate minor calcium effects on their availability.
However, when studies demonstrated that the reduction in
availability of secondary minerals caused by excess diet cal-
cium resulted in increased clinical disease, such as rickets or
parakeratosis, then the induction of secondary mineral defi-
ciency was considered a significant criterion for determin-
ing the maximum tolerable dietary calcium level.
In preruminant calves, diet calcium concentration ex-
ceeding 1.2 percent DM can interfere with fat use, but does
not impair growth or feed intake. The maximum tolerable
dietary calcium for suckling calves is at least 1.2 percent
and likely higher. In cattle, sheep, goats (and presumably
other ruminants) the effects on phytate digestion are incon-
sequential. Adult cows were fed diets containing up to 1.5
percent calcium (in several studies), with little effect on
feed intake and no significant effect on performance. Diets
containing 1.9 percent calcium or greater can cause a sig-
nificant decrease in feed intake in cattle. Although high
calcium in the diet causes zinc deficiency in sheep fed diets
without added zinc, few data demonstrate a detrimental ef-
fect of high calcium diets in sheep or goats. Therefore, for
ruminants, the maximum tolerable dietary calcium level is
set at 1.5 percent. In the horse and rabbit (and presumably
other hind gut fermenters), 2 percent calcium is the maxi-
mum tolerable level, provided sufficient available phospho-
rus is included in the diet.
For growing poultry chicks, the maximum tolerable di-
etary calcium level is 1.5 percent. Diets containing 2 per-
cent calcium will affect growth and bone ash of fast-grow-
ing chicks when diets contain required levels of
phosphorus. High-producing laying hens can tolerate 5 per-
cent calcium diets. Growing pigs have the lowest tolerance
for dietary calcium, and detrimental effects are possible
whenever the dietary calcium to phosphorus ratio exceeds
2:1. The maximum tolerable level of dietary calcium for
pigs is 1 percent, though increasing dietary phosphorus can
increase the maximum tolerable level to some extent. In
fish the data are too limited to allow an estimate of the
maximum tolerable dietary calcium concentration. The only
data available suggest that diets that contain 2 percent or
greater calcium interfere with use of trace minerals and
affect growth when compared to diets that contain 0.2 per-
cent calcium. Since fish are often fast growing, especially
when young, and most are unable to digest phytate, it would
seem reasonable to believe that dietary calcium levels re-
sulting in calcium to phosphorus ratios less than 2: 1 would
not cause any detrimental problems, similar to other single-
stomached species. Because most fish require 0.45 percent
phosphorus diets (Lovell, 1991), the maximum tolerable
dietary level is presumed to be 0.9 percent.
For most breeds of dog, the maximum tolerable dietary
calcium concentration is at least 2 percent, including grow-
ing puppies of larger breeds. The tolerable level can be in-
creased somewhat for most dogs provided the diet calcium
to phosphorus ratio does not exceed 3:1. Most breeds will
suffer a reduction in feed intake and growth if diet calcium
exceeds 2.3 percent. For Great Dane and perhaps some other
large breed puppies, rickets may occur if the diet calcium to
phosphorus ratio exceeds 4:1. The maximum tolerable
dietary calcium concentration for these giant breeds is 1 . 1
percent unless phosphorus is also added to the diet to bring
diet calcium to phosphorus ratios between 1.2:1 and 1 .4: 1 . If
phosphorus is added to maintain this ratio, even Great Danes
can be expected to tolerate up to 2.0 percent calcium diets.
Diets containing more than 2.3 percent calcium risk in-
creased occurrence of osteochondrosis in these breeds, even
if dietary phosphorus is raised. In cats 1 percent calcium
diets are well tolerated and result in optimal bone density
(Pastoor et al., 1994). Feeding cats 2.3 percent calcium diets
reduced growth rate and depressed feed intake and also
caused a negative magnesium balance (Howard et al., 1998).
There are no data to allow a more specific recommendation.
FUTURE RESEARCH NEEDS
Only with extremely high dietary calcium is it likely that
hypercalcemia and its attendant problems will become mani-
fest. However, it is increasingly clear that feeding animals
more calcium than they require to meet their physiological
requirements can reduce the efficiency of absorption of sev-
eral other minerals, which might result in deficiencies of
these minerals secondary to excess dietary calcium. Research
to define the calcium level at which significant interaction
with use of these other nutrients, in particular phytate phos-
phorus and zinc, could increase awareness of these subtle
detrimental dietary calcium effects. Unfortunately, because
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706
MINERAL TOLERANCE OF ANIMALS
the consequences of dietary calcium insufficiency can be
severe and because calcium is an inexpensive feed additive,
the tendency of nutritionists formulating animal diets is to
provide calcium in excess of levels needed to meet the
animal's requirement. To keep calcium to phosphorus ratios
optimal, excess diet calcium encourages oversupplementa-
tion of dietary phosphorus, the most expensive and environ-
mentally damaging of minerals added to animal diets.
SUMMARY
Animals can tolerate relatively high amounts of dietary
calcium for relatively long periods. Using hypercalcemia as
the primary indicator of acute toxicity resulting from exces-
sive absorption of dietary calcium, the level of dietary cal-
cium that would cause this effect is generally so high that
feed intake of the animal would be greatly reduced, limiting
the development of hypercalcemia. When animals are fed
calcium above the maximum tolerable levels over a longer
period of time, the main effects observed would include in-
terference with use of other minerals, especially phosphorus
and zinc, and/or a significant reduction in feed intake affect-
ing performance.
REFERENCES
Aciierman, L. 1984. Demodicosis in cats. Mod. Vet. Pract. 65(10):751-752.
Alfaro, E., M. W. Neathery, W. J. Miller, C. T. Crowe, R. P. Gentry, A. S.
Fielding, D. G. Pugh, and D. M. Blackmon. 1988. Influence of a wide
range of calcium intakes on tissue distribution of macroelements and
microelements in dairy calves. J. Dairy Sci. 71:1295-1300.
Ammerman, C. B., L. R. Ai'rington, M. C. Jayaswal, R. L. Shirley, and G.
K. Davis. 1963. Effect of dietary calcium and phosphorus levels on
nutrient digestibility by steers. J. Anim. Sci. 22:248-252.
Applegate, T. J., R. Angel, and H. L. Classen. 2003. Effect of dietary cal-
cium, 25-hydroxycholecalciferol, or bird strain on small intestinal
phytase activity in broiler chickens. Poult. Sci. 82:1140—1148.
Atia, F. A., P. E. Waibel, I. Hermes, C. W. Carlson, M. M. Walser. 2000.
Effect of dietary phosphorus, calcium, and phytase on performance of
growing turkeys. Poult. Sci. 79:231—239.
Bar, A., V. Razaphkovsky, and E. Vax. 2002. Re-evaluation of calcium and
phosphorus requirements in aged laying hens. Br. Poult. Sci.
43:261-269.
Barron, M. G., and S. Albeke. 2000. Calcium control of zinc uptake in
rainbow trout. Aquatic Toxicol. 50:257-264.
Beede, D. K., T. E. Pilbeam, S. M. Puffenbarger, and R. J. Tempelman.
2001. Peripartum responses of Holstein cows and heifers fed graded
concentrations of calcium (calcium carbonate) and anion (chloride) three
weeks before calving. J. Dairy Sci. 84(Suppl. 1):83.
Beilage, E., E. Kienzle, and E. Muller. 1992. Symptoms and course of a
parakeratosis outbreak in a boar-raising facility. Tieraerztl. Prax.
20:265-269.
Black, H. E., C. C. Capen, J. T. Yarrington, and G. N. Rowland. 1973.
Effect of a high-calcium prepai'tal diet on calcium homeostatic mecha-
nisms in thyroid glands, bone, and intestine of cows. Lab. Invest.
29:437^148.
Boda, J. M., and H. H. Cole. 1954. The influence of dietary calcium and
phosphorus on the incidence of milk fever in dairy cattle. J. Dairy Sci.
37:360-372.
Bourdeau, J. E., D. A. Schwer-Dymerski, P. H. Stern, and C. B. Langman.
1986. Calcium and phosphorus metabolism in chronically vitamin D-
deficient laboratory rabbits. Miner. Electrolyte Metab. 12:176—185.
Boyd, C. E. 1979. Water Quality in Warmwater Fish Ponds. Auburn, AL:
Agriculture Experiment Station.
Brommage, R., S. C. Miller, C. B. Langman, R. Bouillon, R. Smith, and J.
E. Bourdeau. 1988. The effects of chronic vitamin D deficiency on the
skeleton in the adult rabbit. Bone 9:131—139.
Bronner, F. 1987. Intestinal calcium absorption: mechanisms and applica-
tions. J. Nutr. 117:1347-1352.
Chapin, R. E., andS. E. Smith. 1967. The calcium tolerance of growing and
reproducing rabbits. Cornell Vet. 57:480^91.
Chavez-Sanchez, C, C. A. Martinez-Palacios, G. Martinez-Perez, and L.
G. Ross. 2000. Phosphorus and calcium requirements in the diet of the
American cichlid Cichlasoma urophlhalmus (Giinther). Aquacult. Nutr.
6(1):1-10.
Clark J. H., A. W. Legge, C. L. Davis, and G. C. McCoy. 1989. Effects of
calcium carbonate on ruminal fermentation, nutrient digestibility, and
cow performance. J. Dairy Sci. 72:493-500.
Combs, G. E., T. H. Berry, H. D. Wallace, and R. C. Crum, Jr. 1966. Levels
and sources of vitamin D for pigs fed diets containing varying quantities
of calcium. J. Anim. Sci. 25:827-830.
Dowe, T. W., J. Matsushima, and V. H. Arthaud. 1957. The effects of ad-
equate and excessive calcium when fed with adequate phosphorus in
growing rations for beef calves. J. Anim. Sci. 16:81 1-818.
Ender, F., I. W. Dishington, and A. Helgebostad. 1971. Calcium balance
studies in dairy cows under experimental induction and prevention of
hypocalcaemic paresis puerperalis. The solution of the aetiology and
the prevention of milk fever by dietary means. Z. Tierphysiol.
Tierernaehi-. Futtermittelk. 28:233-256.
EPA (U.S. Environmental Protection Agency). 1983. Calcium: Method
215.1 (atomic absorption, direct aspiration). Pp. 215.1-215.2 in Meth-
ods for Chemical Analysis of Water and Wastes, EPA-600/4-79-020.
Cincinnati, OH: U.S. EPA.
Fangauf, R., H. Vogt, and W. Penner. 1961. Studies of calcium tolerance in
chickens. Ai'ch. Geflugelk 25:82-89.
Fontenot, J. P., R. F. Miller, andN. O. Price. 1964. Effects of calcium level
and zinc supplementation of fattening lambs rations. J. Anim. Sci.
23:874-875 (Abstr.).
Freed, W. J., M. J. Perlow, and R. J. Wyatt. 1979. Calcitonin: inhibitory
effect on eating in rats. Science 206:850-852.
Frost, H. M. 1964. Dynamics of bone remodeling. Pp. 315-333 in Bone
Biodynamics, H. M. Frost, ed. Boston: Little Brown.
Gaynor, P. J., F. J. Mueller, J. K. Miller, N. Ramsey, J. P. Goff and R. L.
Horst. 1989. Parturient hypocalcemia in Jersey cows fed alfalfa haylage-
based diets with different cation to anion ratios. J. Dairy Sci. 72:2525—
2531.
Goedegebuure, S. A., and H. A. W. Hazewinkel. 1986. Morphological find-
ings in young dogs chronically fed a diet containing excess calcium.
Vet. Pathol. 23:594-605.
Goings, R. L., N. L. Jacobson, D. C. Beitz, E. T. Littledike, and K. D.
Wiggers. 1974. Prevention of parturient paresis by a prepartum, cal-
cium-deficient diet. J. Dairy Sci. 57:1 184-1 188.
Goff, J. P., and R. L. Horst. 1993. Oral administration of calcium salts for
treatment of hypocalcemia in cattle. J. Dairy Sci. 76:101—108.
Goff, J. P, and R. L. Horst. 1994. Calcium salts for treating hypocalcemia:
carrier effects, acid-base balance, and oral versus rectal administration.
J. Dairy Sci. 77:1451-1456.
Goff, J. P, and R. L. Horst. 1997. Effects of the addition of potassium or
sodium, but not calcium, to prepartum rations on milk fever in dairy
cows. J. Dairy Sci. 80:176-186.
Goff, J. P., R. L. Horst, P. W. Jardon, C. Borelli, and J. Wedam. 1996. Field
trials of an oral calcium propionate paste as an aid to prevent milk fever
in periparturient dairy cows. J. Dairy Sci. 79:378-383.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
CALCIUM
107
Goff, J. P., T. F. Brown, S. R. Stokes, C. L. Brawley, and F. R. Valdez.
2002. Titration of ttie proper dose of calcium propionate (NutroCAL) to
be included in an oral drench for fresh cows. J. Dairy Sci. 85(Suppl.
1):189.
Green, H. B., R. L. Horst, D. C. Beitz, and E. T. Littledike. 1981. Vitamin
D metabolites in plasma of cows fed a prepartum low-calcium diet for
prevention of parturient hypocalcemia. J. Dairy Sci. 64:217-226.
Gutowska, M. S., and R. T. Parkhurst. 1942. Studies in mineral nutrition of
laying hens. II. Excess of calcium in the diet. Poult. Sci. 21:321-3278.
Hall, D. D., G. L. Cromwell, and T. S. Stahly. 1991. Effects of dietary
calcium, phosphorus, calcium: phosphorus ratio, and vitamin K on per-
formance, bone strength, and blood-clotting status of pigs. J. Anim. Sci.
69:646-655.
Hardy, R. W., and K. D. Shearer. 1985. Effect of dietary calcium phosphate
and zinc supplementation on whole body zinc concentration of rainbow
trout (Salmo gairdneri). Can. J. Fish. Aquat. Sci. 42:181-184.
Harms, R. H., and P. W. Waldroup. 1971. The effect of high dietary calcium
on the performance of laying hens. Poult. Sci. 50:967-969.
Hazewinkel, H. A., W. E. Van den Brom, A. T. Van 'T Klooster, G.
Voorhout, and A. Van Wees. 1991. Calcium metabolism in Great Dane
dogs fed diets with various calcium and phosphorus levels. J. Nutr.
121(11 Suppl.):S99-106.
Hazewinkel, H. A., S. A. Goedegebuure, and P. W. Poulos. 1985. Influ-
ences of chronic calcium excess on the skeletal development of growing
Great Danes. J. Am. Anim. Hosp. Assoc. 21:377—391.
Hedhammar, A., F. M. Wu, L. Krook, H. F. Schryver, A. De Lahunta, J. P.
Whalen, F. A. Kallfelz, E. A. Nunez, H. F. Hintz, B. E. Sheffy, and G.
D. Ryan. 1974. Overnutrition and skeletal disease. An experimental
study in growing Great Dane dogs. Cornell Vet. 64(2):Suppl 5:5-160.
Horowitz, B. Z., K. Marquardt, and E. Swenson. 1997. Calcium polysulfide
overdose: a report of two cases. J. Toxicol. Clin. Toxicol. 35:299-303
Hossain, M. A., and M. Furuichi. 2000. Essentiality of dietary calcium
supplement in redlip mullet Liza haematocheila. Aquacult. Nutr.
6(l):33-38.
Howard, K., Q. Rogers, and J. Mon'is. 1998. Magnesium requirement of
kittens is increased by high dietary calcium. J. Nutr. 128(Suppl.):2601S—
2602S.
Huang, C. H., W. Y. Lin, and S. M. Wu. 2003. Effect of dietary calcium and
phosphorus supplementation in fish meal-based diets on the growth of
softshell turtles Pelodiscus sinensis (Wiegmann). Aquacult. Res.
34:843-848.
Hurwitz, S., I. Plavnik, A. Shapiro E. Wax, H. Talpaz, and A. Bar. 1995.
Calcium metabolism and requirements of chickens are affected by
growth. J. Nutr. 125:2679-2686.
Jonsson, G., and B. Pehrson. 1970. Trials with prophylactic treatment of
parturient paresis. Vet. Rec. 87(19):575-578.
Jordan, R. M., V. S. Myers, B. Yoho, and F. A. SpuneU. 1975. Effect of
calcium and phosphorus levels on growth, reproduction and bone devel-
opment of ponies. J. Anim. Sci. 40:78-85.
Kamphues, J., E. Muller, and W. Drochner. 1989. Clinical effects of an
extreme Ca overdose in feed for growing piglets. J. Can. Dent. Assoc.
55:129-133.
Kaushik, S. J. 1995. Nutrients requirements, supply and utilization in the
context of carp culture. Aquaculture 129:225—241.
Kincaid, R. L. 1979. Biological availability of zinc from inorganic sources
with excess dietary calcium. J. Dairy Sci. 62:1081—1085.
Krook L., L. Lutwak, and K. McEntee. 1969. Dietary calcium,
ultimobranchial tumors and osteopetrosis in the bull. Syndrome of cal-
citonin excess? Am. J. Clin. Nutr. 22:115-118.
Laflamme, D. 2000. Effect of breed size on calcium requirements for pup-
pies. Comp. Contin. Educ. Pract. Vet. 23(Suppl. 9A):66-69.
Lauten, S. D., N. R. Cox, W. R. Brawner, Jr., S. A. Goodman, J. T.
Hathcock, R. D. Montgomery, S. A. Kincaid, N. E. Morrison, J. S.
Spano, A. J. Lepine, G. A. Reinhart, andH. J. Baker. 2002. Influence of
dietary calcium and phosphorus content in a fixed ratio on growth and
development in Great Danes. Am. J. Vet. Res. 63:1036-1047.
Lei, X. G., P. K. Ku, E. R. Miller, M. T. Yokoyama, and D. E. Ullrey. 1994.
Calcium level affects the efficacy of supplemental microbial phytase in
corn-soybean meal diets of weanling pigs. J. Anim. Sci. 72:139-143.
Littledike, E. T., D. Glazier, and H. M. Cook. 1976. Electrocardiographic
changes after induced hypercalcemia and hypocalcemia in cattle:
reversal of the induced arrhythmia with atropine. Am. J. Vet. Res.
137:383-388.
Lovell, R. T. 1991. Nutrition of aquaculture species. J. Anim. Sci. 69:4193—
4200.
Lovell, R. T., and Y. P. Li. 1978. Essentiality of vitamin D in diets of
channel catfish (Ictalurus punctatus). Trans. Am. Fish Soc.
107:809-811.
Maenpaa, P. H., T. Koskinen, and E. Koskinen. 1988. Serum profiles of
vitamins A, E and D in mares and foals during different seasons. J.
Anim. Sci. 66:1418-1423.
Martz, F. A., A. T. Belo, M. F. Weiss, R. L. Belyea, and J. P. Goff. 1990.
True absorption of calcium and phosphorus from alfalfa and corn silage
when fed to lactating cows. J. Dairy Sci. 73:1288-1295.
McCay, C. M., A. V. Tunison, M. Crowell, and H. Paul. 1936. The calcium
and phosphorus content of the body of the brook trout in relation to age,
growth, and food. J. Biol. Chem. 1 14:259-263.
Miller, W. 1983. Using mineral requirement standards in cattle feeding pro-
grams and feed formulations. Ga. Nutr. Conf. Feed Ind. Athens: Uni-
versity of Georgia.
Morgan, D. P., E. P. Young, I. P. Earle, R. J. Davey, and J. W. Stevenson.
1969. Effects of dietary calcium and zinc on calcium, phosphorus, and
zinc retention in swine. J. Anim. Sci. 29:900-905.
Nap, R. C, H. A. Hazewinkel, and W. E. van den Brom. 1993. 45Ca kinet-
ics in growing miniature poodles challenged by four different dietary
levels of calcium. J. Nutr. 123:1826-1833.
Nellans, H. N. 1988. Contributions of cellular and paracellular pathways to
transepithelial intestinal calcium transport. P. 269 in Cellular Calcium
and Phosphate Transport in Health and Disease, F. Bronner and M.
Peterlik, eds. New York: Alan R. Liss.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
NRC. 1994. Nutrient Requirements of Poultry: Ninth Revised Edition.
Washington, D.C.: National Academy Press.
NRC. 2006. Nutrient Requirements of Dogs and Cats. Washington, D.C.:
The National Academies Press.
Ogura, Y. 1981. Leg abnormality associated with dietary excessive calcium
carbonate in broiler chicks. Natl. Inst. Anim. Health Q. (Tokyo)
21(3):14I-147.
Pastoor, F. J., R. Opitz, A. T. Van 'T Klooster, and A. C. Beynen. 1994.
Dietary calcium chloride vs. calcium carbonate reduces urinary pH and
phosphorus concentration, improves bone mineralization and depresses
kidney calcium level in cats. J. Nutr. 124:2212-2222.
Pehrson, B., C. Svensson, and M. Jonsson. 1998. A comparative study of
the effectiveness of calcium propionate and calcium chloride for the
prevention of parturient paresis in dairy cows. J. Dairy Sci. 81:2011-
2016.
Phillippo, M., G. W. Reid, and I. M. Nevison. 1994. Parturient hypocalcae-
mia in dairy cows: effects of dietary acidity on plasma minerals and
calciotrophic hormones. Res. Vet. Sci. 56:303—309.
Puis, R. 1994. Mineral Levels in Animal Health: Diagnostic Data, Second
Edition. Clearbrook, B.C., Canada: Sherpa International.
Reinhart, G. A., and D. C. Mahan. 1986. Effect of vai'ious calcium:phosphorus
ratios at low and high dietary phosphorus for starter, grower, and finisher
swine. J. Anim. Sci. 63:457^66.
Robinson, E. H., S. D. Rawles, P. B. Brown, H. E. Yette, and L. W. Greene.
1986. Dietary calcium requirement of channel catfish Ictalurus
punctatus, reared in calcium-free water. Aquaculture 53:263-270.
Ross, R.D., G.L. Cromwell, and T.S. Stahly. 1984. Effects of source and
particle size on the biological availability of calcium in calcium supple-
ments for growing pigs. J. Anim. Sci. 59:125-134.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
108
MINERAL TOLERANCE OF ANIMALS
Sandberg, A. S., T. Larsen, and B. Sandstrom. 1993. High dietary calcium
level decreases colonic phytate degradation in pigs fed a rapeseed diet.
J. Nutr. 123:559-566.
Schoenmakers, 1., H. A. Hazewinkel, G. Voorhout, C. S. Carlson, and D.
Richardson. 2000. Effects of diets with different calcium and phospho-
rus contents on the skeletal development and blood chemistry of grow-
ing Great Danes. Vet. Rec. 147:652-660.
Schryver, H. F., H. F. Hintz, and J. E. Lowe. 1974. Calcium and phosphorus
in the nutrition of the horse. Cornell Vet. 64:493-515.
Shackelford, M. E., T. F. Collins, T. N. Black, M. J. Ames, S. Dolan, N. S.
Sheikh, R. K. Chi, and M. W. O'Donnell. 1994. Mineral interactions in
rats fed A1N-76A diets with excess calcium. Food Chem. Toxicol.
32(3):255-263.
Shane, S. M., R. J. Young, and L. Krook. 1969. Renal and parathyroid
changes produced by high calcium intake in growing pullets. Avian Dis.
13:558-567.
Smith, H., and J. H. Taylor. 1961. Effect of feeding two levels of dietary
calcium on the growth of broiler chicks. Nature 190:1200.
Urbanyi, L. 1960. Chicken feeding trials with diets containing sufficient
phosphorus and increasing amounts of calcium carbonate. Nutr. Abstr.
30:691-696.
Wasserman, R. H. 1981. Intestinal absorption of calcium and phosphorus.
Fed. Proc. 40:68-72.
Weber, M., L. Martin, H. Dumon, V. Biourge, and P. Nguyen. 2000. Growth
and skeletal development in two large breed dogs fed 2 calcium levels.
J. Vet. Intern. Med. 14:388 (Abstr.).
Wentink, G. H., and T. S. van den Ingh. 1992. Oral administration of cal-
cium chloride-containing products: testing for deleterious side effects.
Vet. Q. 14(2):76-79.
Wheeler, W. E., and C. H. Noller. 1976. Limestone buffers in complete
mixed rations for dairy cattle. J. Dairy Sci. 59:1788-1793.
Wise, A. 1983. Dietary factors determining the biological activities of
phytase. Nutr. Abstr. Rev. 53:791-806.
Yarrington, J. T., C. C. Capen, H. E. Black, and R. Re. 1977. Effects of a
low-calcium prepartal diet on calcium homeostatic mechanisms in the
cow: morphologic and biochemical studies. J. Nutr. 107:2244—2256.
Xu, C, T. Wensing, S. Kocsis, and A. C. Beynen. 1999. High calcium
intake lowers apparent digestibility of energy in veal calves. Arch.
Tierernahr. 52:67-73.
Zimmerman, D. R., V. C. Speer, V. W. Hays, and D. V. Catron. 1963.
Effect of calcium and phosphorus levels on baby pig performance. J.
Anim. Sci. 22:658-663.
Zinn, R. A., and Y. Shen. 1996. Interaction of dietary calcium and supple-
mental fat on digestive function and growth performance in feedlot
steers. J. Anim. Sci. 74:2303-2309.
Copyright © National Academy of Sciences. All rights reserved.
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114
MINERAL TOLERANCE OF ANIMALS
TABLE 10-2 Calcium Concentrations in Fluids and Tissues of Animals (mg/kg or mg/L)"
Fisti
Animal
Serum
Muscle
(wet wt basis)
Liver*
(wet wt basis)
Kidney*
(wet wt basis)
BonegCa/lOOg
(fat free, dry wt basis)
Milk (g/L) or Egg
(g Ca/eggshell)
Ctiicken,
broiler
90-130
75-80
170-600
14-20
Laying hen
200-400
18-22
2.0-2.1
Pig ^^B
90-120
^^^^^B
34-63 ^^H
60-125
^^^1
to^^^^l
Cow
90-100
30-300
30-200
45-200
24.5-26.0
1.2
Sheep
90-110
55-96
40-80
60-140
1.8-2.0
80-100 With bone
1,900^,100
Without bone
<1,000
Whole fish meaF
40-50 g/kg dry wt
NOTE: Dietary calcium excess does not increase the calcium content of animal tissues significantly, unless accompanied by vitamin D intoxication.
"Data largely adapted from Puis, 1994.
''Vitamin D intoxication can cause metastatic calcification of soft tissues increasing calcium content of these tissues several-fold above normal upper limits.
"^Menhaden or anchovy fish meal fed to livestock.
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11
Chromium
INTRODUCTION
Chromium (Cr) is a metallic element that occurs in each
of the oxidation states from -2 to +6. Only the 0, +2, +3,
and +6 valence states are commonly found. Elemental chro-
mium (0) does not occur naturally. Chromium (+2) is un-
stable and is readily oxidized to trivalent chromium (+3).
Chromium occurs naturally primarily in the trivalent form,
largely as ferrochromite (FeCrjO^) ores. Trivalent chro-
mium (h-3) forms stable complexes with both organic and
inorganic ligands. Hexavalent chromium (-1-6) has strong
oxidizing properties and is produced almost entirely by in-
dustrial processes (WHO, 1988). Chromium (+6) is spon-
taneously reduced to chromium (H-3), when present in a
soluble form.
The principal component of chromium ores is chromite, a
black mineral consisting largely of iron and chromium (H-3)
oxides, with lesser amounts of magnesium and aluminum
oxides (Katz and Salem, 1994). Chromium has not been
mined in the United States since 1961. Most of the chro-
mium ores processed in the United States are imported from
South America, Turkey, and Russia (ATSDR, 2000).
Approximately 60 percent of the chromium processed is
used in the production of stainless steel and other alloys.
Ferrochromite used in the production of stainless steel and
other alloys is prepared by the reduction of chromite with car-
bon (Katz and Salem, 1994). Chromium (+3) is used in the
refractory industry as a component in chrome and chrome-
magnesite, magnesite-chrome bricks, and granular chrome-
bearing and granular chromite, which are used as linings for
high-temperature industrial furnaces (ATSDR, 2000). Both
trivalent and hexavalent chromium are produced in the chemi-
cal industry and used for chrome plating, leather tanning, and
manufacturing of pigments and wood preservatives.
ESSENTIALITY
Early studies by Schwartz and Mertz (1959) showed that
chromium was a component of a glucose tolerance factor
that corrected impaired glucose metabolism in rats fed cer-
tain diets. Later studies demonstrated that chromium poten-
tiates insulin function (Offenbacher et al., 1997). Clinical
signs of chromium deficiency, including glucose intolerance,
weight loss, and nerve and brain disorders, have been ob-
served in humans receiving long-term parenteral nutrition
(Anderson, 1995). Addition of small amounts of chromium
(+3) chloride (CrClj) to the total parenteral nutrition solu-
tion corrected deficiency signs in all patients. Recent studies
suggest that chromium affects insulin by binding to a low-
molecular weight oligopeptide named chromodulin
(Vincent, 2001). Chromodulin tightly binds four chromic
ions and amplifies insulin receptor tyrosine kinase activity;
thus, it enhances insulin action. Without chromium,
apochromodulin is largely ineffective in stimulating insulin-
dependent tyrosine kinase activity. Activation of
apochromodulin is specific for chromium.
Until recently, practical diets fed to domestic animals
were assumed to provide sufficient chromium to meet ani-
mal requirements. Although responses to chromium supple-
mentation have been variable, a number of studies in the past
10 years have indicated that supplementation of diets with
organic forms of chromium may affect animal metabolism
and production criteria as well as the composition of animal
products produced. Addition of chromium picolinate to diets
of calves (Bunting et al., 1994) and growing pigs (Amoikon
et al., 1995) increased glucose clearance rate following in-
travenous glucose administration. In swine, chromium
picolinate has increased carcass lean and decreased carcass
fat in growing-finishing pigs (Page et al., 1993) and in-
creased litter size in sows (Lindemann et al., 1995;
Lindemann, 1999). Chromium supplementation to poultry
diets has improved growth rate in broilers (Lien et al., 1999)
and reduced serum and egg yolk cholesterol in hens (Lien et
al., 1996). A number of studies in cattle indicate that chro-
mium supplementation from various sources may increase
immune response and reduce incidence of disease, especially
in stressed animals (Spears, 2000). Addition of chromium
115
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MINERAL TOLERANCE OF ANIMALS
methionine to lactating dairy cow diets increased milk pro-
duction and feed intalce (Hayirli et al., 2001).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Contamination of biological samples with chromium dur-
ing collection, storage, and preparation of samples for analy-
sis can present a major source of error. Prior to 1978, re-
searchers were unaware that chromium concentrations they
measured in tissues, blood, urine, and foods far exceeded
true concentrations, because of background and environmen-
tal contamination (Guthrie et al., 1978). Chromium is gener-
ally present in tissues, plasma, and urine in the ng/g or ng/L
range. Therefore, it is essential to minimize contamination
from dust and stainless steel material (scalpels, knives, trays,
needles, and grinding and homogenizing equipment) used in
collection and preparation of samples. Stainless steel instru-
ments should be replaced with titanium, glass, quartz, or
polyethylene instruments (Katz and Salem, 1994). Needles
made from nickel or platinum should be used for collection
of blood samples for chromium analysis. Reagents of the
highest purity also must be used to avoid contamination.
Reagent blanks should be carried through sample prepara-
tion and analysis to correct for background contamination.
Losses of chromium through volatilization may occur dur-
ing heating or acid digestion of samples in open systems
(WHO, 1988). A reference material (obtained from the Na-
tional Institute of Standards and Technology) with a certi-
fied value for chromium is necessary to validate analytical
procedures.
Low concentrations of chromium in biological samples
can be measured using graphite furnace atomic absorption
spectrometry, neutron activation analysis, or mass spectrom-
etry. Graphite furnace atomic absorption spectrometry is the
most commonly used method, and has a detection limit of
0.005 |Jg/L when an appropriate background correction
method is used. Flame atomic absorption spectrometry and
inductively-coupled plasma atomic emission spectrometry
are not sensitive enough to detect chromium concentrations
typically found in biological samples, but can be used to
determine potentially toxic concentrations of chromium in
feedstuffs.
REGULATION AND METABOLISM
Absorption and Metabolism
Metabolism of chromium is greatly affected by valance
state. Hexavalent chromium is absorbed to a greater extent
than the trivalent form (Donaldson and Barreras, 1966;
Kerger et al., 1996) and readily enters cells through nonspe-
cific anion carriers. In contrast, chromium (+3) is poorly
absorbed and enters cells with very low efficiency. Insignifi-
cant amounts of hexavalent chromium are likely to be con-
sumed orally because chromium (-1-6) is reduced in the envi-
ronment to chromium (-1-3), the more stable oxidation state.
Furthermore, chromium (+6) consumed is totally or at least
partly reduced to chromium (+3) in the acid environment of
the stomach (Donaldson and Barreras, 1966). Hexavalent
chromium also does not generally occur naturally and is pro-
duced almost totally from human activities.
Absorption of chromium by humans consuming self-se-
lected diets ranged from 0.5 to 2.0 percent, with higher ab-
sorption values observed in individuals consuming a low
chromium intake (Anderson and Kozlovsky, 1985). Esti-
mated absorption of chromium from soluble sources, such as
CrClj and chromium acetate, in humans and rats has ranged
from 0.4 to approximately 2.0 percent (Donaldson and
Barreras, 1966; Juturu et al., 2003). Absorption of chromium
from chromium (H-3) oxide was negligible in rats (Juturu et
al., 2003). It is this property that allows use of chromic oxide
as a nondigestible marker for digestibility studies. Gargus et
al. (1994) reported a mean absorption of 2.8 percent in hu-
mans administered 400 [ig Cr/day as chromium picolinate.
Chromium is transported in the blood primarily bound to
transferrin (Offenbacher et al., 1997). Plasma or serum chro-
mium concentrations in humans are generally less than
0.30 |Jg/L. Blood chromium concentrations are not in equi-
librium with tissue chromium concentrations and do not
reflect body stores. Tissue chromium concentrations are low
(generally less than 100 ng/g DM) with kidney, liver, spleen,
and bone containing the highest concentration.
The active form of chromium that potentiates insulin
function remains unclear. Early studies suggested that chro-
mium was a component of a glucose tolerance factor (Mertz,
1993). Glucose tolerance factor isolated from brewer's yeast
contained chromium (H-3), nicotinate, glycine, cysteine, and
glutamate (Toepfer et al., 1976). More recent research sug-
gests that chromodulin is the active form of chromium
involved in facilitating insulin action (Vincent, 2001).
Chromodulin is an oligopeptide comprised primarily of gly-
cine, cysteine, aspartate, and glutamate, and has been iso-
lated from the liver or kidney of a number of animal species
(Vincent, 2001). In response to insulin release, chromium
from the blood is transported to insulin-sensitive cells where
chromium binds to apochromodulin. When insulin concen-
trations decrease, chromodulin is believed to be released
from cells and excreted in the urine. Urine is the major route
of excretion for absorbed chromium. Consumption of high
carbohydrate diets that increase blood insulin concentrations
increases urinary excretion of chromium (Offenbacher et al.,
1997).
IVIetabolic Interactions and IVIechanisms of Toxicity
Studies have indicated that chromium (+3) absorption is
increased by ascorbic acid, amino acids, and oxalate
(Offenbacher et al., 1997). Zinc may reduce chromium ab-
sorption; however, increasing dietary zinc did not reduce
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CHROMIUM
117
toxicosis of chiromium (+3) in chicks (Ciiung et al., 1983).
Iron overload in humans increases saturation of transferrin
with iron and may impair chromium transport (Offenbacher
et al., 1997). High dietary concentrations of chromium (+3)
alleviate signs of vanadium toxicosis in chicks (Hill and
Matrone, 1970).
Trivalent chromium has a low order of toxicity, because
of low intestinal absorption and limited entry into cells.
Hexavalent chromium is several-fold more toxic than triva-
lent chromium (WHO, 1988; Dayan and Paine, 2001).
Hexavalent chromium not reduced to chromium (H-3) in the
gastrointestinal tract or blood can cross cell membranes
where it is ultimately reduced to chromium (H-3) by reducing
agents such as glutathione, cysteine, and ascorbic acid. The
mechanism of chromium toxicosis is believed to be due to
chromium (+3) and/or chromium (+5) and chromium (+4),
intermediates in the reduction of hexavalent to trivalent chro-
mium, binding to intracellular macromolecules, including
DNA (ATSDR, 2000). Toxicity of chromium also may be
related to chromium (+3, +4, or +5) induced free radical for-
mation (Bagchi et al., 2002).
SOURCES AND BIOAVAILABILITY
Chromium occurs naturally in the Earth's crust and also
is released into the environment from combustion processes
and ore processing industries. Naturally occurring chromium
is almost always in the trivalent state, while chromium (+6)
is almost entirely derived from human activities (WHO,
1988). Concentrations of chromium in the ambient air in the
United States range from 0.005 to 0.525 |ig/m-\ In U.S. river
and ocean waters, chromium concentrations average 10.0
and 0.3 |ig/L, respectively (ATSDR, 2000). Soil chromium
varies greatly with a mean concentration of 37.0 mg/kg
(USGS, 1984). Chromium is present in soils primarily in
carbonate and oxide forms that are not mobile in soil. Ex-
tractable chromium, measured following extraction of soil
with acids or chelating agents, provides a much better esti-
mate of chromium available for plant uptake than total soil
chromium.
Chromium analysis of animal feedstuffs has received little
attention. However, most human food sources are low (<0. 10
mg/g DM) in chromium. Feed phosphate sources appear to
be a major source of chromium in certain animal diets. Feed
grade monocalcium phosphate and defluorinated phosphate
sources vary in chromium content but average 83 and 110
mg Cr/kg, respectively (Sullivan et al., 1994). At present,
chromium picolinate, chromium propionate, and chromium
methionine can be supplemented to swine diets, at levels
from 0.2 to 0.4 mg Cr/kg diet, in the United States. Chro-
mium supplementation is currently not permitted in other
animal species.
When given orally, hexavalent chromium has a much
greater bioavailability than even water-soluble forms of in-
organic chromium (H-3). However, as discussed earlier, chro-
mium (+6) is not likely to be consumed orally. Chromium
(+3) oxide is essentially unavailable when given to rats, com-
pared to the more soluble CrClj and chromium (+3) acetate
(Juturu et al., 2003). Certain organic forms of chromium (+3)
appear to be more bioavailable than inorganic trivalent
forms. Rats supplemented with 5 mg Cr/kg from chromium
picolinate or a chromium dinicotinic acid-diglycine-cysteine-
glutamic acid complex had higher chromium concentrations
in kidney and liver than those receiving CrClj after three
weeks (Anderson et al., 1996). When supplemented at 20 to
100 mg Cr/kg for 20 weeks, rats fed chromium picolinate
also had much higher liver and kidney chromium concentra-
tions than rats fed CrClj (Anderson et al., 1997a). In contrast
to these findings, absorption of ^'Cr from CrClj and chro-
mium picolinate has been similar in short-term studies with
rats (Ohn et al., 1994; Anderson et al., 1996).
TOXICOSIS
Chromium toxicity has been extensively reviewed (WHO,
1988; Katz and Salem, 1994; EPA, 1998; Dayan and Paine,
2001). Toxicosis of chromium is a major concern in humans
exposed in occupational and industrial settings to chromium
via inhalation and dermal contact. The major form of chro-
mium believed to be responsible for toxicosis in humans is
chromium (+6). Hexavalent chromium can act as a carcino-
gen, an allergen, and an acute irritant in humans and experi-
mental animals (Dayan and Paine, 2001). Chromates (+6)
are used in oil fields as a corrosion inhibitor and in drilling
muds. Toxicosis from chromates (+6) has been suspected in
cattle exposed to oil field wastes (Kerr and Edwards, 1981).
However, chromium (+6) is generally not consumed orally
for reasons described earlier. This discussion will focus on
chromium (+3). Trivalent chromium is relatively nontoxic
via oral intake.
Single Dose and Acute
Large doses of chromium (+3) are required to produce
signs of acute toxicosis. A single oral dose of 650 mg Cr/kg
BW produced no overt toxicosis in young rats (NRC, 1980).
The LDjQ in rats for chromium (+3) as CrCl3-6H20,
Cr(N03)3-9H20, and Cr(CH3COO)3-H20 is approximately
365, 422, and 2,376 mg Cr/kg BW, respectively (Katz and
Salem, 1994). Female rats are slightly more sensitive to acute
doses of chromium than males (ATSDR, 2000). Signs of
acute toxicosis in rats include hypoactivity, mydriasis, lacri-
mation, and diarrhea. Exposing carp to water containing
20 mg Cr/L as CrCl3 for 48 hours resulted in 100 percent
mortality (Table 1 1-1); however, 10 mg/L had no effect on
mortality (Muramoto, 1981). Chromium sulfate caused
lower mortality in carp than CrCl3 when supplied at 20 mg
Cr/L. The LCjq for chromium in prawn larvae was estimated
at 12.5 mg/L for CrCl3 (Marino-Balsa et al., 2000).
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118
MINERAL TOLERANCE OF ANIMALS
Chronic
A number of studies evaluating oral ingestion of high
concentrations of chromium (+3) are summarized in Table
11-1. Body weight gain in young chicks was reduced by ad-
dition of 1,500 mg Cr/kg diet as Cr2(S04)3 (Chung et al.,
1983) or 2,000 mg/kg diet as CrClj (Hill and Matrone, 1970).
In laying hens, 50 mg Cr/kg diet from either CrClj, chro-
mium yeast, or a chromium aminoniacinate complex did not
affect egg production, but reduced activity of liver cyto-
chrome P-450 dependent monooxygenases (Guerra et al.,
2002). They suggested that 50 mg Cr/kg may impair cyto-
chrome P-450 catalyzed drug metabolism. Considering the
life expectancy of laying hens, the biological significance of
this finding is unclear.
Providing chromium (CrClj) in drinking water at 328 mg/L
in rats (Bataineh et al., 1997) or 656 mg/L in mice (Elbetieha
and Al-Hamood, 1997) for 12 weeks reduced body weight
gain. In male mice, CrClj at 1,640 mg Cr/L of water reduced
fertility, and 656 mg/L reduced implantation and viable
fetuses in pregnant females (Elbetieha and Al-Hamood,
1997). Mice born and raised to mice exposed to 328 mg Cr
(CrCl3)/L of water during gestation and lactation (20 d) had
reduced body weight at 60 days of age (Al-Hamood et al.,
1998). Fertility was impaired in female but not male mice
exposed prenatally and postnatally to chromium (Al-
Hamood et al., 1998). Reduced sexual behavior (measured
by number of mounts and number of males ejaculating) was
observed in male rats given 328 mg Cr/L of water for 12
weeks, but fertility was not affected (Bataineh et al., 1997).
Limited research has evaluated chronic toxicity of organic
forms of chromium. Rats supplemented for 20 weeks with
100 mg Cr/kg diet from chromium picolinate had chromium
concentrations in liver and kidney that were approximately
7-fold higher than observed in rats fed a similar concentra-
tion of CrClj (Anderson et al., 1997a). However, no signs of
toxicosis, including pathological changes in liver or kidney,
were seen in rats fed either chromium source. Chromium
(-1-3) oxide is very insoluble and did not produce toxicosis
even when provided in the diet of rats at up to 34,215 mg Cr/kg
for 2 years (Ivankovic and Preussmann, 1975).
Factors Influencing Toxicity
Soluble forms of chromium (+6) are several-fold more
toxic than soluble forms of chromium (H-3). Animals are not
usually exposed to chromium (H-6) orally for reasons dis-
cussed previously. Toxicity of chromium (H-3) is affected by
solubility of the compound. Insoluble CrjOj has not pro-
duced toxicosis in animals (Ivankovic and Preussmann,
1975; NRC, 1980) while soluble forms such as CrCl, and
Cr2(S04)3 can reduce body weight gain and impair repro-
duction when provided in feed or water at high concentra-
tions (Table 11-1). Organic forms of chromium may be more
toxic than CrClj. Chromium picolinate feeding resulted in
higher tissue chromium concentrations than CrClj (Ander-
son et al., 1997a). However, elevated tissue chromium con-
centrations in rats supplemented with chromium picolinate
has not caused toxicosis.
TISSUE LEVELS
Chromium is widely distributed in the body at very low
(ng/g DM) concentrations. Representative values in tissues
from various animals are shown in Table 11-2. Addition of
100 mg Cr/kg as CrClj to turkey diets for 5 weeks greatly
increased tissue chromium concentrations; however, even at
the high level of supplementation, tissue chromium only ex-
ceeded 1 mg/kg DM in kidney (Anderson et al., 1989). In
growing pigs, supplementation with 0.2 to 0.3 mg Cr/kg as
chromium picolinate increased chromium concentrations in
liver, kidney, and heart, but not in muscle (Ward, 1995;
Anderson et al., 1997b). Liver and kidney chromium con-
centrations were much higher in rats fed chromium
picolinate than in those fed CrCl, at high concentrations
(Anderson etal., 1997a). Supplementation of cattle diets with
low concentrations of chromium did not increase tissue chro-
mium (Spears et al., 2004). Tissue chromium data are not
available for animals fed toxic concentrations of chromium.
It is unlikely that chromium accumulation in animal prod-
ucts, other than possibly kidney, would cause a toxicological
concern for humans.
MAXIMUM TOLERABLE LEVELS
The maximum tolerable level for chromium is defined as
the dietary level that, when fed for a defined period of time,
will not impair animal health and/or performance. Valance
state and chemical form of chromium affect the maximum
tolerable level for chromium. Hexavalent chromium (-1-6) is
much more toxic than trivalent chromium (H-3). Maximum
tolerable levels for chromium (+6) have not been defined for
most domestic animals because chromium (+6) is generally
not ingested orally.
Chromic oxide, an insoluble form of chromium (+3) is
very poorly absorbed, and has been widely used as an indi-
gestible marker in animals for periods of several weeks at
concentrations as high as 3,000 mg Cr/kg diet with no
evidence of adverse effects (NRC, 1980 ). Feeding diets con-
taining over 30,000 mg Cr/kg from CrjOj for two years also
did not produce adverse effects in rats (Ivankovic and
Preussmann, 1975).
Soluble forms of chromium (+3), such as CrClj and
Cr,(S04)3, reduce body weight gain in young chicks when
fed at 1,500 to 2,000 mg Cr/kg diet. Young chicks can toler-
ate 500 mg Cr (from soluble forms)/kg diet for 21 to 35 days
without adverse effects (Hill and Matrone, 1970; Chung et
al., 1983). Exposure of rats and mice to 328 to 656 mg Cr/L
in drinking water for 12 weeks reduced body weight and
impaired reproduction (Elbetieha and Al-Hamood, 1997; Al-
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CHROMIUM
119
Hamood et al., 1998). Developmental effects were also ob-
served in mice exposed prenatally and postnatally to 328 mg
Cr/L of water (Al-Hamood et al., 1998). Dietary supplemen-
tation of rats for 20 weeks with 100 mg Cr/kg from either
CrClj or chromium picolinate did not produce toxicosis, but
increased liver and kidney chromium concentrations
(Anderson et al., 1997a). Based on available literature, the
maximum tolerable level for chromium (H-3) was set at 3,000
mg/kg for Cr^Oj. For more soluble forms of chromium (H-3)
the maximum tolerable level was set at 500 mg/kg for poultry
and 100 mg/kg for mammalian species. Limited data in fish
suggest that soluble forms of chromium (-H3) can be toler-
ated for 48 to 72 hours at 8.0 to 10.0 mg/L of water. In animal
species other than poultry and fish, rat and mice data were
used to establish maximum tolerable levels. At dietary con-
centrations of chromium up to the maximum tolerable levels
indicated, any increase in chromium concentration in edible
tissue, with the possible exception of kidney, should not
present a human health concern.
FUTURE RESEARCH NEEDS
Studies are needed to define the maximum tolerable level
of chromium for most domestic animals. Research is par-
ticularly needed to determine the concentration of chromium
from various organic chromium supplements that can be tol-
erated without adverse effects.
SUMMARY
Chromium occurs in a number of oxidation states, with
chromium (H-3) being the most stable form. Trivalent chro-
mium potentiates insulin activity and is generally recognized
as an essential trace mineral. Chromium is found naturally
almost entirely as chromium (+3), but both trivalent and
hexavalent chromium are produced and used in the chemical
industry. Hexavalent chromium is much more toxic than
chromium (+3). However, chromium (+6) released into the
environment is largely reduced to chromium (+3). Almost
all of the chromium consumed orally is in the trivalent form.
Chromium (+3) is relatively nontoxic due to its poor intesti-
nal absorption and limited entry of absorbed chromium (+3)
into cells. Chromium oxide even at dietary concentrations
over 30,000 mg Cr/kg diet did not produce toxicosis in rats.
The level of chromium (+3) in soluble forms, such as CrClj,
needed to cause adverse effects in animals is above 100 mg/kg.
Fish can tolerate at least 8 mg Cr/L of water for 48 to 72 hours
without adverse effects. The amount of soluble chromium
(+3) needed to produce adverse effects is at least 100 times
the amount needed to meet animal requirements.
REFERENCES
ATSDR (Agency for Toxic Substances and Disease Registry). 2000. Toxi-
cological profile for cliromium. Atlanta, GA: Agency for Toxic Sub-
stances and Disease Registry, U.S. Department of Health and Human
Services, Public Health Service. Available at http://www.atsdr.cdc.gov/
toxprofiles/tpV.html.
Al-Hamood, M. H., A. Elbetieha, and H. Bataineh. 1998. Sexual maturation
and fertility of male and female mice exposed prenatally and postnatally
to trivalent and hexavalent chromium compounds. Reprod. Fertil. Dev.
10:179-183.
Amoikon, E. K., J. M. Fernandez, L. L. Southern, D. L. Thompson, T. L.
Ward, and B. M. Olcott. 1995. Effect of chromium tripicolinate on
growth, glucose tolerance, insulin sensitivity, plasma metabolites, and
growth hormone in pigs. J. Anim. Sci. 73:1 123— 1 130.
Anderson, R. A. 1995. Chromium and parenteral nutrition. Nutrition
11:83-86.
Anderson, R. A., and A. S. Kozlovsky. 1985. Chromium intake, absorption
and excretion of subjects consuming self-selected diets. Am. J. Clin.
Nutr. 41:1177-1183.
Anderson, R. A., N. A. Bryden, M. M. Polansky, and M. P. Richards. 1989.
Chi'omium supplementation of turkeys: effects on tissue chromium. J.
Agric. Food Chem. 37:131-134.
Anderson, R. A., N. A. Bryden, M. M. Polansky, and K. Gautschi. 1996.
Dietary chromium effects on tissue chromium concentrations and chro-
mium absorption in rats. J. Trace Elem. Exp. Med. 9:11—25.
Anderson, R. A., N. A. Bryden, andM. M. Polansky. 1997a. Lack of toxic-
ity of chromium chloride and chromium picolinate in rats. J. Am. Coll.
Nutr. 16:273-279.
Anderson, R. A., N. A. Bryden, C. M. Evock-Clover, and N. C. Steele.
1997b. Beneficial effects of chromium on glucose and lipid variables in
control and somatotropin-treated pigs are associated with increased tis-
sue chromium and altered tissue copper, iron and zinc. J. Anim. Sci.
75:657-661.
Bagchi, D., S. J. Stohs, B. W. Downs, M. Bagchi, and H. G. Preuss. 2002.
Cytotoxicity and oxidative mechanisms of different forms of chromium.
Toxicol. 180:5-22.
Bataineh, H., M. H. Al-Hamood, A. Elbetieha, and I. B. Hani. 1997. Effect
of long-term ingestion of chromium compounds on aggression, sex
behavior and fertility in adult male rate. Drug Chem. Toxicol.
20:133-149.
Bunting, L. D., J. M. Fernandez, D. L. Thompson, and L. L. Southern.
1 994. Influence of chromium picolinate on glucose usage and metabolic
criteria in growing Holstein calves. J. Anim. Sci. 72:1591—1599.
Chung, K. H., M. H. Kang, C. S. Kim, I. K. Han, and K. N. Lee. 1983. The
toxicity of trivalent chromium and its interaction with cobalt and zinc in
the chick. Korean J. Anim. Sci. 25:686-691.
Cohn, L. A., J. R. Dodam, D. L. McCaw, and D. J. Tate. 1999. Effects of
chromium supplementation on glucose tolerance in obese and nonobese
cats. Am. J. Vet. Res. 60:1360-1363.
Dayan, A. D., and A. J. Paine. 2001. Mechanisms of chromium toxicity,
carcinogenicity and allergenicity: review of the literature from 1985 to
2000. Human Exp. Toxicol. 20:439^51.
Donaldson, R. M., Jr., and R. F. Barreras. 1966. Intestinal absorption of
trace quantities of chromium. J. Lab. Clin. Med. 68:484-493.
Elbetieha, A., and M. H. Al-Hamood. 1997. Long-term exposure of male
and female mice to trivalent and hexavalent chromium compounds:
effect on fertility. Toxicology 1 16:39^7.
EPA (U.S. Environmental Protection Agency). 1998. Toxicological review
of trivalent chromium. Washington, D.C.: U.S. Environmental Protec-
tion Agency. Available at http://www.epa.gov/IRIS/toxreviews/
0028-tr.pdf. Accessed on March 22, 2005.
Gargas, M. L., R. L. Norton, D. J. Paustenbach, and B. L. Finley. 1994.
Urinary excretion of chromium by humans following ingestion of chi'o-
mium picolinate. Drug Metab. Dispos. 22:522-529.
Copyright © National Academy of Sciences. All rights reserved.
&
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ttp7/www nap edi]/ratalng/1 1 rina htmll
120
MINERAL TOLERANCE OF ANIMALS
Guerra, M. C, C. Renzulli, A. L. Pozzetti, M. Paolini, and E. Speroni. 2002.
Effects of trivalent cliromium on tiepatic CYP-linlced monooxygenases
in laying hens. J. Appl. Toxicol. 22:161-165.
Guthi-ie, B. E., W. R. Wolf, and C. Veillon. 1978. Background con-ection
and related problems in the determination of chromium in urine by
graphite furnace atomic absorption spectrometry. Anal. Chem. 50: 1900-
1902.
Hayirli, A., D. R. Bremmer, S. J. Bertics, M. T. Socha, and R. R. Grummer.
2001. Effect of chromium supplementation on production and meta-
bolic parameters in periparturient dairy cows. J. Dairy Sci. 84:1218-
1230.
Hill, C. H., and G. Matrone. 1970. Chemical parameters in the study of in
vivo and in vitro interactions of transition elements. Fed. Proc. 29: 1474—
1481.
Ivankovic, S., and R. Preussmann. 1975. Absence of toxic and carcinogenic
effects after administration of high doses of chromic oxide pigment in
subacute and long-term feeding experiments in rats. Food Cosmet.
Toxicol. 13:347-351.
Juturu, v., J. R. Komorowski, J. P. Devine, and A. Capen. 2003. Absorption
and excretion of chromium from orally administered chromium chlo-
ride, chromium acetate and chromium oxide in rats. Trace Elem.
Electroly. 20:23-28.
Katz, S. A., and H. Salem. 1994. The Biological and Environmental Chem-
istry of Chromium. New York: VCH Publishers.
Kerger, B. D., D. J. Paustenbach, G. E. Corbett, and B. L. Finely. 1996.
Absorption and elimination of trivalent and hexavalent chromium in
humans following ingestion of a bolus dose in drinking water. Toxicol.
Appl. Pharmacol. 141:145-158.
Kerr, L. A., and W. C. Edwards. 1981. Chromate poisoning in livestock
from oil field wastes. Vet. Hum. Toxicol. 23:401^02.
Lien, T., S. Chen, S. Shiaw, D. P. Froman, and C. Y. Hu. 1996. Chromium
picolinate reduces laying hen serum and egg yolk cholesterol. Prof.
Anim. Sci. 12:77-80.
Lien, T. E., Y. M. Horng, and K. H. Yang. 1999. Performance, serum char-
acteristics, carcass traits and lipid metabolism of broilers as affected by
supplement of chromium picolinate. Br. Poult. Sci. 40:357-363.
Lindemann, M. D. 1999. Chromium and swine nutrition. J. Trace Elem.
Exp. Med. 12:149-161.
Lindemann, M. D., A. F. Harper, and E. T. Korngay. 1995. Further assess-
ment of the effects of supplementation of chromium from chromium
picolinate on fecundity in swine. J. Anim. Sci. 73(Suppl. 1):185 (Abstr.).
Marino-Balsa, J. C, E. Poza, E. Vazquez, and R. Beiras. 2000. Compara-
tive toxicity of dissolved metals to early larval stages of Palaemon ser-
ratus, Maja squinado, and Homarus gammarus. Arch. Environ. Contam.
Toxicol. 39:345-351.
Mertz, W. 1993. Chromium in human nutrition: a review. J. Nutr.
123:626-633.
Mooney, K. W., andG. L. Cromwell. 1997. Efficacy of chromium picolinate
and chromium chloride as potential carcass modifiers in swine. J. Anim.
Sci. 75:2661-2671.
Muramoto, S. 1981. Influence of complexans (NTA, EDTA) on the toxicity
of trivalent chromium (chromium chloride, sulfate) at levels lethal to
fish. J. Environ. Sci. Health A16:605-610.
Ng, W., and R. P. Wilson. 1997. Chromic oxide inclusion in the diet does
not affect glucose utilization or chromium retention by channel catfish,
Ictalurus punctatus. J. Nutr. 127:2357-2362.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
Offenbacher, E. G., F. X. Pi-Sunyer, and B. J. Stoecker. 1997. Chromium.
Pp. 389^12 in Handbook of Nutritionally Essential Mineral Elements,
B. L. O'Dell and R. A. Sunde, eds. New York: Marcel Dekker.
Olin, K. L., D. M. Stearns, W. H. Ai'mstrong, and C. L. Keen. 1994. Com-
parative retention/absorption of ^'Cr picolinate in a rat model. Trace
Elem. Electroly. 11:182-186.
Page, T. G., L. L. Southern, T. L. Ward, and D. L. Thompson, Jr. 1993.
Effect of chromium picolinate on growth and serum and carcass traits of
growing-finishing pigs. J. Anim. Sci. 71:656-662.
Rosebrough, R. W., and N. C. Steele. 1981. Effect of supplemental dietary
chromium or nicotinic acid on carbohydrate metabolism during basal,
starvation, and refeeding periods in poults. Poult. Sci. 60:407^17.
Schachter, S., R.W.Nelson, and C. A. Kirk. 2001. Oral chromium picohnate
and control of glycemia in insulin-treated diabetic dogs. J. Vet. Intern.
Med. 15:379-384.
Schwartz, K., and W. Mertz. 1959. Chromium (III) and the glucose toler-
ance factor. Arch. Biochem. Biophys. 85:292-295.
Spears, J. W. 2000. Micronutrients and immune function in cattle. Proc.
Nutr. Soc. 59:587-594.
Spears, J. W., K. E. Lloyd, M. E. Tiffany, and M. T. Socha. 2004. Effect of
supplemental chromium on tissue chromium concentrations in cattle. J.
Anim. Sci. 82(Suppl. 1):43 (Abstr.).
Steele, N. C, and R. W. Rosebrough. 1979. Trivalent chromium and nico-
tinic acid supplementation for the turkey poult. Poult. Sci. 58:983-984.
Sullivan, T. W., J. H. Douglas, and N. J. Gonzalez. 1994. Levels of various
elements of concern in feed phosphates of domestic and foreign origin.
Poult. Sci. 73:520-528.
Tacon, A. G., Jr., and M. M. Beveridge. 1982. Effects of dietary trivalent
chromium on rainbow trout. Nutr. Rep. Int. 25:49-56.
Toepfer, E. W., W. Mertz, M. M. Polansky, E. E. Roginski, and W. R. Wolf.
1976. Preparation of chromium-containing material of glucose toler-
ance factor activity from brewer's yeast and by synthesis. J. Agric. Food
Chem. 25(1): 162-166.
USGS (U.S. Geological Survey). 1984. Element concentrations in soils and
other surficial materials of the conterminous United States. United States
Geological Survey Professional Paper 1270. Washington, D.C.: U.S.
Government Printing Office.
Vincent, J. B. 2001. The bioinorganic chemistry of chromium (III). Polyhe-
dron 20:1-26.
Ward, T. L. 1995. Dietary chi'omium supplementation for pigs and chick-
ens. Ph.D. dissertation, Louisiana State University, Baton Rouge.
WHO (World Health Organization). 1988. Chromium. Environmental
Health Criteria 61. Geneva: World Health Organization.
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CHROMIUM
123
TABLE 11-2 Chromium Concentrations in Fluids and Tissues of Animals (mg/kg)"
Egg
Egg
Animal
Quantity
Source
Duration
Route
Muscle
Liver
Kidney
Heart
white
yolk
Reference
Cattle
Control
+0.4 mg/kg
+0.8 mg/kg
CrCl,
Cr nieotinate
146 d
Diet
25
21
20
13
12
11
Spears et al., 2004
Cattle
Control
+0.8 mg/kg
Cr methionine
125 d
Diet
116
71
41
38
108
127
Spears et al., 2004
Pigs
Control
80 d
Diet
2
9
10
8
Ward, 1995
+0.2 mg/kg
CrCl,
6
17
15
19
+0.2 mg/kg
Cr picolinate
3
19
42
12
J
Pigs
Control
50 d
Diet
<1.5
21
27
4
Anderson et al..
+0.3 mg/kg
Cr picolinate
<1.5
29
57
11
1997b
Rats
Control
+100 mg/kg
+100 mg/kg
CrCl,
Cr picolinate
20 wk
Diet
6
90
550
8
700
2,200
Anderson et al., 1
1997a
Turkey hens
Control
35 d
Diet
3
6
14
4
14
29
Anderson et al., 1989
+25 mg/kg
CrClj
4
106
367
8
9
27
+100 mg/kg
CrClj
10
494
933
35
15
56
+200 mg/kg
CrCl:,
13
959
2,254
52
"Values are on a dry matter basis.
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12
Cobalt
INTRODUCTION
Cobalt (Co) is a silvery-white, hard metal with an atomic
number of 27 and an atomic weight of 58.93. Most common
compounds of cobalt have an oxidation state of +2 or +3
(Greenwood and Earnshaw, 1997). The +2 valence is stable
in aqueous solution and is the major form of cobalt found in
simple salts. In contrast, cobalt (+3) is a strong oxidizing
agent and is unstable in aqueous solution. However, cobalt
(+3) can form numerous coordination complexes with nitro-
gen-donor ligands and is the form of cobalt present in vita-
min Bjj. Cobalt is known for its magnetic properties. The
element is easily magnetized and retains its magnetism un-
der a wide range of environmental conditions.
Linnaeite (CO3S4), safforite (CoAsj), glaucodot (CoAsS),
and erythrite (Co3(As204)2) are the most important ores of
cobalt (ATSDR, 2001). These ores are associated with
nickel, copper, and lead, and most of the cobalt produced is
recovered as a by-product of ores treated for recovery of
nickel or copper. The largest cobalt reserves are in Zaire,
Zambia, Morocco, Canada, and Australia. Cobalt deposits in
the United States are not concentrated enough to allow eco-
nomical recovery of the metal. With the exception of a neg-
ligible amount of by-product cobalt produced from some
mining operations, no cobalt is mined or refined in the United
States (ATSDR, 2001). Reported U.S. use of cobalt metal in
2003 was 8,000 metric tons (USGS, 2004).
A major use of metallic cobalt is in the production of
superalloys that are used in gas turbine aircraft engines
(ATSDR, 2001). It is also used in magnetic alloys and alloys
that require hardness, wear resistance, and corrosion resis-
tance. In addition, cobalt compounds are used (1) as pig-
ments (blue) in glass, ceramics, and paint; (2) as catalysts in
the petroleum industry; and (3) to hasten the oxidation and,
thus, drying of oil-based paints. Gamma rays from radioac-
tive ^°Co are widely used to sterilize medical devices, as an
external source in radiography and radiotherapy, and for food
irradiation.
ESSENTIALITY
The only known function of cobalt is as an essential com-
ponent of vitamin 6,2 (cobalamin). Vitamin Bj2 contains
cobalt (H-3) surrounded by six coordinately linked groups to
form an octahedron. Vitamin Bjj is a cof actor for the en-
zymes methylmalonyl CoA mutase and methionine synthase.
Methylmalonyl CoA mutase is responsible for conversions
of methylmalonyl CoA to succinyl CoA and is important in
propionate metabolism. Methionine synthase is involved in
the regeneration of methionine following loss of its methyl
group and in the maintenance of biologically active folate
concentrations in tissues.
Mammals lack the ability to synthesize vitamin B|2, and
nonruminant animals require a dietary source of vitamin Bp.
Vitamin B|2 can be synthesized from inorganic cobalt by
certain bacteria and algae (Smith, 1997). Ruminal bacteria
synthesize enough vitamin B|2 to meet the requirements of
ruminants provided that adequate dietary cobalt is supplied.
Ruminants require 0. 10 to 0. 15 mg Co/kg diet to allow suffi-
cient synthesis of vitamin Bjj by ruminal bacteria to meet
the animal's requirement. In certain areas of the world, for-
age cobalt concentrations are well below requirements of
ruminants due to low soil cobalt concentrations. Cobalt defi-
ciency in ruminants, caused by low dietary intake of cobalt,
results in loss of appetite, reduced growth rate or even loss in
body weight in severe cases, and anemia (Underwood and
Suttle, 1999).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Biological samples of plant and animal origin are gener-
ally low (<0.5 mg/kg DM) in cobalt. Graphite furnace
atomic absorption spectrometry with Zeeman background
correction is the method of choice for measuring low con-
centrations of cobalt (Smith, 1997). Neutron activation
analysis and differential pulse anodic stripping voltammetry
124
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COBALT
125
also have been used for determining low concentrations of
cobalt. Flame atomic absorption spectrometry is not sensi-
tive enough to detect cobalt concentrations normally found
in biological samples.
Contamination of samples with cobalt during collection,
storage, and preparation of samples for analysis should be
avoided. Disposable syringes and technical-grade anticoagu-
lants may contaminate blood samples with cobalt. Wet
ashing with acid is the preferred method for preparing solid
samples for cobalt analysis. Dry ashing may result in losses
of cobalt.
REGULATION AND METABOLISM
Absorption and Metabolism
In weanling rats fed physiological concentrations of co-
balt, from CoClj, apparent and true absorption of cobalt av-
eraged 28 and 29.8 percent, respectively (Kirchgessner et
al., 1994). Mice absorbed 26 percent of an oral dose of la-
beled cobalt (Toskes et al., 1973). Absorption of cobalt was
very high in young rats (1 to 20 days of age) and decreased
greatly by 30 days of age (Naylor and Harrison, 1995).
Cobalt absorption also declined with age in guinea pigs.
However, independent of age, cobalt absorption was much
lower in guinea pigs than in rats (Naylor and Harrison, 1995).
In nonruminants, cobalt and iron appear to share a common
intestinal transport system and cobalt absorption is greatly
increased in iron deficiency (Thomson et al., 1971). Absorp-
tion of cobalt is very low (1 to 2 percent) in ruminants
(Looney et al., 1976; Van Bruwaene et al., 1984). Low
absorption of cobalt in ruminants may relate to binding of
cobalt by ruminal microorganisms. A portion of cobalt in-
gested by ruminants is used by ruminal bacteria for synthesis
of vitamin Bp. It has been estimated that the efficiency of
cobalt conversion to vitamin Bj, ranges from 1.7 to 18 per-
cent (Smith and Marston, 1970).
Absorbed cobalt is primarily excreted in urine with small
amounts excreted via fecal endogenous routes (Kirchgessner
et al., 1994). Cobalt concentrations in tissues are generally
low (1 mg/kg DM or less), but liver and kidney cobalt con-
centrations increase dramatically when animals are fed high
dietary cobalt (Henry et al., 1997). Liver has the highest con-
centration of cobalt followed by the kidney and heart. Be-
cause cobalt is required in the mammalian system in the form
of vitamin B|2, transport and intermediatory metabolism of
cobalt per se has received little attention.
IVIetabolic Interactions and IVIechanisms of Toxicity
Sulfur amino acids, especially cysteine, may form stable
complexes with cobalt and reduce its absorption. Supple-
menting cysteine or methionine in excess of dietary require-
ments reduced liver and kidney cobalt concentrations in
chicks fed high dietary cobalt (Southern and Baker, 1981).
Iron and cobalt interact in the intestinal mucosal and are
mutually antagonistic (Thomson et al., 1971). Supplementa-
tion of cobalt at 100 mg/kg diet or higher reduced serum and
liver iron in pigs (Huck and Clawson, 1976). In chicks
supplemented with high concentrations (100 to 400 mg/kg
diet) of cobalt, liver and kidney cobalt concentrations were
greatly elevated when chicks were fed an iron-deficient diet
(Blalock, 1985). The addition of 100 or 1,000 mg Fe/kg to
the high cobalt diets greatly reduced liver and kidney cobalt
concentrations.
Feeding elevated but nontoxic concentrations of cobalt
increased zinc absorption in chicks fed diets low in zinc
(Chung et al., 1977). Similarly, growth and zinc status of
pigs fed a low zinc diet were improved by the addition of 27
or 54 mg Co/kg diet (Chung et al., 1976).
A number of possible mechanisms for cobalt toxicity may
exist. Exposure to cobalt may cause oxidative damage to
tissues by causing generation of oxygen radicals and free
radical-induced DNA damage (Kasprzak et al., 1994). In
support of this hypothesis, selenium and vitamin E adminis-
tration offered protection against cobalt-induced cardiomy-
opathy in pigs (Van Vleet et al., 1977). Increasing dietary
cysteine, a precursor of the antioxidant glutathione, also al-
leviated growth depression resulting from cobalt toxicosis in
chicks (Southern and Baker, 198 1). Another possible mecha-
nism of CO bait toxicity relates to the ability of co bait to block
calcium channels and thus, alter cellular calcium influx
(Yamatani et al., 1998). Some cobalt toxicosis signs may
relate to the effect of cobalt on heme and heme-containing
enzymes (ATSDR, 2001). Cobalt is believed to inhibit two
different sites in the heme biosynthetic pathway.
SOURCES AND BIOAVAILABILITY
Cobalt occurs naturally in the Earth's crust at an average
concentration of 20 to 25 mg/kg (ATSDR, 2001). Soils gen-
erally contain from 1 to 40 mg Co/kg and the average cobalt
concentration in U.S. soils is 7.2 mg/kg. Cobalt concentra-
tions in surface and groundwater are usually between 1 and
10 |Jg/L. Elevated concentrations of cobalt in soil and water
can result from activities such as mining and processing of
cobalt-bearing ores, disposing of cobalt-containing wastes,
burning of fossil fuels, copper and nickel smelting and refin-
ing, and applying cobalt containing sludge or fertilizers to
soil (ATSDR, 2001).
Most animal feedstuffs are low in cobalt (<0.5 |ig/kg).
Concentration of cobalt in plant material is dependent on
soil cobalt, soil pH, and plant species. Soil uptake of cobalt
by forages decreases as soil pH increases. Legumes are
higher in cobalt than grasses when grown on cobalt adequate
soil (Underwood and Suttle, 1999). Soils deficient in cobalt
(< than 3.0 mg Co/kg soil) are found in certain areas of the
southeastern and northeastern United States. Ruminants
grazing or consuming forages grown in these areas require
cobalt supplementation to prevent deficiency. Cereal grains
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126
MINERAL TOLERANCE OF ANIMALS
usually contain deficient concentrations (<0.06 mg/kg) of
cobalt. Feeds of animal origin, with the exception of liver
products, are also low in cobalt.
Cobalt is generally supplemented to ruminant diets as
C0CO3, C0SO4, or various organic forms. Kawashima et al.
(1997a) compared bioavailability of different cobalt sources
based on tissue cobalt accumulation in lambs fed high (40
mg Co/kg) dietary cobalt. Feed grade sources of C0CO3 and
cobalt glucoheptonate were similar in bioavailability to re-
agent grade CoSO^-VHjO. Cobalt oxide was approximately
20 percent as bioavailable as CoSO^-VHjO based on accu-
mulation of cobalt in various tissues. In vitro studies indi-
cated that CO3O4 was totally unavailable for synthesis of vi-
tamin Bj2 by ruminal microorganisms (Kawashima et al.,
1997b). Bioavailability of cobalt from cobalt propionate was
similar to C0CO3 in steers based on plasma and liver vitamin
Bj2 concentrations (Tiffany et al., 2003). Absorption of co-
balt from cobalt naphthenate, an organometallic cobalt-con-
taining compound used as a drier in paint, appears to be simi-
lar to C0CI2 in rats (Firriolo et al., 1999).
TOXICOSIS
Cobalt toxicosis in animals is very rare because concen-
trations of cobalt normally present in animal diets are much
lower than those needed to cause toxicosis. Suspected cases
of cobalt toxicosis, due to excessive cobalt addition to water,
feed, or pastures, have been reported in cattle (Dickson and
Bond, 1974). Cobalt toxicosis is not likely to occur in
nonruminants unless environmental contamination of feed
or water occurs.
Single Dose and Acute
High oral doses of cobalt caused sedation, diarrhea, trem-
ors, convulsions, and death in rats (Speijers et al., 1982).
Histological changes were observed in heart, liver and kid-
ney of rats that died. The LD^q in rats for CoCl2-6H20 has
ranged from 42.4 to 190 mg Co/kg BW in various studies
(ATSDR, 2001; Speijers et al., 1982). Oral administration of
100 mg Co/kg BW, as C0SO4, for 3 days in young pigs re-
sulted in cardiomyopathy, listlessness, diarrhea, and high
mortality (Van Vleet et al., 1977). Severity of cardiomyopa-
thy was greater in pigs that were inherently susceptible to
stress compared to nonstress-susceptible pigs (Van Vleet et
al., 1977).
Chronic
Studies evaluating oral ingestion of high concentrations
of cobalt are summarized in Table 12-1. Cobalt concentra-
tions as low as 100 mg Co/kg diet have reduced weight gain
in young chicks (Hill, 1974, 1979a; Ling and Leach, 1979).
Lower concentrations of cobalt may affect disease suscepti-
bility as chicks fed 50 mg Co/kg diet had increased mortality
following experimental infection with Salmonella
gallinarum (Hill, 1974). Addition of 200 mg Co/kg or higher
to chick diets has increased mortality in noninoculated birds
(Hill, 1974; Diaz et al., 1994) and resulted in histological
lesions in the digestive tract, liver, heart, and skeletal muscle
(Diaz et al., 1994).
The amount of cobalt that can be tolerated without ad-
verse effects in rats appears to be similar to chicks. In rats
fed an iron-adequate diet, 50 mg Co/kg did not affect weight
gain, but addition of 100 mg Co/kg diet or higher reduced
weight gain and feed intake and caused some mortality
(Huck, 1975). However, as little as 25 mg Co/kg diet re-
duced weight gain and feed intake when rats were fed an
iron-deficient diet (Huck, 1975). Myocardial damage has
been seen in adult rats given 12.4 mg Co/kg BW for 21 days
(Morvai et al., 1993). Testicular degeneration has been ob-
served in male rats (Corrier et al., 1985; Anderson et al.,
1992) and mice (Anderson et al., 1993) given high oral doses
of cobalt. Oral administration of cobalt at 5.2 mg Co/kg BW
or higher during gestation has impaired fetal development in
mice and rats, and increased mortality in pregnant rabbits
(Szakmary et al., 2001).
Based on limited research, higher concentrations of co-
balt are required in pigs than in chicks and rats to cause toxi-
cosis. Addition of up to 200 mg Co/kg diet did not cause
observable adverse effects in young pigs (Huck and
Clawson, 1976). Cobalt concentrations of 400 or 600 mg/kg
diet caused anorexia, growth depression, reduced blood he-
moglobin and hematocrit, incoordination, muscular tremors,
stiff legs, and humped back in pigs (Huck and Clawson,
1976).
Older studies indicated that cattle can tolerate up to 0.86
mg Co/kg BW without adverse effects (Ely et al., 1948;
Keener etal., 1949). Higher concentrations of cobalt reduced
feed intake and caused hyperchromemia (Keener et al.,
1949). No recent studies examining cobalt toxicosis in cattle
were found in the literature. Becker and Smith (1951) re-
ported that 4.4 mg Co/kg BW or higher, administered via
water, decreased feed intake in sheep. A daily dose of 1 1.0
mg Co/kg BW caused anemia and high mortality in sheep
(Becker and Smith, 1951). In a more recent study, adult rams
were given 3.0 or 4.5 mg Co/kg BW for 70 days (Corrier et
al., 1986). The dose of cobalt was then increased to 10 or 15
mg/kg BW for an additional 39 days. Tissue cobalt concen-
trations were greatly elevated in cobalt-dosed rams, but no
pathological or clinical manifestations of toxicosis were
found in this study. The addition of 40 mg Co/kg diet for 60
days also did not affect performance or general health of
lambs (Henry et al., 1997).
Factors Influencing Toxicity
Iron status greatly affects the concentration of cobalt re-
quired to produce a toxicosis. Cobalt absorption is increased
in iron deficiency (Valberg et al., 1969; Blalock, 1985), and
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COBALT
127
iron deficiency in cliicks (Chetty, 1972) and rats (Huck,
1975) lowered the concentration of cobalt required to de-
press growth by over 50 percent. The addition of 100 to 200
mg Fe/kg to diets adequate in iron partially alleviated cobalt-
induced growth depression but did not affect increased sus-
ceptibility of chicks to Salmonella gallinarum (Hill, 1974).
Increasing dietary concentrations of methionine or cys-
teine alleviates cobalt toxicosis. Addition of 0.5 or 1.0 per-
cent DL-methionine to a corn-soybean meal-based diet com-
pletely alleviated growth depression and reduced serum iron
concentrations in pigs fed 600 mg Co/kg diet (Huck and
Clawson, 1976). However, serum cobalt concentrations in
pigs were not reduced by methionine supplementation. In-
creasing dietary methionine or cysteine partially alleviated
reduced growth and feed efficiency noted in chicks fed 250
or 500 mg Co/kg diet (Southern and Baker, 1981). Cysteine
was more efficacious than methionine, when provided on an
isosulfurous basis, in alleviating cobalt toxicosis in chicks.
Sulfur amino acids may reduce cobalt toxicity by forming
stable complexes with cobalt in the digestive tract that are
poorly absorbed and/or by enhancing the detoxication of
absorbed cobalt (Baker and Czarnecki-Maulden, 1987). In-
creasing dietary protein from 10 to 20 or 30 percent partially
prevented growth depression but not increased susceptibility
to Salmonella gallinarum observed in chicks fed toxic levels
of cobalt (Hill, 1979a).
Selenium and vitamin E status may affect toxicity of co-
balt. Intramuscular injection of selenium and vitamin E, one
day prior to oral administration of 100 mg Co/kg BW, pro-
tected against cobalt-induced myocardial damage (Van Vleet
et al., 1977). Ascorbic acid addition to diets partially pre-
vented growth depression observed in chicks fed 200 mg
Co/kg (Hill, 1979b). Cobalt toxicosis in chicks was exacer-
bated by duodenal coccidiosis (Eimeria acervulina) in chicks
(Southern and Baker, 1982).
Based on studies showing a much higher cobalt absorp-
tion in young ( 1 to 20 days) rats and guinea pigs than in older
(30 to 200 days) animals, one would expect that lower con-
centrations of cobalt may be required to produce toxicosis in
young animals. Young calves appeared to be affected more
by lower concentrations of cobalt than older calves (Keener
et al., 1949).
TISSUE LEVELS
Cobalt is found in tissues at low concentrations (<1.0
mg/kg DM) when animals are fed normal dietary cobalt con-
centrations. Exposure of animals to high dietary cobalt
greatly increases concentrations of cobalt in a number of tis-
sues. Representative values in tissues from various animals
fed normal or high concentrations of cobalt are shown in
Table 12-2. Cobalt concentrations in liver and kidney in-
crease to the greatest extent with smaller increases in hearts
of animals fed high concentrations of cobalt. Increases in
muscle cobalt in animals given high concentrations of cobalt
are relatively small, and muscle cobalt was only 0.26 mg/kg
DM in lambs supplemented with 40 mg Co/kg diet for 60
days (Henry et al., 1997).
MAXIMUM TOLERABLE LEVELS
The maximum tolerable level for cobalt is defined as the
dietary level that, when fed for a defined period of time, will
not impair animal health and/or performance. A number of
factors can affect the maximum tolerable level for cobalt,
especially iron status of the animal and dietary concentration
of sulfur amino acids. Age and antioxidant status of the ani-
mal also appear to affect the level of cobalt that can be toler-
ated without adverse effects on animal performance or
health.
Chicks and rats are able to tolerate 50 mg Co/kg diet with-
out adverse effects on growth (Hill, 1974; Huck, 1975).
However, a 50 mg Co/kg diet increased disease susceptibil-
ity in chicks experimentally inoculated with Salmonella
gallinarum (Hill, 1974). In pigs, cobalt concentrations
greater than 200 mg/kg diet were required to depress growth
and feed efficiency (Huck and Clawson, 1976). Older stud-
ies suggested that calves can tolerate up to 0.86 mg Co/kg
BW (Ely et al., 1948). This would be 34 mg/kg diet if dry
matter intake is assumed to be 2.5 percent of BW. Controlled
studies to assess cobalt tolerance have not been reported in
older cattle. Yearling sheep tolerated 3.5 mg Co/kg BW (ap-
proximately 144 mg Co/kg diet) for 56 days (Becker and
Smith, 1951), while adult male sheep tolerated approxi-
mately 180 mg Co/kg diet for 109 days without adverse ef-
fects (Corrier et al., 1986). Studies have not been conducted
to determine if such high concentrations of cobalt can be
safely tolerated by younger lambs or during fetal development.
Based on available literature, the maximum tolerable lev-
els for cobalt were set at 25 mg/kg diet for chicks, rats, sheep,
and cattle, and 100 mg/kg diet for swine. Insufficient data
are available to set a maximum tolerable level for cobalt for
dogs and cats. At dietary cobalt concentrations up to the
maximum tolerable levels indicated, increases in cobalt in
edible tissue are not likely to present a human health con-
cern. However, animals fed diets containing the maximum
tolerable level of cobalt may have kidney cobalt concentra-
tions that exceed standards for human health (see Maximum
Tolerable Levels chapter).
FUTURE RESEARCH NEEDS
Additional work is needed with swine to confirm earlier
research indicating that growing pigs could tolerate consid-
erably higher dietary concentrations of cobalt than chicks or
rats. The most pressing need for cobalt toxicosis research is
in ruminants, especially cattle. Studies examining cobalt tol-
erance in growing calves were conducted in the 1940s, and
no research has been conducted to define levels of cobalt
that can be safely tolerated by older cattle. In contrast, cobalt
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128
MINERAL TOLERANCE OF ANIMALS
Studies in sheep have all been conducted with yearling or
adult animals, and these studies indicate that sheep may be
able to tolerate much higher cobalt concentrations than cattle.
It is unclear if the discrepancy in cobalt tolerance reported
between sheep and cattle is truly a species difference or an
age effect.
SUMMARY
Cobalt functions as an essential component of vitamin
Bj2- Nonruminant animals do not require a dietary source of
cobalt because mammalian tissues are unable to synthesize
vitamin Bj2 from inorganic cobalt. Ruminal microorganisms
synthesize vitamin Bjj from cobalt, and the vitamin Bjj pro-
duced serves to meet the animal's requirement. Therefore,
ruminants have a dietary requirement for cobalt. Cobalt toxi-
cosis is generally not a practical problem because concentra-
tions of cobalt needed to cause toxicosis are much higher
than those normally found in animal diets. Errors in formu-
lation of mineral supplements for ruminants could result in
cobalt toxicosis. However, toxic levels of cobalt are over
100 times greater than dietary requirements for ruminants.
REFERENCES
ATSDR (Agency for Toxic Substances and Disease Registry). 2001. Toxi-
cological profile for cobalt. Atlanta, GA: tJ.S. Department of Health
and Human Services, Public Healtti Service. Available at http://
www.atsdr.cdc.gov/toxprofiles/tp33.html.
Anderson, M. B., N. G. Pedigo, R. P. Katz, and W. J. George. 1992. Histo-
pathology of testes from mice chronically treated with cobalt. Reprod.
Toxicol. 6:41-50.
Anderson, M. B., K. Lepak, V. Farinas, and W. J. George. 1993. Protective
action of zinc against cobalt-induced testicular damage in the mouse.
Reprod. Toxicol. 7:49-54.
Baker, D. H., and G. L. Czarnecki-Maulden. 1987. Pharmacologic role of
cysteine in ameliorating or exacerbating mineral toxicities. J. Nutr.
117:1003-1010.
Becker, D. E., and S. E. Smith. 1951. The level of cobalt tolerance in year-
ling sheep. J. Anim. Sci. 10:266—271.
Blalock, T. L. 1985. Studies on the role of iron in the reversal of zinc,
cadmium, vanadium, nickel, and cobalt toxicities in broiler pullets.
Ph.D. dissertation. North Carolina State University, Raleigh.
Chetty, K. N. 1972. Interactions of cobalt and iron in chicks. Ph.D. disser-
tation. North Carolina State University, Raleigh.
Chung, A. S., W. G. Hoekstra, and R. H. Grummer. 1976. Supplemental
cobalt or nickel for zinc deficient G. F. pigs. J. Anim. Sci. 42:1352-
1353 (Abstr.).
Chung, A. S., M. L. Sunde, R. H. Grummer, and W. G. Hoekstra. 1977. The
sparing effect of cobalt in chicks. Fed. Proc. 37:668 (Abstr).
Clyne, N., L. E. Lins. S. K. Pehrsson, A. Lundbereg, and J. Werner. 1988.
Distribution of cobalt in myocardium, skeletal muscle and serum in
exposed and unexposed rats. Trace Elem. Med. 5:52-54.
Corrier, D. E., H. H. Mollenhauer, D. E. Clark, M. F. Hare, and M. H.
Elissalde. 1985. Testicular degeneration and necrosis induced by di-
etary cobalt. Vet. Pathol. 22:610-616.
Corrier, D. E.. L. D. Rowe, D. E. Clark, and M. F. Hare. 1986. Tolerance
and effect of chronic dietary cobalt on sheep. Vet. Hum. Toxicol.
28:216-219.
Diaz, G. J., R. J. Julian, and E. J. Squires. 1994. Lesions in broiler chickens
following experimental intoxication with cobalt. Avian Dis. 38:308-316.
Dickson, J., and M. P. Bond. 1974. Cobah toxicity in cattle. Aust. Vet. J.
50:236.
Ely, R. E., K. M. Dunn, and C. F. Huffman. 1948. Cobalt toxicity in calves
resulting from high oral administration. J. Anim. Sci. 7:239-246.
Firriolo, J. M., F. Ayala-Fierro, I. G. Sipes, and D. E. Carter. 1999. Absorp-
tion and disposition of cobalt naphthenate in rats after a single oral dose.
J. Toxicol. Environ. Health 58:383-395.
Greenwood, N. N., and A. Earnshaw. 1997. Chemistry of the Elements.
(2nd ed.) Oxford: Butterworth-Heinemann.
Henry, P. R., R. C. Littell, and C. B. Ammerman. 1997. Bioavailability of
cobalt sources for ruminants. 1 . Effects of time and dietary cobalt con-
centration on tissue cobalt concentration. Nutr. Res. 17:947-955.
Hill, C. H. 1974. Influence of high levels of minerals on the susceptibility of
chicks to Salmonella gallinarum. J. Nutr. 104:1221-1226.
Hill, C. H. 1979a. The effect of dietary protein levels on mineral toxicity in
chicks. J. Nutr. 109:501-507.
Hill, C. H. 1979b. Studies on the ameliorating effect of ascorbic acid on
mineral toxicities in the chick. J. Nutr. 109:84—90.
Huck, D. W. 1975. The study of cobalt toxicity in pigs and rats. Ph.D.
dissertation. North Carolina State University, Raleigh.
Huck, D. W., and A. J. Clawson. 1976. Excess dietary cobalt in pigs. J.
Anim. Sci. 43:1231-1246.
Kasprzak, K. S., T. H. Zastawny, and S. L. North. 1994. Oxidative DNA
base damage in renal, hepatic, and pulmonary chromatin of rats after
intraperitoneal injection of cobalt (II) acetate. Chem. Res. Toxicol.
7:329-335.
Kawashima, T., P. R. Henry, C. B. Ammerman, R. C. Littell, and J. Price.
1997a. Bioavailability of cobalt sources for ruminants. 2. Estimation of
the relative value of reagent grade and feed grade cobalt sources from
tissue cobalt accumulation and vitamin Bp concentrations. Nutr. Res.
17:957-974.
Kawashima, T., P. R. Henry, D. G. Bates, C. B. Ammerman, R. C. Littell,
and J. Price. 1997b. Bioavailability of cobalt sources for ruminants. 3.
In vitro ruminal production of vitamin Bp and total corrinoids in re-
sponse to different cobalt sources and concentrations. Nutr. Res.
17:975-987.
Keener, H. A., G. P. Percival, K. S. Mon-ow, and G. H. Ellis. 1949. Cobalt
tolerance in young dairy cattle. J. Dairy Sci. 32:527—533.
Kirchgessner, M., S. Reuber, and M. Kreuzer. 1994. Endogenous excretion
and true absorption of cobalt as affected by the oral supply of cobalt.
Biol. Trace Elem. Res. 41:175-189.
Ling, J. R., and R. M. Leach, Jr. 1979. Studies on nickel metabolism: inter-
action with other mineral elements. Poult. Sci. 58:591-596.
Looney, J. W., G. Gille, R. L. Preston, E. R. Graham, and W. H. Pfander.
1976. Effects of plant species and cobalt intake upon cobalt utilization
and ration digestibility by sheep. J. Anim. Sci. 42:693-698.
Morvai, V., E. Szakmary, E. Tatrai, G. Ungvary, and G. Folly. 1993. The
effects of simultaneous alcohol and cobalt chloride administration on
the cardiovascular system of rats. Acta Physiol. Hung. 81(3):253-261.
Naylor, G. P. L., and J. D. Harrison. 1995. Gastrointestinal iron and cobalt
absorption and iron status in young rats and guinea pigs. Human Exp.
Toxicol. 14:949-954.
Paternain, J. L., J. L. Domingo, and J. Corbella. 1988. Developmental tox-
icity of cobalt in the rat. J. Toxicol. Environ. Health 24:193-200.
Smith, R. M. 1997. Cobalt. Pp. 357-387 in Handbook of Nutritionally Es-
sential Mineral Elements, B.L.O'Dell and R. A. Sunde, eds. New York:
Marcel Dekker.
Smith, R. M., and H. R. Marston. 1970. Production, absorption, distribu-
tion, and excretion of vitamin Bp in sheep. Br. J. Nutr. 24:857—877.
Southern, L. L., andD. H. Baker. 1981. The effect of methionine or cysteine
on cobalt toxicity in the chick. Pouh. Sci. 60:1303-1308.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
COBALT
129
Southern, L. L. and D. H. Balcer. 1982. Eimeria acervuUna injection in
cliicks fed cobalt in the presence or absence of excess dietary methion-
ine. J. Nutr. 112{6):1220-1223.
Speijers, G. J. A., E. 1. Krajnc, J. M. Berkvens, and M. J. van Logten. 1982.
Acute oral toxicity of inorganic cobalt compounds in rats. Food Chem.
Toxicol. 20:311-314.
Szakmary, E., G. Ungvary, A. Hudak, E. Tatrai, M. Naray, and V. Morvai.
200 1 . Effects of cobalt sulfate on prenatal development of mice, rats,
and rabbits and on early postnatal development of rats. J. Toxicol.
Environ. Health 62:367-386.
Thomson, A. B. R., L. S. Valberg, and D. C. Sinclair. 1971. Competitive
nature of the intestinal transport mechanism for cobalt and iron in the
rat. J. Clin. Invest. 50:2384-2394.
Tiffany, M. E., J. W. Spears, L. Xi, and J. Horton. 2003. Influence of dietary
cobalt source and concentration on performance, vitamin Bj^ status,
and ruminal and plasma metabolites in growing and finishing steers. J.
Anim.Sci. 81:3151-3159.
Toskes, P. P., G. W. Smith, and M. E. Conrad. 1973. Cobalt absorption in
sex-linked anemia mice. Am. J. Clin. Nutr. 26:435^37.
Underwood, E. J., and N. F. Suttle. 1999. The Mineral Nutrition of Live-
stock (3rd ed). New York: CABl Publishing.
USGS (U.S. Geological Survey). 2004. Mineral Commodity Summaries.
Available at http://minerals.usgs.gov/minerals/pubs/commodity/cobalt.
Accessed on March 27, 2005.
Valberg, L. S., L. Ludwig, andD. Olatunbosun. 1969. Alteration in cobalt
absorption in patients with disorders of iron metabolism.
Gastreonterology 56:241—251.
Van Bruwaene, R., G. B. Gerber, R. Kirchmann, J. Colard, and J. Van
Kerkom. 1984. Metabolism of ^'Cr, ^''Mn, '"'Fe and ^"Co in lactating
dairy cows. Health Phys. 46:1069-1082.
Van Vleet, J. F., A. H. Rebar, and V. J. Ferrans. 1977. Acute cobalt and
isoproterenol cardiotoxicity in swine: protection by selenium- vitamin E
supplementation and potentiation by stress-susceptible phenotype. Am.
J. Vet. Res. 38:991-1002.
Yamatani, K., K. Saito, and Y. Ikezawa. 1998. Relative contribution of
Ca^+-dependent mechanism in glucagon-induced glucose output from
the liver. Aich. Biochem. Biophys. 355:175-180.
Copyright © National Academy of Sciences. All rights reserved.
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inemi Tnlemnce nf Animals- Sennnd Revised Edition
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130
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COBALT
133
TABLE 12-2 Cobalt Concentrations in Fluids and Tissues of Animals (mg/kg)
Animals Quantity
Source Duration Route Serum Liver Kidney
Muscle
Heart
Spleen
Reference
Rats
Chicks
Control
4.2 mg/kg BW
Control
+100 mg/kg
+200 mg/kg
+400 mg/kg
CoSO^-
VH^O
CoCL-
56 d
Diet 0.001
0.12
Diet
0.02"
0.48
0.14°
1.50
1.11
4.53
0.15"
2.83
8.25
10.24
Sheep Control CoClj- 109 d Gavage 0.09 0.09" 0.09"
3.0-10.0 mg/kg BW eH^O 0.98 8.50 2.10
4.5-15.0 mg/kg BW ' 1.33 8.70 1.90
Sheep Control CoS04- 60 d Diet 0.20* 0.77*
+20 mg/kg 7H,0 3.74 3.27
+40 mg/kg ' 7.33 4.83
0.05"
1.62
Clyne et al.,
1988
Blalock, 1985
Pigs
Control
CoClj-
84 d
Diet
1.16*
0.39*
ND^
0.62*
Huck and
+200 mg/kg
6H,0
8.40
16.72
2.90
4.46
Clawson,
+400 mg/kg
10.85
39.73
5.40
5.99
1976
+600 mg/kg ^H
^^^^
^^1
^^^h
12.72
35.89 ^H
B 9.28
6.89
0.10*
0.14
0.26
0.13*
0.59
1.26
0.10*
0.39
0.67
Corrier et al.,
1986
Henry et al.,
1997
"Wet tissue basis.
*Dry tissue basis.
^Not detectable.
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13
Copper
INTRODUCTION
Copper (Cu) is one of the oldest metals known to hu-
mans. It occurs naturally, to a small extent as the free metal,
but most copper occurs as compounds in the +1 (cuprous) or
+2 (cupric) oxidation state. Cuprous compounds are gener-
ally colorless and are rapidly oxidized to the cupric form in
aqueous solution. Cupric compounds are blue or green in
color and +2 is the most important oxidation state of copper.
Copper has a high electrical and thermal conductivity, and is
highly resistant to corrosion (ATSDR, 2002). These unique
properties have made copper one of the most important in-
dustrial metals.
Copper is found primarily as oxide, sulfide, or carbonate
ores with chalcocite (CUjS), chalcopyrite (CuFeSj), mala-
chite (CuC03(CuOH2)), and cuprite (Cu,0) ores as the most
important sources. Chile is the world's leading copper pro-
ducer followed by the United States. In the United States,
1.12 million tons of copper were mined and 860,000 tons
were imported for processing in 2003 (USGS, 2004). An
additional 210,000 tons of copper were reclaimed in the
United States by recycling from old scrap in 2003.
Brass, bronze, gun metal, and monel metal are important
alloys that contain copper. Copper alloys are used in construc-
tion, electrical products, transportation equipment, industrial
machinery and equipment, coins, and consumer products
(ATSDR, 2002). Copper compounds are also used as fungi-
cides, in fertilizers, in nutritional supplements for humans
and animals, and as algicides in reservoirs and streams.
(Linder, 2002). Copper-dependent enzymes function in en-
ergy metabolism, maturation and stability of collagen and
elastin, pigmentation, the antioxidant defense system, and
iron metabolism, as well as other biological processes. Defi-
ciency of copper may result in cardiovascular disorders (car-
diac failure or rupture of the aorta), depigmentation and im-
paired keratinization of hair and wool, anemia, reduced
growth, neonatal ataxia, bone abnormalities, and impaired
immune responses. Deficiency signs vary depending on ani-
mal species and the severity of the deficiency. Copper defi-
ciency is a practical problem in ruminants in many areas of
the world. Most copper deficiencies in ruminants are due to
the presence of antagonists (molybdenum, sulfur, and iron)
in feeds that greatly impair copper metabolism.
Nonruminant animals generally require between 4 and 8
mg Cu/kg diet (Underwood and Suttle, 1999). Copper re-
quirements appear to be higher in horses (Underwood and
Suttle, 1999). It is well documented that pharmacological
concentrations of copper (125 to 250 mg Cu/kg diet) can
stimulate growth and feed efficiency in swine (Cromwell et
al., 1989) and poultry (Harms and Buresh, 1987; Pesti and
Bakalli, 1996). The mechanism responsible for the growth-
promoting action of high dietary copper in nonruminants is
unclear. Copper requirements of ruminants vary from ap-
proximately 4 to over 20 mg Cu/kg diet, depending on di-
etary concentrations of copper antagonists (Underwood and
Suttle, 1999). Relatively low dietary concentrations of mo-
lybdenum and sulfur can increase copper requirements by 2-
to 3-fold.
ESSENTIALITY
Copper was reported to be essential for growth and he-
moglobin formation in rats in 1928 (Underwood and Suttle,
1999). Subsequent research indicated that copper was an es-
sential component of a number of enzymes including cyto-
chrome oxidase, lysyl oxidase, superoxide dismutase, tyro-
sinase, ceruloplasmin, and dopamine [3-monooxygenase
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Because of the abundance of copper in the environment,
precautions should be taken to avoid contamination when
collecting samples for copper analysis (WHO, 1998).
Vessels to be used in the collection of samples for copper
134
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COPPER
135
determination shiould be cleaned of dust and washied withi
dilute acid. Glassware and most plastics are relatively free of
copper contamination, but heavily pigmented plastics may
contain copper and should be avoided. Deionized water
should be used to dilute samples for copper analysis because
even distilled water can be contaminated with copper
through contact with copper plumbing and brass fixtures.
Wet ashing with acid in an open vessel digestion system or
closed microwave digestion system is the preferred method
for preparing solid samples for copper analysis. Acid(s) used
in the digestion process should be extremely low in copper,
and a blank should be carried through all procedures to cor-
rect for contamination.
Atomic absorption spectrophotometric (AAS) methods
(either flame or graphite furnace) are common methods used
for detennination of copper. Flame AAS has a detection limit
of 0.01-0.1 |Jg/mL, while graphite furnace AAS is much
more sensitive with a detection limit of 0.01-1.0 ng/mL
(Harris, 1997). Another common method for copper deter-
mination is inductively-coupled plasma atomic emission
spectroscopy (ICP-AES). Sensitivity of ICP-AES for copper
is similar to graphite furnace AAS and this method extends
linearity over a wider concentration range than AAS and al-
lows for multielement analysis.
REGULATION AND METABOLISM
Absorption and Metabolism
Major differences in copper metabolism exist between
nonruminant and ruminant animals. Studies in humans and
rats indicate that copper is fairly well absorbed (~30 to 75
percent) in nonruminants (Linder, 2002). Absorption of cop-
per occurs primarily from the small intestine. Percentage of
dietary copper absorbed is affected by dietary copper, being
higher when intake of copper is marginal or low relative to
requirements. In the intestinal mucosa, a portion of the cop-
per is bound to metallothionein or similar proteins (Linder,
2002). Binding to metallothionein prevents transfer of cop-
per to the intestinal serosa, and metallothionein-bound cop-
per can be lost in the feces during normal turnover of intes-
tinal cells. Metallothionein has a higher affinity for copper
than zinc, and high dietary zinc can reduce copper absorp-
tion by inducing synthesis of metallothionein (Harris, 1997).
In ruminants, with a functional rumen, copper absorption
is low (<1.0 to 10 percent) relative to nonruminants
(Underwood and Suttle, 1999). Low absorption of copper in
ruminants is largely due to complex interactions that occur
among copper, sulfur, and molybdenum in the ruminal envi-
ronment. Copper absorption is much higher (~75 percent) in
young ruminants prior to establishment of a ruminal micro-
flora (Underwood and Suttle, 1999).
Absorbed copper in portal blood binds to albumin and
transcuprein for transport primarily to the liver (Linder,
2002). In the liver, copper can be excreted via the bile, stored.
or used for synthesis of ceruloplasmin or other copper
metalloenzymes. Biliary excretion is the major mechanism
responsible for copper homeostasis. Copper excreted in bile
is present in forms that are poorly reabsorbed from the small
intestine. Liver copper concentrations (15 to 30 mg Cu/kg
DM) are well regulated in most nonruminants; however, bil-
iary copper excretion becomes saturated at high dietary cop-
per concentrations, and then liver copper accumulation oc-
curs. Genetic disorders, associated with impaired biliary
excretion of copper, occur in humans (Wilson's disease) and
certain breeds of dogs (Hyun and Filippich, 2004) that result
in elevated liver copper concentrations. Normal liver copper
concentrations in ruminants (100 to 400 mg Cu/kg DM) are
considerably higher than in pigs and chickens (Underwood,
1977). In fact, concentrations of copper normally found in
the liver of most nonruminants would be indicative of cop-
per deficiency in ruminants. Biliary copper excretion is much
less effective in regulating liver copper concentrations in
ruminants. This is especially true in sheep where increasing
dietary copper does not appear to increase biliary copper
excretion (Saylor and Leach, 1980).
Liver is the major storage organ for copper, and stored
copper is largely bound to metallothionein in most species
(Bremner, 1987). When high dietary copper is ingested,
binding to metallothionein appears to be an important cellu-
lar detoxification mechanism in some animal species
(Bremner, 1987). In sheep, a much smaller proportion of
liver copper is bound to metallothionein, and sheep have a
limited ability to increase metallothionein synthesis in re-
sponse to increased liver copper (Saylor et al., 1980).
Copper not excreted in bile, stored, or used for copper-
dependent enzymes in the liver leaves the liver largely bound
to ceruloplasmin, an oxidase and acute phase protein. In most
species (except birds), ceruloplasmin is the major form of
copper in plasma and is believed to be the major protein that
transports copper to extrahepatic tissues. Ceruloplasmin is
thought to recognize receptors on the plasma membrane of
tissues and to release copper into cells (Harris, 1997). Free
copper is highly toxic to cells; cytosolic proteins, referred to
as copper chaperones, bind copper ions and deliver them to
copper-requiring proteins without releasing free copper ions
(Pena et al., 1999). Tissue copper concentrations are highest
in the liver followed by the kidney and brain.
IVIetabolic Interactions and IVIechanisms of Toxicity
Interactions that occur among copper, sulfur, and molyb-
denum are extremely important in ruminant nutrition. Mo-
lybdenum in ruminant diets is frequently within the range of
1 to 5 mg Mo/kg DM, while total sulfur usually varies from
0.1 to 0.3 percent. Concentrations of molybdenum and sul-
fur on the upper end of this range greatly reduce copper
bioavailability and increase the risk of copper deficiency. In
contrast, low dietary concentrations of molybdenum and sul-
fur increase the risk of copper toxicosis, especially in sheep.
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136
MINERAL TOLERANCE OF ANIMALS
Sulfide, derived from sulfate reduction and degradation
of sulfur amino acids by ruminal microorganisms, is believed
to reduce copper absorption via formation of insoluble cop-
per sulfide (Suttle, 1991). Increasing dietary sulfur from 0.1
to 0.4 percent reduced copper bioavailability by 30 to 56
percent in hypocupremic sheep fed low molybdenum diets
(Suttle, 1974). Sulfide can also interact with molybdate in
the rumen to form various thiomolybdates (Suttle, 1991).
Tri-and tetrathiomolybdates reduce copper absorption by
forming insoluble complexes with copper that do not release
copper even under acidic conditions. When dietary sulfur
and molybdenum are high, di- and trithiomolybdates can be
absorbed and affect systemic metabolism of copper
(Gooneratne et al., 1989). Systemic effects on copper me-
tabolism attributed to thiomolybdates include (1) increased
biliary excretion of copper from liver stores; (2) removal of
copper from metalloenzymes; and (3) strong binding of cop-
per to plasma albumin, which results in reduced transport of
available copper for biochemical processes. Molybdenum
and sulfur supplementation have been used to prevent and
treat copper toxicosis in sheep (Howell and Gooneratne,
1987). Intravenous administration of ammonium
tetrathiomolybdate has effectively been used to treat copper
toxicosis in sheep (Howell and Gooneratne, 1987).
In nonruminants, interactions between copper and mo-
lybdenum are minimal and only occur at very high concen-
trations of molybdenum (Mills and Bremner, 1980). Copper
does interact with amino acids in nonruminants. Sulfur
amino acid requirements for maximal growth are higher in
chicks fed pharmacological levels of copper (Robbins and
Baker, 1980; Wang et al., 1987). Increasing the concentra-
tion of methionine or cysteine above dietary requirements
for growth alleviates the growth depression seen in chicks
fed excess copper (500 mg Cu/kg) (Jensen and Maurice,
1979; Robbins and Baker, 1980). Cysteine supplementation
reduced liver copper concentrations in chicks fed high di-
etary copper (Persia et al., 2003) and may chelate copper and
reduce its absorption (Baker and Czarnecki-Maulden, 1987).
A number of studies indicate that high dietary zinc can
reduce copper absorption (WHO, 1998). High doses of zinc
are effective in reducing copper absorption in patients with
Wilson's disease. High dietary zinc (220 or 420 mg Zn/kg
DM) was effective in preventing copper toxicosis by reduc-
ing liver copper accumulation in lambs fed high copper diets
(Bremner et al., 1976). High dietary iron can reduce copper
absorption in nonruminants (Yu et al., 1994) and reduces
copper status in cattle and sheep (Spears, 2003).
The mechanism of chronic copper toxicity appears to re-
late to ionic copper producing oxidative damage to tissues.
Copper can shift between an oxidized (Cu+-) and reduced
state (Cu"*"') in the cell, which allows copper to bind strongly
to many types of electron-rich structures (WHO, 1998). Nor-
mally, free copper in the cell is maintained at low concentra-
tions by copper-binding compounds such as metallothionein,
glutathione, and copper chaperone proteins (Viarengo et al..
2002). However, when the copper concentration in the cell
overwhelms metal homeostasis, free copper can alter cellu-
lar functions by directly binding to proteins and nucleic ac-
ids and by formation of reactive oxygen species. Ionic cop-
per readily participates in the Fenton reaction that results in
the production of reactive oxygen species, including the hy-
droxyl radical (Viarengo et al., 2002). Hydroxyl radicals can
cause lipid peroxidation in cell membranes, cleavage of
nucleic acids, and oxidation of cellular proteins.
Acute copper toxicosis in several species, including hu-
mans, results in nausea and vomiting. It is believed that the
mechanism responsible for these signs is due to copper ions
stimulating receptors that, in turn, stimulate the vagus nerve,
eliciting a reflex response of nausea and vomiting (Araya et
al., 2002).
SOURCES AND BIOAVAILABILITY
Copper is found naturally in the Earth's crust at an aver-
age concentration of 50 mg/kg (ATSDR, 2002). Seawater
contains approximately 0.15 [Jg Cu/L, and fresh water con-
tains 1.0 to 20 |Jg Cu/L in uncontaminated areas (WHO,
1998). Natural weathering of soil and discharges from in-
dustries and sewage treatment plants can result in copper
release into water. Copper compounds are also sometimes
applied to water to kill algae. Copper released into water is
primarily in particulate form and tends to settle out, precipi-
tate out, or be adsorbed by organic matter, hydrous iron,
manganese oxides, or clay in the sediment. This usually re-
sults in low concentrations of copper downstream from the
source of copper entry. The cuprous (H-1) ion is unstable in
aqueous solution and tends to disproportionate to the cupric
(h-2) form and copper metal unless a stabilizing ligand is
present (WHO, 1998). The only cuprous compounds stable
in water are insoluble ones such as cuprous sulfide. Cupric
copper forms coordination compounds or complexes with
inorganic and organic ligands. Bioavailability of copper in
water is generally low due to adsorption to suspended par-
ticles and complexation by dissolved organic matter or inor-
ganic ligands such as carbonate (WHO, 1998). Copper in
sediments also appears to be of poor bioavailability because
of its ability to react with acid volatile sulfides and form
insoluble precipitates (Besser et al., 1996).
Copper concentrations in various soil types in the United
States can vary from 1 to 700 mg/kg with an average con-
centration of 25 mg/kg (WHO, 1998). Soil copper concen-
trations are highest in areas in close proximity to copper
mining and smelting activities. Application of sludge, poul-
try or swine waste, and copper-containing fungicides can
increase soil copper concentrations. The majority of copper
deposited in soil will be strongly adsorbed and remain in the
upper few centimeters of soil (Georgopoulos et al., 2002).
Soil copper can adsorb to organic matter, clay minerals, car-
bonate minerals, or hydrous iron and manganese oxides.
Copper binds to soil more strongly than other divalent
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COPPER
137
cations (Georgopoulos et al., 2002). Because of the strong
adsorption and complexation of soil copper, elevated soil
copper often does not greatly increase copper uptake by
plants (Suttle and Price, 1976; Payne et al., 1988).
Forages generally contain 3 to 8 mg Cu/kg DM (Minson,
1990). Legumes are usually higher in copper than grasses
when grown under temperate conditions. Bioavailability of
copper from forages is low in ruminants and is greatly af-
fected by forage concentrations of sulfur, molybdenum, and
iron (Underwood and Suttle, 1999). Normal concentrations
of copper in cereal grains range from 3 to 8 mg Cu/kg DM,
while leguminous and oilseed meals range from 15 to 35
mg/kg DM. Relative to copper sulfate, copper bioavailability
from corn gluten meal, soybean meal, and cottonseed meal
was 48, 38, and 41 percent, respectively, in chicks (Aoyagi
et al., 1995). Feeds of animal origin with the exception of
liver products are low in copper. Liver is often used as an
ingredient in pet foods. Based on chick studies, using bile
copper excretion as a measure of bioavailability, copper in
pork liver was essentially unavailable (Aoyagi et al., 1993).
However, copper from chicken, turkey, beef, and sheep liver
was similar in bioavailability to copper sulfate (Aoyagi et
al., 1993).
Use of poultry or swine waste in diets or as pasture fertil-
izer can result in high intakes of copper by ruminants. Poul-
try and swine waste are high in copper, especially if waste is
obtained from animals fed growth stimulatory concentrations
of copper (100 to 250 mg/kg). Copper from swine and poul-
try waste is equal in bioavailability to copper sulfate when
fed to hypocupremic ewes (Suttle and Price, 1976). Applica-
tion of high copper waste to pasture (Suttle and Price, 1976)
or crop land (Payne et al., 1988) did not increase forage or
grain copper concentrations greatly. However, application
of waste to pastures can result in copper toxicosis due to
ingestion of forage contaminated with high copper waste.
Copper toxicosis has been reported in ruminants fed poultry
waste (Suttle et al., 1978; Tokarnia et al., 2000) or grazing
pastures where large amounts of waste have been applied
(Sargison and Scott, 1996). However, other studies have
shown no ill effects from grazing sheep on pasture fertilized
with high-copper pig manure (Prince et al., 1975). In addi-
tion, in some studies chicks and sheep have been fed high-
copper pig manure directly with no ill effects, apparently
because the copper in the manure was poorly bioavailable to
the chickens and sheep (Prince et al., 1975; Izquierdo and
Baker, 1986).
Another potential source of copper in ruminants is copper
used in foot baths. Copper sulfate foot baths are used in ru-
minants to control foot rot and other lameness-related prob-
lems. Ingestion of copper from baths or consumption of pas-
ture where the copper sulfate solution has been disposed of
can lead to copper toxicosis. Copper has been used as an
anthelmintic to control gastrointestinal parasites in ruminants
(Bang et al., 1990). For example, high doses of copper (3 to
4 g) from copper oxide needles have been administrated to
sheep (Bang et al., 1990) and goats (Chartier et al., 2000) to
control parasite loads.
A major source of copper in animal diets is supplemental
copper added to diets or free choice mineral supplements.
Errors in copper formulation or excess supplementation with
copper can result in toxicosis. Sources of copper supple-
mented to animal diets include cupric sulfate, tribasic cupric
chloride, copper oxide (primarily cupric oxide), cupric car-
bonate, and various organic copper sources. Copper from
copper oxide powder is essentially unavailable when fed to
cattle (Kegley and Spears, 1994), hens (Jackson and
Stevenson, 1981), chicks (Baker et al., 1991), and swine
(Cromwell et al., 1989). Copper oxide needles supply avail-
able copper in ruminants because the needles are retained in
the digestive tract and release copper over several weeks.
Apparently, copper oxide powder passes through the acid
environment of the digestive tract before the copper can be
solubilized (Spears, 2003). Tribasic cupric chloride is simi-
lar in bioavailability to cupric sulfate in chicks (Miles et al.,
1998) and swine (Cromwell et al., 1998) and in cattle fed
diets low in molybdenum and sulfur (Spears et al., 2004).
Relative to cupric sulfate (set at 100 percent), tribasic cupric
chloride is more bioavailable (132 to 196 percent) when
supplemented to diets high in molybdenum and sulfur
(Spears et al., 2004). Feed grade cupric carbonate appears to
be somewhat less bioavailable, based on liver copper con-
centrations, than cupric sulfate (Ledoux et al . , 1991; Ward et
al., 1996). Results of studies evaluating the bioavailability
of copper from different organic sources have been variable,
with some studies indicating similar bioavailability and oth-
ers higher bioavailability relative to cupric sulfate (Spears,
2003).
In field studies with fish, the bioconcentration factor for
copper was 10 to 100, indicating a low potential for
bioconcentration (ATSDR, 2002). Biomagnification of cop-
per also does not occur in the food chain.
TOXICOSIS
A number of excellent reviews are available on copper
toxicosis in mammals and fish (Howell and Gooneratne,
1987; Bremner, 1998; WHO, 1998; ATSDR, 2002;
Clearwater et al., 2002). Copper toxicosis can result from a
single large dose of copper or from repeated exposure to
copper concentrations that exceed animal requirements. A
number of studies evaluating oral ingestion of high concen-
trations of copper are summarized in Table 13-1.
Animal species differ greatly in their ability to tolerate
excess copper. Sheep are very sensitive to copper toxicity.
Death due to copper toxicosis is a common problem in sheep.
The range of dietary copper concentrations required by sheep
under some conditions can overlap with dietary concentrations
that cause toxicosis under other conditions. For example,
10 mg Cu/kg diet may be required by sheep if dietary sulfur
and molybdenum are fairly high. However, if dietary
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138
MINERAL TOLERANCE OF ANIMALS
molybdenum is low, 10 mg Cu/kg diet can cause toxicosis in
some breeds of sheep (Hogan et al., 1968). The sensitivity of
sheep to copper toxicity appears to relate to their inability to
increase biliary copper excretion in response to elevated copper
intakes (Bremner, 1998). Cattle and goats are less suscep-
tible to copper toxicity than sheep. Young ruminants are
more susceptible than adults because of higher absorption.
In nonruminants, copper homeostatic control mechanisms
generally are very efficient in preventing toxicosis. Concen-
trations of copper needed to cause toxicosis in nonruminants
generally exceed requirements by at least 25 -fold, and are as
high as 50-fold in pigs. Rats can tolerate higher dietary con-
centrations of copper than swine and poultry, and mice are
less sensitive than rats to copper toxicity (Hebert et al.,
1993). Most fish can tolerate fairly high concentrations of
dietborne copper (Clearwater et al., 2002). However, some
fish species are sensitive to relatively low concentrations of
copper in water (Taylor et al., 1996).
Liver and kidney are target organs for copper toxicosis in
all species. Lesions in the forestomach also occur in rats and
mice (Hebert et al., 1993), and proventriculitis (Wideman et
al., 1996) and gizzard erosion (Jensen and Maurice, 1978)
are seen in poultry exposed to high dietary copper.
Single Dose and Acute
Acute copper toxicosis signs include nausea, vomiting,
diarrhea, excessive salivation, abdominal pain, convulsions,
paralysis, and sometimes death (NRC, 1980; WHO, 1998).
Necropsy of animals with acute copper toxicosis reveals
acute gastroenteritis, necrotic hepatitis, and splenic and re-
nal congestion. The acute toxic level of oral copper (as
CUSO4) is 9 to 20 mg/kg BW in sheep and approximately
200 mg/kg BW in cattle (NRC, 1980). Administration of
copper oxide wire or needles at a rate of 4.1 g Cu/head to
sheep (Bang et al., 1990) or 3.4 g Cu/head to goats (Chartier
et al., 2000) did not produce toxicosis. Copper oxide needles
release copper slowly in the gastrointestinal tract and appear
to be relatively safe when administered at the labeled dosage
to ruminants with a functional rumen. However, administra-
tion of copper oxide needles to young calves has resulted in
mortality from copper toxicosis (Hamar et al., 1997; Steffen
et al., 1997). In horses, a single oral dose of 125 mg CUSO4
(in solution)/kg BW resulted in gastroenteritis, hemolysis,
kidney and liver damage, and death within 2 weeks (Hintz,
1987). Acute toxicosis did not occur when the same amount
of copper was added to the feed of horses. The LD^q in rats
for copper as CUSO4 has ranged from 120 to 244 mg Cu/kg
BW in different studies (WHO, 1998).
The 96-hr LCjq for Chinook salmon was 54-64 |ig Cu/L
of water (Hamilton and Buhl, 1990). In channel catfish, the
24-hr LC5Q was 2,500 to 3,500 pg/L depending on water tem-
perature (Smith and Heath, 1979). In rainbow trout, the 96-hr
LCjQ ranged from 20 |Jg Cu/L in soft acid water to 520 |-ig/L
in hard alkaline water (Howarth and Sprague, 1978).
Chronic
Chronic copper toxicosis in sheep is characterized by the
gradual accumulation of copper in the liver over a period of
several weeks or months. The condition is most common in
lambs fed large amounts of concentrate feeds, but can occur
under grazing conditions if forage molybdenum concentration
is low or if sheep are consuming plants that contain hepato-
toxic compounds (Underwood and Suttle, 1999). Copper
toxicosis in sheep consists of a prehemolytic, and hemolytic
phase (Howell and Gooneratne, 1987). Although copper is
accumulating in the liver and to a lesser extent in the kidney
during the prehemolytic phase, the animal is clinically normal,
and depressed animal performance is generally not evident
until at least shortly before the hemolytic phase occurs. Dur-
ing the prehemolytic phase, liver necrosis occurs and enzymes
(aspartate aminotransferase, glutamate dehydrogenase, and
sorbitol dehydrogenase) indicative of liver damage may be-
come elevated in serum, but blood copper is generally nor-
mal (Howell and Gooneratne, 1987). Liver concentrations of
copper in all cellular fractions are increased, but the propor-
tion of cellular copper in the nuclear fraction is increased
during copper loading (Gooneratne et al., 1979).
Sheep show histological and biochemical evidence of
liver damage at liver copper concentrations as low as 350
mg Cu/kg DM; however, clinical signs of toxicosis do not
usually occur until liver concentrations of 1,000 mg Cu/kg
DM or higher are reached (Underwood and Suttle, 1999).
Animals that die from copper toxicosis often have liver con-
centrations that exceed 2,000 mg Cu/kg DM. The hemolytic
phase (referred to as hemolytic crisis) is associated with rapid
release of copper from the liver into the blood and is charac-
terized by hemolysis, hemoglobinemia, and hemoglobinuria.
Clinical signs may include dullness, anorexia, excessive
thirst, jaundice of mucous membranes, dark-colored urine,
sunken eyes with blood vessels on the surface of the sclera
showing a chocolate-brown color, and death (Howell and
Gooneratne, 1987). Observed hemolysis is due to entry of
excessive copper into erythrocytes. The mechanism whereby
copper induces hemolysis is unclear, but may be due to cop-
per inducing production of superoxide radicals that cause
erythrocyte membrane damage (Howell and Gooneratne,
1987). Sheep with a mild hemolysis may survive and re-
cover, especially if treated with copper chelating agents such
as ammonium tetrathiomolybdate or penicillamine that in-
crease copper excretion.
Sheep that are killed during the hemolytic phase or those
that die from toxicosis show major liver and kidney damage
(Howell and Gooneratne, 1987). Livers contain areas of ne-
crotic parenchymal cells and swollen copper-containing
Kupffer cells high in acid phosphatase. Kidney copper is
greatly elevated following the hemolytic phase. The elevated
copper causes necrosis in the proximal convoluted tubules and
impaired glomerular and tubular function. In addition, kid-
neys have a characteristic black or dark brown color.
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COPPER
139
The concentration of dietary copper needed to cause toxi-
cosis in siieep lias varied greatly among studies (Table 13-1)
and is greatly affected by genetics and dietary factors that will
be discussed in the next section. In several studies (Hill and
Williams, 1965; Pond, 1989; Zervas et al., 1990) feeding total
(diet plus supplemental) dietary copper concentrations of 30
to 40 mg/kg DM resulted in some mortality from toxicosis.
Death losses occurred after 3 to 12 weeks of feeding the high
copper diets. Elevated plasma aspartate aminotransferase ac-
tivity was observed in some lamb breeds fed a total dietary
copper concentration of 20 mg/kg DM for 9 weeks
(Woolliams et al., 1982). Long-term studies have indicated
that copper toxicosis can occur in housed sheep fed diets con-
taining approximately 10 mg Cu/kg (Hogan et al., 1968) and
in ewes grazing forage containing 7.5 to 15.0 mg Cu/kg DM
(MacPherson et al., 1997) if dietary molybdenum is low.
Cattle can tolerate higher dietary concentrations of cop-
per than sheep. However, some breeds of cattle may be more
susceptible to copper toxicosis than others. Clinical signs of
copper toxicosis in cattle are similar to those described for
sheep. The preruminant calf is more susceptible to copper
toxicosis than older cattle during relatively short-term cop-
per exposure. Clinical cases of copper toxicosis occurred in
10- to 12-week-old calves fed milk replacer containing 115
mg Cu/kg DM (Shand and Lewis, 1957). In calves (Holstein
and Ayrshire-Holstein crossbreds), supplementation of milk
replacer with 50 mg Cu/kg DM for 6 weeks reduced intake
(Jenkins and Hidiroglou, 1989). Copper addition to milk re-
placer at 200 mg/kg DM reduced gain and intake while 1,000
mg Cu/kg DM resulted in a 43 percent mortality in calves
(Jenkins and Hidiroglou, 1989).
Older cattle (Bonsmara) receiving 10 or 20 mg Cu/kg
BW, in an oral drench, for 5 days per week showed clinical
signs of copper toxicosis by day 679 after initial dosing
(Gummow, 1996). However, liver damage occurred much
sooner based on elevated serum asparate aminotransferase
activity. A number of factors may influence the ability of
older cattle to tolerate copper. In some studies (Chapman et
al., 1962; Felsman et al., 1973), cattle have tolerated high
doses of copper without showing signs of toxicosis, and un-
der certain conditions (that are not well defined) cattle ap-
pear to regulate liver copper concentrations once concentra-
tions reach a certain level. Steers (Hereford x Brahman)
dosed daily with 0.13 to 2.0 g Cu/d, via gelatin capsule, for
16 months showed no clinical signs of toxicosis (Chapman
et al., 1962). Liver copper concentrations increased during
the study, but final liver copper concentrations were approxi-
mately 2,000 mg/kg DM regardless of the quantity of copper
dosed. Steers (Hereford) administered 3 g Cu/d, via a gelatin
capsule, also did not show adverse effects by 64 days; how-
ever, this quantity of copper given in water resulted in clini-
cal signs of copper toxicosis, including death, and much
higher liver copper concentrations (Chapman et al., 1962).
No signs of copper toxicosis were observed in weaned Hol-
stein calves fed a high concentrate diet supplemented with
125 to 900 mg Cu/kg DM for 98 days (Felsman et al., 1973).
Liver copper concentrations at the end of the study in cop-
per-supplemented calves were approximately 900 mg/kg
DM, regardless of dietary copper (Felsman et al., 1973).
Long-term supplementation of lower dietary copper con-
centrations than those described above can cause toxicosis
in cattle. Bradley (1993) reported the death of 9 of 63 Hol-
stein cows in a herd from copper toxicosis. For over two
years, the cows received a diet that analyzed 37.5 mg Cu/kg
DM during lactation and 22.6 mg Cu/kg DM during the dry
period. Cows exhibited clinical signs of copper toxicosis
prior to death and had elevated postmortem liver copper con-
centrations that ranged from 1,236 to 2,179 mg/kg DM. All
cows that died were in late pregnancy. The addition of am-
monium molybdate to the diet for 18 days and removal of
the copper-containing mineral supplement arrested the out-
break of copper toxicosis (Bradley, 1993). Lactating dairy
cows (Holstein) tolerated 40 (Engle et al., 2001) or 80 mg
(Du et al., 1996) supplemental Cu/kg DM for 60 days. How-
ever, over the 60-day periods, liver copper concentrations
increased by over 7 mg Cu/kg DM/day in both studies. If
this rate of increase in liver copper had continued, cows may
have eventually showed signs of copper toxicosis.
Goats can also tolerate much higher dietary copper con-
centrations than sheep. Zervas et al. (1990) compared the
susceptibility of lambs and goats to chronic copper toxico-
sis. Lambs supplemented with 30 or 60 mg Cu/kg DM had
elevated serum asparate aminotransferase after 50 days, and
some lambs died from copper toxicosis beginning as early as
67 days. Goats fed the same diets (30 or 60 mg Cu/kg) had
normal serum asparate aminotransferase activity and exhib-
ited no signs of toxicosis during the 137-day study. Lambs
stored 6 to 9 times more copper in their livers than goats.
Goats fed a total dietary copper of 36 mg/kg DM for 88 days
had increased liver copper but no signs of toxicosis or liver
damage (Luginbuhl et al., 2000). Goats administered 600
mg Cu/d (gelatin capsule) for 4 weeks showed clinical signs
of toxicosis and one of two goats receiving 1,200 mg Cu/d
died (Solaiman et al., 2001).
Copper is relatively nontoxic to nonruminant animals.
Supplementation of swine diets with 250 mg Cu/kg diet in-
creased liver copper concentration, but generally has produced
no negative effects on animal growth or health. In fact, 250
mg/kg of added copper normally stimulates growth rates of
weanling pigs (Hill et al., 2000). Addition of 250 mg Cu/kg to
sow diets for up to 775 days had no adverse effects on animal
health and actually increased piglet birth and weaning weights
(Cromwell et al., 1993). In growing pigs, 500 mg Cu/kg diet
has reduced growth and hemoglobin concentrations (Bunch et
al., 1965; Kline et al., 1971) and resulted in increased mortal-
ity in one study (DeGoey et al., 1971).
Poultry are similar to swine in their ability to tolerate ex-
cess dietary copper. In long-term studies with laying hens,
400 mg Cu/kg diet or higher reduced feed intake and egg
production, and increased gizzard weight (Jackson et al..
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MINERAL TOLERANCE OF ANIMALS
1979; Jackson and Stevenson, 1981). Some studies with
broilers have indicated that supplementation with 250 mg
Cu/kg diet can cause slight gizzard lining erosion (Robbins
and Baker, 1980), proventriculitis (Wideman et al., 1996),
and lesions in the oral cavity, tongue, and pharynx (Chiou et
al., 1999). In other studies, no adverse effects were noted in
broilers supplemented with 375 (Pesti and Bakalli, 1996) or
450 (Ledoux et al., 1991) mg Cu/kg diet. Supplementation
with 500 mg Cu/kg diet reduced body weights and feed in-
take, and caused gizzard erosion in turkey poults (Christmas
and Harms, 1979). In older turkeys, addition of up to 500 mg
Cu/kg diet did not affect performance (Leeson et al., 1997).
Ducklings accumulated more copper in their livers than
chicks when fed high dietary copper concentrations (Wood
and Worden, 1973) and thus, may be more sensitive to cop-
per toxicosis. Addition of 500 mg Cu/kg to duckling diets
caused myopathy characteristic of selenium-vitamin E defi-
ciency (Van VIeet, 1982). High mortality and severe necro-
sis in the gizzard, skeletal muscle, and intestine were ob-
served in ducklings fed 1,000 mg Cu/kg diet.
Horses and rabbits appear to be more resistant to copper
toxicosis than swine or poultry. Ponies fed diets containing
up to 79 1 mg Cu/kg for 6 months showed no signs of toxico-
sis, including liver damage despite final liver copper con-
centrations over 3,000 mg/kg DM (Smith et al., 1975). Some
of the ponies were pregnant during the study and foaled nor-
mally 3 to 4 months after the study ended. Rabbits can toler-
ate 500 mg Cu/kg diet for up to 32 days without adverse
effects (Patton et al., 1982; Grobner et al., 1986). In some
studies, high dietary copper has increased gain and reduced
mortality from enteritis in rabbits (Patton et al., 1982). Addi-
tion of 1,000 mg Cu/kg diet reduced gain, feed intake, and
feed efficiency in rabbits (Grobner et al., 1986).
Rats are very tolerant to dietary copper. Diets supple-
mented with 1,000 mg Cu/kg produced no adverse effects in
rats (Hebert et al., 1993; Aburto et al., 2001a). Aburto et al.
(2001a) reported reduced body weight and slight liver dam-
age in rats fed 1,250 mg Cu/kg diet for 3 months, and more
extensive liver damage in animals fed 1,500 mg Cu/kg. Rats
fed 2,000 to 8,000 mg Cu/kg diet for 13 weeks exhibited
hyperplasia and hyperkeratosis of the squamous mucosa on
the limiting ridge separating the forestomach from the glan-
dular stomach, inflammation in the liver, with indications of
cellular damage, and an increase in the size and number or
cytoplasmic protein droplets present in the epithelium of the
proximal convoluted tubules of kidney (Hebert et al., 1993).
Severity of stomach, liver, and kidney lesions increased with
increasing dietary copper. Some research indicates that rats
are able to adapt to prolonged exposure to high copper, with
elevated liver and kidney concentrations eventually decreas-
ing, with subsequent recovery from copper-induced liver and
kidney damage (Haywood, 1985; Fuentealba et al., 1993).
Mice are even less sensitive to copper than rats (Hebert et
al., 1993). Chronic copper toxicosis did not affect reproduc-
tion in either rats or mice (Hebert et al., 1993).
Copper toxicosis resulting from a genetic disorder in cop-
per metabolism is a problem in certain breeds of dogs, espe-
cially in Bedlington terriers (Hyun and Filippich, 2004).
Dogs with this disorder absorb normal amounts of copper,
but biliary excretion of copper is reduced. Progressive accu-
mulation of copper within hepatic lysosomes results in liver
damage that can be fatal. Occurrence of a hemolytic crisis is
uncommon in dogs with inherited copper toxicosis, but can
be seen in the terminal stages. Once diagnosed, inherited
copper toxicosis is treated by restricting copper intake, add-
ing an antagonist, such as zinc, to the diet to reduce copper
absorption and/or use of chelators that increase urinary cop-
per excretion (Hyun and Filippich, 2004). Limited research
has examined the level of copper needed to cause toxicosis
in normal dogs. During a 12-month study, 2 of 12 Beagle
dogs fed 8.4 mg Cu/kg BW developed elevated serum
alanine aminotransferase (WHO, 1998).
The amount of dietborne copper needed to cause toxicosis
differs among fish species (Clearwater et al., 2002). Channel
catfish may be most sensitive to dietary copper. Mural et al.
(1981)found thatonly 8mg Cu/kg diet reduced gain:feed, and
that 16 to 32 mg Cu/kg diet reduced gain and gain:feed during
a 16-week study with catfish. In contrast, Gatlin and Wilson
(1986) reported that copper concentrations up to 40 mg/kg
diet caused no adverse effects in channel catfish during a 13-
week study. In Atlantic salmon fry, copper concentrations of
500 to 1,750 mg/kg diet reduced weight gain (Berntssen et al.,
1999). Atlantic salmon parr are more sensitive to lower di-
etary concentrations of copper than fry (Clearwater et al.,
2002). Lanno et al. (1985) concluded that 665 mg Cu/kg diet
was the maximum tolerable level in rainbow trout fry, when
copper was supplied from CUSO4. Reduced gain and increased
feed:gain were observed in trout fed diets containing 730 mg/
kg and increased mortality occurred when diets supplied 1 ,5 85
to 3,088 mg Cu/kg (Lanno et al., 1985). Dietary copper con-
centrations as low as 660 mg/kg increased mortality in rain-
bow trout fry when supplemental copper was provided from
shrimp, enriched with copper (Mount et al., 1994). Water-
borne copper released from shrimp may have contributed to
the higher toxicosis of copper in this study (Mount et al., 1994).
Rainbow trout exposed to water containing 144 |ig Cu/L for
12 weeks had reduced growth and increased mortality when
fed high carbohydrate diets and maintained at 10°C (Dixon
and Hilton, 1985). This concentration of copper in water had
no effect when fish were fed low carbohydrate diets and/or
maintained at a water temperature of 15°C.
Factors Influencing Toxicity
A number of dietary, physiological, and genetic factors
affect the occurrence of copper toxicosis, especially in rumi-
nants. Length of exposure will affect copper toxicity because
copper generally accumulates in the liver over time when
animals are fed high dietary copper. In ruminants, young
animals are more susceptible to copper toxicosis than older
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COPPER
141
animals during relatively short-term exposure periods (Todd,
1969).
Molybdenum and sulfur are potent copper antagonists that
greatly affect the level of copper needed to cause toxicosis in
ruminants. Addition of 0.2 percent sulfur and 2 to 16 mg
Mo/kg diet reduced liver copper and liver damage in sheep
fed a high copper diet (45 mg Cu/kg) for 18 weeks (Suttle,
1977). In sheep previously exposed to high dietary copper,
supplementation with 0.3 percent sulfur and 14 or 30 mg
Mo/day reduced liver copper concentrations by 34 to 47 per-
cent over a 79-day period (Van Ryssen, 1994). Deaths from
outbreaks of copper toxicosis can also be alleviated by
supplementation of molybdenum and sulfur (Hidiroglou et
al., 1984). However, sheep consuming diets low in molyb-
denum and sulfur are susceptible to toxicosis at relatively
low (10 to 14 mg/kg) dietary copper concentrations. High
dietary sulfur intake via feed or water will reduce copper
toxicity even if dietary molybdenum is low. Consumption of
high sulfate (1,500 mg SO4/L) water versus normal water
greatly reduced liver copper accumulation in cattle fed 100
mg Cu/kg diet (Wright et al., 2000).
Dietary iron and zinc can also influence copper toxicity.
High dietary zinc can reduce liver copper and clinical signs
of copper toxicosis. In lambs fed diets containing 29 mg Cu/kg,
increasing dietary zinc from 43 to 220 or 420 mg/kg reduced
liver copper concentrations and liver damage, and prevented
onset of a hemolytic crisis (Bremner et al., 1976). Providing
high dietary zinc to sheep that had previously been loaded
with copper was ineffective in reducing liver copper concen-
trations over an 88-day period (Van Ryssen, 1994). How-
ever, administration of 200 mg Zn/day for 2 years to dogs
(Bedlington terriers and West Highland White terriers) with
inherited copper toxicosis reduced liver copper concentra-
tions and liver damage (Brewer et al., 1992).
Factors that reduce or eliminate ruminal protozoa increase
copper bioavailability and, thus, increase the susceptibility
of ruminants to chronic copper toxicosis (Ivan et al., 1986).
Liver copper concentrations increased to a much greater ex-
tent in fauna-free than in faunated sheep when diets contain-
ing 13 mg Cu/kg were fed (Ivan et al., 1986). Lower copper
bioavailability in sheep with ruminal protozoa may relate to
the role of protozoa in degradation of dietary protein. In-
creased degradation of dietary protein by ruminal microor-
ganisms increases ruminal sulfide, which subsequently can
reduce copper absorption. Feeding monensin, a carboxylic
ionophore, increased liver copper in sheep (Van Ryssen and
Barrowman, 1987; Ivan et al., 1992). Higher liver copper in
sheep fed monensin may relate to the ability of the iono-
phore to reduce ruminal protozoa numbers.
Plants containing toxins that compromise liver function
decrease tolerance for copper in ruminants. Plants belonging
to the Heliotropium echium and Senecio genera contain
pyrrolizidine alkaloids that cause liver damage. Concurrent
exposure to high copper and Heliotropium europaeum in
sheep enhanced the toxicity of both substances and caused
greater accumulation of copper in liver than high copper
alone (Howell et al. 1991). Mycotoxins that cause liver dam-
age can also increase liver copper concentrations and may
lower the level of copper needed to produce toxicosis (White
et al., 1994).
High dietary copper may increase the requirement for
certain antioxidants because of its ability to cause oxidative
damage. Addition of 2 mg Se/kg or 200 lU vitamin E/kg to
diets adequate in these nutrients prevented mortality and
muscle necrosis in ducklings fed 1,500 mg Cu/kg diet (Van
Vleet et al., 1981). Dietary selenium did not affect hepatic
damage in rats fed 2,000 mg Cu/kg diet (Aburto et al.,
2001b). Ascorbic acid supplementation reduced liver copper
accumulation, but did not alleviate the growth depression
observed in chicks fed 1,000 mg Cu/kg diet (Persia et al.,
2003).
Copper toxicosis in poultry is affected by dietary sulfur
amino acid level. Addition of 0.4 percent methionine or 0.33
percent L-cysteine to diets adequate in sulfur amino acids
prevented growth depression and reduced liver copper in
chicks fed 500 mg Cu/kg diet (Jensen and Maurice, 1979).
Cysteine supplementation at 0.5 percent also alleviated
growth depression and reduced elevated liver copper con-
centrations in chicks receiving 1,000 mg Cu/kg diet (Persia
et al., 2003). In turkey poults, addition of 0.4 percent me-
thionine partially prevented growth depression and gizzard
erosion seen in birds fed 500 or 750 mg Cu/kg diet (Christ-
mas and Harms, 1979).
Susceptibility to copper toxicosis, especially in sheep and
dogs, is greatly affected by genetics. Breeds of sheep differ
in their ability to accumulate copper in their livers when fed
low (Littledike and Young, 1993; Suttle et al., 2002) or mod-
erate to high (Woolliams et al., 1982) copper levels. When
fed moderately high dietary copper, Texel-sired lambs were
most susceptible to copper toxicosis followed by Suffolk
lambs (Woolliams et al., 1982). Finnish landrace were inter-
mediate and Scottish Blackface appeared to be least suscep-
tible to copper toxicosis. In crossbred lambs fed diets low in
copper (4 to 5 mg/kg), Texel-sired lambs had the highest
liver copper followed by Dorset- and Montadale-sired lambs
with lambs from Finnsheep or Romanov rams being lowest
(Littledike and Young, 1993).
Genetic differences among breeds in copper metabolism
also occur in cattle. Simmental and Charolais cows and their
calves had lower plasma copper concentrations than Angus
when fed diets low in copper (Ward et al., 1995). Simmental
cattle also have lower liver copper concentrations than An-
gus (Mullis et al., 2003). Biliary copper excretion is higher
in Simmental compared to Angus (Gooneratne et al., 1994).
Copper accumulated more rapidly in the liver of Jerseys than
in Holsteins when copper was supplemented at 80 mg/kg
diet (Du et al., 1996). During an outbreak of copper toxicosis
in nursing beef calves, 32 percent of Angus calves were af-
fected, but only 5.5 percent of Charolais calves (Sargison
and Scott, 1996).
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142
MINERAL TOLERANCE OF ANIMALS
Liver copper concentrations vary greatly among and
witliin breeds in dogs (Thiornburg et al., 1990). Inherited
copper toxicosis affects approximately 70 percent of
Bedlington terriers in the United States (Hyun and Filippich,
2004). The condition is caused by an autosomal recessive
trait that reduces biliary excretion of copper. Inherited cop-
per toxicosis has also been seen in Doberman pinschers.
West Highland White terriers, Skye terriers, Dalmatians, and
in some mixed breeds (Hyun and Filippich, 2004).
Acute toxicity of waterborne copper in fish is affected by
water hardness, pH, and temperature (WHO, 1998). The 96-hr
LCjQ for rainbow trout increased with increasing water hard-
ness and was higher at alkaline pH (Howarth and Sprague,
1978). The effect of water temperature varies depending on
fish species (Smith and Heath, 1979).
TISSUE LEVELS
Representative copper concentrations in tissues from vari-
ous animals fed normal or high levels of copper are shown in
Table 13-2. Copper concentrations are highest in the liver,
and liver copper increases in animals fed high dietary cop-
per. Normal liver copper concentrations are higher in rumi-
nants than in pigs and chickens, and relatively small amounts
of dietary copper greatly increase liver copper concentra-
tions in ruminants. In nonruminants and fish, liver copper
increases to a much smaller extent with increasing dietary
copper unless high levels of copper (>100 mg Cu/kg) are
fed. Kidney copper concentrations also can increase in ani-
mals fed high dietary copper, but to a lesser extent than liver.
Muscle contains less than 4 mg Cu/kg DM in most animals
and does not increase in animals fed high copper diets. Cop-
per concentration in eggs is also not affected by level of
copper in diets of laying hens. The copper content of milk is
low and varies with species and stage of lactation
(Underwood, 1977). Copper addition to diets already ad-
equate in copper has little effect on milk copper concentra-
tion in cows (Underwood, 1977).
MAXIMUM TOLERABLE LEVELS
The maximum tolerable level for copper is defined as the
dietary level that, when fed for a defined period of time, will
not impair animal health and/or performance. Nonruminant
animals are tolerant to high dietary copper concentrations rela-
tive to copper requirements. Based on published literature in
nonruminants, maximum tolerable levels for copper in mg
Cu/kg diet were set by the NRC committee at chicken and
turkey, 250; duck, 100; swine, 250; horse, 250; rabbit, 500;
rat, 1,000; and mouse, 2,000. Insufficient data are available
to set a maximum tolerable level for copper for dogs and cats.
In broilers, addition of 250 mg Cu/kg to diets may in-
crease the incidence of proventriculitis (Wideman et al.,
1996) and lesions in the oral cavity, tongue, and pharynx
(Chiou et al., 1999), but negative effects on performance are
generally not observed. Ponies tolerated up to 791 mg Cu/kg
diet for 6 months without showing clinical signs of toxicosis
(Smith et al., 1975). However, liver copper concentrations
were elevated to concentrations that could cause toxicosis
problems in stressful situations that affect liver function.
Because of the limited research data, and possible genetic
differences in susceptibility to copper toxicity, a maximum
tolerable level of 250 mg Cu/kg is recommended in horses.
The maximum tolerable level of dietborne copper for fish
is affected by species and fish size or life stage (Clearwater
et al., 2002). The upper limit for copper intake from diets in
Atlantic salmon and rainbow trout is approximately 100 and
500 mg/kg diet, respectively. The maximum tolerable cop-
per level may be lower for channel catfish, but sufficient
data are not available to arrive at a reliable upper limit.
Waterborne copper is generally more toxic to fish than
dietborne copper. However, it is impossible to set a maxi-
mum tolerable water copper concentration for fish because
of the major impact of water hardness and pH on copper
toxicity from water.
In sheep, the maximum tolerable level was set at 15 mg
Cu/kg diet DM. Some sheep breeds may be susceptible to
copper toxicosis at lower dietary concentrations if dietary
molybdenum and/or sulfur are below normal levels (1 to 2
mg Mo/kg diet; 0.15 to 0.25 percent S) (Hogan et al., 1968;
MacPherson et al., 1997). This upper limit for copper is simi-
lar to the current European Commission (EC, 2003) limit of
17 mg Cu/kg DM in sheep diets. A recent study (Suttle et al.,
2002) suggested that the EC limit of 17 mg Cu/kg diet was
too high for some sheep breeds when fed high concentrate
diets (contained 0.27 percent sulfur and unspecified molyb-
denum concentration).
The level of dietary copper that causes toxicosis in rumi-
nants is greatly affected by dietary sulfur and molybdenum,
and genetics. Other factors that may affect the maximum
level of copper that ruminants can tolerate include: (1) length
of exposure, (2) age, (3) initial liver copper concentration at
the onset of high copper exposure, (4) dietary toxins that
impair liver function and trigger a hemolytic crisis, and
(5) dietary concentrations of zinc and iron. Maximum toler-
able copper levels for ruminants were set based on available
literature, and assuming normal dietary sulfur (0.15 to 0.25
percent DM) and molybdenum (1 to 2 mg/kg DM).
The maximum tolerable level for copper in cattle was set at
40 mg Cu/kg diet DM. Higher concentrations of copper can
often be tolerated by cattle for several weeks or even months.
However, long-term feeding of diets slightly less than 40 mg
Cu/kg can result in copper toxicosis (Bradley, 1993). Feeding
high dietary copper will greatly increase liver copper concen-
trations. Factors that regulate liver copper in cattle are poorly
understood, and the minimum liver copper concentration that
may result in clinical signs of toxicosis is not known. How-
ever, cattle not showing clinical signs of copper toxicosis, but
with high liver copper concentrations, would be expected to
be more susceptible to a hemolytic crisis when exposed to
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COPPER
143
toxins that cause liver damage or other stressors. Increased
incidence of copper toxicosis in cattle has been reported re-
cently by the Veterinary Laboratories Agency (VLA) in En-
gland (Bidewell et al., 2000; VLA, 2001). A few years ago a
considerable amount of the supplemental copper provided in
cattle supplements was in the form of copper oxide (primarily
cupric oxide) powder. Based on research indicating that
bioavailability of copper from copper oxide was extremely
low, more bioavailable sources of copper have now replaced
copper oxide in most ruminant supplements. Supplementation
of more bioavailable copper sources to cattle diets may have
contributed to increased incidence of copper toxicosis. Recent
studies with goats suggest that their tolerance to copper is simi-
lar to cattle.
HUMAN HEALTH
Copper in edible tissue is not likely to present a human
health concern, when copper is provided in animal diets at
the maximum tolerable levels indicated. Muscle copper is
low and increasing dietary copper does not increase muscle
copper concentration. Copper intake from animal products
could possibly be of concern in humans that consume large
quantities of liver. Livers from animals fed dietary copper
concentrations within the maximum tolerable levels sug-
gested can contain from approximately 20 to 900 mg Cu/kg
DM (Table 13-2).
FUTURE RESEARCH NEEDS
Maximum tolerable levels of copper are fairly well defined
for poultry and swine, and copper toxicosis is not a common
problem in these species. Copper toxicosis in ruminants is
primarily due to poor copper homeostasis, resulting in liver
copper accumulation. Research is needed to better understand
biliary copper excretion in ruminants and factors that affect it.
Under certain conditions, which are not well defined, cattle
appear to regulate liver copper concentrations once concen-
trations reach a certain level in spite of high copper intakes.
However, in other situations, liver copper continues to increase
until ruminants succumb to copper toxicosis. Additional re-
search is also needed to identify factors (dietary toxins, stress,
etc.) that may trigger the occurrence of hemolytic crisis, and
thus clinical signs of copper toxicosis in ruminants with el-
evated liver copper concentrations.
SUMMARY
Copper occurs primarily in the cuprous (+1) and cupric
(h-2) oxidation states. Because of its high electrical and ther-
mal conductivity, and resistance to corrosion, copper is a
widely used industrial metal. Copper compounds are also
used in nutritional supplements for animals, fungicides, and
as algicides in streams and reservoirs. Copper is an essential
trace mineral, and functions as a component of a number of
enzymes that are involved in maturation and stability of col-
lagen and elastin, energy metabolism, the antioxidant de-
fense system, and pigmentation, as well as other processes.
Homeostatic control mechanisms for copper are usually very
efficient in preventing copper toxicosis in nonruminants.
Concentrations of copper needed to cause toxicosis in
nonruminants exceed requirements by at least 25-fold. Ru-
minants, particularly sheep, are very susceptible to copper
toxicity. Copper requirements of sheep generally range from
3 to 8 mg Cu/kg diet DM, while 15 mg Cu/kg diet or even
less can cause toxicosis under certain conditions. Cattle and
goats can generally tolerate 40 mg Cu/kg diet DM for sev-
eral weeks or months. Maximum tolerable concentrations of
copper for ruminants are greatly affected by dietary concen-
trations of sulfur and molybdenum as well as dietary toxins
that compromise liver function. Susceptibility of sheep and
dogs to copper toxicity is greatly affected by genetics. Cer-
tain fish species are also quite susceptible to toxicosis from
waterborne copper. In all species, liver and kidney are the
major organs affected by copper toxicosis.
REFERENCES
Aburto, E. M., A. E. Cribb, C. Fuentealba, B. O. Ikede, F. S. B. Kibenge,
and F. Markliam. 2001a. Morphological and biochemical assessment of
the liver response to excess dietary copper in Fischer 344 rats. Can. J.
Vet. Res. 65:97-103.
Aburto, E. M., A. Cribb, I. C. Fuentealba, B. O. Ikede, F. S. B. Kibenge, and
F. Maridiam. 2001b. The failure of selenium supplementation to pre-
vent copper-induced liver damage in Fischer 344 rats. Can. J. Vet. Res.
65:104-110.
ATSDR (Agency for Toxic Substances and Disease Registry). 2002. Toxi-
cological profile for copper. Atlanta, GA: U.S. Department of Health
and Human Services, Public Health Service. Available at http://
www.atsdr.cdc.gov/toxprofiles/tpl32.html. Accessed March 23, 2005.
Aoyagi, S., D. H. Baker, and K. J. Wedekind. 1993. Estimates of copper
bioavailability from liver of different animal species and from feed in-
gredients derived from plants and animals. Poult. Sci. 72:1746-1755.
Aoyagi, S., K. M. Hiney, andD. H. Baker. 1995. Estimates of zinc and iron
bioavailability in pork liver and the effect of sex of pig on the
bioavailability of copper in pork liver fed to male and female chicks. J.
Anim. Sci. 73:793-798.
Araya, M., M. Gonzalez, M. Olivares, and R. Uauy. 2002. Biological ef-
fects of chronic copper exposure. Pp. 385-396 in Handbook of Copper
Pharmacology and Toxicology, E. J. Massaro, ed. Totowa, NJ: Humana
Press.
Baker, D. H., and G. L. Czarnecki-Maulden. 1987. Pharmacologic role of
cysteine in ameliorating or exacerbating mineral toxicities. J. Nutr.
117:1003-1010.
Baker, D. H., J. Odle, M. A. Funk, and T. M. Wieland. 199 1 . Bioavailability
of copper in cupric oxide, cuprous oxide, and in a copper-lysine com-
plex. Poult. Sci. 70{1):177-179.
Baker, R. T. M., R. D. Handy, S. J. Davies, and J. C. Snook. 1998. Chronic
dietary exposure to copper affects growth, tissue lipid peroxidation, and
metal composition of the grey mullet, Chelon labrosus. Mar. Environ.
Res. 45:357-365.
Bang, K. S., A. S. Familton, and A. R. Sykes. 1990. Effect of copper oxide
wire particle treatment on establishment of major gastrointestinal nema-
todes in lambs. Res. Vet. Sci. 49:132-137.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
144
MINERAL TOLERANCE OF ANIMALS
Berntssen, M. H. G., A. Lundebye, and A. Maage. 1999. Effects of elevated
dietary copper concentrations on growth, feed utilization and nutri-
tional status of Atlantic salmon (Salmo salar L.) fry. Aquaculture
174:167-181.
Besser, J. M., C. G. Ingersol, and J. P. Giesy. 1996. Effects of spatial and
femoral variation of acid- volatile sulfide on the bioavailability of copper
and zinc in freshwater sediments. Environ. Toxicol. Chem. 15:286-293.
Bidewell, C. A., G. P. David, and C. T. Livesey. 2000. Copper toxicity in
cattle. Vet. Rec. 147:399-400.
Bradley, C. H. 1993. Copper poisoning in a dairy herd fed a mineral supple-
ment. Can. Vet. J. 34:287-292.
Bradley, B. D., G. Graber, R. J. Condon, and L. T. Frobish. 1983. Effects of
graded levels of dietary copper on copper and iron concentrations in
swine tissues. J. Anim. Sci. 56:625-630.
Bremner, I. 1987. Involvement of metallothionein in the hepatic metabo-
lism of copper. J. Nutr. 117:19-29.
Bremner, 1. 1998. Manifestations of copper excess. Am. J. Clin. Nutr.
67:1969S-1073S.
Bremner, 1., B. W. Young, and C. F. Mills. 1976. Protective effect of zinc
supplementation against copper toxicosis in sheep. Br. J. Nutr.
36:551-561.
Brewer, G. J., R. D. Dick, W. Schall, V. Yuzbasiyan-Gurkan, T. P.
MuUaney, C. Pace, J. Lindgren, M. Thomas, and G. Padgett. 1992. Use
of zinc acetate to treat copper toxicosis in dogs. J. Am. Vet. Med. Assoc.
201:564-567.
Buckley, W. T., and R. M. Tait. 1981. Chronic copper toxicity in lambs. A
survey of blood constituent responses. Can. J. Anim. Sci. 61:613-624.
Bunch, R. J., J. T. McCall, V. C. Speer, and V. W. Hays. 1965. Copper
supplementation for weanling pigs. J. Anim. Sci. 24:995-1000.
Chapman, H. L., S. L. Nelson, R. W. Kidder, W. L. Sippel, and C. W.
Kidder. 1962. Toxicology of cupric sulfate for beef cattle. J. Anim. Sci.
21:960-962.
Chartier, C, E. Etter, H. Hoste, 1. Pors, C. Koch, and B. Dellac. 2000.
Efficacy of copper oxide needles for the control of nematode parasites
in dairy goats. Vet. Res. Comm. 24:389-399.
Chiou, P. W. S., K. L. Chen, and B. Yu. 1997. Toxicity, tissue accumulation
and residue in egg and excreta of copper in laying hens. Anim. Feed Sci.
Tech. 67:49-60.
Chiou, P. W. S., C. L. Chen, K. L. Chen, and C. P. Wu. 1999. Effect of high
dietary copper on the morphology of gastro-intestinal tract in broiler
chickens. Asian- Australas. J. Anim. Sci. 12(4):548-553.
Christmas, R. B., and R, H. Harms. 1979. The effect of supplemental cop-
per and methionine on the performance of turkey poults. Poult. Sci.
58:382-384.
Clearwater, S. J., A. M. Farag, and J, S. Meyer. 2002. Bioavailability and
toxicity of dietborne copper and zinc in fish. Comp. Biochem. Physiol.
C Toxicol. Pharmacol.l32(3):269-313.
Cromwell, G. L., M. D. Lindemann, H. J. Monegue, D. D. Hall, and D. E.
Orr, Jr. 1998. Tribasic copper chloride and copper sulfate as copper
sources for weanling pigs. J. Anim. Sci. 76:1 18-123.
Cromwell, G. L., T. S. Stahly, and H. J. Monegue. 1989. Effects of source
and level of copper on performance and liver copper stores in weanling
pigs. J. Anim. Sci. 67:2996-3002.
Cromwell, G. L., H. J. Monegue, and T. S. Stahly. 1993. Long-term effects
of feeding a high copper diet to sows during gestation and lactation. J.
Anim. Sci. 71:2996-3002.
DeGoey, L. W., R. C. Wahlstrom, and R. J. Emerick. 1971. Studies of high
level copper supplementation to rations for growing swine. J. Anim.
Sci. 33:52-57.
Dixon, D. G., and J. W. Hilton. 1985. Effects of available dietary carbohy-
drate and water temperature on the chronic toxicity of waterborne cop-
per to rainbow trout (Salmo gairdneri). Can. J. Fish. Aquat. Sci.
42:1007-1013.
Du, Z., R. W. Hemken, and R. J. Harmon. 1996. Copper metabolism of
Holstein and Jersey cows and heifers fed diets high in cupric sulfate or
copper proteinate. J. Dairy Sci. 79:1873-1880.
EC (European Commission). 2003. Opinion of the Scientific Committee for
Animal Nutrition on the use of copper in feedingstuffs. European Com-
mission Health and Consumer Protection Directorate-General.
Edmonds, M. S., and D. H. Baker. 1986. Toxic effects of supplemental
copper and roxarsone when fed alone or in combination to young pigs.
J. Anim. Sci. 63:533-537.
Engle, T. E., and J. W. Spears. 2000. Effects of dietary copper concentra-
tion and source on performance and copper status of growing and fin-
ishing steers. J. Anim. Sci. 78:2446-2451.
Engle, T. E., J. W. Spears, L. Xi, and F. W. Edens. 2000a. Dietary copper
effects on lipid metabolism and circulating catecholamine concentra-
tions in finishing steers. J. Anim. Sci. 78:2737-2744.
Engle, T. E., J. W. Spears, T. A. Armstrong, C. L. Wright, and J. Odle.
2000b. Effects of dietary copper source and concentration on carcass
characteristics and lipid and cholesterol metabolism in growing and fin-
ishing steers. J. Anim. Sci. 78:1053-1059.
Engle, T. E., V. Fellner, and J. W. Spears. 2001. Copper status, serum cho-
lesterol, and milk fatty acid profile in Holstein cows fed varying con-
centrations of copper. J. Dairy Sci. 84:2308-2313.
Felsman, R. J., M. B. Wise, R. W. Harvey, and E. B. Barrick. 1973. Effect
of added dietary levels of copper sulfate and an antibiotic on per-
formance and certain blood constituents of calves. J. Anim. Sci.
36:157-160.
Fuentealba, 1. C, R. W. Davis, M. E. Elmes, B. Jasani, and S. Haywood.
1993. Mechanisms of tolerance in the copper-loaded rat. Exp. Mol. Path.
59:71-84.
Gatlin, D. M. 1., and R. P. Wilson. 1986. Dietary copper requirement of
fingerling channel catfish. Aquaculture 54:277—285.
Georgopoulos, P. G., A. Roy, R. E. Opiekun, P. J. Lioy, and M. J. Yonone-
Lioy. 2002. Environmental Dynamics and Human Exposure to Copper.
Vol. 1, Environmental Dynamics and Human Exposure Issues. New
York: International Copper Association.
Gooneratne, S. R., J. M. Howell, and J. M. Gawthorne. 1979. Intracellular
distribution of copper in the liver of normal and copper loaded sheep.
Res. Vet. Sci. 27:30-37.
Gooneratne, S. R., W. T. Buckley, and D. R. Chiistensen. 1989. Review of
copper deficiency and metabolism in ruminants. Can. J. Anim. Sci.
69:819-845.
Gooneratne, S. R., H. W. Symonds, J. V. Bailey, and D. R. Christensen.
1994. Effects of dietary copper, molybdenum and sulfur on biliary cop-
per and zinc excretion in Simmental and Angus cattle. Can. J. Anim.
Sci. 74:315-325.
Gopinath, C, G. A. Hall, and J. M. Howell. 1974. The effects of chronic
copper poisoning on the kidneys of sheep. Res. Vet. Sci. 16:57-65.
Grace, N. D., S. O. Knowles, J. R. Rounce, D. M. West, and J. Lee. 1998.
Effect of increasing pasture copper concentrations on the copper status
of grazing Romney sheep. N. Z. J. Agric. Res. 41 :377— 386.
Grobner, M. A., P. R. Cheeke, and N. M. Patton. 1986. Effect of dietary
copper and oxytetracycline on growth and mortality of weanling rab-
bits. J. Appl. Rabbit Res. 9:46-53.
Gummow, B. 1996. Experimentally induced chi'onic copper toxicity in
cattle. Onderstepoort J. Vet. Res. 63:277-288.
Hamar, D. W., C. L. Bedwell, J. L. Johnson, P. C. Schultheiss, M. Raisbeck,
D. M. Grotelueschen, E. S. Williams, D. O'Toole, R. J. Paumer, M. G.
Vickers, and T. J. Graham. 1997. Iatrogenic copper toxicosis induced
by administering copper oxide boluses to neonatal calves. J. Vet. Diagn.
Invest. 9:441^M3.
Hamilton, S. J., and K. J. Buhl. 1990. Safety assessment of selected inor-
ganic elements to fry of Chinook salmon (Oncorhynchus twhawytscha).
Ecotoxicol. Environ. Safe. 20:307-324.
Harms, R. H., and R. E. Buresh. 1987. Influence of three levels of copper on
the performance of turkey poults with diets containing two sources of
methionine. Pouh. Sci. 66:721-724.
Harris, E. D. 1997. Copper. Pp. 23 1-273 in Handbook of Nutritional Essen-
tial Mineral Elements, B. L. O'Dell and R. A. Sunde, eds. New York:
Marcel Dekker.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
COPPER
145
Haywood, S. 1985. Copper toxicosis and tolerance in the rat. J. Pathol.
145:149-158.
Hebert, C. D., M. R. Elwell, G. S. Travlos, C. J. Fitz, and J. R. Bucher.
1993. Subchronic toxicity of cupric sulfate administered in drinking
water and fed to rats and mice. Fund. Appl. Toxicol. 21:461^75.
Hidiroglou, M., D. P. Heaney, and K. E. Hartin. 1984. Copper poisoning in
a flock of sheep. Copper excretion patterns after treatment with molyb-
denum and sulfur or penicillamine. Can. Vet. J. 25:377-382.
Hill, G. M., G. L. Cromwell, T. D. Crenshaw, C. R. Dove, R. C. Ewan, D.
A. Knabe, A. J. Lewis, G. W. Libal, D. C. Mahan, G. C. Shurson, L. L.
Southern, and T. L. Veum. 2000. Growth promotion effects and plasma
changes from feeding high dietary concentrations of zinc and copper to
weanling pigs (regional study). J. Anim. Sci. 78:1010-1016.
Hill, R., and H. L. Williams. 1965. The effects of intensively reared lambs
of diets containing excess copper. Vet. Rec. 77:1043-1045.
Hintz, H. F. 1987. Copper toxicity. Equine Pract. 9:17-18.
Hogan, K. G., D. F. L. Money, and A. Blayney. 1968. The effect of a mo-
lybdate and sulfate supplement on the accumulation of copper in the
livers of penned sheep. N. Z. J. Agric. Res. 1 1 :435 -l-ll .
Howarth, R. S., and J. B. Sprague. 1978. Copper lethality to rainbow trout
in waters of various hardness and pH. Water Res. 12:455^62.
Howell, J. M.., andS. R. Gooneratne. 1987. The pathology of copper toxic-
ity in animals. Pp. 53-78 in Copper in Animals and Man. Vol. 11, J. M.
Howell and J. M. Gawthorne, eds. Boca Raton, FL: CRC Press.
Howell, J. M., H. S. Deol, P. R. Dorling, and J. B. Thomas. 1991. Experi-
mental copper and heliotrope intoxication in sheep: morphological
changes J. Comp. Pathol. 105(l):49-74.
Hyun, C, and L. J Filippich. 2004. Inherited copper toxicosis with emphasis
on copper toxicosis in Bedlington terriers. J. Exp. Anim. Sci. 43:39-64.
Ivan, M., D. M. Veira, and C. A. Kelleher. 1986. The alleviation of chronic
copper toxicity in sheep by ciliate protozoa. Br. J. Nutr. 55:361-367.
Ivan, M., M. D. Dayrell, and M. Hidiroglou. 1992. Effects of bentonite and
monensin on selected elements in the stomach and liver of fauna-free
and faunated sheep. J. Dairy Sci. 75:201—208.
Izquierdo, O. A., and D. H. Baker. 1986. Bioavailability of copper in pig
feces. Can. J. Anim. Sci. 66:1145-1148.
Jackson, N., and M. H. Stevenson. 1981. A study of the effects of dietary
added cupric oxide on the laying, domestic fowl and a comparison with
the effects of hydrated copper sulfate. Br. J. Nutr. 45:99-1 10.
Jackson, N., M. H. Stevenson, and G. McC. Kirkpatrick. 1979. Effects of
the protracted feeding of copper sulfate- supplemented diets to laying,
domestic fowl on egg production and on specific tissues, with special
reference to mineral content. Br. J. Nutr. 42:253—266.
Jenkins, K. J., and M. Hidiroglou. 1989. Tolerance of the calf for excess
copper in milk replacer. J. Dairy Sci. 72:150-156.
Jensen, L. S., and D. V. Maurice. 1978. Effect of methionine on copper in-
duced growth depression and gizzard erosion. Poult. Sci. 57:1530—1532.
Jensen, L. S., and D. V. Maurice. 1979. Influence of sulfur amino acids on
copper toxicity in chicks. J. Nutr. 109(l):91-97.
Kamunde, C. N., M. Grosell, J. N. A. Lott, and C. M. Wood. 2001. Copper
metabolism and gut morphology in rainbow trout {Oncorhynchus
mykiss) during chi'onic sublethal dietary copper exposure. Can. J. Fish.
Aquat. Sci. 58:293-305.
Kegley, E. B., and J. W. Spears. 1994. Bioavailability of feed-grade copper
sources (oxide, sulfate, or lysine) in growing cattle. J. Anim. Sci.
72:2728-2734.
King, J. O. L. 1975a. The feeding of copper sulfate to ducklings. Br. Poult.
Sci. 16:409^11.
King, J. O. L. 1975b. The feeding of copper sulfate to growing rabbits. Br.
Vet. J. 131:70-75.
Kline, R. D., V. W. Hays, and G. L. Cromwell. 1971. Effects of copper,
molybdenum and sulfate on performance, hematology and copper stores
of pigs and lambs. J. Anim. Sci. 33:771-779.
Knox, D., C. B. Cowey, and J. W. Adron. 1984. Effects of dietary zinc
intake upon copper metabolism in rainbow trout (Salmo Gairdneri).
Aquaculture 40:199-207.
Kornegay, E. T.. P. H. G. van Heugten, M. D. Lindemann, and D. J.
Blodgett. 1989. Effects of biotin and high copper levels on performance
and immune response of weanling pigs. J. Anim. Sci. 67:1471-1477.
Lanno, R. P., S. J. Slinger, and J. W. Hilton. 1985. Maximum tolerable and
toxicity levels of dietary copper in rainbow trout (Salmo Gairdneri
Richardson). Aquaculture 49:257-268.
Ledoux, D. R., P. R. Henry, C. B. Ammerman, P. V. Rao, and R. D. Miles.
199 1 . Estimation of the relative bioavailability of inorganic copper sources
for chicks using tissue uptake of copper. J. Anim. Sci. 69:215-222.
Leeson, S., A. K. Zubair, E. J. Squires, and C. Forsberg. 1997. Influence of
dietary levels of fat, fiber, and copper sulfate and fat rancidity on cecal
activity in the growing turkey. Poult. Sci. 76:59-66.
Linder, M. C. 2002. Biochemistry and molecular biology of copper in mam-
mals. Pp. 3-32 in Handbook of Copper Pharmacology and Toxicology,
E. J. Massaro, ed. Totowa, NJ: Humana Press.
Littledike, E. T., and L. D. Young. 1993. Effect of sire and dam breed on
copper status of fat lambs. J. Anim. Sci. 71:774—778.
Luginbuhl, J. M., M. H. Poore, J. W. Spears, and T. T. Brown. 2000. Effect
of dietary copper level on performance and copper status of growing
meat goats. Sheep Goat Res. J. 16:65-71.
MacPherson, A., E. M. Milne, and A. J. MacPherson. 1997. Copper poison-
ing in ewes. Vet. Rec. 141:631.
Miles, R. D., S. F. O'Keefe, P. R. Henry, C. B. Ammerman, and X. G. Luo.
1998. The effect of dietary supplementation with copper sulfate or triba-
sic copper chloride on broiler performance, relative copper
bioavailability, and dietary proxidant activity. Poult. Sci. 77:416^25.
Mills, C. F., and 1. Bremner. 1980. Nutritional aspects of molybdenum in
animals. Pp. 519-542 in Molybdenum and Molybdenum Containing
Enzymes, M. Coughlan, ed. New York: Pergamon Press.
Minson, D. J. 1990. Forage in Ruminant Nutrition. New York: Academic
Press.
Mount, D. R., A. K. Barth, T. D. Garrison, K. A. Barten, and J. R. Hockette.
1994. Dietary and waterborne exposure of rainbow trout (Oncorhynchus
mykiss) to copper, cadmium, lead and zinc using a live diet. Environ.
Toxicol. Chem. 13:2031-2041.
MuUis, L. A., J. W. Spears, and R. L. McCraw. 2003. Effects of breed
(Angus vs Simmental) and copper and zinc source on mineral status of
steers fed high dietary iron. J. Anim. Sci. 81:318—322.
Murai, T., J. W. Andrews, and R. G. Smith. 1981. Effects of dietary copper
on channel catfish. Aquaculture 22:353-357.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
Patton, N. M., D. J. Harris, M. A. Grobner, R. A. Swick, and P. R. Cheeke.
1982. The effect of dietary copper sulfate on enteritis in fryer rabbits. J.
Appl. Rabbit Res. 5:78-82.
Payne, C. G., D. C. Martens, E. T. Kornegay, and M. D. Lindemann. 1988.
Availability and form of copper in three soils following eight annual
applications of copper-enriched swine manure. J. Environ. Qual.
17:740-746.
Pena, M. M., J. Lee, andD. J. Thiele. 1999. A delicate balance: homeostatic
control of copper uptake and distribution. J. Nutr. 129:1251—1260.
Persia, M. E., C. M. Parsons, and D. H. Baker. 2003. Amelioration of oral
copper toxicity in chicks by dietary additions of ascorbic acid, cysteine
and zinc. Nutr. Res. 23:1709-1718.
Pesti, G. M., andR. 1. Bakalli. 1996. Studies on the feeding of cupric sulfate
pentahydrate and cupric citrate to broiler chickens. Poult. Sci. 75: 1086—
1091.
Pond, W. G. 1989. Effects of dietary protein level and clinoptilolite on the
weight gain and liver mineral response of growing lambs to copper
supplementation. J. Anim. Sci. 67:2772—2781.
Prince, T. J., V. W. Hays, and G. L. Cromwell. 1975. Environmental effects
of high copper pig manure on pasture for sheep. J. Anim. Sci. 41:326
(Abstr.).
Robbins, K. R., andD. H. Baker. 1980. Effect of sulfur amino acid level and
source on the performance of chicks fed high levels of copper. Poult.
Sci. 59:1246-1253.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
146
MINERAL TOLERANCE OF ANIMALS
Sargison, N. D., and P. R. Scott. 1996. The diagnosis and treatment of
chronic copper poisoning in 4- to 12-week-old single-suckled calves.
Agri-Practice 17:36^0.
Saylor, W. W., and R. M. Leach. 1980. Intracellular distribution of copper
and zinc in sheep: effect of age and dietary levels of the metals. J. Nutr.
110:448^59.
Saylor, W. W., F. D. Morrow, and R. M. Leach. 1980. Copper- and zinc-
binding proteins in sheep liver and intestine: effect of dietary levels of
the metals. J. Nutr. 110:460-468.
Shand, A., and G. Lewis. 1957. Chronic copper poisoning in young calves.
Vet. Rec. 69:618-620.
Smith, J. D., R. M. Jordan, and M. L. Nelson. 1975. Tolerance of ponies to
high levels of dietary copper. J. Anim. Sci. 41:1645—1649.
Smith, M. J., and A. G. Heath. 1979. Acute toxicity of copper, chromate,
zinc, and cyanide to freshwater fish: effect of different temperatures.
Bull. Environ. Contam. Toxicol. 22:113-119.
Solaiman, S. G., M. A. Maloney, M. A. Qureshi, G. Davis, and G. D. An-
drea. 200 1 . Effects of high copper supplements on performance, health,
plasma copper and enzymes in goats. Small Ruminant Res. 41:127-139.
Soli, N. E., and 1. Nafstad. 1978. Effects of daily oral administration of
copper to goats. Acta Vet. Scand. 19:451-568.
Spears, J. W. 2003. Trace mineral bioavailability in ruminants. J. Nutr.
133:1506S-1509S.
Spears, J. W., E. B. Kegley, and L. A. Mullis. 2004. Bioavailability of
copper from tribasic copper chloride and copper sulfate in growing
cattle. Anim. Feed Sci. Technol. 116:1-13.
Steffen, D. J., M. P. Carlson, and H. H. Casper. 1997. Copper toxicosis in
suckling beef calves associated with improper administration of copper
oxide boluses. J. Vet. Diagn. Invest. 9:443—446.
Suttle, N.F.I 974. Effects of organic and inorganic sulfur on the availability
of dietary copper to sheep. Br. J. Nutr. 32:559-568.
Suttle, N. F. 1977. Reducing the potential copper toxicity of concentrates to
sheep by the use of molybdenum and sulfur supplements. Anim. Feed
Sci. Technol. 2:235-246.
Suttle, N. F. 1991. The interactions between copper, molybdenum, and sul-
fur in niminant nutrition. Annu. Rev. Nutr. 11:121-140.
Suttle, N. F., and J. Price. 1976. The potential toxicity of copper-rich animal
excreta to sheep. Anim. Prod. 23:233-241.
Suttle, N. F., C. S. Munro, and A. C. Field. 1978. The accumulation of
copper in the liver of lambs on diets containing dried poultry waste.
Anim. Prod. 26:39^5.
Suttle, N. F., R. M. Lewis, and J. N. W. Small. 2002. Effects of breed and
family on rate of copper accretion in the liver of purebred Charollais,
Suffolk and Texel lambs. Anim. Sci. 75(2):295-302.
Taylor, E. W., M. W. Beaumont, P. J. Butler, J. Mair, and M. S. 1. Mujallid.
1996. Lethal and sub-lethal effects of copper upon fish: a role for am-
monia toxicity? Pp. 85-1 13 in Toxicology of Aquatic Pollution, E. W.
Taylor, ed. Cambridge: Cambridge University Press.
Thornburg, L. P., G. Rottinghaus, M. McGowan, K. Kupka, S. Crawford,
and S. Forbes. 1990. Hepatic copper concentrations in purebred and
mixed-breed dogs. Vet. Pathol. 27:81-88.
Todd, J. R. 1969. Chronic copper toxicity of ruminants. Proc. Nutr. Soc.
28:189-198.
Tokarnia, C. H., J. Dobereiner, P. V. Peixoto, and S. S. Moraes. 2000. Out-
break of copper poisoning in cattle fed poultry litter. Vet. Human
Toxicol. 42:92-95.
Underwood, E. J. 1977. Trace Elements in Human and Animal Nutrition,
4th ed. New York: Academic Press.
Underwood, E. J., and N. F. Suttle. 1999. The Mineral Nutrition of Live-
stock, 3rd ed. New York: CABl Publishing.
USGS (U.S. Geological Survey). 2004. Mineral Commodity Summaries.
Available at http://minerals.usgs.gov/minerals/pubs/commodity/copper.
Accessed May 5, 2005.
Van Ryssen, J. B. J. 1994. The effectiveness of using supplemental zinc and
molybdenum to reduce the copper content in the liver of hypercuprotic
sheep. J. South African Vet. Assoc. 62:59-63.
Van Ryssen, J. B. J., and P. R. Barrowman. 1987. Effect of ionophores on
the accumulation of copper in the livers of sheep. Anim. Prod.
44:255-261.
Van Vleet, J. F. 1 982. Amounts of twelve elements required to induce sele-
nium-vitamin E deficiency in ducklings. Am. J. Vet. Res. 43:851-857.
Van Vleet, J. F., G. D. Boon, and V. J. Ferrans. 1981 . Induction of lesions of
selenium-vitamin E deficiency in ducklings fed silver, copper, cobalt,
tellurium, cadmium or zinc: protection by selenium or vitamin E supple-
ments. Am. J. Vet. Res. 42:1206-1216.
Viarengo, A., B. Burlando, and C. Bolognesis. 2002. Cellular responses to
copper in aquatic organisms. Pp. 4 1 7^3 1 in Handbook of Copper Phar-
macology and Toxicology, E. J. Massaro, ed. Totowa, NJ: Humana
Press.
VL A. 200 1 . Veterinary Laboratories Agency Surveillance Report. July sees
an increased incidence of copper poisoning in cattle. Vet. Rec.
149:257-260.
Wang, J., S. R. Rogers, and G. M. Pesti. 1987. Influence of choline and
sulfate on copper and toxicity and substitution of an antagonism be-
tween methionine and copper supplements to chick diets. Poult. Sci.
66:1500-1507.
Ward, J. D., J. W. Spears, and G. P. Gengelbach. 1995. Differences in cop-
per status and copper metabolism among Angus, Simmental, and Charo-
lais cattle. J. Anim. Sci. 73:571-577.
Ward, J. D., J. W. Spears, andE. B. Kegley. 1996. Bioavailability of copper
proteinate and copper carbonate relative to copper sulfate in cattle. J.
Dairy Sci. 79:127-132.
White, C. L., D. G. Masters, D. 1. Paynter, J. McC. Howell, S. P. Roe, M. J.
Barnes, and J. G. Allen. 1994. The effects of supplementary copper and
a mineral mix on the development of Lupinosis in sheep. Aust. J. Agric.
Res. 45:279-291.
Wideman, R. F., Jr., Y. K. Kirby, T. L. Barton, D. Clark, G. R. Bayyari, W.
E. Huff, P. A. Moore, and P. A. Dunn. 1996. Excess dietary copper
triggers enlargement of the proventriculus in broilers. J. Appl. Poult.
Res. 5(3):219-230.
Wood, E. C, and A. N. Worden. 1973. The influence of dietary copper
concentration on hepatic copper in the duckling, and the chick. J. Sci.
Food Agric. 24:167-174.
Woolliams, J. A., N. F. Suttle, G. Wiener, A. C. Field, and C. Woolliams.
1982. The effect of breed of sire on the accumulation of copper in lambs,
with particular reference to copper toxicity. Anim. Prod. 35:299-307.
WHO (World Health Organization). 1998. Copper. Environmental Health
Criteria 200. Geneva: World Health Organization.
Wright, C. L., J. W. Spears, T. E. Engle, and T. A. Armstrong. 2000. Effect
of dietary copper level and high sulfate water on copper metabolism and
growth in cattle. Pp. 759-762 in Trace Elements in Man and Animals
10, A. M. Roussel, R. A. Anderson, and A. E. Farrier, eds. New York:
Kluwer Academic/Plenum Publishers.
Yu, S., C. E. West, and A. C. Beynen. 1994. Increasing intakes of iron
reduces status, absorption and biliary excretion of copper in rats. Br. J.
Nutr. 71:887-895.
Zervas, G., E. Nikolaou, and A. Mantzios. 1990. Comparative study of
chronic copper poisoning in lambs and young goats. Anim. Prod.
50:497-506.
Copyright © National Academy of Sciences. All rights reserved.
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COPPER
153
TABLE 13-2 Copper Concentrations in Fluids and Tissues of Animals (mg/kg)
Animal
Quantity
Source
Duration
Route Liver Kidney Muscle
Heart Egg Reference
Rabbits
Chicks
Laying hens
Control
CUSO4
48 wk
Diet
12"
3.4°
Jackson and Stevenson,
+ 150 mg/kg
16
3.4
1981
+ 300 mg/kg
32
3.3
+ 450 mg/kg
61
3.0
Fish,
rainbow
trout
Control
+ 250 mg/kg
+ 500 mg/kg
Control
+ 250 mg/kg
Control
+ 150 n
+ 300n
+ 450n
Control
+ 120 mg/kg
+ 240 mg/kg
Control
+ 20 mg/kg
+ 40 mg/kg
Control
+ 30 mg/kg
Control
+ 300 mg/kg
+ 1,000 mg/kg
CuSO,
CuSO,
28 d
42 d
Diet
Diet
12°
195
890
3.1''
5
10
11
15
2.6
3.6
3.4
0.4*
0.4
2.8"
3.0
Grobner et al., 1986
Pesti and Bakalli, 1996
CuSO,
132 d
Bradley et al., 1983
CuSO
CuSO,
350° 14°
2,400 50
7.0°
26.0
28 d
Diet
38*
45
100
1.7*
1.7
10.0
0.3*
0.3
0.3
Zervas et al., 1990
Kamunde et al., 2001
°Dry tissue basis.
*Wet tissue basis.
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14
Fluorine
INTRODUCTION
Fluorine (F) is tiie most electronegative and reactive of
all elements and can form compounds with all elements ex-
cept helium, neon, and argon. It has an atomic number of 9
and an atomic weight of 18.9984. Fluorine is a pale green-
ish-yellow, highly toxic gas with a characteristic pungent
odor. In nature, it does not occur in the elemental state but
forms organic or inorganic compounds as fluorides. Fluo-
rine occurs mainly as salts containing the halide anion, fluo-
ride. It is found in both igneous and sedimentary rock and
constitutes about 0.06-0.09 percent of the upper layers of
the Earth's crust. It ranks 13th in abundance among elements
in the Earth's crust. The most important inorganic fluorine-
bearing minerals are fluorspar (CaFj), fluorapatite
(Caj(P04)3F), and cryolite (NajAlFg). The largest known
deposits of fluoride are located in the United States, United
Kingdom, and Germany.
Inorganic fluorides are used in steel, glass, brick, ceramic,
and adhesive manufacture. Hydrogen fluoride (HF), a major
industrial compound, is widely used in the production of
cryolite, aluminium fluoride (AIF3), gasoline alkylates, and
chlorofluorocarbons. It is also used for cleaning or etching
compounds for semiconductors, glass, aluminium, and tan-
ning leather, and it is also used in rust removers. HF is highly
soluble in water in which it forms hydrofluoric acid. Cal-
cium fluoride (CaFj), with a fluorine content of 48.7 per-
cent, is relatively insoluble in water and dilute acids and
bases. It is the principal fluoride-containing mineral pro-
duced for industrial use as a flux in steel, glass, and enamel
production, and as the raw material for production of hy-
drofluoric acid and anhydrous HF. Sodium fluoride (NaF),
fluorosilic acid (HjSiFg), and sodium hexafluorosilicate
(NajSiFg) are used for controlled fluoridation of drinking
water.
Fluorides are ubiquitous in the environment and are re-
leased naturally through the weathering and dissolution of
minerals, as emissions from volcanoes, and as marine aero-
sols (Symonds et al., 1988; ATSDR, 2003). Inorganic fluo-
rides are released in the environment from phosphate fertil-
izer production and use; aluminium smelting; steel produc-
tion; glass, enamel, brick, and ceramic manufacturing; glue
and adhesive production; pesticides; and drinking water fluo-
ridation (Burns and AUcroft, 1964; Neumiiller, 1981; Fuge,
1988; Fuge and Andrews, 1988). Transformation and trans-
port of inorganic fluorides in the aquatic environment is in-
fluenced by pH, hardness, and the concentration of ion-ex-
change materials (e.g., bentonite clay and humic acid) in
water. In the environment, vaporization, aerosol, and hy-
drolysis are the main factors that determine the fate of fluo-
rides. Generally, the formation of aluminium and calcium
complexes and pH affect the fate of fluorides in soils. In
areas of extreme acidity and alkalinity, inorganic fluorides
leach into surface or ground water, and their solubilization
in water may be further enhanced by the presence of ion-
exchange materials (Pickering et al., 1988). During weather-
ing under acidic conditions, certain fluorine-bearing miner-
als (e.g., cryolite) dissolve rapidly; however, the solubility
of fluorapatite and calcium fluoride is relatively slow (Fuge
and Andrews, 1988). Soils rich in calcium carbonate or
amorphous aluminium hydroxides may bind inorganic fluo-
ride by forming insoluble calcium fluoride or aluminium-
fluoro-hydroxide complexes, thus limiting leaching from the
soil and uptake by plants (Fluhler et al., 1982). Other cations
(e.g., iron) also contribute to the fixation of fluoride (Murray,
1983, 1984); however, soil phosphate may contribute to the
mobility of inorganic fluoride (Kabata-Pendias and Pendias,
1984). The fate of inorganic fluorides released to soil also
depends on their chemical form, rate of deposition, soil
chemistry, and climate (Davison, 1983).
ESSENTIALITY
Fluorine is considered an essential element, although spe-
cific deficiency signs have not been observed in experimen-
tal animals. No one has yet produced an environment suffi-
154
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FLUORINE
155
ciently devoid of this element tliat survival of an animal was
virtually threatened. Fluorine was identified as a constituent
of bones and teeth as early as 1905. Attempts to demonstrate
the essential role of fluorine in rat experiments with other
than dental criteria have not been successful. McClendon
and Gershon-Cohen (1953) fed weaning rats for 66 days
upon materials grown hydroponically in water considered to
be "fluorine free." The rats weighed 5 1 g and had 10 carious
molars per animal compared to fluoride-supplemented rats
that weighed 128 g and had 0.5 carious molars per animal.
Maurer and Day (1957) purified dietary ingredients and pro-
duced a diet that contained about 0.007 |jg/g fluoride on
which four generations of rats were raised without evidence
of impaired general health, dental health, or weight gain as
compared to rats raised on the same diet plus 2 |jg/mL of
fluoride in their drinking water. In the early 1970s, it was
reported that mice fed low fluoride (0.005 pg/g diet) exhib-
ited anemia and infertility compared to mice supplemented
with fluoride (50 |Jg/mL drinking water) (Messer et al., 1972,
1973). Subsequently, it was determined that the diets of these
mice were low in iron and that high dietary fluoride, similar
to that fed in supplemented controls, improved iron absorp-
tion or use (Tao and Suttie, 1976). Mice fed low fluoride
diets containing sufficient iron neither exhibited anemia nor
infertility. Relatively high fluoride supplementation (2.5-
7.5 |Jg/g diet) to rats fed low fluoride (0.04 |ig/g diet) slightly
improved the growth of suboptimally growing rats. Weber
(1966) reported that in six generations of study on mice, no
definite differences in reproduction were observed between
the low (0.25 |Jg/g) and high (65 |Jg/g) fluoride groups.
Schwarz and Milne (1972), working in a filtered-air envi-
ronment, reported a favorable growth response when small
increments (1-2.5 pg/g) of fluoride were added to a low
fluoride diet for rats. Studies on high fluoride supplements
indicate that these growth-promoting effects were probably
pharmacological. High or pharmacological amounts of fluo-
ride have been also found to depress lipid absorption and to
alleviate nephrocalcinosis induced by feeding phosphorus
and to alter soft tissue calcification by magnesium deprivation.
Several decades of research on humans have strength-
ened the view that fluorine is essential to reduce the preva-
lence of dental caries, and it should be considered as an es-
sential element on this basis (NRC, 1993). A fluoride
supplement of 80 pg/g diet enhanced the growth of broiler
chickens (Gutierrez et al., 1993). To date, sufficient evidence
of the essentiality of fluorine in farms animals has been pro-
vided only by Anke et al. (1997). Female goats developed
skeletal abnormalities and poor growth in their offspring for
10 generations on a diet containing < 0.3 mg F/kg DM. These
findings need to be confirmed in other animal species before
being accepted as evidence for essentiality in higher ani-
mals. Fluoride may be needed for proper functioning of some
enzymes, given that in vitro its activities, including histidine
methyl transferase, stabilize the interaction between gua-
nosine triphosphatase (GTPase) and GTPase-activitating
proteins, and affect the posttranslational assembly of
glycosaminoglycan chains in mineralizing bone cells (Kirk,
1991).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Fluorine is too reactive to be analyzed directly in biologi-
cal samples and environmental media, and its measurement
is restricted to the detection of the free anion (F"). The most
widely used analytical method is a potentiometric technique
that measures free anion using the fluoride ion-selective elec-
trode (F-ISE) (Neumiiller, 1981; Harzdorf et al., 1986;
ATSDR, 2003). This method has been used for the quantifi-
cation of fluoride in biological tissues and fluids (e.g., urine,
serum, plasma, organs, bone, and teeth), foodstuffs, and en-
vironmental media (e.g., air, water, and soil). The variations
in the sample preparation procedures and the recovery of
this element may affect the detection limits using F-ISE. The
values reported by this method range from 0. 1 to 300 ng/m^ in
air, from 1 to 1,000 |ig/L in water, and from 0.05 to 20 mg/kg
in nonskeletal tissues (Harzdorf et al., 1986; ATSDR, 2003).
Fluoride ions form a stable, colorless complex such as
(AlFg)-'", (FeFg) ^", and (ZrFg) ^^ with certain trivalent ions.
Colorimetric methods are based on the bleaching of these
metal complexes with organic dyes in the presence of fluo-
ride (WHO, 1984). Other methods for the quantification of
fluorine include gas chromatography (GC), ion chromatog-
raphy, capillary electrophoresis, atomic absorption, and pho-
ton activation (Neumiiller, 1981; Harzdorf et al., 1986; Wen
et al., 1996; ATSDR, 2003). GC methods have been used to
measure fluoride concentrations in urine and plasma but require
extraction and derivatization using trimethylchlorosilane in
toluene to produce trimethylfluorosilane (Ikenishi et al.,
1988). Analytical methods based on neutron or proton acti-
vation of fluorine- 19 have been also developed that measure
emitted gamma rays or x-rays using lithium-drifted germa-
nium detectors (Shroy et al., 1982; Knight et al., 1988).
These techniques do not depend on the specific sample
matrix or chemical form.
Appropriate sample preparation is the critical step in the
accurate quantification of fluoride, especially where only the
free fluoride ion is measured. For analysis involving bio-
logical materials, the most accurate method is microdiffusion
techniques such as the acid-hexamethyldisioxane (HMDS)
diffusion method described by Taves (1968). Methods in-
volving acid or alkali digestion may not convert all complex
organic fluorine into an ionic form that can be conveniently
measured (Venkateswarlu, 1983). Open-ashing methods
may result in the loss of volatile fluoride compounds or of
fluoride itself at temperatures in excess of 550°C, or they
may result in contamination with extraneous fluoride
(Venkateswarlu, 1983; Campbell, 1987).
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156
MINERAL TOLERANCE OF ANIMALS
REGULATION AND METABOLISM
Approximately 75 to 90 percent of ingested fluoride is
absorbed in the stomach and small intestine as well as rumen
of animals (Messer, 1984; WHO, 1994; Cerklewski, 1997).
The efficiency of fluoride absorption depends on the solubil-
ity of the fluoride compound and the presence of other di-
etary components. In the stomach, low pH conditions favor
the formation of highly diffusible hydrogen fluoride (pK^ =
3.4). Therefore, the conditions that promote gastric acidity
increase the rate of fluoride absorption, and it is impaired by
alkalinity. The absorption from the small intestine occurs as
the fluoride ion by non-pH dependent diffusion (Nopakun
and Messer, 1990). In the fasted state, fluoride absorption
from either fluoridated water or sodium fluoride is almost
100 percent (Rao, 1984; Trautner and Seibert, 1986). Soluble
fluorides, such as sodium fluoride, are almost completely
absorbed. Less soluble sources, such as bone meal, are rela-
tively poorly absorbed (<50 percent). Calcium, magnesium,
aluminum, sodium chloride, and high lipid levels are the
main dietary factors that depress fluoride absorption (NRC,
1980; Cerklewski, 1997).
The respiratory tract is the major route of absorption of
both gas and particulate fluoride from industrial emissions.
Depending on their aerodynamic characteristics and solubil-
ity, fluoride-containing particles are deposited in the bron-
chioles and nasopharynx and absorbed either immediately or
gradually released from lungs (Mclvor, 1990). Dermal ab-
sorption of fluoride has been reported only in the case of
burns resulting from exposure to hydrofluoric acid (Burke et
al., 1973).
Removal of fluoride from circulation occurs principally
through two mechanisms: renal excretion and calcified tis-
sue deposition. Following absorption, the concentration of
ionic fluoride (F") increases in plasma where it reacts with
calcium to form calcium fluoride. Some ionic fluoride may
become non-ionic by coordinating with macromolecules
such as proteins (Singer and Armstrong, 1964; Kirk, 1991).
About 75 percent of fluoride in the blood is in the plasma
(Carlson et al., 1960), with 15 to 70 percent (0.01-0.04 mg/L)
in the ionic form (Singer and Armstrong, 1964). Nearly 5
percent of plasma fluoride is bound to protein, but most of
the bound fluoride is associated with compounds having
molecular weights less than albumin. However, HF, not ionic
fluoride, apparently is the form that is in diffusion equilib-
rium across cell membranes. It is removed from circulation
by mineralized tissues in exchange for other anions such as
hydroxyl ion, citrate, and carbonate and subsequently enters
bone crystal lattice. Soft tissue fluoride levels are maintained
within narrow limits and are marginally affected by long-
term fluoride intake or by short-term fluctuations in plasma
levels. However, soft tissue fluoride is readily exchangeable
with extracellular fluid fluoride, as demonstrated by the rapid
distribution of '^F following intravenous injection (Wallace,
1953; Carlson et al., 1960). The rate of uptake of fluoride
into bones and teeth is most efficient during early develop-
ment stages. Approximately 50 percent of fluoride absorbed
each day is deposited in the calcified tissues (bone and de-
veloping teeth), which results in approximately 99 percent
of body burden of fluoride being associated with these tis-
sues (NRC, 1980). Excretion of fluoride occurs mainly via
the urine, which accounts for approximately 90 percent of
total excretion. Urinary excretion of fluoride is directly re-
lated to urinary pH; thus factors that affect urinary pH, such
as diet, drugs, metabolic and respiratory disorders, and alti-
tude residence, can affect how much absorbed fluoride is
excreted. Generally, > 20 percent of ingested fluoride is ex-
creted in feces.
Milk and saliva have fluoride concentrations similar to
plasma ionic fluoride levels, and variations in plasma fluo-
ride levels are reflected in these secretions. Milk fluoride
concentrations are affected only minimally by dietary fluo-
ride (Greenwood et al., 1964). Fluoride crosses the placental
barrier of cows, and fluoride levels in the bones of the off-
spring are correlated with those of maternal blood (NRC,
1974). However, bone fluoride concentration of calves born
to cows consuming as much as 108 mg F/kg diet (from so-
dium fluoride) were low (Hobbs and Merriman, 1962), and
it appeared that neither placental fluoride transfer nor milk
fluoride concentration were sufficient to adversely affect the
health of these calves.
Homeostatic regulation of plasma fluoride concentration
involves the kidneys and skeleton (Smith et al., 1950; Singer
and Armstrong, 1964). Bone has a great affinity to incorpo-
rate fluoride into hydroxyapatitite to form fluorapatite. This
results in larger, less soluble, more stable apatite crystals
(Zipkin et al., 1964). The fluoride cannot be removed with-
out resorption of this mineral unit. Even low levels of fluo-
ride intake will result in appreciable accumulation of fluo-
ride in the skeleton and teeth. These accumulations can
increase, within limits, over a period of time without mor-
phological evidence of pathology. However, in some cases
of high-fluoride intake, structural bone changes develop
(Shupe et al., 1963b). Most soft tissues do not accumulate
much fluoride, even during high intakes, although tendon
(Armstrong and Singer, 1970), aorta (Ericsson and Ullberg,
1958), and placenta (Gardner et al., 1952) have a higher
fluoride concentration than other soft tissues, possibly asso-
ciated with their relatively high levels of calcium and mag-
nesium. Kidney will usually exhibit a high fluoride concen-
tration during high fluoride ingestion due to urine retained in
the tubules and collecting ducts.
In laboratory animals and humans, approximately 99 per-
cent of fluoride is retained in bones and teeth (Kaminsky et
al., 1990; Hamilton, 1992), with the remainder distributed in
vascularized soft tissues and the blood (Mclvor, 1990). In
calcified tissues, the highest concentration is found in bone,
dentine, and enamel, and the concentration varies with age,
sex, and in different parts of the bone. During the rapid
growth phase at the early stages of development, a high por-
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FLUORINE
157
tion of fluorine is deposited in skeletal tissues. Retention of
fluorine in skeletal tissues is related to the turnover of miner-
als and previous exposure to this element (Carracio et al.,
1983). The selective affinity of fluoride for mineralized tis-
sues is, in the short term, due to uptake on the surface of
bone crystallites by the processes of isoionic and heteroionic
exchange. In the long run, fluoride is incorporated into the
crystal lattice structure of teeth and skeletal tissues by re-
placing some hydro xyl ions within the unit cells of hydroxya-
patite (Ca|g(P04)g(OH)2), producing partially fluoridated
hydroxyapatite (Ca|Q(P04)g(0H)^ ^-^F^^)-
Metabolic Interactions and Mechanism of Toxicity
The mechanism of fluorine toxicity is partially under-
stood, and the clinical manifestations of the toxicosis de-
pend on the age and species of animal, dosage, fonn and
duration of exposure to fluorine, and nutritional status. The
biochemical and clinical basis of acute fluorine toxicity has
been classified into four major categories: (1) enzyme inhibi-
tion, (2) calcium complex formation, (3) shock, and (4) spe-
cific organ injury (Hodge and Smith, 1981). Fluoride inhibits a
large number of metalloenzymes containing copper, manga-
nese, zinc, nickel, and iron (heme and non-heme) by binding
to the metal on the active site (reviewed by Messer, 1984;
Kirk, 1991). Enzymes requiring divalent cations (e.g., magne-
sium) are also inhibited, and in some instances inhibition of
fluoride ion is enhanced by inorganic phosphate (e.g., enolase,
succinic dehydogenase). Although the inhibition of enzyme
activities by fluoride toxicosis interrupts metabolic processes
such as glycolysis and synthesis of proteins (Kessabi, 1984),
the molecular mechanisms involved in these biochemical
processes are mainly speculative. Fluoride concentrations of
blood and tissues increase rapidly, and there is a severe hypo-
calcemia probably from inhibition of lactate required for
extrusion of Ca^"^ from bone (Hodge and Smith, 1981). The
mechanism of sudden death during acute toxicity may also
involve hyperkalemia or diminished Na+ZK-H-ATPase activity
affecting ATP production and causing glycolysis inhibition
(Messer, 1984).
Many of the biochemical actions of fluoride toxicity have
been explained in terms of its substitution for hydro xyl ions,
which the fluoride ions closely resemble in their physical
properties (hydration number, ion radius, and charge), par-
ticularly in mineralized tissues where the substitution results
in dissolution of minerals in bones. For enolase and pyro-
phosphatase, which have been examined in considerable de-
tail, the substitution of the fluoride ion for the hydroxyl ion
(that normally participates in this enzymatic reaction) results
in the formation of stable, less reactive complexes. Chronic
toxicosis occurs in extracellular fluid when the fluoride con-
centration is in the low micromolar range and includes both
inhibitory and stimulatory effects on cells that cannot readily
be explained in terms of biochemical effects (Messer, 1984;
Kirk, 1991).
SOURCES AND BIOAVAILABILITY
Fluoride is present in varying amounts in air, water, soil,
and in plant and animal tissues. Active volcanoes and fuma-
roles, as well as certain industrial processes, may contribute
significantly to local concentrations of fluoride. Fluoride
levels in surface water vary according to local geology and
proximity to emission sources. Fluoride concentrations in
surface freshwater range from 0.01 to 0.03 mg F~/L and the
range in seawater is 1.2 to 1.5 mg F-/L (EPA 1980; IPCS,
2002). Higher concentrations are found in areas where there
is geothermic and volcanic activity. In rivers, fluoride con-
centrations range from < 0.001 to 6.5 mg F~/L; the average
fluoride concentration is approximately 0.2 mg F~/L
(Fleischer et al., 1974). Fluoride levels may be higher in
lakes, especially in saline lakes and lakes in closed basins in
areas of high evaporation. The Great Salt Lake in Utah has a
fluoride content of 14 mg F~/L (Fleischer et al., 1974). The
fluoride content of ground water generally ranges from 0.02
to 1.5 mg/L (Fleischer, 1962; EPA, 1980). Highest fluoride
levels in U.S. ground water are generally found in the South-
west, and maximum ground water levels in Nevada, south-
ern California, Utah, New Mexico, and western Texas ex-
ceed 1.5 mg/L. In endemic fluorosis areas, deep-well water
may percolate through fluorapatite and frequently contains 3
to 5 mg F~/L, and sometimes 10 to 15 mg F~/L (Harvey, 1952;
Cholak, 1959). The amount of fluoride in water is influenced
by pH, water hardness, and the presence of clay that has ion-
exchange properties. In the Rift Valley of Kenya and Tanza-
nia, high fluoride levels in water and a high incidence of
fluorosis have been correlated with low levels of calcium
and magnesium in the water (Gaciri and Davies, 1993).
Industrial pollution furnishes airborne fluorine in one of
three principal forms: hydrofluoric acid, silicon tetrafluo-
ride, or fluoride-containing particulate matter. The average
fluorine concentrations in air are generally less than 0.1 pg/m-'
(IPCS, 2002) with higher concentrations in urban than rural
areas. Generally, the airborne fluorine contamination in ar-
eas located in the vicinity of industrial emissions does not
exceed 2 to 3 [ig/va^. Direct inhalation of fluoride does not
contribute significantly to fluoride accumulation in animals;
however, these emissions contaminate plants, soil, and wa-
ter. Gaseous fluorine may be absorbed and incorporated in
plant tissues. Particulate fluorides accumulate on plant sur-
faces and may be ingested by animals as the plant is eaten.
Rain may wash off some of these inert particles, but their
toxicity is related largely to their solubility in water.
Although soil is undoubtedly the principal source of fluo-
ride in plants, there is no consistent relationship between
total fluoride in soil and plants (NRC, 1974). Fluorine con-
tent of pastures and forages are particularly low unless they
have been contaminated by a deposition of dust and fumes
from volcanic and industrial origin or by fluoride-rich
geothermic and well water used for irrigation (Shupe, 1980).
Animals ingest soil during grazing, which may contribute to
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MINERAL TOLERANCE OF ANIMALS
more than 50 percent of the dietary fluorine in grazing sheep
and cattle, and this amount may increase to > 80 percent in
winter months (Cronin et al., 2000). There is some indica-
tion that acid soils promote fluoride uptake in plants, and
liming of these soils may reduce it. Fluoride content of soils
ranges from 20 to 1,000 mg total F7kg in areas without natu-
ral phosphate and fluoride deposits. Some soils unusually
high in fluoride have been found in Idaho (3,870 mg/kg) and
in Tennessee (8,300 mg/kg). The natural fluoride content of
the soil increases with increasing depth. Only 5 to 10 percent
of the total fluoride content in soil is soluble (Noemmik,
1953). The fluoride content increase with depth is in the
usual range in the United States, as 20 to 500 mg/kg (aver-
age, 190 mg/kg) from to 8 cm deep and 20 to 1,620 mg/kg
(average, 292 mg/kg) from to 30 cm deep (Robinson and
Edgington, 1946). The extent of fluoride retention depends
upon the amount of clay and pH, and the distribution at vari-
ous depths follows the clay pattern of soil. Several anthropo-
genic sources of fluoride can enrich soil, especially phos-
phate fertilizers, insecticides containing fluorides, and
emissions from industry. Soils may contain fluoride in sev-
eral different minerals.
Natural forage normally contains 2 to 20 mg F/kg dry
weight (NRC, 1974). Cereal grains and cereal by-products
usually contain 1 to 3 mg/kg (Underwood and Suttle, 1999),
which mainly accumulates in the outer layer and embryo
(Kumpulainen and Koivistoinen, 1977). The fluorine con-
tent of both leaf and root vegetables do not differ apprecia-
bly from those of cereals, with the exception of spinach,
which is rich in this element. The tea plant and camellia are
exceptions, and fluoride concentrations of 100 mg/kg or
more have been reported (Underwood and Suttle, 1999).
Fluorine is a normal component of calcified animal and fish
tissues. Animal by-products containing bone may contribute
significant quantities of fluoride to animal diets, depending
upon the amount of by-product used (and bone contained)
and the dietary history of the animals from which the by-
products were derived. Bone ash normally contains less than
1,500 mg F/kg and would contribute only minor amounts.
However, cattle grazing fluoride-contaminated pastures can
have bone ash containing over 10,000 mg/kg F. Aquatic or-
ganisms absorb fluoride to a limited extent from food sources
and directly from water where that uptake depends on fluo-
ride concentration, exposure time, and temperature (Hemens
and Warwick, 1972; Milhaud et al., 1981; Nell and Livanos,
1988). In natural environments, the proximity of anthropo-
genic sources, geology, physiochemical conditions, and food
source also influence fluoride content in fish, invertebrates,
and aquatic plants.
The primary sources of dietary fluorides for farmed ani-
mals are phosphorus supplements and feed ingredients of
animal origin. Phosphorus supplements greatly vary in their
fluoride content, depending on origin and manufacturing
processes. The majority of U.S. feed phosphate originates
from rock phosphate deposits, which contain 2 to 5 percent
(average, 3.5 percent) fluorine (vanWazer, 1961). When pro-
cessed sufficiently to qualify as defluorinated, feed-grade
phosphates must contain no more than 1 part of fluoride to
100 parts phosphorus (AAFCO, 2004). Processed low-fluo-
ride, feed phosphates include mono-, di-, and tricalcium
phosphates, mono- and diammonium phosphates, mono- and
disodium phosphates, ammonium and sodium poly-
phosphates, feed-grade phosphoric acid, and defluorinated
phosphate. Unprocessed feed phosphates, supplying substan-
tial amounts of fluoride, include soft rock phosphate, ground
rock phosphate, and ground low-fluoride rock phosphate.
More readily absorbed sources of fluoride, when incorpo-
rated in animal diets, are undefluorinated, fertilizer-grade
phosphates.
Fluoride levels in blood, urine, and feces are commonly
used to assess bioavailability and toxic levels of fluorine for
humans and animals from dietary sources; however, skeletal
tissue uptake has been used for experimental animal investi-
gations (Rao, 1984). Fluoride is readily absorbed from wa-
ter, but the absorption from diet may depend on the follow-
ing factors: concentration, source, chemical form (inorganic
or organic), other elements (Al, Ca, Mg, P, CI, S04^"), fluo-
rine exposure from other sources (water, air, etc.), and physi-
ological status (age, acid-base balance, disease, etc.). Soluble
forms of fluorine, such as sodium fluoride, are readily ab-
sorbed compared with bone meal, rock phosphate, and
defluorinated rock phosphate. Fluorine from dicalcium phos-
phate and raw rock phosphate was 50 percent as available as
fluorine from NaF (Clay and Suttle, 1985). The fluorine from
hay is available as NaF (Shupe et al., 1962).
Some reduction in fluorine absorption from diet may be
associated with insoluble complex formation between the
fluoride anion and multivalent cations in the alkaline envi-
ronment of the small intestine. Calcium and magnesium form
insoluble complexes with fluoride, which significantly de-
creases fluoride absorption (Cerklewski, 1997). Aluminium
also forms an insoluble complex with fluoride. Among the
anions, only chloride significantly influences fluoride
bioavailability. Diets low in chloride reduce fluorine excre-
tion and increase uptake in bone and teeth (Cerklewski,
1997). Fluoride absorption in laboratory animals increased
when either fat or protein were increased (McGown et al.,
1976; Boyde and Cerklewski, 1987).
TOXICOSIS
The toxicity of fluorine in animals via excessive fluoride
ingestion from water or from industrial exposure is referred
to as fluorosis, chronic fluorine toxicity, or fluorine toxico-
sis. The toxicosis is initially manifested as dental fluorosis
(mottled enamel) and, at higher levels of intake, skeletal fluo-
rosis. Several reviews have been published on fluoride tox-
icity in animals and humans (Krishnamachari, 1987;
Whitford, 1996; Kirk, 1991; Underwood and Suttle, 1999;
Cronin et al., 2000; ATSDR, 2003; Camargo, 2003; IPCS,
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FLUORINE
159
2002; McDowell, 2003). Table 14-1 summarizes some stud-
ies on the effects of fluorine exposure in animals.
Single Dose
The oral LDjg for fluorine varies among animal species
and also by gender. In rats, the following LD^q values or their
range (mg F"/kg body weight) have been reported for three
common fluoride supplements (DeLopez et al., 1976; Lim et
al., 1978; Whitford, 1990; ATSDR, 2003): sodium fluoride,
31 to 101; sodium monofluorophosphate, 75 to 102; and stan-
nous fluoride, 45.7. For mice, LD^q values reported were 44.3;
58, 54, and 94; and 25.5 and 3 1 .2 for sodium fluoride, sodium
monofluorophosphate, and stannous fluoride, respectively
(Lim et al., 1978; ATSDR, 2003). The predominant signs of
toxicosis in these animals upon administration of a single large
oral dose of fluoride were nausea, salivation, lacrimation,
vomiting, diarrhea, respiratory arrest, tetany, and coma. Intra-
peritoneal injection (13.6 and 21.8 mg F"/kg BW) of sodium
fluoride into female rats caused proximal tubular necrosis and
marked changes in kidney weight, urine osmolarity and pH,
and chloride excretion; however, these effects were less severe
in the younger animals (Daston et al., 1985). When sodium
fluoride solutions (1 to 50 mmol ¥^fL dissolved in 0. 1 N HCl)
were introduced in the stomach of rats, several histopathologi-
cal changes in the gastrointestinal tract (hemorrhage, disrup-
tion of epithelial integrity and glandular structure, lysis, and
loss of epithelial cells) were observed (Easmann et al., 1984,
1985).
The inhalation exposure of rats, mice, and guinea pigs to
fluorine gas (F,) and HF causes severe ocular and nasal irri-
tation, pulmonary congestion, edema, respiratory distress,
and erythraemia of exposed skin (ATSDR, 2003). Fluorine
is more toxic than HF (Stokinger, 1949; Keplinger and
Suissa, 1968). For rats, LC^q values (mg F"/m-^) ranging from
4,065 to 14,400 have been reported for 5-minute exposure
(WHO, 1984; ATSDR, 2003) and 1,084 for 60-minute expo-
sure to HF (Rosenholtz et al., 1963). The LC^q for mice were
approximately 5,000 and 280 when exposed to HF for 5 and
60 minutes, respectively (WHO, 1984; ATSDR, 2003).
Direct exposure of the skin to hydrofluoric acid produces
severe burns and tissue damage depending upon the concen-
tration and the length of the exposure (Derelanko et al.,
1985). In rats, direct application of aqueous solution of so-
dium fluoride (0.5 and 1.0 percent) to the abraded skin
caused necrosis, edema, and inflammation (Essman et al.,
1981).
Acute
Acute fluoride toxicosis is rare. It usually results from the
accidental ingestion of compounds such as sodium
fluorosilicate (NaiSiFg), used as a rodenticide, or sodium
fluoride, used as an ascaricide in swine. The rapidity with
which toxic signs appear depends on the amount of fluoride
ingested (Cass, 1961). Toxic signs include high fluoride con-
tent of blood and urine, restlessness, stiffness, anorexia, re-
duced milk production, excessive salivation, nausea, vomit-
ing, urinary and fecal incontinence, chronic convulsions,
necrosis of gastrointestinal mucosa, weakness, severe de-
pression, and cardiac failure (Shupe et al., 1963a,b). Death
occurred within 12 to 14 hours in dairy cows after ingesting
sodium fluorosilicate (Krug, 1927). Acute fluoride toxicosis
also occurred in cattle after exposure to wood treatment com-
pounds used on utility poles (Bischoff et al., 1999). The pre-
dominant systematic effects of acute oral exposure to so-
dium fluoride in humans and laboratory animals include
hypocalcemia, hyperkalemia, and gastrointestinal pain
(ATSDR, 2003).
Chronic
Chronic skeletal fluorosis is prevalent in cattle, sheep,
goats, horses, and humans in parts of India, Argentina, Aus-
tralia, Turkey, Africa, the United States, and other regions of
the world (Underwood, 1981; WHO, 1994), often due to
consumption of water high in fluoride. The degree to which
inorganic fluoride induces skeletal changes varies consider-
ably in farm animals. Cattle are most sensitive to fluorosis,
followed by sheep, horses, pigs, rabbits, rats, guinea pigs,
and poultry (Franke, 1989). Young animals are most affected
by fluorosis. The dietary concentration at which fluoride in-
gestion becomes harmful in farm animals is not clearly de-
fined. Diagnosis of fluoride toxicosis at low levels of inges-
tion is difficult because there is an extended interval of time
between ingestion of elevated levels and the appearance of
toxic signs (Shupe, 1970). Low-level toxicosis also depends
upon solubility of the fluoride source, general nutritional sta-
tus, species of animal, age when ingested, and dietary com-
ponents that modify toxicity.
Both domestic and wild grazing animals also develop
chronic fluorosis due to contamination with volcanic gas and
ash (Roholm, 1937; Araya et al., 1990; Shanks, 1997), inges-
tion of commercial phosphorus supplements (Shupe et al.,
1992; Jubb et al., 1993; Singh and Swarup, 1995), phosphate
fertilizer residues (Clark and Stewart, 1983), forage or water
polluted with industrial emissions (Kay et al., 1975; Singh and
Swarup, 1995; Kierdorf et al., 1996), and drinking water from
ground and geothermal sources that are rich in fluoride
(Harvey, 1952; Shupe et al., 1984; Botha et al., 1993).
The effect of fluorine toxicosis generally takes weeks or
months to become manifest and some of the excess fluorine
is excreted in urine (Underwood and Suttle, 1999). Plasma
fluoride concentrations reflect short-term changes in fluo-
rine uptake with levels of < 0. l|Jg g"' in normal animals and
1 \ig g"' indicating a high fluorine uptake (Suttie et al., 1972).
The skeleton of animals normally contains the greatest pro-
portion of fluorine within the animal and the normal whole
bone fluorine concentration ranges between 300 and 600 |ig
g"' (dry fat-free basis), the highest concentration being
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MINERAL TOLERANCE OF ANIMALS
within the cancellous bones such as rib and vertebrae
(Underwood and Suttle, 1999). In ruminants, teeth contain
approximately half the fluorine concentration of bone
(Underwood and Suttle, 1999). The period during which
developing teeth in cattle are sensitive to excess fluoride is
from approximately 6 months to 4 years of age. Teeth that
have erupted are not influenced adversely by subsequent
fluoride ingestion (Garlick, 1955), and cattle that are more
than 3 years old will not develop typical dental lesions. Den-
tal fluorosis is generally diagnosed by examining the inci-
sors. Gross fluoride lesions of the incisor enamel begin with
inside mottling (white, chalky patches or striations) and
progresses to defined mottling, hyperplasia, and
hypocalcification. A scoring system for classification of den-
tal fluorosis has been proposed (NRC, 1974).
The amount of fluoride stored in bone may increase over
time with no apparent change in bone structure or function.
However, if excess fluoride ingestion is sufficiently high,
and occurs over a sufficiently long period of time, morpho-
logical abnormalities will develop. In livestock, clinically
palpable (bilateral) lesions usually develop first on the medi-
cal surface of the proximal third of the metatarsals. Subse-
quent lesions are seen on the mandible, metacarpals, and ribs.
Osteofluorotic lesions tend to be more severe in those bones,
and parts of the bones, that are subject to greatest physical
stress. Radiographic evidence of osteoporosis, osteosclero-
sis, osteomalacia, hyperostosis, and osteophytosis or any
combination of these lesions has been described (Johnson,
1965; Shupe and Alther, 1966; Shupe, 1969). Grossly, se-
verely affected bones appear chalky white, are larger in di-
ameter, and heavier than normal, and they have a roughened,
irregular periosteal surface. In cattle poisoned by industrial
fluoride emissions, Krook and Maylin (1979) suggested that
the primary target of fluoride was the resorbing osteocyte.
Morphological signs of osteolysis were absent, and the fail-
ure of resorption caused osteopetrosis with retention of
lamellar bone in cortices.
Animal movement may be impaired by intermittent peri-
ods of stiffness and lameness, associated with advanced ar-
eas with calcification of particular structures and tendon in-
sertions. In animals with marked periosteal hyperostosis,
spurring and bridging of the joints may lead to rigidity of the
spine and limbs. Anorexia, unthriftiness, dry hair, and thick,
nonpliable skin have been noted in fluorotic animals
(Roholm, 1937; Shupe et al., 1963b).
Primary adverse effects on reproduction and lactogenesis
have not been demonstrated although milk production may
decrease with high fluoride intake, secondary to dental and
skeletal damage and consequent reductions in feed and wa-
ter intake (Stoddard et al., 1963). Suttle et al. (1957b) have
demonstrated that cows first exposed to fluoride at 4 months
of age can consume 40 to 50 mg/kg of fluorine as sodium
fluoride in their diet for two or three lactations without a
measurable effect on milk production. Milk production was
reduced in the fourth and subsequent lactations. Higher di-
etary fluoride levels (93 mg/kg) affected the milk production
in the second lactation slightly and definitely reduced milk
yield in a subsequent lactation (Stoddard et al., 1963). Irre-
spective of level or duration of fluoride intake, clinical signs
of toxicosis will normally precede impaired milk produc-
tion. No characteristic, unequivocal histological or func-
tional changes in blood or soft tissues have been correlated
with fluoride intakes sufficient to induce chronic fluorosis of
bones and teeth.
Natural surface waters are often contaminated with fluoride
from discharges of fluoridated municipal waters, fertilizers, and
other industrial pollutants that cause ecological risk to aquatic
organisms and plants. In certain areas, high concentrations ( 10
mg F^VL) have been measured in rivers (CEPA, 1993;
Camargo, 1996). Aquatic organisms accumulate soluble inor-
ganic fluorides. When sodium fluoride was released into an
experimental pond, within 24 hours the concentration of fluo-
ride in aquatic vascular plants increased 35 -fold and a signifi-
cant increase in its uptake was observed in algae (14-fold),
molluscs (12-fold), and fish (7-fold) (Kudo and Garrec, 1983).
Limited data on the toxicity of fluorine in freshwater to algae,
aquatic plants, invertebrates, and fish are available (reviewed
by Camargo, 2003). Aquatic plants can effectively remove fluo-
ride from contaminated water, and the concentration increases
with exposure time. The toxicity is linked to fluoride ions that
affect nucleotide and nucleic acid metabolism that influences
algal cell division (Antia and Klut, 1981). Some algae can toler-
ate inorganic fluoride levels as high as 200 mg/L (Antia and
Klut, 1981; Camargo, 2003). Fluoride toxicity in aquatic inver-
tebrates and fish increases with increasing fluoride concentra-
tions, exposure time, and water temperature. Marine inverte-
brates appear to be more tolerant to toxicity than freshwater
species (reviewed by Camargo, 2003). Fluorine accumulates in
the exoskeleton of invertebrates and bones of fish. The LCjq
values (mg F"/L) of several fish at different exposure times
range from 5 1 to 460 (Camargo, 2003). In soft water with low
ionic content, a fluoride concentration as low as 0.5 mg F"/L
produces toxicosis in invertebrates and fish. Among fishes, rain-
bow trout have been used widely to study fluoride toxicity. In
addition to water temperature, calcium and chloride content of
water and body size also affect the fluorine toxicity.
In humans, the major toxic effects range from dental fluo-
rosis (Fejerskov et al., 1977; DenBesten and Thariani, 1992),
reversible gastric disturbances (Jowsey et al., 1979), and
lower urinary concentrating ability (Goldemberg, 1931;
Whitford and Taves, 1973) to skeletal fluorosis (Singh and
Jolly, 1970) and death (Hodge and Smith, 1965; Church,
1976; Dukes, 1980;Eichleretal., 1982; Gessner et al., 1994).
Reproduction
The adverse effects of high levels of fluoride intakes on
reproduction of several laboratory animal species have been
reported (IPCS, 2002). Reproductive function was severely
affected in female mice orally administered >5.2 mg F/kg
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FLUORINE
161
BW/day after mating (Pillai et al., 1989), and in male rabbits
orally administered 9.1 mg F/kg BW/day for 30 days
(Chinoy et al., 1991). Histopatliological changes have also
been observed in testes of male rabbits fed 4.5 mg F/kg
BW/day for 18 to 29 months (Susheela and Kumar, 1991)
and male mice fed 4.5 mg F/kg BW/day for 30 days (Chinoy
and Sequeira, 1989a,b) and in ovaries of female rabbits in-
jected subcutaneously with 10 mg F/kg BW for 100 days
(Shashi, 1990). Exposure of dams to 150 mg/L fluorine in
drinking water prior to breeding and during pregnancy and
lactation had no adverse effects on the bones of developing
rats (Ream et al., 1983a), although effects on the bones of
the dams were observed (Ream et al., 1983b). The lowest-
observable-effect-level (LOEL) of dams was considered to
be 21.4 mg/kg BW/day. In most studies, the fluoride con-
centrations associated with adverse effects were much higher
than those measured in drinking water or animal feeds. The
apparent threshold concentration for inducing reproductive
effects in animals in drinking water has been listed by NRC
(1993): 100 mg/L for mice, rat, foxes, and cattle; 100-200
mg/L for mink, owls, and kestrels; and >500 mg/L for
hens.
Genotoxicity and Carcinogenicity
The genotoxicity of fluoride has been examined in a large
number of in vitro and in vivo assays (WHO, 1984; Li et al.,
1987; Tong et al., 1988; Zeigler et al., 1993; IPCS, 2002).
Generally, fluoride is not mutagenic in microbial cells, but
increases the frequency of gene-locus mutations in cultured
mammalian cells and induces the morphogenic transforma-
tion of Syrian hamster embryo cells at cytotoxic concentra-
tion in vitro. Although the results of some studies have indi-
cated that sodium fluoride increases unscheduled DNA
synthesis in mammalian cells, these results were not con-
firmed when steps were taken to eliminate potential artifacts
(i.e., formation of precipitable complexes of magnesium
fluoride and pH] thymidine). Sodium fluoride has been con-
sidered capable of inducing chromosomal aberrations, mi-
cronuclei, and sister-chromatid exchanges in vitro in mam-
malian cells; however, the results from these studies were
not consistent. Chromosal aberrations have not been detected
in cells exposed in vitro to levels of fluoride less than 10 [igl
mL, which is considered as a threshold for the clastogenic
activity of fluoride.
The results of early carcinogenicity bioassays conducted
with NaF administered in water were largely negative. How-
ever, the documentation and protocols of these studies were
inadequate according to current bioassay techniques and thus
of limited value. Although several carcinogenicity bioassays
have been conducted in recent years, the results of two stud-
ies were selected to be reliable by NRC (1993). The National
Toxicological Program (NTP, 1990) administered 175 mg
F/L in drinking water to male and female mice. Although
results were negative, there was some evidence of a dose-
related increase in the incidence of osteosarcomas in male
rats. These results were not confirmed by another study con-
ducted by Procter and Gamble (Maurer et al., 1990) in which
fluorine in the diets was at doses higher than those in the
NTP study. The later study did produce significant dose-
related incidence of osteomas (benign bone tumors) in male
and female mice. The available laboratory animal experi-
mental data are insufficient to demonstrate a carcinogenic
effect of fluorine (NRC, 1993).
Factors Influencing Toxicity
Toxicity of fluoride, at a given level of exposure, depends
on animal species, source, concentration, chemical form (in-
organic or organic), other elements, and physiological status
(age, acid-base balance, disease, etc.) of the animal. Fluo-
ride is readily absorbed from water; therefore, the toxicity of
soluble fluoride compounds will depend on their water solu-
bility. Based on the skeletal accumulation of fluoride by rats,
Hobbs et al. (1954) ranked the toxicity of fluoride com-
pounds in the order from highest to lowest as follows: rock
phosphate, natural and synthetic cryolite, calcium and mag-
nesium fluosilicates, and calcium fluoride. Fluoride in rock
phosphate was considerably less toxic to beef heifers than
that in sodium fluoride (Hobbs and Merriman, 1962). Natu-
rally fluorinated water produced toxicity comparable to equal
amounts of fluoride from sodium fluoride added to water
(Wagner and Muhler, 1957) or to a dry diet (Harvey, 1952;
Wuthier and Phillips, 1959). Variations in fluoride intake,
with alternate periods of high and low exposure, were more
damaging to young cattle than were constant intakes of the
same amount (Suttie et al., 1972).
Some dietary components that have been shown to re-
duce fluoride toxicosis include aluminum, calcium, magne-
sium, phosphorus, sodium chloride, boron, and sulfates
(NRC, 1980; Krishnamachari, 1987). Calcium given orally
or intravenously counteracts the effects of fluoride, particu-
larly toxicity of an acute nature (Krishnamachari, 1987).
Feeding of calcium carbonate, aluminum oxide, or alumi-
num sulfate reduces absorption of fluoride and may control
chronic fluorosis under some conditions. However, the con-
sumption of a combination of aluminum sulfate with cal-
cium carbonate in a mineral mixture was not effective in
reducing bone fluoride accumulation in cattle grazing in a
fluoride-contaminated pasture (Allcroft and Burns, 1968).
Aluminum compounds may also adversely affect dietary
phosphorus retention (Street, 1942; Hobbs et al., 1954;
Alsmeyer et al., 1963; Storer and Nelson, 1968); if they are
used to alleviate fluoride toxicosis, increased levels of phos-
phorus must be fed. Aluminum chloride and aluminum ac-
etate also appear to be effective in reducing fluorosis in
cattle, but aluminum oxide produces only slight alleviation
(Hobbs et al., 1954). For chickens, free-choice access to di-
etary aluminum sulfate at 800 mg Al/kg completely pre-
vented toxicity of 1,000 mg F/kg; the oxide form was not
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MINERAL TOLERANCE OF ANIMALS
effective (Cakir et al., 1978). Aluminum seems to reduce the
gastrointestinal absorption of fluoride.
High intakes of boron have been shown to be an effective
antidote to fluoride toxicosis in rabbits (Baer et al., 1977;
Elsair et al., 1980), pigs (Seffner and Teubener, 1983), and
sheep (Wheeler et al., 1988). Boron may induce formation of
a complex, BF^, which is excreted in the urine. Magnesium
metasilicate has been tested in chronic fluorosis patients, who
responded with partial clinical amelioration of their signs (Rao
et al., 1975). Toxicity of fluorine is also affected by dietary fat
level, probably due to its effects on absorption of this element.
Increase in the level of dietary fat from 5 to 15 or 20 percent
enhanced the growth-retardation effect of high fluorine intake
in rats (Miller and Phillips, 1953; Buttner and Muhler, 1958)
and chickens (Bixler and Muhler, 1960). Fluorine, in the pres-
ence of fat, causes delayed gastric emptying, which may ac-
count for the increased toxicity of fluorine in rats fed high-fat
diets (McGown et al., 1976).
TISSUE LEVELS
The concentrations of fluorine in bone, tissues, blood,
eggs, and milk vary with fluorine intakes from water and
diet (NRC, 1980). Mineralized tissues contain approximately
99 percent of total body fluorine, with a major proportion
concentrated in bone. The skeleton of animals normally con-
tains the highest proportion of fluorine, with normal bone
having ranges from 0.3 to 0.6 mg F/g of dry tissue on a fat-
free basis (Underwood and Suttle, 1999). The fluorine con-
centration in the soft tissues is relatively low and changes
little with age. Kidneys contain higher levels of fluorine than
other tissues partly due to urine retained in this organ. Nor-
mal fluorine levels (|Jg/g, dry matter basis) of cow and sheep
in the following soft tissues have been reported (Harvey,
1952; Suttie et al., 1958): liver, 2.3 and 3.5; kidney, 3.5 and
4.2; thyroid, 2.1 and 3.0; and heart, 2.3 and 3.0. Dairy cows
fed a ration supplemented with 50 pg F/g as NaF for 5.5
years only increased the levels in heart, liver, thyroid, and
pancreas 2- to 3-fold above 3 |Jg/g found in tissues of normal
cows (Suttie et al., 1958). In normal cow's milk, fluorine
levels range from 0.01 to 0.4 (ig/g (Suttie et al., 1957b;
Bergmann, 1995), whereas fluorosis can occur in cattle when
levels reach 0.64 |jg/g (Suttie et al., 1957b).
Plasma fluoride concentrations are maintained within nar-
row limits by regulatory mechanisms involving skeletal tis-
sues. In cattle, the plasma fluorine concentration is less than
0.1 [Jg/g in normal animals and 1 pg/g indicates a high fluo-
rine uptake from diet (Suttie et al., 1972). The fluorine con-
centration in plasma of healthy humans ranges from 7.6 to
28.5 pg/L (Guy, 1979) and values as high as 106 ± 76 mg/L
in adults exposed to 5.03 mg F/L in drinking water have
been reported (Li et al., 1995). Elevated intakes of fluoride
also result in an increased concentration of fluoride in urine
and bone. In several long-term experiments with beef and
dairy cattle, the skeletal concentration of fluorine was ap-
proximately proportional to the concentration of NaF (NRC,
1974). Urine fluoride levels are approximately correlated
with dietary intake, although the duration of fluoride inges-
tion, sampling time, and total urinary output will introduce
variation. With excess ingestion of fluorine, urinary levels
increased from 15 to 30 mg/L to an upper limit of 70 to 80
mg/L (Suttie and Kolstad, 1977). The following urine con-
centrations indicate fluorine status of cattle: normal, <5 mg
F/L; borderline toxicity, 20 to 30 mg F/L; systematic toxic-
ity, >35 mg F/L (McDowell, 2003).
Birds fed high-fluoride diets accumulate fluorine in their
eggs, particularly in yolk. The fluorine content of normal
chicken eggs increased from 0.8 to 0.9 |Jg/g to as high as 3
|jg/g with an increase in dietary rock phosphate concentra-
tion (Phillips et al., 1935). Generally the fluorine in deboned
poultry meat is low (0.2 mg/kg), but higher values in the
range of 0.3 to 2.7 mg/kg in chicken and turkey meat have
been reported (Jedra et al., 2001). Fluoride is mainly con-
centrated in skeletal tissues of fish and exoskeletons of in-
vertebrates. In freshwater and marine fish muscle, it ranges
from 0.6 to 26 mg/kg wet weight (Lall, 1994; Camargo,
2003) and in whole fish, from 10 to 60 mg/kg (Soevik and
Braekkan, 1981). The average amount in the edible part of
muscle is 0.8 mg F/kg, but small bones retained in fish
muscle can affect the fluorine content (Lall, 1994). Fluorine
in the muscle of crab, shrimps, and prawn from the North
Sea varies from 1 to 4 mg/kg (Soevik and Braekkan, 1981).
Antarctic krill contains exceptionally large amounts of fluo-
rine (mg/kg dry weight): whole animal, 1,000; muscle, 70;
and exoskeleton, 2,000. The concentrations of fluoride in
the body of wild invertebrates consumed by fish have ranged
from 7 to 3,500 mg/kg (Camargo, 2003). The consumption
of these organisms could have a significant effect on the
fluorine content of fish tissues.
HUMAN HEALTH
Fluorine is considered a hazardous substance with inges-
tion of large doses of this element in either food or water or
both. Fluoride consumed from water and beverages accounts
for more than 70 percent of total fluoride intake, because
most animal meat, milk, and eggs contain less than 30 |ig F/
100 g (Table 14-2). Regular consumption of marine fish and
crustaceans can significantly increase fluoride intake. The
drinking water in many parts of the world is naturally rich in
fluoride, which causes local inhabitants to develop endemic
fluorosis. Several reviews related to the risk of chronic fluo-
ride toxicity to humans have been published (Kaminsky et
al., 1990; USPHS Ad Hoc Subcommittee on Fluoride, 1991;
NRC, 1993; Whitford, 1996; IPCS, 2002; ATSDR, 2003).
MAXIMUM TOLERABLE LEVELS
The tolerance levels for domestic animals are based on
clinical signs of fluoride toxicosis, and most of the values
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FLUORINE
163
were obtained before 1980. While small intakes of fluoride
may be beneficial or even essential, prolonged intakes of
oral fluoride concentrations above these maximum tolerable
levels may result in reduced performance. The tolerable lev-
els are based on tolerances to sodium fluoride or other fluo-
rides of similar toxicity (fluoride in certain phosphorus
sources appears to be less toxic) and assume that the diet is
essentially the sole source of fluoride. When water also con-
tains appreciable fluoride (> 3 mg/L), these dietary levels
should be reduced. The maximum fluoride levels for young
beef or dairy calves and heifers are 35 and 40 mg/kg of diet,
respectively; for animals kept for breeding, 30 to 40 mg/kg
of diet for heifers; and for mature animals, 40 to 50 mg/kg of
diet. Long-term studies (approximately 7 years) conducted
with young calves showed that 30 mg F/kg diet caused ex-
cessive staining of teeth (Hobbs and Merriman, 1959; Shupe
et al., 1963b). Minor morphological lesions may be seen in
cattle teeth when dietary fluoride during tooth development
exceeds 20 mg/kg, but a relationship between these lesions
and animal performance has not been established.
Mature dairy cattle consume more feed in relation to body
weight than mature beef cattle, so maximum recommended
concentrations of dietary fluoride are 40 mg/kg for dairy
cattle and 50 mg/kg for beef cattle. Lifetime fluoride expo-
sure for finishing cattle is less than for breeding cattle, so the
maximum tolerable level for this productive class is esti-
mated at 100 mg/kg. Excessive exposure during tooth devel-
opment in cattle may result in exaggerated tooth wear, im-
paired mastication, and sensitivity to cold drinking water.
Maximum tolerable levels for other species are based on rela-
tively limited published data in some cases, and the level of
40 mg F/kg for horses and rabbits represents an estimate.
Levels for lifetime exposure for sheep, swine, and poultry
are less than that for cattle and horses. Poultry are relatively
less sensitive to fluoride. The maximum tolerable levels are
150, 150, and 200 mg F/kg for swine, turkeys, and chicken,
respectively. Sheep raised for lamb or wool can tolerate 60
mg F/kg diet, and finishing lamb can tolerate up to 150 mg
F/kg diet (NRC, 1980).
Studies on laboratory species under a wide range of ex-
perimental design have been summarized by CEP A (1993)
and IPCS (2002), and the NOAEL and the LOAEL are as
follows (mg of F/kg of BW/day): rats, 1.8-12.7, 3.2-12.8;
and mice, 2.7-9.1,4.5-5.7. The estimated average safe con-
centrations (infinite hour LCg Q^ values) of fluoride for fry
(8-10 cm) of rainbow trout and brown trout in soft water
(21.2-22.4 mg CaCOj/L) were 5.14 (range 3.10-7.53) and
7.49 (range 4.42-10.96) mg F-/L, respectively (EPA, 1986;
Lee et al., 1995). A fluoride concentration of 0.5 mg F"/L is
considered safe for freshwater upstream migrating salmon
inhabiting soft water of low ionic content and 1-1.5 mg F"/L
in hard water with high ionic content (Camargo and La
Point, 1995; Camargo, 1996).
The LCjQ values of fluoride for freshwater, brackish, and
marine invertebrates at different stages of development, ex-
posure time, and temperature have ranged from 10.5 to 308
F"/L. However, the safe concentration (infinite hour LCqqj
values) of fluoride for many species in soft freshwater is in
the range of 0.5 mg F"/L (Camargo, 2003).
The lethal dose (LDjqq) of sodium fluoride in an average
human adult has been estimated between 5 and 10 g (32 to
64 mg of F/kg BW) (WHO, 1984; Whitford, 1990). The tol-
erable upper intake level of fluorine ranges from 0.7 to 2.2
mg/day for children to 10 mg/day for adult men and women
(NRC, 1993), approximately 2- to 3-fold higher than the rec-
ommended dietary allowance. The EPA derived an oral ref-
erence dose (RFD) of 0.06 mg/kg/day for fluorine (ATSDR,
2003) that was based on a NOAEL of 0.06 mg of F/kg of
BW/day and the LOAEL of 0.12 mg of F/kg of BW/day
from data on fluorosis in children. The maximum amount of
fluoride allowed by EPA in drinking water is 4 mg/L.
FUTURE RESEARCH NEEDS
The beneficial effects of fluoride on dental health of
farmed and laboratory animals and humans have been known
for more than 60 years; however, the exact biochemical
mechanisms to qualify fluorine as an essential trace element
remain to be established. Numerous publications describe
the effects of fluorine supplementation (in some cases, phar-
macological dose) that include prevention of dental caries or
osteoporosis. As well, the amelioration of anemia and fertil-
ity in experimental animals has been reported; however, the
biochemical mechanisms remain unclear. The potential haz-
ard of fluoride on farm animals by ingestion of phosphate
fertilizers, volcanic ash, and industrial wastes is likely to
continue and it will affect terrestrial and aquatic animal pro-
duction. Research is needed to establish the risk of fluorine
toxicity in pastoral systems and aquaculture, as well as to
develop sustainable strategies for the future. The impact of
human activities — such as aluminum smelters, discharges of
municipal waters, and industries manufacturing brick, ce-
ramics, glass, and chemicals containing fluorides — are caus-
ing significant increases in the fluoride concentration of sur-
face waters. Despite detennining the safe levels of fluoride
for certain aquatic organisms, there are limited data on
bioaccumulation in the edible portion of fish and shellfish.
SUMMARY
Fluorine is present as fluoride in igneous and sedimentary
rock. Most plants have a limited capacity to absorb fluoride
from the soil; however, animals may consume significant
quantities from contaminated surface waters, deep-well
water percolating through fluorapatite; forages contaminated
by fluoride-bearing dusts, fumes, or water; animal by-prod-
ucts containing bone high in fluoride; and a variety of inor-
ganic phosphate supplements. Animals normally ingest low
levels without harm, and small amounts of fluoride may be
beneficial and perhaps even essential. Ingestion of excessive
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164
MINERAL TOLERANCE OF ANIMALS
fluoride chronically induces characteristic lesions of the skel-
eton and teeth, resulting in intermittent lameness, excessive
tooth wear, reduced feed and water intake, and decreased
weight gain and milk production. Developing teeth and bone
are particularly sensitive, and excessive exposure in early
postnatal life is especially damaging. Other disorders caused
by acute fluorine toxicosis in animals and/or humans include
gastrointestinal irritation, severe cardiac effects (e.g., tetany,
cardiovascular collapse, ventricular fibrillation), and paren-
chymal liver degeneration. In general, those fluoride com-
pounds that are most soluble are most toxic. Aquatic organ-
isms absorb fluorine from their diet and surrounding water
and accumulate it in skeletal tissues. Toxicity data are avail-
able for terrestrial and aquatic animals; however, oral maxi-
mum tolerable levels for fish are not established.
REFERENCES
AAFCO (Association of American Feed Control Officials). 2004. Official
Publication of the Association of American Feed Control Officials, Inc.
West Lafayette, IN.
Abdelhamid, A. M., and T. M. Dorra. 1993. Effects of feedborne fluorine
intoxication on broiler chiciis' performance. Biochem. Physiol. Path.
42:133-145.
Allcroft, R., and K. N. Burns. 1968. Fluorosis in cattle in England and
Wales: incidence and sources. Fluoride 1:50-53.
Alsmeyer, W. L., B. G. Harmon, D. E. Becker, A. H. Jensen, and H. W.
Norton. 1963. Effects of dietary Al and Fe in phosphorus utilization. J.
Anim.Sci. 22:1116-1123.
Anderson. J. O., J. S. Hurst, D. C. Strong, H. M. Nielsen, D. A. Greenwood,
W. Robinson, J. L. Shupe, W. Binns, R. A. Bagley, and C. I. Draper.
1955. Effect of feeding various levels of sodium fluoride to growing
turiteys. Poult. Sci. 34:1147-1153.
Anke, M., H. Gurtler, M. Glei, S. Anke, M. Jaritz, H. Freytag, and V.
Shafter. 1997. Effects of fluoride poor diets in generation of goats. Pp.
192-194 in ftoceedings of the Ninth Symposium on Trace Elements in
Man and Animals. P. W. F. Fischer, M. R. L'Abbe, K. A. Cockell, and
R. S. Gibson, eds. Ottawa: NRC Press.
Antia, N. J., and M. E. Klut. 1981. Fluoride addition effects on euryhaline
phytoplankter growth in nutrient-enriched seawater at an estuarine level
of salinity. Bot. Mar. 24:147-152.
Araya, O., F. Wittwer, A. Villa, and C. Ducom. 1990. Bovine fluorosis fol-
lowing volcanic activity in the southern Andes. Vet. Rec. 126:641-642.
Armstrong, W. D., and L. Singer. 1970. Distribution in body fluids and soft
tissues. Pp. 94—104 in Fluorides and Human Health. Geneva: World
Health Organization.
ATSDR (Agency for Toxic Substances and Disease Registry). 2003. Toxi-
cological profile for fluorides, hydrogen fluoride and fluorine. Atlanta,
GA: U.S. Department of Health and Human Services. Available at http://
www.atsdr.cdc.gov/toxprofiles/tpl 1. html. Accessed on April 4. 2005.
Baer, H. P., R. Bech, J. Franke, A. Grunewald, W. Kochmann, F. Melson,
H. Runge, and W. Wiedner. 1977. Ergebnisse tierexperimenteller
Untersuchungen an Kaninchen mit Natriumfluorid unter Einwirkung
von Gegenmitteln. Z. Gesamte Hyg. Grenzgeb. 23:14—20.
Bergmann, R. 1995. Fluorid in der Ernahrung des Menschen. Biologische
Bedeutung fiir den wachsenden Organismus. Habilitationsschrift. Ber-
lin: Virchow-Klinikum der Humboldt-Universitat, 133 pp.
Bischoff, K., W. C. Edwards, and J. Fearer. 1999. Acute fluoride toxicosis
in beef cattle. Bovine Pract. 33(1): 1-3.
Bixler, D., and J. C. Muhler. 1960. Retention of fluoride in soft tissues of
chicken receiving different fat diets. J. Nutr. 70:26-30.
Botha. C. J., T. W. Naude, P. P. Minnaar, S. R. Van Amstel, and S. D. Janse
Van Rensburg. 1993. Two outbreaks of fluorosis in cattle and sheep. J.
S. Afr. Vet. Assoc. 64:165-168.
Boyde, C. D., and F. L. Cerklewski. 1987. Influence of type and level of
dietary protein on fluoride bioavailability in the rat. J. Nutr. 1 17:2086—
2090.
Bunce, G. E., Y. Chiemchaisri, and P. H. Phillips. 1962. The mineral re-
quirements of the dog. IV. Effect of certain dietary and physiologic
factors upon the magnesium deficiency syndrome. J. Nutr. 76:23-29.
Burke, W. J., U. R. Hoegg, and R. E. Phillips. 1973. Systemic fluoride
poisoning resulting from a fluoride skin burn. J. Occup. Med. 15:39^1.
Burns. K. N., and R. Allcroft. 1964. Fluorosis in cattle. 1. Occurrence and
effects in industrial areas of England and Wales, 1954—57. In Animal
Disease Surveys Report No. 2, Ministry of Agriculture, Fisheries and
Food. London: Her Majesty's Stationary Office, 51 pp.
Buttner, W., and J. C. Muhler. 1958. The retention of fluoride by the skel-
eton, liver, heart and kidney as a function of dietary fat intake in the rat.
J. Nutr. 65:259-266.
Cakir, A., T. W. Sullivan, and F. B. Mather. 1978. Alleviation of fluorine
toxicity in starting turkeys and chicks with aluminum. Poult. Sci.
57:498-505.
Camargo, J. A. 1996. Comparing levels of pollutants in regulated rivers
with safe concentrations of pollutants for fishes: a case study. Chemo-
sphere 33:81-90.
Camargo, J. A. 2003. Fluoride toxicity to aquatic organisms: a review.
Chemosphere 50:251-264.
Camargo, J. A., and T. W. La Point. 1995. Fluoride toxicity to aquatic life:
a proposal of safe concentrations for five species of Palearctic freshwa-
ter invertebrates. Ai'ch. Environ. Contam. Toxicol. 29:159-163.
Camargo, J. A., and J. V. Tarazona. 1991. Short-term toxicity of fluoride
ion (F") in soft water to rainbow trout and brown trout. Chemosphere
22:605-611.
Campbell, A. 1987. Determination of fluoride in various matrices. Pure
Appl. Chem. 59:695-702.
Carlson, C. H., W. D. Armstrong, and L. Singer. 1960. Distribution and
excretion of radiofluoride in the human. Proc. Soc. Exp. Biol. Med.
104:235-239.
Caraccio, T., J. Greensher, and H. Mofenson. 1983. The toxicology of fluo-
ride. In Clinical Management of Poisoning and Drug Overdose, L.
Haddad and J. Winchester, eds. Philadelphia: W.B. Saunders.
Cass, J. S. 1961. Fluorides: a critical review. IV. Response of livestock and
poultry to absorption of inorganic fluorides. J. Occup. Med. 3:471-527.
CEPA (Canadian Environmental Protection Act). 1993. Inorganic Fluorides,
Priority Substances. Ottawa: List Assessment Report, Canada Commu-
nication Group Publishing.
Cerklewski, F. L. 1997. Fluoride bioavailability — Nutritional and clinical
aspects. Nutr. Res. 17:907-927.
Chinoy, N., and E. Sequeira. 1989a. Effects of fluoride on the
histoarchitecture of the reproductive organs of the male mouse. Reprod.
ToxicoL 3:261-267.
Chinoy, N., and E. Sequeira. 1989b. Fluoride induced biochemical changes
in reproductive organs of male mice. Fluoride 22:79-85.
Chinoy, N., E. Sequeira, and M. Narayama. 1991. Effect of vitamin C and
calcium on the reversibility of fluoride-induced alterations in spermato-
zoa of rabbits. Fluoride 24:29-39.
Cholak, J. 1959. Fluorides: a critical review. I. The occurrence of fluoride
in air, food, and water. J. Occup. Med. 1 :50I-51 1.
Church, L. E. 1976. Fluorides — use with caution. Md. Dent. Assoc. J.
19:106-112.
Clark, R. G., and D. J. Stewart. 1983. Fluorine. Pp. 129-134 in The Mineral
Requirements of Grazing Ruminants, N. D. Grace, ed. New Zealand
Society of Animal Production Occasional Publication 9:129-134.
Clay, A. B., and J. W. Suttie. 1985. The availability of fluoride from NaF
and phosphorus supplements. Vet. Human Toxicol. 27:3—6.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
FLUORINE
165
Comar, C. L., W. J. Visek, W. E. Lotz, and J. H. Rust. 1953. Effects of
fluorine on calcium metabolism and bone growth in pigs. Am. J. Anat.
92:361-389.
Cronin, S. J., V. Manoharan, M. J. Hedley, and L. Loganathan. 2000. Fluo-
ride: a review of its fate, bioavailability, and risks of fluorosis in grazed-
pasture systems in New Zealand. N. Z. J. Agric. Res. 43:295-321.
Dabeka, R. W., and A. D. McKenzie. 1995. Survey of lead, cadmium, fluo-
ride, nickel, and cobalt in food composites and estimation of dietary
intakes of these elements by Canadians in 1986-1988. J. Assoc. Off.
Anal. Chem. Int. 78:897-909.
Daston, G., B. Rehnberg, B. Carver, and B. Kavelock. 1985. Toxicity of
sodium fluoride to the postnatally developing rat kidney. Environ. Res.
37:461^74.
Davison, A. 1983. Uptake, transport and accumulation of soil and airborne
fluorides by vegetation. Pp. 61-82 in Fluorides: Effects on Vegetation,
Animals and Humans, S. J. Shupe, H. Peterson, and N. Leone, eds. Salt
Lake City, UT: Paragon Press.
DeLopez, O. H., F. A. Smith, and H. C. Hodge. 1976. Plasma fluoride
concentrations in rats acutely poisoned with sodium fluoride. Toxicol.
Appl. Pharmacol. 37:75-83.
DenBesten, P. K., and H. Thariani. 1992. Biological mechanisms of fluoro-
sis and level and timing of systemic exposure to fluoride with respect to
fluorosis. J. Dent. Res. 71:1238-1243.
Derelanko, M., S. Gad, F. Gavigan, and B. Dunn. 1985. Acute dermal tox-
icity of dilute hydrofluoric acid. J. Toxicol. Cutan. Ocular. Toxicol.
4:73-85.
Dukes, M. N. G. 1980. Fluoride. In Side Effects of Drugs, Annual 4, M. N.
G. Dukes, ed. Oxford: Excerpta Medica.
Easmann, R. P., D. E. Steflik, D. H. Pashley, R. V. McKinney, and G. M.
Whitford. 1984. Surface changes in rat gastric mucosa induced by so-
dium fluoride: a scanning electron microscopy study. J. Oral Pathol.
13:255-264.
Easmann, R. P., D. H. Pashley, N. Birdsong, R. M. McKinney, and G. M.
Whitford. 1985. Recovery of rat gastric mucosa following single fluo-
ride dosing. J. Oral Pathol. 14:779-792.
Eichler, H. G., K. Lenz, M. Fuhrmann, and K. Hruby. 1982. Accidental
ingestion of NaF tablets by children: report of a poison control center
and one case. Int. J. Clin. Pharm. Ther. Toxicol. 20:334—338.
Elsair, J., R. Merad, R. Denine, M. Reggabi, B. Alamir, S. Benali, M.
Azzouz, and K. Khelfat. 1980. Boron as a preventive antidote in acute
and subacute fluoride intoxication in rabbits: its action on fluoride and
calcium-phosphorus metabolism. Fluoride 13:129-138.
EPA (U.S. Environmental Protection Agency). 1980. Reviews of the envi-
ronmental effects of pollutants: IX. Fluoride. Health Effects Research
Laboratory, Office of Research and Development. USEPA-600/1-78-
050, Cincinnati, OH.
EPA (U.S. Environmental Protection Agency). 1986. Quality criteria for
water. USER A440 A'- 86-001.
Ericsson, Y., and S. Ullberg. 1958. Autoradiographic investigations of the
distribution of F'^ in mice and rats. Acta Odont. Scand. 16:363-374.
Essman, E., W. Essman, and E. Valderrama. 1981. Histaminergic media-
tion of the response of rat skin to topical fluorides. Arch. Dermatol. Res.
271:325-340.
Fargo, J. M., G. Bohstedt, P. H. Phillips, and E. B. Hart. 1938. The effect of
fluorine in rock phosphate on growth and reproduction in swine. Proc.
Am. Soc. Anim. Prod. 31:122-125.
Fejerskov, O., A. Thylstrup, and M. J. Larsen. 1977. Clinical and structural
features and possible pathogenic mechanisms of dental fluorosis. Scand.
J. Dent. Res. 85:510-534.
Fleischer, M. 1962. Fluoride content of ground water in the conterminous
United States. U.S. Geological Survey Miscellaneous Geological Inves-
tigation 1—387. Washington, D.C.: U.S. Geological Survey.
Fleischer, M., R. M. Forbes, and R. C. Harriss. 1974. Fluorine. Pp. 22-25 in
Geochemistry and the Environment. Vol. 1. The relation of selected
trace elements to health and disease. Washington, D.C.: National
Academy of Science.
Fliihler, H., J. Polomski, and P. Blaser. 1982. Retention and movement of
fluoride in soils. J. Environ. Qual. 11:461^68.
Franke, J. 1989. Differences in skeletal response to fluoride in humans and
animals: an overview. Fluoride 22:10—19.
Fuge, R. 1988. Sources of halogens in the environment, influences on hu-
man and animal health. Environ. Geochem. Health 10:51-61.
Fuge, R., and M. J. Andrews. 1988. Fluorine in the UK environment.
Environ. Geochem. Health 10:96-104.
Gaciri, S. J., and T. C. Davies. 1993. The occun'ence and geochemistry of
fluoride in some natural waters of Kenya. J. Hydrol. 143:395^12.
Gardiner, E. E., F. N. Andrews, R. L. Adams, J. C. Rogler, and C. W.
Carrick. 1959. The effect of fluorine on the chicken proventriculus.
Poult. Sci. 38:1423-1425.
Gardiner, E. E., K. S. Winchell, and R. Hironaka. 1968. The influence of
dietary sodium fluoride on the utilization and metabolizable energy
value of a poultry diet. Poult. Sci. 47:1241-1244.
Gardner D. E., F. A. Smith, H. C. Hodge, D. E. Overton, and R. Feltman.
1952. The fluoride content of placental tissue as related to the fluoride
content of drinking water. Science 115:208-209.
Garlick, N. L. 1955. The teeth of the ox in clinical diagnosis. IV. Dental
fluorosis. Am. J. Vet. Res. 16:38^M.
Gerry, R. W., C. W. Cairick, R. E. Roberts, and S. M. Hauge. 1947. Phos-
phate supplements of different fluorine contents as sources of phospho-
rus for chickens. Poult. Sci. 26:323-334.
Gessner, B. D., M. Beller, J. P. Middaugh, and G. M. Witford. 1994. Acute
fluoride poisoning from a public water system. N. Engl. J. Med. 330:95—99.
Goldemberg, L. 1931. Tratemiento e la enfermedad de Basedow y del
hipertiroidismo por fluor. Rev. Soc. Med. Int. Soc. Fisiolog. 6:217-242.
Greenwood, D. A., J. R. Blayney, O. K. Skinsnes, and P. C. Hodges. 1946.
Comparative studies of the feeding of fluorides as they occur in purled
bone meal powder, defluorinated phosphate and sodium fluoride in dogs.
J. Dent. Res. 25:311-326.
Greenwood, D. A., J. L. Shupe, G. E. Stoddard, L. E. Harris, H. M. Nielsen,
and L. E. Olson. 1964. Fluorosis in Cattle. Logan: Utah Agric. Exp. Stn.
Spec. Rep. 17.
Gutierrez, O., A. 1. Marrero, 1. Terry, and J. Cairo. 1993. Utilization of
fluoride as growth promoter in broiler rations. Performance measure-
ments. Cuban J. Agric. Sci. 27:319—323.
Guy, W. 1979. Inorganic and organic fluorine in human blood. Pp. 125-147
in Continuing Evaluation of the Use of Fluorides, E. Johansen, D. Taves,
and T. Olsen, eds. Boulder, CO: Westview Press for the American
Association for the Advancement of Science (AAAS Selected Sympo-
sium 11).
Guy, W., D. Taves, and W. Brey. 1976. Organic fluoro compounds in hu-
man plasma: prevalence and characterization. Am. Chem. Soc. Symp.
Ser. 28:117-134.
Hahn, P. H. W., and W. Guenter. 1 986. Effect of dietary fluoride and alumi-
num on laying hen performance and fluoride concentration in blood,
soft tissue, bone and egg. Poult. Sci. 65:1343—1349.
Hamilton, M. 1992. Water fluoridation: a risk assessment perspective. J.
Environ. Health 54:27-32.
Harris, L. E., R. J. Raleigh, M. A. Madsen, J. L. Shupe, J. E. Butcher, and D.
A. Greenwood. 1 963. Effects of various levels of fluorine, stilbestrol, and
oxytetracycline in the fattening ration of lambs. J. Anim. Sci. 22:51-56.
Harris, L. E., R. J. Raleigh, G. E. Stoddard, D. A. Greenwood, J. L. Shupe,
and H. M. Nielsen. 1964. Effects of fluorine on dairy cattle. 111. Diges-
tion and metabolism trials. J. Anim. Sci. 23:537-546.
Hams, M. A., D. A. Madsen, L. E. Greenwood, J. L. Shupe, and R. J.
Raleigh. 1958. Effects of various levels and sources of fluorine in the
fattening ration of Columbia, Rambouillet, and Terghee lambs. J. Agric.
Food Chem. 6:365-368.
Harvey, J. M. 1952. Chronic endemic fluorosis of Merino sheep in
Queensland. Queensl. J. Agric. Sci. 9:47-141.
Harzdorf, C, N. Kinwel, L. Marangoni, J. Ogleby, J. Ravier, and F. Roost.
1986. The determination of fluoride in environmentally relevant matri-
ces. Anal. Chim. Acta 182:1-16.
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inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
766
MINERAL TOLERANCE OF ANIMALS
Hemens, J., and R. J. Warwicit. 1972. The effects of fluoride on estuarine
organisms. Water Res. 6:1301-1308.
Hillman, D., D. L. Bolenbaugh and E. M. Convey. 1979. Hypothyroidism
and anaemia related to fluoride in dairy cattle. J. Dairy Sci. 62:416^23.
Hobbs, C. S., and G. M. Merriman. 1959. The effects of eightyears continu-
ous feeding of different levels of fluorine and alleviators on feed con-
sumption, teeth, bones and production of cows. J. Anim. Sci. 18:1526.
(Abstr.)
Hobbs, C. S., and G. M. Merriman. 1962. Fluorosis in beef cattle. Knox-
ville: Tenn. Agric. Exp. Stn. Bull. 351.
Hobbs, C. S., R. P. Moorman, Jr., J. M. Griffith, J. L. West, G. M. Memman,
S. L. Hansard, and C. C. Chamberlain, with the collaboration of W. H.
Maclntire, L. J. Jones, and L. S. Jones. 1954. Fluorosis in cattle and
sheep. Knoxville: Tenn. Agric. Exp. Stn. Bull. 235.
Hodge, H. C, and F. A. Smith. 1965. Biological properties of inorganic
fluorides. Pp. 1^2 in Fluoride Chemistry, Vol. 4, J. H. Simons, ed.
New Yoric: Academic Press.
Hodge, H. C, and F. A. Smith. 1 98 1 . Fluoride. Pp. 439-483 in Disorders of
Mineral Metabolism, Vol. 1, F. Bronner and J. W. Coburn, eds. New
York: Academic Press.
Hoogstratten, B., N. C. Leone, J. L. Shupe, D. A. Greenwood, and J.
Lieberman. 1965. Effect of fluorides on the hematopoietic system, liver
and thyroid gland in cattle. J. Am. Med. Assoc. 192:26-32.
Ikenishi, R., T. Kitagawa, and M. Nishiuchi. 1988. Gas chi'omatographic
method for the determination of fluoride ion in biological samples: 1.
Fluoride level in monkey. Chem. Pharm. Bull. 36:662-669.
IPCS (International Program on Chemical Safety of the United Nations).
2002. Fluorides, Environmental Health Criteria 227. Geneva: World
Health Organization.
Jedra, M., B. Urbanek-Karlowska, M. Fonberg-Broczek, D. Sawilska-
Rautenstrauch, and P. Badowsk. 2001. Bioavailable fluoride in
poultry deboned meat and meat products. Rocz. Panstw. Zakl. Hig.
52:225-230.
Johnson, L. C. 1965. Histogenesis and mechanisms in the development of
osteofluorosis. Pp. 424-441 in Fluorine Chemistry, Vol. 4, J. H. Simons,
ed. New York: Academic Press.
Jowsey, J.. B. L. Riggs, and P. J. Kelley. 1979. Fluoride in the treatment of
osteoporosis. Pp. 1 1 1-123 in Continuing Evaluation of the Use of Fluo-
rides, E. Johansen, D. Taves, and T. Olsen, eds. Boulder, CO: Westview
Press for the American Association for the Advancement of Science
(AAAS Selected Symposium 11).
Jubb, T. F., T. E. Annand, D. C. Main, and G. M. Murphy. 1993. Phospho-
rus supplements and fluorosis in cattle — a northern Australian experi-
ence. Aust. Vet. J. 70:379-383.
Kabata-Pendias, A., andH. Pendias. 1984. Fluorine. Pp. 209-215 in Trace
Elements in Soil and Plants. Boca Raton, FL: CRC Press.
Kaminsky, L. S., M. C. Mahoney, J. Leach, J. Melius, and M. J. Miller.
1990. Fluoride: benefits and risks of exposure. Crit. Rev. Oral Biol.
Med. 1:261-281.
Kay, C. E., P. C. Tourangeau, and C. C. Gordon. 1975. Industrial fluorosis in
wild mule and whitetail deer from western Montana. Fluoride 8:182-191.
Keplinger, M. L., and L. W. Suissa. 1968. Toxicity of fluorine short-term
inhalation. Am. Ind. Hyg. Assoc. J. 29:10-18.
Kessabi, M. 1984. Metabolisme et biochimie toxicologique due fluor: une
revue. Rev. Med. Vet. 135:497-510.
Kick, C. H., R. M. Bethke, and P. R. Record. 1933. Effect of fluorine in the
nutrition of the chick. Poult. Sci. 12:382-387.
Kick, C. H., R. M. Bethke, B. H. Edgington, O. H. M. Wilder, P. R. Record,
W. Wilder, T. J. Hill, and S. W. Chase. 1935. Fluorine in animal nutri-
tion. Columbus: Ohio Agric. Exp. Stn. Bull. 558.
Kierdorf, H., U. Kierdorf, F. Sedlacek, and M. Erdelen. 1996. Mandibular
bone fluoride levels and occurrence of fluoride induced dental lesions in
populations of wild red deer (Cervus elaphus) from central Europe.
Environ. Pollut. 93:75-81.
Kirk, K. L. 1991. Biochemistry of the Elemental Halogens and Inorganic
Halides. New York: Plenum, pp. 19-68.
Knight, H. G., A. K. Furr, and T. F. Parkinson. 1988. Determination of
fluorine by neutron activation analysis. Anal. Chem. 49:1507—1510.
Krishnamachari, K. A. V. R. 1987. Fluorine: trace elements in human and
animals. Nutrition 1:365^15.
Krook, L., and G. A. Maylin. 1979. Industrial fluoride pollution. Chronic fluo-
ride poisoning in Cornwall Island cattle. Cornell Vet. 69 (Suppl. 8):4— 70.
Krug, O. 1927. Fine Vergiftung von Milchohen dutch Kilselfluornatrium.
Z. Fleish. Milchhyg. 37:38-39.
Kudo, A., and J. P. Garrec. 1983. Accidental release of fluoride into experi-
mental pond and accumulation in sediments, plants, algae, molluscs and
fish. Regul. Toxicol. Pharmacol. 3:189-198.
Kumpulainen, J., and P. Koivistoinen. 1977. Fluorine in foods. Residue
Rev. 68:37-57.
Lall, S. P. 1994. Minerals in fish and shellfish. Pp. 187-213 in Fish and Fishery
Products, A. Ruiter, ed. Wallingford, Oxon, UK: CAB International.
Lee, G., M. R. EUersieck, F. L. Mayer, and G. F. Krause. 1995. Predicting
chronic lethality of chemicals to fishes from acute toxicity test data:
multifactor probit analysis. Environ. Toxicol. Chem. 14:345-349.
Li Y., A. Dunipace, and G. Stookey. 1987. Absence of mutagenic or anti-
mutagenic activities of fluoride in Ames Salmonella assays. Mutat. Res.
190:229-236.
Li, Y., C. K. Liang, B. P. Katz, E. J. Brizendine, and G. K. Stookey. 1995.
Long-term exposure to fluoride in drinking water and sister chromatid
exchange frequency in human blood lymphocytes. J. Dent. Res.
74:1468-1474.
Lim, J. K., G. J. Renaldo, and P. Chapman. 1978. LDjq of stannous fluoride,
sodium fluoride and sodium mono-fluoro phosphate in the mouse com-
pared to the rat. Caries Res. 12:177—179.
Maurer, J. K., M. C. Cheng, B. G. Boysen, and R. L. Anderson. 1990. Two-
year carcinogenicity study of sodium fluoride in rats. J. Nat. Cancer
Inst. 82(13):1118-1126.
Maurer, R. L., and H. G. Day. 1957. The non-essentiality of fluorine in
nutrition. J. Nutr. 62:561-573.
McClendon, J. F., and J. Gershon-Cohen. 1953. Water-culture crops
designed to study deficiencies in animals. J. Agric. Food Chem.
1:464-466.
McDowell, L. R. 2003. Minerals in Animal and Human Nutrition, 2nd ed.
Amsterdam: Elsevier.
McGown, E. L., D. L. Kolstad, and J. W. Suttie. 1976. Effect of dietary fat
on fluoride absorption and tissue fluoride retention in rats. J. Nutr.
106:575-579.
Mclvor, M. 1990. Acute fluoride toxicity: pathophysiology and manage-
ment. Drug Safety 5:79-85.
Merriman, G. M., and C. S. Hobbs. 1962. Bovine fluorosis from soil and
water sources. Knoxville: Tenn. Agric. Exp. Stn. Bull. 347.
Messer, H. H. 1984. Fluorine. Pp. 55-87 in Biochemistry of the Essential
Ultratrace Elements, E. Frieden, ed. New York: Plenum Press.
Messer, H. H., W. D. Armstrong, andL. Singer. 1972. Fertility impairment
in mice on a low fluoride intake. Science 177:893-894.
Messer, H. H., W. D. Armstrong, andL. Singer. 1973. Influence of fluoride
intake on reproduction in mice. J. Nutr. 103:1319-1324.
Milhaud, G., L. Bahri, and A. Dridi. 1981. The effects of fluoride on fish in
Gabes Gulf. Fluoride 14:161-168.
Miller, R. F., and P. H. Phillips. 1953. The metabolism of fluorine in the
bones of the fluoride-poisoned rat. J. Nutr. 5 1 :273— 281 .
Murray, F. 1983. Fluoride retention by sandy soils. Water Air Soil Pollut.
20:361-367.
Murray, F. 1984. Fluoride retention in highly leached disturbed soils.
Environ. Pollut. (Series B) 7:83-95.
Neeley, K. L., and F. G. Harbaugh. 1954. Effects of fluoride ingestion on a
herd of dairy cattle in the Lubbock, Texas area. J. Am. Vet. Med. Assoc.
124:344-350.
Nell, J. A., and G. Livanos. 1988. Effects of fluoride concentration in sea-
water on growth and fluoride accumulation by Sydney rock oyster
(Saccostrea commercialis) and flat oyster (Ostrea angasi) spat. Water
Res. 22:749-753.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
FLUORINE
167
Neumiiller, O. 1981. Rompps Chemie Lexikon, Vol. 2. 8th ed, Stuttgart:
Franck'sch Verlagshandlung.
Newell, G. W., and H. J. Schmidt. 1958. The effects of feeding fluorine as
sodium fluoride to dairy cattle — a six-year study. Am. J. Vet. Res.
19:363-375.
Noemmik, H. 1953. Fluorine in Swedish agricultural products, soil and
drinking water. Acta Polytechnica 127:1—121.
Nopakun, J., and H. H. Messer. 1990. Mechanisms of fluoride absorption
from the rat small intestine. Nutr. Res. 10:771-780.
NRC (National Research Council). 1974. Effects of Fluorides in Animals.
Washington, DC: National Academy Press.
NRC. 1980. Mineral Tolerance of Domestic Animals. Washington, D.C.:
National Academy Press.
NRC. 1993. Health Effects of Ingested Fluoride. Washington, D.C.:
National Academy Press.
NTP (National Toxicological Program). 1990. Technology of carcinogen-
esis studies in F344/n rats and 6C3F1 mice (drinking water studies).
NTP TR 393. Washington, D.C.: U.S. Department of Health and Hu-
man Services.
Phillips, P. H., H. E. English, andE. B. Hart. 1935. The augmentation of the
toxicity of fluorosis in the chick by feeding desiccated thyroid. J. Nutr.
10:399^07.
Pickering, W. F., J. Slavek, and P. Waller. 1988. The effect of ion exchange
on the solubility of fluoride compounds. Water Air Soil Pollut. 39:323—
336.
Pierce, A. W. 1952. Studies on fluorosis of sheep. 1. The toxicity of water-
borne fluoride for sheep maintained in pens. Aus. J. Agric. Res. 3:326-
340.
Pierce, A. W. 1954. Studies on fluorosis of sheep. 11. The toxicity of water-
borne fluoride for mature grazing sheep. Aus. J. Agric. Res. 5:545-554.
Pierce, A. W. 1959. Studies on fluorosis of sheep. 11. The toxicity of water-
borne fluoride for the grazing sheep throughout its life. Aus. J. Agric.
Res. 10:186-198.
Pillai, K. S., A. T. Mathai, and P. B. Deshmuhk. 1989. Effect of fluoride on
reproduction in mice. Fluoride 22:165-168.
Pimentel, R., and R. V. Bulkley. 1983. Influence of water hardness of fluo-
ride toxicity to rainbow trout. Environ. Toxicol. Chem. 2:381-386.
Ramberg, C. F., Jr., J. M. Phang, G. P. Mayer, A. 1. Norberg, and D. S.
Kronfeld. 1970. Inhibition of calcium absorption and elevation of cal-
cium removal rate from bone in fluoride treated calves. J. Nutr. 100:981-
990.
Rao, G. S. 1984. Dietary intake and bioavailability of fluoride. Annu. Rev.
Nutr. 4:115-136.
Rao, S. R., K. J. R. Murthy, T. V. Murthy, S. S. Reddy, and M. K. Saxena.
1975. Treatment of fluorotic radiculopathy. Fluoride 8:144—154.
Ream, L., D. Hull, J. Scott, and P. Pendergrass. 1983a. Fluoride ingestion
during multiple pregnancies and lactations: microscopic observations
on bone of the rat. Virchows Arch. B. Cell Pathol. 44:35^4.
Ream, L., J. Scott, and P. Pendergrass. 1983b. Bone morphology of wean-
ling rats from dams exposed to fluoride. Cell Tissue Res. 233:689-691.
Robinson, W. O., and G. Edgington. 1946. Fluorine in soils. Soil Sci.
61:341-353.
Roholm, K. 1937. Fluorine intoxication: a clinical-hygienic study with a
review of the literature and some experimental investigations. London:
H. K. Lewis.
Rosenholtz, M., T. Carson, M. Weeks, F. Wilinski, D. Ford, and F. Oberst.
1963. A toxicopathologic study in animals after brief single exposures
to hydrogen fluoride. Am. Ind. Hyg. Assoc. J. 24:253—261.
Schamschula, R., J. Duppenthaler, E. Sugar, K. Toth, and D. Barmes. 1988.
Fluoride intake and utilization by Hungarian children: associations and
interrelationships. Acta Physiol. Hung. 72:253-261.
Schwarz, K., and D. B. Milne. 1972. Fluorine requirement for growth in the
rat. Bioinorg. Chem. 1:331—338.
Seffner, W., and W. Teubener. 1983. Antidotes in experimental fluorosis on
pigs morphological studies. Fluoride 16:33-37.
Shanks, D. 1997. Clinical implications of volcanic eruptions on livestock —
case studies following the 1995 and 1996 eruptions of Mt. Ruapehu.
Proceedings of the 27th Seminar of the Society of Sheep and Beef Cattle
Veterinarians. N. Z. Vet. Assoc. Publ. 175:1-13.
Shashi, A. 1990. Histopathological changes in rabbit ovary during experi-
mental fluorosis. Indian J. Pathol. Microbiol. 33:113-117.
Shroy, R. E., H. W. Kraner, and K. W. Jones. 1982. Proton activation analy-
sis for the measurement of fluorine in food samples. Anal. Chem.
54:407^13.
Shupe, J. L. 1969. Levels of toxicity to animals provide sound basis for
fluoride standards. A symposium: the technical significance of air
quality standards. Environ. Sci. Technol. 3:721—726.
Shupe, J. L. 1970. Fluorosis. Pp. 288-301 in Bovine Medicine and Surgery,
W. J. Gibbons, E. J. Catcott, and J. F. Smithcors, eds. Wheaton, IL: Am.
Vet. Publ.
Shupe, J. L. 1980. Clinopathological features of fluoride toxicosis in cattle.
J. Anim. Sci. 51:746-758.
Shupe, J. L., and E. W. Alther. 1966. The effects of fluorides on livestock,
with particular reference to cattle. Pp. 307-354 in Handbook of Experi-
mental Pharmacology, Vol. 20, Pt. 1 , O. Eichler, A. Faran, H. Herken,
A. D. Welch, and F. A. Smith, eds. New York: SpringerVerlag.
Shupe, J. L., M. L. Miner, L. E. Harris, and D. A. Greenwood. 1962. Rela-
tive effects of feeding hay atmospherically contaminated by fluoride
residue, normal hay plus calcium fluoride, and normal hay plus sodium
fluoride to dairy heifers. Am. J. Vet. Res. 23:777-787.
Shupe, J. L., L. E. Harris, D. A. Greenwood, J. E. Butcher, and H. M.
Nielsen. 1963a. The effect of fluorine on dairy cattle. V. Fluorine in the
urine as an estimator of fluorine intake. Am. J. Vet. Res. 24:300—306.
Shupe, J. L., M. L. Miner, D. A. Greenwood, L. E. Hams, and G. E.
Stoddard. 1963b. The effect of fluorine on dairy cattle. 11. Clinical and
pathological effects. Am. J. Vet. Res. 24:964-984.
Shupe, J. L., A. E. Olsen, and H. B. Peterson. 1984. Fluoride toxicosis in
wild ungulates. J. Am. Vet. Assoc. 185:1295-1300.
Shupe, J. L., R. H. Bruner, J. L. Seymour, and C. L. Alden. 1992. The
pathology of chronic bovine fluorosis: a review. Toxicol. Pathol.
20:274-288.
Singer, L., and W. D. Armstrong. 1964. Regulation of plasma fluoride in
rats. Proc. Soc. Exp. Biol. Med. 117:686-689.
Singh, A., and S. S. Jolly. 1970. Chronic effects on the skeletal system.
Fluoride and human health, Geneva: World Health Organization, pp.
238-249.
Singh, J. L., andD. Swarup. 1995. Clinical observations and diagnosis fluo-
rosis in dairy cows and buffaloes. Agripractice 16:25—30.
Smith, F. A., D. E. Gardner, and H. C. Hodge. 1950. Investigation on the
metabolism of fluoride. 11. Fluoride content of blood and urine as a
function of fluorine in drinking water. J. Dent. Res. 29:596-600.
Smith, L. R., T. M. Hailstone, N. C. Bay, R. M. Block, and A. B. De Leon.
1985. Studies on the acute toxicity of fluoride ion to stickleback, fathead
minnow, and rainbow trout. Chemosphere 14:1383-1389.
Smith, S. B., N. S. Cowen, J. W. Dodge, L. S. Mix, G. L. Rumsey, A. A.
Warner, and D. F. Woodward. 1970. Effect of added levels of fluorine
on selected characteristics of egg shells and bones from caged layers.
Poult. Sci. 49:1438. (Abstr.).
Snook, L. C. 1958. The use of rock phosphate from Christmas Island in
poultry rations. J. Dep. Agric. W. Aust. 7:545-550.
Soevik, T., and O. R. Braekkan. 1981. The fluoride contents in some Nor-
wegian fish products and other marine products. Fiskeridir. Skr. Ser.
Ernae. 2:1-16.
Spencer, G. R., F. I. El-Sayed, G. H. Kroening, K. L. Pell, N. Shoup, D. F.
Adams, M. Franke, and J. E. Alexander. 1971. Effects of fluoride, cal-
cium, and phosphorus on porcine bone. Am. J. Vet. Res. 32:1751-1774.
Stoddard, G. E., G. Q. Bateman, L. E. Harris, J. L. Shupe, and D. A. Green-
wood. 1963. Effects of fluorine on dairy cattle. IV. Milk production. J.
Dairy Sci. 46:720-726.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
168
MINERAL TOLERANCE OF ANIMALS
Stokinger. H. E. 1949. Toxicity following inhalation of fluorine and hydro-
gen fluoride. Pp. 1021-1057 in Pharmacology and toxicology of ura-
nium compounds, C. Voegtlin and H. C. Hodge, eds. New York:
McGraw-Hill.
Storer, N. L., and T. S. Nelson. 1968. The effect of various aluminum com-
pounds on chick performance. Poult. Sci. 47:244—247.
Street, H. R. 1942. The influence of aluminum sulfate and aluminum hy-
droxide upon the absorption of dietary phosphorus by the rat. J. Nutr.
24:111-119.
Susheela, S . , and A. Kumar. 1 99 1 . A study of the effect of high concentra-
tions of fluoride on the reproductive organs of male rabbits, using light
and scanning electron microscopy. J. Reprod. Fertil. 92:353-360.
Suttie, J. W., andE. C. Faltin. 1971. The effect of a short period of fluoride
ingestion on dental fluorosis in cattle. Am. J. Vet. Res. 32:217-222.
Suttie, J. W., and E. C. Faltin. 1973. Effects of sodium fluoride on dairy
cattle: influence of nutritional state. Am. J. Vet. Res. 34:479.
Suttie, J. W., and D. L. Kolstad. 1977. Effects of dietary fluoride ingestion
on ration intake and milk production. J. Dairy Sci. 60:1568-1573.
Suttie, J. W., and P. H. Phillips. 1959. Studies on the effects of dietary
sodium fluoride on dairy cows. V. A three-year study on mature ani-
mals. J. Dairy Sci. 42:1063-1069.
Suttie, J. W., R. F. Miller, and P. H. Phillips. 1957a. Effects of dietary
sodium fluoride on dairy cows. 1. The physiological effects and the de-
velopment symptoms of fluorosis. J. Nutr. 63:21 1-224.
Suttie, J. W., R. F. Miller, and P. H. Phillips. 1957b. Studies of the effects of
dietary sodium fluoride on dairy cows. 11. Effects on milk production. J.
Dairy Sci. 40:1485-1491.
Suttie, J. W., P. H. Phillips, andR. F. Miller. 1958. Studies of the effects of
dietary sodium fluoride on dairy cows. 111. Skeletal and soft tissue fluo-
rine deposition and fluorine toxicosis. J. Nutr. 65:293-304.
Suttie, J. W., R. Gesteland, and P. H. Phillips. 1961. Effects of dietary
sodium fluoride on dairy cows, IV. In young heifers. J. Dairy Sci.
44:2250-2258.
Suttie, J. W., J. R. Carlson, and E. C. Faltin. 1972. Effects of alternating
periods of high- and low-fluoride ingestion on diary cattle. J. Dairy Sci.
55:790-804.
Symonds, R., W. Rose, and M. Reed. 1988. Contribution of CI- and F-
bearing gases to the atmosphere by volcanoes. Nature 334:415^18.
Tao, S., and J. W. Suttie. 1976. Evidence for a lack of an effect of dietary
fluoride level on reproduction in mice. J. Nutr. 106:1115—1122.
Taves, D. R. 1968. Electrophoretic mobility of serum fluoride. Nature
220:582-583.
Taves, D., N. Forbes, D. Silverman, and D. Hicks. 1983. Inorganic fluoride
concentrations in human and animal tissues. Pp. 189-193 in Fluorides:
Effects on Vegetation, Animals and Humans, J. Shupe, H. Peterson, and
N. Leone, eds. Salt Lake City, UT: Paragon Press.
Tong, C, C. McQueen, S. Ved Brat, and G. Williams. 1988. The lack of
genotoxicity of sodium fluoride in a battery of cellular tests. Cell Biol.
Toxicol. 4:173-186.
Trautner K., and G. Siebert. 1986. An experimental study of bioavailability
of fluoride from dietary sources in man. Arch. Oral Biol. 31:223-228.
Underwood, E. J. 1981. The mineral nutrition of livestock, 2nd ed. Slough,
UK: Commonwealth Agricultural Bureaux.
Underwood, E. J., and N. F. Suttie. 1999. The Mineral Nutrition of Live-
stock, 3rd ed. New York: CABl Publishing.
USPHS AdHoc Subcommittee on Fluoride. 1991. Review of fluoride: ben-
efits and risks. Bethseda, MD: U.S. Public Health Service, Department
of Health and Human Services.
VanWazer, J. R. 1961. Technology, biological functions, and applications.
Pp. 1025—1075 in Phosphorus and Its Compounds, Vol. 2. New York:
Interscience.
Venkateswarlu, P. 1983. Overview of analytical methods for fluorine in air,
water, soil vegetation, body fluids and tissues. Pp. 19—52 in Fluorides:
Effects on Vegetation, Animals and Humans, J. Shupe, H. Peterson, and
N. Leone, eds. Salt Lake City, UT: Paragon Press.
Wagner, M. J., and J. C. Muhler. 1957. The metabolism of natural and
artificial fluoridated waters. J. Dent. Res. 36:552—558.
Wallace, P. C. 1953. The metabolism of '^F in normal and chronically
fluorosed rats. Berkeley: University of California Report UCRL-2196.
Weber, C. W. 1966. Fluoride in the nutrition and metabolism of experimen-
tal animals. Ph.D. dissertation. University of Arizona, Tucson.
Weber, C. W., A. R. Doberanz, and B. L. Reid. 1969. Fluoride toxicity in
the chick. Poult. Sci. 48:230-235.
Wen, M. K., Q. C. Li, and C. Y. Wang. 1996. Developments in the analysis
of fluoride 1993-1995. Fluoride 29:82-88.
Wheeler, S. M., A. D. Turner, and K. J. Ellis. 1988. The effects of sodium
borate and sodium bicarbonate upon fluoride retention and serum cal-
cium and phosphate in sheep. J. Trace Elem. Electrolytes Health Dis.
2:185-189.
Whitford, G. M. 1990. The physiological and toxicological characteristics
of fluoride. J. Dent. Res. 69:539-549.
Whitford, G. 1996. The Metabolism and Toxicity of Fluoride, Vol. 16, 2nd
rev. ed. Basel: Karger, Monographs in Oral Science.
Whitford, G. M., and D. R. Taves. 1973. Fluoride-induced diuresis: renal
tissue solute concentrations, functional, hemodynamic and histologic
correlates in the rate. Anesthesiology 39:416^27.
WHO (World Health Organization). 1984. Fluorine and Fluorides. Envi-
ronmental Health Criteria 36. Geneva; WHO.
WHO (World Health Organization). 1994. Fluorides and Oral Health. WHO
technical report series #846. Geneva; WHO.
Wuthier, R. E., and P. H. Phillips. 1959. The effects of longtime administra-
tion of small amounts of fluoride in food or water on caries-susceptible
rats. J. Nutr. 67:581-588.
Zebrowski, E. J., and J. W. Suttie. 1966. Glucose oxidation and glycogen
metabolism in fluoride-fed rats. J. Nutr. 88: 267-272.
Zeigler, E., M. D. Shelby, and K. L. Witt. 1993. Genetic toxicity of fluoride.
Environ. Mol. Mutagen. 21:309-318.
Zipkin, 1., F. McClure, and W. Lee. 1960. Effect of prolonged exposure to
fluoride on the ash, fluoride, citrate, and crystallinity of bovine bone.
Arch. Oral BioL 2:190-195.
Zipkin, 1., E. D. Fanes, and J. L. Shupe. 1964. Effect of prolonged exposure
to fluoride on the ash, fluoride, citrate, and crystallinity of bovine bone.
Am. J. Vet. Res. 25:1591-1597.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
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FLUORINE
181
TABLE 14-2 Fluorine Concentrations in Fluids and Tissues of Animals (mg/kg or |Jg/L)
Level and
Liver or
Egg
Animal
Source of F
Plasma
Bone
Soft Tissues
Muscle
Milk
Yolk
Reference
Humans
Diet
0.003-
0.080
1.5-2.2
19.6-159
J
Guy et at., 1976; Zipkin
et at., 1960; Taves et at., 1983
Chickens,
16
0.001
538
5.2
4.0
4.3
Hahn and Guenter, 1986
laying
too
0.003
2,247
5.5
4.0
3.3
hens
1,300
0.010
2,600
19.2
6.7
18.4
Meat and
poultry
Cattle,
fluorosis
Cows
Cows
Cows
Cows
Sheep
17 varieties
of muscle
and poultry
in Canada
Meat and
7 varieties of
poultry
meat and
poultry in
Hungary
12 varieties
of diary
products in
Canada
13 varieties
of dairy
products in
[ Hungaiy _
Milk and
milk products
sampled
between
1981-1989 in
Gennany
50 Mg/g
fluorine in
feed ration
for 5.5 yr
10 mg/g liter
fluorine in
water for
2 yr
0.04-1.2
Dabeka and McKenzie, 1995
0.01-1.7
885-6,918
0.072-0.64
0.01-0.8
0.045-0.51
Schamschula et al., 1988
Hillman et al., 1979
Dabeka and McKenzie, 1995
Schamschula et al., IS
0.019-0.16
Bergmann, 1995
Liver: 3.6
Kidney: 19.3
Heart: 4.6
Thyroid: 7.3
Liver: 2.2
Kidney: 16.8
Thyroid: 7.2
Heart: 2.2
Harvey, 1952
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15
Iodine
INTRODUCTION
The name iodine (I) is derived from thie Greek word iodes,
meaning violet. Iodine (atomic weighit 126.9045), a nonme-
tallic element of the halogen group, is volatile at ambient
temperature and pressure. It can exist in various oxidation
states with valences of "1, """l, ^3, """S, or "'"7, but the main
oxidation state is "1 as iodide. The term iodide refers to its
ionic form I". lodate refers to lO-^". Elemental iodine occurs
as a purple-black solid with rhombic crystalline structure that
sublimes into the gaseous form (Ij), giving off an intense
violet vapor and a characteristic odor. It is also a component
of fallout produced by nuclear explosions. Iodine is less re-
active than other halogens (fluorine [F], chlorine [CI], and
bromine [Br]) but readily forms compounds with other ele-
ments. It dissolves in alcohol, carbon disulfide, carbon tetra-
chloride, and chloroform, but it is only slightly soluble in
water. In water, hydrogen and iodine form hydrogen iodide.
Iodine forms compounds with certain nonmetals (e.g., car-
bon, nitrogen, phosphorus, and oxygen), and it can be dis-
placed by the other halogens. Among 36 isotopes of iodine
with masses between 108-143 (Chu et al., 1999), 14 yield
significant radiation. The naturally occurring isotopes of io-
dine, '^^I and '^^I, are stable and radioactive. The other iso-
topes of iodine are instable isotopes. Iodine"'^' is a radioac-
tive isotope with a half-life of 8 days. It is widely used to
diagnose abnormalities of the thyroid gland in humans and
experimental animals.
Iodine, the 64th most abundant element (10"^ percent of
Earth's crust), is widely distributed in nature and present in
both organic and inorganic substances in very small amounts.
The ocean is the primary source of iodine, containing be-
tween 50-60 l-ig/L. Only a few substances, such as the salt-
petre deposits of Chile and some marine products, have con-
centrations of up to 1,000-2,000 mg/kg. Iodine is present in
soil, air, and water and becomes a constituent of plants and
animals used for food. The average iodine concentration
in air, soil, freshwater, and animal body are 0.7 |ig/m-^.
300 Mg/kg, 5 Mg/1, and 0.4 mg/kg (WHO, 1998; ATSDR,
2004). The iodine content of water reflects the iodine con-
tent of the rocks and soils of the region. Thus, crops grown
in certain areas, such as the Ganges plains of India, are io-
dine deficient, and animals and humans in this area suffer
from a deficiency of this element. An important source of
iodine is caliche, a nitrate rock that contains up to 0.2 per-
cent iodine in the form of iodate salts. Iodine is also found as
an iodide in certain seaweeds.
Iodine was first isolated in 1811 by a French chemist,
Bernard Courtois, from seaweed ash during the making of
gunpowder. In 1895, Baumann discovered iodine in the hu-
man thyroid gland and the relationship of iodine deficiency
to enlargement of the thyroid gland was first clinically shown
by Marine and Kimball in 1922 (Hetzel and Dunn, 1989). A
comprehensive review of the historical aspects of goiter has
been published (Matovinovic, 1983). Iodine and its com-
pounds are used as supplements in feeds and foods (e.g.,
iodized salt), agricultural chemicals (e.g., herbicides and fun-
gicides), animal drugs (e.g., ethylenediamine dihydriodide
[EDDI]) and sanitizers (e.g., iodophors). EDDI is used at
relatively high levels to prevent or treat foot rot and soft
tissue lumpy jaw in cattle (Miller and Tillapaugh, 1966).
Iodophors are widely used in the dairy industry as teat dips
and udder washes. lodophor solutions are also used as sani-
tizing agents for cleansing equipment. In industry iodine is
used mainly as organoiodine compounds in pharmaceuticals,
photography, pigments, sterilization, dyestuffs, and rubber
manufacture.
ESSENTIALITY
Iodine is an essential element for animal species, includ-
ing humans, mainly because it is an integral component of
the thyroid hormones, 3,3',5-triiodothyronine (T3) and
3,3',5,5'-tetraiodothyronine (thyroxine, T^). Thyroid hor-
mones regulate cell activity and growth in virtually all tis-
sues and therefore are essential in intermediary metabolism.
182
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IODINE
183
reproduction, growth and development, hematopoiesis, cir-
culation, neuromuscular functioning, and thermoregulation.
The concentration of iodine in the environment, as well as in
plant material and water, is extremely variable throughout
the world and iodine deficiency disorders (IDD) can be a
major problem in both domestic animals and humans (Hetzel
and Dunn, 1989; Delange, 1994; Underwood and Suttle,
1999).
In all farm animals, deficiency is accompanied by thyroid
hyperplasia or "goiter" and a decrease in thyroglobulin con-
centration within the follicles of the thyroid gland. The
goitrous condition is a hyperplastic response of the thyroid
glands to an increased stimulation of thyroid growth by thy-
roid-stimulating hormones produced in the pituitary gland.
With mild iodine deficiency, the hyperplastic thyroid gland
can compensate for the reduced absorption of iodine (Hetzel
and Welby, 1997). Deficiency signs vary depending upon
the animal species and the severity of the deficiency. Calves
may be born hairless, weak, or dead. Fetal death can occur at
any stage of gestation, but cows often appear normal
(Hemken, 1960). Reproductive failures have been reported
in both male and female cattle, sheep, and pigs suffering
from goiter (Underwood and Suttle, 1999). Chickens may
show thyroid hyperplasia without a significant effect on
growth and reproductive performance. Laying hens fed diets
containing 0.01 to 0.02 mg I/kg, produced eggs of low hatch-
ability and poor embryonic development. While 0.35 mg
I/kg was adequate to maintain good hatchability, 0.75 mg
I/kg was not sufficient to prevent thyroid hyperplasia in em-
bryos (Rogler et al., 1961).
Goitrogenic substances in feed may increase iodine re-
quirement substantially (2- to 4-fold) depending on the
amount and type of this natural toxicant (Bell, 1984). Cy-
anogenetic goitrogens include thiocyanate derived from cya-
nide in white clover and the glucosinolates found in Bras-
sica seeds and forages (e.g., kale, turnips, and rapeseeds).
These thiocyanate compounds impair iodine uptake by the
thyroid, but their effect can be overcome by increasing di-
etary iodine intake. Several cases of fetal death, abortion, or
the birth of weak lambs or calves associated with hypothy-
roidism have been reported where plants containing goitro-
gens constituted an appreciable proportion of the diet during
pregnancy (Sinclair and Andrews, 1958). Goitrogens, par-
ticularly the thiooxazolidone type, readily pass from the
bloodstream to the milk of lactating animals and conse-
quently the milk possesses goitrogenic potency (Arstila et
al., 1969; Laurberg et al., 2002).
Recent estimates of iodine requirements (mg/kg diet) pub-
lished in NRC publications where diet does not contain
goitrogens are as follows: chicken and cats, 0.35; turkey,
0.40; beef cattle, 0.50; dairy cattle, 0.25 (growing) and 0.5
(lactating); sheep, 0.1-0.8; horses, 0.10; swine, 0.14; rats
and mice, 0.15; nonhuman primates, 2 (reviewed by
McDowell, 2003). Lactating animals require more dietary
iodine because approximately 10 percent or more of the io-
dine intake may be excreted in milk, depending upon the rate
of milk production (Miller et al., 1975). Iodine requirements
may also be influenced by genetic differences, climate, and
environment. The thyroid hormone secretion in certain ani-
mals has been shown to be inversely related to environmen-
tal temperature. Cattle, sheep, and goats show a significant
decrease in thyroid hormone production during the summer
(ARC, 1980).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Iodine is found in the organic forms in plants and animals
and in the inorganic form in natural water samples. Methods
for the identification and quantitative determination of io-
dine depend upon the type of compound and the matrices in
which it occurs. Iodine normally exists in nature as iodide
(L); however, other common forms include iodate (lO^) and
molecular iodine (Ij). For analysis of iodine in most biologi-
cal samples, a dissolution step (wet or dry ashing) is required
prior to analysis in order to convert and isolate it to a chemi-
cal or physical form suitable for detection. Spectrophotom-
etry was initially used for the determination of iodine based
on the iodized catalyzed reaction of cerium (IV) by arsenic
(III) in food and feeds.
Several analytical methods — including chromatography
(ion and gas), spectrometry, and neutron activation analy-
sis — are used to determine iodine in feeds and foods. The
ionic forms of iodine, iodide or iodate, can be determined
using ion chromatography where detection limits with con-
ductivity detection generally range between 0.1-lmg/L.
Other analytical techniques, particularly those based on ra-
dioiodine measurements, require highly specialized equip-
ment and multi-step sample preparation techniques, which
are prone to iodine loss or contamination. Due to the high
selectivity and sensitivity obtained by ICP-MS, it is com-
monly used for the quantitative determination of iodine in
biological tissues (Larsen and Ludwigsen, 1997; Julshamn
etal., 2001).
Some iodine species, such as hydrogen iodide, are volatile
at room temperature and therefore must be stabilized in sample
solutions at alkaline pH prior to ICP-MS determination. Vola-
tilization of iodine may lead to memory and adhesion effects
in ICP instruments, which may cause problems in sample in-
troduction systems. Several methods such as digestion using
perchloric acid in combination with nitric acid have been used
successfully to digest samples in polytetrafluoroethylene-lined
steel bombs. The acid mixture oxidizes potentially volatile
iodine species to nonvolatile species such as iodate. Other
analytical approaches using ICP-MS are based on alkali ex-
traction combining potassium hydroxide and tetramethylam-
monium hydroxide (TMAH) to determine iodine in milk or
serum by flow injection ICP-MS or use TMAH as a strong
alkali to measure iodine in diets supplemented with the ele-
ment. The microwave digestion system using 0.5 percent
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MINERAL TOLERANCE OF ANIMALS
ammonium solution lias also been successfully used for rapid
and sensitive determination of iodine (Baumann, 1990;
Vanhoe et al., 1993). Volatile and semi-volatile forms of or-
ganic iodine may be determined by gas chromatography and
gas chromatography-mass spectrometry.
REGULATION AND METABOLISM
Absorption and Metabolism
Ingested inorganic iodine and iodate are reduced to iodide
and absorbed almost completely from the gastrointestinal tract
(Hetzel and Maberly, 1986). In the ruminant, the rumen is the
major site of absorption of iodine and the abomasum is the
major site of endogenous secretion (Barua et al., 1964). After
absorption, the iodide is rapidly distributed throughout the
body. The major sites of iodine concentration are the thyroid
and the kidney. In addition, iodine is concentrated by the sali-
vary glands, mammary glands, gastric mucosa, placenta,
ovary, skin, and hair (Gross, 1962). In thyroid follicular cells,
iodine is transformed through a series of metabolic steps into
the thyroid hormones, T4 and T3. These two hormones ex-
press almost all of the biological effects of iodide. Other forms
of iodine in the thyroid include inorganic iodine, 3-
monoiodotyrosine (MIT), 3, 5 -diiodotyrosine (DIT), polypep-
tides containing thyroxine, and thyroglobulin.
Iodide trapped by the thyroid is oxidized by thyroid peroxi-
dase to active iodine, which iodinates the tyrosyl residues in
thyroglobulin. This large glycoprotein (MW 660,000), the
storage form of thyroid hormones, serves as the substrate for
iodination and coupling of peptide-linked iodotyrosines to T^
and T3. This coupling reaction is also catalyzed by thyroid
peroxidase and results in conversion of an alanine side chain
to dehydroalanine. Thyroglobulin consists of two polypeptide
subunits that undergo post-translational glycosylation and io-
dination prior to secretion into the lumen of the thyroid fol-
licle. The iodoprotein is reabsorbed into the thyroid cells and
hydrolyzed to release free thyroid hormones for secretion into
the circulation sytem and distribution to the peripheral tissues.
This process also occurs in lactating mammary glands and, to
a limited extent, in the ovum within the ovary. In other sites,
the element remains in the form of iodide.
Thyroglobulin in the colloid contains the greatest part of
iodine in a normal thyroid. Approximately 70 percent of the
dry weight of a thyroid gland is thyroglobulin. One mole of
thyroglobulin containing 1 percent iodine consists of 10-12
residues each of MIT and DIT, 3-4 residues of T4, and less
than one residue of T3. The percent iodine varies and is a
function of iodine in the diet. The colloid can store a sufficient
amount of thyroid hormones to supply the body needs of hu-
mans for several months (Taurog, 2000); however, the storage
time may vary among different animals. The iodide pool is
replenished continuously, exogenously from the diet and en-
dogenously from the saliva, gastric juice, and breakdown of
thyroid hormones and iodothyronines by deiodination. The
pool is in a dynamic equilibrium with the thyroid gland and
kidneys. Approximately 80-90 percent of iodine intake is ex-
creted via the kidneys in the urine (Vought and London, 1967;
Nath et al., 1992); other routes include saliva, bile, sweat, and
feces. In lactating animals, milk is also a major route of iodine
excretion. Undigested organic iodine is excreted in feces.
Thyroid honnones are primarily transported in blood mainly
(>99.7 percent) loosely bound to plasma proteins (thyroxine
binding protein, transthyretin, albumin, and lipoproteins). The
regulation of thyroid metabolism is a complex process, which
involves the thyroid, anterior pituitary, hypothalmus, and pe-
ripheral tissues (Hetzel and Welby, 1997). Thyroid-stimulating
hormones (TSH) from the pituitary gland stimulate thyroid
metabolism via cyclic AMP and the synthesis of thyroid hor-
mones. The TSH released from the pituitary is inhibited through
a feedback control by the thyroid hormones, and its release is
stimulated by thyrotropin-releasing hormones (TRH), a tripep-
tide (pyroglutamyl histidyl-prolinamide). Synthesis of TRH
occurs in the hypothalamus, and they are transported to the pi-
tuitary through blood vessels. The secretion of TRH from the
hypothalamus is in turn inhibited by T3. These interacting fac-
tors of the thyroid-pituitary-hypothalamus axis maintain ho-
meostasis with regard to thyroid hormones. Under normal con-
ditions most of the thyroid hormones released from the thyroid
gland are in the form of T^ and only a small amount as T3. Three
selenium-dependent enzymes, deiodinase (Type I, II, and III)
convert T4 into T3, the biological active form of thyroid hor-
mone (Arthur, 1999). Thiouracil only inhibits Type I deiodinase
(IDl). A major difference exists between ruminants and
nonruminants with respect to ID 1 ; this enzyme is particularly
important in brown tissue metabolism of newborn ruminants
and serves as source of T3 for other tissues (Nicol et al., 1994).
Free MIT and DIT are deiodinated by tissue deiodinases. Nor-
mal concentrations of thyroid hormones are necessary to main-
tain a wide range of essential physiological processes including
metabolic rate, protein and enzyme synthesis, thermoregula-
tion, and growth and development of most vital organs.
Fish and other aquatic organisms obtain iodine primarily
from gills and, to a lesser extent, from food sources. Rain-
bow trout derive 80 percent of their iodine from water, 19
percent from diet, and less than 1 percent from recycling
iodine originating from thyroid hormone degradation (Hunt
and Bales, 1979). When dietary uptake is low or absent, fish
are able to maintain their plasma iodine levels by uptake of
iodide from water and mobilization of this element from tis-
sue stores. Major differences exist between fish and mam-
mals in the handling of iodine and extrathyroidal metabo-
hsm of T4 and T3 (Higgs et al., 1982).
IVIetabolic Interactions and IVIechanism of Toxicity
The cellular functions of thyroid hormone are mediated
through triiodothyronine in a complex molecular mechanism
involving steroid and thyroid hormones and nuclear recep-
tors (Hetzel and Welby, 1997). Retinoic acid (vitamin A)
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IODINE
185
stimulates, synergistically with triiodothyronine, the produc-
tion of growth hormones in cultured cells. Goitrogenic sub-
stances in a wide range of vegetables and plant products are
capable of producing thyroid hyperplasia by interfering with
thyroid hormone synthesis. The pituitary responds by in-
creasing TSH output, thus causing thyroid gland hypertro-
phy in an effort to increase thyroid hormone production. In-
organic elements in diets that interfere with iodine
metabolism include: (1) high intake of fluorine, arsenic, and
calcium, (2) cobalt deficiency or excess, and (3) low manga-
nese intake (Underwood and Suttle, 1999). Higher amounts
of dietary potassium increase urinary loss of iodine in cattle
(Dennis and Hemken, 1978). Synthetic flavonoids have been
shown to interfere with iodine metabolism in a rat fetus by
crossing the placenta and reducing the availability of T^.
Iodine toxicosis in animals and humans markedly reduces
thyroidal iodine uptake, and the response is dependent on
dose and duration of iodine intake (Hetzel and Welby, 1997).
Excess iodine may result in either hypothyroidism, with or
without goiter, or hyperthyroidism (thyrotoxicosis), but the
mechanisms involved in these responses are not completely
understood. Numerous studies conducted on the mechanisms
of iodine toxicity show the following direct effects on thy-
roid glands: (1) inhibition of iodide transport and uptake by
the thyroid; (2) accumulation of iodotyrosines; (3) inflam-
mation and degeneration of follicular cells; and (4) damage
to follicular cells DNA. Indirect effects of iodine toxicosis
include: (1) changes in thyroid hormones transport in
plasma; (2) interference in TSH or transthyrectin metabo-
lism; (3) higher hepatic microsomal enzyme activities caus-
ing an increase in iodotyrosine excretion; and (4) poor ab-
sorption of thyroid hormones and their excretion in feces.
The adverse effects of iodine toxicosis may not be related
exclusively to the source of the iodine. Large doses of iodine
temporarily inhibit either organic iodine synthesis (Wolff-
Chaikoff effect), possibly by binding the active form of io-
dine as I3", or inhibit thyroglobulin proteolysis with reduc-
tion in hormone secretion. Both effects may contribute to the
stimulation of release of TSH from the pituitary gland and to
an increase in serum concentration of TSH and hypertrophy
of the thyroid gland. However, the thyroid gland adapts to
excess iodine by decreasing its transport into the cell. The
mechanisms for the Wolff-Chaikoff effect involve both io-
dide transport and iodination reactions, possibly through an
inhibition of the expression of sodium-iodine symport (NIS)
and thyroid peroxidase. This reaction is mediated by iodide
or an iodinated metabolic intermediate (Eng et al., 1999).
Iodine may escape when iodide transport into the thyroid
gland is either depressed to release it from inhibition of thy-
roid peroxidase or by other biochemical processes in the pro-
duction of iodothyronines (Sailer et al., 1998). Several
chemical inhibitors of iodine thyroid metabolism have been
identified (ATSDR, 2004).
The mechanism by which the iodide suppresses iodina-
tion and thyroid hormone release appears to involve inhibi-
tion of adenyl cylase. The stimulatory actions of TSH on the
thyroid gland, which include increased iodide transport and
increased iodination of thyroglobulin production and release
of T4 and T3, occur in response to an increase in intracellular
cAMP levels. Iodide inhibits adenylate cyclase in thyroid
follicle cells and decreases the TSH-induced rise in intracel-
lular cAMP. However, inhibitors of the iodination reaction,
such as prophylthiouracil, can prevent the effects of iodide
on adenylate cyclase. This indicates that the active inhibitor
may be an endogenous iodinated species, which is produced
in the reaction involving thyroid peroxidase.
Excess iodide intake may also be a contributing factor in
the development of lymphocytic thyroiditis in rats and mice
and autoimmune thyroiditis in humans. Hyperthyroidism has
been observed after iodine supplementation of iodine-defi-
cient populations. Chronic iodine deficiency results in thy-
roid gland proliferation and the development of autonomous
nodules that do not respond to serum TSH levels. Under
these conditions, excess amounts of iodine cause increased
levels and nonregulated thyroid hormone production
(Corvilain et al., 1998; Roti and Uberti, 2001).
SOURCES AND BIOAVAILABILITY
Iodine is distributed widely in nature in both organic and
inorganic forms in very small amounts. Iodine is present in
soil, air, and water and is a constituent of plants and animals
used for food. It exists in several chemical forms such as mo-
lecular iodine, iodide, iodate, and periodate. It is also subject
to oxidation-reduction reactions to yield other forms, as well
as microbial alkyation (e.g., methyl iodide). The highest con-
centration of iodine (0.5 to 2 g/kg) is found in nitrate deposits
(saltpetre) of Chile, where it was brought from Antarctic anti-
cyclonic airflows from the Pacific Ocean. Several marine al-
gae (brown, red, and green) cultured in Southeast Asia contain
high concentrations of iodine (up to 3 g I/kg). The iodine con-
tent of water reflects the iodine content of the rocks and soils
of the region. Iodine in water is in the form of iodide and
iodate. The iodine content in seawater averages 40- 60 |Jg/L
and unpolluted surface water contains 2- 4 |Jg/L (NRC, 1974).
In certain areas, where water is polluted with municipal waste-
water or urban run-off, the concentration may be as high as
8.7 |jg I/L (FDA, 1974; WHO, 1988). In Denmark, iodine
concentrations ranging from 2 to 139 |Jg/L have been reported
in drinking water (Pedersen et al., 1999; Rasmussen et al.,
2000). In surface water, the proportion of iodide to iodate de-
pends on the microbial activity and release of iodine from
terrestrial sources (De Luca Rebello et al., 1990). The iodine
content of river water may range from 0.1 to 18 |Jg/L (NRC,
1979), with a relative proportion of iodide to iodate of about
55:45. The average atmospheric iodine concentration ranges
between 2-52 ng/m^ (NRC, 1979; WHO, 1988), with gaseous
iodine exceeding particulate iodine by a factor of 2-6 (White-
head, 1984). The source of atmospheric iodine is mainly from
the vaporization of seawater; in this process, iodide is
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MINERAL TOLERANCE OF ANIMALS
oxidized by solar liglit. Ttie concentration of atmosphieric io-
dine is much higher over the ocean. Air pollution, particularly
the combustion of gasoline and oil, increases the iodine con-
centration in air.
The concentration of iodine in common feedstuffs is
highly variable. Protein sources of animal origin other than
fishery by-products contain relatively high amounts of this
element. Oilseed proteins or their concentrates contain 100
to 300 |Jg/kg and common cereal grains 40 to 100 |Jg/kg.
Concentrations of iodine in forage depend on the iodine con-
tent of soil. Many soils of the world are low in iodine and
goiter regions have been identified in many areas of all con-
tinents. During the glaciation period, iodine was swept away
and replaced by crystalline soil that lacks humus to retain
sufficient amounts of iodine. Heavy rain and flooding may
also leach iodine in certain areas. Soils near the oceans pro-
vide iodine to plants. Iodine concentrations in forages from
the Great Lakes region and the Northwest United States are
generally low enough to cause iodine deficiency in cattle
unless iodine is supplemented to diets.
Iodine sources permitted as feed additives include cal-
cium iodate, sodium iodate, potassium iodate, potassium
iodide, sodium iodide, EDDI, calcium iodobehenate,
cuprous iodide, 3,5-diiodosalicylic acid, pentacalcium
orthoperiodate, and thymol iodide (AAFCO, 2004). Iodine
occurs in foods largely as inorganic iodide. In this form, it is
almost completely absorbed from the gastrointestinal tract
(Underwood, 1977). The reported bioavailability of potas-
sium iodide, sodium iodide, EDDI, and pentacalcium
orthoperiodate for poultry, cattle, and rats is about 100 per-
cent, and for calcium iodide between 90-95 percent
(Ammerman and Miller, 1972; Miller and Ammerman,
1990). Diiodosalicylic acid is a stable compound and well
absorbed (80 percent) by rats, but it is not well utilized (~15
percent) by ruminants. Pentacalcium orthoperiodate and
EDDI are also more stable and less soluble and are added to
mineral blocks for licking by cattle to supply dietary iodine.
Limited information is available on the bioavailability of
iodine from plant material and animal by-products (Miller
and Ammerman, 1990).
Potassium iodate used in salt iodization and as a maturing
agent and dough conditioner in bread may appear in animal
and human food sources. Some non-food sources also sup-
ply iodine (e.g., iodine-containing drugs, antiseptics and dis-
infectants, and iodized oil used for intramuscular injections),
lodophors used as antiseptic agents for udder washes and
milking machines — as well as disinfection of tanks used for
handling, storing, and transport of milk — can increase the
iodine content of dairy products.
TOXICOSIS
Iodine toxicosis can result from a single large dose of
iodine or from repeated exposure to iodine concentrations
that exceed animal requirements. Several studies evaluating
oral ingestion of high concentrations of iodine are summa-
rized in Table 15-1. Several reviews are available on iodine
toxicity in mammals (NRC, 1980; SCF, 2002; McDowell,
2003; ATSDR, 2004); however, reports on iodine toxicity to
fish from diet and the aquatic environment are sparse. More
than a century ago, in practically all of the areas of Europe
affected by goiter, there was a wave of enthusiasm for the
use of some form of inorganic iodine to prevent and treat
goiter. It appears that indiscriminate use of various iodine
preparations was practiced with many cases of toxicosis. The
adverse effects of iodine in humans and animals have re-
sulted from the consumption of food supplements (e.g., io-
dized salt, bread or water), use of iodine-containing pharma-
ceuticals (e.g., oral, intramuscular injection, applications to
skin and mucus membrane), iodine in water supplies and
consumption of seaweed or animal meat containing thyroid
tissues. Iodine toxicity has been studied in many laboratory
animals, dogs, poultry, pigs, cattle, and goats. Significant
species differences exist in the tolerance to high levels of
iodine because of the differences in basal metabolic rate and
iodine metabolism. All species appear to have a wide margin
of safety for this element.
Single Dose
The reported oral LD^q in rats fed Nal was 3,320 mg I /kg
BW and the oral LDjqq for mice fed KI was 1,425 mg I /kg
BW (Clayton and Clayton, 1981). The oral LDj^ of iodate
and iodide in mice were 483-698 and 1,550-1,580 mg/kg
BW, respectively (Webster et al., 1957). Webster et al.
(1966) determined the minimum lethal dose and the maxi-
mum allowable dose of potassium iodate for dogs. Oral ad-
ministration of three single doses of potassium iodate (100,
200, or 250 mg/I kg BW) to dogs caused anorexia and occa-
sional vomiting at the low level; however, the higher levels
(200 and 250 mg/kg) caused death preceded by anorexia,
prostration, and coma (Webster et al., 1966). Severe retinal
degenerative changes have been reported in laboratory ani-
mals intravenously administered sodium iodate above 10 mg/
kg (Biirgi et al., 2001), but no such retinal changes were
observed in guinea pigs given potassium iodate in the drink-
ing water (Highman et al., 1955).
Acute and Chronic
The prolonged administration of large doses of iodine
markedly reduces iodine uptake by the thyroid, thus causing
antithyroidal or goitrogenic effects in many domestic and
experimental animals (Radostits et al., 2000). High levels of
iodide inhibit organic-iodine formation and saturate the ac-
tive-transport mechanism of this ion causing iodide goiter.
Significant species differences exist in tolerance to high di-
etary iodine intakes. In comparison to other trace element
toxicities, the dietary level of iodine necessary to cause toxi-
cosis is high relative to the minimal requirement. For ex-
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IODINE
187
ample, the margin of safety is 1 ,000 times ttie minimal re-
quirement of chickens (NRC, 1994) and pigs (Newton and
Clawson, 1974; NRC, 1998). A significant amount of data is
available on iodine toxicity in humans (Hetzel and Welby,
1997; ATSDR, 2004); however, limited research has been
conducted on acute and chronic toxicosis in domestic and
laboratory animals since the NRC last report (NRC, 1980).
Iodine toxicity data on laboratory animals is considered of
limited use for humans (ATSDR, 2004) because of the higher
sensitivity of this element to animals and some differences
in their dietary requirements and energy metabolism.
Although early work on the minimum toxic iodine intake
(as calcium iodate) for calves (80-112 kg) was close to 50
mg/kg diet, some animals showed adverse effects at lower
levels (Newton and Clawson, 1974; Newton et al., 1974).
Elevated levels of dietary iodine depressed growth rate and
feed intake, with the depression being significant for diets
containing 50, 100, or 200 mg/kg added iodine. The feeding
of either 100 or 200 mg I/kg, and in some cases lower levels,
produced toxic signs that included coughing and nasal dis-
charge. All levels of added iodine increased serum iodine,
and calves fed 200 mg/kg had significantly lower hemoglo-
bin and serum calcium levels. Calves fed diets with added
iodine had heavier adrenal glands, but there was no consis-
tent effect on the weight of the thyroid glands. Based on
trends in growth rate and adrenal weights, Newton et al.
(1974) concluded that 50 mg/kg diet appeared to be the mini-
mum toxic level for calves. Another study showed that calves
(100 kg) tolerated 20 and 40 mg I/kg from EDDI, but daily
gains were slightly depressed at 86 and 174 mg/kg diet (Fish
and Swanson, 1977). Iodine levels of 71, 140, and 283 mg/kg
had no effect, but a level of 435 mg/kg diet depressed daily
gains in yearling (320 kg) heifers (Fish and Swanson, 1977).
Mild and severe signs of iodine toxicosis were observed
in cattle fed 2.2 and 20 mg I/animal for 6 months
(Mangkoewidjojo et al., 1980).
Iodine toxicosis has been reported in adult dairy cows
with dietary intakes of 50 mg/day (NRC, 1980, 2001). High
concentrations of iodine in the diet increase iodine concen-
tration in milk. Humans are more susceptible to iodine thy-
ro toxicity than cows; therefore, the excess iodine in the dairy
cow must be limited due to public health concerns (Hetzel
and Welby, 1997). Feeding 170 mg I/day to high-yielding
cows for 30 days has resulted in abortions within a 68-day
period following treatment (Morrow and Edwards, 1981).
Other clinical signs of iodine toxicosis in dairy cows and
cattle include excessive nasal and ocular discharge, cough-
ing, nervousness, tachycardia, decrease in appetite, dermati-
tis and alopecia, exopthalmos, weight loss, decreased milk
production, susceptibility to infectious and respiratory dis-
eases, and increased mortality of dams (Olson et al., 1984;
Radostits et al., 2000).
Sheep were able to tolerate daily diets of 102 mg I/kg (as
KI) and 214 mg I/kg (as EDDI) for 22 days without any
adverse effects on growth and feed intake (McCauley et al..
1973). Body weight gains were depressed by daily intakes of
393 mg potassium iodide (300 mg iodine) or 562 mg EDDI
(450 mg iodine) per lamb per day. Other signs of iodine toxi-
cosis in sheep include cough, anorexia, hyperthermia, respi-
ratory diseases, and sometimes death (McCauley et al., 1973;
Paulikova et al., 2002).
A high incidence of goiter and leg weakness was reported
in foals born to mares fed 48-432 mg I/day (Baker and
Lindsey, 1968; Drew et al., 1975), although an upper tolerable
limit for horses has not been established. Excess iodine caused
osteoporosis and increase in serum phosphate and alkaline
phophatase levels in thoroughbred horses (Silva et al., 1987).
Pigs and chickens are more tolerant of excess iodine than
are cattle. Newton and Clawson (1974) fed levels of iodine
ranging from 10 to 1,600 mg/kg diet to growing-finishing
pigs and found that the minimum toxic level was between
400 and 800 mg/kg. Growth rate, feed intake, and hemoglo-
bin levels were depressed at 800 and 1,600 mg I/kg, and
liver iron levels were significantly depressed at 400 mg/kg
diet. A decrease in serum Tj concentrations was observed in
finishing pigs fed 10 mg I/kg diet (Schone and Leiterer,
1999). During lactation and the last 30 days of gestation,
neither 1,500 nor 2,500 mg I/kg diet affected reproduction in
sows (Arrington et al., 1965).
Early work on iodine toxicity in chickens showed that
their performance was not affected by feeding 500 mg I/kg
in the form of potassium iodide for up to 6 weeks (Wilgus et
al., 1953). More recent studies on oral iodine toxicity of
potassium iodide in chickens fed >900 mg I/kg showed
depressed growth and neurological clinical signs (Baker et
al., 2003); however, severe growth depression in chickens
fed 1,000-1,500 mg I/kg was totally reversed by dietary
supplementation of 50-100 mg Br/kg as sodium bromide. In
chicken and turkey laying hens, typical iodine toxicosis signs
observed with high intake of dietary iodine include decreased
egg production, egg size, and hatchability; low fertility;
enlarged thyroids in hatching chicks; and wiry down
(Perdomo et al., 1966; Arrington et al., 1967; Marcilese et
al., 1968; Christensen et al., 1991; Christensen and Ort,
1991). Turkey breeder hens are more sensitive to high dietary
iodine than chickens (Christensen and Ort, 1991). When lay-
ing chickens were fed 625 to 5,000 mg I/kg, egg production
varied inversely with the iodine level and ceased with dietary
levels of 5,000 mg/kg (Arrington et al., 1967). Early
embryonic death, reduced hatchability, and delayed hatch-
ing were also observed; however, egg production com-
menced within 1 week after cessation of feeding iodine. Diets
containing 5,000 mg I/kg caused an increase in serum
calcium level, as well as a marked reduction in egg produc-
tion and in the size of ovaries and oviducts of chickens
(Roland et al., 1977).
Marked differences exist between rabbits, hamsters,
and rats in their tolerance to high intakes of iodine. Mor-
tality was high in the offspring of rabbits fed 250 mg I/kg
in late gestation. However, the feeding of diets containing
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188
MINERAL TOLERANCE OF ANIMALS
2,500 mg/kg iodine to liamsters during gestation did not
affect deatii loss in ttie offspring (Arrington et al., 1965).
The survival of the offspring of rats was not affected by
feeding gestating female rats 500 mg I/kg, but high mor-
tality of the young was found when the gestation diets
contained 1,000 mg I/kg (Ammerman et al., 1964). No
gross lesions or abnormalities in mice or guinea pigs that
received 5,000 mg/L of potassium iodate in their drinking
water for several weeks were observed (Webster et al.,
1959). However, mice showed hemosiderin deposits in
the renal convoluted tubules.
High concentrations of dietary iodine (up to 14 mg/kg of
diet) in commercial and experimental feed have been shown
to cause a transient decrease in serum thyroid hormone lev-
els in cats (Tarttelin et al., 1992; Kyle et al., 1994; TartteUn
and Ford, 1994). Excessive dietary iodine intake may be
linked to feline hyperthyroidism; however, epidemiologic
studies have not identified a clear relationship between di-
etary iodine and adenomas or adenocarcinomas of the thy-
roid gland in cat (Scarlett, 1994). The minimum lethal dose
for potassium iodate administered orally to dogs was esti-
mated to be 200 to 250 mg/kg (Webster et al., 1966). In
puppies, high levels of iodine (5.6 mg/kg of diet) caused a
decrease in uptake of radioiodine by the thyroid gland
(Castillo et al., 2001a), and an excessive amount of iodine
present in some commercial feed caused impairment of thy-
roid function and hypothyroidism (Castillo et al., 2001b).
In humans, an iodine intake of 2 mg/day is considered
harmful (Hetzel and Welby, 1997). Oral iodine toxicosis has
occurred in certain areas of China and Japan in populations
exposed to chronic high intakes (50-80 mg/day) of iodine
(Wolff, 1969; NRC, 2001). Inhabitants of coastal regions
that consume large amounts of seaweed developed goiter
from high iodine intake (Hetzel and Welby, 1997). The re-
lease of at least 15 different radioactive isotopes of iodine
occurs as gases when uranium or plutonium atoms are split
resulting in typical signs of iodine toxicosis in animals and
humans (ATSDR, 2004). In 1986, the Chernobyl nuclear
accident in the Soviet Union caused excess iodine levels in
milk from dairy cows grazing on contaminated pastureland.
Children drinking contaminated milk showed iodine toxicity
(Kazakov et al., 1992; Nauman and Wolff, 1993).
Oral toxicity of iodine in fish has not been studied, but
high amount of iodine in water is toxic. An exposure of 8 mg
I/L was lethal to mullet (Gozlan, 1968). Acute toxicity of
iodine to channel fish varied with the exposure period
(Le Valley, 1982). Concentrations as low as 0.72 mg I/L re-
sulted in 100 percent mortality during a 24-hour exposure
period and 7.2 mg I/L within an hour. Mortality was caused
due to gill damage and asphyxiation.
Factors Influencing Toxicity
Natural or synthetic chemicals distributed in plants and
plant products used for animal feeds or for forage possess
goitrogenic properties and they affect iodine bioavailability
and metabolism (Talbot et al., 1976). Although the effects of
goitrogens on iodine toxicity are not clearly defined, changes
in thyroid metabolism associated with high intake of these
compounds may influence iodine toxicity as well as concen-
tration of iodine in tissue and animal products. There are two
types of goitrogens: thiocyanates and goitrin (L-5-vinyl-2-
thiooxazolidone). Among the naturally occurring goitrogens,
the best characterized are the glucosinolate derivatives iso-
lated from the Brassica species. Rapeseed, kale, cabbage, and
turnip contain high concentrations of goitrogens. Thiocyan-
ates inhibit the uptake of iodine in the thyroid, but their action
is reversible by iodine supplementation. However, goitrin in-
hibits thyroid hormone synthesis, probably through inhibition
of thyroid peroxidase, and this effect is irreversible by iodine
supplements (Talbot et al., 1976). Iodine supplementation al-
leviates the hypothyroidism and the adverse effects on perfor-
mance caused by feeding rapeseed meal to swine, and the ef-
ficacy of iodine can be improved by dietary copper
supplementation (Liidke and Schone, 1988; Schone et al.,
1988). Glucosinolates are inactivated by treatment with cop-
per sulphate solution. Moreover, extrusion of rapeseed with
barley eliminates its hypothyroidism effects (Maskell et al.,
1988). Other plant products such as soybean, cottonseed, lin-
seed meals, lentils, and peanuts also contain goitrogenic sub-
stances (Matovinovic, 1983; Fenwick et al., 2000).
Thiocyanates, perchlorates, and rubidium salts are known
to interfere with iodine uptake by the thyroid, and high lev-
els of arsenic can induce goiter in rats (Underwood, 1977).
Bromide, fluoride, cobalt, manganese, and nitrate may also
inhibit normal iodine uptake (Talbot et al., 1976). Excess
calcium intake has been shown to have an antithyroid effect
(Taylor, 1954). Adequate amounts of both iodine and sele-
nium are necessary for optimum thyroid metabolism (Hotz
et al., 1997). Selenium deficiency can influence iodine
bioavailability. High iodine intake when selenium is defi-
cient in diets of rats causes thyroid tissue damage as a result
of low thyroidal GSH-Px activity during thyroid stimulation
(Hotz et al., 1997).
However, a moderately low selenium intake normalized
the circulating T4 concentration in the presence of iodine
deficiency. Protein-calorie malnutrition may reduce iodine
absorption and thyroid iodine clearance and radiodide up-
take (Ingenbleek and Beckers, 1973, 1978). Excess dietary
iodine intake has been also shown to inhibit thyroid activity,
presumably by blocking the uptake of iodine by the thyroid
(Baker and Lindsey, 1968; Nagasaki, 1974; Newton and
Clawson, 1974; Fish and Swanson, 1983; Kaneko, 1989).
Certain food coloring agents (e.g., erythrosine), pharmaceu-
tical products, water purification tablets, and disinfectants
contain high amounts of iodine and are likely to increase
total intake of this element by the animal.
Few studies have been conducted to compare the relative
toxicity of various iodine compounds. No differences in toxic-
ity of sodium and potassium iodide to rats have been reported
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IODINE
189
(Arrington et al., 1965). lodate salts were more toxic than io-
dide salts in mice when administered orally, intraperitoneally,
or intravenously (Webster et al., 1957). Although absorption of
EDDI and sodium or potassium iodide does not differ widely in
dairy cows, EDDI was retained in most tissues longer than the
iodide salts (Miller and Swanson, 1973). The presence of food
in the stomach greatly decreased the acute toxic effects of orally
administered iodine to mice and guinea pigs, and small or inter-
mittent doses of potassium iodate in drinking water were better
tolerated by these animals than a single dose given by stomach
tube (Webster et al., 1959).
contain 4-10 |ig I/kg, which is located mainly in the yolk.
Feeding large amounts of iodine supplements and seaweed
to laying hens increases the amount in eggs by 100-fold or
more (Underwood and Suttle, 1999). When high con-
centrations of iodine (100-150 |Jg/day) were fed to laying
hens, the iodine concentration reached 50-120 |Jg/kg
(Marcilese et al., 1968). Iodine concentrations in fish muscle
vary widely (30 to 3,500 pg/kg) between species as well as
within species, and the concentration is generally higher in
marine fish (Varo et al., 1982; Lall, 1994; Julshamn et al.,
2001; Karl etal., 2001).
TISSUE LEVELS
Iodine concentration in animal products, particularly milk
and eggs, is directly influenced by iodine intake from feed
and water. In mammals, approximately 80 percent of total
iodine is distributed in the thyroid gland, and the remaining
amount is found in other soft tissues including muscle, liver,
kidney, and heart (Downer et al., 1981; Kaufmann and
Rambeck, 1998). The highest iodine concentrations are in
fish, shellfish, marine algae, and seaweed. Representative
iodine concentrations in tissues from various animals fed
normal or high levels of iodine are shown in Table 15-2.
Although iodine is a natural constituent of milk, the con-
centration is influenced by iodine intake, stage of lactation,
season, level of milk production, and the use of
iodine-containing disinfectants to maintain udder and dairy
equipment. Average iodine concentrations in milk of cows
fed 0, 40, 81, 162, 405, and 810 mg I/kg diet as EDDI was 8,
362, 895, 1,559, 2,036, and 2,383 pg/L (Miller et al., 1975).
The iodine content of milk varies seasonally, with higher
concentrations present in winter (80- 930 |Jg/L) than in sum-
mer (40-200 |Jg/L) (Varo et al., 1982; Dellavalle and
Barbano, 1984; Pennington, 1990; Lee et al., 1994; Larsen et
al., 1999; MAFF, 2000). The colostrum of dairy cows is
much higher in iodine than milk, and in late lactation there is
a decrease in concentration. A mean value of 264 ± 100 |Jg/L
for colostrom compared to 98 ± 82 |Jg/L for milk was re-
ported (Kirchgessner, 1959). Iodine content of milk is re-
duced below normal in goiter regions (Feng et al., 1999).
Dipping of teats in iodophor after milking increased the io-
dine levels from 89 and 94 |Jg/L to 127 and 152 |ig/L (Funke
et al., 1975). Average iodine concentration reported in sheep
and goat milk were 105.5 and 63.0 |Jg/L, respectively; how-
ever, the concentrations were much higher when these ani-
mals had access to mineral licks containing the element
(Travnicek and Kursa, 2001).
The early work of Fisher and Carr (1974) showed that the
iodine content of beef, pork, and mutton was low (27 to 45
|jg/kg). A wide range of iodine concentration ranging from 2
to 580 |Jg/kg has been reported in animal meat products from
Europe and the United States (Hemken et al., 1972; Hemken,
1979; Varo et al., 1982; Wenlock et al., 1982; Dunn, 1993;
Lee et al., 1994; Jahreis et al., 2001). Generally, hen eggs
MAXIMUM TOLERABLE LEVELS
The tolerance levels of domestic animals are based on clini-
cal signs of iodine toxicosis, and most animals tolerate high
dietary iodine concentrations relative to iodine requirements.
Iodine toxicity in domestic animals has not been properly
quantified. Based on available literature, maximum tolerable
levels (mg I/kg diet) suggested for iodine are cattle, 50; sheep,
50; swine, 400; chicken and turkey, 300. These values are
unchanged from those reported by NRC (1980) since recent
data do not support a change in these recommendations. Al-
though cattle can tolerate 50 mg/kg iodine, this level in the
diet may result in undesirably high levels of iodine in the milk.
Among the species studied, horses are most susceptible to io-
dine toxicity. High levels of iodine, for example of kelp con-
sumption by horses, cause goiter in the offspring of mares.
Assuming that mares consume 10 kg air dry diet daily, the
maximum tolerable level for iodine in horse diets is 5 mg/kg.
Laboratory animal models have been useful to study the
mechanism of iodine toxicity. However, the major
toxicokinetics data on oral exposure have been obtained in
experimental and clinical studies of humans using
biomarkers (e.g., urinary excretion, serum TSH, thyroid scin-
tillation scan, and antibodies) (ATSDR, 2004). Thus, unlike
other minerals, most toxicological studies conducted with
laboratory animals lack toxicokinetic data, and results do
not distinguish specific effects of an overdose of iodine or
iodate supplements (Biirgi et al., 2001). Mice showed
marked toxic effects of iodate administered in water for 4
weeks such as hemolysis and renal damages, which occurred
from 300 mg I/kg BW upward with a no-observable-effect
level (NOEL) at approximately 120 mg/kg BW. However,
guinea pigs exposed via the same route tolerated 300 mg/kg
BW without apparent effect. When given intravenously to
rats, doses above 10 mg I/kg BW were highly toxic to retina
(Biirgi etal., 2001).
HUMAN HEALTH
Iodine toxicity in humans is well documented and the
subject of several comprehensive reviews by national, re-
gional, and international organizations. Estimates of di-
etary intake of iodine have ranged from <50 |Jg/day in
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190
MINERAL TOLERANCE OF ANIMALS
iodine-deficient regions to >10 mg/day in populations that
regularly consume seaweeds high in iodine. The NRC's
Recommended Dietary Allowance (RDA) for iodine is
150 |ig/day (2.1 |jg/kg/day for a 70-kg adult), with addi-
tional allowances for 70 and 140 pg/day during pregnancy
and lactation, respectively (NRC, 2001). An upper toler-
able level of iodine intake for an adult human is 1,100 |Jg/
day (NRC, 2001). A provisional maximum tolerable daily
intake of 1 mg/day (equivalent to 17 |Jg/kg BW) from all
sources has been recommended by WHO (1988). In coun-
tries with long-standing IDD, the intake should not ex-
ceed 500 |Jg I/day to prevent hyperthyroidism (AFSSA,
2001). A minimal risk level (MRL) of 0.01 mg/kg/day
has been derived for acute duration of oral exposure (1-
14 days) to iodine, which is based on a NOAEL of 0.024
mg/kg/day in healthy adult males (ATSDR, 2004). This
NOAEL value derived from human adults may also be
applicable to children and the elderly. Genotoxicity and
carcinogenicity data for iodine are limited and are nonex-
istent for iodate (Biirgi et al., 2001).
FUTURE RESEARCH NEEDS
The toxicity of iodine in most domestic and aquatic ani-
mals should be better defined. There is a need to determine
the mechanisms involved in iodine metabolism, particularly
the interaction of iodine with other nutrients such as sele-
nium, bromine, and iron. Although the toxicity of iodine for
humans has been extensively studied, there is a need for more
research to better establish the basis for beneficial or essen-
tial action of iodine, and the intake below which this action
is compromised. This would be helpful in setting the lower
limits of toxicity standards for iodine and would allow better
use of animal by-products in human nutrition.
SUMMARY
Iodine is an essential element for all animals. Its only
known function in the body is in the synthesis of the thy-
roid hormones. Sodium iodide, potassium iodide, and eth-
ylenediamine dihydroiodide are well utilized as a source of
iodine. Limited information is available on the
bioavailability of this element from plant and animal by-
products. Species differ widely in their susceptibility to
iodine toxicity, but all animals can tolerate iodine levels far
in excess of their requirements for this element. Feeding
excessive levels of iodine has resulted in decreased egg
production in hens, inhibition of lactation in rats, decreased
hemoglobin levels in pigs, and goiter and reduced thyroid
hormone synthesis in several species. Increasing the iodine
intake of lactating cows and laying hens increases the lev-
els of iodine in milk and eggs.
REFERENCES
AAFCO (Association of America Feed Control Officials). 2004. Official
publication of tlie Association of American Feed Control Officials, Inc.
West Lafayette, IN.
AFSSA (Agence Fran9aise de Securite Sanitaire des Aliments). 2001. Re-
port from the AFSSA Expert Committee on Human Nutrition. Vitamin
and mineral fortification of commonly eaten foods: meeting the nutri-
tional and safety needs of consumer. 8 November 200 1 . Case No. 2000-
SA-0239. Annex4b, p.l5.
Ammerman, C. B., and S. M. Miller. 1972. Biological availability of minor
mineral ions: a review. J. Anim. Sci. 35:681-694.
Ammerman, C. B., L. R. Arrington, A. C. Warnick, J. L. Edwards, R. L.
Shirley, and G. K. Davis. 1964. Reproduction and lactation in rats fed
excessive iodine. J. Nutr. 84:108-112.
ARC (Agriculture Research Council). 1980. The nutrient requirements of
ruminant livestocii. Slough, UK: Commonwealth Agriculture Bureaux.
Arrington, L. R., R. N. Taylor, Jr., C. B. Ammerman, and R. L. Shirley.
1965. Effects of excess dietary iodine upon rabbits, hamsters, rats and
swine. J. Nutr. 87:394-398.
Arrington, L. R., R. A. Santa Cruz, R. H. Harms, and H. R. Wilson. 1967.
Effects of excess dietary iodine upon pullets and laying hens. J. Nutr.
92:325-330.
Arstila A., F. E. Krusius, and P. Peltola. 1969. Studies on the transfer of
thio-oxazolidone-type goitrogens into cow's milk in goitre endemic dis-
tricts of Finland and in experimental conditions. Acta Endocrinol.
(Copenhagen) 60:712-718.
Arthur, J. R. 1999. Functional indicators of iodine and selenium status.
Proc. Nutr. Soc. 58:507-512.
ATSDR (Agency for Toxic Substances and Disease Registry). 2004. Toxi-
cological profile for iodine. Atlanta, GA: Agency for Toxic Substances
and Disease Registry, U.S. Department of Health and Human Services,
Public Health Service. Available at http://www.atsdr.cdc.gov/
toxprofiles/tpl58.html. Accessed on April 7, 2005.
Baker, D. H., T. M. Parr, and N. R. Augspurger. 2003. Oral iodine toxicity
in chicks can be reversed by supplemental bromine. J. Nutr. 133:2309—
2312.
Baker, H. J., and J. R. Lindsey. 1968. Equine goiter due to excess dietary
iodide. J. Am. Vet. Med. Assoc. 153:1618-1630.
Barua, J.,R. G. Gragle, and J. K.Miller. 1964. Sites of gastrointestinal-blood
passage of iodide and thyroxine in young cattle. J. Dairy Sci. 47:539—
541.
Baumann, H. 1990. Rapid and sensitive determination of iodine in fresh
milk and milk powder by inductively coupled plasma-mass spectrom-
etry (ICP-MS). Fresenius J. Anal. Chem. 338:809-812.
Bell, J. M. 1984. Nutrients and toxicants in rapeseed meal: a review. J.
Animal Sci. 58:996-1010.
Btirgi, H., T. Schafner, and J. P. Seller. 2001. The toxicology of iodate: a
review of the literature. Thyroid 11:449^56.
Brzoska, F., H. Pyska, B. Brzoska, and W. Wiewiora. 2000. Effect of iodine
intake in daily ration on iodine content in milk and iodine status of dairy
cows. Rocz. Nauk. Zootech. 27:103-1 16.
Castillo, v., J. Lalia, M. Junco, G. Sartorio, A. Marquez, M. Rodriguez, and
M. Pisarev. 2001a. Changes in thyroid function in puppies fed a high
iodine commercial diet. Vet. J. 16:80-84.
Castillo, v., M. Pisarev, J. Lalia, M. Junco, M. Rodriguez, R. Cabrin, and
A. Marquez. 2001b. Commercial diet induced hypothyroidism due to
high iodine. A histological and radiological analysis. Vet. Quart.
23:218-223.
Christensen, V. L., and J. F. Ort. 1991. Iodine toxicity in large white turkey
breeder hens. Poult. Sci. 70:2402-2410.
Christensen, V. L., W. E. Donaldson, J. F. Ort, and J. E. Grimes. 1991.
Influence of diet mediated maternal thyroid alterations on hatchability
and thyroid metabolism of turkey embryos. Iodine toxicity in large tur-
key hens. Poult. Sci. 70:1594-1601.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
IODINE
191
Chu, S. Y. F., L. P. Ekstrom, and R. B. Firestone. 1999. Isotope explorer:
www table of radioactive isotopes. Bericeley: The Lund/LBNL Nuclear
Data Search. Available at http://nucleardata.nuclear.lu.se/nucleardata/
toi/listnuc.asp. Accessed on April 7, 2005.
Clayton, G. D., and F. E. Clayton. 1981. In Patty's Industrial Hygiene and
Technology, 3rd ed., G. D. Clayton and F. E. Clayton, eds. New York:
John Wiley and Sons.
Corvilain, B., J. Van Sande, and J. E. Dumont. 1998. Autonomy in endemic
goitre. Thyroid 8:107-113.
Delange, F. 1994. The disorders induced by iodine deficiency. Thyroid
4:107-128.
Dellavalle, M. E., and D. M. Barbano. 1984. Iodine content of milk and
other foods. J. Food Protec. 47:678-684.
De Luca Rebello, A., F. W. Herms, and K. Wagener. 1990. The cycling of
iodine as iodate and iodide in a tropical estuarine system. Mar. Chem.
29:77-93.
Dennis, R. J., and R. W. Hemken 1978. Potassium requirement of dairy
cows in early and mild lactation. J. Dairy Sci. 61:757—762.
Downer, J. V., R. W. Hemken, J. D. Fox, and L. J. Bull. 1981. Effect of
dietary iodine on tissue iodine content of the bovine. J. Anim. Sci.
52:413^17.
Drew, B., W. P. Barber, and D. G. Williams. 1975. The effect of excess
iodine on pregnant mares and foals. Vet. Rec. 97:93-95.
Dunn, J. T., and F. Delange. 2001. Damaged reproduction: the most impor-
tant consequence of iodine deficiency. J. Clin. Endocrin. Met. 86:2360—
2363.
Eng, P. H. K., G. R. Cardona, S. L. Fang, M. Previti, S. Alex, N.
Carrasco, and W. W. Chin. 1999. Escape from acute Wolff-Chaikoff
effect is associated with a decrease in thyroid sodium/iodide
symporter messenger ribonucleic acid and protein. Endocrinology
140:3404-3410.
FDA (U.S. Food and Drug Administration). 1974. Iodine in foods: chemi-
cal methodology and sources of iodine in human diet. PB, 233-559.
Washington, D.C.: U.S. Food and Drug Administration, Bureau of
Foods, Division of Nutrition.
Feng J., S. Lai, Z. Feng, J. Feng, S. J. Lai, and Z. G. Feng. 1999. Effects of
high iodine diets on the iodine content of milk and milk quality of cows.
Chin. J. Anim. Sci. 35:26-27.
Fenwick, G. R., R. K. Heaney, and R. Mawson. 2000. Glucosinolates. Pp.
1^1 in Toxicants of Plant Origin, Vol II, P. R. Cheeke, ed. Boca Raton,
FL: CRC Press.
Fish, R. E., and E. W. Swanson. 1977. Iodine tolerance of calves, yearlings,
dry cows, and lactating cows. J. Dairy Sci. 60 (Suppl. 1):151— 156.
Fish, R. E., andE. W. Swanson. 1982. Effectsof excessive intakes of iodine
upon growth and thyroid function of growing Holstein heifers. J. Dairy
Sci. 64:605-610.
Fish, R. E., and E. W. Swanson. 1983. Effect of excessive iodide adminis-
tered in the dry period on thyroid function and health of dairy cows and
their calves in the periparturtient period. J. Anim. Sci. 56:162-172.
Fisher, K. D., and C. J. Carr. 1974. Iodine in foods: chemical methodology
and sources of iodine in the human diet. Life Sciences Research Office,
Federation of American Societies for Experimental Biology, Bethesda,
MD. PB-233 599. Springfield, VA: National Technical Information
Service.
Funke, H., K. Iwarrson, S. O. Olsson. P. Salomonsson, and P. Stranberg.
1975. Effect of teat dipping with iodophors on udder health and iodine
content of milk. Nord. Veterinaermed. 27:270-284.
Gozlan, R. S. 1968. Isolation of iodine-producing bacteria from aquaria.
Anionic Leeuwenhoek 34:226-230.
Gross, J. 1962. Iodine and bromine. In Mineral Metabolism, C. L. Comar
and F. Bronner, eds. New York: Academic Press.
Haggard, D. L., H. D. Stowe, G. H. Conner, and D. W. Johnson. 1980.
Immunologic effects of experimental iodine toxicosis in young cattle.
Am. J. Vet. Res. 41:539-543.
Hemken, R. W. 1960. Iodine. J. Dairy Sci. 53:1138-1143.
Hemken, R. W. 1979. Factors that influence the iodine content of milk and
meat: a review. J. Anim. Sci. 48:981-985.
Hemken, R. W., J. H. Vandersall, M. A. Oskarsson, and L. R. Fryman.
1972. Iodine intake related to milk iodine and performance of dairy
cattle. J. Dairy Sci. 55:931-934.
Herzig, I., B. Pisarikova, I. Diblikova, and P. Suchy. 2001. Iodine concen-
tration in porcine blood, urine, and tissues after a single dose of iodised
oil. Vet. Med. (Prague) 46:153-159.
Hetzel, B. S., and J. T. Dunn. 1989. The iodine deficiency disorders: their
nature and prevention. Annu. Rev. Nutr. 9:21—38.
Hetzel, B. S., and G. F. Maberly. 1986. Iodine. Pp. 139-208 in Trace Ele-
ments in Human and Animal Nutrition, 5th ed.. Vol 2, W. Mertz, ed.
New York: Academic Press.
Hetzel B. S., and M. C. Welby. 1997. Iodine. Pp. 557-582 in Handbook of
Nutritionally Essential Mineral Elements, B. L. O'Dell and R. A. Sunde,
eds. New York: Marcel Dekker.
Higgs, D. A., U. H. M. Fagerlund, J. G. Eales, and J. R. McBride. 1982.
Application of thyroid and steroid hormones as anabolic agents in fish
culture. Comp. Biochem. Physiol. 73B: 143-1 76.
Highman, B., S. H. Webster, and M. E. Rice. 1955. Degeneration of retina
and gastric parietal cells and other pathologic changes following admin-
istration of iodates. Fed. Proc. 14:407 (Abstr.).
Hillman, D., and A. R. Curtis. 1980. Chronic iodine toxicity in dairy cattle:
blood chemistry, leukocytes, and milk iodine. J. Dairy Sci., 63:55-63.
Hotz, C. S., D. W. Fitzpatrick, K. D. Trick, and M. R. L'Abbe. 1997. Di-
etary iodine and selenium interact to affect thyroid hormone metabo-
lism of rats. L Nutr. 127:1214-1218.
Hunt, D. W. C, and J. G. Eales. 1979. Iodine balance in rainbow trout
(Salmo gairdneri) and effects of testosterone propionate. J. Fish Res.
Board Can. 36:282-285.
Ingenbleek, Y., and C. Beckers. 1973. Evidence for intestinal malabsorp-
tion of iodine in protein-calorie malnutrition. Am. J. Clin. Nutr.
26:1323-1330.
Ingenbleek, Y., and C. Beckers. 1978. Thyroidal iodate clearance and
radioiodide uptake in protein-calorie malnutrition. Am. J. Clin. Nutr.
31:408^15.
Jahreis, G., W. Hausmann, G. Kiessling, K. Franke, and M. Leiterer. 2001.
Bioavailability of iodine from normal rich diets in dairy products results
in balance studies in women. Exp. Clin. Endocrinol. Diabetes 109:163-
167.
Julshamn, K., L. Dahl, and K. Eckhoff. 2001. Determination of iodine in
seafood by inductively coupled plasma/mass spectrometry. J. Assoc.
Off. Anal. Chem. 84:1976-1983.
Kaneko, J. J. 1989. Thyroid function. In Clinical Biochemistry of Domestic
Animals, 4th ed,, J. J. Kaneko, ed. San Diego: Academic Press.
Karl, H., W. Munkner, S. Ki'ause, and I. Bagge. 2001. Determination of
spatial variation and distribution of iodine in fish. Dtsch. Lebebsm.-
Rundsch. 97:89-96.
Kaufmann, S., and W. A. Rambeck. 1998. Iodine supplementation in
chicken, cow and pig feed. J. Anim. Physiol. Anim. Nutr. 80:147—152.
Kazakov, V. S., E. P. Demidchik, and L. N. Astakhova. 1992. Thyroid
cancer after Chernobyl. Nature (Lond.) 359:21-22.
Kirchgessner, M. 1959. Interactions between different elements in
colostrums and milk. Z. Tierphysiol. Tierernaehr. Futtermittelkd.
14:270-277.
Kyle A., M. Tarttelin, R. Cooke, and H. Ford. 1994. Serum free thyroxine
levels in cats maintained on diets relatively high or low in iodine. N. Z.
Vet. J. 42:101-103.
Lall, S. P. 1994. Macro and trace elements in fish and shellfish. Pp. 187—
213 in Fish and Fishery Products, Composition, Nutritive Properties
and Stability. E. Ruiter, ed. Wallingford, UK: CAB International.
Larsen, E. H., andM. B. Ludwigsen. 1997. Determination of iodine in food-
related certified reference materials using wet ashing and detection by
inductively coupled plasma mass spectrometry. J. Anal. At. Spectrom.
12:435^39.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
192
MINERAL TOLERANCE OF ANIMALS
Larsen, E. H., P. Knuthsene, and M. Hansen. 1999. Seasonal and regional
variations of iodine in Danish dairy products determined by inductively
coupled plasma mass spectrometry. J. Anal. At. Spectrom. 14:41^14.
Laurberg, P., S. Andersen, N. Knudsen, L. Ovesen, S. B. Nahr, and 1. B.
Pendersen. 2002. Thiocyanate in food and iodine in milJc: from domes-
tic animal feeding to improved understanding of cretinism. Thyroid
12:897-902.
Le Valley, M. J. 1982. Acute toxicity of iodine to channel catfish (Ictalurus
punctatus). Bull. Environ. Contam. Toxicol. 29:7—11.
Lee, S. M., J. Lewis, D. H. Buss, G. D. Holcombe, and P. R. Lawrence.
1994. Iodine in British foods. Br. J. Nutr. 72:435-446.
Ltidke, H., and F. Schone. 1988. Copper and iodine in pig diets with high
glucosinolate rapeseed meal. 1. Performance and thyroid hormone sta-
tus. Anim. Feed Sci. Technol. 22:33^3.
MAFF (Ministry of Agriculture Fisheries and Food). 2000. Iodine in milk.
Food Surveillance Information Sheet No. 127. Available at http://
www.food.uk/science/survellance/maffinfo/2000/maff-2000- 1 98. Ac-
cessed April 7, 2005.
Mangkoewidjojo, S., S. D. Sleight, and E. M. Convey. 1980. Pathological
features of iodine toxicosis in calves. Am. J. Vet. Res. 7:1057-1061.
Marcilese, N. A., R. H. Harms, R. M. Valsechhi, and L. R. /Vrrington. 1968.
Iodine uptake by ova of hens given excess iodine and effect upon ova
development. J. Nutr. 94:117-120.
Maskell, L., M. Ellis, and R. Smithard. 1988. Nutritive value of pig diets con-
taining extraded or milled full-fat rapeseed. Anim. Prod. 46:522 (Abstr.).
Matovinovic, J. 1983. Endemic goitre and cretinism at the dawn of the third
millennium. Annu. Rev. Nutr. 3:341^12.
McCauley, E. H., J. G. Linn, and R. D. Goodrich. 1973. Experimentally
induced iodide toxicosis in lambs. Am. J. Vet. Res. 34:65-70.
McDowell, L. R. 2003. Minerals in Animal and Human Nutrition.
Amsterdam: Elsevier Science B.V.
Miller, E. R., and C. B. Ammerman. 1990. Iodine bioavailability. Pp. 157-
168 in Bioavailability of Nutrients for Animals: Amino Acids, Miner-
als, Vitamins, C. B. Ammerman, D. H. Baker, and A. J. Lewis, eds. San
Diego: Academic Press.
Miller, J. 1., and K. Tillapaugh. 1966. Iodide medicated salt for beef cattle.
Cornell Feed Service No. 62. Ithaca: Cooperative Extension Service,
Cornell University.
Miller, J. K., and E. W. Swanson. 1973. Metabolism of ethylenediamine-
dihydriodide and sodium or potassium iodide by dairy cows. J. Dairy
Sci. 56:378-384.
Miller, J. K., E. W. Swanson, and G. E. Spalding. 1975. Iodine absorption,
excretion, recycling and tissue distribution in the dairy cow. J. Dairy
Sci. 58:1578-1593.
Morrow, D. A., and L. Edwards. 1981. Effects of iodine toxicity on repro-
duction in a daily herd. Bovine Prac. 16:1 14— 1 18.
Nagasaki, M. S. 1974. Effects of excess quantities of iodide. Pp. 165— 172 in
Thyroid, Vol. Ill, M. A. Greer and D. H. Solomon, eds. Washington,
D.C.: American Physiological Society.
Nath, S. K., B. Moinier, F. Thuiller, M. Roninger, and J. F. deSjeux. 1992.
Urinary excretion of iodine and fluoride from supplemented food grade
salt. Int. J. Vitam. Nutr. Res. 62:66-72.
Nauman, J., and J. Wolff. 1993. Iodide prophylaxis in Poland after the
Chernobyl reactor accident: benefits and risks. Am. J. Med. 94(5):524— 532.
Newton, G. L., and A. J. Clawson. 1974. Iodine toxicity: physiological
effects of elevated dietary iodine on pigs. J. Anim. Sci. 39:879-884.
Newton, G. L., E. R. Bamck, R. W. Harvey, and M. B. Wise. 1974. Iodine
toxicity. Physiological effects of elevated dietary iodine on calves. J.
Anim. Sci. 38:449^55.
Nicol, F., H. Lefrane, J. R. Arthur, and P. Trayhurn. 1994. Characterization
and postnatal development of 5'-deiodinase activity in goat perirenal
fat. Am. J. Physiol. 267(1 Pt 2): R 144-149.
NRC (National Research Council). 1974. Nutrients and Toxic Substances
in Water for Livestock and Poultry. Washington, D.C.: National Acad-
emy Press.
NRC. 1979. A dynamic model of the global iodine cycle for the estimation
of dose to the world population from releases of iodine- 129 to the envi-
ronment. U.S. Nuclear Regulatory Commission, Division of Safeguards,
Fuel Cycle, and Environmental Research, l/\E-SDM-257.
NRC. 1980. Mineral Tolerance of Domestic Animals. Washington, D.C.:
National Academy Press.
NRC. 1994. Nutrient Requirements of Poultry, 9th rev. ed. Washington,
D.C.: National Academy Press.
NRC. 1998. Nutrient Requirements of Swine, 10th rev. ed. Washington,
D.C.: National Academy Press.
NRC. 2001. Pp. 258-259 in Dietary Reference Intakes of Vitamin A, Vita-
min K, Ai'senic, Boron, Chromium, Copper, Iodine, Iron, Manganese,
Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, D.C.:
National Academy Press.
Olson, W. G., J. B. Stevens, J. Anderson, and D. W. Haggard. 1984. Io-
dine toxicosis in six herds of dairy cattle. J. Am. Vet. Med. Assoc.
184:179-181.
Paulikova, 1., G. Kovac, J. Bires, S. Paulik, H. Seidel, and O. Nagy. 2002.
Iodine toxicity in ruminants. Vet. Med. (Prague) 47(12):343— 350.
Pedersen, K. M., P. Laurberg, S. Nohr, A. Jorgensen, and S. Andersen.
1999. Iodine in drinking water varies more than 100-fold in Denmark.
Importance for iodine content of infant formulas. Eur. J. Endocrinol.
140:400^03.
Pennington, J. A. T. 1990. Iodine concentration in U.S. milk: variations due
to time, season and region. J. Dairy Sci. 73:3421—3427.
Perdomo, J. T., R. H. Harms, and L. R. Arrington. 1966. Effect of dietary
iodine upon egg production, fertility and hatchability. Proc. Soc. Exp.
Biol. Med. 122:758-760.
Radostits, O., C. Gay, D. Blood, K. Hinchcliff, J. Ai-undel, D. Jacobs, K.
Leslie, B. Ikede, R. McKenzie, andD. Bildfell. 2000. Diseases caused
by deficiencies of mineral nutrients. Pp. 1480-1514 in Veterinary
Medicine: A Textbook of Diseases of Cattle, Sheep, Pigs, Goats and
Horses, O. Radostits, C. Gay, D. Blood, and K. Hinchcliff, eds. Lon-
don: W. B. Saunders.
Rasmussen, L. B., E. R. Larsen, and L. Ovesen. 2000. Iodine content in
drinking water and other beverages in Denmark. Eur. J. Clin. Nutr.
54:57-60.
Rogler, J. C, H. E. Parker. F. N. Andrews, and C. W. Carrick. 1961. The
iodine requirements of the hen. 2. Hens reared on a diet deficient in
iodine. Pouh. Sci. 40:1554-1562.
Roland, D. A., S. T. McCready, R. H. Stonerock, and R. H. Harms. 1977.
Hypercalcemic effect of potassium iodide on serum calcium in domes-
tic fowl. Poult. Sci. 56:1310-1314.
Roti, E., and E. Uberti. 2001. Iodine excess and hyperthyroidism. Thyroid
11:493-500.
Rys, R., E. Wir-Konas, H. Pyska, M. Kuchta, and M. Pietras. 1997. Changes
in egg iodine concentration in thi'ee hen strains in relation to iodine level
in diets. Rocz. Nauk. Zootech. 24:229-242.
Sailer, B., H. Fink, and K. Mann. 1998. Kinetics of acute and chronic iodine
excess. Exp. Clin. Endocrinol. Diabetes 106 (Suppl. 3):S34— S38.
Scarlett, J. M. 1994. Epidemiology of of thyroid diseases of dogs and cats.
Vet. Clin. North Am. Small An. 24(3):477^86.
SCF (Scientific Committee for Food). 2002. Opinion of the scientific com-
mittee on food on the tolerable upper intake level of iodine. Brussels:
The European Commission. Available at http://europa.eu.int/comm/
food/fs/sc/scf/index_en.html. Accessed on April 7, 2005.
Schone, F., and M. Leiterer. 1999. Iodine in the nutrition of the pig. Re-
quirement - supply - oversupply. Landbauforsch. Volkenrode SH
193:216-222.
Schone, F., H. Ltidke, A. Hennig, and G. Jahi'eis. 1988. Copper and iodine
in pig diets with high glucosinolate rapeseed meal. 11. Influence of io-
dine supplements for rations with rapeseed meal untreated or treated
with copper ions on performance and thyroid hormone status of grow-
ing pigs. Anim. Feed Sci. Technol. 22:45-59.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
IODINE
193
Silva, C. A., H. Merkt, P. N. Bergamo, S. S. Barros, C. S. Barros, M. N.
Santos, H. O. Happen, H. Heidemann, and H. Meyer. t987. Conse-
quences of excess iodide supply in a tliorouglibred stud in Brazil. J.
Reprod. Pert. 35:529-533.
Sinclair, D. P., and E. D. Andrews. 1958. Prevention of goitre in new-born
lambs from kale-fed ewes. N. Z. Vet. J. 6(3):87-95.
Talbot, J. M., K. D. Fisher, and C. J. Carr. 1976. A review of the effects of
dietary iodine on certain thyroid disorders. Bethesda, MD: Life Sci-
ences Research Office, Federation of American Societies for Experi-
mental Biology.
Tarttelin, M., and H. Ford. 1994. Dietary iodine level and thyroid function
in the cat. J. Nutr. 124: 2577S-2578S.
Tarttelin, M., L. Johnson, R. Cooke, H. Ford, and C. Feek. 1992. Serum free
thyroxine levels responds inversely to changes in levels of dietary io-
dine in the domestic cat. N. Z. Vet. J. 40:66-68.
Taurog, A. M. 2000. Hormone synthesis: thyroid iodine metabolism. Pp.
61-85 in The Thyroid, L. E. Bravermann and R. D. Utiger, eds. Phila-
delphia: Lippincott, Williams and Wilkins.
Taylor, S. 1954. Calcium as a goitrogen. J. Clin. Endocrinol. Metab.
14(11):1412-1422.
Travnicek, J., and J. Kursa. 2001. Iodine concentration in milk of sheep and
goats from farms in South Bohemia. Acta Vet. Brno. 70:35^2.
Underwood, E. J. 1977. Trace Elements in Human and Animal Nutrition,
4th ed. New York: Academic Press.
Underwood, E. J., and N. F. Suttle 1999. The Mineral Nutrition of Live-
stock, 3rd ed. New York: CABI Publishing.
Vanhoe, H., F. Van Allemeersch, J. Versieck, and R. Dams. 1993. Effect of
solvent type on the determination of total iodine in milk powder and
human serum by inductively coupled plasma mass spectrometry. Ana-
lyst 118:80-89.
Varo, P., E. Saari, and P. Kovistoinen. 1982. Iodine in Finnish foods. Int. J.
Vitam. Nutr. Res. 52:80-89.
Vought, R. L., and W. T. London. 1967. Iodine intake, excretion and thyroi-
dal accumulation in healthy subjects. J. Clin. Endocrinol. Met. 27:913—
919.
Webster, S. H., M. E. Rice, B. Highman. and W. F. Von Oettingen. 1957.
The toxicology of potassium and sodium iodates: acute toxicity in mice.
J. Pharmacol. Exp. Ther. 120:171-192.
Webster, S. H., M. E. Rice, B. Highman, and E. F. Stohlman. 1959. The
toxicology of potassium and sodium iodates. II. Subacute toxicity of
potassium iodate in mice and guinea pigs. Toxicol. Appl. Pharmacol.
1:87-96.
Webster, S. H., E. F. Stohlman, and B. Highman. 1966. The toxicology of
potassium and sodium iodates. III. Acute and subacute oral toxicology
of potassium iodate in dogs. Toxicol. Appl. Pharmacol. 8:185-192.
Wenlock, R. W., D. H. Buss, R. H. Moxon, and N. G. Bunton, 1982. Trace
nutrient. 4. Iodine in British food. Br. J. Nutr. 47:381-390.
Whitehead, D. C. 1984. The distribution and transformations of iodine in
the environment. Environ. Int. 10:321-339.
WHO (World Health Organization). 1988. Toxicological evaluation of cer-
tain food additives and contaminants, FAS 24: 267—294. Geneva: World
Health Organization.
WHO. 1998. Iodine. Environmental Health Criteria 200. Geneva: World
Health Organization.
Wilgus, H. F., F. X. Gassner, A. P. Patton, and G. S. Harshfield. 1953. The
iodine requirements of chickens. Ft. Collins: Colo. Agric. Exp. Stn.
Tech. Bull. 49.
Wolff, J. 1969. Iodide goiter and the pharmacological effects of excess
iodide. Am. J. Med. 47(1):101-124.
Copyright © National Academy of Sciences. All rights reserved.
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inemi Tnlemnce nf Animals- Sennnd Revised Edition
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MINERAL TOLERANCE OF ANIMALS
TABLE 15-2 Iodine Concentrations in Fluids and Tissues of Animals
Animal
Quantity
Source
Duration
Route
Milk Egg Yolk
(Mg/100 ml) (|jg/g)
Reference
Chickens
Control (0.5 mg I/kg)
+ 2.0 mg I/kg
+ 4.4 mg I/kg
+ 2.7 mg I/kg
+ 7.2 mg I/kg
Kelp
Kelp
Calj
Cal^
45 d
Diet
0.18
0.87
2.00
1.36
0.93
Rys'etaf, 1997
Control
5 d after
Diet
0.13
+ 10 mg I/kg live wt
KI
single dose
Diet
12.86
+ 10 mg I/kg live wt
Iodized oil
Diet
14.04
+ 10 mg I/kg live wt
Iodized oil
Intramuscular
injection
0.44
Control
21 d after
Diet
0.05
+ 10 mg I/kg live wt
KI
single dose
Diet
0.09
+ 10 mg I/kg live wt
Iodized oil
Diet
0.01
+ 1 mg I/kg live wt
Iodized oil
Intramuscular
injection
0.99
Cows, dairy
Control
+ 10 mg I/kg
+ 20 mg I/kg
+ 30 mg I/kg
+ 40 mg I/kg
KI
5 wk
Diet
1.8
15.7
23.6
30.1
36.2
Feng et al., 1999
Cows, dairy
Control (5.8 mg I/cow/d)
EDDI
42 d
Diet
20.6
Brzoska et at., 2000
Spring
+ 28.3 mg I/cow/d
+ 43.3 mg I/cow/d
+ 58.3 mg I/cow/d
^^H
Cows, dairy
Control (5.8 mg I/cow/d)
■
^^^^^^^^^H
Summer
+ 28.3 mg I/cow/d
+ 43.3 mg I/cow/d
+ 58.3 mg I/cow/d
EDDI
47 d
Diet
^^H
Cows, dairy
Control (5.8 mg I/cow/d)
^H
^^^^^^^^^H
Autumn
+ 28.3 mg I/cow/d
^H
^^^^^^^^^^^^^^1
+ 43.3 mg I/cow/d
EDDI
32 d
Diet
^H
^^^^^^^^^^^^^^1
+ 58.3 mg I/cow/d
239.2
^^^
Cows,
dairy
Control
+ 3.8 mg I/kg
+ 3.8 mg I/kg
+ 7.6 mg I/kg
+ 7.6 mg I/kg
+ 1 1.5 mg I/kg
+ 1 1.5 mg I/kg
KI
EDDI
KI
EDDI
KI
EDDI
Goats
20.5-162.4 |jg/kg
+ 3.05 ^ig I/kg
DM
Hay
Hay + iodized
salt
Sheep
20.5-162.4 |jg/kg
+ 3.05 Mg/kg
DM
Hay
Hay + mineral
lick
5d
Diet
Herzigetal., 2001
Diet
Diet
20 ± 5.2
50 ±15.2
80 ± 3.0
64 ±13.9
173 ±39.3
121 ±52.8
19.3
142.2
105.5
243.3
Travnicek and Kursa,
2001
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16
Iron
INTRODUCTION
The atomic symbol for iron is Fe, wliicti is derived from
the halin ferrum. Iron (atomic number, 26; atomic weight,
55.847) is a silvery, lustrous metal. There are 14 known iso-
topes of iron. Common iron consists of a mixture of four
isotopes.
The melting point of iron is 1,535°C, boiling point is
2,750°C, specific gravity is 7.874 (20°C), with a valence of
2, 3, 4, or 6. Pure iron is chemically reactive and corrodes
rapidly, especially in moist air or at elevated temperatures.
Four allotropic forms, or ferrites, are known: a, (3, y, and 5,
with transition points at 770, 928, and 1,530°C. The a form
is magnetic, but when iron is transformed into the p form,
the magnetism disappears, although the lattice remains un-
changed.
Iron is relatively abundant in the universe. It is found in
the sun and many types of stars in considerable quantity. The
core of the earth is thought to be largely composed of iron
with about 10 percent occluded hydrogen. On a weight ba-
sis, the metal makes up 5 percent of the Earth's crust and is
the fourth most abundant element. Pure iron is rarely en-
countered in commerce; it is usually alloyed with carbon or
other metals. Pig iron is an alloy containing about 3 percent
carbon with various amounts of sulfur, silicon, manganese,
and phosphorus. Iron is hard, brittle, and fairly fusible and is
used to produce other alloys, including steel. Wrought iron,
which contains only a few tenths of a percentage of carbon,
is tough, malleable, and less fusible. The pure metal is very
reactive chemically and rapidly corrodes, especially in moist
air or at elevated temperatures.
Iron is one of the most useful metals in both technology
and biology. Iron compounds are involved in numerous oxi-
dation-reduction reactions, beginning with the reduction of
hydrogen and its incorporation into carbohydrates during
photosynthesis in the presence of ferredoxins (Fairbanks,
1994). Iron is a vital constituent of plant and animal life and
works as an oxygen carrier in hemoglobin.
The ancient Greeks, Egyptians, and Hindus prescribed iron
as a treatment for general weakness, diarrhea, and constipa-
tion. The role of iron in blood formation became apparent in
the 17th century when it was shown that iron salts were of
value in treating chlorosis, now known as iron-deficiency ane-
mia, in young women. The first clinical description of iron
overload was reported in 1871 (Fairbanks, 1994).
ESSENTIALITY
Iron has been recognized as an essential nutrient for more
than 100 years when it was found to be present in all body
cells. The largest portion is found as a necessary component
of the protein molecules hemoglobin and myoglobin. The
major role of iron in both hemoglobin and myoglobin are
similar. Hemoglobin is found in red blood cells (erythro-
cytes) and transports oxygen from the lungs to the tissues,
whereas myoglobin binds oxygen for immediate use by
muscle cells (Morris, 1987).
Iron is also found in plasma (transferrin), milk
(lactoferrin), placenta (uteroferrin), and liver (ferritin and
hemosiderin) (Underwood, 1977; Underwood and Suttle,
1999). Species differences in total body iron concentrations
occur in the newborn, but become much less pronounced in
the adult. For example, the pig has relatively little iron in its
body at birth (29 mg/kg) because it is born with low liver
iron stores and has no polycythemia (venous hematocrit of
greater than 65 percent) of the newborn as does the human
infant. The newborn rabbit, by contrast, has an exceptionally
high total body iron concentration (135 mg/kg) because of
its high liver stores (Underwood, 1977). The iron concentra-
tion of skeletal muscle (on a fresh tissue basis) in adult dogs,
rabbits, hens, pigs, and cattle ranges from 12 to 16 mg/kg
(Georgievskii et al., 1979).
799
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MINERAL TOLERANCE OF ANIMALS
Iron plays an important role not only in oxygen delivery
to the tissues, but also as a cofactor with several enzymes
involved in energy metabolism and thermoregulation. Mito-
chondrial iron enzymes are essential for oxidative produc-
tion of cellular energy. Aerobic metabolism depends on iron
because of its role in the functional groups of most of the
enzymes of the Krebs cycle, as an electron carrier in cyto-
chromes, and as a means of oxygen and carbon dioxide trans-
port in hemoglobin (Fairbanks, 1994).
Iron deficiency is the most commonly known potential
mineral deficiency in humans (Baynes, 1994). It is estimated
that about half of the world's population suffers from iron
deficiency. Iron deficiency is of limited practical significance
in most livestock, but examples of situations in which animals
are vulnerable to iron deficiency are newborn pigs, calves
raised for veal, copper-supplemented pigs, and animals with
parasitic infestations (Underwood and Suttle, 1999). Iron is
required in growing, laying, and lactating animals at between
50 and 100 mg/kg, depending on age and species.
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
The most common methods currently used for the analy-
sis of iron in biological samples are flame AAS, graphite
furnace AAS, ICP-AES, ICP-MS, and x-ray fluorescence
spectroscopy. The method of choice for the analysis of iron
at very low concentrations is graphite furnace AAS, but
AAS and ICP-AES are acceptable for measuring usual or
toxic levels. Limits of detection for iron using AAS are on
the order of pg/mL (mg/kg) and for graphite furnace AAS
are generally in the low ng/mL (ppb) range. Sample prepara-
tion usually consists of wet ashing the specimen with strong
acid and heat, and redissolving the residue in dilute acid prior
to analysis so that all iron species are converted quantita-
tively to the same iron compound.
To ensure adequate quality control, a reference material
should be used that closely matches the matrix type and con-
centration of the experimental samples to be analyzed. Iron
contamination during sample collecting and processing must
be avoided. All glass equipment involved in blood collec-
tion and storage should be made of iron-free silicate glass
and acid washed. Because of the high levels of iron in the
atmosphere, samples can become contaminated during the
analytical process. It is essential, therefore, to complete all
analyses keeping the sample covered or in a hood. Blanks
should be included in all analyses.
REGULATION AND METABOLISM
Absorption
Gastrointestinal absorption of iron occurs primarily in the
duodenum, and the proportion of the dose that is absorbed
decreases as the dose increases. It is likely that iron absorp-
tion occurs by the divalent metal transporter- 1, which prima-
rily transports non-heme iron (Bressler et al., 2004). The rate-
limiting processes in iron absorption are associated with
transfer of iron from enterocytes to the blood rather than
transport across the apical membrane of the enterocytes.
Because of the limited capacity of the body to excrete iron,
iron homeostasis is maintained primarily by adjusting iron
absorption to bodily needs. The absorption of iron is affected
by (1) the age, iron status, and state of health of the animal;
(2) the conditions within the gastrointestinal tract; (3) the
amount and chemical form of the iron ingested; and (4) the
amounts and proportions of various other components of the
diet, both organic and inorganic (Underwood, 1977).
Soluble forms of iron are absorbed better than insoluble
forms (Skikne and Baynes, 1994). The proportion of a dose
of highly soluble iron absorbed by adults may vary from 2 to
20 percent when ingested (Layrisse and Martinez-Torres,
1971). Phytate, milk proteins, and soy proteins reduce iron
absorption. Young animals absorb iron more efficiently than
do older animals. Pregnancy, lactation, or a deficiency of
iron also increases the efficiency of absorption.
Metabolic Interactions
Once absorbed, iron enters the blood where it is taken up
by transferrin (Baker and Morgan, 1994). Iron in circulation
is primarily bound to transferrin. Transferrin distributes iron
throughout the body to wherever it is needed, mostly to
erythrocyte precursors in the bone marrow for new hemo-
globin synthesis. Cell membranes contain a protein called
transferrin receptor. On the cell membrane, diferric transfer-
rin binds to transferrin receptors, and then the iron-transfer-
rin-transferrin receptor complex is internalized by endocyto-
sis. The cellular regulation of iron is dependent on the effect
of iron, or iron lack, in stimulating the synthesis of ferritin or
of transferrin receptors, respectively (Fairbanks, 1994). This
regulatory mechanism involves the effect of iron on iron-
responsive elements (IRE) in the untranslated regions of
transferrin receptor mRNA and ferritin mRNA. An iron-re-
sponsive element binding protein (IRE-BP) appears to be
involved in the activation or repression of ferritin and also of
the transferrin receptor gene.
Much of the absorbed iron is transferred to the bone mar-
row where the iron-transferrin receptor complex enters eryth-
roblasts by endocytosis. Iron is released into the cytosol and
apotransferrin is returned to circulation. Within the cytosol,
iron either is transported to mitochondria to be incorporated
into heme or taken up by ferritin within siderosomes
(Fairbanks, 1994). Within the mitochondria, iron is inserted
into protoporphyrin, forming heme, a reaction catalyzed by
heme synthetase (ferrochelatase). Heme inhibits the release
of iron from transferrin, an important feedback mechanism
for adjusting the iron supply to the rate of hemoglobin syn-
thesis. Approximately 20 to 25 mg of iron is used daily for
hemoglobin synthesis in humans.
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IRON
201
In addition to the synthiesis of lieme, iron is also required
for tfie synthesis of iron-containing enzymes (Fairbanks,
1994). Examples of iron-containing enzymes are cytochrome
c, aconitase, cytochrome oxidase, phenylalanine hydroxy-
lase, and a-glycerophosphate dehydrogenase. These en-
zymes are sensitive to iron depletion; the degree of loss var-
ies from enzyme to enzyme and from tissue to tissue.
Cytochrome c and aconitase are readily depleted during iron
deficiency, as are the iron-sulfur enzymes in muscle mito-
chondria.
Iron in excess of need is stored intracellularly as ferritin
and hemosiderin, principally in the macrophage system of
the liver, spleen, and bone marrow (Fairbanks, 1994). Fer-
ritin is the basic storage form; hemosiderin appears to be
aggregated ferritin stripped of its protein component. Mobi-
lization of iron from iron stores requires the presence of the
Cu-containing enzyme of the plasma ceruloplasmin
(ferroxidase I) (Chung et al., 2004).
Daily excretion of iron is limited, and losses from the
body are relatively small except during hemorrhage or men-
struation. Although iron is released from breakdown of
erythrocytes and is secreted in bile, most of this iron is reab-
sorbed and used to form new hemoglobin. The primary
routes of iron excretion are via feces and urine, and there are
additional losses in sweat, hair, and nails (Georgievskii et
al., 1979; McDowell, 2003).
Mechanism of Toxicity
Organ damage arising from iron overload is remarkable
for the range of tissues affected and for the slow and insidi-
ous onset of organ dysfunction with chronic toxicity (Eaton
and Qian, 2002). The organs affected most by iron overload
are the liver, heart, and pancreatic beta cells; all are tissues
with highly active mitochondria, which generate activated
oxygen species capable of causing synergistic toxicity with
intracellular iron.
One hypothesis concerning the etiology of cell and organ
damage arising from iron overload is that excess iron selec-
tively targets mitochondria and, perhaps, the mitochondrial
genome (Eaton and Qian, 2002). The leak of electrons from
mitochondria accounts for about 90 percent of the activated
oxygen generated by most cells. Experimental acute iron
loading of cultured (beating) rat myocardial cells caused a
decrease in membrane polyunsaturated fatty acid (PUFA)
content, loss of thiol-dependent enzyme activities, decreased
ATP, and increased lysosomal fragility (Link et al., 1989).
Similar changes in mitochondrial energy production with
iron loading have been observed in the livers of rats with
chronic iron overload (Bacon et al., 1993). It is also known
that abnormal accumulation of iron within mitochondria is
associated with extensive and irreversible damage. Affected
mitochondria show not only iron accumulation but also in-
activation of iron-sulfur enzymes — complexes I, II, and III
and aconitase (Rotig et al., 1997). One of the pathological
consequences of iron overload might be damage to mito-
chondrial DNA (Eaton and Qian, 2002). There are several
reasons for the apparent fragility of mitochondrial DNA
(mtDNA): (1) mitochondria generate reactive oxygen spe-
cies; (2) mitochondria are intrinsically rich in iron; (3)
MtDNA is deficient in histones that may normally provide
partial protection against oxidant damage; and (4) repair of
damage to mtDNA is slow and less effective.
An alternative, but not mutually exclusive, mechanism
for the toxic effects of iron on cells and organs involves the
proposition that an accumulation of iron within the cellular
lysosomal compartment sensitizes the lysosomes to damage
and rupture, releasing damaging lysosomal digestive en-
zymes into the cytoplasm of the cell (Eaton and Qian, 2002).
Minimal release of lysosomal enzymes may induce transient
reparative autophagocytosis, while moderate lysosomal rup-
ture is followed by apoptosis. Severe oxidative stress, caus-
ing massive lysosomal breakdown, causes necrosis.
In summary, iron overload or toxicosis causes a number
of serious and life-threatening pathologies. The molecular
bases of these changes are not known, but pathologies in-
volving an interaction between iron and mitochondrial res-
piration seem to be at the core.
SOURCES AND BIOAVAILABILITY
Sources
The iron content of animal feeds is highly variable. The
level of iron in herbage plants is determined by the species
and type of soil in which the plants grow. Values as high as
700 to 800 mg/kg iron have been recorded for uncontami-
nated alfalfa and as low as 40 mg/kg for some grasses grown
on sandy soils (Underwood, 1977). Most cereal grains con-
tain 30 to 60 mg/kg, and species differences are small. The
leguminous and oil seeds may contain 100 to 200 mg/kg
iron.
Feeds containing animal products are rich sources of
iron. Meat meals and fish meals contain 400 to 600 mg/kg,
and blood meals contain more than 3,000 mg/kg iron.
Ground limestone, oyster shell, and many forms of calcium
phosphate used as mineral supplements contain 2,000 to
5,000 mg/kg iron (Underwood, 1977). Iron is commonly
added to animal diets in the form of iron sulfate, iron chlo-
ride, iron proteinates, and blood meal. Red iron oxide is
added to some pet foods and trace mineral supplements as
a coloring agent, but the iron in this source is essentially
unavailable to animals.
Water
The EPA has established National Primary Drinking
Water Regulations that set mandatory water quality stan-
dards for drinking water contaminants (EPA, 1992). These
are enforceable standards called "maximum contaminant
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MINERAL TOLERANCE OF ANIMALS
levels" (MCL), which are established to protect the public
against consumption of drinking water contaminants that
present a risk to human health. An MCL is the maximum
allowable amount of a contaminant in drinking water that is
delivered to the consumer. The MCL set for iron is 0.3 mg/
L. Excessive amounts of iron in water cause a rusty color,
sediment, metallic taste, and reddish or orange staining of
containers and cooking utensils. Iron is not generally listed
in tables with safe upper limits of concentrations of minerals
in water for livestock and poultry (NRC, 1974). Iron content
of surface waters in the United States ranges from 0.10 to
4,600 Mg/L with a mean of 43.9 pg/L (NRC, 1974). Well
water with high iron content may cause bacteria to prolifer-
ate, forming a red, slimy mass.
Bioavailability
Henry and Miller (1995) published a comprehensive re-
port on the bioavailability of iron in a wide variety of
feedstuff s and feed supplements. The proportion of dietary
iron absorbed is largely determined by the iron requirement
of the individual or animal. Absorption is regulated by the
body iron stores; the percentage absorbed is inversely pro-
portional to serum ferritin concentrations (Bothwell et al.,
1979). Iron bioavailability is also influenced by the compo-
sition of the diet.
A variety of factors in feeds can have an enhancing or
inhibiting effect on iron bioavailability. Ascorbic acid
strongly enhances the absorption of non-heme iron. In the
presence of ascorbic acid, dietary ferric iron is reduced to
ferrous iron, which forms a soluble iron-ascorbic acid com-
plex in the stomach. Animal tissues enhance the uptake of
non-heme iron. It is thought that low molecular weight pep-
tides released during digestion bind iron and improve its
bioavailability.
Inhibitors of non-heme iron absorption include phytate,
polyphenols, and calcium. Phytic acid (inositol
hexaphosphate) is present in legumes, rice, and grains. There
appears to be a dose-response relationship between the level
of phytate in a food and iron absorption (Hallberg and
Hulthen, 2000). Because phytate and iron are concentrated
in the aleurone layer and germ of grains, milling to white
flour and white rice reduces the content of phytate and iron,
thereby increasing the bioavailability of the remaining iron
(Larsson et al., 1996). Polyphenols markedly inhibit the ab-
sorption of non-heme iron. Iron binds to tannic acid in the
intestinal lumen forming an insoluble complex that reduces
absorption. The inhibitory effects of tannic acid are dose
dependent and reduced by the addition of ascorbic acid
(lOM, 2000). Calcium appears to inhibit the absorption of
both heme and non-heme iron (Gleerup et al., 1995). The
mechanism is not fully understood, but it may involve inter-
ference with the degradation of phytic acid and/or inhibition
of iron absorption during the transfer through the mucosal
cell.
Trace mineral interactions may also alter iron
bioavailability. An excess of one trace mineral may impair
the absorption or transportation of another mineral with simi-
lar divalent form, possibly by competing for intestinal bind-
ing sites on the mucosa; conversely, a deficiency of one min-
eral may be associated with an enhanced absorption of
another (Hill and Matrone, 1970). Interactions affecting iron
transport that have been described in animals include zinc-
copper-iron, calcium-phosphorus-iron, manganese-iron, co-
balt-iron, nickel-iron, and iron-cadmium. For example.
Baker andHalpin (1991) reported that when young chickens
are fed excessive dietary concentrations of manganese, the
blood hemoglobin concentrations decrease.
Additional examples of interactions that affect
bioavailability of iron for animals, along with a discussion
of the effects of feed processing, are provided in the review
by Henry and Miller (1995).
TOXICOSIS
Iron toxicosis is not a common problem in most domestic
animals, probably because of the limited absorption and up-
take of iron when intakes are high. Nevertheless, if intakes
are sufficiently high, signs of iron toxicosis occur. When
animals consume large amounts of iron over sustained peri-
ods, tissue overload occurs, iron binding capacity is ex-
ceeded, and reactive (free) iron levels become sufficient to
cause peroxidative damage, especially in liver. According to
Underwood and Suttle (1999), the underlying pathogenic
mechanism is peroxidative damage of lipid membranes and
therefore the extent of the damage will depend to some ex-
tent on the antioxidant status of the animal. Rats, and prob-
ably other animals, become more susceptible to iron over-
load with age (Wu et al., 1990).
Single Dose
Very large doses of soluble iron sources can be fatal.
Accidental fatal toxicoses have occurred in children, and
there have been fatalities in adults due to suicides (Abdel-
Mageed and Oehme, 1990). The lethal dose in adults is 200
to 250 mg Fe/kg BW. Three to 10 grams of ferrous sulfate
are usually fatal in young children (Mullaney and Brown,
1988). Autopsy findings include periportal hepatic necrosis
and congestion along with necrosis of gastric and duodenal
mucosa. Iron toxicosis in most animals (dogs may be an ex-
ception) requires much higher iron levels along with high
intakes of cobalt, zinc, manganese, or copper (Abdel-
Mageed and Oehme, 1990). A few studies have examined
the effect of single doses of iron in animals (Table 16-1). In
piglets given 200 mg iron from ferric ammonium citrate
within six hours of birth, only 33 percent survived for 21
days. Lesions in piglets dosed with ferrous sulfate include
hydropericardium, hydrothorax, and coagulative necrosis of
skeletal muscle. Ferrous sulfate given at 200 mg/kg BW to
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IRON
203
rabbits caused death within a few hours of administration
(NRC, 1980). A lethal dose of iron (200 mg/kg as ferrous
sulfate) was administered into the duodenum of seven rab-
bits as heart rate, right atrial pressure, arterial pressure, car-
diac output, left ventricular pressure, right ventricular devel-
oped force, and arterial pH were monitored (Artman et al.,
1982). The acute lethal dose increased systemic vascular re-
sistance and depressed stroke volume, cardiac output, and
ventricular force. In these rabbits, acute iron toxicosis sig-
nificantly depressed myocardial contractility.
Single dose iron toxicity has also been studied in swine.
Eight pigs (mean weight 25 kg) were given 60 mg of iron as
either solid iron tablets or chewable multivitamins with iron
per kg body weight (Nordt et al., 1999). After 10 hours, gross
examination of the esophagus, liver, small and large intes-
tines, and stomach of all the animals was performed by a
surgical pathologist. All of the animals survived for the 10-
hour study. The group receiving the solid iron tablets had
severe esophageal inflammation and focal erosion, but no
significant changes were identified in the liver, small intes-
tine, or large intestine of either group.
A newly born pig has very low iron reserves, rapid
growth, limited iron intake from the sow's milk, and is gen-
erally raised in an environment (away from soil) where ex-
ogenous iron is not available; therefore, pigs are routinely
supplied with an oral or injectable dose of iron (usually dex-
trin, dextran, or gleptoferrin). In some cases, after a single
dose injection of iron in a newborn pig, toxicosis has oc-
curred. Death may result as quickly as 30 minutes to 6 hours
postinjection or even be delayed for 2 to 4 days. A toxic oral
single dose of iron from ferrous sulfate is approximately 600
mg/kg BW for 3- to 10-day-old pigs (Campbell, 1961). A
single injection of 200 mg/kg BW of iron dextran to new-
born pigs from sows fed adequate vitamin E will result in
normal hemoglobin concentrations and growth performance
(Hill et al., 1999). However, toxicosis signs were observed
when 100 mg/kg BW of iron dextran was injected into new-
born pigs from vitamin E deficient sows (Lannek et al.,
1962).
The severity of iron toxicosis in young pigs from oral
doses of 200 mg iron administered within 6 hours of birth
depended on the iron source given. Dosing with ferric am-
monium citrate resulted in 66 percent mortality by 21 days
of age (Cornelius and Harmon, 1976).
Within 8 hours of birth, five foals were given 16 mg/kg
BW of ferrous fumarate orally (Mullaney and Brown,
1988). Two of the five foals died 50 hours after dosing,
one died at 7 days, and the other two survived. Necropsies
showed that the foals had liver disease. The dose of iron
causing acute toxicosis in foals (about 16.5 mg/kg BW) is
strikingly low when compared with the dose rates of other
species. This may be related to the high serum iron and
percentage saturation of transferrin levels that foals have
at birth. Also, since iron absorption is elevated at birth, a
small amount of orally administered iron could be well
absorbed and exceed the iron binding capacity of serum
and result in free or unbound iron reaching tissues, espe-
cially the liver.
Iron toxicity is sometimes encountered in dogs and cats,
usually as the result of consumption of large amounts of
readily ionizable iron such as multivitamins, dietary min-
eral supplements, or human pregnancy supplements. Acute
doses from 200 to 600 mg of iron per kilogram of body
weight are fatal in dogs (Reissman and Coleman, 1955;
Bronson and Sisson, 1960; D' Arcy and Howard, 1962). For
cats, the LD^g (median lethal dose) for an acute dose of
ferrous sulfate has been estimated to be 500 mg/kg BW
(Hoppe et al., 1955).
A study using rat hepatocytes showed that glutathione
and vitamin E can be protective against the lipid peroxidation
associated with iron toxicity (Milchak and Bricker, 2002). In
piglets, iron toxicosis is often associated with vitamin E de-
ficiency (Lannek et al., 1962).
Acute
Rats injected intraperitoneally with iron dextran at doses
of 250, 500, or 1,000 mg/kg BW developed oxidative stress
and impaired spermatogenesis in the testes that was depen-
dent on the amount of iron given and its accumulation in the
tissue (Lucesoli et al., 1999), suggesting that the toxic ef-
fects of iron are dose dependent. Chicks (2-days old) force-
fed by oral gavage with either 1, 10, or 100 mg ferrous sul-
fate (0.2, 2, or 20 mg of iron) survived and showed no gross
lesions from the treatment (Wallner-Pendleton et al., 1986).
However, administration of 180, 240, or 300 mg ferrous sul-
fate (36, 48, or 60 mg of iron) by gavage caused 6.6, 16.1,
and 26.5 percent of 3-day-old chicks to die within 24 hours,
respectively, and 85 percent developed ulcerative hemor-
rhagic ventriculitis and friable livers (Pescatore and Harter-
Dennis, 1989). An LDjg of 357 mg ferrous sulfate for chicks
has been reported. In laboratory animals, the oral LD^q is
reported to be 300, 600, and 900 mg/kg BW in guinea pigs,
rabbits, and mice, respectively (Somers, 1947).
Brown trout were exposed for 96 hours to lethal concen-
trations of iron sulfate as commercial grade liquor and ana-
lytical grade iron sulfate to determine if gill tissues reflect
systemic toxicosis (Dalzell and Macfarlane, 1999). The 96-
hour LCjQ on brown trout of a commercial iron (III) sulfate
liquor was 28 mg total iron/L (0.05 mg soluble iron/L); the
96-hour LCjQ for analytical grade iron (III) sulfate was 47
mg total iron/L (0.24 mg soluble iron/L). Lethal and suble-
thal exposure to both grades of iron caused accumulation on
the gill, which appears to be the main target for iron toxicity.
Physical clogging of gills and gill damage was seen. Gill
tissue showed no evidence of iron uptake, and iron did not
accumulate in plasma of fish exposed to iron compared to
controls. Respiratory disruption due to physical clogging of
the gills is suggested as a possible mechanism for iron toxi-
cosis in fish.
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204
MINERAL TOLERANCE OF ANIMALS
In humans, acute toxicity resulting from overdose of me-
dicinal iron, especially in children, has been reported (lOM,
2000). Gastrointestinal irritation occurs with doses between
20 and 60 mg/kg BW.
Chronic
Characteristic signs of chronic iron toxicosis include re-
duced feed intake, growth rate, and efficiency of feed con-
version. Cao et al. (1996) fed day-old chicks diets supple-
mented with 400, 600, or 800 mg/kg added iron as either
ferrous sulfate or iron methionine. The basal diet contained
188 mg/kg of iron. Feed intake and weight gain were re-
duced at all supplemental levels, but the effects were most
evident at the 800 mg/kg level.
A moderately high iron intake coupled with removing
phytate from a corn-soy diet increased the susceptibility to
oxidative stress in weanling pigs (Porres et al., 1999). Two
levels of dietary iron were studied: 80 or 750 mg/kg diet as
ferrous sulfate. Liver, colon, and colon mucosal scrapings
were collected after feeding the diets for four months. Oxi-
dative stress, as measured by thiobarbituric acid reacting
substances (TEARS), was increased in the high iron group
as well as by adding phytase to the lower iron diet. The data
show that intrinsic phytate in corn and soy is protective
against lipid peroxidation in the colon in the presence of
moderately high levels of dietary iron. Signs of a phospho-
rus deficiency were noted in pigs fed 5,102, or 7,102 mg/kg
iron when phosphorus was present at 0.92 percent of the diet
(Furugouri, 1972).
Dose-response studies done in steers show that chronic
intakes of high amounts of iron (i.e., 400 or 1,600 mg/kg) as
ferrous sulfate reduced daily feed intake and average daily
gain; 1,600 mg/kg reduced plasma copper and increased
plasma inorganic phosphorus (Standish et al., 1969). Koong
et al. (1970) fed six levels of iron between 100 and 4,000 mg/
kg as iron citrate to calves weighing about 125 kg. Poor gains
and diarrhea occurred in the animals fed 4,000 mg/kg,
and they were changed to 2,000 mg/kg after 6 weeks. The
body weights and feed consumption data for calves re-
ceiving 1,000 mg/kg were not significantly different from
those receiving 100 mg/kg. There was a trend toward
poorer performance at all dietary iron levels of 500 mg/kg
or more.
Milk replacers containing 100,500, 1,000, 2,000, or 5,000
mg/kg iron were fed to 3-day-old calves for six weeks to
estimate the lowest amount of dietary iron (added as ferrous
sulfate) that would reduce calf performance (Jenkins and
Hidiroglou, 1987). Calves tolerated all iron treatments ex-
cept 5,000 mg/kg. At 5,000 mg/kg, calves showed reduced
weight gains, feed efficiency, and digestibility of DM and
protein. There were no other signs of iron toxicosis and no
gross abnormalities on postmortem examination. Marked
increases in spleen and liver iron occurred with 2,000 and
5,000 mg/kg treatments.
Lambs with an initial weight of 31 kg were fed diets
supplemented with iron (as ferric citrate) at either or 760
mg/kg for 76 days (Rosa et al., 1982). The experiment also
included supplemental levels of phosphorus and aluminum.
The supplemental iron reduced feed intake and weight gain.
An increased intake of phosphorus partially alleviated the
adverse effects of the excess iron. In a subsequent experi-
ment (Rosa et al., 1986), mature wethers (70.5 kg) were
supplemented with ferric citrate to provide either or 1,000
mg of iron per kilogram of diet. The high iron intake re-
duced weight gain, but this was partially counteracted by
supplemental zinc. The effect of supplemental iron on
growth and mineral utilization was studied in 24 lambs
weighing an average of 29 kg (Prabowo et al., 1988). Treat-
ments consisted of supplemental iron at 0, 300, 600, or
1,200 mg/kg diet as ferrous carbonate. Lambs were slaugh-
tered after ad libitum access to the diet for 98 to 121 days.
None of the levels of dietary iron affected lamb gain or
feed intake. However, most forms of ferrous carbonate are
low in iron bioavailability (Henry and Miller, 1995), and
this probably explains the high iron tolerance in this ex-
periment. Supplemental iron did increase iron concentra-
tions in liver, spleen, and bone. Serum and liver copper, as
well as copper transport proteins, were decreased by
supplemental iron; zinc and manganese status were not af-
fected; and only subtle changes were seen in plasma and
tissue phosphorus. Studies of iron toxicosis in adult sheep
show that the chronic dose is between 40 and 80 mg/kg
BW/day when iron is administered in the soluble form of
ferrous chloride (Rallis et al., 1989).
To determine the effect of supplemental iron on liver
function in adult ponies, four ponies were given 50 mg Fe/kg
BW/day for 8 weeks (Pearson and Andreasen, 2001). He-
patic and serum iron concentrations, percentage saturation
of transferrin, and serum ferritin concentrations were in-
creased compared with baseline values and controls, but
there were no adverse clinical signs or histological lesions in
the liver; liver iron levels returned to normal by 28 weeks.
The effect of increased iron intake on growth and lipid
peroxidation in juvenile catfish weighing 32 g was studied in
a group of fish fed a fishmeal-based diet containing either
663 or 6,354 mg/kg dry diet as ferrous sulfate for 5 weeks
(Baker et al., 1997). The higher iron diet suppressed growth,
although tissue iron levels were not altered and hematocrit
levels did not change. Lipid peroxidation of the liver and
heart increased with the higher dose, and hepatic levels of
vitamin E were depleted. These data show that vitamin E is
important in preventing damage caused by excessive dietary
iron in fish as well as other species.
Factors Influencing Toxicity
The dietary level at which iron becomes toxic is af-
fected by other dietary constituents and by the physiologi-
cal state of the animal (Underwood, 1977; Abdel-Mageed
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IRON
205
and Oehme, 1990). Animals can tolerate considerably
higher daily exposure levels of iron when it is consumed
in the diet than when it is delivered in the water or the
fasting state. Among dietary factors, calcium is important
in modulating iron toxicity (lOM, 2000); high calcium
intakes reduce iron toxicity. Dietary phytate can also
modulate iron toxicity. Pigs fed diets high in iron and low
in phytate were more susceptible to oxidative stress than
pigs fed high iron-high phytate diets (Porres et al., 1999).
High dietary intakes of cobalt, copper, zinc, and manga-
nese, and deficient intakes of nickel will depress iron ab-
sorption. Levels of iron intake that would produce signs
of toxicosis in the animal would clearly need to be much
higher under conditions of abnormally high intakes of one
or more of these interacting elements than when such in-
takes are low or normal.
Several antioxidant enzymes may play vital roles in the
impact of overload iron. Cytosolic superoxide dismutase pre-
vents the toxic effects of oxygen (Wisnicka et al., 1998) and
chronic iron toxicosis (Zhao et al., 1995). Oral vitamin E can
prevent a toxic reaction to oral iron (ferrous sulfate or fuma-
rate) or intramuscular injection of iron either as dextrin or
dextran (Tollerz, 1973). In addition, Dougherty et al. (1981)
reported that supplemental dietary vitamin E was essential
in preventing mortality in rats given intraperitoneal injec-
tions of iron. Vitamin E and glutathione status of the animal
also influence susceptibility to iron toxicity (Lannek et al.,
1962; Milchak and Bricker, 2002).
Once iron has been absorbed, methods to minimize
its toxic effects are based on chelation to reduce the body
burden. The chelating agents are desferrioxamine,
CaNaj-EDTA and DTPA (diethylene triamine penta-acetic
acid).
TISSUE LEVELS
Accumulation of iron in tissues is dependent upon the
dose, the length of exposure, mode of administration, com-
position of the diet, and physiology of the animal (Table 16-
2). When animals are exposed to excessive amounts of iron,
it is preferentially deposited in the liver, spleen, and bone
marrow (Underwood, 1977). With very high doses, iron may
be deposited in the heart and kidneys. The iron content of
milk varies with the species and stage of lactation and is
highly resistant to changes in the level of dietary iron
(Underwood, 1977). The average iron concentration in hu-
man, cow, and goat milk is very similar. A high proportion
of values fall between 0.3 and 0.6 |ig/mL, with a mean of
about 0.5 |Jg/mL. An average hen's egg contains close to 1
mg of iron, or approximately 20 mg/kg of the edible portion
(Underwood, 1977). A high proportion of this iron is present
in the yolk. The effect of changes in the chicken's diet on
egg iron is unknown. Increases in liver, kidney, spleen, and
bone iron of chicks were reported when diets contained from
400 to 800 mg/kg of supplemental iron (Cao et al., 1996). A
modest 25 percent increase in muscle iron occurred when
steers were fed 1,000 mg/kg iron compared to 100 mg/kg
(Standish et al., 1969). In sheep, a supplement of 760 mg/kg
of iron as ferric citrate increased iron concentrations in liver,
kidney, spleen, and muscle (Rosa et al., 1982). Similar ef-
fects were observed in a subsequent experiment. Muscle iron
levels did not change in sheep fed 40 or 80 mg Fe/kg BW
(Rallis et al., 1989).
MAXIMUM TOLERABLE LEVELS
The maximum tolerable level of iron is defined as the
dietary level that, when fed for a defined period of time, will
not impair accepted indices of animal health or performance.
Dietary iron from natural feed sources is more tolerable at
higher concentrations than iron from soluble compounds.
Maximum tolerable concentrations of dietary iron have been
set at 500 mg/kg for cattle, 500 mg/kg for sheep, 500 mg/kg
for poultry, and 3,000 mg/kg for swine. Aquatic animals and
fish appear to have damage to gills when iron concentrations
are above 0.1 mg/L. These tolerable concentrations were set
based on the animal having normal iron status, and fed a
source of iron that is highly digestible. Therefore, higher
dietary concentrations can probably be fed when iron is sup-
plied from sources with low bioavailability or if the animal
is in a deficient state.
HUMAN HEALTH
The Food and Nutrition Board of the Institute of Medi-
cine recently established an upper level for dietary intake of
iron by humans. The estimate was based on the gastrointes-
tinal effects of supplemental intakes of iron salts (lOM,
2000). The LOAEL was estimated to be 70 mg/day and the
uncertainty factor was 1.5 to permit extrapolation to a
NOAEL. The LOAEL of 70 mg/day divided by the 1.5 un-
certainty factor gives an upper level of 45 mg Fe/day.
FUTURE RESEARCH NEEDS
There are inadequate data to define accurately maximum
tolerable levels for iron from dietary or water sources for
most non-laboratory animals. Few studies have included in-
cremental dose levels adequate for determining thresholds
for toxicity. Although swine seem to be able to tolerate
higher iron concentrations than most other species, long-term
studies are needed to confirm this tolerance.
SUMMARY
Iron toxicosis occurs in animals given excessive supple-
ments to prevent deficiencies. Since iron absorption is tightly
regulated, most animals do not take up large amounts of iron
from their diet. Thus, the primary effect of high iron intakes
is gastrointestinal distress. Young animals absorb iron more
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206
MINERAL TOLERANCE OF ANIMALS
efficiently than older animals and have a lower tolerance.
Most research on iron toxicity has utilized iron sulfate, which
is highly available. Low levels of iron exposure cause subtle
changes in growth and feed efficiency. Higher levels of ex-
posure cause accumulation in the liver, spleen, and bone
marrow, the major sites for iron storage. Muscle, milk, and
eggs are not a major site of iron accumulation.
REFERENCES
Abdel-Mageed, A. B., and F. W. Oelime. 1990. A review of tlie biochemi-
cal roles, toxicity and interactions of zinc, copper and iron: III. Iron.
Vet. Hum. Toxicol. 32:324-328.
Artman, M., R. D. Olson, and R. C. Boerth. 1 982. Depression of myocardial
contractility in acute iron toxicity in rabbits. Toxicol. Appl. Pharmacol.
66:329-337.
Bacon, B. R., C. O'Neill, and R. S. Britton. 1993. Hepatic mitochondrial
energy production in rats with chronic iron overload. Gastroenterology
105:1134-1140.
Balcer, D. H., and K. M. Halpin. I99I. Manganese and iron interrelation-
ship in the chick. Poult. Sci. 70:146-151.
Baker, E., and E. H. Morgan. 1994. Iron transport. In Iron Metabolism in
Health and Disease, J. H. Brock, J. W. Halliday, M. J. Pippard, and L.
W. Powell, eds. London: W. B. Saunders Company.
Baker, R. T. M., P. Martin, and S. J. Davies. 1997. Ingestion of sub-lethal
levels of iron sulphate by African catfish affects growth and tissue lipid
peroxidation. Aquat. Toxicol. (Amst.) 40:51-61.
Bairaza, M .L., C. E. Coppock, K. N. Brooks, D. L. Wilks, R. G. Saunders,
and G. W. Latimer. 1991. Iron sulfate and feed pelleting to detoxify free
gossypol in cottonseed diets for dairy cattle. J. Dairy Sci. 74:3457-3467.
Baynes, R. D. 1994. Iron deficiency. Pp. 189-226 in Iron Metabolism in
Health and Disease, J. H. Brock, J. W. Halliday, M. J. Pippard, and
L. W. Powell, eds. London: W. B. Saunders Company.
Bothwell, T. H., and C. A. Finch. 1962. Iron Metabolism. Boston: Little and
Brown.
Bothwell, T. H., R. W. Charlton, J. D. Cook, and C. A. Finch. 1979. Iron
Metabolism in Man. Oxford: Blackwell Scientific Publications.
Bressler, J. P., L. Olivi, J. H. Cheong, Y. Kim, and D. Bannona. 2004.
Divalent metal transporter 1 in lead and cadmium transport. Ann. N. Y.
Acad. Sci. 1012:142-152.
Bronson, W., and T. Sisson. 1960. Studies on acute iron poisoning. Am. J.
Dis. Child. 99:18-26.
Campbell, E. A. 1961. Iron poisoning in the young pig. Aust. Vet. J. 37:78—83.
Cao, J., X. G. Luo, P. R. Heniy, C. B. Ammerman, R. C. Littell, and R. D.
Miles. 1996. Effect of dietary iron concentration, age, and length of iron
feeding on feed intake and tissue iron concentration of broiler chicks for
use as a bioassay of supplemental iron sources. J. Poult. Sci. 75:495-504.
Chase, C. R., D. K. Beede, H. H. Van Horn, J. K. Shearer, C. J. Wilcox, and
G. A. Donovan. 2000. Responses of lactating dairy cows to copper
source, supplementation rate, and dietary antagonist (Iron). J. Dairy Sci.
83:1845-1852.
Chung, J., D. J. Haile, and M. Wessling-Resnick. 2004. Copper-induced
ferroportin- 1 expression in j 774 macrophages is associated with in-
creased iron efflux. Proc. Nat. Acad. Sci. USA 101:2700-2705.
Cornelius, S. G., andB. G. Harmon. 1976. Sources of oral iron for neonatal
piglets. J. Anim. Sci. 42:1350 (Abstr.).
Dalzell, D. J. B., and N. A. A. Macfarlane. 1999. The toxicity of iron to
brown trout and effects on the gills: a comparison of two grades of iron
sulphate. J. Fish Biol. 55:301-315.
D'Arcy, P. F., and E. M. Howard. 1962. The acute toxicity of ferrous salts
administered to dogs by mouth. J. Pathol. Bacteriol. 83:65-72.
Dean, B. S., F. W. Oehme, E. P. Krenzelok, G. R. Griffith, and R. H. Hines.
1996. Iron complexation with oral deferoxamine in a swine model. Vet.
Hum. Toxicol. 38:96-98.
Dougherty, J. J., W. A. Croft, and W. G. Hoekstra. 1981. Effects of ferrous
chloride and iron dextran on lipid peroxidation in vivo in vitamin E and
selenium adequate and deficient rats. J. Nutr. 1 1 1:1784— 1796.
Eaton, J. W., and M. Qian. 2002. Molecular bases of cellular iron toxicity.
Free Radical Biol. Med. 32:833-840.
EPA (tJ.S. Environmental Protection Agency). 1992. Secondary drinking
water regulations: guidance for nuisance chemicals. Available at http://
www.epa.gov/safewater/consumer/2ndstandards.html. Accessed March
22, 2005.
Fairbanks, V. F. 1994. Iron in medicine and nutrition. Pp. 185-213 in Mod-
ern Nutrition in Health and Disease, M. E. Shils, J. A. Olson, and M.
Shike, eds. Philadelphia: Lea & Febiger.
Furugouri, K. 1972. Effect of elevated levels of dietary iron on iron stores in
liver, some blood constituents and phosphorus deficiency in young
swine. J. Anim. Sci. 34:573-577.
Georgievskii, V. I., B. N. Annenkov, and V. I. Samokhin. 1979. Mineral
Nutrition of Animals. London: Butterworths.
Gleerup, A., L. Rossander-Hulthen, E. Gramatkovski, and L. Hallberg.
1995. Iron absorption from the whole diet: comparison of the effect of
two different distributions of daily calcium intake. Am. J. Clin. Nutr.
61:97-104.
Hallberg, L., andL. Hulthen. 2000. Prediction of dietary iron absorption: an
algorithm for calculating absorption and bioavailability of dietary iron.
Am. L Clin. Nutr. 71:1147-1160.
Henry, P. R., and E. R. Miller. 1995. Iron bioavailability. Pp. 169-199 in
Bioavailability of Nutrients for Animals: Amino Acids, Minerals, and
Vitamins, C. B. Ammerman, D. H. Baker, and A. J. Lewis, eds. San
Diego: Academic Press.
Hill, C. H., and G. Matrone. 1970. Chemical parameters in the study of in
vivo and in vitro interactions of transition elements. Fed. Proc. 29: 1474—
1481.
Hill, G. M., J. E. Link, L. Meyer, and K. L. Fritsche. 1999. Effect of vitamin
E and selenium on iron utilization in neonatal pigs. J. Anim. Sci.
77:1762-1768.
Hoppe, J. O., G. M. A. Marcelli, andM. L. Tainter. 1955. Progress of medi-
cal science therapeutics: a review of the toxicity of iron compounds.
Am. J. Med. Sci. 230:558-571.
lOM (Institute of Medicine). 2000. Dietary Reference Intakes for Vitamin
A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Man-
ganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washing-
ton, D.C.: National Academy Press.
Jenkins, K. J., and M. Hidiroglou. 1987. Effect of excess iron in milk re-
placer on calf performance. J. Dairy Sci. 70:2349-2354.
Koong, L. J., M. B. Wise, and E. R. Barrick. 1970. Effect of elevated dietary
levels of iron on the performance and blood constituents of calves. J.
Anim. Sci. 31:422-427.
Lannek, N., P. Lindberg, and G. Tollerz. 1962. Lowered resistance to iron
in vitamin E-deficient piglets and mice. Nature 195:1006.
Larsson, M., L. Rossander-Hulthen, B. Sandstrom, and A. S. Sandberg.
1996. Improved zinc and iron absorption from breakfast meals con-
taining malted oats with reduced phytate content. Br. J. Nutr. 76:677—
688.
Layrisse, M., and C. Martinez-ToiTcs. 1971. Food iron absorption: iron
supplementation of food. Prog. Hematol. 7:137-160.
Link, G., A. Pinson, I. Kahane, and C. Hershko. 1989. Iron loading modi-
fies the fatty acid composition of cultured rat myocardial cells and lipo-
somal vesicles: effects of ascorbate and alpha-tocopherol on myocardial
lipid peroxidation. J. Lab. Clin. Med. 1 14:243-249.
Lucesoli, F., M. Caligiuri, M. F. Roberti, J. C. Perazzo, and C. G. Fraga.
1999. Dose-dependent increase of oxidative damage in the testes of rats
subjected to acute iron overload. Arch. Biochem. Biophys. 372:37^3.
McDowell, L. R. 2003. Minerals in Animal and Human Nutrition.
Amsterdam: Elsevier.
Milchak, L. M., and J. D. Bricker. 2002. The effects of glutathione and
vitamin E on iron toxicity in isolated rat hepatocytes. Toxicol. Lett.
(Amst.) 126:169-177.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
IRON
207
Morris, E. R. 1987. Iron. Pp. 79—142 in Trace Elements in Human and
Animal Nutrition, Vol. 1, W. Mertz, ed. New York: Academic Press.
MuUaney, T. P., and C. M. Brown. 1988. Iron toxicity in neonatal foals.
EquineVet. J. 20:119-124.
NRC (National Research Council). 1974. Nutrients and Toxic Substances
in Water for Livestock and Poultry. Washington, D.C.: National
Academy Press.
NRC. 1980. Mineral Tolerance of Domestic Animals. Washington, D.C.:
National Academy Press.
Nordt, S. P., S. R. Williams, C. Behling, P. Richter, A. S. Manoguerra, and
R. F. Clark. 1999. Comparisonof the toxicities of two iron formulations
in a swine model. Acad. Emerg. Med. 6:1 104— 1 108.
Pearson, E. G., and C. B. Andreasen. 2001. Effect of oral administration of
excessive iron in adult ponies. J. Am. Vet. Med. Assoc. 218:400^04.
Pescatore, A. J., and J. M. Harter-Dennis. 1989. Effects of fen'ous sulfate
consumption on the performance of broiler chicks. Poult. Sci. 68: 1063—
1067.
Porres, J. M., C. H. Stahl, W. H. Cheng, Y. Fu, K. R. Roneker, W. G. Pond,
and X. G. Lei. 1999. Dietary intrinsic phytate protects colon from lipid
peroxidation in pigs with a moderately high dietary iron intake. Proc.
Soc. Exp. Biol. Med. 221:80-86.
Prabowo, A., J. W. Spears, and L. Goode. 1988. Effects of dietary iron on
performance and mineral utilization in lambs fed a forage-based diet. J.
Anim. Sci. 66:2028-2033.
Rallis, T., A. G. Spais, A. Papasteriadis, A. Agiannidis, and S. Leondidis.
1989. Iron toxicity in sheep. J. Trace Elem. Electrolytes Health Dis.
3:131-137.
Reissman, K. R., and T. S. Coleman. 1955. Acute intestinal iron intoxica-
tion. 11. Metabolic, respiratory and circulatory effects of absorbed iron
salts. Blood 46:46-51.
Rosa, I. v., P. R. Henry, and C. B. Ammerman. 1982. Interrelationship of
dietary phosphorus, aluminum and iron on performance and tissue min-
eral composition in lambs. J. Anim. Sci. 55:1231—1240.
Rosa, 1. v., C. B. Ammerman, and P. R. Hem'y. 1986. Interrelationships of
dietary copper, zinc and iron on performance and tissue mineral con-
centration in sheep. Nutr. Rep. Int. 34:893-903.
Rotig, A., P. de Lonlay, D. Chretien, F. Foury, M. Koenig, D. Sidi, A.
Munnich, and P. Rustin. 1997. Aconitase and mitochondrial iron-
sulphur protein deficiency in Friedreich ataxia. Nature Genetics
17:215-217.
Skikne, B., and R. D. Baynes. 1994. Iron absorption. Pp. 151-188 in Iron
Metabolism in Health and Disease, J. H. Brock, J. W. Halliday, M. J.
Pippard, and L. W. Powell, eds. London: W. B. Saunders Company.
Somers, G. F. 1947. Relative oral toxicity of some therapeutic iron prepara-
tions. Br. Med. J. 2:201.
Standish, J. F., C. B. Ammerman, C. F. Simpson, F. C. Neal, and A. Z.
Palmer. 1969. Influence of graded levels of dietary iron, as ferrous sul-
fate, on performance and tissue mineral composition of steers. J. Anim.
Sci. 29:496-503.
Tollerz, G. 1973. Vitamin E, selenium (and some related compounds) and
tolerance towards iron in piglets. Acta Agric. Scand. Suppl. 19:184—191.
Underwood, E. J. 1977. Iron. Pp. 13-55 in Trace Elements in Human and
Animal Nutrition, E. J. Underwood, ed. New York: Academic Press.
Underwood, E. J., and N. F. Suttle. 1999. The Mineral Nutrition of Live-
stock, 3rd ed. New York: CABI.
van Ravenswaay, R. O., P. R. Henry, and C. B. Ammerman. 2001. Effects
of time and dietary iron on tissue iron concentration as an estimate of
relative bioavailability of supplemental iron sources for ruminants.
Anim. Feed Sci. Technol. 90:185-198.
Wallner-Pendleton, E., D. P. Froman, and O. Hedstrom. 1986. Identifica-
tion of ferrous sulfate toxicity in a commercial broiler flock. Avian Dis.
30:430^32.
Wisnicka, R., A. Ki'zepilko, J. Wawryn, Z. Ki'awiec, and T. Bilinski. 1998.
Protective role of superoxide dismutase in iron toxicity in yeast.
Biochem. Mol. Biol. Int. 44:635-641.
Wu, W. H., M. Meydani, S. N. Meydani, P. M. Burklund, J. B. Blumberry,
and H. N. Munro. 1990. Effect of dietary iron overload on lipid
peroxidation, prostaglandin synthesis and lymphocyte proliferation in
young and old rats. J. Nutr. 120:280-289.
Zhao, M., K. Matter, J. A. Laissue, and A. Zimmerman. 1995. Copper, zinc,
and manganese superoxide dismutase immunoreactivity in hepatic iron
overload disease. Hist. Histopath. 10:925-935.
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17
Lead
INTRODUCTION
The atomic symbol for lead is Pb, which is derived from
the Latin plumbum. Lead (atomic number, 82; atomic
weight, 207.19; specific gravity, 11.34) is a bluish to sil-
very-gray metal, although the pure metal is easily tarnished
by an oxide film to dull gray. Lead metal is soft, pliable,
and has no characteristic taste or smell. It has four naturally
occurring isotopes (208, 206, 207, and 204 in order of abun-
dance), but the isotopic ratios for various mineral sources
are sometimes substantially different. This property has
been used to carry out nonradioactive-tracer environmental
and metabolic studies.
Lead has four electrons in its valence shell, but only two
ionize readily. The usual oxidation state of lead in inorganic
compounds is therefore +2 rather than H-4. Lead sulfide, lead
oxides, and most other inorganic salts of lead are poorly
soluble in water. Exceptions are salts with nitrate, chlorate,
and chloride. Organic salts have variable solubility, with lead
oxalate being insoluble and acetate being highly soluble.
Lead in the Earth's crust is usually found in the sulfide
(PbS) form as galena ores, with smaller amounts in cerrusite
(PbCOj) and anglesite (PbSO^). Galena occurs mostly in
deposits associated with other minerals, particularly zinc.
Mixed lead and zinc ores account for about 70 percent of
total lead supplies from mining. In 2002, Australia was the
largest producer of lead, with 23 percent of the world's total,
followed by China, 21 percent; the United States, 15 per-
cent; Peru, 10 percent; and Mexico, 5 percent. About 97 per-
cent of the lead in the United States is produced in Alaska
and Missouri (Smith, 2002).
Production of lead-acid batteries is the dominant use of
lead, accounting for about 83 percent of reported lead con-
sumption in 2002 (Smith, 2002). Use of lead in ammunition
and as pigments for glass and ceramics continues to account
for much of the rest of consumption, although these uses are
declining as less toxic substitutes are being developed. Other
current commercial uses of lead metal include production of
brass and bronze alloys, solders, greases, caulkings, and
bearings. Lead sheets are used in building construction, stor-
age tanks, and medical radiation shielding. Organolead com-
pounds were historically used as fuel additives
(tetraethyllead and tetramethyllead), but they are not cur-
rently an important industrial product.
Lead is considered one of the most significant environ-
mental pollutants, and its use is highly regulated because of
its high level of toxicity (IPCS, 1989; ATSDR, 1999). Be-
cause of this, lead metabolism and toxicity have been in-
tensely studied in humans and these data are often useful in
prediction of toxicity to domestic animals. Lead has been
incriminated as one of the most common causes of acciden-
tal poisonings in agricultural, companion, and wild animals,
as well as humans; however, incidence of toxicosis has been
diminishing due to decreased use of lead-containing prod-
ucts (Prescott, 1983; Morgan, 1994; Burger, 1995;
Needleman, 2004). Lead poisoning is sometimes referred to
as plumbism.
ESSENTIALITY
Lead is not known to be an essential nutrient for animals
and does not participate in any known beneficial biochemi-
cal functions. However, in several studies, the addition of
lead to the diet of rats and pigs improved growth rates and
lipid metabolism ( Reichlmayr-Lais and Kirchgessner, 1981;
Kirchgessner et al., 1991; Manser, 1991) and improved egg
production in chickens (Mazliah et al., 1989).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
The most common methods currently used for the analy-
sis of lead in biological samples are flame atomic absorption
spectrometry (AAS), graphite furnace atomic absorption
spectrometry (GFAAS), anode stripping voltametry (ASV),
inductively coupled plasma-atomic emission spectroscopy
210
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LEAD
211
(ICP/AES), inductively coupled plasma mass spectrometry,
and x-ray fluorescence spectroscopy. GFAAS and ASV are
the methods of choice for the analysis of lead at very low
concentrations, but AAS and ICP/AES are adequate when
levels are in the toxic range. Limits of detection for lead
using AAS are on the order of |ig/mL (ppm) and for GFAAS
are generally in the low ng/mL (ppb) range (Flegal and
Smith, 1995). Sample preparation usually consists of wet
ashing the specimen with strong acid and heat, and redis-
solving the residue in dilute acid prior to analysis so that all
lead species are converted quantitatively to the same lead
compound. Closed vessel microwave digestion gives similar
results as wet ashing (McCarthy and Ellis, 1991).
The reference method for the determination of the abso-
lute amounts of lead is by isotope dilution mass spectrom-
etry (Grandjean and Olsen, 1984), but due to equipment costs
and required expertise, it is not widely used. Spectrophoto-
metric methods, using diphenylthiocarbazone as the colori-
metric reagent, were widely used in the past. They are less
sensitive but still useful for toxicity studies.
To ensure adequate quality control, a reference material
should be used that closely matches the matrix type and con-
centration of the experimental samples to be analyzed. Lead
contamination during sample collecting and processing must
be avoided. All glass equipment involved in blood collec-
tion and storage should be made of lead-free silicate glass
and acid washed.
REGULATION AND METABOLISM
Absorption and Metabolism
Gastrointestinal absorption of lead occurs primarily in the
duodenum, and the percentage of the dose that is absorbed
decreases as the dose increases. It is likely that lead absorption
occurs by inadvertent uptake through pathways of essential
nutrients such as the divalent metal transporter- 1, which trans-
ports non-heme iron (Bressler et al., 2004). The rate-limiting
processes in lead absorption are associated with transfer of
lead from enterocytes to the blood rather than transport across
the apical membrane of the enterocytes. The efficiency of lead
absorption is markedly influenced by the chemical form of the
lead, the level of other dietary constituents, and the age and
physiological state of the animal. Soluble forms of lead are
absorbed better than insoluble forms. The proportion of a dose
of highly soluble lead absorbed by adults may vary from less
than 10 percent when ingested with a meal to 60-80 percent
when ingested after a fast. Calcium and phosphate are particu-
larly effective in reducing lead absorption (Fullmer, 1991;
Varnai et al., 2001). Young animals absorb lead considerably
more efficiently than older animals. Pregnancy, lactation, or a
deficiency of iron or calcium also increases the efficiency of
lead absorption. The apparent absorption of lead in adult sheep
is 15 percent when included in the diet at 1,000 mg/kg (Pearl
etal., 1983).
Absorption of lead from inhalation of particulates and
dust is efficient, but dermal absorption of inorganic lead
through unabraded skin is considered to be minimal (<0.1
percent) (IPCS, 1995).
Once absorbed, lead enters the blood where >90 percent
is taken up by red blood cells (Cake et al., 1996). Most of the
lead in red blood cells is bound to hemoglobin within the cell
rather than the erythrocyte membrane. Lead in plasma binds
to albumin and y-globulins and complexes with low molecu-
lar weight sulfhydryl compounds. After entering peripheral
tissues, lead is predominantly bound to protein. High affin-
ity cytosolic lead binding proteins (PbBP) rich in aspartic
and glutamic acids have been identified in the cytosol of rat
kidney and brain (Fowler, 1998). These proteins possess dis-
sociation constants for lead of 10"^ M. Lead also binds to
metallothionein. Binding of lead to these proteins attenuates
lead-induced inhibition of several enzymes.
Over time lead redistributes from soft tissues to bone
where it forms highly stable complexes with phosphate, re-
placing calcium in hydroxyapatite. As a result, lead is incor-
porated into bone during the normal mineralization processes
that occur during bone growth and remodeling and is also
released to the blood during the process of bone resorption
(Silbergeld et al., 1993; O'Flaherty, 1998). Physiological
states (e.g., pregnancy, parturition, osteoporosis, infection,
or prolonged immobilization) that are associated with in-
creased bone resorption promote the release of lead and en-
try into blood and milk (ATSDR, 1999).
A mother with a high body lead burden can transfer lead
transplacentally to her developing fetus. In rats and humans,
there is no functional placental-fetal barrier to lead trans-
port. Maternal and fetal blood lead levels are nearly identi-
cal, so lead passes through the placenta unencumbered
(Goyer, 1990). In cynomolgus monkeys (Macaca
fascicularis), up to 40 percent of the maternal lead burden
that is transferred to the fetus is mobilized from maternal
skeleton (Franklin et al., 1997). The transport of lead through
the more complex epitheliochorial placenta of pigs is de-
layed and there appears to be protection against lead accu-
mulation in the fetal brain (Lu et al., 1997). Lead transferred
from the hen to the egg is found in the shell and the yolk, but
not the white (Mazliah et al., 1989). Lead can also be trans-
ferred to milk, and 90 percent is associated with casein
(Beach and Henning, 1988).
Lead that is incorporated into hair is a useful indicator of
toxic levels of exposure, though levels are affected by hair
color, texture, location on the body, and growth phase. Also,
external contamination is problematic because cleaning
methods that are sufficiently vigorous to remove superficial
lead also remove lead from the hair shaft (IPCS, 1995).
Metabolism of inorganic lead consists primarily of re-
versible ligand reactions, including the formation of com-
plexes and thiols with free amino acids and proteins.
Organolead compounds are actively metabolized in the liver
by oxidative dealkylation catalyzed by cytochrome P-450.
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MINERAL TOLERANCE OF ANIMALS
Tetraethyl and tetramethyl lead are oxidized to triettiyl and
trimetiiyl metabolites, respectively, and to inorganic lead.
Further biotransformation of these intermediate metabolites
is highly species-specific.
The half-life for lead in blood and other soft tissues of
adult humans is about 1 month, but it is much longer in the
various bone compartments. The lead content of blood
steadily declines after exposure is discontinued. Lead is ex-
creted in the urine following glomerular filtration in the kid-
neys and by the intestines, either by transmucosal losses or
through biliary clearance in the form of organolead conju-
gates. There is considerable species variability in the rela-
tive importance of urinary versus intestinal excretion routes.
Intestinal excretion appears to dominate in rats and sheep. In
dogs, renal excretion dominates at low levels of lead expo-
sure but the proportion of the lead excreted into the gut via
bile increases with increasing body burden (Klaassen and
Shoeman, 1974).
Mechanism of Toxicity
Proposed toxic mechanisms for lead include its ability
to interact with proteins and change their functions, inhibit
or mimic the action of calcium, replace zinc as a cofactor in
enzymes, and cause oxidative stress (Bressler and
Goldstein, 1991; Goering, 1993; Goldstein, 1993; Hsu and
Guo, 2002). Lead modifies the folding, binding character-
istics or enzymatic activity of proteins by binding to sulf-
hydryl, amine, phosphate, and carboxyl groups. Lead can
replace calcium in some reactions, such as formation of
hydroxyapatite. Lead can replace zinc in the catalytically
active site of enzymes, such as 5-aminolaevulinic acid de-
hydratase (Warren et al., 1998). It mimics calcium in the
activation of calmodulin and protein kinase C by binding
to amino acid carboxyl groups and sulfhydryl groups, re-
spectively. Lead-induced oxidative stress also contributes
to the pathogenesis of lead poisoning. The relative impor-
tance of these diverse disruptive actions depends upon the
cell type and organ system (Goyer, 1993).
SOURCES AND BIOAVAILABILITY
The primary sources of lead exposure to animals are con-
taminated soils; lead paints that remain on older structures;
water from plumbing systems that contain lead; and lead-
based products, especially batteries, used crankcase oil, and
linoleum (Waldner et al., 2002). Most plants do not take up
large amounts of lead from the soil and plant-based feed
ingredients are low in lead unless they are contaminated from
airborne sources or postharvest (Burrows, 1982). Meat and
fishmeals are low in lead unless they become contaminated
by exogenous sources. However, some mineral sources have
high levels of lead. For instance, samples of feed-grade cop-
per sulfate and complete mineral mixes had 640 and 460 mg/
kg, respectively (Bakalh et al., 1995a; Marcal et al., 2001).
The contribution of natural sources to lead concentrations
in the biosphere is small and anthropogenic sources dominate.
Releases to soil from nonferrous smelters, battery plants, and
chemical plants are currently the major anthropomorphic
sources of lead. In 1984, combustion of leaded gasoline was
responsible for approximately 90 percent of all anthropogenic
lead emissions. Use of lead additives in motor fuels was to-
tally banned after 1995, and use in paints and many other ap-
plications has also been prohibited. Yet lead is extremely per-
sistent in the environment and historical sources are still a
major contaminant. The chemical remnants from leaded fuels
now exist in soils primarily as inorganic lead oxides, carbon-
ates, oxycarbonates, sulfates, and oxysulfates. Lead has been
mined and purified throughout recorded history, and the
legacy of this activity is reflected in the high content of lead in
soils at many locations (Eckel et al., 2002). Agricultural use of
municipal sludge and other biosolids as fertilizers also con-
tributes lead to soils. Dusting and flaking of paint from older
structures is a source of lead contamination in surface dust
and soils. Many metropolitan areas have areas of very high
lead concentrations due to historical use of lead paints and
leaded fuels. Companion animals accumulate lead from soils
and dust to a much greater extent than humans living in the
same environment, and are particularly at risk to lead expo-
sure from the sanding and scraping of lead-based paints dur-
ing remodeling of older homes (Berny et al., 1994; Knight and
Kumar, 2003). Though most automobile batteries are recycled,
toxicosis occasionally occurs from animals ingesting those left
in pastures (Oskarsson et al., 1992). Lead used for balancing
wheels has also been implicated in toxicosis. A major source
of lead to waterfowl and other wildlife is spent lead shot, bul-
lets, cartridges, and the lead sinkers used in sport fishing
(Burger and Gochfeld, 2000; De Francisco et al., 2003). Birds
retain grit in their gizzard as a digestive aid and lead particles
can be retained in the acid environment of the gizzard for long
periods of time, increasing its toxicity. Bullets and other am-
munition contaminating target ranges have caused lead toxi-
cosis in cattle, and shooting ranges should not be used for
pasture.
Lead occurs naturally in the Earth's crust at a concentra-
tion of about 13 mg/kg, but there are some areas with much
higher concentrations, including the lead ore deposits scat-
tered throughout the world. The lead concentrations in igne-
ous, metamorphic, and sedimentary rocks are in the range of
10-20 mg/kg. The lead content of sandstones and carbon-
aceous shales from the United States and Europe ranges from
10 mg/kg to 70 mg/kg. Lead in phosphate rocks may exceed
100 mg/kg (IPCS, 1989; ATSDR, 1999). The concentration
of lead in the top layers of soil may be due to deposition and
accumulation of atmospheric particulates from anthropo-
genic sources. For example, soils directly beside major road-
ways where leaded gasoline was used for decades are typi-
cally 30-2,000 mg/kg higher than natural levels, but drop
exponentially up to 25 meters from the roadway (IPCS,
1989; ATSDR, 1999).
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The concentration of lead in surface water is liiglily vari-
able depending upon sources of pollution; lead content of
sediments; and the pH, salinity, and organic matter content
of the water. Surface waters in the United States average
3.9 l-ig/L and are higher in urban areas than in rural areas
(ATSDR, 1999). Lead is estimated to be present in seawa-
ter at approximately 0.005 |-ig/L. In seawater and most sur-
face and ground waters, the concentration of dissolved lead
is kept low because lead forms carbonates, sulfates, and
phosphates that have low water solubilities and precipitate
out of the water column. Much of the remaining ionic lead
absorbs to organic matter and is removed by appropriate
water purification.
Biomagnification of lead in the environment does not
typically occur. In general, the highest lead concentrations
are found in aquatic and terrestrial organisms that live near
lead-contaminated sites. In aquatic organisms, lead concen-
trations are usually highest in benthic organisms and algae,
and lowest in upper trophic level predators such as carnivo-
rous fish. Older organisms tend to contain the greatest body
burdens of lead.
The bioavailability of lead in soil to plants is highest in
acidic soils that have low organic matter content. Transloca-
tion of lead ions in plants is limited, and most lead is found
in the cell walls of root cells. The total concentration of lead
in soil does not correlate well with the concentration in the
plant unless the soil content is expressed as extractable lead.
Foliar uptake of lead occurs to a very limited extent. No
specific category of food is especially high in lead content,
and levels in raw edible plants are usually below 0.05 mg/kg
wet weight. In a recent study, levels of lead in grain were not
correlated to soil content and surface contamination intro-
duced during grain harvest or storage was the primary source
of lead in feeds using these feedstuffs (Zhao et al., 2004).
Cattle grazing near lead smelters have elevated blood lead
levels and the mean levels decrease with distance. However,
ingestion of soil along with roots is thought to be the primary
source of lead (Neuman and Dollhopf, 1992). There is some
indication that dairy cattle can detect lead on pasture grasses
and that they prefer to graze pastures without lead (Strojan
and Phillips, 2002).
Silage can be an important contributor of lead. In one
report, alfalfa, estimated to contain 25.89 mg Pb/kg dry
matter due to contamination of contaminating soil, was
ensiled for 3 weeks in a glass-lined silo and the haylage from
the bottom of the silo contained 1 18.6 mg of Pb/kg. Appar-
ently, lead migrated and concentrated in the bottom of the
silo (Coppock et al., 1988).
Bioavailability
The bioavailability of lead is markedly influenced by its
form and especially by its solubility. The efficiency of lead
absorption is directly related to its solubility in the gas-
trointestinal tract. Unfortunately, most toxicity studies use
lead acetate, which is one of the most soluble forms of lead
and does not mimic the bioavailability of lead oxide, sulfide,
sulfate, carbonate, or phosphate found in contaminated soils
and waters. The bioavailability of lead sulfide is only about
10 percent that of lead acetate and lead oxide is intermediate
in bioavailability (Dieter et al., 1993; Freeman et al., 1996).
In growing rats, the bioavailability relative to lead acetate of
lead in soil from mining wastes mixed with feed is typically
10 percent or less (Freeman et al., 1992; Dieter et al., 1993;
Freeman et al., 1994; Polak et al., 1996). The bioavailability
of lead in contaminated soil to growing pigs was found to be
58 to 74 percent of lead acetate, depending on the tissue
examined (Casteel et al., 1997). However, the soil was dosed
2 hours before a meal and was not incorporated into food,
and the absorption of lead from soil was greatly depressed
by food consumption (Maddaloni et al., 1998). The
bioavailability of lead in sewage and harbor sludges to lambs
is only about half that of lead acetate (Van Der Veen and
Vreman, 1986). The bioavailability of metallic lead is only
about 1 5 percent of lead acetate, and particle size is inversely
related to lead absorption (Barltrop and Meek, 1975, 1979).
The bioavailability of lead in animal tissues is less than
that in lead acetate. For example, lead intrinsically incorpo-
rated into the soft tissues of oysters has a relative
bioavailability of 72 percent (Stone et al., 1981). Lead in
milk is highly available (Hallen and Oskarsson, 1995).
TOXICOSIS
Lead intoxication in humans has been documented since
the second century B.C. and much of our understanding of
lead toxicity comes from studies in humans and other pri-
mates. While not as extensive, studies with companion ani-
mals, poultry, and livestock have demonstrated similar health
effects of lead as those observed in humans (Table 17-1).
Cardiovascular, hematological, and neurodevelopmental
signs of lead occur at the lowest levels of exposure, and re-
nal, gastrointestinal, hepatic, and immunological signs oc-
cur with higher doses or lengths of exposures. The toxicity
of lead does not appear to be dependent on the route of expo-
sure and is readily predicted by blood lead levels (IPCS,
1995; ATSDR, 1999). Correlation and regression analyses
of blood lead levels versus the incidence of various clinical
endpoints indicate that toxic symptoms in humans begin
when blood lead levels reach 10-15 |-ig/dL. These include
effects on heme metabolism, erythrocyte pyrimidine nucle-
otide metabolism, serum vitamin D levels, mental and physi-
cal development, and blood pressure. Anemia, nephrotoxic-
ity, and more overt neurological impairment occur when
blood lead levels exceed 30 |Jg/dL.
Hematological Changes
Lead inhibits the activities of 5-aminolevulinic acid de-
hydratase and ferrochelatase enzymes and, consequently.
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MINERAL TOLERANCE OF ANIMALS
heme biosynthesis. Heme is a feedback inhibitor of 5-
aminolevulinic acid synthetase activity, so lead toxicity
causes an increase in plasma and urinary 5-aminolevulinic
acid. Lead inhibition of ferrochelatase results in an accumu-
lation of zinc protoporphyrin in circulating erythrocytes be-
cause of the placement of zinc, rather than iron, in the por-
phyrin moiety. Decreased hemoglobin production, coupled
with an increase in erythrocyte destruction, results in a hy-
pochromic, normocytic anemia with associated reticulocy-
tosis (Lubran, 1980; Scheuhammer, 1987b).
Cardiovascular Effects
Lead toxicosis often causes hypertension in humans and
other animals. Additional signs include myocarditis, electro-
cardiographic disturbances, heightened catecholamine
arrhythmogenicity, altered myocardial contractile respon-
siveness to inotropic stimulation, hypercholesterolemia, ath-
erosclerosis, degenerative structural and biochemical
changes affecting the musculature of the heart and vascula-
ture, and increased vascular reactivity to alpha-adrenergic
agonists (Kopp et al., 1988). Several mechanisms for these
multifactorial actions appear to be involved. Lead causes
increased intracellular concentrations of calcium in capillar-
ies and arteries, triggering smooth muscle contraction and
increased vascular smooth muscle tone. Lead also causes
oxidation and inactivation of nitric oxide, increasing vascu-
lar constriction. These direct effects are augmented by in-
creased sympathetic activity and circulating noradrenaline
and angiotensin-converting enzyme activity (Vaziri, 2002).
Neurological and Neurodevelopmental Effects
Lead impairs neurological functions at virtually all stages
of the life cycle (Regan, 1989; Winneke et al., 1996). At low
levels, lead has subtle effects on learning and IQ. Higher lev-
els of exposure cause blindness and encephalopathy, which
manifests as dullness, irritability, poor attention span, head-
ache, muscular tremor, loss of memory, and hallucinations.
Lead blocks voltage-regulated calcium channels, inhibiting the
influx of calcium that triggers the release of neurotransmitters
(Gill et al., 2003). Thus, lead inhibits the propagation of nerve
transmission that follows the depolarization of presynaptic
nerve terminals. Lead also enters the cell by the same chan-
nels as calcium and acts as a calcium agonist to increase the
spontaneous release of neurotransmitters. Lead-induced syn-
aptic noise during critical early periods of postnatal develop-
ment may permanently disrupt the synaptic organization and
functional processing of neurons (Johnston and Goldstein,
1998; Bressler et al., 1999; Marchetti, 2003).
Hydrocephalus may also occur during lead toxicosis, es-
pecially in younger animals and children. Lead affects the
differentiation of brain endothelial cells and influences its
vasculature. The resulting disruption of the blood-brain bar-
rier allows albumin, ions, and consequently water to freely
enter the brain. Because the brain lacks a well-developed
lymphatic system, clearance of plasma constituents is slow,
edema occurs, and intracranial pressure rises (Bressler and
Goldstein, 1991). Increased capillary permeability allows
more lead to enter the brain. Fetal astrocytes and neurons
lack the ability to form detoxifying lead-protein complexes
and are especially susceptible. Consequently, lead causes
reductions or delays in the development of the hippocampus
and cerebral cortex, and reductions in the number and size of
axons in the optic nerve (Goyer, 1990).
The effects of lead are not limited to the central nervous
system. Demyelination of peripheral nerves and decreased
nerve conduction velocities cause impaired motor skills due
to lead toxicosis (Araki et al., 2000). Poor coordination and
erratic movements are among the first obvious clinical signs
noticed in farm and companion animals.
Gastrointestinal Effects
Colic is a consistent early symptom of lead poisoning in
individuals acutely exposed to high levels of lead. Colic is
characterized by a combination of abdominal pain, constipa-
tion, cramps, nausea, vomiting, anorexia, and weight loss
(Pagliuca et al., 1990).
Renal Effects
Impairment in kidney function occurs acutely when the
lead dose is high or after chronic exposure to lower levels
(Loghman-Adham, 1997; ATSDR, 1999; Brewster and
Perazella, 2004). The characteristics of early or acute lead-
induced nephropathy include nuclear and mitochondrial in-
clusion bodies and cytomegaly of the proximal tubular epi-
thelial cells. Dysfunction of the proximal tubules is manifest
as aminoaciduria, glucosuria, and phosphaturia with hypo-
phosphatemia. These effects appear to be reversible. Chronic
lead nephropathy progresses to interstitial fibrosis, dilation
of tubules and atrophy or hyperplasia of the tubular epithe-
lial cells forming microcysts, reduction in glomerular filtra-
tion rate, and azotemia. These changes are not readily re-
versed upon lead withdrawal. Lead's inhibition of renal
cytochrome P-450 system interferes with the activation of
25-hydroxyvitamin to 1,25-dihydroxyvitamin D and second-
ary disruption in calcium homeostasis (Smith et al., 1981;
ATSDR, 1999).
Inclusion bodies are lead-protein complexes composed
of acidic non-histone proteins and are diagnostic of lead toxi-
cosis. As much as 90 percent of lead in the kidney is con-
tained in the inclusion bodies, suggesting that they provide a
detoxification function.
Immunological Effects
Lead exposure at low to moderate levels does not pro-
duce widespread changes in the numbers of leukocytes but
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LEAD
215
does have important functional impacts on regulatory cells,
including macrophages and T lymphocytes. Lead causes a
pronounced shift in the balance in T helper cell function to-
ward T helper 2 responses at the expense of T helper 1 func-
tions. This bias alters the type of effector responses triggered
by vaccinations, allergens, and infectious organisms and in-
fluences the host's susceptibility to various diseases (Dietert
et al., 2004). In poults, lead disrupts eicosanoid metabolism
of macrophages and influences their regulatory functions
(Knowles and Donaldson, 1997).
Reproduction
Lead adversely affects both male and female reproduc-
tive functions. Decreased fertility and increased incidence of
abortions and stillbirths occur in females (IPCS, 1995;
ATSDR, 1999; Sallmen, 2001). In males, lead causes
asthenospermia, hypospermia, and teratospermia. Reproduc-
tive effects of lead toxicosis range from indirect effects of
lead on nutrition or hormonal status to more direct effects on
chromatin stability and epigenetic changes. However, lead
does not appear to be a major cause of congenital anomalies.
Bone
Lead impairs normal bone growth and remodeling as in-
dicated by decreased bone density and bone calcium con-
tent, decreased trabecular bone volume, and altered growth
plate morphology. Lead may affect bone indirectly by de-
creasing the activation of 1,25-dihydroxy vitamin D and dis-
rupting calcium homeostasis (Pounds et al., 1991; Silbergeld
et al., 1993). The appearance of lead inclusion bodies in os-
teoclasts is one of the most sensitive histological changes
that occurs in subclinical lead toxicosis of dogs (Hamir et
al., 1988).
Cancer
Data in laboratory animals indicate that lead acetate and
lead phosphate at very high doses are carcinogenic, and that
the most common tumor in rats is renal. The relevance of
this observation to human cancer is controversial, but the
U.S. Environmental Protection Agency has designated lead
as a probable human carcinogen (EPA, 1999).
Toxicity to Aquatic Organisms
Lead toxicosis in fish is very common. Clinical signs in-
clude muscular atrophy, lordoscoliosis, paralysis, black tails,
degeneration of the caudal fins, hyperactivity, loss of equi-
librium, erratic behavior, decreased growth, and death. In
many species, black tails are the first noticeable signs of high
levels of lead in the water. Juvenile fish generally are more
sensitive to lead toxicosis than adults. Organic compounds
are usually more toxic to fish than inorganic lead salts. Dis-
ruptions in ion regulations, especially calcium, sodium, and
chloride, appear to be a primary mechanism of the toxic ef-
fects of lead (Rogers et al., 2003). Lead toxicity to fish and
other aquatic animals has been extensively reviewed (Eisler,
1988; IPCS, 1989; Sorenson, 1991).
Single Dose
Very large doses of soluble lead sources can cause severe
intestinal pain and death due to encephalopathy in humans
(ATSDR, 1999). Most studies examining the effect of single
doses of lead on farm animals were published prior to 1980
and were reviewed in the previous version of this report
(NRC, 1980). Goats drenched with 400 mg/kg BW as lead
acetate died after 23 days and 50 mg/kg BW resulted in abor-
tion. Ponies drenched with 1 g lead/kg BW as lead acetate
were highly anorexic and lost considerable body weight
(DoUahite etal., 1975). A single dose of lead acetate to calves
at 200-400 mg Pb/kg BW is fatal. In adult cattle, 600-800
mg Pb/kg BW is fatal (NRC, 1980). When given in the diet,
1 g lead acetate/kg BW is fatal to sheep (Blaxter, 1950). Pigs
and chickens appear to be more resistant to single dose or
acute toxicosis of lead (NRC, 1980).
Acute
In humans, early neurological symptoms of acute lead
poisoning include dullness, irritability, fatigue, decreased li-
bido, dizziness, and confusion. The condition may then
worsen, sometimes abruptly, to delirium, convulsions, pa-
ralysis, coma, and death. Overt signs and symptoms of neu-
rotoxicity occur when blood lead levels reach 40-60 |Jg/dL
(IPCS, 1995; ATSDR, 1999).
Acute exposure of animals to lead most frequently occurs
from contamination of the feed; licking and chewing batter-
ies; or consuming lead paint, lead shot, or lead sinkers. Year-
ling dairy heifers that consumed lead-contaminated silage de-
veloped blindness, tachypnea, foaming at the mouth, chewing,
and facial fasciculations (Galey et al., 1990). Dogs with acute
lead poisoning developed anorexia, salivation, vomiting, and
diarrhea accompanied by spasmodic colic (Prescott, 1983).
Death in dogs from acute exposure occurs at doses of 191,
1,300, and 1,366 mg Pb/kg BW for lead acetate, oxide, and
sulfate, respectively (ATSDR, 1999). Chickens fed 200 mg/
kg BW Pb/day from lead acetate develop anorexia, diarrhea,
watery discharge from the mouth, muscular weakness, brown-
ish-black discoloration of the comb, difficult respiration, and
convulsions. Consumption of this level of lead results in death
starting at about day 10 (Brar et al., 1997).
Lead shot or sinkers ingested by birds and other animals
can be fatal. Depending on the amount of shot ingested, clini-
cal signs develop within a few days and death may occur
after a few weeks. In ducks, clinical signs include abnormal
behavior, intense green diarrhea, anorexia, weakness, inabil-
ity to fly, and eventually paralysis (De Francisco et al., 2003).
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MINERAL TOLERANCE OF ANIMALS
The toxicity of lead-contaminated water to fish varies
considerably, depending on water hardness, pH, salinity, and
organic matter. Young stages offish are more susceptible to
lead than adults or eggs. Rainbow trout are among the most
sensitive species, and death occurs (LC^q) at 1.0 mg Pb/L
from lead nitrate when the water hardness is 140 mg CaCOj/L
(Rogers et al., 2003). The LC^q value for tilapia was found to
be 202 mg Pb/L using lead nitrate. At lower levels of expo-
sure, the lability of lysosomal membranes in the gill was
found to be a more sensitive indicator of toxicosis than de-
creases in blood hemoglobin and occurred at levels above
47 mg/L (Tabche et al., 1990).
Chronic
Subtle changes in hematological, neurological, and bio-
chemical indices in rats, monkeys, and humans chronically
exposed to lead occur at around 0.005 to 0.01 mg Pb/kg BW/
day, and functional changes become apparent at around 1
mg/kg BW/day (ATSDR, 1999). For example, in a 9-year
study with monkeys, evidence of functional changes in tem-
poral visual function occurred at 2 mg Pb/kg BW/day (Rice,
1998). In most studies, lead was administered by gavage or
in the water. Considerably higher levels are needed to obtain
similar results when lead is provided in the feed. In a 2-year
feeding study with rats, lead did not have detrimental hema-
tological effects at 10 mg/kg diet, but caused significant in-
hibition of aminolevulinic acid dehydratase (ALAD) at 50
mg/kg. In this study, changes in enzyme activity did not
translate into changes in hemoglobin concentration, hemat-
ocrit, or renal function at 500 mg/kg, but did at 1,000 mg/kg
(Azar et al., 1973). Regardless of the route of delivery, im-
paired learning and memory is the most sensitive indicator
of lead toxicosis and occurs at blood lead levels of about 150
|jg/L in rats and primates (IPCS, 1995).
In a 2-year feeding study with dogs, 50 mg/kg diet of lead
was tolerated without hematological changes. There was a
significant inhibition of ALAD at 100 and 500 mg/kg, but
hematocrit was normal (Azar et al., 1973). Histological le-
sions in the central nervous system were observed in dogs
gavaged a mixture of lead salts at 5 mg Pb/kg BW/day
(Hamir et al., 1984), but were not observed in dogs given
slightly lower levels (Steiss et al., 1985).
Laying hens tolerate 25 mg Pb/kg diet from lead acetate,
but 50 mg/kg results in decreased egg production accom-
panied by feather molt (Edens and Garlich, 1983). Grow-
ing quail tolerate 100 mg/kg diet of lead from lead acetate
with only changes in plasma calcium levels, whereas 1,000
mg/kg diet results in decreased growth rate. Exposure of
quail from hatching through reproduction resulted in de-
creased egg production at dietary lead levels of 10 mg/kg
(Edens and Garlich, 1983). In one study, adding 1 mg Pb/
kg diet as lead acetate or lead sulfate significantly de-
creased the growth rate of broiler chickens without signifi-
cantly influencing the concentration of lead in the liver.
kidney, or muscle (Bakalli et al., 1995a). The background
level of lead in the control diet was 2.6 mg/kg so the total
lead content was estimated to be 3.6 mg/kg. When dietary
calcium levels were increased, the chickens tolerated 500
mg/kg without a decrease in growth rate, which is similar
to prior experiments (Berg et al., 1980; NRC, 1980). Grow-
ing pigs are also relatively sensitive to chronic lead expo-
sure as indicated by one experiment where feeding 25 mg
Pb/kg diet as lead acetate resulted in decreased weight gain
and efficiency of gain (Phillips et al., 2003).
Lead sulfate at 500 mg Pb/kg diet had no apparent effect
on calves (Logner et al., 1984), but 1,000 mg/kg resulted in
decreased weight gain and feed efficiency (Neathery et al.,
1987). In ponies, lead toxicosis from consumption of con-
taminated hay resulted initially in weakness and slight inco-
ordination followed in time by difficulty swallowing and
decreased muscle control of the lips and rectal sphincter, and
eventually by muscular tremors, severe incoordination, and
esophageal paralysis (Burrows and Borchard, 1982). Similar
clinical signs have been observed in calves and goats
(Zmudski et al., 1983; Zmudzki et al., 1985; Swarup and
Dwivedi, 1992).
The prominent indication of lead toxicosis via water ex-
posure in fish is darkening of the skin extending from the
caudal fin to the anal fin. In rainbow trout, blackening of the
tail is a more sensitive indicator of lead exposure than liver,
kidney, or brain histopathology and occurs at 120 \ig Pb/L
(Sippel et al., 1983). When lead is delivered as part of the
diet, blackening of the tail is not a prominent clinical sign,
and changes in growth rate, behavior, and histopathology
are diagnostic. Rainbow trout tolerate 45 mg Pb/kg diet as
lead nitrate with no apparent effect (Sippel et al., 1983).
Factors Influencing Toxicity
The dietary level at which lead becomes toxic is affected
by other dietary constituents and by the physiological state
of the animal (Scheuhammer, 1987a). Animals can tolerate
considerably higher daily exposure levels of lead when it is
consumed in the diet than when it is delivered in the water.
Lead ingested in the water without simultaneous food con-
sumption is considerably more toxic than when water is
ingested with a meal. Among dietary factors, calcium is
very important in modulating lead toxicity. Animals fed
low calcium diets exhibit increased susceptibility to lead
toxicosis as a consequence of increased lead retention as-
sociated with decreased renal excretion of lead. High lev-
els of calcium and phosphorus decrease intestinal absorp-
tion of lead and decrease its toxicity. Lead toxicosis also
impairs vitamin D metabolism and increases the apparent
need for dietary calcium.
Low dietary iron increases the susceptibility of animals
to lead intoxication and increases tissue deposition of lead
because of enhanced gastrointestinal absorption. Lead ab-
sorption, tissue deposition, and toxicity are enhanced by
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LEAD
217
physiological factors that increase absorption of iron, such
as fast growth, gestation, and lactation. High dietary zinc has
been shown to have a protective effect against lead toxicosis
in rats, chicks, horses, and rabbits. The protective action of
zinc on lead toxicity is thought to be mediated by decreased
absorption (Brewer et al., 1985). Unlike zinc, high levels of
cadmium increase lead deposition and toxicity (Prasada Rao
et al., 1989; Phillips et al., 2003).
Lactose promotes lead absorption in rats and in calves
(Zmudzki et al., 1986). In chicks, monensin or selenium in-
creases accumulation of lead in tissues and decreases the
amount of lead needed to cause anemia (Khan et al., 1993,
1994). Addition of methionine to a deficient diet decreases
the toxicity of lead to growing chicks by increasing lead ex-
cretion (Latta and Donaldson, 1986).
The toxicity of lead to fish decreases with increasing hard-
ness of the water. Lead readily forms PbC032 in hard water
and is poorly absorbed. Calcium in hard water also competes
with lead for absorption and decreases its toxicity. Lead spe-
cies such as Pb"*""*" and Pb(OH)"^ are more prominent in
softwater and are more available and toxic.
Once lead has been absorbed, methods to minimize its
toxic effects are based on chelation to reduce the body bur-
den. The standard chelating agents currently in use are
CaNa2-EDTA, meso-2,3-dimercaptosuccinic acid (DMS A),
and dimercaprol (BAL). Thiamin supplementation dimin-
ishes the clinical signs of lead toxicosis to cattle (Coppock et
al., 1991).
TISSUE LEVELS
Accumulation of lead in tissues is dependent upon the
dose and the length of exposure. These relationships have
been extensively detailed in rat models (IPCS, 1995;
ATSDR, 1999). In one study, rats exposed to 50 mg Pb/L
water as lead acetate for 90 days accumulated lead in tissues
in the order kidney > brain > spleen > prostate > heart >
testis and liver. Muscle is not a predominant site of lead ac-
cumulation. At 5 mg/L, significant lead accumulation was
seen only in the brain and kidney. In most organs, the lead
concentration was highest 2 weeks after dosing began and
subsequently declined. However, in the brain, lead increased
gradually over the 90-day dosing period (Areola et al., 1999).
In sheep fed 1,000 mg/kg lead acetate, muscle levels reached
a maximum in 30 days and then began to decline (Pearl et
al., 1983). Similarly in fish, lead uptake reaches equilibrium
after several weeks of exposure and decreases in some tis-
sues. In fish, lead is accumulated mostly in the gill, liver,
kidney, and bone (IPCS, 1989).
The relationship between lead exposure level and tissue
accumulation is summarized in Table 17-2. Concentrations
of lead in muscle and milk are relatively low and remain so
unless high dietary levels are fed. Lead accumulates in kid-
ney and bone even when relatively low levels of lead are
added to the diet. Similar observations have been made in
the field. In acutely sick cattle poisoned by licking the re-
mains of storage batteries burned and left in a pasture, levels
of lead in milk averaged 0.08 mg/L and in the muscle ranged
from 0.23 to 0.5 mg/kg (wet weight basis) compared to nor-
mal levels of below 0.005 and 0.01 mg/kg, respectively. Very
high concentrations were found in the kidneys, with a range
of 70-330 mg/kg (Oskarsson et al., 1992). In cattle grazing
near a lead smelter, the tissue lead levels were highest in
cattle grazing near the smelter and decreased with distance
(Neuman and Dollhopf, 1992).
Accumulation of lead in the eggs of chickens is not well
characterized. In one study, hens were dosed with lead ac-
etate starting at 5 and increasing to 100 mg Pb/kg BW/day
over a period of 102 weeks. During the dosing period, the
level of lead in egg yolks from controls ranged from 0.08 to
0.18 mg/kg. In the yolks from lead-dosed hens, lead ranged
from 0.40 to 1.08 mg/kg. Levels in egg white were always
less than 0.4 mg/kg and were not affected by dietary lead
(Mazliah et al., 1989).
MAXIMUM TOLERABLE LEVELS
The maximum tolerable level of lead is defined as the
dietary level that, when fed for a defined period of time, will
not impair accepted indices of animal health or performance.
Rainbow trout are among the most sensitive fish to lead toxi-
cosis. Juveniles of this species can tolerate chronic consump-
tion of 45 mg Pb/kg diet and can tolerate levels of 50 pg Pb/L
water. Rats and dogs tolerate 10 mg lead/kg diet without
changes in functional indices in hematopoiesis or kidney
function. In chickens and quail, slight but significant changes
in growth and egg production occur with the addition of 1
mg Pb/kg diet as lead acetate, and 0.5 mg/kg of highly
soluble lead source appears to be a maximum tolerable dose
for chronic exposure in these species when dietary calcium
levels are low. However, when dietary calcium levels are
high, 100 mg Pb/kg diet is tolerated. In pigs, 25 mg Pb/kg
diet from lead acetate results in decreased growth, but there
is insufficient information to establish a maximum tolerable
dose in this species. In ruminants, 250 mg/kg lead in the diet
can be tolerated for several months without significant ef-
fects on performance; however, levels of lead in kidneys and
bone become of concern if consumed by humans. It should
be noted that the above MTL are for highly available sources
such as lead acetate. Animals are likely able to tolerate higher
levels of many lead sources. As discussed in the
"Bioavailability" section, the bioavailability of lead in soil
and municipal sewage is about half of that in lead acetate
and metallic lead is only 15 percent as available.
HUMAN HEALTH
Muscle tissue does not accumulate marked amounts of
lead; however, levels in bone and kidney can be unaccept-
ably high in animals suffering from lead toxicosis. Lead does
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218
MINERAL TOLERANCE OF ANIMALS
not migrate significantly from bone to meat under a variety
of coolcing regimens (Baxter et al., 1992).
FUTURE RESEARCH NEEDS
There are inadequate data to accurately define MTL for
lead from dietary or water sources for most nonlaboratory
animals. Few studies have included incremental dose levels
adequate for determining thresholds for toxicity. Addition-
ally, most studies utilize lead acetate, but this is not a form
that animals would be exposed to via diet, water, or acci-
dents. Studies using metallic lead and lead salts found in
typical contaminants are needed. Most studies on toxicity of
lead in water use distilled water and single daily doses, usu-
ally to animals with empty stomachs. Research is needed
where water is provided for ad libitum consumption and the
water has typical hardness characteristics.
SUMMARY
Lead is a common cause of accidental poisonings in ani-
mals. Primary sources of lead exposure to animals include
contaminated soils and lead-based products, especially bat-
teries and older paints. Most plants do not take up large
amounts of lead from the soil, and plant-based feed ingredi-
ents are low in lead unless they are contaminated by soil or
airborne sources. Lead in feed is not efficiently absorbed,
but lead in water consumed without a meal is much more
available. Young animals absorb lead more efficiently than
older animals and have a lower tolerance. Most research on
lead toxicity has utilized lead acetate, which is highly avail-
able. Animals are more likely to be exposed to metallic lead
or lead salts that are considerably less available. Low levels
of lead exposure cause subtle cardiovascular, hematological,
and neurodevelopmental changes. Higher levels of exposure
cause renal, gastrointestinal, hepatic, and immunological dis-
turbances. Lead accumulates in kidney, brain, and bone.
Muscle is not a major site of accumulation except at very
high doses of lead.
REFERENCES
Araki, S., H. Sato, K. Yokoyama, and K. Murata. 2000. Subclinical neuro-
physiological effects of lead: a review on peripheral, central, and auto-
nomic nervous system effects in lead workers. Am. J. Ind. Med. 37:
193-204.
Areola, O. O., M. Williams- Johnson, and A. L. Jadhav. 1999. Relationship
between lead accumulation in blood and soft tissues of rats
subchronically exposed to low levels of lead. Toxic Subst. Mech. 18:
1-13.
ATSDR (Agency for Toxic Substances and Disease Registry). 1999. Toxi-
cological profile for lead. Atlanta, GA: U.S. Department of Health and
Human Services, Public Health Service.
Azar, A., H. J. Trochimowicz, and M. E. Maxfield. 1973. Pp. 199-210 in
Review of Lead Studies in Animals Carried out at Haskell Laboratory:
Two Year Feeding Study and Response to Hemorrhage Study, D. Barth,
A. Berlin, and R. Engel, eds. Luxembourg: Commission of the Euro-
pean Communities, Amsterdam.
Bakalli, R. I., G. M. Pesti, and W. L. Ragland. 1995a. The magnitude of
lead toxicity in broiler chickens. Vet. Hum. Toxicol. 37:15—19.
Bakalli, R. I., G. M. Pesti, W. L. Ragland, V. Konjufca, and R. Novak.
1995b. Delta-aminolevulinic acid dehydratase: a sensitive indicator of
lead exposure in broiler chicks (gallus domesticus). Bull. Environ.
Contam. Toxicol. 55:833-839.
Barltrop, D., and F. Meek. 1975. Absorption of different lead compounds.
Postgrad. Med. J. 51:805-809.
Barltrop, D., and F. Meek. 1979. Effect of particle size on lead absorption
from the gut. Arch. Environ. Health 34:280-285.
Baxter, M. J., J. A. Burrell, H. M. Crews, A. Smith, andR. C. Massey. 1992.
Lead contamination during domestic preparation and cooking of pota-
toes and leaching of bone-derived lead on roasting, marinading and boil-
ing beef Food Addit. Contam. 9:225-235.
Beach, J. R., and S. J. Henning. 1988. The distribution of lead in milk and
the fate of milk lead in the gastrointestinal tract of suckling rats. Pediatr.
Res. 23:58-62.
Berg, L. R., J. O. Nordstrom, and L. E. Ousterhout. 1980. The prevention of
chick growth depression due to dietary lead by increased dietary cal-
cium and phosphorus levels. Poult. Sci. 59:1860-1863.
Berny, P. J., L. M. Cote, and W. B. Buck. 1994. Relationship between soil
lead, dust lead, and blood lead concentrations in pets and their owners:
evaluation of soil lead threshold values. Environ. Res. 67:84—97.
Blaxter, K. L. 1950. Lead as a nutritional hazard to livestock. J. Comp.
PathoL 60:140-151.
Brar, R. S., H. S. Sandhu, S. S. Randhawa, and G. S. Grewal. 1997. Effect
of repeated oral toxicity of lead on activities of some plasma enzymes in
domestic fowls. Indian J. Anim. Sci. 67:878-879.
Bressler, J. P., and G. W. Goldstein. 1991. Mechanism of lead neurotoxic-
ity. Biochem. Pharmacol. 41:479^84.
Bressler, J., K. A. Kim, T. Chakraborti, and G. Goldstein. 1999. Molecular
mechanisms of lead neurotoxicity. Neurochem. Res. 24:595-600.
Bressler, J. P., L. Olivi, J. H. Cheong, Y. Kim, and D. Bannona. 2004.
Divalent metal transporter 1 in lead and cadmium transport. Ann. N. Y.
Acad. Sci. 1012:142-152.
Brewer, G. J., G. M. Hill, R. D. Dick, A. S. Prasad, and Z. T. Cossack. 1985.
Interactions of trace elements: clinical significance. J. Am. Coll. Nutr.
4:33-38.
Brewster, U. C, and M. A. Perazella. 2004. A review of chi'onic lead intoxi-
cation: an unrecognized cause of chronic kidney disease. Am. J. Med.
Sci. 327:341-347.
Burden, V. M., M. B. Sandheinrich, and C. A. Caldwell. 1998. Effects of
lead on the growth and delta-aminolevulinic acid dehydratase activity
of juvenile rainbow trout, oncorhynchus mykiss. Environ. Pollut.
101:285-289.
Burger, J. 1995. A risk assessment for lead in birds. J. Toxicol. Environ.
Health 45:369-396.
Burger, J., and M. Gochfeld. 2000. Effects of lead on birds (laridae): a
review of laboratory and field studies. J. Toxicol. Environ. Health Part
B: Critical Reviews 3:59-78.
Burrows, G. E. 1982. Lead poisoning in the horse. Equine Prac. 4:30—36.
Burrows, G. E., and R. E. Borchard. 1982. Experimental lead toxicosis in
ponies: comparison of the effects of smelter effluent-contaminated hay
and lead acetate. Am. J. Vet. Res. 43:2129-2133.
Cake, K. M., R. J. Bowins, C. Vaillancourt, C. L. Gordon, R. H. McNutt. R.
Laporte, C. E. Webber, and D. R. Chettle. 1996. Partition of circulating
lead between serum and red cells is different for internal and external
sources of lead. Am. J. Ind. Med. 29:440^445.
Casteel, S. W., R. P. Cowart, C. P. Weis, G. M. Henningsen, E. Hoffman,
W. J. Brattin, R. E. Guzman, M. F. Starost, J. T. Payne, S. L. Stockham,
S. V. Becker, J. W. Drexler, and J. R. Turk. 1997. Bioavailability of lead
to juvenile swine dosed with soil from the Smuggler Mountain NPL site
of Aspen, Colorado. Fundam. Appl. Toxicol. 36:177-187.
Coppock, R. W., W. C. Wagner, and R. D. Reynolds. 1988. Migration of
lead in a glass-lined bottom-unloading silo. Vet. Hum. Toxicol.
30:458-459.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
LEAD
219
Coppock, R. W., W. C. Wagner, J. D. Reynolds, R. S. Vogel, H. B. Gelberg,
L. Z. Florence, and W. A. Wolff. 1991. Evaluation of edetate and thia-
mine for treatment of experimentally induced environmental lead poi-
soning in cattle. Am. J. Vet. Res. 52:1860-1865.
De Francisco, N., J. D. Ruiz Troya, and E. I. Aguera. 2003. Lead and lead
toxicity in domestic and free living birds. Avian Pathol. 32:3-13.
Dieter, M. P., H. B. Matthews, R. A. Jeffcoat, and R. F. Moseman. 1993.
Comparison of lead bioavailability in f344 rats fed lead acetate, lead
oxide, lead sulfide, or lead ore concentrate from Skagway, Alaska. J.
Toxicol. Environ. Health 39:79-93.
Dietert, R. R., J. E. Lee, I. Hussain, and M. Piepenbrink. 2004. Develop-
mental immunotoxicology of lead. Toxicol. Appl. Pharmacol. 198:
86-94.
DoUahite, J. W., L. D. Rowe, and J. C. Reagor. 1975. Experimental lead
poisoning in horses and Spanish goats. Southwest Vet. 28:40^2.
Eckel, W. P., M. B. Rabinowitz, and G. D. Foster. 2002. Investigation of
unrecognized former secondary lead smelting sites: confirmation by
historical sources and elemental ratios in soil. Environ. Pollut. 117:
273-279.
Edens, F. W., and J. D. Garlich. 1983. Lead-induced egg production de-
crease in leghorn and Japanese quail hens. Poult. Sci. 62:1757—1763.
Edens, F. W., and V. K. Melvin. 1989. Lead influences on physiological
and growth responses in Coturnix japonica selected for large body
weights. Environ. Res. 50:140-156.
Eisler, R. 1988. Lead hazards to fish, wildlife, and invertebrates: a synoptic
review. U.S. Fish and Wildlife Biological Report 85 (1.14).
EPA (U.S. Environmental Protection Agency). 1999. Integrated Risk Infor-
mation System (IRIS). Cincinnati: U.S. Environmental Protection
Agency, Office of Health and Environmental Assessment, Environmen-
tal Criteria and Assessment Office.
Flegal, A. R., and D. R. Smith. 1995. Measurements of environmental lead
contamination and human exposure. Rev. Environ. Contam. Toxicol.
143:1^5.
Fowler, B. A. 1998. Roles of lead-binding proteins in mediating lead
bioavailability. Environ. Health Perspect. 106 (Suppl 6): 1585-1 587.
Franklin, C. A., M. J. Inskip, C. L. Baccanale, C. M. Edwards, W. I. Manton,
E. Edwards, and E. J. O'Flaherty. 1997. Use of sequentially adminis-
tered stable lead isotopes to investigate changes in blood lead during
pregnancy in a nonhuman primate (macaca fascicularis). Fundam. Appl.
Toxicol. 39:109-119.
Freeman, G. B., J. D. Johnson, J. M. Kilhnger, S. C. Liao, P. I. Feder, A. O.
Davis, M. V. Ruby, R. L. Chaney, S. C. Lovre, and P. D. Bergstrom.
1992. Relative bioavailability of lead from mining waste soil in rats.
Fundam. Appl. Toxicol. 19:388-398.
Freeman, G. B., J. D. Johnson, S. C. Liao, P. I. Feder, A. O. Davis, M. V.
Ruby, R. A. School, R. L. Chaney, and P. D. Bergstrom. 1994. Absolute
bioavailability of lead acetate and mining waste lead in rats. Toxicology
91:151-163.
Freeman, G. B., J. A. Dill, J. D. Johnson, P. J. Kurtz, F. Parham, and H. B.
Matthews. 1996. Comparative absorption of lead from contaminated
soil and lead salts by weanling fischer 344 rats. Fundam. Appl. Toxicol.
33:109-119.
Fullmer, C. S. 1991. Intestinal calcium and lead absorption: effects of di-
etary lead and calcium. Environ. Res. 54:159-169.
Galey, F. D., B. D. Slenning, M. L. Anderson, P. C. Breneman, E. S.
Littlefield, L. A. Melton, and M. L. Tracy. 1990. Lead concentra-
tions in blood and milk from periparturient dairy heifers seven
months after an episode of acute lead toxicosis. J. Vet. Diagn. In-
vest. 2:222-226.
Gill, K. D., V. Gupta, and R. Sandhir. 2003. Ca2-H/calmodulin-mediated
neurotransmitter release and neurobehavioural deficits following lead
exposure. Cell Biochem. Funct. 21:345-353.
Goering, P. L. 1993. Lead-protein interactions as a basis for lead toxicity.
Neurotoxicology 14:45-60.
Goldstein, G. W. 1993. Evidence that lead acts as a calcium substitute in
second messenger metabolism. Neurotoxicology 14:97-102.
Goyer, R. A. 1990. Transplacental transport of lead. Environ. Health
Perspect. 89:101-105.
Goyer, R. A. 1993. Lead toxicity: current concerns. Environ. Health
Perspect. 100:177-187.
Grandjean, P., and B. Olsen. 1984. Lead. Pp. 153-169 in Techniques and
Instrumentation in Analytical Chemistry. Volume 4: Evaluation of Ana-
lytical Methods in Biological Aystems. Part B: Hazardous Metals in
Human Toxicology, A. Vercruysse, ed. New York: Elsevier Science.
Hallen, 1. P., and A. Oskarsson. 1995. Bioavailability of lead from various
milk diets studied in a suckling rat model. Biometals 8:231—236.
Hamir, A. N., N. D. Sullivan, and P. D. Handson. 1984. Neuropathological
lesions in experimental lead toxicosis of dogs. J. Comp. Pathol.
94:215-231.
Hamir, A. N., N. D. Sullivan, and P. D. Handson. 1988. Tissue lead distri-
bution and pathological findings in lead exposed dogs maintained on fat
and calcium modified diets. Br. Vet. J. 144:240-245.
Hsu, P. C, and Y. L. Guo. 2002. Antioxidant nutrients and lead toxicity.
Toxicology 180:33^4.
IPCS (International Programme on Chemical Safety). 1989. Environmental
Health Criteria 85 — Lead, Environmental Aspects. Geneva: World
Health Organization.
IPCS. 1995. Environmental Health Criteria 165 — Inorganic Lead. Geneva:
World Health Organization.
Johnston, M. V., andG. W. Goldstein. 1998. Selective vulnerability of the
developing brain to lead. Curr. Opin. Neurol. 1 1:689-693.
Khan, M. Z., J. Szarek, A. Krasnodebska-Depta, and A. Koncicki. 1993.
Effects of concurrent administration of lead and selenium on some
haematological and biochemical parameters of broiler chickens. Acta
Vet. Hung. 41:123-137.
Khan, M. Z., J. Szarek, A. Koncicki, and A. Krasnodebska-Depta. 1994.
Oral administration of monensin and lead to broiler chicks: effects
on haematological and biochemical parameters. Acta Vet. Hung.
42:111-120.
Kirchgessner, M., D. L. Plass, and A. M. Reichlmayr-Lais. 1991. Lead de-
ficiency in swine. Pp. 1 1—21 in Proceedings of the Seventh International
Symposium on Trace Elements in Man and Animals (Tema 7), B.
Momcilovic, ed. Dubrovinik: IMI.
Klaassen, C. D., andD. W. Shoeman. 1974. Biliary excretion of lead in rats,
rabbits, and dogs. Toxicol. Appl. Pharmacol. 29:434^446.
Knight, T. E., and M. S. Kumar. 2003. Lead toxicosis in cats — a review. J.
Feline Med. Surg. 5:249-255.
Knowles, S. O., and W. E. Donaldson. 1997. Lead disrupts eicosanoid me-
tabolism, macrophage function, and disease resistance in birds. Biol.
Trace Elem. Res. 60:13-26.
Kopp, S. J., J. T. Barron, and J. P. Tow. 1988. Cardiovascular actions of
lead and relationship to hypertension: a review. Environ. Health
Perspect. 78:91-99.
Lassen, E. D., and W. B. Buck. 1979. Experimental lead toxicosis in swine.
Am. J. Vet. Res. 40:1359-1364.
Latta, D. M., and W. E. Donaldson. 1986. Lead toxicity in chicks: interac-
tions with dietary methionine and choline. J. Nutr. 116:1561-1568.
Loghman-Adham, M. 1997. Renal effects of environmental and occupa-
tional lead exposure. Environ. Health Perspect. 105:928-939.
Logner, K. R., M. W. Neathery, W. J. Miller, R. P. Gentry, D. M. Blackmon,
and F. D. White. 1984. Lead toxicity and metabolism from lead sulfate
fed to Holstein calves. J. Dairy Sci. 67:1007-1013.
Lu, J., G. Petroianu, B. Widjaja, and R. Ruefer. 1997. Transplancental ki-
netics of lead in pregnant mini-pigs. Arch. Toxicol. 71:187-192.
Lubran, M. M. 1980. Lead toxicity and heme biosynthesis. Ann. Clin. Lab.
Sci. 10:402^13.
Maddaloni, M., N. Lolacono, W. Manton, C. Blum, J. Drexler, and J.
Graziano. 1998. Bioavailability of soilborne lead in adults, by stable
isotope dilution. Environ. Health Perspect. 106 (Suppl. 6):1589-1594.
Manser, W.W. 1991. Lead — an essential trace element. J. Pak. Med. Assoc.
41:48.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
220
MINERAL TOLERANCE OF ANIMALS
Mareal, W. S., L. Gaste, M. Liboni, P. E. Pardo, M. R. Nascimento, and C.
S. Hisasi. 2001. Concentration of lead in mineral salt mixtures used as
supplements in cattle food. Exp. Toxicol. Pathol. 53:7-9.
Marchetti, C. 2003. Molecular targets of lead in brain neurotoxicity.
Neurotox. Res. 5:221-236.
Mazliah, J., S. Barron, E. Bental, and 1. Reznik. 1989. The effect of chronic
lead intoxication in mature chickens. Avian Dis. 33:566—570.
McCarthy, H. T., and P. C. Ellis. 1991. Comparison of microwave digestion
with conventional wet ashing and dry ashing digestion for analysis of
lead, cadmium, chromium, copper, and zinc in shellfish by flame atomic
absorption spectroscopy. J. Assoc. Off. Anal. Chem. 74:566—569.
Morgan, R. V. 1994. Lead poisoning in small companion animals: an up-
date (1987-1992). Vet. Hum. Toxicol. 36:18-22.
Neathery, M. W., W. J. Miller, R. P. Gentry, C. T. Crowe, E. Alfaro, A. S.
Fielding, D. G. Pugh, and D. M. Blackmon. 1987. Influence of high
dietary lead on selenium metabolism in dairy calves. J. Dairy Sci.
70:645-652.
Needleman, H. 2004. Lead poisoning. Annu. Rev. Med. 55:209-222.
Neuman, D. R., and D. J. DoUhopf. 1992. Lead levels in blood from cattle
residing near a lead smelter. J. Environ. Qual. 21:181-184.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
O'Flaherty, E. J. 1998. A physiologically based kinetic model for lead in
children and adults. Environ. Health Perspect. 106 (Suppl. 6):1495-1503.
Oskarsson, A., L. Jorhem, J. Sundberg, N. G. Nilsson, and L. Albanus.
1992. Lead poisoning in cattle — transfer of lead to milk. Sci. Total
Environ. 111:83-94.
Pagliuca, A., G. J. Mufti, D. Baldwin, A. N. Lestas, R. M. Wallis, and A. J.
Bellingham. 1990. Lead poisoning: clinical, biochemical, and
haematological aspects of a recent outbreak. J. Clin. Pathol. 43 :277-28 1 .
Pearl, D. S., C. B. Ammerman, P. R. Henry, and R. C. Littell. 1983. Influ-
ence of dietary lead and calcium on tissue lead accumulation and deple-
tion, lead metabolism and tissue mineral composition in sheep. J. Anim.
Sci. 56:1416-1426.
Phillips, C, Z. Gyori, and B. Kovacs. 2003. The effect of adding cadmium
and lead alone or in combination to the diet of pigs on their growth, car-
case composition and reproduction. J. Sci. Food Agric. 83:1357-1365.
Polak, J. E., J. O'Flaherty, G. B. Freeman, J. D. Johnson, S. C. Liao, and P.
D. Bergstrom. 1996. Evaluating lead bioavailability data by means of a
physiologically based lead kinetic model. Fundam. Appl. Toxicol.
29:63-70.
Pounds, J. G., G. J. Long, and J. F. Rosen. 1991. Cellular and molecular
toxicity of lead in bone. Environ. Health Perspect. 91:17—32.
Prasada Rao, P. V., S. A. Jordan, and M. K. Bhatnagar. 1989. Combined
nephi'otoxicity of methylmercury, lead, and cadmium in pekin ducks:
metallothionein, metal interactions, and histopathology. J. Toxicol.
Environ. Health 26:327-348.
Prescott, C. W. 1983. Clinical findings in dogs and cats with lead poison-
ing. Aust. Vet. J. 60:270-271.
Regan, C. M. 1989. Lead-impaired neurodevelopment. Mechanisms and
threshold values in the rodent. Neurotoxicol. Teratol. 1 1 :533-537.
Reichlmayr-Lais, A. M., and M. Kirchgessner. 1981. (In German; English
Summary.) Essentiality of lead for growth and metabolism. Z.
Tierphysiol. Tierernahr. Futtermittelkd. 46:1-8.
Rice, D. C. 1998. Effects of lifetime lead exposure on spatial and temporal
visual function in monkeys. Neurotoxicology 19:893-902.
Rogers, J. T., J. G. Richards, and C. M. Wood. 2003. lonoregulatory disrup-
tion as the acute toxic mechanism for lead in the rainbow trout
(oncorhynchus mykiss). Aquatic Toxicol. 64:215-234.
Sallmen, M. 2001. Exposure to lead and male fertility. Int. J. Occup. Med.
Environ. Health 14:219-222.
Scheuhammer, A. M. 1987a. The chronic toxicity of aluminum, cadmium,
mercury, and lead in birds: a review. Environ. Pollut. 46:263-295.
Scheuhammer, A. M. 1987b. Erythrocyte delta-aminolevulinic acid dehy-
dratase in birds. li. The effects of lead exposure in vivo. Toxicology
45:165-175.
Sharma, R. P., J. C. Street, J. L. Shupe, and D. R. Bourcier. 1982. Accumu-
lation and depletion of cadmium and lead in tissues and milk of lactat-
ing cows fed small amounts of these metals. J. Dairy Sci. 65:972-979.
Silbergeld, E. K., J. Sauk, M. Somerman, A. Todd, F. McNeill, B. Fowler,
A. Fontaine, and J. van Buren. 1993. Lead in bone: storage site, expo-
sure source, and target organ. Neurotoxicology 14:225—236.
Sippel, A. J. A., J. R. Geraci, and P. Hodson. 1983. Histo pathological and
physiological responses of rainbow trout salmo-gairdneri to sublethal
levels of lead. Water Res.l7:ll 15-1 118.
Smith, C. M., H. F. DeLuca, Y. Tanaka, and K. R. Mahaffey. 1981. Effect
of lead ingestion on functions of vitamin d and its metabolites. J. Nutr.
111:1321-1329.
Smith, J. R. 2002. Minerals Yearbook: Lead No. 2004. Reston, VA: U.S.
Geological Survey.
Sorenson, E. M. 1991. Metal Poisoning in Fish. Boca Raton, FL: CRC
Press.
Steiss, J. E., K. G. Braund, and E. G. Clark. 1985. Inability to experimen-
tally produce a polyneuropathy in dogs given chronic oral low level
lead. Can. J. Comp. Med. 49:401^04.
Stone, C. L., M. R. Fox, and K. S. Hogye. 1981. Bioavailability of lead in
oysters fed to young Japanese quail. Environ. Res. 26:409^21.
Strojan, S. T., and C. J. C. Phillips. 2002. The detection and avoidance of
lead-contaminated herbage by dairy cows. J. Dairy Sci. 85:3045-3053.
Swarup, D., and S. K. Dwivedi. 1992. Changes in blood and cerebrospinal
fluid indices in experimental lead toxicity in goats. Indian J. Anim. Sci.
62:928-931.
Tabche, L. M., C. M. Martinez, and E. Sanchez-Hidalgo. 1990. Compara-
tive study of toxic lead effect on gill and hemoglobin of tilapia fish. J.
Appl. Toxicol. 10:193-196.
Van Der Veen, N. G., and K. Vreman. 1986. Transfer of cadmium lead
mercury and arsenic from feed into various organs and tissues of fatten-
ing lambs. Neth. J. Agric. Sci. 34:145-154.
Varnai, V. M., M. Piasek, M. Blanusa, M. M. Saric, D. Simic, and K.
Kostial. 200 1 . Calcium supplementation efficiently reduces lead absorp-
tion in suckling rats. Pharmacol. Toxicol. 89:326-330.
Vaziri, N. D. 2002. Pathogenesis of lead-induced hypertension: role of oxi-
dative stress. J Hypertens. 20 (Suppl. 3):S 15-20.
Vreman, K., N. G. Van Der Veen, E. J. Van Der Molen, and W. G. De Ruig.
1986. Transfer of cadmium lead mercury and arsenic from feed into
milk and various tissues of dairy cows chemical and pathological data.
Neth. J. Agric. Sci. 34:129-144.
Waldner, C, S. Checkley, B. Blakley, C. Pollock, and B. Mitchell. 2002.
Managing lead exposure and toxicity in cow-calf herds to minimize the
potential for food residues. J. Vet. Diagn. Invest. 14:481^86.
Warren, M. J., J. B. Cooper, S. P. Wood, and P. M. Shoolingin-Jordan.
1998. Lead poisoning, haem synthesis and 5-aminolaevulinic acid de-
hydratase. Trends Biochem. Sci. 23:217-221.
Winneke, G., H. Lilienthal, and U. Kramer. 1996. The neurobehavioural
toxicology and teratology of lead. Arch. Toxicol. Suppl. 18:57-70.
Youssef, S. A., A. A. El-Sanousi, N. A. Afifi, and A. M. El Brawy. 1996.
Effect of subclinical lead toxicity on the immune response of chickens
to Newcastle disease virus vaccine. Res. Vet. Sci. 60:13-16.
Zhao, F. J., M. L. Adams, C. Dumont, S. P. McGrath, F. A. Nicholson, B. J.
Chambers, and A. H. Sinclair. 2004. Factors affecting the concentrations
of lead in British wheat and barley grain. Environ. Pollut. 131:461^68.
Zmudski, J., G. R. Bratton, C. Womac, and L. Rowe. 1983. Lead poisoning
in cattle: reassessment of the minimum toxic oral dose. Bull. Environ.
Contam. Toxicol. 30:435^141.
Zmudzki, J., G. R. Bratton, C. Womac, and L. D. Rowe, Jr. 1985. Low dose
lead effects in calves fed a whole milk diet. Bull. Environ. Contam.
Toxicol. 35:612-619.
Zmudzki, J., G. R. Bratton, C. W. Womac, L. D. Rowe, Jr., and B. Wagner.
1986. Lactose and milk replacer influence on lead absorption and lead
toxicity in calves. Bull. Environ. Contam. Toxicol. 36:356—363.
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18
Magnesium
INTRODUCTION
Magnesium (Mg) is a divalent cation belonging to Group
IIA of the periodic table of elements. In its pure form, magne-
sium is a silvery gray, very light metal that corrodes easily and
is also highly inflammable. Magnesium is most commonly
found in the Earth's crust as magnesite, primarily composed
of magnesium carbonate hydroxide. Magnesium oxide is used
in many industrial processes as a means of neutralizing acidity
of solutions. Magnesium oxide is produced from magnesite
ore (MgC03)4 Mg(OH), by exposing the ore to high heat in a
process called calcining. The temperature and duration of the
calcination procedure determines the reactive properties
(grades) of the magnesium oxide.
Decomposition of magnesium carbonate to form magne-
sium oxide and carbon dioxide begins at a temperature
slightly above 400°C. Calcination temperatures of between
800°C and 1,000°C produce magnesium oxide with a rela-
tively high surface area and remarkable reactivity. This grade
reacts readily with water and fairly vigorously with diluted
acid solutions (stomach secretions). Grades produced at rela-
tively low temperatures (up to approximately 1,000°C) are
called caustic calcined magnesite, and are produced for a
wide variety of applications including animal feeds (Adam
et al., 1996). The finer the grinding of the magnesium oxide
particles, the better the availability of the magnesium for
absorption by animals. In contrast, calcining at temperatures
above 1,600°C produces "dead burnt" magnesite, a magne-
sium oxide with extremely low reactive properties that
should not be used in animal feeds as the magnesium is not
readily available for absorption. These grades are also called
sinter or sinter magnesite and are principally used in iron
foundries as a refractory brick material.
Though magnesium sulfate (Epsom salts) can be found in
relatively pure form in deposits in various parts of the world,
it is more commonly produced after the harvesting of com-
mon salt (halite). Magnesium sulfate is extracted from the
waste waters (bitterns) of solar salt operations by further
evaporation, refrigeration, and re-crystallization. Cooling the
diluted bittern to between -5°C and -10°C precipitates up to
70 percent of the magnesium sulfate, which is then filtered
to recover 85-96 percent pure Epsom salt that is marketed as
an industrial-grade Epsom salt.
ESSENTIALITY
Magnesium is a major intracellular cation that is a neces-
sary cofactor for enzymatic reactions vital to every major
metabolic pathway. Magnesium is a cofactor of many en-
zymes in the body including those involved in cellular respi-
ration and transfer of phosphate between adenosine triphos-
phate (ATP), adenosine diphosphate (ADP), and adenosine
monophosphate (AMP). Extracellular magnesium is vital to
normal nerve conduction, muscle function, and bone min-
eral formation. A common sign of magnesium deficiency in
all species is hyperexcitability caused by a reduction in nerve
resting membrane potential closer to the level at which an
action potential is triggered. Less severe signs of magnesium
deficiency include reduced appetite and poor performance.
Magnesium deficiency is also pro -inflammatory and is asso-
ciated with increases in oxidative stress in vivo and cardiac
susceptibility to ischemia/reperfusion (I/R) injury (Kramer
et al., 2003). Magnesium deficiency can increase the suscep-
tibility to toxicoses from various other metals such as alumi-
num (Nielsen et al., 1988). In freshwater fish, low magne-
sium water increases the uptake of copper (de
Schamphelaere and Janssen, 2002), cadmium (Michibata et
al., 1986), silver (Schwartz and Playle, 2001) and tin (Dou-
glas et al., 1996). Magnesium appears to out-compete these
toxic elements for metal binding ligands on the surface of
the gills, reducing uptake of these more toxic metals.
Magnesium deficiency occurs more commonly in rumi-
nants than nonruminants, especially those grazing in pas-
tures. This appears to be due to the low magnesium content
of lush growing pasture coupled with a relatively high con-
tent of potassium, protein, organic acids, and other antago-
224
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MAGNESIUM
225
nists that interfere with the transport of magnesium across
the rumen wall (Martens and Schweigel, 2000). In contrast
to nonruminants, adult ruminants must absorb magnesium
effectively from the forestomach if they are going to meet
their tissue magnesium requirements. Though the small in-
testine of ruminants can absorb magnesium, overall, the
small intestine is actually an area of net magnesium secre-
tion (Greene et al., 1983).
Because they are dependent on forestomach magnesium
absorption, the magnesium requirements of ruminant spe-
cies are higher than other species and range from 0.15-0.3
percent of the diet. For most nonruminant animals, including
most freshwater fish (Gatlin et al., 1982), requirements for
magnesium can be satisfied with just 0.06 percent magne-
sium diets (NRC, 1994, 1998, 2006). Nearly 60 percent of
the magnesium in the body is located within bone mineral,
and most of the rest is located within the intracellular fluids
of the body.
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Determination of magnesium in feeds and tissues is best
accomplished by wet or dry ashing of the sample followed
by resuspension of the ash in an acidic solution for analysis
by atomic absorption spectrophotometry. Atomic absorption
is conducted at a wavelength of 285.2 nm and can detect as
little as 0.001 mg magnesium per liter. Phosphate, silicon,
titanium, and aluminum that might be in the sample can in-
terfere with magnesium absorption spectra, but their effect is
masked by the addition of lanthanum to the standards and
samples being analyzed. Since low magnesium values result
if the pH of the sample is above 7, both standards and
samples are prepared in dilute hydrochloric acid solution.
Concentrations of calcium greater than 1,000 mg/L in the
analyzed ash suspension can also cause low magnesium val-
ues. Concentrations of up to 500 mg/L each of sodium, po-
tassium, and nitrate cause no interference. Anionic chemical
interferences can be expected if lanthanum is not used in
samples and standards (EPA, 1983). The nitrous oxide-acety-
lene flame will provide two to five times greater sensitivity
than an air-acetylene flame, but is not necessary for routine
analysis of feeds or biological samples. Near-infrared spec-
trophotometry is not an acceptable method of determining
magnesium content of feedstuffs or forages, though it is of-
ten used for that purpose.
Magnesium concentrations can also be measured to ppb
(ug/L) levels using the ICP-OES. The ICP uses radio fre-
quency-generated plasma to excite the electrons of the mag-
nesium atoms, which then produce photons of light unique
to magnesium. Photomultiplier tubes detect and quantitate
the photons emitted by the excited magnesium atoms, al-
lowing quantification of the magnesium concentration. An
inductively-coupled plasma source atomizes and excites
even the most refractory magnesium atoms with high effi-
ciency, so there is less interference and about 10-fold
greater sensitivity using ICP-OES than using atomic ab-
sorption spectrometry.
REGULATION AND METABOLISM
In nonruminant animals and young (preruminant) rumi-
nants, magnesium is absorbed primarily from the small in-
testine. In most cases, the dietary magnesium is readily
solubilized within the acidic environment of the stomach
and a large proportion remains available for absorption in
the upper duodenum. In adult ruminants, small intestine
secretion of magnesium generally exceeds small intestine
absorption of magnesium (Cragle, 1973) so that the rumi-
nant becomes highly dependent on absorption of magne-
sium across the forestomach walls to meet its magnesium
needs. Magnesium is usually absorbed by an active trans-
port process, which is especially useful when magnesium
content of the diet is low. Passive diffusion across gas-
trointestinal and forestomach walls can occur whenever
ionized magnesium concentration in the digestive fluid is
greater than the ionized magnesium content of the extracel-
lular fluids, which allows magnesium to flow down its con-
centration gradient into the blood.
Large amounts of magnesium are stored in bone where it
is an integral part of bone mineral crystals. However, it is not
readily labile and available for metabolic needs of the ani-
mal during periods of dietary magnesium insufficiency.
Magnesium homeostasis essentially consists of urinary ex-
cretion of any excess dietary magnesium that is absorbed.
About 72 percent of magnesium in the plasma (the portion
that is not bound to plasma proteins) crosses the glomerulus
and enters the renal tubular fluids. Under most circum-
stances, much of this magnesium is reabsorbed and passes
back into the plasma. Plasma magnesium concentration for
most mammals and birds is normally between 0.75 and 1.5
mmol/L or 18 and 36 mg/L. The kidneys play a key role in
maintaining magnesium homeostasis, but only under condi-
tions of hypermagnesemia. If dietary magnesium is absorbed
in excess of need, plasma magnesium concentration rises
above the renal threshold for reabsorption of magnesium and
the excess is excreted into the urine. The renal threshold for
magnesium, i.e., the plasma magnesium concentration at
which all magnesium filtered across the glomerulus is reab-
sorbed, is approximately 0.75 mmol/L or 18 mg/L in the
cow and 0.90 mmol/L or 22 mg/L in sheep, and closer to 1 .0
mmol/L for most other species (Littledike and Goff, 1987).
Plasma magnesium concentrations below these levels indi-
cate that dietary magnesium absorption is not sufficient and
little or no magnesium will be detected in urine. The renal
threshold is responsive to parathyroid hormone, which is
secreted in response to hypocalcemia, not hypomagnesemia.
Under the influence of parathyroid hormone, the renal tubu-
lar absorption of both calcium and magnesium is enhanced,
returning more of the filtered calcium and magnesium into
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226
MINERAL TOLERANCE OF ANIMALS
the blood, raising blood calcium and magnesium concentra-
tions. Unfortunately, since hypomagnesemia does not elicit
parathyroid hormone secretion, renal reabsorption of mag-
nesium does not improve in response to developing hypo-
magnesemia to any great extent (Rude et al., 1978).
Animals have no hormonal mechanisms that allow the
animal to adapt to a low magnesium diet for any length of
time by increasing intestinal magnesium absorption. Since
gastrointestinal magnesium absorption is not directly regu-
lated hormonally, the animal must receive a relatively con-
stant supply of magnesium in the diet to avoid developing
hypomagnesemia and deficiency symptoms.
SOURCES AND BIOAVAILABILITY
Magnesium is most commonly supplemented using mag-
nesium oxide. Pure magnesium oxide is 60.3 percent mag-
nesium and 39.7 percent oxygen. The heat of calcination re-
quired to form pure MgO from magnesite ore renders the
magnesium less bioavailable. Feed-grade sources of MgO
are incompletely calcined and are generally between 52 and
56 percent magnesium. Magnesium sulfate is more water
soluble than MgO and therefore more available for absorp-
tion than MgO. It is used less frequently because it is gener-
ally less palatable, has a stronger laxative effect, and is more
expensive than MgO (Miller, 1979). Similarly magnesium
chloride is available and occasionally used but is more ex-
pensive than MgO. Magnesium acetate is available but is
cost prohibitive for routine formulation of diets as a magne-
sium supplement. Dolomitic limestone is approximately 12
percent magnesium, and when used as a source of calcium it
will ordinarily supply all the magnesium needed to meet the
requirements of most nonruminant species if ground finely
enough to become solubilized in the stomach acids.
Plant uptake of magnesium increases with soil magne-
sium content. Magnesium fertilization of the soil can in-
crease plant magnesium content. High soil potassium tends
to decrease magnesium uptake from soils. Cool, wet weather
can also reduce plant magnesium content, which increases
susceptibility of grazing animals to development of hypo-
magnesemic tetany. In some forage systems, it is common
practice to spray magnesium oxide slurries onto the surface
of foliage that cattle or sheep are expected to graze within
the next few days to help avoid hypomagnesemia.
Most major feedstuffs used in diet formulation (corn,
wheat, soybean meal) contain more than 0.10 percent mag-
nesium. Therefore it is not usually necessary to supplement
diets of nonruminants with inorganic magnesium unless
purified ingredients dominate the diet.
TOXICOSIS
Magnesium toxicosis presents itself as three distinct clini-
cal pictures. These are hypermagnesemia with sedation, di-
arrhea, and inappetance, which all lead to reduced perfor-
mance. Only with a single very large dose of magnesium is it
possible to raise blood magnesium concentration to the ex-
tent necessary to observe sedation. Acute and chronic supple-
mentation with excessive magnesium can cause diarrhea and/
or inappetance. See Table 18-1 for effects of magnesium
exposure on animals.
Single Dose
When blood magnesium concentration is increased above
5 mEq/L (60 mg/L), there is a general reduction in nerve
activity and loss of muscle tone. Animals lose the ability to
stand. At 6 mEq/L, the heart rate slows and there are charac-
teristic changes observed in the electrocardiogram indica-
tive of reduced ventricular contraction. At about 7 mEq/L,
there is a loss of many of the reflexes of the body and there is
central nervous system depression. Above 10 mEq/L, the
animal is likely to go into a coma and there is a high risk of
asystolic cardiac arrest (Mordes and Wacker, 1978). Prior to
the 1930s and the development of suitable barbiturates for
veterinary anesthesia, veterinarians rapidly administered
magnesium intravenously to horses, cattle, and dogs to in-
duce a recumbent state to provide restraint for short surgical
procedures. The magnesium caused hyperpolarization of cell
membranes, reducing the likelihood that an action potential
could be generated in the nerves and muscles of the body.
The effective dose was about 0.025-0.028 g Mg/kg BW as
magnesium sulfate (Bowen et al., 1970). Smaller doses of
magnesium sulfate are often incorporated into chloral hy-
drate anesthesia protocols for horses to improve muscle re-
laxation. By increasing the intravenous dose of magnesium
above 0.2 g/kg BW, animals could be effectively euthanized
by inducing cardiac arrest (but not humanely by today's stan-
dards because consciousness may or may not be induced
first). Hypertonic magnesium sulfate administered rectally
can also cause an increase in blood magnesium concentra-
tion and was once used to treat hypomagnesemic tetanies of
cattle (Bacon et al., 1990). To achieve the same effects by
oral administration of magnesium would require very large
doses of readily soluble magnesium administered as a
drench. In most cases, the kidneys would be likely to rid the
body of the excess absorbed magnesium before blood mag-
nesium concentrations could rise to deleterious levels. In
fact, there are no reports of toxicosis from hypermagnesemia
following oral ingestion of magnesium occurring in animals
with intact renal function. Several cases of coma induced by
oral magnesium have been reported in humans, but in nearly
every case the person was in renal failure, which compro-
mised the ability of the body to rid itself of the excess ab-
sorbed magnesium (Fassler et al., 1985). In newborn lambs,
administration of 10 ml of a 25 percent magnesium sulfate
solution rectally induced coma and loss of deep tendon re-
flexes. Rectal administration of 10 ml of a 50 percent mag-
nesium sulfate solution caused cardiorespiratory failure in
less than an hour (Andrews et al., 1965). Based on this re-
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MAGNESIUM
227
search, it is assumed that a single oral dose of 0.10 g Mg/kg
BW (approximately one-half the dose causing sedation in
lambs) administered orally would not cause intolerable
hypermagnesemia in animals. Absorption of magnesium
administered orally is expected to be even slower and less
efficient than rectal administration and absorption across
the colon mucosa. Unfortunately, unabsorbed magnesium
can induce an osmotic diarrhea in animals. Cattle given
drenches consisting of between 102 and 205 g magnesium as
magnesium oxide developed severe scours within 48 hours.
Those receiving just 68 g magnesium suffered no diarrhea
(Care, 1960).
Magnesium sulfate, a saline laxative, is often used for
treatment of intestinal impactions in horses. Clinical signs of
hypermagnesemia are an uncommon complication follow-
ing oral administration of magnesium sulfate but have been
known to occur (Henninger and Horst, 1997). Renal insuffi-
ciency, hypocalcemia, or compromise of intestinal integrity
were thought to have predisposed the horses in this report to
magnesium toxicosis.
Acute
Care (1960) fed steers a diet that was 0.76 percent mag-
nesium for 8 days with no adverse effects, but diets that were
1.15 percent or greater magnesium induced diarrhea within
48 hours.
Chronic
Veal calves were fed milk replacers containing 0.1 per-
cent (NRC requirement), 0.3 percent, or 0.6 percent mag-
nesium for 16 weeks (Petersson et al., 1988). No adverse
effects were observed with the 0.3 percent magnesium diet.
However, weight gain was reduced in calves fed the 0.6
percent magnesium milk replacer and upon necropsy it was
discovered that 70 percent of calves fed 0.6 percent magne-
sium milk replacer had stones in their kidneys consisting
primarily of calcium apatite and secondarily of struvite.
Adding NaCI to the milk replacer reduced kidney and blad-
der calculi formation. When calves were allowed access to
water ad libitum, the added NaCl prevented calculi forma-
tion completely.
Lactating cows were fed diets that were either 0.37 or
0.63 percent magnesium. Cows that were fed the high mag-
nesium diet absorbed more total grams of dietary magne-
sium, but there were no differences in feed intake or milk
production in these cows during the 16 days of the trial
(Jittakhot et al., 2004). Holstein bull calves fed 1, 2, or 4
percent supplemental magnesium as magnesium oxide
(added to a control diet containing 0.3 percent magnesium)
experienced diarrhea with tubular mucus casts at all three
supplemental magnesium levels. As dietary magnesium con-
tent increased, the extent and intensity of the diarrhea in-
creased. High (2 and 4 percent) magnesium diets reduced
feed consumption and weight gains. Plasma magnesium rose
sharply in response to the increased intake of magnesium. In
calves receiving the 4 percent added magnesium, the plasma
values were abnormally high at 50-60 mg magnesium per
liter of plasma. Within 1 week after calves were returned to
the control diet, magnesium in urine and plasma declined to
control levels (Gentry et al., 1978).
In growing steers, increasing diet magnesium from 0.3 to
1.4 percent with magnesium oxide reduced diet DM digest-
ibility. Increasing diet magnesium to 2.5 or 4.7 percent
caused a magnesium dose-related loss in weight gain and
severe diarrhea and lethargy (Chester-Jones et al., 1990).
High magnesium chloride in the drinking water of sheep
(water was 0.2-0.3 percent magnesium chloride) caused oc-
casional diarrhea over a 16-month period and reduced the
growth rate of the sheep (Pierce, 1959).
Day-old chicks fed corn-soy rations containing adequate
amounts of calcium and phosphorus could be fed up to 0.5 1
percent magnesium in the diet with no adverse effects. How-
ever, when diet magnesium was increased to 0.71 percent,
the chicks exhibited poorer growth and their tibia were lower
in ash than control chicks (Chicco et al., 1967). Nugara and
Edwards (1963) fed broiler chicks diets that were 0.32 per-
cent magnesium with no ill effects but found that increasing
magnesium content to 0.64 percent reduced body weight and
bone ash and increased mortality. Lee et al. (1980) demon-
strated that young broilers fed corn-soymeal diets with 0.9
percent added magnesium had reduced growth and diarrhea.
Bones from these chicks had lesions similar to those of rick-
ets, and bone ash was greatly reduced. When dietary phos-
phorus was marginal to below normal, the addition of as
little as 0.3 percent magnesium to the basal diet also caused
rachitic lesions in bone, suggesting that magnesium supple-
mentation could interfere with dietary phosphorus use. The
study cautioned that dietary magnesium concentrations could
often reach levels of 0.4-0.7 percent if high magnesium lime-
stones were used in the diet or if the soybeans or corn used in
the ration originated from high magnesium soils.
Day-old Japanese quail (Coturnix coturnix japonica)
were fed 1 1 dietary levels of magnesium ranging from 125
to 2,000 mg/kg (0.0125-0.2 percent magnesium diets) using
magnesium sulfate as the source of magnesium added to
highly purified diets. Diets below 0.03 percent magnesium
were associated with magnesium deficiency signs including
poor growth, and occasional excitability, gasping, and con-
vulsions. The 0.2 percent diet did not affect growth of the
birds, though there was an unexplained increase in mortality
of the chicks in this group and was unlikely due to magne-
sium (Harland et al., 1976).
Inclusion of magnesium carbonate into laying hen rations
for 38 weeks at levels that raised total diet magnesium to
1.12 percent reduced egg production, and the hens had lower
BW at the end of the trial. When dolomitic limestone was
used as the source of magnesium, no effects on egg produc-
tion or shell strength were observed with diet magnesium as
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228
MINERAL TOLERANCE OF ANIMALS
high as 0.79 percent (Stillmak and Sunde, 1971). No adverse
effects were observed when diet magnesium was increased
to 0.77 percent in laying hens over a period of 7 weeks (Atteh
and Leeson, 1983). McWard (1967) found that diets that
were 1.9 percent magnesium supplied by magnesium sulfate
reduced egg production.
Swine have been fed 0.24 percent magnesium diets for
short periods of time immediately prior to slaughter to re-
duce fluid exudation by muscle postmortem, which enhances
carcass characteristics (Hamilton et al., 2002). Sows are of-
ten fed 1 percent magnesium sulfate (0.20 percent magne-
sium) before farrowing as a stool softener with no evidence
of toxicosis. There are no data that demonstrate a toxic level
of dietary magnesium in this species.
In tilapia, 0.32 percent dietary magnesium concentration
in a low (24 percent) protein diet caused signs of toxicosis.
At higher protein diets (44 percent), this level of magnesium
was not a problem (Dabrowska et al., 1989).
Guinea pigs fed diets that were 1.2 percent magnesium
suffered diarrhea, lethargy, reduced growth, and increased
mortality, especially if the dietary calcium to phosphorus
ratio was below 0.6:1 (Morris and O'Dell, 1963). If the cal-
cium to phosphorus ratio was greater than 1.5:1, there was
no ill effect of 1.2 percent magnesium diets.
Cats fed diets consisting of 0.5 percent magnesium were
found to have greater amounts of struvite stones in their blad-
der and urethra. In these studies, magnesium oxide was used
to increase dietary magnesium content (Lewis et al., 1978;
Kallfelz et al., 1980). Subsequent studies suggest that the
magnesium oxide may have acted as an alkalinizing agent
and that magnesium, in and of itself, was not the true cause
of the struvite stones. High pH urine, regardless of magne-
sium status, will cause struvite stones (Taton et al., 1984;
Buffington et al., 1990).
Horses often consume forages that are 0.5 percent mag-
nesium with no ill effects (Lloyd et al., 1987). Mature ponies
consuming diets that were 0.86 percent magnesium from
magnesium oxide for one month suffered no ill effects of the
diet (Hintz and Schryver, 1973).
Purified mouse diets supplemented with magnesium
chloride to achieve dietary levels of 0, 0.036, 0.072, 0.144,
0.288, or 0.575 percent magnesium were fed to mice for 13
weeks. The 0.575 percent magnesium diet caused a de-
crease in BW of the mice. This diet also contained 1.725
percent chloride, which may have affected feed intake as
much or more than the magnesium content of the diet. Ad-
verse clinical signs and hematological or blood biochemis-
try parameters were not evident in mice fed diets lower in
magnesium. Histopathologically, vacuolation of kidney tu-
bular cells was apparent in males of the 0.288 and 0.575
percent magnesium diet groups (Tanaka et al., 1994). How-
ever, it is possible that the observed lesions could have been
caused by the metabolic acidosis induced by the chloride
added to the diet. Thus, the study only demonstrated that
diets containing more than 2.5 percent MgCl,-6H20 can
exert toxic effects in mice. It may not be a good study to
assess magnesium toxicity.
Factors Influencing Toxicity
When animals with compromised renal function are fed a
diet that contains more magnesium than they require, they
are unable to excrete the excess absorbed magnesium as they
normally would. They are therefore at greater risk of devel-
oping hypermagnesemia and they can become lethargic.
Availability of water on an ad libitum basis will also permit
excretion of excess absorbed magnesium by the kidneys.
Adequate phosphorus in the diet can overcome some of the
deleterious effects that magnesium can have on bone forma-
tion, especially in poultry (Lee et al., 1980).
The source of magnesium in the diet can affect feed in-
take and if feed intake is reduced, growth and performance
will be reduced over a period of time. Magnesium oxide is
generally considered to be less detrimental to feed intake,
has less acidifying activity, and has less of a laxative effect
than magnesium sulfate and magnesium chloride. Magne-
sium oxide is also used in lower amounts since it is a highly
concentrated source of magnesium. The availability of the
magnesium, particularly from magnesium oxide, is also de-
pendent on the source and the particle size of the magnesium
supplement (Miller, 1979; Henry and Benz, 1995).
Elevated levels of fluoride in the diet can increase the
deposition of magnesium in bone tissues. This may weaken
the bone if diet magnesium levels are elevated along with
high dietary fluoride.
Magnesium can also act as an alkalinizing agent and is
often incorporated into ruminant diets as a means of raising
the pH of rumen fluid in animals fed high grain diets. Should
magnesium enter the plasma unaccompanied by an anion, it
could cause metabolic alkalosis in the animal (see chapter on
Minerals and Acid-Base Balance).
TISSUE LEVELS
Serum magnesium is typically between 0.75 and 1.11 mM
(18-27 mg/L) in most mammalian species (Table 18-2). Cere-
brospinal fluid (CSF) magnesium concentrations are gener-
ally slightly lower than the concentrations in plasma. In nor-
mal cows cerebrospinal fluid magnesium concentration is
0.9-1.0 mM. During hypomagnesemic tetany of cattle and
sheep, plasma and CSF magnesium concentrations are often
less than 0.45 and 0.5 mM, respectively (Bohman et al., 1983;
Puis, 1994). If the kidneys fail to excrete excess absorbed
magnesium rapidly enough, serum and then cerebrospinal
fluid magnesium concentrations can rise, inducing lethargy
and sedation in the animal. Sedation would begin to become
apparent once plasma magnesium concentration exceeded
1.6-2.0 mM (40-50 mg/L) (Mordes and Wacker, 1978). Diet
magnesium is an extremely rare cause of hypermagnesemia in
animals with fully functioning kidneys. Prolonged elevations
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MAGNESIUM
229
in dietary magnesium will increase bone magnesium deposi-
tion. Mammalian bone typically has 6-12 mg Mg/g ash (0.6-
1.2 percent magnesium in the ash). Poultry have bone ash that
is normally 0.5-0.8 percent magnesium. Under toxic condi-
tions, bone ash magnesium content in chicks was reported to
be as high as 1.50 percent (Lee et al., 1980). Magnesium con-
centration in horse muscle does not change during magnesium
deficiency (Stewart et al., 2004). However, in most species
liver and kidney magnesium concentrations increase with di-
etary magnesium, though levels rarely exceed 1,000 mg/kg
tissue DM (250 mg/kg wet weight) (Puis, 1994). Chester-
Jones et al. (1990) did an extensive study of the effect of high
dietary magnesium concentration on the magnesium content
of various tissues of steers fed the diets for 130 days. While
there was a significant linear effect of diet magnesium on tis-
sue magnesium content, the changes in magnesium content
were negligible, with the exception of bone. Bone magnesium
content nearly doubled with extremely high dietary magne-
sium: from 3.6 g/kg dry bone when fed a 0.3 percent magne-
sium diet to 6.4 g/kg dry bone in steers fed a 4.7 percent mag-
nesium diet (Table 18-3).
MAXIMUM TOLERABLE LEVELS
Single Oral Dose
The maximum tolerable single dose in ruminants is esti-
mated from the work of Care (1960) to be 0.12 g Mg/kg
BW. Higher amounts risk induction of diarrhea and
hypermagnesemia. In nonruminant species, where the effi-
ciency of absorption of magnesium is usually greater, the
maximum tolerable dose would be smaller. No data exist to
recommend an upper tolerable single oral dose in
nonruminant animals.
Acute
The absence of osmotic diarrhea is used as the criterion
for determining the level of dietary magnesium that can be
tolerated for short periods of time. Usually diets that are high
enough in magnesium to cause adverse effects in less than
10 days also result in a drastic decrease in feed intake. In
cattle, the work of Care (1960) demonstrates that diarrhea
rapidly occurs in cattle fed 1.15 percent magnesium diets,
but 0.76 percent diets were well tolerated for short periods.
Therefore, the acute tolerable dietary level of magnesium for
ruminants is set at 0.76 percent. No data exist with respect to
diets between 0.7 and 1.15 percent magnesium, which would
allow a more precise definition of the acute tolerable dietary
magnesium level.
Chronic
The criteria for determining the maximum tolerable dietary
magnesium concentration is considered to be the highest di-
etary magnesium level that can be fed without risk of detri-
mental effects on feed intake and growth or performance of
the animals. In cattle, reduced diet digestibility or diarrhea
has been observed only with diets that are greater than 1.15
percent magnesium. Dairy cattle have been fed diets that are
between 0.50 and 0.60 percent magnesium with no observ-
able adverse effects prior to parturition (Goff et al., 1991;
Oetzel et al., 199 1 ; Abu Damir et al., 1994) and during lacta-
tion (Jittakhot et al., 2004). Though detrimental effects of
high dietary magnesium have only been reported with diet
magnesium greater than 1 percent, no experimental data ex-
ist to extend the maximum tolerable dietary magnesium level
beyond 0.6 percent of the diet for ruminants. In the horse,
the maximum tolerable level is set at 0.8 percent magne-
sium, based on the work of Hintz and Schryyer (1973). In
broiler diets, provided there is adequate available phospho-
rus in the diet, the lowest magnesium level causing signifi-
cant adverse effects is 0.64 percent magnesium. The maxi-
mum tolerable level is therefore set at 0.5 percent
magnesium, based largely on the work of Chicco etal. (1967)
in which diets that were 0.51 percent magnesium were with-
out adverse effects. In laying hens, adverse effects on egg
production are not seen until diet magnesium is well above
0.79 percent. The maximum tolerable diet magnesium level
for laying hens is therefore set at 0.75 percent.
In most of the other nonruminant species of mammals,
studies to examine the tolerable limit for dietary magnesium
are not available. For example, the 1980 NRC Mineral Tol-
erance of Domestic Animals suggested that the maximum
tolerable level of magnesium for swine be set at 0.3 percent.
This limit is not based on any reported data. The highest
reported level of dietary magnesium safely fed to pigs was
0.24 percent and it was fed for just a short amount of time
(Hamilton et al., 2002). If there is water available and the
kidneys are functioning it is likely that no ill physiological
effects will be observed from magnesium ingestion at levels
higher than 0.24 percent, but there are no data to support a
dietary maximum tolerable magnesium level in this species.
Similarly, only one study examines the effect of dietary mag-
nesium on fish performance and this study is confounded by
dietary protein alterations at the same time. Dogs and cats
can commonly consume diets that are up to 0.2 percent mag-
nesium — well above their requirement. In cats some detri-
mental effects (uroliths) have been noted with high magne-
sium diets — but uroliths seem more highly dependent on
urine pH as opposed to dietary magnesium. There are no
studies of the effects of higher dietary magnesium levels in
dogs and cats upon which to base a maximum tolerable level.
Decreased palatability of the diet is a possibility with mag-
nesium supplementation, but no studies with any other spe-
cies have demonstrated any effect on feed intake with diets
that were less than 0.5 percent magnesium.
Magnesium in the digesta can complex with phytin phos-
phorus, rendering the complex insoluble and reducing the
availability of the phytate-bound phosphorus for absorption.
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230
MINERAL TOLERANCE OF ANIMALS
Complexing of magnesium with phiytin phiospliorus can oc-
cur at normal dietary magnesium levels. Therefore, feeding
more magnesium than is required will have some impact on
phosphorus use of nonruminant animals, but this effect was
not considered in setting the maximum tolerable limits for
magnesium.
FUTURE RESEARCH NEEDS
Few studies involve feeding diets with levels of magne-
sium that are above the required levels of magnesium in
swine. This could be of great importance if magnesium
supplementation just before slaughter proves a fruitful means
of enhancing pork quality, but only if it can be done without
other detrimental effects.
If farmed fish are to be fed large amounts of fish meal,
they could be receiving relatively high amounts of dietary
magnesium — fish meals are approximately 2.5-3 percent
magnesium on a DM basis. If there is a negative effect of
dietary magnesium on growth of fish, as suggested by
Dabrowska et al. (1989), this information could be of great
importance to the aquaculture industry.
SUMMARY
Magnesium is a relatively nontoxic mineral. Very high
amounts can be fed to animals with no ill effects if the kid-
neys are functioning. Inappetance is the major practical prob-
lem encountered from excessive dietary magnesium. Be-
cause only a fraction of dietary magnesium is generally
absorbed, high amounts of magnesium in the diet can cause
an osmotic diarrhea in the animal. This is usually of greater
concern in poultry houses where the water content of ma-
nure can be a major concern to producers but does not neces-
sarily impact the health of the birds.
REFERENCES
Abu Damir, H., M. Phillippo, B. H. Thorp, J. S. Milne, L. Dick, and I. M.
Nevison. 1994. Effects of dietary acidity on calcium balance and
mobilisation, bone morphology, and 1 ,25 dihydroxy vitamin D in prepar-
tal dairy cows. Res. Vet. Sci. 56:310-318.
Adam, C. L., R. G. Hemingway, and N. S. Ritchie. 1996. Influence of manu-
facturing conditions on the bioavailability of magnesium in calcined
magnesites measured in vivo and in vitro. J. Agric. Sci. 127:377-386.
Andrews, B. F., D. R. Campbell, and P. Thomas. 1965. Effects of hyper-
tonic magnesium sulphate enemas on newborn and young lambs. Lan-
cet 3:64-68.
Atteh, J. O., and S. Leeson. 1983. Influence of increasing dietary calcium
and magnesium levels on performance, mineral metabolism, and egg
mineral content of laying hens. Poult. Sci. 62:1261-1268.
Bacon, J. A., M. C. Bell, J. K. Miller, N. Ramsey, F. J. Mueller. 1990. Effect
of magnesium administration route on plasma minerals in Holstein
calves receiving either adequate or insufficient magnesium in their di-
ets. J. Dairy Sci. 73:470-473.
Bohman, V. R., F. P. Horn, E. T. Littledii^e, J. G. Hurst, and D. Griffin.
1983. Wheat pasture poisoning. II. Tissue composition of cattle grazing
cereal forages and related to tetany. J. Anim. Sci. 57:1364—1373.
Bowen, J. M.,D. M. Blackburn, and J. E. Heavener. 1970.Effect of magne-
sium ions on neuromuscular transmission in the horse, steer, and dog. J.
Am. Vet. Med. Assoc. 157:164-171.
Buffington, C. A., Q. R. Rogers, and J. G. Morris. 1990. Effect of diet on
struvite activity product in feline urine. Am. J. Vet. Res. 5 1 :2025-2030.
Care, A. D. 1960. The effect on cattle of high-level magnesium supplemen-
tation of their diet. Vet. Rec. 72:517-519.
Chester- Jones, H., J. P. Fontenot, and H. P. Veit. 1990. Physiological and
pathological effects of feeding high levels of magnesium to steers. J.
Anim. Sci. 68:4400-4413.
Chicco, C. F., C. B. Ammerman, P. A. Wallegham, P. G. Waldroup, and R.
H. Harms. 1967. Effects of varying dietary ratios of magnesium, cal-
cium, and phosphorus in growing chicks. Poult. Sci. 46:368-373.
Cragle, R. G. 1973. Dynamics of mineral elements in the digestive tract of
ruminants. Fed. Proc. 32:1910-1914.
Dabrowska, H., K. D. Gunther, and K. Meyer-Burgdorff. 1989. Interaction
between dietary protein and magnesium level in tilapia (Oreochromis
niloticus). Aquaculture 76:277—291.
de Schamphelaere, K. A., and C. R. Janssen. 2002. A biotic ligand model
predicting acute copper toxicity for Daphnia magna: the effects of cal-
cium, magnesium, sodium, potassium, and pH. Environ. Sci. Technol.
36:48-54.
Douglas, W. S., S. S. Grasso, D. G. Hutton, and K. R. Schroeder. 1996.
Ionic imbalance as a source of toxicity in an estuarine effluent. Arch.
Environ. Contam. Toxicol. 31:426^32.
EPA (U.S. Environmental Protection Agency). 1983. Magnesium: Method
242.1 (atomic absorption, direct aspiration). Pp. 242.1-1—242.1-2 in
Methods for Chemical Analysis of Water and Wastes, EPA-600/4-79-
020. Cincinnati, OH: EPA.
Fassler, C. A., R. M. Rodriguez, D. B. Badesch, W. J. Stone, and J. J.
Marini. 1985. Magnesium toxicity as a cause of hypotension and
hypoventilation. Occurrence in patients with normal renal function.
Arch. Intern. Med. 145:1604-1606.
Gatlin, D. M. 3rd, E. H. Robinson, W. E. Poe, and R. P. Wilson. 1982.
Magnesium requirement of fingerling channel catfish and signs of mag-
nesium deficiency. J. Nutr. 112:1182-1189.
Gentry, R. P., W. J. Miller, D. G. Pugh, M. W. Neathery, and J. B. Bynum.
1978. Effects of feeding high magnesium to young dairy calves. J. Dairy
Sci. 61:1750-1754.
Goff J. P., R. L. Horst, F. J. Mueller, J. K. Miller, G. A. Kiess, and H. H.
Dowlen. 1991. Addition of chloride to a prepartal diet high in cations
increases 1 ,25-dihydroxy vitamin D response to hypocalcemia prevent-
ing milk fever. J. Dairy Sci. 74:3863-3871.
Greene, L. W., K. E. Webb, Jr., and J. P. Fontenot. 1983. Effect of potas-
sium level on site of absorption of magnesium and other macroelements
in sheep. J. Anim. Sci. 56:1214-1221.
Hamilton, D. N., M. Ellis, M. D. Hermann, F. K. McKeith, K. D. Miller,
and K. W. Purser. 2002. The impact of longissimus glycolytic potential
and short-term feeding of magnesium sulfate heptahydrate prior to
slaughter on carcass characteristics and pork quality. J. Anim. Sci.
80:1586-1592.
Harland, B. F., M. R. Fox, and B. E. Fry, Jr. 1976. Magnesium deficiency,
requirement, and toxicity in the young Japanese quail. Poult. Sci.
55:359-364.
Henninger, R. W., and J. Horst. 1997. Magnesium toxicosis in two horses.
J. Am. Vet. Med. Assoc. 211:82-85.
Henry, P. R., and S. A. Benz. 1995. Magnesium bioavailability. In
Bioavailability of Nutrients for Animals, C. B. Ammerman, D. H. Baker
and A. J. Lewis, eds. San Diego: Academic Press.
Hintz, H. F., andH. F. Schryver. 1973. Magnesium, calcium, and phospho-
rus metabolism in ponies fed varying levels of magnesium. J. Anim.
Sci. 37:927-930.
Jittakhot, S., J. T. Schonewille, H. Wouterse, E. J. Focker, C. Yuangklang
and A. C. Beynen. 2004. Effect of high magnesium intake on apparent
magnesium absorption in lactating cows. Anim. Feed Sci. Tech.
113:53-60.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
MAGNESIUM
231
Kallfelz, F., J. Bressett, and R. Wallace. 1980. Urethral obstruction in
random source and SPF male cats induced by high levels of dietary
magnesium or magnesium and phosphorus. Feline Prac. 10:25-35.
Kramer, J. H., I. T. Mak, T. M. Phillips, and W. B. Weglicki. 2003. Dietary
magnesium intake influences circulating pro-inflammatoi-y neuropep-
tide levels and loss of myocardial tolerance to postischemic stress. Exp.
Biol. Med. 228:665-673.
Lee, S. R., W. M. Britton, and G. N. Rowland. 1980. Magnesium toxicity:
bone lesions. Pouh. Sci. 59:2403-2411.
Lewis, L. D., F. H. Chow, G. F. Taton, and D. W. Hamar. 1978. Effect of
various dietary mineral concentrations on the occurrence of feline uroli-
thiasis. J. Am. Vet. Med. Assoc. 172:559-563.
Littledike, E. T., and J. Goff. 1987. Interactions of calcium, phosphorus,
magnesium, and vitamin D that influence their status in domestic meat
animals. J. Anim. Sci. 65:1727-1743.
Lloyd, K., H. F. Hintz, J. D. Wheat, and H. F. Schry ver. 1987. Enteroliths in
horses. Cornell Vet. 77:172-186.
Martens, H., and M. Schweigel. 2000. Pathophysiology of grass tetany and
other hypomagnesemias. Implications for clinical management. Vet.
CUn. North Am. Food Anim. Pract. 16:339-368.
McWard, G. W. 1967. Magnesium tolerance of the growing and laying
chicken. Br. Pouh. Sci. 8:91-97.
Michibata, H., S. Sahara, M. K. Kojima. 1986. Effects of calcium and mag-
nesium ions on the toxicity of cadmium to the egg of the teleost, Oryzias
latipes. Environ. Res. 40:110-114.
Miller, W. J. 1979. Mineral and trace element nutrition of dairy cattle. P.
120 in Dairy Cattle Feeding and Nutrition, W. J. Miller, ed. New York:
Academic Press.
Mordes, J. P., and E. C. Wacker. 1978. Excess magnesium. Pharmacol.
Rev. 29:274-300.
Morris, E. R., and B. L. O'Dell, 1963. Relationship of excess calcium and
phosphorus to magnesium requirement and toxicity in guinea pigs. J.
Nutr. 81:175-181.
NRC (National Research Council). 1994. Nutrient Requirements of Poul-
try: 9th rev. ed. Washington, D.C.: National Academy Press.
NRC. 1998. Nutrient Requirements of Swine, 10th rev. ed. Washington,
D.C.: National Academy Press.
NRC. 2006. Nutrient Requirements of Dogs and Cats. Washington, D.C.:
The National Academies Press.
Nielsen, F. H., T. R. Shuler, T. J. Zimmerman, and E. O. Uthus. 1988.
Dietary magnesium, manganese, and boron affect the response of rats to
high dietary aluminum. Magnesium 7:133-147.
Nugara, D., and H. M. Edwards. 1963. Influence of dietary Ca and P levels
on the Mg requirement of the chick. J. Nutr. 80:181-184.
Oetzel, G. R., M. J. Fettman, D. W. Hamar, and J. D. Olson. 1991. Screen-
ing of anionic salts for palatability, effects on acid-base status, and uri-
nary calcium excretion in dairy cows. J. Dairy Sci. 74:965-971.
Petersson, K. H., R. G. Warner, F. A. Kallfelz, and C. F. Crosetti. 1988.
Influence of magnesium, water, and sodium chloride on urolithiasis in
veal calves. J. Dairy Sci. 71:3369-3377.
Pierce, A. W. 1959. Studies on salt tolerance of sheep. II. The tolerance of
sheep for mixtures of sodium chloride and magnesium chloride in the
drinking water. Aust. J. Agric. Res. 10:725-733.
Puis, R. 1994. Mineral Levels in Animal Health: Diagnostic Data, 2nd ed.
Clearbrook, B.C., Canada: Sherpa International.
Rude, R. K., S. B. Oldham, C. F. Sharp, Jr., and F. R. Singer. 1978. Parathy-
roid hormone secretion in magnesium deficiency. J. Clin. Endocrinol.
Metab. 47:800-806.
Schwartz, M. L., and R. C. Playle. 2001. Adding magnesium to the silver-
gill binding model for rainbow trout (Oncorhynchus mykiss). Environ.
Toxicol. Chem. 20:467-472.
Stewart, A. J., J. Hardy, C. W. Kohn, R. E. Toribio, K. W. Hinchcliff, and
B. Silver. 2004. Validation of diagnostic tests for determination of mag-
nesium status in horses with reduced magnesium intake. Am. J. Vet.
Res. 65:422-430.
Stillmak, S. J., and M. L. Sunde. 1971. The use of high magnesium lime-
stone in the diet of the laying hen. Poult. Sci. 50:553.
Tanaka, H., A. Hagiwara, Y. Kurata, T. Ogiso, M. Futakuchi, and N. Ito.
1994. Thirteen-week oral toxicity study of magnesium chloride in
B6C3F1 mice. Toxicol. Lett. 73:25-32.
Taton, G. F., D. W. Hamar, and L. D. Lewis. 1984. Urinary acidification in
the prevention and treatment of feline struvite urolithiasis. J. Am. Vet.
Med. Assoc. 184:437^143.
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234
MINERAL TOLERANCE OF ANIMALS
TABLE 18-2 Magnesium Concentrations in Fluids and Tissues of Animals (mg/kg or mg/L)"
Animal
Serum
(mg/L)
Muscle
(mg/kg)
Liver
(mg/kg)
Kidney
(mg/kg)
Bone
(mg/g ash)
Milk (mg/L) or Egg
(mg/g eggshell)
Broiler
chickens
16-36
600-2,000
600-2,000
800-2,000
5-8
Laying hens
16-36
600-2,000
800-2,000
5.3-6.4
Pigs ^^^1
P 19-33 1
^^^^V^9
600-800
560-720
5.8-7.5
^^^1
Cows
18-24
600-1,000
400-1,000
200-800
6-12
100-140
Sheep ^^
_ 19-30
800-1,000
440-800
440-920
4-8
^
Fish*
Meal with bone
25-31 g/kg DM
"Data largely adapted from Puis, 1994.
''Menhaden or anchovy fish meal fed to livestock.
TABLE 18-3 Tissue Magnesium Concentrations in Steers Fed Different Dietary Levels of Magnesium (mg/kg)'
a.b
Tissue
0.3%
Dietary
Mg
1.4%
Dietary
Mg
2.5%
Dietary
Mg
4.7% Dietary Mg
Liver
540
560
570
650
Kidney
690
730
890
970
Heart
940
^ 880
J
H 920
1 900
1
Rib- bone
3,620
4,330
5,750
6,430
Skeletal muscle
750
770
■
^^
800
800
"Adapted from Chester- Jones et al., 1990.
''Data are on a dry matter basis.
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19
Manganese
INTRODUCTION
Manganese (Mn) has an atomic number of 25 and has two
oxidation states: Mn (0) and Mn+^. It does not occur natu-
rally as a metal but as a component of over 100 minerals
(ATSDR, 2000).
The United States has used an estimated 700,000 tons of
manganese per year since 1994 (Goonan and Jones, 2003).
Between 85-90 percent of the demand for manganese in the
United States is for steelmaking because of its sulfur-fixing,
deoxidizing, and alloying properties (Corathers, 2001). Man-
ganese is a component of certain aluminum alloys, particu-
larly those used in the manufacture of soft drink cans, be-
cause it increases corrosion resistance. Inorganic manganese
is also used in dry cell batteries, animal feed, brick coloring,
and fertilizers (Corathers, 2001).
There are three forms of organic manganese that are of toxico-
logical interest to humans. Methylcyclopentadienyl manganese
tricarbonyl (MMT) replaced lead compounds as a fuel additive
that improves the antiknock properties of fuels (Kaiser, 2003).
Maneb (ethylenebisdithiocarbamate manganese) and Mancozeb
(a mixture of substances that contain manganese, zinc, and
dothiocarbamates) are plant fungicides (ATSDR, 2000).
ESSENTIALITY
Manganese is an essential element (Hurley and Keen,
1987; NRC, 1995, 2001; Klein, 2002). The estimated man-
ganese requirement for maintenance, growth, and reproduc-
tion in rodents (rats and mice) is 10 mg/kg diet of manganese
and for guinea pigs is 40 mg/kg diet of manganese (NRC,
1995). The estimated manganese requirements of growing
pigs weighing more than 20 kg is 20 mg/kg diet of manga-
nese (NRC, 1998); of immature leghorn chickens chicks
older than 6 weeks is 28 or 30 mg/kg diet of manganese
(NRC, 1994); of growing and finishing beef cattle is 20 mg/
kg diet of manganese (NRC, 2000); and of dairy cattle is 40
mg/kg diet of manganese (NRC, 2001).
Manganese deficiency has occurred naturally in cattle,
pigs, and poultry fed practical diets. The signs of manganese
deficiency include abnormal bone formation (called perosis
in chickens), abnormalities in carbohydrate and lipid me-
tabolism, growth retardation, dermatitis, and reproductive
failure. The primary enzymes that have been demonstrated
to be sensitive to dietary deficiency of manganese are the
glycosyltransferases and xylosyltransferases (manganese-
activated enzymes involved in proteoglycan synthesis and
hence bone formation), as well as arginase and mitochon-
drial superoxide dismutase (manganese metalloenzymes).
DIFFICULTY IN METHODS OF ANALYSIS AND
EVALUATION
Determination of manganese in biological samples usu-
ally requires digestion of the organic matrix (generally by an
oxidizing acid mixture) prior to analysis (ATSDR, 2000).
Analyses are performed by flame atomic absorption (most
commonly), furnace atomic absorption (when very low lev-
els of manganese are present, as in plasma and urine), ICP-
ES (for multi-mineral analyses), or neutron activation analy-
sis (when very low amounts of manganese are present). None
of the methods distinguish between different oxidation states
of manganese.
Organic forms of manganese (i.e., MMT) are present in
toxicological and environmental samples at very low levels
(ng/g) and require a combination of techniques (i.e., gas or
liquid chromatography with atomic absorption spectrometry)
(ATSDR, 2000).
REGULATION AND METABOLISM
Absorption
The gut is the primary organ preventing excess manga-
nese accumulation in the body when excess manganese is
ingested (Hurley and Keen, 1987; Davis et al., 1993;
235
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236
MINERAL TOLERANCE OF ANIMALS
Andersen et al., 1999; ATSDR, 2000). Apparent absorption
of orally administered ^"^Mn has been estimated to range from
1-5 percent in rats, humans, and livestock (Hurley and Keen,
1987; Davis et al., 1993). However, excretion of absorbed
manganese in the bile occurs very rapidly (i.e., as soon as 1
hour after ingestion) (Malecki et al., 1996). Thus, in most
studies manganese excreted in the bile was part of the man-
ganese measured in the feces and assumed to be
nonabsorbed. True absorption of manganese has been esti-
mated to be 8 percent in young rats (Davis et al., 1993).
Manganese absorption is inversely related to dietary lev-
els of manganese (Abrams et al., 1976). Absorption of man-
ganese appears to occur by a low capacity saturable process
(Garcia-Aranda et al., 1983) and by diffusion (ATSDR,
2000). Uptake and retention of dietary manganese was found
to be greater in the suckling than postweaning stage in rats
(Keen et al., 1986).
A variety of dietary factors affect apparent absorption of
manganese. These factors include iron, calcium, phospho-
rus, phytate, and amino acids. These interactions will be dis-
cussed in the "Bioavailability" section below, because in-
vestigators generally measure tissue retention of manganese
or ^"^Mn, not apparent absorption of manganese, and rarely
true absorption of manganese.
Inhalation
Inhaled manganese can be classified as respirable (gener-
ally dust particles of <5 microns) and as total dust (ATSDR,
2000). The respirable dust enters the bronchioles and alveoli,
and the manganese is absorbed rapidly into the blood stream
(Andersen et al., 1999). The total dust does not travel deeply
into the lungs and is coughed up and swallowed (ATSDR,
2000). The percentage of this inhaled manganese that is ab-
sorbed in the gut is unknown.
Although there are very few data in animals, it is assumed
that inhaled manganese is not a major source of manganese
accumulation in the tissues of livestock. However, Bench et
al. (2001) found that California ground squirrels took up
measurable amounts of manganese from the soil by the ol-
factory pathway. Tjalve and Henriksson (1999) hypothesized
that inhaled manganese taken up via the olfactory pathways
was passed transneuronally to other parts of the brain.
Transport
Manganese absorbed in the gut is transported by a 2-mac-
roglobulins and albumin to the liver (Andersen et al., 1999).
Davis et al. (1993) demonstrated that intraportally adminis-
tered ^"^Mn complexed to albumin (but not as free ^'*Mn or
^■^Mn complexed to transferrin) distributed in tissues, as did
orally administered ^"^Mn. This protein-bound manganese is
efficiently cleared in the liver (Andersen et al., 1999).
Manganese leaving the liver is bound to transferrin. In-
haled and injected manganese is transported by transferrin
(Hurley and Keen, 1987). Hypotransferrinemic mice (pro-
duce <1 percent of normal transferrin levels) have been
found to accumulate extra manganese in their livers but ac-
cumulate less manganese in other tissues (Dickinson et al.,
1996). This suggests that alternatives to transferrin exist.
However, transferrin is believed to be the primary transporter
of manganese across the blood-brain barrier (Aschner et al.,
1999).
Urinary Excretion
Urinary excretion of manganese does not appear to be
sensitive to dietary intake and is a minor route of excre-
tion of manganese (Freeland-Graves et al., 1988; Greger
et al., 1990; Davis and Greger, 1992). Adult human fe-
males excreted about 1 1 nmoles/day of manganese (0.01
|ig/kg BW/day of manganese) whether intake was 1.7 or
16.7 mg manganese daily (Davis and Greger, 1992; Davis
et al., 1992).
Biliary Secretion
Bile is the major excretory route of injected manganese
(Bertinchamps et al., 1966; Klaassen 1974; Thompson and
Klaassen, 1982; Ballatori et al., 1987). Rats excreted 15-40
percent (Ballatori et al., 1987) and calves excreted 21 per-
cent (Abrams et al., 1977) of injected doses of manganese in
bile. Klaassen (1974) observed that rats secreted proportion-
ately more manganese into bile than rabbits and dogs.
Bile is also the major excretory route of ingested manga-
nese, but the effectiveness of the gut in preventing excess
absorption blunts the effect of biliary secretion (Abrams et
al., 1977; Davis et al., 1993; Malecki et al., 1996). Using an
isotope-based model system, Davis et al. (1993) estimated
that growing rats lost 37 percent of their absorbed manga-
nese (2.8 percent of their total manganese intake when true
absorption was 8.2 percent) through biliary secretion.
Malecki et al. (1996) observed that biliary secretion of man-
ganese immediately after an oral dose was proportional to
the amount of manganese given and that biliary secretion of
manganese by fasted rats was proportional to chronic dietary
manganese intakes. Hence, the biliary secretion of manga-
nese during a 4-hour collection period immediately after an
acute dose accounted for 3.4 percent of the dose, and the
biliary secretion of manganese during a 4-hour collection
period by fasted rats accounted for 0.2 percent of their previ-
ous day's intake. Calves excreted 0.2 percent of a duodenal
dose of manganese into bile in one study (Abrams et al.,
1977) and 2.1-3.6 percent of high levels of manganese in-
fused intraduodenally in another study (Symonds and Hall,
1983).
Thus, there are several mechanisms that account for the
huge difference in toxicity of inhaled and ingested manga-
nese. Absorption of manganese is lower in the gut than in the
lungs. Absorbed manganese is transported by macroglobu-
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MANGANESE
237
lins and albumin to the liver, where these manganese com-
plexes are rapidly cleared and the manganese is excreted in
bile. Transferrin receptors determine the location of manga-
nese deposition in the brain under normal conditions.
SOURCES AND BIOAVAILABILITY
Diet
Diet is the major source of ingested manganese for hu-
mans and presumably livestock (EPA, 2004). Vegetable
products (grain products, tea, and vegetables) contribute al-
most 75 percent of the manganese consumed by the average
adult human male in the Total Diet Study (Pennington and
Young, 1991). Similarly, unrefined grains and forages are
the primary natural sources of manganese for livestock
(Schroeder et al., 1966; Hurley and Keen, 1987).
The concentration of manganese in forages can vary by
10-fold with the species of plant, type of soil, and soil treat-
ment. Diets for poultry based on corn (sometimes sorghum
and barley) are deficient in manganese unless supplemented
with it (typically through addition of manganese salts or
manganese-rich ingredients such as wheat bran or middlings
to the diet) (Hurley and Keen, 1987).
Water
The median manganese level in surface water studied in
the National Ambient Water Quality Assessment was 16 |ig/
L of manganese, but 1 percent of samples had concentration
of 400-800 mg/L of manganese (EPA, 2004). Higher levels
of manganese were usually associated with industrial pollu-
tion. However, manganese in water can also reflect erosion
of soils that can contain 2 to 7,000 ^Ig/g soil of manganese
(EPA, 2004).
Generally water is a minor source of ingested manganese.
If cattle consume water containing 3 mg/L of manganese, the
previous NRC report (1980) estimated that the cattle could
consume 3 to 6 times their requirement for manganese. How-
ever, water with such a concentration of manganese would be
discolored and would be less palatable to livestock (Personal
communication, Linn and Raeth-Knight, 2004).
manganese levels in areas with and without use of MMT in
gasoline.
Bioavailability
The bioavailability of manganese varies greatly with natu-
ral diets. Manganese was more available to chicks fed casein-
based versus soy-based diets (Halpin et al., 1986). The addi-
tion of fishmeal to manganese-deficient diets worsened the
signs in chicks more than the addition of wheat bran (Halpin
and Baker, 1986). Uptake of manganese was greater among
14-day-old rats fed cow or human milk rather than soy for-
mula (Keen et al., 1986).
These effects could reflect differences in the phytate or
amino acid content of the diets. Phytate has inconsistently
been found to decrease manganese absorption and retention
(Davies and Nightingale, 1975; Lee and Johnson, 1989). The
presence of cysteine and histidine (Garcia-Aranda et al.,
1983) and lactose (Dupuis et al., 1992) in the gut has been
found to enhance uptake of manganese. Henry (1995) esti-
mated the relative bioavailability of manganese to poultry
was 1.2 times as great from manganese methionine and 1.1
times as great from manganese proteinate as from manga-
nese sulfate or manganous chloride. In sheep, manganese
methionine was 1.25 times as bioavailable as manganese
sulfate (Henry, 1995).
The relative bioavailability of supplemental forms of
manganese differed in some studies. Ammerman and Miller
(1972) observed that the manganese salts included in diets
did not affect bioavailability of manganese to chicks. How-
ever, Southern and Baker (1983) observed that chicks fed
excess supplemental manganese were more sensitive to man-
ganese chloride, carbonate, and sulfate than manganese ox-
ide. Henry (1995) estimated the relative bioavailability of
manganese to poultry was 0.55 from manganese carbonate,
0.30 from manganese dioxide, and 0.75 from manganese
monoxide when the bioavailability of manganese from man-
ganese sulfate and manganese chloride was considered to be
1 . Manganese from manganese carbonate, dioxide, and mon-
oxide (relative bioavailabilities were 0.3, 0.35, and 0.6, re-
spectively) was even less bioavailable to sheep than manga-
nese sulfate (relative bioavailability was 1) (Henry, 1995).
Air
Industries (primarily manganese mines and to a lesser
extent battery plants, ferroalloy production facilities, coke
ovens, and power plants) are the major sources of manga-
nese dust in the air (ATSDR, 2000; Hudnell, 1999). Air levels
of manganese vary with the proximity of industrial sources.
Average ambient manganese levels have been reported near
industrial sources to range from 220 to 330 ng/m^ of manga-
nese and in urban and rural areas without industrial sources
to range from 10 to 70 ng/m"* of manganese (EPA, 2004).
Lynam et al. (1999) reported little difference in ambient
Calcium and Phosphorus
Two of the dietary factors most often studied in regard to
manganese bioavailability for livestock are calcium and
phosphorus (Hurley and Keen, 1987). High levels of both
dietary calcium and phosphorus have been found to increase
the severity of signs of manganese deficiency in dairy calves
(Hawkins et al., 1955), in chickens (Wilgus and Patton,
1939), and in rats (Wachtel et al., 1943).
However, high levels of calcium and phosphorus did not
decrease tissue manganese levels in pigs (Kayongo-Male et
al., 1977) or decrease apparent absorption of manganese in
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238
MINERAL TOLERANCE OF ANIMALS
humans (Greger et al., 1981). Wedekind et al. (1991) dem-
onstrated that the addition of graded levels of calcium as
feed-grade limestone did not affect true absorption of man-
ganese by chickens but addition of graded levels of phos-
phorus as dicalcium phosphate did. Dupuis et al. (1992) ob-
served that the addition of calcium to gut infusates negated
the enhancing effect of lactose on manganese absorption.
Together these data suggest that the effect of calcium and
phosphorus on manganese absorption reflects not only the
relative and absolute amounts of calcium, phosphorus, and
manganese fed, but also the levels of other dietary factors.
Iron
In iron-deficient rats, intestinal absorption of manganese
vi'as increased (Thomson et al., 1971; Flanagan et al., 1980)
and liver manganese levels were increased (Shukla et al.,
1990). Mena (1981) found that anemic and normal human
subjects absorbed 7.5 percent and 3.0 percent, respectively,
of ingested manganese.
The effect of iron supplementation above required
amounts is less clear. Iron supplementation did not affect
tissue manganese concentrations in calves (Ho et al., 1984),
lambs (Prabowo et al., 1988), or chicks (Baker and Halpin,
1991), but decreased tissue manganese concentrations in
mice (Hurley et al., 1983), sheep (Ivan and Hidiroglou,
1980), and rats (Davis et al., 1990) and decreased manga-
nese transfer through the gut of rats (Gruden, 1977). In hu-
mans, inorganic iron supplementation increased fecal man-
ganese losses (Kies et al., 1987) and decreased serum
manganese concentrations after 60 days and lymphocyte
manganese-dependent superoxide dismutase (Mn-SOD) ac-
tivity after 124 days (Davis and Greger, 1992). Heme iron
intake had no consistent effect on serum manganese or lym-
phocyte Mn-SOD activity (Davis et al., 1993).
TOXICOSIS
There are no practically important studies reporting the
toxic effects of a single oral dose of manganese in mammals
(ATSDR, 2000). Thus, all toxicity studies reported here are
chronic in nature (Table 19-1).
Chronic Dietary Exposure to Inorganic IVIanganese
Manganese is considered to be one of the least toxic of
the essential elements (NRG, 1980; Hurley and Keen, 1987).
Decreased growth was not observed until 500 and >2,000
mg/kg diet of manganese was consumed by swine (Grummer
et al., 1950; Leibholz et al., 1962, respectively); 1,000 and
>2,000 mg/kg diet of manganese was consumed by calves
(Jenkins and Hidiroglou, 1991; Cunningham et al., 1966,
respectively); 3,000 mg/kg diet of manganese was consumed
by sheep (Ivan and Hidiroglou, 1980); >3,000 mg Mn/kg
diet of manganese was consumed by chickens (Heller and
Penquite, 1937; Southern and Baker, 1983; Black et al.,
1985b); > 4,000 mg/kg diet of manganese was consumed by
turkeys (Vohra and Kratzer, 1968); and > 7,000 mg/kg diet
of manganese was consumed by rats (Becker and McCoUum,
1938; Moinuddin and Lee, 1960).
These data suggest that swine were more sensitive to ex-
cess manganese than other livestock. However, differences
in the composition of the diets, water sources, and other study
conditions could create these apparent differences among
species.
Generally, depressed iron status and hematological
changes were the most common signs of manganese toxico-
sis, even in animals fed typically adequate levels of iron.
Cattle consuming 1,000 mg/kg diet of manganese had de-
creased iron-binding capacity in serum (Ho et al., 1984), and
cattle consuming 3,000 mg/kg diet of manganese had de-
pressed hemoglobin levels (Cunningham et al., 1966).
Preruminant calves were more sensitive to manganese;
calves fed only 500 mg/kg of manganese in milk replacer
developed low hematocrits (Jenkins and Hidiroglou, 1991).
Sheep consuming 2,550 to 5,000 mg/kg diet of manganese
had depressed tissue iron and hemoglobin levels (Hartman
et al., 1955; Watson et al., 1973). Chickens consuming 3,000
mg/kg diet of manganese had depressed tissue iron concen-
trations (Southern and Baker, 1983; Black et al., 1985b).
Rats consuming >3,550 mg/kg diet of manganese had de-
pressed tissue iron concentrations and depressed hemoglo-
bin levels and red blood cell counts (RBCs) (Becker and
McCollum, 1938; Moinuddin and Lee, 1960; Carter et al.,
1980; Rehnberg et al., 1982). Fish exposed to 2,500 mg/L
water of MnS04 had decreased erythrocyte counts (Agrawal
and Srivastava, 1980) and those exposed to 50 mg/L of man-
ganese had transient decreases in hematocrits (Cossarini-
Dunieretal., 1988).
Some of the differences in sensitivity of animals to the
hematological effects of excess manganese reflect the iron
content of the diets. Repeatedly, investigators have demon-
strated that animals fed low levels of iron were more sensi-
tive (as judged by hematological status) to excess manga-
nese, i.e., 45 mg/kg diet of manganese in sheep (Hartman et
al., 1955), 1,000 mg/kg of manganese in chickens (Baker
and Halpin, 1991), and 400 mg/kg of manganese in rats
(Rehnberg et al., 1982). Matrone et al. (1959) found that a
supplement of 400 mg/kg diet of iron would overcome the
effects of 2,000 mg/kg diet of manganese on hemoglobin
formation in pigs.
To a lesser extent, manganese may interact with other
trace elements. Occasionally depressed liver zinc and el-
evated liver copper concentrations (Hartman et al., 1955;
Watson et al., 1973; Ivan and Hidiroglou, 1980; Black et al.,
1985b) and depressed copper absorption (Ivan and Grieve,
1976) were observed in animals exposed to excess manga-
nese. Excess manganese intake has also been found to coun-
teract excess intake of cobalt and decrease tissue retention of
excess cobalt (Brown and Southern, 1985). Some of these
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MANGANESE
239
changes could partially reflect changes in iron status induced
by excess manganese.
Several groups noted depressed calcium and/or phospho-
rus utihzation in cattle (Reid et al., 1947; Gallup et al., 1952)
and depressed serum phosphorus levels among rats
(Moinuddin and Lee, 1960) fed excess manganese.
Two groups have noted a potential link between man-
ganese and magnesium. Swine fed excess manganese and
low levels of magnesium had depressed heart magnesium
concentrations (Miller et al., 2000). Fain et al. (1952) ob-
served that cattle fed excess manganese had transient de-
pression of serum magnesium levels. Miller et al. (2000)
suggested that excess manganese in diets might be a con-
tributing factor to convulsions among livestock fed insuf-
ficient magnesium.
Exposure to Inorganic Manganese in Water
Limited studies with fish suggest that fish are more sensi-
tive to excess manganese than mammals and birds. The LCjq
for teleost in freshwater was 2,850 mg/L water of MnS04
(Agrawal and Srivastava, 1980), but the LCjq for the fry of
Lates calcarifer in brackish water was 2.2 to 2.5 mg/L of
manganese (Krishnani et al., 2003) after only 90 hours of
exposure. Low levels of manganese reduced hematocrits (50
mg/L of manganese: Cossarini-Dunier et al., 1988) and in-
duced cataracts (198 mg/kg diet of manganese: Waagbo et
al., 2003) in fish.
The sensitivity of fish to manganese may reflect species
differences. However, mammals "appear" to be more sensi-
tive to manganese in water rather than the dietary milieu.
Chandra and Imam (1973) found gavage doses of manga-
nese were fatal to guinea pigs or caused gut necrosis.
Rehnberg et al. administered excess Mn304 to rats by diet
(1982) and by a gavage solution (1981). The rats accumu-
lated similar concentrations of manganese in their livers and
kidneys but accumulated more manganese in their cerebrums
when the manganese was administered by gavage solution.
Umarji et al. (1969) observed neurological signs in rabbits
given excess manganese in their drinking water.
Kondakis et al. (1989) observed more neurological signs
in long-term (>10 years) residents who were older than age
50 in regions of Greece in which the drinking water con-
tained 1 .8 to 2.3 mg Mn/L. Unfortunately dietary manganese
was not assessed in this study and another epidemiological
study did not confirm human sensitivity to manganese in
water (Vieregge et al., 1995). The observation of Kondakis
et al. (1989) led the EPA to suggest the LOAEL for manga-
nese in water for humans was 4.2 mg/day of manganese or
0.06 mg/kg BW of manganese (Velasquez and Du, 1994).
The standard was problematic because it was lower than rec-
ommended dietary levels (Greger, 1998) and is now judged
inappropriate (EPA, 2004).
The Agency for Toxic Substances and Disease Registry
(ATSDR, 2000) found no reports of adverse effects in live-
stock due to exposure to manganese in water. Unpublished
data indicate that calves provided with water containing 0.75
mg/L of manganese did not have reduced water or feed in-
take or decreased growth (Personal communication, Linn
and Raeth-Knight, 2004).
Inlialation Exposure to Inorganic IVIanganese
Chronic exposure to inhaled manganese (usually but not
exclusively MnOj) causes a disabling neurological syndrome
called manganism in humans (ATSDR, 2000). The clinical
symptoms initially include nonspecific symptoms (e.g., fa-
tigue, headache, muscle cramps, lumbago, insomnia, loss of
memory, impotence, slowing of movements) and eventually
behavioral and psychotic changes, symptoms resembling
Parkinson's disease, and dystonia with severe gait distur-
bances (Pal et al., 1999). The extrapyramidal symptoms are
often irreversible and the primary site of the neurological
damage is the globus pallidus.
Accordingly, investigators have identified subclinical
neurological signs through a variety of tests. These include
signal hyperintensity on Tl weighted MRI (magnetic reso-
nance imaging) scans (Pal et al., 1999) and batteries of
neuro behavioral, small motor, and postural tests (Mergler et
al., 1999). Neither clinical nor subclinical neurological ef-
fects of excess inhaled manganese have been reported in live-
stock or pets (ATSDR, 2000).
Intravenous Exposure to Inorganic IVIanganese
Because manganese is an essential element, some physi-
cians have added manganese to parenteral solutions. Veteri-
narians may also be interested in supplementing the
parenteral solutions given to pets. This may not be wise.
Malecki et al. (1995) observed that rats rapidly accumu-
lated manganese in extrahepatic tissues when small (0.1
|imole/day) amounts of manganese were added to
parenteral solutions. Furthermore, several investigators
noted altered MRI scans (resembling those observed in pa-
tients with manganism from excess inhalation of manga-
nese) among patients receiving manganese-supplemented
total parenteral nutrition (TPN) solutions (Ono et al., 1995;
Fell et al., 1996) and among patients with impaired liver
functions (Hauser et al., 1994). Takagi et al. (2002) calcu-
lated the optimal parenteral does of manganese for adult
humans to be 1 |imol/day of manganese (<0.02 |imol/kg
BW/day of manganese).
Exposure to Organic Forms of Manganese
The effects of ingesting in diet or inhaling organic forms
of manganese (i.e., MMT, Maneb, Mancozeb) have not been
reported for livestock or pets (ATSDR, 2000). Moreover,
the adverse effects of the manganese-containing pesticides
on humans and rodents were assumed to result from expo-
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240
MINERAL TOLERANCE OF ANIMALS
sure to the "whole compound, not necessarily from exposure
to manganese" by the ATSDR (2000).
TISSUE LEVELS
Most tissues normally contain less than 3 |lg/g wet
weight of manganese (ATSDR, 2000). Generally tissue
concentrations of manganese are decreased during manga-
nese deficiency (Hurley and Keene, 1987; Malecki et al.,
1996).
Generally, livestock do not accumulate extremely high
levels of manganese in their tissues when excess manganese
was fed (Table 19-2). Chicks fed 1,000 to 4,000 mg/kg of
manganese as chloride, sulfate, carbonate, and oxide salts of
manganese were reported to have <2 mg/kg dry muscle of
manganese and <31 mg/kg dry liver of manganese (South-
ern and Baker, 1983; Black et al., 1984, 1985b). Feeding
hens 13 and 1,000 [ig/g diet of manganese resulted in egg
yolks containing 4 and 33 ^Ig/g wet weight of manganese,
respectively (NRC, 1980).
Cattle fed 1 ,000 mg/kg diet of manganese had <2 mg/kg
dry muscle of manganese, 13 to 27 mg/kg dry liver of man-
ganese, and manganese induced histochemical and histologi-
cal alterations in gastrointestinal mucosa of guinea pigs <2
mg/kg dry bone of manganese (Ho et al., 1984; Jenkins and
Hidiroglou, 1991). Sheep fed 2,000 to 4,500 mg/kg diet of
manganese had <2 mg/kg dry muscle of manganese, usually
<46 mg/kg dry liver of manganese, and <29 mg/kg bone ash
of manganese (Watson et al., 1973; Black et al., 1985a;
Wong-Valle et al., 1989).
MAXIMUM TOLERABLE LEVELS
Many of the studies with swine, cattle, and sheep are old
and the diets were incompletely defined in terms of concen-
trations of other minerals. Generally cattle and sheep fed
typically adequate levels of iron developed no adverse signs
if fed <2,000 mg/kg diet of manganese and swine if fed
<1,000 mg/kg diet of manganese. The exception was
preruminant calves. Calves (weighing about 60 kg and con-
suming 0.81 kg dry matter/day at the end of the study) had
depressed hematocrits when fed 500 mg/kg milk replacer of
manganese (Jenkins and Hidiroglou, 1991).
Poultry generally developed signs if their diets contained
>3,000 mg/kg diet of manganese. Accordingly, 2,000 mg/kg
diet of manganese is a conservative estimate of a safe man-
ganese intake for chickens fed adequate, but not excessive,
levels of other minerals.
FUTURE RESEARCH NEEDS
There is limited need for additional data on the toxicity of
dietary inorganic manganese to livestock. The impact of in-
teractions between manganese and other elements, includ-
ing magnesium, on the toxicity of manganese is probably the
work most apt to produce practically important data. Future
research should focus also on apparent differences in man-
ganese toxicity from feed and water.
SUMMARY
The potential for toxicity of dietary inorganic manganese
to livestock is limited except when dietary intake of other
minerals is marginal. The first signs of manganese toxicosis
in normal animals reflect the adverse effect of dietary man-
ganese on iron or magnesium utilization. However, mam-
mals are very sensitive to excess manganese in intravenous
fluids. Fish may be more sensitive to manganese toxicity
than mammals.
REFERENCES
Abrams, E., J. W. Lassiter, W. J. Miller, M. W. Neathery, R. P. Gentry, and
R. D. Scartli. 1976. Absorption as a factor in manganese homeostasis. J.
Anim. Sci. 42: 630-636.
Abrams, E., J. W. Lassiter, W. J. Miller, M. W. Neathery, R. P. Gentry, and
D. M. Blackmon. 1977. Effect of normal and high manganese diets on
the role of bile in manganese metabolism of calves. J. Anim. Sci.
45:1108-1113.
Agrawal, S. J., and A. K. Srivastava. 1980. Haematological responses in a
fresh water fish to experimental manganese poisoning. Toxicology
17:97-100.
ATSDR (Agency for Toxic Substances and Disease Registry). 2000. Man-
ganese. Atlanta, GA: U.S. Department of Health and Human Services,
Public Health Service. Available at http://www.atsdr.cdc.gov/
toxprofiles/tplSl.html. Accessed February 29, 2004.
Ammerman, C. B., and S. M. Miller. 1972. Biological availability of minor
mineral ions: a review. J. Anim. Sci. 35:681.
Andersen M. E., J. M. Gearhart, andH. J. Clewell, III. 1999. Pharmokinetic
data needs to support risk assessments for inhaled and ingested manga-
nese. Neurotoxicology 20:161-172.
Aschner, M., K. E. Vrana, and W. Zheng. 1999. Manganese uptake and
distribution in the central nervous system (CNS). Neurotoxicology
20:173-180.
Baker, D. H., and K. M. Hatpin. 1991. Manganese and iron interrelation-
ship in the chick. Poult. Sci. 70:146-152.
Ballatori, N., E. Miles, and T. W. Clarkson. 1987. Homeostatic controls of
manganese excretion in the neonatal rat. Am. J. Physiol. 252:R842-847.
Becker, J. E., and E. V. McCollum. 1938. Toxicity of MnCl24H20 when
fed to rats. Proc. Soc. Exp. Biol. Med. 38:740-742.
Bench, G., T. M. Carlsen, P. G. Grant, J. S. Wollett, Jr., J. L. Lewis, and K.
K. Divine. 200 1 . Olfactory bulb uptake and determination of biotransfer
factors in the California ground squirrel (Spermophilus beecheyi) ex-
posed to manganese and cadmium in environmental habitats. Environ.
Sci. Technol. 35:270-277.
Bertinchamps, A. J., S. T. Miller, and G. C. Cotzias. 1966. Interdependence
of routes excreting manganese. Am. J. Physiol. 211:217—224.
Black, J. R., C. B. Ammerman, P. R. Henry, and R. D. Miles. 1984. Biologi-
cal availability of manganese sources and effects of high dietary manga-
nese on tissue mineral composition of broiler-type chicks. Poult. Sci.
63:1999-2006.
Black, J. R., C. B. Ammerman, and P. R. Henry. 1985a. Effects of high
dietary manganese as manganese oxide or manganese carbonate in
sheep. J. Anim. Sci. 60:861—866.
Black, J. R., C. B. Ammerman, P. R. Henry, and R. D. Miles. 1985b. Effect
of dietary manganese and age on tissue trace mineral composition of
broiler-type chicks as a bioassay of manganese sources. Poult. Sci.
64:688-693.
Copyright © National Academy of Sciences. All rights reserved.
&
infimi Tnlemnns nf Animals' Sennnd Revissd Edition
ttp7/www nap Rdi]/ratalng/1 1 1^Ofl htmll
MANGANESE
241
Brown, D. R., and L. L. Southern. 1985. Effect of Eimeria acervulina infection in
cliicks fed excess dietary cobalt and/or manganese. J. Nutr. 1 15:347-351.
Carter, S. D., J. F. Hein, G. L. Rehnberg, and J. W. Laskey. 1980. Chronic
manganese oxide ingestion in rats: hematological studies. J. Toxicol.
Environ. Health 6:207-216.
Chandra, S. V., andZ. Imam. 1973. Manganese induced histochemical and
histological alterations in gastrointestinal mucosa of guinea pigs. Acta
Pharmacol. Toxicol. 33(5):449^58.
Corathers, L. A. 2001. Manganese. U.S. Geological Survey Mineral Year-
book. Available at http://mineral.usgs.gov/mineral/pubs/commodity/
manganese. Accessed December 29, 2003.
Cossarini-Dunier, M., A. Demael, D. Lepot, and V. Guerin. 1988. Effect of
manganese ions on the immune response of carp (Cyprinus carpio)
against Yersinia ruckeri. Develop. Comp. Immunol. 12:573-579.
Cunningham, G. N., M. B. Wise, and E. R. Barrick. 1966. Effect of high
dietary levels of manganese on the performance and blood constituents
of calves. J. Anim. Sci. 25:532- 538.
Davies, N. T., and R. Nightingale. 1975. The effect of phytate on intestinal
absorption and secretion of zinc and whole-body retention of zinc, cop-
per, iron, and manganese in rats. Br. J. Nutr. 34:243-258.
Davis, C. D., and J. L. Greger. 1992. Longitudinal changes of manganese-
dependent superoxide dismutase and other indexes of manganese and
iron status in women. Am. J. Clin. Nutr. 55:747-752.
Davis, C. D., D. M. Ney, and J. L. Greger. 1990. Manganese, iron, and lipid
interactions in rats. J. Nutr. 120: 507—513.
Davis, C. D., E. A. Malecki, and J. L. Greger. 1992. Interactions among
dietary manganese, heme iron, and nonheme iron in women. Am. J.
Clin. Nutr, 56:926-932.
Davis, C. D., L. Zech, and J. L. Greger. 1993. Manganese metabolism in
rats: an improved methodology for assessing gut endogenous losses.
Proc. Soc. Exp. Biol. Med. 202:103-108.
Dickinson, T. K., A. G. Devenyi, and J. R. Connor. 1996. Distribution of
injected iron-59 and manganese-54 in hypotransferrinemic mice. J. Lab.
Clin. Med. 128:220-228.
Dupuis, Y., Z. Porembska, S. Tardivel, A. Fournier, and P. Fournier. 1992.
Intestinal transfer of manganese: resemblance to and competition with
calcium. Reprod. Nutr. Dev. 32(5-6) :453-460.
EPA (U.S. Environmental Protection Agency), Office of Water Quality.
2004. Drinking Water Health Advisory for Manganese. Available at
http://www.epa.gov/safewater/. Accessed June 20, 2004.
Fain, P., J. Dennis, and F. G. Harbaugh. 1952. The effect of added manga-
nese in feed on various mineral components of cattle blood. Am. J. Vet.
Res. 13:348-350.
Fell, J. M. E., A. P. Reynold, N. Meadows, K. Khan, S. G. Long, G.
Quaghebeur, W. J. Taylor, and P. J. Milla. 1996. Manganese toxicity in
children receiving long-term parenteral nutrition. Lancet 347 : 1 2 1 8-1 22 1 .
Flanagan, P. R., J. Haist, and L. S. Valberg. 1980. Comparative effects of
iron deficiency induced by bleeding and a low-iron diet on the intestinal
absorptive interactions of iron, cobalt, manganese, zinc, lead, and cad-
mium. J. Nutr. 110:1754-1763.
Freeland-Graves, J., F. Behmardi, C. W. Bales, V. Dougherty, P. H. Lin, J.
B. Crosby, and P. C. Trickett. 1988. Metabolic balance of manganese in
young men consuming diets containing five levels of dietary manga-
nese. J. Nutr. 118:764-773.
Gallup, W. D. and L. C. Norris. 1939. The amount of manganese required to
prevent perosis in the chick. Poult. Sci. 18:76-82.
Gallup, W. D., J. A. Nance, A. B. Nelson, and A. E. Darlow. 1952. Forage
manganese as a possible factor affecting calcium and phosphorus me-
tabolism of range beef cattle. J. Anim. Sci. 11 :783-784.
Garcia- Aranda, J. A., F. Lifshitz, andR. A. Wapnir. 1983. In vivo intestinal
absorption of manganese in the rat. J. Nutr. 1 13:2601-2607.
Goonan, T. G., and T. S. Jones. 2003. Manganese statistics. Available at
http://mineral.usgs.gov/minerals/pubs/of01-0006/manganese.html. Ac-
cessed December 29, 2003.
Greger, J. L. 1998. Dietary standards for manganese: overlap between nu-
tritional and toxicological studies. J. Nutr. 128:368s-371s.
Greger J. L., S. A. Smith, andS. M.Snedeker. 1981.Effectof dietary calcium
and phosphorus levels on utilization of calcium, phosphorus, magnesium,
manganese, and selenium by adult males. Nutr. Res. 1:31 5—325.
Greger, J. L., D. D. Davis, J. W. Suttie, and B. J. Lyle. 1990. Intake, serum
concentrations, and urinary excretion of manganese by adult males. Am.
LClin. Nutr. 51:457^61.
Gruden, N. 1977. Interrelationship of manganese and iron in rat's duode-
num. Nutr. Rep. Intl. 15:577-581.
Grummer, R. H., O. G. Bentley, P. H. Philips, and G. Bohstedt. 1950. The
role of manganese in growth, reproduction, and lactation in swine. J.
Anim. Sci. 9:170-175.
Halpin, K. M. and D. H. Baker. 1986. Long-term effects of corn, soybean
meal, wheat, bran, and fish meal on manganese utilization in the chick.
Poult. Sci. 65:1371-1374.
Halpin, K. M., D. G. Chausow, and D. H. Baker. 1986. Efficiency of man-
ganese absorption in chicks fed corn-soy and casein diets. J. Nutr.
116:1747-1751.
Hartman, R. H., G. Matrone, and G. H. Wise. 1955. Effect of high dietary
manganese on hemoglobin formation. J. Nutr. 57:429^39.
Hauser, R. A., T. A. Zesiewicz, A. S. Rosemurgy, C. Martinez, and C. W.
Olanow. 1994. Manganese intoxication and chronic liver failure. Ann.
Neurol. 36(6):871-875.
Hawkins, G. E., Jr., G. H. Wise, G. Matrone, R. K. Waugh, and W. L. Lott.
1955. Manganese in the nutrition of young dairy cattle fed different
levels of calcium and phosphorus. J. Dairy Sci. 38:536-547.
Heller, V. V., and R. Penquite. 1937. Factors producing perosis in chickens.
Poult. Sci. 16:243-246.
Henry, P. R. 1995. Manganese bioavailability. Pp. 239—256 in
Bioavailability of Nutrients for Animals: Amino Acids, Mineral, and
Vitamins, C. B. Ammerman, D. H. Baker, and A. J. Lewis, eds. Or-
lando, EL: Academic Press.
Ho, S. Y., W. J. Miller, R. P. Gentry, N. W. Neathery, and D. M. Blackmon.
1984. Effects of high but nontoxic dietary manganese and iron on their
metabolism in calves. J. Dairy Sci. 67:1489—1495.
Hudnell, H. K. 1999. Effects from environmental Mn exposures: a review
of the evidence from non-occupational exposure studies.
Neurotoxicology 20(2-3) :379-397.
Hurley, L. S., and C. L. Keen. 1987. Manganese. Pp. 185-223 in Trace
Elements in Human and Animal Nutrition, vol. 1, 5th ed., W. Mertz, ed.
Orlando, FL: Academic Press.
Hurley, L. S., C. L. Keen, and B. Lonnerdal. 1983. Aspects of trace element
interactions during development. Fed. Proc. 42:1735-1739.
Ivan, M., and C. M. Grieve. 1976. Effects of zinc, copper, and manga-
nese supplementation of high-concentrate ration on gastrointestinal
absorption of copper and manganese in Holstein cows. J. Dairy Sci.
59:1764-1768.
Ivan, M., and M. Hidiroglou. 1980. Effect of dietary manganese on growth
and manganese metabolism in sheep. J. Dairy Sci. 63:385-390.
Jenkins, K. J., and M. Hidiroglou. 1991. Tolerance of the preruminant calf for
excess manganese or zinc in milk replacer. J. Dairy Sci. 74:1047-1053.
Kaiser, J. 2003. Manganese: a high-octane dispute. Science 300:926-928.
Kayongo-Male, H., D. E. Ullrey, E. R. Miller, and K. K. Keahey. 1977.
Manganese, calcium and phosphorus interaction in the diet of the grow-
ing pig. Ghana J. Agric. Sci. 10:39^6.
Keen, C. L., J. G. Bell, and B. Lonnerdal. 1986. The effect of age on man-
ganese uptake and retention from milk and infant formulas in rats. J.
Nutr. 116:395^02.
Kies, C, K. D. Aldrich, J. M. Johnson, C. Creps, C. Kowalski, and R. H.
Wang. 1987. Manganese availability for humans: effect of selected di-
etary factors. Pp. 1 12—122 in Nutritional Bioavailability of Manganese.
ACS Symposium Series 35, C. Kies, ed. Washington, D.C.: American
Chemical Society.
Klaassen, C. D. 1974. Biliary excretion of manganese in rats, rabbits, and
dogs. Toxicol. Appl. Pharmacol. 29:458^68.
Klein, C. J. 2002. Manganese. In Nutrient requirements for preterm infant
formulas. J. Nutr. 132:1492s-1498s.
Copyright © National Academy of Sciences. All rights reserved.
&
infimi Tnlemnns nf Animals' Sennnd Revissd Edition
ttp7/www nap Rdi]/ratalng/1 1 1^Ofl htmll
242
MINERAL TOLERANCE OF ANIMALS
Kondakis, X. G., N. Makris, M. Leotsindis, M. Prinou, T. Papapetropoulos.
1989. Possible health effects of high manganese concentration in drink-
ing water. Arch. Environ. Health 44(3):175-178.
Krishnani, K. K., I. S. Azad, M. Kailasam, A. R. Thirunavukkarasu, B. P.
Gupta, K. O. Joseph, M. Muralidhar, and M. Abraham. 2003. Acute
toxicity of some heavy metals to Lates calcarifer fry with a note on its
histopathological manifestations. J. Environ. Sci. and Health Part A —
Toxic/Hazard. Subst. Environ. Eng. 38:645-655.
Lee, D. Y., and P. E. Johnson. 1989. ^''Mn absorption and excretion in rats fed
soy protein and casein diets. Proc. Soc. Exp. Biol. Med. 190:211-216.
Leibholz, J. J., V. C. Speer, and V. W. Hayes. 1962. Effects of dietary
manganese on baby pig performance and tissue manganese levels. J.
Anim. Sci. 21:772-776.
Lynam, D. R., J. W. Ross, G. D. Pfeifer, B. F. Fort, and T. G. PuUin. 1999.
Environmental effects and exposures to manganese from use of
methylcyclopentadienyl manganese tricarbonyl (MMT) in gasoline.
Neurotoxicology 20:145-150.
Malecki, E. A., H. C. Lo, H. Yang, C. D. Davis, D. M. Ney, and J. L.
Greger. 1995. Tissue manganese concentrations and antioxidant enzyme
activities in rats given total parenteral nutrition with and without supple-
mental manganese. J. Parenter. Enteral Nutr. 19:222-226.
Malecki, E. A., G. M. Radzanowski, T. J. Radzanowski, D. D. Gallaher,
and J. L. Greger. 1996. Biliary manganese excretion in conscious rats is
affected by acute and chronic manganese intake but not by dietary fat. J.
Nutr. 126:489-498.
Matrone G., R. H. Hartman, and A. J. Clawson. 1959. Studies of a manga-
nese-iron antagonism in the nutrition of rabbits and baby pigs. J. Nutr.
67:309-317.
Mena, 1. 1981. Manganese. Pp. 233-270 in Disorders of Mineral Metabo-
lism, F. L. Bronner and J. W. Coburn, eds. New York: Academic Press.
Mergler D., M. Baldwin, S. Belanger, F. Larribe, A. Beuter, R. Bowler, M.
Panisset, R. Edwards, A. deGeoffroy, M. P. Sassine, and K. Hudnell.
1999. Manganese neurotoxicity, a continuum of dysfunction: results
from a community based study. Neurotoxicology 20:327-343.
Miller, K. B., J. S. Caton, D. M. Schafer, D. J. Smith, and J. W. Finley.
2000. High dietary manganese lowers heart magnesium in pigs fed a
low-magnesium diet. J. Nutr. 130:2032-2035.
Moinuddin, J. F., and H. W. T. Lee. 1960. Alimentary, blood and other changes
due to feeding MnS04, MgSO^, and Na^SO^. Am. J. Physiol. 199:77-83.
NRC (National Research Council). 1980. Manganese. In Mineral Tolerance
of Domestic Animals. Washington, D.C.: National Academy Press.
NRC. 1994. Nutrient Requirements of Poultry, 9th ed. Washington, D.C.:
National Academy Press.
NRC. 1995. Manganese. In Nutrient Requirements of Laboratory Animals,
4th ed. Washington, D.C.: National Academy Press.
NRC. 1998. Nutrient Requirements of Swine, 10th ed. Washington, D.C.:
National Academy Press.
NRC. 2000. Manganese. In Nutrient Requirements of Beef Cattle. Wash-
ington, D.C.: National Academy Press.
NRC. 2001. Manganese Requirements. In Nutrient Requirements of Dairy
Cattle. Washington, D.C. : National Academy Press.
NRC. 2001. Manganese. In Dietary Reference Intakes for Vitamin A, Vita-
min K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese,
Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, D.C:
National Academy Press.
Ono, J., K. Harada, R. Kodaka, K. Sakurai, H. Tajiri, Y. Takagi, T. Nagai,
T. Harada, A. Okada, and S. Okada. 1995. Manganese disposition in the
brain during long-term total parenteral nutrition. J. Parenter. Enteral
Nutr. 19:310-312.
Pal, P. K., A. Samii, and D. B. Calne. 1999. Manganese neurotoxicity: a
review of clinical features, imaging, and pathology. Neurotoxicology
20(2-3):227-238.
Pennington, J. A., and B. E. Young. 1991. Total diet study nutritional ele-
ments 1982-1989. J. Am. Diet. Assoc. 71:179-183.
Prabowo, A., J. W. Spears, and L. Goode. 1988. Effects of dietary iron on
performance and mineral utilization in lambs fed a forage-based diet. J.
Anim. Sci. 66:2028-2033.
Rehnberg, G. L., J. F. Hein, S. D. Carter, R. S. Linko, and J. W. Laskey.
1981. Chronic ingestion of MnjO^ by rats: tissue accumulation, distri-
bution and depletion. J. Toxicol. Environ. Health 9:263-272.
Rehnberg, G. L., J. F. Hein, S. D. Carter, R. S. Linko, and J. W. Laskey. 1982.
Chronic ingestion of MnjO^ by rats: tissue accumulation and distribution
of manganese in two generations. J. Toxicol. Environ. Health 9:175-188.
Reid, J. T., K. O. Pfau, R. L. Salisbury, C. B. Bender, and G. M. Ward.
1947. Mineral metabolism studies in dairy cattle, 1. The effect of man-
ganese and other trace elements on the metabolism of calcium and phos-
phorus during early lactation. J. Nutr. 34:661-676.
Schroeder, W. H., J. J. Balassa, and I. H. Tipton. 1966. Essential trace metals
in man: manganese. A study in homeostasis. J. Chronic Dis. 19:545-571.
Shukla, A., K. N. Agarwal, and G. S. Shukla. 1990. Effect of latent iron
deficiency on the levels of iron, calcium, zinc, copper, manganese, cad-
mium and lead in liver, kidney, and spleen of growing rats. Experientia
46:751-752.
Southern, L. L., and D. H. Baker. 1983. Excess manganese ingestion in the
chick. Poult. Sci. 62(4):642-646.
Symonds, H. W., and E. D. Hall. 1983. Acute manganese toxicity and the absorp-
tion and biliary excretion of manganese in cattle. Res. Vet. Sci. 35:5-13.
Takagi, Y., A. Okada, K. Sando, M. Wasa, H. Yoshida, and N. Hirabuki.
2002. Evaluation of indexes of in vitro manganese status and the opti-
mal intravenous dose for adult patients undergoing home parenteral
nutrition. Am. J. Clin. Nutr. 75:112-118.
Thomson, A. B. R., D. Olatunbosun, and L. S. Valberg. 1971. Interrelation
of intestinal transport system for manganese and iron. J. Lab. Clin. Med.
78:642-655.
Thompson, T. N., and C. D. Klaassen. 1982. Presystemic elimination of
manganese in rats. Toxicol. Appl. Pharmacol. 64:236—243.
Tjalve, H., and J. Henriksson. 1999. Uptake of metals in the brain via olfac-
tory pathways. Neurotoxicology 20:181-196.
Umarji, G. M., K. G. Anantanarayan, and R. A. Bellare. 1969. Content of
manganese in rabbit hair in the course of oral chronic administration of
manganese sulfate. C. R. Soc. Biol. 163:1725-1729.
Velasquez, S. E., and J. T. Du, 1994. Derivation of the reference dose for
manganese. Pp. 253-266 in Risk Assessment of Essential Elements, W.
Mertz, C. O. Abernathy, and S. S. Olin, eds. Washington, D.C: ILSl
Press.
Vieregge, P., B. Heinzow, G. Korf, H. M. Teichert, P. Schleifenbaum, and
H. U. Mosinger. 1995. Long term exposure to manganese in rural well
water has no neurological effects. Can. J. Neurol. Sci. 22:286-289.
Vohra, P., and F. H. Kratzer. 1968. Zinc, copper, and manganese
toxicities in turkey poults and their alleviation by EDTA. Poultry
Sci. 47:699-704.
Waagbo, R., K. Hamre, E. Bjerkas, R. Berge, E. Wathne, O. Lie, and B.
Torstensen. 2003. Cataract formation in Atlantic salmon, Salmo salar
L., smolt relative to dietary pro- and antioxidants and lipid level. J. Fish
Dis. 26:213-229.
Wachtel, L. W., C. A. Elvehjem, and E. B. Hart. 1943. Studies on the physi-
ology of manganese in the rat. Am. J. Physiol. 140:72—81.
Watson, L. T., C B. Ammerman, J. P. Feaster, and C E. Roessler. 1973.
Influence of manganese intake on metabolism of manganese and other
mineral in sheep. J. Anim. Sci. 36:131-136.
Wedekind, K. J., E. C Titgemeyer, A. R. Twardock, andD. H. Baker. 1991.
Phosphorus, but not calcium, affects manganese absorption and turn-
over in chicks. J. Nutr. 121:1776-1786.
Wilgus, H. S., Jr., and A. R. Patton. 1939. Factors affecting manganese
utilization in the chicken. J. Nutr. 18:35^5.
Wong-Valle, J., P. R. Henry, C B. Ammerman, and P. V. Rao. 1989. Esti-
mation of the relative bioavailability of manganese sources for sheep. J.
Anim. Sci. 67:2409-2414.
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20
Mercury
INTRODUCTION
Mercury (Hg, with atomic number, 80; atomic weiglit,
200.59; specific gravity, 13.55) exists in tiiree oxidation
states: Hg° (metallic), Hg"*" (mercurous), and Hg+"'" (mercu-
ric) mercury. Each form has a different solubility, reactivity,
and toxicity profile. The metal is dense, silvery-white, shiny,
and a liquid at room temperature. Mercuric compounds are
much more common than mercurous compounds and include
simple salts, such as mercuric chloride, nitrate, and sulfate.
Mercuric chloride (HgClj) and acetate are soluble in water
in toxicologically relevant amounts, whereas mercurous
chloride (Hg,Cl,) is only marginally soluble (2 mg/L) and
HgS is highly insoluble. Hg+"'' can also form organometallic
derivatives in which the mercury atom is covalently bound
to one or two carbon atoms. The carbon-mercury bond is
chemically stable and is not normally split in water or by
weak acids or bases. Methylmercury salts are highly soluble
in water. The metabolism and biological effects of mercury
are intimately related to its high affinity constant (10'-^- 10^°)
for thiol-containing molecules.
Naturally occurring mercury is usually found in cinnabar
ore, which contains mercuric sulfide. Algeria, China,
Kyrgyzstan, and Spain are currently the leading countries
that mine cinnabar for mercury production. Active mining of
mercury in North America has diminished, and mercury is
now produced predominantly as a by-product from gold min-
ing operations in the states of California, Nevada, and Utah,
and in Canada.
Mercury has many unique metallic properties including flu-
idity at room temperature, uniform volume expansion over
the entire liquid temperature range, high surface tension, good
electrical conductivity, and ability to alloy with other metals.
These physical characteristics make it valuable for a wide va-
riety of applications such as thermometers, barometers,
switching devices, batteries, and dental restorations. Amal-
gams used in dentistry contain approximately 50 percent me-
tallic mercury. Mercury's ability to amalgamate with gold and
silver is used in the mining of these precious metals. Most of
the mercury used in the United States is for chlorine-caustic
soda production and electronic applications such as switches
(USGS, 1992). Due to their toxic properties, mercuric com-
pounds were routinely used as bactericides and fungicides in
paints and agricultural fumigants and as wonning medications.
Many of these applications have been banned due to the per-
sistence of mercury in the environment. In human and veteri-
nary medicine, mercurochrome, thimerosal, and phenylmer-
curic nitrate are used as antiseptics and preservatives, although
use is declining.
Human activities are a major source of mercury release
into the environment. Volcanic activity is the predominant
natural source. When mercury is released into the environ-
ment, some of it is transformed into methylmercury by bacte-
ria and fungi. The methylation is believed to involve a nonen-
zymatic reaction between Hg++ and a methylcobalamin
compound that is produced by bacteria (Wood and Wang,
1983). This reaction takes place primarily in aquatic systems.
Thus, it is methylmercury of microbial origin that enters the
food chain and accumulates in animals. Consequently, most
of the research on mercury toxicity has examined the organic
form. Toxicities due to inorganic mercury are typically due to
accidental consumption of medicinals. Metallic mercury tox-
icities occur only following inhalation exposure during vari-
ous industrial processes, but would not likely occur in animal
husbandry. Metallic mercury consumed orally has a very low
toxicity profile and will not be considered here. Several excel-
lent reviews are available on the toxicity of metallic mercury
(ATSDR, 1999; IPCS, 2003).
ESSENTIALITY
Mercury is not known to be an essential element for ani-
mals. In several experiments in rodents, pigs, and chicks,
low levels of inorganic mercury increased growth rate; how-
ever, this effect was not seen in all experiments (Johnston
and Savage, 1991).
248
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MERCURY
249
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
The analysis of total mercury in biological samples is use-
ful as an initial screening, but due to the vastly differing
toxicological profiles of inorganic and organic forms, quan-
tification of each species is useful. Mercury is relatively vola-
tile and easily lost during sample storage, preparation, and
analysis if appropriate methods are not used. Oxidizing prop-
erties of lab ware can cause the loss of methylmercury,
whereas methylmercury may be produced from inorganic
mercury by microbial action in aqueous samples. As with all
minerals, careful attention must be paid to inadvertent con-
tamination of the sample with mercury, especially when de-
termining trace concentrations. Glass or Teflon® should be
thoroughly cleaned, acid-leached, and given a final soaking
in hot (70°C) 1 percent HCl to remove any traces of oxidiz-
ing compounds (e.g., chlorine) that may subsequently de-
stroy methylmercury (ATSDR, 1999). Repeated freezing and
thawing of wet, biological samples can cause the loss of
methylmercury (Horvat and Byrne, 1992). Tissue samples
may be freeze-dried without loss of methylmercury. Stan-
dard or certified reference materials are useful to validate
sample preparation, storage, and analytical methods. Stan-
dards should have a physical and chemical composition that
reflects the samples being analyzed (Horvat, 1999).
Total mercury may be determined following reduction of
all the mercury in the sample to its elemental state using
harsh (nitric acid/perchloric acid, bromate/bromide) diges-
tions. Inorganic mercury can be determined after milder di-
gestions (HCl, sulfuric acid) and reduction. Quantification
may be accomplished using a variety of methods including
AAS, atomic fluorescence spectrometry (AFS), electrother-
mal atomic absorption (ETAAS), neutron activation analy-
sis (NAA), mass spectrometry (MS), and anodic stripping
voltammetry (ASV). Of the available methods, cold vapor
(CV) AAS is the most widely used to determine total mer-
cury in plant and animal tissues. Using standard techniques,
levels of around one ppb can be reliably measured (ATSDR,
1999).
Independent quantification of inorganic and organic
forms of mercury requires isolation or separation of the spe-
cies prior to detection. Extraction, chromatography, distilla-
tion, acid leaching, and alkaline digestion have been rou-
tinely employed for separating species followed by
quantification using CV AAS, CV AFS, or other detection
techniques. Capillary gas-liquid chromatography with elec-
tron capture detection is often used for determining meth-
ylmercury levels in biological samples.
REGULATION AND METABOLISM
Absorption of mercury is highly dependent on its chemi-
cal form. Gastrointestinal absorption of metallic mercury is
only about 0.01 percent of the dose in both humans and ani-
mals. Dermal absorption is also low. Absorption of inor-
ganic mercury from the GI tract ranges between 1 and 40
percent depending on species, age, diet, intestinal pH, and
the solubility of the source. Absorption of organic mercury
compounds is very efficient; the efficiency of methylmer-
cury absorption is 90 percent or greater in mammals and
chickens (March et al., 1983; ATSDR, 1999). In ruminants,
methylmercury is demethylated in the rumen to inorganic
mercury, markedly lowering its absorption (Kozak and
Forsberg, 1979). Fish are able to absorb methylmercury from
water 100 times as fast as inorganic mercury and they absorb
methylmercury from food 5 times more efficiently (Johnston
and Savage, 1991).
Age is a primary factor that influences the absorption of
inorganic mercury. For example, 1 -week-old suckling mice
absorbed 38 percent mercuric chloride, whereas adult mice
absorbed only 1 percent of a dose in standard diets and 7
percent in a milk-based diet (Kostial et al., 1979). Absorp-
tion of mercurous compounds is lower than mercuric forms,
probably because of lower solubility. Bacteria flora in the
gastrointestinal tract may convert some ionic mercury into
methylmercuric compounds prior to absorption. Presumably,
species with active microbial conversion absorb inorganic
mercury most efficiently.
Once absorbed, mercury is transported to tissues via the
blood. Inorganic mercury in the blood is divided about
equally between plasma and red blood cells (Zalups and
Lash, 1994). In plasma, mercury is bound to sulfhydryl
groups on proteins, especially albumin. In erythrocytes, it is
bound to hemoglobin and glutathione. About 90 percent of
the methylmercury in blood is found in the red blood cells.
Methylmercury associates with thiol-containing amino ac-
ids because of the high affinity of the methylmercuric cation
for sulfhydryl groups. Binding of the methylmercury cation
to the thiol group of cysteine creates a chemical structure
similar to that of the essential amino acid methionine. Thus,
methylmercury can cross cell membranes via a carrier-medi-
ated amino acid transport system. Inorganic mercury does
not readily cross cell membranes, but the ionic form may
form complexes with selenium that are more lipophilic and
better able to cross membranes.
The three forms of mercury can be interconverted in the
tissues. Metallic mercury can be oxidized by the hydrogen
peroxide-catalase pathway in the body to its inorganic diva-
lent form. Conversely, absorbed divalent mercury com-
pounds can be reduced to the metallic or monovalent form.
In the presence of protein sulfhydryl groups, mercurous mer-
cury (HgH-) disproportionates to one divalent cation (Hg"*"*")
and one molecule at the zero oxidation state (Hg"). Meth-
ylmercury and phenylmercury can be converted into diva-
lent inorganic mercury in the microsomes of liver and other
tissues (Suda and Hirayama, 1992). Hydroxyl radicals pro-
duced by cytochrome P-450 reductase appear to be a pri-
mary source of reactive species that induces alkyl mercury
degradation.
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250
MINERAL TOLERANCE OF ANIMALS
The tissue distribution of mercury differs depending upon
tiie form of mercury consumed. Following absorption of
mercuric chloride, the liver and kidneys have the highest
mercury levels, whereas the brain and muscle have substan-
tially lower levels. Methylmercury distributes readily to all
tissues. The liver, kidney, and spleen have the highest levels,
but the brain and muscle also accumulate substantial
amounts of methylmercury. This relatively uniform tissue
distribution is due to methylmercury' s ability to cross cell
membranes without difficulty. However, its continual
demethylation in tissues over time results in a shift in distri-
bution because inorganic mercury accumulates in the kidney
and liver. In fish, methylmercury is found predominantly in
the muscle, whereas inorganic mercury is found in highest
levels in the gastrointestinal epithelium.
Mercury can accumulate in hair following oral exposure
to either organic or inorganic mercury. Hair mercury levels,
determined using segmental hair analysis, can be used to
monitor the historical record of exposure to mercury. The
incorporation of mercury into hair is irreversible; the loss of
hair mercury occurs only as the result of hair loss. Following
methylmercury exposure, the concentration of mercury in
the hair is proportional to the concentration of mercury in
the blood. However, hair mercury levels do not reliably re-
flect the level of exposure to elemental mercury or inorganic
mercury compounds (IPCS, 2003). Feather mercury concen-
trations in chickens approximate tissue concentrations on a
dry matter basis following consumption of either organic or
inorganic mercury (March et al., 1983).
Methylmercury effectively crosses both the blood-brain
barrier and the placenta, resulting in higher levels of mer-
cury in the fetal than the maternal brain. Mercuric mercury
penetrates the blood-brain and placental barriers only to a
limited extent, although it does slowly accumulate in the fe-
tus. Mercury from either organic or ionic sources is also
transported into milk (Yoshida et al., 1994).
Tissues are protected against the toxic effects of inorganic
mercury in two ways. Divalent mercury can induce
metallothionein, and a large proportion of the inorganic mer-
cury in the liver and kidneys is bound to this sulfhydryl-rich
protein. Mice that are genetically unable to express
metallothionein are more susceptible to inorganic mercury
toxicity (Satoh, 1997; Stankovic et al., 2003). In the liver,
mercury forms complexes with selenium. Divalent mercury
forms insoluble mercuric selenide in the liver, which is
thought to be a detoxification mechanism in fish and marine
mammals (Storelli and Marcotrigiano, 2002).
Methylmercury has little affinity for metallothionein. It
interacts with selenium to form bismethylmercury selenide,
which is soluble and not stable and thus not likely to be a
good detoxification mechanism. Methylmercury is thought
to be detoxified in two stages (Palmisano et al., 1995). In the
first stage, mercury is stored in the liver as methylmercury.
Above a threshold concentration, a demethylation process
takes place and inorganic mercury forms mercury selenide.
Excretion of inorganic mercury is predominantly via the
urine and feces. High doses increase the percentage of ex-
cretion via the urine. Elimination of metallic mercury also
occurs through the urine and feces, but significant amounts
are also lost through expired air. Methylmercury is excreted
more slowly than inorganic mercury, and the major route of
excretion is the feces via the bile. In bile, methylmercury is
complexed to nonprotein sulfhydryl compounds like glu-
tathione and secreted into the lumen of the intestines
(Ballatori and Clarkson, 1984; Naganuma and Imura, 1984).
Methylmercury is slowly converted into its inorganic form
by intestinal flora, and most of the mercury excreted is in the
inorganic form. Methylmercury that is not demethylated is
resorbed via the enterohepatic circulation and retained.
Elimination of methylmercury compounds generally follows
first-order kinetics. The whole-body half-life of methylmer-
cury and mercuric chloride in humans is about 70 and 40
days, respectively (IPCS, 2003). Neonatal animals have a
lower excretory capacity than adults. In fish, the half-life of
methylmercury is 700 days (Sweet and Zelikoff, 2001), and
methylmercury is retained in the body two to five times
longer than inorganic mercury (Johnston and Savage, 1991).
In chickens, the egg is a major excretory pathway for meth-
ylmercury (Kambamanoli-Dimou et al., 1991).
Mechanism of Toxicity
Cellular mechanisms for the toxic effects of inorganic
and organic mercury are believed to be similar, with the
differences in toxic symptoms caused by these two forms
resulting from differences in their tissue distribution
(ATSDR, 1999). High-affinity binding of divalent mercu-
ric ions to thiol or sulfhydryl groups of proteins is believed
to be the major mechanism of mercury toxicity. Binding to
hydroxyl, carboxyl, and phosphoryl groups may also con-
tribute to toxicity (ATSDR, 1999). Sulfhydryl groups play
an integral part in the structure and function of most pro-
teins, and binding by mercury results in decreased enzyme
activities, impaired structural functionality, and disruption
of transport processes (Zaiups and Lash, 1994). Through
alterations in intracellular thiol status, mercury can pro-
mote oxidative stress, lipid peroxidation, mitochondrial
dysfunction, and changes in heme metabolism. Mercury-
thiol complexes also possess redox activity that promotes
the oxidation of many molecules, including nucleotides.
The selenium-dependent form of glutathione peroxidase is
highly sensitive to inhibition by inorganic mercury, and it
has been proposed that mercury's interactions with sele-
nium limits the amount of selenium available for this en-
zyme (Nielsen and Andersen, 1991). Mercury also disrupts
intracellular calcium homeostasis leading to dysregulation
of a wide variety of cellular functions.
The cytotoxic effects of mercury exhibit a threshold phe-
nomenon. No cellular necrosis is observed up to a certain
dose, but at higher levels necrosis progresses rapidly, some-
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MERCURY
251
times in an all-or-none relationship. This is thought to be due
to the buffering effect of endogenous ligands like
metallothionein and glutathione. Once the buffer becomes
saturated, additional mercury binds to critical nucleophilic
groups in the cell and causes functional impairment (Zalups
and Lash, 1994).
SOURCES AND BIOAVAILABILITY
Animals are exposed to mercury primarily by consuming
high levels of mercury-containing foods. Consumption of
mercury-laden soils while grazing may occur occasionally,
as does accidental consumption of liquid metallic mercury.
A variety of mercuric and mercurous-based medications are
approved for veterinary use, primarily as antiseptics. Exces-
sive dermal application or accidental consumption of these
products has occasionally resulted in toxicities in animals.
Thimerosal (ethylmercury) is used as a preservative in vac-
cines and pharmaceuticals. Its toxicity is similar to that of
methylmercury (Magos, 2001). Most foods and environ-
ments have relatively low levels of mercury, but point
sources in the environment and contaminated feedstuffs re-
main a problem.
Mercury occurs in the Earth's crust at levels averaging 80
|jg/kg, but the actual concentration varies considerably de-
pending on location. Certain shales have mercury up to 10
mg/kg. The major source of mercury is the natural degassing
of the Earth's crust by volcanoes and volatilization from the
ocean. Anthropogenic activities also account for substantial
releases into the environment. These include the burning of
fossil fuel; the production of steel, cement, and phosphate;
alkali processing; smelting of metals; and mining of gold
and mercury. Once in the atmosphere, mercury is widely
disseminated and can circulate for years, accounting for its
widespread distribution.
Concentrations of dissolved mercury in aquatic environ-
ments are open oceans, 0.5-3 ng/L; coastal sea waters, 2-15
ng/L; rivers and lakes, 1- 3 ng/L (IPCS, 1986). Local varia-
tion is considerable because suspended material may also
contribute to the total load.
Organic and inorganic forms of mercury differ greatly in
their environmental fate and potential to become toxic. Much
of the inorganic mercury in natural waters and in soil is
strongly bound to sediment or organic material and is un-
available to organisms. The methylation of inorganic mer-
cury by bacteria in the sediment of aquatic environments is
the limiting step in the transport of mercury into food chains.
Low pH and high levels of dissolved organic compounds
increase the rate of methylation. Once produced by bacteria,
methylmercury enters the food chain. Because animals ac-
cumulate methylmercury faster than they can eliminate it,
animals consume higher concentrations of mercury at each
successive level of the food chain. Thus, low environmental
concentrations of methylmercury can bioaccumulate to po-
tentially harmful concentrations in fish, fish-eating wildlife.
and people. The highest levels are found in long-lived preda-
tory fish, such as swordfish and sharks in the oceans and
pike and bass in freshwater.
Even at locations remote from point sources, mercury
biomagnification can result in toxic effects in consumers at
the top of aquatic food chains. Bioconcentration factors,
which are the ratio between the concentration of mercury in
an organism and the concentration in the medium to which
the organism was exposed, are as follows: algae, about
1,000-8,000; vegetables, <0.1; invertebrates, often >1,000;
fish, often >1,000; birds, about 2 (IPCS, 1986).
In soil and in water, the monovalent or divalent forms of
inorganic mercury predominate and bind strongly to humic
materials and sesquioxides. Mercury sorption to soils gener-
ally decreases with increasing pH and/or chloride ion concen-
tration. Soils in proximity to mercury mines may contain high
levels of mercury. For example, soil in a sheep pasture in Ger-
many near a mercury mining area that was operated since the
15th century contains 435 mg Hg/kg (Gebel et al., 1996). The
accumulation of mercury in plants generally increases with
increasing soil mercury concentration, but is highly depen-
dent on soil characteristics. High organic matter content and
pH decrease the uptake. Generally, the highest concentrations
of mercury are found at the roots, but translocation to other
organs (e.g., leaves) occurs (IPCS, 1986).
Concentrations of mercury in most foodstuffs are often
below the detection limit (usually 20 ng/g fresh weight). Fish
and marine mammals are the dominant sources. The typical
concentration in edible tissues of various species of fish
range from 50-1,400 |Jg/kg fresh weight; however, fish from
contaminated aquatic environments can have 10 mg/kg
(IPCS, 2003). Liver typically has the highest concentrations,
followed by kidney, and muscle has lower levels. The chemi-
cal form of the mercury is tissue dependent. In skeletal
muscle, most (70-90 percent of the total) is methylmercury
compounds, especially methylmercury-cysteine or a chemi-
cally related species (Harris et al., 2003). The liver contains
variable amounts of mercury-selenium complexes. When
mercury levels are high, these insoluble complexes domi-
nate and methylmercury levels account for less than 50 per-
cent of the mercury. Fish typically used for the production of
fishmeal, such as anchovy, herring, and menhaden, occupy a
low level in the food chain and typically have relatively low
levels of mercury. When fishmeals are made from the offal of
fish at higher levels of the food chain (e.g., dogfish or orange
roughy), the meal can contain mercury at 1-2.4 mg/kg wet
weight. Whalemeals have been found to contain in excess of
10 mg/kg. In most fishmeals, greater than 80 percent of the
mercury is in the form of methylmercury (Johnston and Sav-
age, 1991).
Bioavailability
The bioavailability of different forms of mercury is de-
pendent on the efficiency of absorption from the gas-
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252
MINERAL TOLERANCE OF ANIMALS
trointestinal tract. Consequently, the bioavailability of me-
thylmercury is 3-10 times greater than that of mercuric
salts, and roughly a 1,000-fold higher than elemental me-
tallic mercury.
Mercury in soil is largely immobile and insoluble, sug-
gesting that it has a bioavailability that is 3- to 10-fold lower
than mercuric chloride (Paustenbach et al., 1997). Mercuric
sulfide, which is the predominant form naturally found in
many soils, is highly insoluble. Its bioavailability is less than
that of mercuric chloride (Sin et al., 1983). The mercury in
harbor sludge and in sewage sludge is also relatively un-
available (Van Der Veen and Vreman, 1986). Milk proteins
appear to increase the bioavailability of inorganic mercury
through forming complexes and increasing absorption (Mata
etal., 1997).
The bioavailability of methylmercury is decreased by
phytate, some types of fiber, and complexing with sele-
nium (Chapman and Chan, 2000; Tchounwou et al., 2003).
Dietary fibers, such as pectin and cellulose, can alter the
ability of microflora to demethylate methylmercury and
therefore affect its reabsorption rate. For example, wheat
bran enhances fecal excretion of mercury after methylmer-
cury exposure by increasing its demethylation rate by in-
testinal flora (Rowland et al., 1986). Using neurotoxicity
as an endpoint, the bioavailability of mercury in fish or seal
liver is somewhat lower than methylmercury chloride in
cats, rats, and quail (Ganther and Sunde, 1974; Ohi et al.,
1976; Eaton et al., 1980). This may be due to the presence
of mercury-selenium complexes that are of low
bioavailability. However, methylmercury-cysteine found in
fish has a higher rate of fecal excretion and lower rate of
tissue accumulation than methylmercury chloride
(Berntssen et al., 2004).
TOXICOSIS
Because of their differing bioavailabilities and tissue dis-
tributions, the toxicity profiles of organic mercury and inor-
ganic mercury differ (Table 20-1). Accumulation of inor-
ganic mercury in the kidneys causes changes in renal
function, which are one of the most sensitive indications of
its toxicity. The easy transport of methylmercury into the
brain and across the placenta makes the nervous system and
the fetus sensitive indicators for the organic form. The fol-
lowing discussion treats these two forms of mercury sepa-
rately. The bulk of the information regarding toxicity result-
ing from oral exposure to inorganic mercury comes from
studies of mercuric chloride, whereas methylmercuric chlo-
ride has served as the model for studying organic mercury
toxicity. The extensive literature on the toxicology of mer-
cury exposure in humans and animal models, primarily pri-
mate and rodent, has been reviewed by the National Research
Council, the U.S. Environmental Protection Agency, and the
World Health Organization (ATSDR, 1999; NRC, 2000;
IPCS, 2003).
Single Dose
Inorganic Mercury
Ingestion of mercuric chloride is highly irritating to the
tissues of the mucosa of the mouth and the gastrointestinal
tract. Blisters and ulcers on the lips and tongue and vomiting
occur quickly after consumption. Necrotizing ulceration and
hemorrhages develop throughout the gastrointestinal tract.
Death from oral exposure to inorganic mercury is usually
caused by shock, cardiovascular collapse, acute renal fail-
ure, and severe gastrointestinal damage. In human adults, a
lethal dose of mercuric chloride is estimated to be 10-42 mg
Hg/kg BW. In rats, the oral LD^q for a single dose of mercu-
ric chloride ranges from 26-78 mg Hg/kg BW depending on
age, with younger animals being most sensitive (Kostial et
al., 1978). A single gavage dose of mercuric chloride at 7.4
mg Hg/kg BW in water caused significant decreases in blood
lactate dehydrogenase hemoglobin, erythrocytes, and hema-
tocrit and renal pathology (Nielsen and Andersen, 1995). In
quail, the LD^g for a single dose of mercuric chloride ranges
from 26-54 mg Hg/kg BW from 3-30 days of age, respec-
tively (Hill and Soares, 1987). The quail rapidly (15 min-
utes- 1 hour) developed extreme neurological dysfunction
and usually died within 6-24 hours.
Organic Mercury
In quail, the LD^q for a single dose of methylmercury
chloride ranges from 1 1-26 mg Hg/kg BW from 3-30 days
of age, respectively (Hill and Soares, 1987). The quail slowly
developed clinical signs and most deaths occurred from 3-7
days after dosing (Hill and Soares, 1987).
Acute
Inorganic Mercury
Chickens given water containing 500 mg Hg/L as HgClj
had decreased growth rates and hematological changes
within 3 days, and mortality increased within 9 days. One of
the major signs of toxicity was dehydration due to refusal to
drink the mercury-containing water (Grissom and Thaxton,
1985, 1986). TheLDggfor HgCljin quail chicks exposed via
the diet for 5 days ranged between 2,956 and 5,086 mg Hg/kg
diet (Hill and Soares, 1987). Symptoms included ruffled
feathers, tremors, and lethargy.
The NOAEL for rats administered mercuric chloride 5
days a week for 2 weeks is 0.93 mg Hg/kg/day using a
change in kidney weight as the endpoint. Renal pathology
and changes in renal function occur at 3.7 mg Hg/kg/day
(ATSDR, 1999).
Inorganic mercury is toxic to fish at low concentrations.
The gills are a primary site of pathology, which is character-
ized as apoptosis of laminar cells and laminar fussion within
the branchial tissue (Daoust et al., 1984). The LCjq values
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MERCURY
253
(|jg Hg/L) for freshwater fish exposed for 96 hours are tila-
pia, 350; rainbow trout, 220; striped bass, 90; carp, 180
(IPCS, 1986); and catfish, 570 (Elia et al., 2003). Toxicity is
affected by temperature, salinity, dissolved oxygen, and wa-
ter hardness. Embryonic and larval stages are considerably
more sensitive, and LC^q values (|ig Hg/L) for the embryo
through the larval period are 30 and 4.7 for channel catfish
and rainbow trout, respectively.
Organic Mercury
Laying hens gavaged with methylmercury chloride at 2.7
mg Hg/kg BW for 6 days had a marked decrease in egg pro-
duction and shell quality (Lundholm, 1995). This level of
exposure is equal to 27 mg Hg/kg diet at a food intake of 100
g/day. The LD^q for methylmercury chloride in quail chicks
exposed via the diet for 5 days ranged between 32 and 47 mg
Hg/kg diet, for hatchlings and 2-week-old chicks, respec-
tively (Hill and Soares, 1987).
Rats exposed to methylmercury at 4 mg Hg/kg BW/day
for 8 days develop overt signs of neurotoxicity. These symp-
toms may not be observed until several days after cessation
of dosing (Magos et al., 1985). Methylmercury at levels be-
low 0.1 mg Hg/kg BW/day appear to be tolerated over short
periods of time by rodents (ATSDR, 1999).
Chronic
Inorganic Mercury
Chronic exposure to inorganic mercury results in progres-
sive anemia, nephrotoxicity, gastric disorders, salivation, me-
tallic taste in the mouth, inflammation, tenderness of gums,
tremors, inactivity, and an abnormal gait. The kidney, particu-
larly the renal proximal tubules and glomerulus, is particu-
larly sensitive to inorganic mercury (Zalups and Lash, 1994).
Histopathology of mercury-induced nephropathy in humans
and rats includes dilated tubules with hyaline casts, degenera-
tion and atrophy of tubular epithelium, and thickened tubular
and glomerular basement membranes. In some cases accumu-
lation of inflammatory cells may occur. Markers of renal tox-
icity include proteinuria, oliguria, increases in urinary excre-
tion of tubular enzymes, decreased ability to concentrate the
urine, and increased plasma creatinine (Zalups and Lash,
1994). In rabbits, low levels of mercury cause the production
of antibodies against the glomerular basement membrane re-
sulting in immunologically mediated membranous
glomerulonephropathy. This can occur in the absence of sig-
nificant tubular damage. In rodents, decreases in body weight
or rate of gain after ingestion of mercuric chloride require a
larger dose than nephropathy (IPCS, 2003). Although inor-
ganic mercury does not readily cross the blood-brain barrier,
a broad range of neurotoxic symptoms occur following
chronic exposure and are qualitatively similar to those induced
by organic mercury compounds (see below).
Dose-response studies designed to accurately determine
safe levels of inorganic mercury for poultry, pigs, ruminants,
and companion animals are generally lacking. However,
studies designed to determine symptoms of toxicity, mecha-
nisms of toxicity, and tissue accumulation of mercury are
relevant. The insoluble HgO and HgSO^are tolerated at 100
mg Hg/kg diet in chickens with no loss in growth or egg
production, respectively (NRC, 1980; Hill et al., 1987).
However, the more soluble HgClj reduces the fertility and
growth of quail at 8 and 25 mg Hg/kg diet, respectively (Hill
and Shaffner, 1976; El-Begearmi, 1980). Quail tolerate 4 mg
Hg/kg diet for 1 year without adverse effects on egg produc-
tion or fertility (Hill and Shaffner, 1976). Ducks tolerate 0.5
mg Hg/kg diet as HgClj, but 5 mg/kg causes histopathology
in the seminiferous tubules (McNeil and Bhatnagar, 1985).
In pigs fed HgClj, 50 but not 5 mg Hg/kg diet causes hepatic
steatosis and enlarged lymph nodes (Chang et al., 1977).
In rats, the 6-month NOAEL for mercuric chloride ad-
ministered in water by gavage is 0.23 mg Hg/kg BW/day
using nephropathy as the endpoint (ATSDR, 1999). Assum-
ing a food intake of lOg/100 g BW, this dose is equivalent to
2.3 mg/kg diet. In a 2-year study giving mercuric acetate to
rats in their feed, renal damage occurred at levels as low as 2
mg Hg/kg BW/day (Fitzhugh et al., 1950). Loss of body
weight required higher doses.
In chickens, chronic consumption of water containing
HgClj at 125 mg Hg/L causes a depression in growth, but 25
mg/L is tolerated (Thaxton et al., 1975). At 300 mg/kg,
HgClj results in growth depression, increased adrenal
weights, decreased bursal weights, bursal pathology, and
impaired humoral immune responses to antigens (Thaxton et
al., 1982; Bridger and Thaxton, 1983).
In Atlantic salmon, a diet containing 5 mg Hg/kg of HgClj
results in pathological changes in the brain that are indica-
tive of mercury toxicity (Berntssen et al., 2003). Water con-
taining 64 |Jg/L of mercury from HgClj causes mortality af-
ter 3 months in rainbow trout (Niimi and Kissoon, 1994).
Organic Mercury
The most sensitive endpoint for oral exposure to organic
forms of mercury is the nervous system. The nature and se-
verity of symptoms are dependent on dose and duration of
exposure, as well as developmental stage during the expo-
sure. A developing nervous system is considerably more sen-
sitive than an adult's. Both the central and peripheral ner-
vous systems can be damaged. Ataxia, muscle spasms,
paralysis, impaired vision, loss of coordination, and hind
limb crossing are common neurological signs of methylmer-
cury exposure in animals. Changes in behavior, decreased
activity, and deficiencies in learning and memory also oc-
cur. In monkeys, neurotoxicity may not be expressed until
years after cessation of exposure to methylmercury.
Mercury-induced damage is selective to certain areas of
the brain associated with sensory and coordination functions.
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MINERAL TOLERANCE OF ANIMALS
particularly neurons in the visual cortex and granule cells of
the cerebellum. Neuronal degeneration, loss of astrocytes,
and glial proliferation in the cortical and cerebellar gray
matter and basal ganglia are evident in histological sections
(Magos et al., 1985). This damage is usually irreversible.
Cholinergic and GABA neurotransmitter systems are af-
fected by mercury exposure, but it is unclear whether
changes in neurochemical parameters are primary targets of
mercury or whether the changes are secondary to degenera-
tive changes in neurons.
The effects of methylmercury on neurodevelopment and
tissue pathology in nonreproducing rodents have been ex-
amined in a very large number of studies and several excel-
lent reviews of this literature are available (ATSDR, 1999;
NRC, 2000; IPCS, 2003). In most studies, the NOAEL was
0.1 mg Hg/kg BW/day or greater, although a few studies
found lower thresholds of toxicity. At a food intake of 1 50 g/
kg BW for growing rats, this would be equivalent to a level
of 6.7 mg/kg diet. However, levels that cause behavioral
changes in offspring are often lower (see "Effect of Mercury
on Reproduction" below).
Cats and monkeys are generally more sensitive to meth-
ylmercury than rodents. The NOAEL of methylmercury using
neurobehavioral and renal pathology endpoints in monkeys is
about 0.04 mg Hg/kg/day following long-term exposure
(ATSDR, 1999; NRC, 2000). Cats fed contaminated fish at
doses as low as 0.046 mg Hg/kg/day began to exhibit
neurobehavioral changes after 60 weeks, including mild im-
pairment of motor activity and diminished sensitivity to pain
(Charbonneau et al., 1976). At 0.074 mg Hg/kg/day, cats dis-
played neurological signs and convulsions. The NOAEL in
this study was estimated at 0.02 mg/kg BW. Assuming a food
intake of 75 g/kg BW of dry diet, chronic consumption of a
diet with 0.27 mg Hg/kg should be safe for cats.
When exposure is high enough, methylmercury also af-
fects the kidney and causes nephritis in a manner very simi-
lar to inorganic mercury (see above), suggesting that its tox-
icity results from metabolism to inorganic mercury (Magos
etal., 1985).
A variety of studies have shown decreased growth, egg
production, and fertility in chickens when methylmercury
was fed at levels above 4 mg Hg/kg diet (NRC, 1980;
Bhatnagaretal., 1982; McNeil and Bhatnagar, 1985;Prasada
Rao et al., 1989; Lundholm, 1995; Maretta et al., 1995;
Pribilincova et al., 1996). Young chickens tolerate 1.35 mg/kg
diet without decreased growth (March et al„ 1983), but 5
mg/kg greatly increases mortality (Scares, 1973). In ducks,
0.5 mg Hg/kg diet as methylmercury did not affect behav-
ioral endpoints, although 3.8 mg/kg had adverse effects
(Bhatnagaretal., 1982).
Studies useful for determining the threshold for toxicity
of organic mercury sources to ruminants have not been con-
ducted since 1980. The previous NRC publication (NRC,
1980) reviewed five studies in ruminants and arrived at a
dietary level of 2 mg/kg as safe for all species.
A study was conducted in which brook trout were raised
for three generations over a 144-week period and exposed to
six levels of methylmercury ranging from 0.01 to 2.93 |ig
Hg/L (McKim et al., 1976). At 0.93 pg Hg/L, second genera-
tion trout developed deformities and most females eventu-
ally died. At mercury levels of 0.29 pg/L and below, sur-
vival, growth, and reproduction were normal. In general, fish
at higher trophic levels are more tolerant to mercury than
those at lower trophic levels (Johnston and Savage, 1991).
Effect of Mercury on Reproduction
Methylmercury alters reproductive success in both males
and females. In males, mercury exposure results primarily in
impaired spermatogenesis, decreased sperm motility, and
degeneration of seminiferous tubules. In females, mercury
exposure induces abortions, increases fetal resorption and
malformations, and impairs neurodevelopment.
The placenta acts as a barrier for the transport of inor-
ganic mercury to the fetus, but organic mercury is trans-
ported efficiently. The developing fetal brain is the most
sensitive target for the toxic effects of methylmercury
(Yoshida, 2002). Methylmercury toxicity in the fetus is
often referred to as "fetal Minamata disease" because the
syndrome was first described following a mercury contami-
nation disaster in Minamata, Japan, that affected thousands
of people (NRC, 2000). This syndrome is characterized by
microcephaly, degeneration and trophy of cortical struc-
tures, loss of cellularity in the cerebrum and cerebellum, a
reduction in myelin, ventricular dilation, gliosis, and disor-
ganization of the brain layers. Newborns suffer from sei-
zures, spasticity, blindness, and severe learning deficits. A
similar syndrome has been described in rats, mice, ham-
sters, guinea pigs, cats, and monkeys.
Methylmercury causes developmental effects following
oral exposure during gestation, lactation, or postweaning,
but the outcome of prenatal exposure is most severe (Nielsen
and Andersen, 1995). In rodents, one study found subtle be-
havioral changes in the offspring of rats at a dose of 0.008
mg Hg/kg BW/day. The NOAEL in this study was 0.004
mg/kg/day (Bornhausen et al., 1980). The reference dose for
safe maternal daily dietary intake of methylmercury has been
set at 0.0001 mg/kg BW (EPA, 2001).
Factors Influencing Toxicity
The fetus and neonate are most sensitive to the toxic ef-
fects of methylmercury. Males of some species are more sen-
sitive to mercury toxicity than females. Animals with re-
duced renal capacity due to aging or renal disease are also
more susceptible (Zaiups and Lash, 1994).
Selenium protects against acute nephrotoxicity induced
by inorganic or organic mercury. Inorganic forms of sele-
nium appear to be more effective than organic forms. In
chickens, selenium also protects against toxicity of organic
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MERCURY
255
mercury to the seminiferous epithelium (Maretta et al.,
1995). Possible mechanisms include redistribution of mer-
cury, competition by selenium for mercury-binding sites,
formation of a mercury-selenium complex that diverts mer-
cury from sensitive targets, and prevention of oxidative dam-
age by increasing selenium available for the selenium-de-
pendent glutathione peroxidase (Chapman and Chan, 2000).
High levels of dietary zinc protect against the nephro-
toxic effects of mercury. Zinc-induced metallothionein binds
mercury in the renal cortex and shifts the distribution of
mercury away from the more sensitive epithelial cells in the
proximal tubules (Zalups and Lash, 1994). Conversely, the
nephrotoxicity of mercury is exacerbated in zinc-deficient
animals. In the zinc-deficient state, less mercury accumu-
lates in the kidneys, but the toxicity is greater.
Vitamin E decreases the toxicity of methylmercury, prob-
ably by protection against oxidation (Kling et al., 1987).
Vitamin C has been shown to be protective against meth-
ylmercury toxicity in some studies, but to enhance toxicity
in others (Chapman and Chan, 2000).
TISSUE LEVELS
The enrichment of different tissues in mercury depends
on its form. Inorganic forms of mercury accumulate in kid-
ney and liver, with considerably lower levels in muscle. Most
organic forms of mercury distribute uniformly across tissues,
including muscle. Phenylmercury distributes similarly to
mercuric sources, being highest in kidney and liver, but low
in muscle (Kosutzka et al., 2002; Marettova et al., 2003).
Regardless of the form, accumulation of mercury in the
tissues of animals is relatively linear over the range from back-
ground levels to levels that are toxic for the animal (Table 20-
2). However, the rate of accumulation of mercury in muscle of
poultry and livestock is much greater for methylmercury than
inorganic forms of mercury. Accumulation of mercury in tis-
sues takes many months to plateau, and older animals usually
have higher levels than younger animals. Once mercury has
accumulated in tissues, its depletion occurs very slowly so
that depuration by feeding clean feed and providing clean
water has little value. Regardless of the form of mercury, di-
etary levels that are safe for the animal result in levels in
muscle that would cause toxicity in humans.
The accumulation of mercury in the eggs of hens fed
methylmercury reaches a plateau in about 4 weeks, and
higher concentrations are found in the albumen than in the
yolk (March et al., 1983). The shell contains relatively low
amounts of mercury.
In fish, the accumulation of mercury increases with age
and size of the fish. The kidney, spleen, and liver accumulate
the highest level of mercury, followed by the gill, gonad,
brain, and then muscle (McKim et al., 1976; Sweet and
Zelikoff, 2001).
Chelation therapy is presently the treatment of choice for
reducing the body burden of inorganic mercury, but is largely
ineffective for organic mercury. Efficacious chelators con-
tain sulfhydryl groups that can bind mercury and compete
with its binding to sulfhydryl groups in body tissues. BAL,
DMPS, D-penicillamine, and DMSA have been used to mo-
bilize tissue stores (NRC, 2000).
MAXIMUM TOLERABLE LEVELS
The maximum tolerable level of mercury is defined as the
dietary level that, when fed for a defined period of time, will
not impair accepted indices of animal health or performance.
Inorganic Mercury
Acute exposure to soluble forms of inorganic mercury at
1 mg/kg BW is tolerated without morbidity in those
nonruminant species examined, but future development of
neurological signs cannot be excluded. Chronic consump-
tion of diets containing soluble forms of inorganic mercury
of 0.2 mg/kg is tolerated by rodents, poultry, and pigs. In-
soluble forms of mercury are tolerated at considerably higher
levels. Given the lack of studies using ruminant species and
the possibility of greater bioavailability of inorganic mer-
cury due to methylation in the rumen, no recommendation
on safe levels of inorganic mercury for ruminants can be
given at this time.
Organic IVIercury
Methylmercury at 0.5 mg Hg/kg BW/day is tolerated over
short periods of time by rodents. Assuming a food intake of
lOg/lOOg BW, this dose is equivalent to 5.0 mg Hg/kg diet.
Because information is not generally available for other spe-
cies, 5.0 mg Hg/kg diet is suggested as a safe level for acute
exposure (10 days or less) for other mammals and birds, al-
though future development of neurological signs cannot be
excluded.
Chronic consumption of methylmercury at 1 mg Hg/kg diet
is tolerated by poultry and salmon. The 1980 Mineral Toler-
ances publication (NRC, 1980) established a dietary level of 2
mg/kg as safe for swine and ruminants. Given that little rel-
evant research on these species has been conducted since the
previous report, no changes are made to this recommendation.
Methylmercury at 0.1 mg Hg/kg BW is tolerated in
nonreproducing rodents and cats when consumed chronically.
In all studies reviewed, rodents, nonhuman primates, and cats
tolerated 0.005 mg HG/kg BW/day during reproduction.
Trout tolerate water containing 0.29 |Jg/L of methylmer-
cury; however, fish at lower trophic levels may be sensitive
to the toxic effects of mercury at this level.
HUMAN HEALTH
The MRL is the dose that can be ingested daily for a life-
time without a significant risk of adverse effects. The MRL
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256
MINERAL TOLERANCE OF ANIMALS
for mercury was set at 0.0003 mg Hg/kg/day for a 70-kg
person, based on neurodevelopmental outcomes in children
exposed in utero to methylmercury from maternal fish in-
gestion. For pregnant women, the suggestion is not to con-
sume fish containing greater than 0.25 mg/kg (ATSDR,
1999). The UN Food and Agriculture Organization (FAO)
and the World Health Organization (WHO) set the maxi-
mum mercury intake at 0.23 |Jg/kg BW/day in order to suffi-
ciently protect the developing fetus. The reports stressed that
public health authorities should keep in mind that fish play a
key role in meeting nutritional needs in many countries.
Commercial fish sold through interstate commerce that are
found to have levels of methylmercury above an "action
level" of 0.5 mg/kg (established by the FDA) cannot be sold
to the public. Maximum mercury levels in meats and eggs
have been set at 0.05 mg/kg in many countries. The levels of
dietary and water mercury that are tolerated by fish, poultry,
and livestock would result in tissue levels that exceed these
limits. Consequently, standards for mercury levels in feed
and water supplied to animals intended for human consump-
tion should be based on tissue residue levels and not animal
health concerns.
FUTURE RESEARCH NEEDS
Currently, there is insufficient information on the dose-
response relationship between mercury in feedstuffs versus
levels in meat, milk, or eggs at dietary concentrations that
result in food mercury levels of 0.01 to 1.0 mg/kg. Re-
search that identifies the level of mercury in feeds that re-
sult in mercury residue levels of concern for human health
are greatly needed. Though little research has been con-
ducted to determine safe intake levels of organic mercury
for poultry and livestock, this is not of great concern be-
cause tissue residues should limit the maximum permis-
sible mercury levels in animal feeds. However, there is a
need for additional research on safe levels of organic mer-
cury for companion animals, especially cats because of
their high consumption of fish.
SUMMARY
Mercury exists in numerous chemical forms, including
metallic, mercuric, and organic forms. Mercury released into
the environment from natural and anthropogenic sources is in
the inorganic form, but it is metabolized by bacteria in aquatic
environments to organic forms, primarily methylmercury.
Methylmercury is concentrated at each level of the food chain
and is found at high levels in carnivorous fish. Animals are
exposed to organic mercury via their diet and mercuric forms
via accidental consumption of mercury-based medicinals or
from consumption of soil. Methylmercury is more toxic than
inorganic forms because its bioavailability is considerably
greater. The primary dietary source of methylmercury is
fishmeal and other fish products; plant sources contribute little
mercury to the diet. The nervous system is the most sensitive
indication of methylmercury toxicity, whereas the kidney is
most sensitive to mercuric complexes. Levels of mercury in
the diet and water that are tolerated by animals with no appar-
ent effect result in unacceptably high levels of mercury in meat
and eggs for human consumption.
REFERENCES
Allen, P. 1994. Mercury accumulation profiles and their modification by
interaction with cadmium and lead in the soft tissues of the cichlid
oreochromis aureus during chronic exposure. Bull. Environ. Contam.
Toxicol. 53:684-692.
ATSDR (Agency for Toxic Substances and Disease Registry). 1999. Toxi-
cological Profile for Mercury. Atlanta, GA: U.S. Department of Health
and Human Services, Public Health Service.
Ballatori, N., and T. W. Clarkson. 1984. Dependence of biliary secretion of
inorganic mercury on the biliary transport of glutathione. Biochem.
Pharmacol. 33:1093-1098.
Batterham, E. S., T. B. Gorman, and R. Chvojka. 1983. Nutritional value
and mercury content of fish silage for growing pigs. Anim. Feed Sci.
Technol. 9:169-179.
Berntssen, M. H., A. Aatland, and R. D. Handy. 2003. Chronic dietary mer-
cury exposure causes oxidative stress, brain lesions, and altered behaviour
in Atlantic salmon (salmo salar) parr. Aquatic Toxicol. 65:55-72.
Berntssen, M. H., K. Hylland, A. K. Lundebye, and K. Julshamn. 2004.
Higher faecal excretion and lower tissue accumulation of mercury in
wistar rats from contaminated fish than from methylmercury chloride
added to fish. Food Chem. Toxicol. 42:1359-1366.
Bhatnagar, M. K., O. E. Vrablic, and S. Yamashiro. 1982. Ultrastructural
alterations of the liver of pekin ducks fed methyl mercury-containing
diets. J. Toxicol. Environ. Health 10:981-1003.
Bornhausen, M., H. R. Musch, and H. Greim. 1980. Operant behavior per-
formance changes in rats after prenatal methylmercury exposure.
Toxicol. Appl. Pharmacol. 56:305-310.
Bridger. M. A., and J. P. Thaxton. 1983. Humoral immunity in the chicken
as affected by mercury. Arch. Environ. Contam. Toxicol. 12:45^9.
Chang, C. W., R. M. Nakamura, and C. C. Brooks. 1977. Effect of varied
dietary levels and forms of mercury on swine. J. Anim. Sci. 45:279-285.
Chapman, L., and H. M. Chan. 2000. The influence of nutrition on methyl
mercury intoxication. Environ. Health Perspect. 108 (Suppl. l):29-56.
Charbonneau, S. M., I. C. Munro, E. A. Nera, F. A. Armstrong, R. F. Willes,
F. Bryce. and R. F. Nelson. 1976. Chronic toxicity of methylmercury in
the adult cat. Interim report. Toxicology 5:337—349.
Daoust, P. Y., G. Wobeser, and J. D. Newstead. 1984. Acute pathological
effects of inorganic mercury and copper in gills of rainbow trout. Vet.
Pathof 21:93-101.
Eaton, R. D., D. C. Secord, and P. Hewitt. 1980. An experimental assess-
ment of the toxic potential of mercury in ringed seal liver for adult
laboratory cats. Toxicol. Appl. Pharmacol. 55:514—521.
El-Begearmi, M. M., H. E. Ganther, and M. L. Sunde. 1980. Toxicity of
mercuric chloride in Japanese quail as affected by methods of incorpo-
ration into the diet. Poult. Sci. 59:2216-2220.
El-Begearmi, M. M., H. E. Ganther, and M. L. Sunde. 1982. Dietary inter-
action between methylmercury, selenium, arsenic, and sulfur amino
acids in Japanese quail. Poult. Sci. 61:272-279.
Elia, A. C, R. Galarini, M. I. Taticchi, A. J. Dorr, andL. Mantilacci. 2003.
Antioxidant responses and bioaccumulation in ictalurus melas under
mercury exposure. Ecotoxicol. Environ. Safe. 55:162-167.
EPA (U.S. Environmental Protection Agency). 2001. Reference dose for
the chronic oral exposure to methylmercury. Integrated Risk Informa-
tion System (IRIS). Cincinnati, OH: U.S. Environmental Protection
Agency, Office of Health and Environmental Assessment, Environmen-
tal Criteria and Assessment Office.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
MERCURY
257
Fitzhugh, O. G., A. A. Nelson, and E. P. Laug. 1950. Chronic oral toxicities
of mercuric-phenyl and mercuric salts. Arch. Ind. Hyg. Occup. Med.
2:433^42.
Ganther, H. E., and M. L. Sunde. 1974. Effect of tuna fish and selenium on
the toxicity of methylmercury. J. Food Sci. 39:1—15.
Gebel, T., S. Kevekordes, J. Schaefer, H. von Platen, and H. Dunkelberg.
1996. Assessment of a possible genotoxic environmental risk in sheep
bred on grounds with strongly elevated contents of mercury, arsenic and
antimony. Mutat. Res. 368:267-274.
Grissom, R. E., Jr., and J. P. Thaxton. 1985. Onset of mercury toxicity in
young chickens. Arch. Environ. Contam. Toxicol. 14:193—196.
Grissom, R. E., Jr., and J. P. Thaxton. 1986. Interaction of mercury and
water deprivation on the hematology of chickens. J. Toxicol. Environ.
Health 19:65-74.
Harris, H. H., I. J. Pickering, and G. N. George. 2003. The chemical form of
mercury in fish. Science 301:1203.
Hill, C. H. 1990. The effect of dietary mercury on vanadate toxicity in the
chick. Biol. Trace Elem. Res. 23:1 1—16.
Hill, E. F., and C. S. Shaffner. 1976. Sexual maturation and productivity of
Japanese quail fed graded concentrations of mercuric chloride. Poult.
Sci. 55:1449-1459.
Hill, E. F., and J. H. Scares, Jr. 1987. Oral and intramuscular toxicity of
inorganic and organic mercury chloride to growing quail. J. Toxicol.
Environ. Health 20:105-116.
Horvat, M. 1999. Current status and future needs for biological and envi-
ronmental reference materials certified for methylmercury compounds.
Chemosphere 39:1167-1179.
Horvat, M., and A. R. Byrne. 1992. Preliminary study of the effects of some
physical parameters on the stability of methylmercury in biological
samples. Analyst 117:665-668.
IPCS (International Programme on Chemical Safety). 1986. Mercury —
Environmental Aspects; Environmental Health Criteria. Geneva: World
Health Organization.
IPCS. 2003. Elemental Mercury and Inorganic Mercury Compounds.
Geneva: World Health Organization.
Johnson, D. E., E. W. Kienholz, J. C. Baxter, E. Spangler, and G. M. Ward.
1981. Heavy metal retention in tissues of cattle fed high cadmium sew-
age sludge. J. Anim. Sci. 52:108-1 14.
Johnston, J. N., andG. P. Savage. 1991. Mercury consumption and toxicity
with reference to fish and fishmeal. Nutr. Abstr. Rev. (Series A) 61 :74—
116.
Kambamanoli-Dimou, A., A. Kamarianos, and S. Kilikidis. 1991. Transfer
of methylmercury to hens' eggs after oral administration. Bull. Environ.
Contam. Toxicol. 46:128-133.
Kling, L. J., J. H. Soares, Jr., and W. A. Haltman. 1987. Effect of vitamin E
and synthetic antioxidants on the survival rate of mercury-poisoned
Japanese quail. Poult. Sci. 66:325—331.
Kostial, K., D. Kello, S. Jugo, I. Rabar. and T. Maljkovic. 1978. Influence
of age on metal metabolism and toxicity. Environ. Health Perspect.
25:81-86.
Kostial, K., I. Rabar, M. Blanusa, and M. Landeka. 1979. Effect of age on
heavy metal absorption. Proc. Nutr. Soc. 38:251-256.
Kosutzka, E., J. Pribilincova, M. Ledec, and M. Maretta. 2002. The effect
of selenium on mercury retention in the offspring of treated hens. Acta
Vet. (Belgr.) 52:355-360.
Kozak, S., and C. W. Forsberg. 1979. Transformation of mercuric chloride
and methyl mercury by the rumen micro flora. Appl. Environ. Microbiol.
38:626-636.
Lundholm, C. E. 1995. Effects of methyl mercury at different dose regimes
on eggshell formation and some biochemical characteristics of the egg-
shell gland mucosa of the domestic fowl. Comp. Biochem. Physiol. C
Pharmacol. Toxicol. Endocrinol. 110:23—28.
Magos, L. 200 1 . Review on the toxicity of ethylmercury, including its pres-
ence as a preservative in biological and pharmaceutical products. J.
Appl. Toxicol. 21:1-5.
Magos, L., A. W. Brown, S. Sparrow, E. Bailey, R. T. Snowden. and W. R.
Skipp. 1985. The comparative toxicology of ethyl- and methylmercury.
Arch. Toxicol. 57:260-267.
March, B. E., R. Poon, and S. Chu. 1983. The dynamics of ingested methyl
mercury in growing and laying chickens. Poult. Sci. 62:1000-1009.
Maretta, M., E. Marettova, P. Skrobanek, and M. Ledec. 1995. Effect of
mercury on the seminiferous epithelium of the fowl testis. Acta Vet.
Hung. 43:153-161.
Marettova, E., M. Maretta, J. Legal, and P. Nad. 2003. The effect of sele-
nium on phenyl mercury toxicity and mercury retention in chicken. Acta
Vet. (Belgr.) 53:211-217.
Mata, L., L. Sanchez, and M. Calvo. 1997. Interaction of mercury with
human and bovine milk proteins. Biosci. Biotechnol. Biochem.
61:1641-1645.
Mattsson, J. L., E. Miller, J. P. Alligood, J. E. Koering, and S. G. Levin.
1981. Early effects of methylmercury on the visual evoked response of
the dog. Neurotoxicology 2:499—514.
McKim. J. M., G. F. Olson, G. W. Holcombe, and E. P. Hunt. 1976. Long-
term effect of methylmercuric chloride on three generations of brook
trout. J. Fish. Res. Board Can. 33:2726-2739.
McNeil, S. I., and M. K. Bhatnagar. 1985. Ultrastructure of the testis of
pekin ducks fed methyl mercury chloride: seminiferous epithelium. Am.
L Vet. Res. 46:2019-2025.
Naganuma, A., and N. Imura. 1984. Species difference in biliary excretion
of methyl mercury. Biochem. Pharmacol. 33:679-682.
Nielsen, J. B., and O. Andersen. 1991. A comparison ofthe effects of sodium
selenite and seleno-1-methionine on disposition of orally administered
mercuric chloride. J. Trace Elem. Electrolytes Health Dis. 5:245-250.
Nielsen, J. B., and O. Andersen. 1995. A comparison ofthe lactational and
transplacental deposition of mercury in offspring from methylmercury-
exposed mice. Effect of seleno-1-methionine. Toxicol. Lett. 76: 165-17 1.
Niimi, A. J., and G. P. Kissoon. 1994. Evaluation ofthe critical body bur-
den concept based on inorganic and organic mercury toxicity to rain-
bow trout (oncorhynchus mykiss). Arch. Environ. Contam. Toxicol. 26:
169-178.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
NRC. 2000. Toxicological Effects of Methylmercury. Washington, D.C.:
National Academy Press.
Ohi, G., S. Nishigaki, H. Seki, Y. Tamura, and T. Maki. 1976. Efficacy of
selenium in tuna and selenite in modifying methylmercury intoxication.
Environ. Res. 12:49-58.
Palmisano, F., N. Cardellicchio, and P. G. Zambonin. 1995. Speciation of
mercury in dolphin liver: a two-stage mechanism for the demethylation
accumulation process and role of selenium. Mar. Environ. Res. 40:1—12.
Pathak, S. K., and M. K. Bhowmik. 1998. The chronic toxicity of inorganic
mercury in goats: clinical signs, toxicopathological changes and residual
concentrations. Vet. Res. Commun. 22:131-138.
Paustenbach, D. J., G. M. Bruce, and P. Chrostowski. 1997. Current views
on the oral bioavailability of inorganic mercury in soil: implications for
health risk assessments. Risk Anal. 17:533-544.
Prasada Rao, P. V., S. A. Jordan, and M. K. Bhatnagar. 1989. Combined
nephi'otoxicity of methylmercury, lead, and cadmium in pekin ducks:
metallothionein, metal interactions, and histopathology. J. Toxicol.
Environ. Health 26:327-348.
Pribilincova, J., E. Marettova, J. Kosucky, and M. Maretta. 1996. The effect
of phenyl mercury on reproductive performance in laying hens. Acta
Vet. Hung. 44:377-387.
Rowland, I. R., A. K. Mallett, J. Flynn, and R. J. Hargreaves. 1986. The
effect of various dietary fibres on tissue concentration and chemical
form of mercury after methylmercury exposure in mice. Arch. Toxicol.
59:94-98.
Satoh, M. 1997. Enhanced renal toxicity by inorganic mercury in
metallothionein-nuU mice. J. Pharmacol. Exp. Ther. 283:1529-1533.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
258
MINERAL TOLERANCE OF ANIMALS
Sin, Y. M., Y. F. Lira, and M. K. Wong. 1983. Uptake and distribution of
mercury in mice from ingesting soluble and insoluble mercury com-
pounds. Bull. Environ. Contam. Toxicol. 31:605-612.
Soares, J. H., Jr. 1973. The comparative effect of oral ingestion of methyl
mercury on chicks and rats. Poult. Sci. 52:452^58.
Stankovic, R. K., V. Lee, M. Kekic, and C. Harper. 2003. The expression
and significance of metallothioneins in murine organs and tissues fol-
lowing mercury vapour exposure. Toxicol. Pathol. 31:514—523.
Storelli, M. M., and G. O. Marcotrigiano. 2002. Mercury speciation and
relationship between mercury and selenium in liver of galeus
melastomus from the Mediterranean Sea. Bull. Environ. Contam.
Toxicol. 69:516-522.
Suda, I., and K. Hirayama. 1992. Degradation of methyl and ethyl mercury
into inorganic mercury by hydroxyl radical produced from rat liver mi-
crosomes. Arch. Toxicol. 66:398-402.
Sweet, L. I., and J. T. Zelikoff. 2001. Toxicology and immunotoxicology of
mercury: a comparative review in fish and humans. J. Toxicol. Environ.
Health. B Crit. Rev. 4:161-205.
Tchounwou, P. B., W. K. Ayensu, N. Ninashvili, and D. Sutton. 2003. En-
vironmental exposure to mercury and its toxicopathologic implications
for public health. Environ. Toxicol. 18:149-175.
Thaxton, J. P., J. Gilbert, P. Y. Hester, and J. Brake. 1982. Mercury toxicity
as compared to adrenocorticotropin-induced physiological stress in the
chicken. Arch. Environ. Contam. Toxicol. 11:509-514.
Thaxton, P., C. R. Parkhurst, L. A. Cogburn, and P. S. Young. 1975. Adre-
nal function in chickens experiencing mercury toxicity. Poult. Sci.
54:578-584.
USGS (U.S. Geological Survey). 1992. Mercury, Minerals Yearbook —
2002.
Van Der Veen, N. G., and K. Vreman. 1986. Transfer of cadmium lead
mercury and arsenic from feed into various organs and tissues of fatten-
ing lambs. Neth. J. Agric. Sci. 34:145-154.
Wood, J. M., and H. K. Wang. 1983. Microbial resistance to heavy metals.
Environ. Sci. Technol. 17:82a— 90a.
Yoshida, M. 2002. Placental to fetal transfer of mercury and fetotoxicity.
Tohoku J. Exp. Med. 196:79-88.
Yoshida, M., C. Watanabe, H. Satoh, T. Kishimoto, and Y. Yamamura.
1994. Milk transfer and tissue uptake of mercury in suckling offspring
after exposure of lactating maternal guinea pigs to inorganic or meth-
ylmercury. Arch. Toxicol. 68:174—178.
Zalups, R. K., and L. H. Lash. 1994. Advances in understanding the renal
transport and toxicity of mercury. J. Toxicol. Environ. Health 42: 1^14.
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21
Molybdenum
INTRODUCTION
Molybdenum (Mo) has an atomic number of 42 and an
atomic weiglit of 95.94. Althougli molybdenum is grouped
with tungsten and chromium in the Periodic Table, its chemi-
cal properties resemble only those of tungsten. As a highly
versatile element, molybdenum has various oxidation states
(IMOA, 2002). While the low oxidation states of molybde-
num (2- to 2+) do not occur in biological systems, the 3+ to
6+ states of molybdenum form an array of complexes with
oxygen- or nitrogen-donor ligands and with the halogens.
Molybdate complexes with sulfur-donor ligands are also
common, but complexes with phosphorus- or arsenic-donor
ligands are rare. The 4+ Mo is strongly stabilized by cya-
nide, and forms the most stable sulfide with sulfur (S). The
5+ or 6-1- Mo is found mainly in oxomolybdenum species.
Molybdenum is widely distributed in nature as molybdenite,
wulfenite, ferrimolybdate, jordisite, and powellite. The
United States is the largest producer of molybdenum in the
world. Most molybdenum compounds are derived from mo-
lybdenum trioxide that is generated by roasting molybde-
num disulfide ores. In industry, molybdenum is mainly used
in manufacturing alloys and electronic devices. In human
medicine, molybdenum-containing compounds may be used
to treat dental caries and Wilson's disease, and to lower
blood glucose and free fatty acids (Haywood et al., 1998).
ESSENTIALITY
Molybdenum is required for nitrogen fixation and for the
reduction of nitrate to nitrite in bacteria (Williams and
Fraiisto da Silva, 2002). As a component of aldehyde oxi-
dase, sulfite oxidase, and xanthine oxidase, molybdenum is
probably essential for all higher animals. However, molyb-
denum requirements are extremely low, and clear signs of
deficiency have been demonstrated in very few species. In
the three enzymes where it serves as a cofactor, molybde-
num is present as molydopterin, a mononuclear molybde-
num atom coordinated to the sulfur atoms of a pterin deriva-
tive (Johnson et al., 1980). It helps in catalyzing the oxida-
tion or metabolism of aldehydes, sulfite, sulfur-containing
amino acids, purines, pyrimidines, and pteridines (Kisker et
al., 1997). Deficiency of these enzymes or the molybdenum
cof actors (Johnson, 1997) causes severe metabolic disorders
or death in humans (Turnlund et al., 1995). Amino acid in-
tolerances and irritability were shown in a patient with
Crohn's disease receiving total parenteral nutrition, and the
condition was improved by treating the person with ammo-
nium molybdate (Abumrad et al., 1981). Primary molybde-
num deficiency was reported by Anke et al. (1985) in goats
fed a semi-purified diet containing 24 \ig of Mo/kg. These
goats showed depressed growth, impaired reproduction, and
increased mortality of kids and mothers. Secondary molyb-
denum deficiency was produced in chicks fed low molybde-
num diets containing high levels of tungsten (Nell et al.,
1980; Topham et al., 1982a, b). The signs were anemia,
growth retardation, and decreased tissue molybdenum lev-
els; xanthine dehydrogenase activity; and the conversion of
xanthine to uric acid. The anemia was probably related to the
ferroxidase activity of xanthine oxidase in the intestinal
mucosa and liver. Both pigs (Anke et al., 1978) and calves
(Gengelbach and Spears, 1998) fed semi-purified diets have
responded to molybdenum supplements. The effect of mo-
lybdenum on protein synthesis was positive in trout, but
negative in rats (IMOA, 2002). Because of the ability of
molybdenum to change between 4+ and 6+ and the redox
potential link to electron acceptors such as cytochrome C
and NAD, the molybdenum-containing enzymes may be
important in regulating cellular peroxide and superoxide
radicals. In turn, the free radicals are related to oxidative
injuries in the body and inflammatory response to trauma
such as invasion of nematodes in grazing animals (Suttle
et al., 1992). As requirements for molybdenum by goats, rats,
chicks, and perhaps other species are no higher than 0.2 mg/kg
of diets (McDowell, 2003), molybdenum deficiency is rare
in animals fed practical diets. The molybdenum require-
262
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MOLYBDENUM
263
ment of adult humans is approximately 25 |Jg/day, but the
actual daily molybdenum intakes of German and Mexican
adults are 3 to 8 times higher than that level (Holzinger et al.,
1998).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Total molybdenum contents in feeds, feces, water, urine,
and tissues are often determined using colorimetric methods
or atomic absorption spectroscopy. After the samples are dry
ashed in a muffle furnace or wet ashed in heated, concen-
trated sulfuric acid, 4-methyl-l,2-dimercaptobenzene is used
to produce a molybdenum-mercaptide complex under acidic
conditions (Johnson, 1988). After the complex is extracted
into an organic solvent, it is quantified by absorbance at 680
nm. To reduce the interferences from ferric iron and tung-
sten, KI and tartrate are added into the mixture, respectively.
Ahmed and Haque (2002) have recently reported a rapid,
ultra-sensitive, and highly selective spectrophotometric
method for the determination of trace amounts of molybde-
num, using 5,7-dibromo-8-hydroxyquinoline. Their proce-
dure does not require an extraction step. Alternatively, mo-
lybdenum can be detected at picomole levels by graphite
furnace atomic absorption spectroscopy (Johnson, 1988).
Because molybdenum carbides may accumulate on the walls
of the graphite furnace and thus cause memory effects (arti-
ficially elevated levels), it is better to ash the samples at low
temperature and to add a burnoff cycle between analyses. In
addition, molybdenum can be determined by inductively
coupled plasma atomic emission spectrometry after the
samples are dry-ashed at 450°C and diluted in 2.5 percent
HCl (Holzinger et al., 1998).
REGULATION AND METABOLISM
Absorption and Metabolism
Absorption of molybdenum takes place in the stomach
and throughout the small intestine of rats (Nielsen, 1996).
The water-soluble molybdenum, such as the sodium or am-
monium salts of 6+ Mo and the molybdenum in high molyb-
denum herbage, is readily absorbed by ruminants (Grace and
Suttle, 1979). But, the disulfide form {4+ Mo) is poorly ab-
sorbed. After an oral dose of '^Mo, the peak blood levels of
molybdenum were detected within 4 hours in pigs, but not
until 96 hours in cattle (Bell et al., 1964). Although the aver-
age absorption coefficient of stable or radioactive isotopes
of molybdenum is 20 to 30 percent, the actual absorption
rate of dietary molybdenum can be affected by species, age
of animals, and levels of molybdenum and other nutrients in
diets (Miller et al., 1972; Friberg and Lener, 1986; Turnlund
et al., 1995). In the small intestine, the absorption of molyb-
denum across the mucosa is an active, carrier-mediated pro-
cess that is also used by sulfate (Mason and Cardin, 1977).
This gives rise to a possible antagonism between molybde-
num and sulfate in their intestinal absorption and/or renal
reabsorption. The interaction may be used to explain why
increasing dietary sulfur decreased absorption or retention
of molybdenum in sheep (Dick, 1956; NRC, 1980). It may
also explain why ruminants are susceptible to molybdenum
toxicosis because dietary sulfate is reduced to sulfide in the
ruminal environment (Underwood and Suttle, 1999) so that
essentially no sulfur leaves the rumen as sulfate to interfere
with molybdenum absorption. However, the extremely high
absorption coefficients of molybdenum in humans, up to >90
percent, at both low and high dietary intakes (22 versus 467
mg/day) (Turnlund et al., 1995) suggest a largely passive
and nonsaturable mechanism for molybdenum absorption.
Absorbed molybdenum is transported in the blood, at-
tached to proteins in the red blood cells and as free ionic
molybdate in the plasma (Versieck et al., 1981). In the liver
of preruminant calves, 40, 30, 23, and 7 percent of total tis-
sue molybdenum was distributed in the nuclei, cytosol, large
granule, and microsome, respectively (Jenkins, 1989). In-
creasing dietary copper from 10 to 1,000 mg/kg of diet re-
sulted in a decrease in liver molybdenum from 2.7 to 0.7 mg/kg
of dry matter, mainly in the nuclei. In laboratory species,
approximately 36 to 90 percent of molybdenum was excreted
through urine, and the output increased with the exposure
(Vyskocil and Viau, 1999). Feces may serve as a major ex-
cretion pathway in ruminants fed diets with high sulfur and
high coppertmolybdenum ratios (Grace and Suttle, 1979) or
diets with high molybdenum and "normal" levels of sulfur
and copper (Pott et al., 1999). Milk is an additional molyb-
denum excretion pathway in lactating animals. The reported
biological half-lives of molybdenum vary considerably: 0.4
to 0.6 hour in liver and kidney of rabbits, 20 hours in the
whole body of cattle, several days in the tissues of rats, and
several weeks in humans (Vyskocil and Viau, 1999; IMOA,
2002). According to Lesperance et al. (1985), plasma mo-
lybdenum is a better indicator of molybdenum intake than
tissue copper levels, and urinary molybdenum may be used
to estimate molybdenum intake in the field. However, uri-
nary excretion of molybdenum may not remain linear with
high levels of dietary molybdenum intake (Pott et al., 1999).
IVIetabolic Interactions, Regulations, and IVIechanism of
Toxicities
As there is little or no regulation of molybdenum uptake
in simple-stomached species, body molybdenum balance is
controlled primarily by urinary excretion (Johnson, 1997).
Due to the chemical similarities, tungsten can compete with
molybdenum at sites of transport, uptake, and utilization.
Thus, tungsten can interrupt or replace the incorporation of
molybdenum into target proteins, producing nonfunctional
enzymes. Because concentrations of tungsten in water, feeds,
and the environment are low, this antagonism has been
shown only under experimental conditions (Nell et al., 1980).
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MINERAL TOLERANCE OF ANIMALS
In contrast, the interaction among molybdenum, copper,
and sulfur is of great practical significance in grazing rumi-
nants (Spears, 2003). When these animals ingest moderate
to high levels of molybdenum from pasture, a concomitant
high intake of sulfur induces copper deficiency (Ward,
1978). The disorder was initially attributed to the formation
of insoluble copper-molybdenum-sulfur complexes (mono-,
di, tri-, and tetra-thiomolybdates) in the rumen (Gooneratne
et al., 1989; Suttle, 1991). However, Allen and Gawthorne
(1987) argued for the importance of an association of
thiomolybdates and copper with proteins in the solid digesta,
suggesting that the molybdenum-copper antagonism was not
a direct action, but a consequence of molybdenum affinity
for sulfide generated within the rumen. After ruminal
administration of ^'Mo-labeled compounds, tri- and tetra-
thiomolybdates were found in the solid phase of ruminal,
duodenal, and ileal digesta, whereas di- and tri-thiomolybdates
were detected in the plasma of sheep (Price et al., 1987).
Likely, the inhibition of copper absorption was mediated by
tri- and tetra-thiomolybdates, and the postabsorptive effect
on copper metabolism was exerted by di- and tri-
thiomolybdates. In summary, absorbed thiomolybdates may
affect copper metabolism in the following ways: (1) enhance
biliary excretion of copper from liver stores; (2) reduce trans-
port of available copper for biochemical synthesis by bind-
ing copper to plasma albumin; and (3) remove copper from
cupro-enzymes (Suttle, 1991; Spears, 2003). Obviously, the
presence of the sulfide-generating microbes in the rumen
renders cattle and sheep susceptible to the molybdenum-
copper-sulfur imbalance.
In the presence of adequate dietary copper, liver cop-
per or plasma ceruloplasmin of rats was not decreased
by feeding 500 mg Mo/kg of diet for 70 days (Igarza et
al., 1999). High levels of dietary sulfur increase urinary
excretion of molybdenum and decrease tissue molybde-
num deposition. Furthermore, molybdenum can also in-
teract with phosphorus, iron, and other elements (IMOA,
2002). There was only a slight effect of supplemental
molybdenum (10 mg/kg as sodium molybdate) on the
metabolism of ^^Se-selenomethionine in ram lambs
(White et al., 1989).
Generally speaking, molybdenum toxicosis may be
caused by either high levels of molybdenum intake or mod-
erate levels of molybdenum intake combined with low lev-
els of copper or low copper:molybdenum ratios. In most
cases, molybdenosis resembles secondary copper defi-
ciency. Some of the clinical signs may be explained by the
deficiency of copper-containing enzymes: low tyrosinase
activity causing rough hair coat, achromotrichia, and the
loss of crimp in the wool (steely wool); low ferroxidase
activity causing anemia; and low lysine oxidase activity
causing skeletal and/or collagenous disorders (NRG, 1980).
The biochemical changes of molybdenosis, such as reduced
plasma ceruloplasmin, are related to impaired copper me-
tabolism.
SOURCES AND BIOAVAILABILITY
Sandy soil contains low molybdenum, whereas marine
origin soil contains high molybdenum, ranging from 0.1 to
20 mg/kg on a dry basis (Underwood and Suttle, 1999). The
extractable molybdenum in the soil, normally 10 percent of
total molybdenum, increases with increasing soil pH. As
excessively high pasture molybdenum concentrations (up to
200 mg/kg) occur only on alkaline soils, molybdenum toxi-
cosis is not normally seen in animals grazing pasture on acid
(pH <6.5) and well-drained soils (McDowell, 2003). The
median value of molybdenum in pasture was 1.1 mg/kg (dry
basis) for 20 improved hill pasture sites in Scotland, with the
highest concentration at 60 mg/kg (Suttle and Small, 1993).
In areas with industrial contamination, herbage values of
molybdenum were up to 23 1 mg/kg (Gardner and Hall-Patch,
1962). In some areas of Northern California, alfalfa and other
legumes contain low levels of molybdenum and often do not
contain sufficient molybdenum to maximize forage yield,
whereas forages grown in much of California south of a line
between San Francisco and Lake Tahoe may accumulate too
much molybdenum and can produce molybdenosis in live-
stock (Meyer et al., 1999). The commonly detected concen-
trations of molybdenum (mg/kg DM) in various plant
sources are as follows: cereal grains and straws, 0.2 to 0.5;
grass, 0.2 to 0.8; clovers and other legumes, 0.5 to 1.5; and
vegetable protein concentrates, 0.5 to 2.0 (McDowell, 2003).
Apples and bilberry heather seem to contain molybdenum
<0.1 mg/kg (Anke et al., 1985). In plant feeds, molybdenum
exists as water-soluble sodium and ammonium salts and
water-insoluble molybdenum oxide, calcium molybdate, and
molybdenum sulfide (MoSj) (NRC, 1980). Animal tissues
and milk usually contain low levels of molybdenum, mainly
as molybdopeterin, but can be elevated by high dietary con-
centrations (Anke et al., 1985). In mixed diets for humans,
molybdenum concentrations range from 0.19 to 0.63 mg/kg
dry matter (Holzinger et al., 1998). Water from different
parts of the world contains 0.1 to 4 |jg of Mo/L, but the level
can be as high as 25 mg/L in the groundwater of Colorado
(IMOA, 2002). Seawater contains approximately 8 |ag of Mo/
L. Sodium molybdate is the only accepted source of molyb-
denum by the U.S. animal feed industry to be used when
copper toxicosis is suspected.
TOXICOSIS
Molybdenosis is produced by either high molybdenum
intakes alone (>100 mg/kg) or moderately high molybde-
num intakes concomitant with low dietary copper levels (<5
mg/kg) or low dietary copper:molybdenum ratios (<2:1).
Mild molybdenosis may be identified by only biochemical
changes such as increases in xanthine oxidase activity or
blood uric acid. Severe molybdenosis is manifested by clini-
cal signs, and even death. In most cases, the molybdenum
toxicosis is largely secondary to copper deficiency or
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MOLYBDENUM
265
hypocuprosis, and it may be reversed by supplemental cop-
per. Because of the interactions of molybdenum, sulfur, and
copper, it is necessary to consider dietary levels and body
status of both copper and sulfur in defining or comparing
molybdenum toxicity in various species (Ward, 1978).
Single Dose and Acute
When administrated orally, the LD^q of molybdenum tri-
oxide and ammonium molybdate was 125 and 370 mg of
Mo/kg of body weight for rats, respectively. The LD|qq of
ammonium molybdate was 1,200, 1,020, and 1,310 mg of
Mo/kg for guinea pigs, rabbits, and cats, respectively
(Venugopal and Luckey, 1978). For soluble molybdenum
compounds, the lethal doses for repeated oral administra-
tions ranged from 60 to 333 mg of Mo/kg of BW/day for
rats, mice, guinea pigs, and rabbits (Vyskocil and Viau,
1999), but only 3 mg of Mo/kg of BW/day for steers (Cook
et al., 1966). Signs of acute molybdenosis include gas-
trointestinal irritation, diarrhea, coma, and death from car-
diac failure (Opresko, 1993). Injuries in the liver and kidney,
sometimes in the adrenals and spleen, may also occur in the
intoxicated animals.
Reid (2002) found that molybdenum was relatively non-
toxic to juvenile Kokanee salmon, as the 96-hour LCjq was
greater than 2,000 mg of Mo/L (sodium molybdate). Acute
sublethal molybdenum exposure had little effect on oxygen
consumption or plasma lactate, sodium, and Cortisol concen-
trations at rest or active states in kokanee. Similarly,
Hamilton and Buhl (1990) observed no mortality or any overt
sign of stress in Chinook salmon and Coho salmon exposed
to 78 to 1,000 mg of Mo/L. They suggested that the 96-hour
LCjQ exceeded 1,000 mg of Mo/L, regardless of the water
dilution quality or the life stage for these species. Little acute
toxicosis of sodium molybdate was shown in selected salt-
water organisms including the pink shrimp, the mysid
shrimp, and the sheepshead minnow, and the calculated 96-
hour LCjQ exceeded 1,000 mg of Mo/L (Knothe and Van
Riper, 1988). For bluegill and rainbow trout, the 96-hour
LDjo (mg/L) was 65 to 87 for MoO,, 120 to 157 for ammo-
nium molybdate, and 6,790 to 7,340 for sodium molybdate
(IMOA, 2002).
Chronic
Anorexia and body weight loss are typical signs of
chronic molybdenosis in cattle. When these animals graze
on "teart" pasture containing 20 to 100 mg of Mo/kg dry
matter (normal: 3 to 5 mg of Mo/kg)(Underwood and Suttle,
1999), scours may occur within 24 hours (Lloyd et al., 1976).
Prolonged high molybdenum intake in cattle also produced
anemia, achromotrichia, posterior weakness, skeletal de-
formities, and reproductive abnormalities (Venugopal and
Luckey, 1978). These signs were shown in early studies with
various types of cattle fed molybdenum from 6.2 to 400 mg/kg
of diets (NRC, 1980). Unless indicated otherwise, sodium
molybdate was used as the source of molybdenum in the
following toxicity studies.
Severe molybdenum toxicosis in weanling heifers fed 100
mg of Mo/kg of diet (Table 21-1) for 336 days was mani-
fested as scouring, achromotrichia, anemia, weight loss, and
31 percent mortality within 2 weeks after the study began
(Lesperance et al., 1985). Secondary copper deficiency was
induced in beef heifers by feeding 7 to 16 mg of Mo/kg of
diet (as molybdenumxopper ratio, 2.5:1) in the presence of
0.3 percent of sulfur and 3 to 6 mg of Cu/kg (Arthington et
al., 1996a,b). The molybdenum-supplemented animals also
showed decreased plasma copper and ceruloplasmin and in-
creased plasma fibrinogen and blood neutrophil numbers.
Supplementing 5 mg of Mo/kg of dry matter in either cop-
per-adequate or -deficient diets did not dramatically alter the
specific immunity of the stressed cattle (Ward and Spears,
1999). When 5 -week-old Holstein calves were given water
containing 1, 10, or 50 mg Mo/L (as ammonium molybdate)
for 21 days, liver copper content was reduced in the calves
receiving the highest level of molybdenum (Kincaid, 1980).
The calculated proportion of plasma copper as ceruloplas-
min was reduced from 61 to 43 percent with increases in
water molybdenum levels, indicating a reduced copper up-
take by tissues from the plasma. In a semi-purified diet that
contained 1.1 mg of copper and 1.1 mg of Mo/kg of dry
matter for calves, supplementing 5 mg of Mo/kg depressed
humoral immune responses and erythrocyte superoxide
dismutase activity, compared with those supplemented with
10 mg of Cu/kg (Gengelbach and Spears, 1998). However,
these effects were not significant in the presence of 5 mg of
Cu/kg. Supplementing 5 mg of Mo/kg of diet to 7-month-
old steers for 245 days reduced plasma copper and cerulo-
plasmin concentrations, and erythrocyte superoxide
dismutase activity in the non-copper-supplemented steers,
but had no effect on performance or carcass quality (Ward
and Spears, 1997). Steers exhibited no further changes in
copper status when dietary molybdenum was increased from
5 to 10 mg/kg of diet in the presence of 2.7 g of S/kg of diet
(Gengelbach, 1994). Compared with the controls, heifers
or steers showed no adverse response after grazing
bahiagrass pasture treated with high molybdenum biosolids
(molybdenum loads from 0.27 to 2.56 kg/ha) for 6 months
(Tiffany et al., 2000, 2002).
Sheep are also susceptible to molybdenosis (NRC, 1980).
Their clinical signs of chronic molybdenum toxicosis are
essentially secondary hypocuprosis: reduced crimp and pig-
mentation of wool, anemia, alopecia, and depressed weight
gain. When sheep were fed a basal diet containing 1.0 g of
sulfur and 0.5 mg of molybdenum per kg of diet, supple-
menting 4 mg of molybdenum and 3 g of sulfur per kg of diet
reduced copper bioavailability by 40 to 70 percent, but the
addition of only molybdenum had no effect at all (Suttle,
1975). Increasing molybdenum (as ammonium molybdate)
from 0.4 to 8.4 mg/kg of dry matter in the diets for wethers
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266
MINERAL TOLERANCE OF ANIMALS
resulted in reduced daily gains, poor feed efficiency, and
decreased solubility of copper and molybdenum in the ru-
men, along with increased liver and kidney molybdenum
contents (Ivan and Veira, 1985). There was no effect on liver
copper content. Supplementing molybdenum (as tetra-
thiomolybdate) at 10 to 40 mg of Mo/kg of dry matter into a
copper- and chromium-deficient diet for male goats exacer-
bated the copper deficiency (Aupperle et al., 2001). In con-
trast, Anke et al. (1985) reported that goats tolerated diets
with 1 g of Mo/kg of diet, and they suggested that this high
tolerance was not due to insufficient molybdenum absorp-
tion or related to copper metabolism.
Other ruminants and most nonruminants are resistant to
molybdenum toxicity (NRC, 1980). Mule deer fed molybde-
num up to 1 g/day showed no clinical signs (Nagy et al., 1975).
Growing swine showed no apparent adverse response to 27
mg of Mo/kg of feed (Gipp et al., 1967), 50 mg of Mo/kg of
feed (Kline et al., 1973), or 1 g of Mo/kg of diet (Davis, 1950),
whereas the growth retardation effect of 1.5 g of Mo/kg of
diet (in the presence of 17.8 mg of Cu/kg of diet) was re-
versed by addition of 0.4 percent sulfate (Standish et al.,
1975). No deleterious effects were observed in horses graz-
ing the "teart" pasture that caused diarrhea in cattle
(McDowell, 2003), but an early study indicated an associa-
tion with rachitis in foals and yearlings grazing on pasture
containing 5 to 22 mg of Mo/kg (Walsh and O'Moore, 1953).
Several chick studies indicated that 100 mg of Mo/kg of feed
was safe (Davies et al., 1960), 200 to 300 mg of Mo/kg of
feed caused growth depression (Kratzer, 1952), 4 g of Mo/kg
of feed caused anemia (Arthur et al., 1958), and 8 g of Mo/kg
of feed caused 61 percent mortality (Davies et al., 1960). In
laying hens, 500 mg of Mo/kg of feed caused decreased
hatchability and 1 g of Mo/kg of feed reduced egg produc-
tion (Lepore and Miller, 1965).
Rabbits fed molybdenum at Ig/kg of feed or higher levels
may show anorexia, loss of weight, alopecia, a slight derma-
tosis, anemia, splayed front legs, and premature deaths
(Arrington and Davis, 1953). The adverse hematological ef-
fects of high molybdenum intakes in rabbits are fairly con-
sistent (Vyskocil and Viau, 1999). Feeding male New
Zealand rabbits (1.5 to 2.7 kg) a diet containing 4.5 g of
sodium molybdate/kg or 0.3 percent of molybdenum ion for
25 to 31 days resulted in thyroidal hypofunction
(Widjajakusuma et al., 1973). The signs include reduced
plasma thyroxine concentration, thyroxine secretion rate, and
follicular epithelial cells in the gland, and these impairments
may be the major causal factor for the reduced feed intake in
the molybdenotic rabbits. There was also a direct role of the
molybdate ion in the degeneration of the thyroid gland.
Given ammonium molybdate in drinking water at 500 mg/kg
of BW/day, male albino rats (60-70 g) showed growth re-
tardation, altered activities of phosphatases in tissues, and
increases in the basophilic substances in the cytoplasm of
the liver cells (Bandyopadhyay et al., 1981). A high protein
diet partially reversed these changes. However, serum ceru-
loplasmin activity in rats was not affected by 500 mg of
Mo/kg diet, with supplemental copper at 40 mg/kg of diet
(Igarza et al., 1999). When juvenile Kokanee salmon (20-
70 g) were given molybdenum at 25 mg/L or higher levels
for 7 days, there were increases in ventilation, post exer-
cise loss of equilibrium, exercised-induced delayed mor-
tality, and accumulation of molybdenum in gills and liver
(Reid, 2002).
Reproduction
After male rats were administrated 30 or 50 mg of sodium
molybdate/kg BW/day for 60 days, there were significant
decreases in the absolute or the relative weights of epid-
idymides, seminal vesicles and ventral prostate, sperm
motility and count, and testicular sorbitol dehydrogenase,
but increases in testicular lactate dehydrogenase and y-
glutamyl transpeptidase, tissue molybdenum accumulation,
spermoatozoa abnormalities, and male-mediated
embryotoxicity (Pandey and Singh, 2002). Given ammonium
molybdate in drinking water at 500 mg/kg BW, male albino
rats (60-70 g) showed elevated serum levels of luteinizing
hormone, follicle stimulating hormone, prolactin, and Corti-
sol (Bandyopadhyay et al., 1981). Given deionized water
containing 10 or 100 mg of Mo/L from weaning to 21 days
of gestation, female rats showed a prolonged estrous cycle,
lower body weight gain, delayed fetal esophageal develop-
ment, lower transfer of fetal hemopoiesis to bone marrow,
and delayed myelination in the spinal cord, along with in-
creased fetal resorption (Fungwe et al., 1990). As mentioned
earlier, heifers fed a low copper (4.5 mg/kg) diet supple-
mented with 5 mg of Mo/kg produced calves that became
more susceptible to diseases than those born to heifers that
were not supplemented with molybdenum (Gengelbach
etal., 1997).
Factors Influencing Toxicity
Toxicity of molybdenum, at a given level of exposure,
depends on species, body status or dietary levels of copper
and sulfur, and the chemical form of molybdenum. Both
cattle and sheep are most sensitive to molybdenum toxicity,
whereas other ruminants, nonruminants, and fish are fairly
resistant to molybdenosis. The low tolerance to molybde-
num in cattle and sheep may be partially explained by the
reduction of digesta sulfate to sulfide in the rumen and the
formation of thiomolybdates that are more toxic than molyb-
date (Underwood and Suttle, 1999; Spears, 2003). Compara-
tively, sheep are somewhat less susceptible to molybdenum
toxicity than cattle, probably due to a lower ceruloplasmin
turnover (NRC, 1980).
As molybdenosis is associated with the dysfunctions of
several copper-containing enzymes such as tyrosinase,
ferroxidase, and dopamine beta hydroxylase (NRC, 1980),
dietary copper levels and body copper status are critical to
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MOLYBDENUM
267
the incidence and severity of molybdenum toxicosis. Given
adequate or iiigii dietary copper, many species, even cattle,
can tolerate relatively high levels of molybdenum. On the
other hand, the antagonistic interaction between molybde-
num and copper can be used to prevent copper toxicosis.
Supplemental or intravenous administration of molybdate
compounds, along with SO^, has been used to prevent cop-
per poisoning in sheep (MacLachlan and Johnston, 1982;
Olson et al., 1984; Humphries et al., 1986).
Inorganic sulfate supplements seem to protect against
molybdenum toxicity. However, Underwood and Suttle
(1999) suggested that this protection might be confined to
nonruminants, via reducing intestinal molybdenum absorp-
tion and increasing urinary molybdenum excretion. They
considered the reported molybdenum reduction in sheep
given sulfur supplement an artifact and argued that the si-
multaneous addition of molybdenum and sulfur actually ex-
acerbated the molybdenum-induced impairment of copper
metabolism (Suttle, 1975). A high protein diet can partially
alleviate molybdenum toxicosis, probably via the metabo-
lism of sulfur-containing amino acids (Igarza et al., 1999).
Highly soluble trioxide and ammonium molybdates are
much more toxic than the insoluble compounds such as mo-
lybdenum disulphide, metal, and dioxide (Vyskocil and
Viau, 1999). Ammonium molybdate seems to be more toxic
to chickens than sodium molybdate (Davies et al., 1960).
Male rats seem to tolerate less molybdenum than female rats
(Vyskocil and Viau, 1999). Other dietary factors such as
manganese, zinc, iron, lead, and tungstate and the chemical
forms of molybdenum also affect molybdenum toxicity
(NRC, 1980).
TISSUE LEVELS
Concentrations of molybdenum in tissues, blood, eggs,
and milk vary with molybdenum intakes (Table 21-2), and
the fluctuations are modulated by concomitant inorganic sul-
fate and copper levels (Arthur et al., 1958; NRC, 1980).
Under normal conditions, liver molybdenum concentrations
of Fallow deer, sheep, pig, cow, and humans fall between 2
and 3 mg/kg of dry matter, whereas the concentration is
lower (0.62 mg/kg) for Roe deer and much higher for horses
(8 mg/kg) (Anke et al., 1985). In many species, kidney con-
tains approximately half the molybdenum of liver, but
chicken liver and kidney have similar molybdenum contents
(~ 4 mg/kg) that are higher than the molybdenum content in
muscle (0.14 mg/kg; IMOA, 2002). In adult humans, brain,
lung, muscle, and spleen have similar molybdenum contents
as well (0.14 to 0.20 mg/kg). High levels of tungsten (up to
1 percent) reduced liver molybdenum contents in chicks fed
diets containing 0.5, but not 4 to 5 mg of Mo/kg of feed (Nell
et al., 1980). In wethers, liver or kidney molybdenum con-
tents were more than doubled by increasing the dietary mo-
lybdenum level from 0.4 to 8.4 mg/kg of dry matter (Ivan
and Veira, 1985). Similarly, molybdenum concentrations of
seven different bones were elevated approximately 30-fold
by increasing the molybdenum level of corn silage diets from
0.4 to 1 1 mg/kg of dry matter (Hidiroglou et al., 1982). While
the molybdenum-supplemented wethers also had elevated
Zn concentrations in their bones, the contents of Cu, Mg, P,
Ca, and total ash were unaffected by dietary molybdenum.
After fish were exposed to molybdenum in water ranging
from to 250 mg/L for 3 days, both gill and liver accumu-
lated molybdenum in a dose-dependent fashion (Reid, 2002).
The relationship between the tissue and exposure levels of
molybdenum was linear on a double-reciprocal plot. Al-
though both organs accumulated similar amounts of molyb-
denum on a weight basis, the estimated maximal binding
capacity and the apparent dissociation constant for liver were
4 and 25 times higher than gill, respectively (Reid, 2002).
Both liver and bone molybdenum contents in cattle can be
increased up to 10 to 20 times by feeding high molybdenum
diets over control diets (Ward, 1978).
The whole blood molybdenum concentrations in sheep
and cattle fed low molybdenum diets range from 10 to 60
mg/L, and the mean serum molybdenum concentration of
110 healthy humans was 0.44 |ig/L (Forrer et al., 2001).
Plasma molybdenum concentrations in cattle fed high mo-
lybdenum diets may be 60- to 260-fold higher than those fed
"normal" control diets (Ward, 1978). Cow milk molybde-
num concentrations range from 18 to 120 pg/L, and may
exceed 1 mg/L from cattle grazing on high molybdenum
pasture or ingesting diets supplemented with molybdenum
at 53-173 mg/kg of dry feed (Archibald, 195 1; Huber et al.,
1971; NRC, 1980). Eggs from hens fed commercial rations
had average molybdenum values (wet weight basis) of 0.5,
0.4, and 0.8 mg/kg for whole eggs, white, and yolk, respec-
tively (Arthur et al., 1958).
MAXIMUM TOLERABLE LEVELS
The maximum tolerable level of a mineral is the dietary
level that, when fed for a defined period of time, will not
impair animal health and performance. With the lowest tol-
erance to molybdenum toxicity among all species studied,
cattle definitely show overt toxicosis when the dietary mo-
lybdenum level is at 100 mg/kg of dry matter or higher, re-
gardless of dietary copper or sulfur levels. Toxicosis may
also be produced in cattle by 25 to 50 mg Mo/kg of dry
matter (Ward, 1994). However, the toxicosis caused by
<25 mg Mo/kg is often associated with inadequate available
copper. In addition, 5 mg Mo/kg may be detrimental to
copper-deficient cattle (Gengelbach et al., 1997) and has
been demonstrated to cause copper depletion in heifers
(Bremner et al., 1987). Based on the responses of growth,
liver copper concentration, and plasma copper distribution,
Kincaid (1980) suggested the minimal toxic concentration
of molybdenum in drinking water for calves was between 10
and 50 mg/L, and the critical copper:molybdenum ratio is
<0.5 when the animals were given diets containing 13 mg
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268
MINERAL TOLERANCE OF ANIMALS
Cu/kg and 0.29 percent sulfur. Thus, the maximum tolerable
level of molybdenum, based on the above-mentioned defini-
tion, is suggested as 5 to 10 mg/kg of dry matter for copper-
adequate cattle. However, unless dietary copper is increased
above requirement, this concentration of molybdenum may
lead to copper deficiency over time. It might also be safe to
suggest the same level for sheep and horses. Comparatively,
swine and poultry are more resistant to molybdenosis than
ruminants. As chicks perfomied normally at 100 mg of Mo/kg
of feed (Davies et al., 1960) and 200 mg of Mo/kg of
feed was the lowest level that caused growth depression
(Kratzer, 1952), the maximum tolerable level of molybde-
num for poultry is suggested as 100 mg of Mo/kg of feed.
Two independent studies indicated that growing swine
showed no apparent adverse response to 27 (Gipp et al.,
1967) or 50 mg (Kline et al., 1973) of Mo/kg of feed. Al-
though another old study showed that pigs tolerated 1 g of
Mo/kg of diet (Davis, 1950), the level is unrealistically high.
Based on the chick data and physiological similarities be-
tween these two species, the maximum tolerable level of
molybdenum for swine is suggested as 150 mg of Mo/kg of
feed. For all species of fish studied, a level of 10 mg of Mo/L
seems to be tolerable.
Vyskocil and Viau (1999) reviewed 14 selected earlier
studies in laboratory species based on the "quality" of the
experimental design. They summarized the NOAEL and the
LOAEL as follows (mg of Mo/kg BW/day): rats: 0.9 to 40
(NOAEL), 1.6 to 80 (LOAEL); rabbits: 0.5 to 23 (NOAEL),
5 to 46 (LOAEL); guinea pigs: 75 (LOAEL); and mice: 1.5
(LOAEL). Assuming a 200-g rat eats 15 g diet/day and a
NOAEL of 0.5 mg Mo/kg BW, the tolerable dietary molyb-
denum level is 7 mg/kg diet. An intake of 0.15 mg/kg BW
may be toxic to humans (Holzinger et al., 1998). The toler-
able upper intake level of molybdenum ranges from 0.3 to
0.6 mg/day for children to 2 mg/day for adults, approxi-
mately 40-fold higher than the recommended dietary allow-
ance (IMOA, 2002).
FUTURE RESEARCH NEEDS
Past studies of molybdenum toxicity were mainly con-
ducted under conditions of low or deficient levels of copper.
Future research is needed to distinguish primary molybde-
num toxicosis at adequate or relatively high levels of dietary
copper from the molybdenum-induced copper deficiency.
The biochemical mechanism of the interactions of molybde-
num with sulfur and copper, and the subsequent metabolic
impact are still unclear. Data on bioavailability of dietary
molybdenum of various sources will be useful for both nutri-
tional and toxicological research on molybdenum.
SUMMARY
Molybdenum is a component of three enzymes involved
in catalyzing the metabolism of aldehydes, sulfite, sulfur-
containing amino acids, purines, pyrimidines, and
peteridines in animals. As an essential element, its nutrient
requirements for various species are easily met by feeding
practical diets. Thus, molybdenum deficiency is normally
produced under experimental conditions with semi-purified
diets or high levels of tungstate. However, molybdenum toxi-
cosis can be a practical problem in cattle or sheep grazing
pasture on alkaline soil or contaminated with industrial
sources of molybdenum. The clinical signs of molybdenosis
are essentially secondary copper deficiency manifested by
diarrhea, anorexia, depigmentation of hair or wool, anemia,
neurologic disturbances, impaired reproduction, and prema-
ture death. Other metabolic disorders caused by molybde-
num toxicosis include hypothyroidism, bone and joint defor-
mities, impaired immunity, and liver and kidney injuries.
The biochemical alterations include decreases in plasma
ceruloplasmin, increases in molybdenum-containing enzyme
activities, and alterations of tissue copper and molybdenum
concentrations. Nonruminants and fish are relatively resis-
tant to molybdenum toxicity. The actual tolerable levels of
molybdenum depend on species, dietary levels of copper and
sulfate or protein, and chemical forms of molybdenum. Mo-
lybdenum is not classified as a carcinogen. The teratogenic
effect of molybdenum has yet to be observed in mammals,
but molybdenum is embryotoxic.
REFERENCES
Abumrad, N. N., A. J. Schneider, D. Steel, and L. S. Rogers. 1981. Amino
acid intolerance during prolonged total parenteral nutrition reversed by
molybdate therapy. Am. J. Clin. Nutr. 34:2551-2559.
Ahmed, M. J., and M. E. Haque. 2002. A rapid spectrophotometric method
for the determination of molybdenum in industrial, environmental, bio-
logical and solid samples using 5,7-Dibromo-8-hydroxyquinoline. Anal.
Sci. 18:433^39.
Allen, J. D., and J. W. Gawthorne. 1987. Involvement of the solid phase of
rumen digesta in the interaction between copper, molybdenum and sul-
phur in sheep. Br. J. Nutr. 58:265-276.
Anke, M., M. Green, M. Partschefeld, and B. Groppel. 1978. Molybdenum
deficiency in ruminants. Pp. 230—233 in Proceedings of the Third Inter-
national Symposium on Trace Element Metabolism in Man and Ani-
mals, M. Kirchgessner, ed. Weihenstephan, Germany: Arbeitskreis fur
Tierernahrungsforschung.
Anke, M., B. Groppel, and M. Grun. 1985. Essentiality, toxicity, require-
ment and supply of molybdenum in human and animals. Pp. 154—157 in
Trace Elements in Man and Animals-TEMA 5, C. F. Mills, I. Bremner,
and J. K. Chesters, eds. Slough, UK: Commonwealth Agricultural
Bureaux.
Archibald, J. G. 1951. Molybdenum in cow's milk. J. Dairy Sci. 34:1026.
Arrington, L. R., and G. K. Davis. 1953. Molybdenum toxicity in the rabbit.
J. Nutr. 51:295-304.
Arthington, J. D., L. R. Corah, and F. Blecha. 1996a. The effect of molyb-
denum-induced copper deficiency on acute-phase protein concentra-
tions, superoxide dismutase activity, leukocyte numbers, and lympho-
cyte proliferation in beef heifers inoculated with bovine herpesvirus- 1.
J. Anim. Sci. 74:211-217.
Arthington, J. D., A. R. Spell, L. R. Corah, and F. Blecha. 1996b. Effect of
molybdenum-induced copper deficiency on in vivo and in vitro mea-
sures of neutrophil chemotaxis both before and following an inflamma-
tory stressor. J. Anim. Sci. 74:2759-2764.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
MOLYBDENUM
269
Arthur, D. I., I. Motzok, and H. D. Branion. 1958. Interaction of dietary
copper and molybdenum in rations fed to poultry. Poult. Sci. 37:1 181.
Aupperle, H., H. A. Schoon, and A. Frank. 2001. Experimental copper de-
ficiency, chi'omium deficiency and additional molybdenum supplemen-
tation in goats -pathological findings. Acta Vet. Scand. 42:311-321.
Bandyopadhyay, S. K., K. Chatterjee, R. K. Tiwari, A. Mitra, A. Banerjee,
K. K. Ghosh, and G. C. Chatterjee. 1981. Biochemical studies on mo-
lybdenum toxicity in rats: effects of high protein feeding. Int. J. Vit.
Nutr. Res. 51:401-409.
Bell, M. D., G. B. Diggs, R. S. Lowrey, and P. L. Wright. 1964. Compari-
son of Mo'' metabolism in swine and cattle as affected by stable molyb-
date. J. Nutr. 84:367-372.
Bremner, L, W. R. Humphries, M. Phillippo, M. J. Walker, and P. C.
Morrice. 1987. Iron-induced copper deficiency in calves: dose-response
relationships and interactions with molybdenum and sulfur. Anim. Prod.
45:403^14.
Cook, G. A., A. L. Lesperance, V. R. Bohman, and E. H. Jensen. 1966.
Interrelationship of molybdenum and certain factors to the development
of the molybdenum toxicity in syndrome. J. Anim. Sci. 25:96-101.
Davies, R. E., B. L. Reid, A. A. Kurnick, and J. R. Couch. 1960. The effect
of sulfate on molybdenum toxicity in the chick. J. Nutr. 70:193-198.
Davis, G. K. 1950. The influence of copper on the metabolism of phospho-
rus and molybdenum. Pp. 216—229 in Symposium on Copper Metabo-
lism, W. D. McElroy and B. Glass, eds. Baltimore: Johns Hopkins Press.
Dick, A. T. 1956. Molybdenum in animal nutrition. Soil Sci. 81:229-258.
Friberg, L., and L. Lener. 1986. Molybdenum. Pp. 446^61 in Handbook
on the Toxicology of Metals, 2nd ed., L. Friberg, G. F. Nordberg, and
V. B. Vouk, eds. New York: Elsevier/NorthHolland Biomedical Press.
Forrer, R., K. Gautschi, and H. Lutz. 2001. Simultaneous measurement of
the trace elements Al, As, B, Be, Cd, Co, Cu, Fe, Li, Mn, Mo, Ni, Rb,
Se, Sr, and Zn in human serum and their reference ranges by ICP-MS.
Biol. Trace Elem. Res. 80:77-93.
Fungwe, T. V., F. Buddingh, D. S. Demick, C. D. Lox, M. T. Yang, and S.
P. Yang. 1990. The role of dietary molybdenum on estrous activity,
fertility, reproduction and molybdenum and copper enzyme activities of
female rats. Nutr. Res. 10:515-524.
Gardner, A. W., and P. K. Hall-Patch. 1962. An outbreak of industrial
molybdenosis. Vet. Rec. 74:113.
Gengelbach, G. P. 1994. Effects of dietary copper deficiency on cellular
immunity in cattle. Ph.D. dissertation. North Carolina State University,
Raleigh.
Gengelbach, G. P., and J. W. Spears. 1998. Effects of dietary copper and
molybdenum on copper status, cytokine production, and humoral im-
mune response of calves. J. Dairy Sci. 81:3286—3292.
Gengelbach, G. P., J. D. Ward, J. W. Spears, and T. T. Brown, Jr. 1997.
Effects of copper deficiency and copper deficiency coupled with high
dietai'y iron or molybdenum on phagocytic cell function and response of
calves to a respiratory disease challenge. J. Anim. Sci. 75:1112—1118.
Gipp, W. F., W. G. Pond, and S. E. Smith. 1967. Effects of level of dietary
copper, molybdenum, sulfate, and zinc on body weight gain, hemoglo-
bin, and liver storage of growing pigs. J. Anim. Sci. 26:727-730.
Gooneratne, S. R., W. T. Buckley, and D. A. Christensen. 1989. Review of
copper deficiency and metabolism in ruminants. Can. J. Anim. Sci.
69:819-845.
Grace, N. D. and N. F. Suttle. 1979. Some effects of sulphur intake on
molybdenum metabolism in sheep. Br. J. Nutr. 41:125-136.
Hamilton, S. J., and K. J. Buhl. 1990. Acute toxicity of boron, molybde-
num, and selenium to fry of chinook salmon and coho salmon. Aich.
Environ. Contam. Toxicol. 19:366-373.
Haywood, S., Z. Dincer, J. Holding, and N. M. Parry. 1998. Metal (molyb-
denum, copper) accumulation and retention in brain, pituitary and other
organs of ammonium tetrathiomolybdate-treated sheep. Br. J. Nutr.
79:329-331.
Hidiroglou, M., G. Morris, and M. Ivan. 1982. Chemical composition of
sheep bones as influenced by molybdenum supplementation. J. Dairy
Sci. 65:619-624.
Holzinger, S., M. Anke, B. Rohrig, and D. Gonzalez. 1998. Molybdenum
intake of adults in Germany and Mexico. Analyst 123(3):447^50.
Huber, J. T., N. O. Price, andR. W. Engel. 1971. Response of lactating cows
to high levels of dietaiy molybdenum. J. Anim. Sci. 32(2):364— 367.
Humphries, W. R., C. F. Mills, A. Greig, L. Roberts, D. Inglis, and G. J.
Halliday. 1986. Use of ammonium tetrathiomolybdate in the treatment
of copper poisoning in sheep. Vet. Rec. 1 19(24):596-598.
Igarza, L., M. A. Quiroga, M. C. Agostini, and N. Auza. 1999. Modelo
experimental para el estudio de la molibdenosis y de la deficiencia
primaria de cobre en ratas. Acta Physiol. Pharmacol. Ther. Latinoam.
49:170-176.
IMOA (International Molybdenum Association). 2002. Available at
http://www.imoa.info.
Ivan, M., and D. M. Veira. 1985. Effects of copper sulfate supplement on
growth, tissue concentration, and niminal solubilities of molybdenum
and copper in sheep fed low and high molybdenum diets. J. Dairy Sci.
68:891-896.
Jenkins, K. J. 1989. Effect of copper loading of preruminant calves on intra-
cellular distribution of hepatic copper, zinc, iron, and molybdenum. J.
Dairy Sci. 72:2346-2350.
Johnson, J. L. 1988. Molybdenum. Methods Enzymol. 158:371-382.
Johnson, J. L. 1997. Molybdenum. Pp. 413^38 in Handbook of Nutrition-
ally Essential Mineral Elements, B. L. O'Dell and R. A. Sunde, eds.
New York: Marcel Dekker.
Johnson, J. L., B. E. Hainline, and K. V. Rajagopalan. 1980. Characteriza-
tion of the molybdenum cofactor of sulfite oxidase, xanthine oxidase
and nitrate reductase. Identification of a pteridine as a structural compo-
nent. J. Biol. Chem. 255:1783-1786.
Kincaid, R. L. 1980. Toxicity of ammonium molybdate added to drinking
water of calves. J. Dairy Sci. 63:608-610.
Kisker, C, H. Schindelin, A. Pacheco, W. A. Wehbi, R. M. Garrett, K. V.
Rajagopalan, J. H. Enemark, and D. C. Rees. 1997. Molecular basis of
sulfite oxidase deficiency from the structure of sulfite oxidase. Cell
91:973-983.
Kline, R. D., M. A. Corzo, V. W. Hays, and G. L. Cromwell. 1973. Related
effects of copper, molybdenum and sulfide on performance, hematol-
ogy, and copper stores of growing pigs. J. Anim. Sci. 37:936-941.
Knothe, D. W., and G. G. Van Riper. 1988. Acute toxicity of sodium mo-
lybdate dehydrate (molyhibit 100) to selected saltwater organisms. Bull.
Environ. Contam. Toxicol. 40:785-790.
Kratzer, F. H. 1952. Effect of dietary molybdenum upon chicks and poults.
Proc. Soc. Exp. Biol. Med. 80:483^86.
Lepore, P. D., and R. F. Miller. 1965. Embryonic viability as influenced by
excess molybdenum in chicken breeder diets. Proc. Soc. Exp. Biol. Med.
118:155-157.
Lesperance, A. L., V. R. Bohman, and J. E. Oldfield. 1985. Interaction of
molybdenum, sulfate and alfalfa in the bovine. J. Anim. Sci. 60:791-802.
Lloyd, W. E., H. T. Hill, and G. L. Meerdink. 1976. Observations of a case
of molybdenosis-copper deficiency in a South Dakota dairy herd. Pp.
85—95 in Molybdenum in the Environment, W. Chappell and K. K.
Peterson, eds. New York: Marcel Dekker.
MacLachlan, G. K., and W. S. Johnston. 1982. Copper poisoning in sheep
from North Ronaldsay maintained on a diet of terrestrial herbage. Vet.
Rec. 111(13):299-301.
Mason, J. and C. J. Cardin. 1977. The competition of molybdate and sul-
phate ions for a transport system in the ovine small intestine. Res. Vet.
Sci. 22(3):313-315.
McDowell, L. R. 2003. Minerals in Animal and Human Nutrition, 2nd ed.
Amsterdam: Elsevier.
Meyer, R. D., R. L. Phillips, and D. B. Marcum. 1999. Molybdenum, cop-
per, and selenium in alfalfa and other forages. Proceedings of the 29th
California Alfalfa Symposium, December 8—9, 1999, Radisson Hotel,
Fresno, CA. Available at http://esce.ucr.edu/wasteman/2000/
Meyer_california_alfalfa_symposium.htm. Accessed on April 2, 2005.
Miller, J. K., B. R. Moss, M. C. Bell, and N. Sneed. 1972. Comparison of
''Mo metabolism in young cattle and swine. J. Anim. Sci. 34:846—850.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
270
MINERAL TOLERANCE OF ANIMALS
Nagy, J. G., W. Ciiappel. and G. M. Ward. 1975. Effects of liigh molybde-
num intake in mule deer. J. Anim. Sci. 41:412.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
Nell, J. A., E. F. Annison, and D. Balnave. 1980. The influence of tungsten
on the molybdenum status of poultry. Br. Poult. Sci. 21:193-202.
Nielsen, F. H. 1996. Other trace elements. Chapter 35. Pp. 353-377 in
Present Knowledge in Nutrition, 7th ed., E. E. Ziegler and L. J. Filer,
eds. Washington, D.C.: International Life Sciences Institute Press.
Olson, K. J., J. P. Fontenot, and M. L. Failla. 1984. Influence of molybde-
num and sulfate supplementation and withdrawal of diets containing
high-copper boiler litter on tissue copper levels in ewes. J. Anim. Sci.
59:210-216.
Opresko, D. M. 1993. Toxicity summary for molybdenum. Available at
http://risk.lsd.ornl.gov/tox/profiles/molybdenum.
Pandey, R., and S. P. Singh. 2002. Effects of molybdenum on fertility of
male rats. BioMetals 15:65-72.
Pott, E. B., P. R. Henry, M. A. Zanetti, P. V. Rao, E. J. Hinderberger, Jr.,
and C. B. Ammerman. 1999. Effects of high dietary molybdenum con-
centration and duration of feeding time on molybdenum and copper
metabolism in sheep. Anim. Feed Sci. Technol. 79:93.
Price, J., A. M. Will, G. Paschaleris, and J. K. Chesters. 1987. Identification
of thiomolybdates in digesta and plasma from sheep after administration
of '''Mo-labelled compounds into the rumen. Br. J. Nutr. 58: 127-138.
Reid, S. D. 2002. Physiological impact of acute molybdenum exposure in
juvenile kokanee salmon (Oncorhynchus nerka). Comp. Biochem.
Physiol. Part C 133:355-367.
Spears, J. W. 2003. Trace mineral bioavailability in ruminants. J. Nutr.
133:1506S-1509S.
Standish, J. F., C. B. Ammerman, N. D. Wallace, and G. E. Combs. 1975.
Effect of high dietary molybdenum and sulfate on plasma copper clear-
ance and tissue minerals in growing swine. J. Anim. Sci. 40:509—513.
Suttle, N. F. 1975. The role of organic sulfur in the copper-molybdenum-S
interrelationship in ruminant nutrition. Br. J. Nutr. 34:41 1^20.
Suttle, N. F. 1991. The interactions between copper, molybdenum, and sul-
phur in ruminant nutrition. Annu. Rev. Nutr. 11:121-140.
Suttle, N. F., and J. Small. 1993. Evidence for delayed availability of cop-
per in supplementation trials with lambs in molybdenum-rich pastures.
Pp. 651—655 in Proceedings of the Eighth Symposium on Trace Ele-
ments in Man and Animals, M. Anke, D. Meissner, and C. F. Mills, eds.
Gersdorf, Germany: Verlag Media Touristik.
Suttle, N. F., D. P. Knox, K. W. Angus, F. Jackson, and R. L. Coop. 1992.
Effects of dietary molybdenum on nematode and host during Haemon-
chus contortus infection in lambs. Res. Vet. Sci. 52:230—235.
Tiffany, M. E., L. R. McDowell, G. A. O'Connor, F. G. Martin, N. S.
Wilkinson, E. C. Cardoso, S. S. Percival, and P. A. Rabiansky. 2000.
Effects of pasture applied biosolids on performance and mineral status
of grazing beef heifers. J. Anim. Sci. 78:1331-1337.
Tiffany, M. E., L. R. McDowell, G. A. O'Connor, F. G. Martin, N. S.
Wilkinson, S. S. Percival, and P. A. Rabiansky. 2002. Effects of re-
sidual and reapplied biosolids on performance and mineral status of
grazing beef steers. J. Anim. Sci. 80:260—269.
Topham, R. W., M. C. Walker, and M. P. Calisch. 1982a. Liver xanthine
dehydrogenase and iron mobilization. Biochem. Biophys. Res.
Commun. 109:1240-1246.
Topham, R. W., M. C. Walker, M. P. Calisch, and R. W. Williams. 1982b.
Evidence for the participation of intestinal xanthine oxidase in the mu-
cosal processing of iron. Biochemistry 21:4529—4535.
Turnlund, J. R., W. R. Keyes, G. L. Peiffer, and G. Chiang. 1995. Molybdenum
absoiption, excretion, and retention studied with stable isotopes in young
men during depletion and repletion. Am. J. Clin. Nutr. 61:1102-1109.
Underwood, E. J., and N. F. Suttle. 1999. The Mineral Nutrition of Live-
stock, 3rd ed. New York: CABl Publishing.
Venugopal, B., and T. D. Luckey. 1978. Molybdenum. Pp. 253-257 in
Metal Toxicity in Mammals, 2. Chemical Toxicity of Metals and Metal-
loids. New York: Plenum Press.
Versieck, J., J. Hoste, L. Vanballengerghe, F. Barbier, R. Cornells, and 1.
Waelput. 1981. Serum molybdenum in diseases of the liver and biliary
system. J. Lab Clin. Med. 97:535-544.
Vyskocil, A., and C. Viau. 1999. Assessment of molybdenum toxicity in
humans. J. Appl. Toxicol. 19:185-192.
Walsh, T., and L. B. O'Moore. 1953. Excess of molybdenum in herbage as a
possible contributory factor in equine osteodystrophia. Nature 171:1166.
Ward, G. M. 1978. Molybdenum toxicity and hypocuprosis in ruminants: a
review. J. Anim. Sci. 46:1078-1085.
Ward, G. M. 1994. Molybdenum requirements, toxicity, and nutritional lim-
its for man and animals. Stud. Inorg. Chem. 19:452^76.
Ward, J. D., and J. W. Spears. 1997. Long-term effects of consumption of
low-copper diets with or without supplemental molybdenum on copper
status, performance, and carcass characteristics of cattle. J. Anim. Sci.
75:3057-3065.
Ward, J. D., and J. W. Spears. 1999. The effects of low-copper diets with or
without supplemental molybdenum on specific immune responses of
stressed cattle. J. Anim. Sci. 77:230-237.
White, C. L., T. K. Cadwalader, W. G. Hoekstra, and A. L. Pope. 1989. The
metabolism of ^""Se-selenomethionine in sheep given supplementary
copper and molybdenum. J. Anim. Sci. 67:2400-2408.
Widjajakusuma, M. C, P. K. Basrur, and G. A. Robinson. 1973. Thyroid
function in molybdenotic rabbits. J. Endocrinol. 57(3) :4 19^24.
Williams, R. J. P., and J. J. R. Frausto da Silva. 2002. Breakthroughs and
views: the involvement of molybdenum in life. Biochem. Biophys. Res.
Comm. 292:293-299.
Copyright © National Academy of Sciences. All rights reserved.
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22
Nickel
INTRODUCTION
Nickel (Ni) is a transition element that exhibits a mixture
of ferrous and nonferrous metal properties. Metallic nickel is
lustrous silver-white, malleable, and resistant to corrosion
(Smialowicz, 1998). Nickel is both siderophilic (i.e., associ-
ates with iron) and chalcophilic (i.e., associates with sulfur)
and constitutes 0.008 percent of the Earth's crust, which
makes it the 24th element in order of natural abundance. It is
mostly mined as the laterites nickeliferous limonite
((Fe,Ni)0(OH)) and garnierite (a hydrous nickel silicate), or
the magmatic sulfide pentiandite ((Ni,Fe)gSg).
In the Western world, about 65 percent of the nickel is
used for making stainless steel and 12 percent for making
superalloys. The remaining usage is divided among alloy
steels, rechargeable batteries, catalysts and other chemicals,
coinage, foundry products, and plating (USGS, 2003). The
principal commercial chemicals are NiCOj, NiClj, NiO, and
NiS04.
Nickel in compounds is usually divalent, but can exist in
oxidation forms -1, 0, H-1, +2, +3, and +4. The acetate, ni-
trate, sulfate, and halogen salts of nickel are water soluble,
whereas the oxides, sulfides, carbonates, phosphate, and el-
emental forms of nickel are insoluble in water. In biological
systems, Ni-+ predominates and coordinates with water or
other soluble ligands (Sutherland and Costa, 2002). Proteins
containing the amino acid histidine (Sarkar, 1984) are the
apparent key biological ligands for nickel.
ESSENTIALITY
Nickel is essential for some lower forms of life where it
participates in hydrolysis and redox reactions, regulates gene
expression, and stabilizes certain structures (Nielsen, 1998).
In these roles, nickel forms ligands with sulfur, nitrogen, and
oxygen, and exists in oxidation states -1-3, +2, and H-1. Among
the enzymes requiring nickel for activity are hydrogenases
that have been identified in >35 species of bacteria, includ-
ing methanogenic, hydrogen-oxidizing, sulfate-reducing,
phototrophic, and aerobic nitrogen-fixing bacteria. Nickel is
a component of ureases from bacteria, mycoplasma, fungi,
yeast, algae, and invertebrates. A nickel-containing super-
oxide dismutase has been identified in Streptomyces (Kim et
al., 1998).
Nickel is essential for nitrogen metabolism in plants
where it is a component of urease (Welch, 1981). In soy-
beans, urea accumulates to toxic levels as a result of de-
pressed urease activity (Eskew et al., 1983). The mechanism
for nickel deficiency disrupting nitrogen metabolism, and
altering malate and amino acid concentrations in grains, is
not fully understood. These disruptions result in growth de-
pression, premature senescence, decreased tissue iron con-
centrations, inhibited grain development, and decreased
grain viability (Brown et al., 1987, 1990).
Nickel is generally not accepted as an essential nutrient
for higher animals, apparently because of the lack of a
clearly defined specific biochemical function. However,
under experimental conditions, nickel deprivation resulted
in several subnormal functions in higher animals. Nickel
deprivation (<10G |Jg/kg diet) in goats depressed growth
(Anke et al., 1984) and in rats (27 |-ig/kg diet) increased
blood pressure (Nielsen, 2001). Reproductive function was
impaired in both goats and rats. In breeding goats, the rate
of success of first insemination and conception was de-
creased, and number of breeding attempts to achieve preg-
nancy was increased (Anke et al., 1984). In rats, sperm pro-
duction and motility were decreased (Yokoi et al., 2003).
The biochemical changes reported to occur in nickel-de-
prived pigs fed <100 pg Ni/kg dry diet included increased
urinary calcium excretion and decreased skeletal calcium
content (Anke et al., 1984). Rats fed 2-30 \ig Ni/kg diet
exhibited changes in blood and iron indexes that suggested
an impairment in iron metabolism (Schnegg and
Kirchgessner, 1975; Nielsen et al., 1984; Stangl and
Kirchgessner, 1997). In addition, nickel-deficient (13
|jg/kg diet) rats accumulated triacylglycerol in liver with
276
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NICKEL
277
increased concentrations of saturated, monosaturated, and
polyunsaturated fatty acids; decreased liver activities of li-
pogenic enzymes glucose-6-piiosptiate defiydrogenase, 6-
pfiospiiogluconate defiydrogenase, malic enzyme, and fatty
acid synthase (StangI and Kirchgessner, 1996); and altered
brain and erythrocyte fatty acid composition of total lipids
and individual phospholipids (StangI and Kirchgessner,
1997). Nickel might have a function that is associated with
vitamin Bp, because lack of this vitamin inhibits the re-
sponse to nickel supplementation when dietary nickel is
low (Nielsen et al., 1989), and nickel can alleviate vitamin
Bj2 deficiency in higher animals (StangI et al., 2000).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Electrothermal atomic absorption spectrometry (EAAS)
with Zeeman background correction is currently the tech-
nique most often used to determine the concentration of
nickel in biological materials (Sunderman et al., 1988b). The
use of ICP-MS for the analysis of nickel is hampered by
matrix interference by calcium, sodium, and potassium.
Four methods are commonly used for the preparation of
samples for analysis by EAAS. These are acid digestion, pro-
tein precipitation, acidification (Sunderman et al., 1988b),
and microwave digestion (Benson et al., 1989). Acid diges-
tion is the oxidation of the sample with nitric acid and an
oxidizer such as hydrogen peroxide. The protein precipita-
tion method is used for fluids (serum, plasma, whole blood,
saliva, bile, and cerebrospinal fluid) and involves the pre-
cipitation of protein from the fluid by nitric acid and heat.
The direct technique in which the sample is just acidified
with nitric acid prior to analysis, is used to determine nickel
in urine, water, and protein-free aqueous samples. The mi-
crowave digestion procedure uses a microwave oven for ir-
radiating samples in Teflon digesters containing nitric acid,
hydrochloric acid, and hydrogen peroxide.
Contamination is a major concern when determining the
presence of nickel in a sample. Careful handling of samples
is required to prevent contamination from ambient air, skin
(sweat) of the handler, instruments (e.g., stainless steel
knives, scissors, needles, etc.) used to collect samples, and
reagents used in the analysis. Because of contamination con-
cerns, the validity of any nickel analysis can only be assured
by the use of quality control procedures.
REGULATION AND METABOLISM
Absorption and Metabolism
It is generally accepted that <10 percent of the nickel that
humans and animals ingest with food is absorbed (Nieboer
et al., 1988). Nickel absorption is heightened by iron defi-
ciency (Tallkvist and Tjalve, 1997), pregnancy
(Kirchgessner et al., 1980b), and lactation (Kirchgessner et
al., 1983). The mechanisms involved in the transport of
nickel through the gut are not conclusively established, but
both active and passive processes are thought to be involved
(Foulkes and McMuUen, 1986; Tallkvist and Tjalve, 1998).
It has been suggested that some nickel is transported through
an iron-transport system (Tallkvist and Tjalve, 1997), and
cobalt can compete with these elements for transport
(Eidelsburger et al., 1996). Nickel homeostasis may be regu-
lated by absorption from the gut. The rate of nickel transfer
was greater in everted jejunal sacs from nickel-deprived rats
than from nickel-adequate rats (StangI et al., 1998).
Nickel is transported in blood principally bound to serum
albumin. Small amounts of nickel in serum are associated
with the amino acids histidine and aspartic acid, and with a-
2-macroglobulin (nickeloplasmin) (Nomoto and Sunderman,
1988; Tabata and Sarkar, 1992). Uptake of soluble nickel
from serum into tissues is believed to be governed by ligand
exchange reactions (Sutherland and Costa, 2002). It has been
suggested that histidine removes nickel from serum albumin
and mediates its entry into cells. The transfer of nickel across
plasma membranes apparently involves both active and dif-
fusion mechanisms, which have not been defined. Soluble
nickel may share a common transport system with magne-
sium and/or iron (e.g., transported into the cell bound to
transferrin) and some soluble nickel probably enters cells
via calcium channels (Sutherland and Costa, 2002). Insoluble
nickel compounds enter the cell via phagocytosis (Sutherland
and Costa, 2002).
Although fecal nickel excretion (mostly unabsorbed
nickel) is 10-100 times as great as urinary excretion, most of
the small fraction of absorbed nickel is rapidly and efficiently
excreted through the kidney as urinary low-molecular-
weight complexes (Predki et al., 1992). In healthy humans,
urinary nickel concentrations generally range from 0.1 to
13.3 |Jg/L (Sutherland and Costa, 2002). The nickel content
in human sweat is high (~70 |Jg/L), which points to active
secretion of nickel by the sweat glands (Omokhodion and
Howard, 1994). Based on isotopic studies in which nickel
was administered intravenously, excretion of exogenous
nickel through the bile or gut is insignificant (Marzouk and
Sunderman, 1985; Patriarca et al., 1997).
IVIetabolic Interactions and IVIechanisms of Toxicity
Because there apparently are mechanisms for the homeo-
static regulation of nickel, life-threatening toxicity of nickel
through oral intake is low, ranking with elements such as
zinc, chromium, and manganese. Generally, a diet of 100
mg Ni/kg supplemented as a water soluble salt is required to
produce signs of nickel toxicity in rats, mice, chicks, dogs,
cows, rabbits, pigs, ducks, and monkeys. Initial signs of
nickel toxicity apparently are the result of reduced food in-
take (partially caused by reduced palatability) and gas-
trointestinal irritation. Some responses to excessive intake
of nickel may be the result of nickel interfering with the
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278
MINERAL TOLERANCE OF ANIMALS
absorption or use of essential elements, especially copper,
iron, and zinc; these responses become more evident when
the intake of these elements is deficient. For example, exces-
sive amounts of nickel as nickel chloride or nickel sulfate
exacerbate signs of severe iron, copper, and zinc deficien-
cies in rats (Nielsen et al., 1979; Nielsen and Zimmerman,
1981; and Mathur et al., 1982, respectively). Studies using
injected nickel or isolated cells suggest that nickel may have
toxic effects through altering cellular redox status, which
can cause DNA and cellular membrane and protein damage,
impaired cell cycle progression, and abnormal cytoskeletal
structure (Sutherland and Costa, 2002). The oxidation po-
tential of nickel is lowered upon binding to certain cellular
ligands; this increases its reactivity towards cellular oxidants
such as molecular oxygen, hydrogen peroxide, and lipid per-
oxides. Oxidation of Ni-+ to Ni"*"^ may result in the formation
of reactive oxygen species that can cause cytotoxic damage
and decrease cellular antioxidant capacity (Sutherland and
Costa, 2002). Nickel also may be toxic through inhibiting
enzymes involved in glucose, energy, and oxidative metabo-
lism. In mice, 1,600 mg Ni/kg diet as nickel acetate inhibited
the activities of liver and heart cytochrome C oxidase, kid-
ney malic dehydrogenase, liver, kidney and heart isocitric
dehydrogenase, kidney succinic dehydrogenase, and liver
NADH cytochrome C reductase (Weber and Reid, 1969).
Pandey et al. (1999) found that 5 and 10 mg Ni/kg BW ad-
ministered orally as nickel sulfate 5 days a week for 35 days
increased the activities of lactate dehydrogenase and
y-glutamyl transpeptidase and decreased the activity of sor-
bitol dehydrogenase in the testes of mice. In rats, 1,000 mg
Ni/kg diet as nickel chloride or nickel sulfate increased blood
glucose, serum and liver protein, liver urea and liver
glutamate dehydrogenase activity, and inhibited the activi-
ties of liver and heart cytochrome C oxidase, liver succinic
dehydrogenase and glucose-6-phosphate dehydrogenase,
and plasma alkaline phosphatase (Whanger, 1973; Schnegg
and Kirchgessner, 1976; Kirchgessner et al., 1980a; Mathur,
1983).
SOURCES AND BIOAVAILABILITY
Most animal feeds, because they are plant-based, contain
relatively high amounts of nickel (Nielsen, 1987). Common
pasture plants contain 0.5-3.5 mg Ni/kg DM. Nickel content
has been reported in some feed grains and protein sources,
including wheat (0.08-0.3 mg/kg); corn (0.20 mg/kg); oats
(0.71-2.09 mg/kg); linseed meal (5.24 mg/kg); soybean meal
(7.91 mg/kg); and sunflower meal (7.78 mg/kg). Exposure
to emissions from industry such as nickel-processing plants
can increase the nickel content of plants 10-fold (Anke et al.,
1995). Because nickel concentrations are low in animal tis-
sues, milk products and meat meals used as protein supple-
ments contain relatively low amounts of nickel. However,
fish protein concentrate was found to contain 0.7-2.8 mg Ni/
kg (Langmyhr and Orre, 1980). The nickel content of water
is typically low. The concentrations in the major river basins
and water supplies of the United States were determined to
be usually <10 |Jg/L (NRC, 1975).
In humans, when nickel in water is ingested after an over-
night fast, as much as 50 percent, but usually closer to 20-25
percent, of the dose is absorbed (Solomons et al., 1982;
Sunderman et al., 1989). Foods, drinks, and specific
biochemicals (e.g., ascorbic acid) depress this high absorp-
tion, often to < 1 percent. The form of nickel in foods and
feeds and its bioavailability has not been determined.
TOXICOSIS
The toxicity of nickel in laboratory animals exposed to
nickel through dermal application, injection, or inhalation,
and in isolated cells exposed to high doses of nickel, has
been extensively studied. This study has been prompted by
findings showing that nickel is a carcinogen and an allergen
for humans. Exposure to nickel oxides and nickel subsulfide
has been consistently associated with lung and nasopharyn-
geal cancer among nickel refinery workers in Wales, Canada,
Norway, and the United States (Kasprzak, 1987). Nickel is a
powerful sensitizing agent that elicits hypersensitivity reac-
tions manifested by contact dermatitis and asthma
(Smialowicz, 1998). The many toxic manifestations of nickel
by routes of exposure not relevant to the mission of this docu-
ment have been recently reviewed (Sutherland and Costa,
2002), and thus will not be presented here. Also, unlike the
predecessor of this document (NRC, 1980), this review will
not tabulate studies showing relatively high amounts of
orally ingested nickel (generally between 20 and 1,000 mg
Ni/kg diet) having no or beneficial effects. For example, no
adverse effects were observed in rats fed 250, 500, or 1,000
mg Ni/kg diet as nickel carbonate, nickel soap, and nickel
catalyst for 3 to 4 months, or in monkeys fed in a similar
manner for 6 months (Phatak and Patwarhan, 1950). An ex-
ample of a beneficial effect is the finding that supplementing
25 mg Ni/kg diet in chicks improved their bone strength
(Wilson etal., 2001).
Acute
The acute toxicity of nickel is low. It has been suggested
that low oral toxicity may be the result of nickel binding to a
basolateral population of metal carriers in the gastrointesti-
nal tract, which blocks its own basolateral transfer in a con-
centration-dependent manner (Muller-Fassbender et al.,
2003). Nonetheless, acute lethal doses have been adminis-
tered to animals. The first published study of nickel using
experimental animals determined the effects of acute high
doses of nickel. Gmelin (1826) found that the administration
of nickel sulfate to rabbits and dogs by stomach tube pro-
duced severe gastritis and fatal convulsions; sublethal doses
of nickel sulfate in dogs induced cachexia and conjunctivi-
tis. The acute oral LD^q dose of nickel (as nickel acetate)
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NICKEL
279
was determined to be 1 36 mg/kg BW for mice and 116 mg/kg
BW for rats (Fairchild et al., 1977). The 48-hour LCjq values
for carp (Putitius conchonius) in soft and hard water for
nickel sulfate were 158.4 and 397.9 mg/L, respectively; for
nickel chloride, the values were 295.4 and 586.2 mg/L, re-
spectively (Gill and Pant, 1981). The 48-hour LCjq for
Channel punctatus was found to be 30.7 mg/L of water
(Khangarot and Durve, 1982).
Reports of human nickel toxicosis through oral intake
are limited to a few case reports of acute effects caused by
the ingestion of high doses of soluble nickel salts. The most
prominent case report was of 20 people who accidentally
ingested 0.5-2.5 g of nickel as the sulfate and chloride;
they developed nausea, abdominal pain, diarrhea, vomit-
ing, and shortness of breath (Sunderman et al., 1988a). A
0.6 mg oral dose of nickel as nickel sulfate in water drunk
by fasting (thus nickel was highly available) nickel-sensi-
tive individuals produced a contact dermatitis-like reaction
(Cronin et al., 1980).
Chronic
Table 22-1 summarizes the doses and effects (mostly
physical signs) of chronic consumption of high amounts of
nickel by various animals. No chronic toxicosis signs caused
by oral intake have been reported for humans. Extended pe-
riods of time consuming relatively high amounts of nickel
are required before signs of chronic toxicosis are seen in
animals. The most commonly reported signs of toxicosis in-
clude depressed growth, feed intake, and feed efficiency;
hematological changes; kidney damage; and impaired repro-
ductive performance characterized by increased deaths of
offspring.
As indicated by Table 22-1, high oral nickel intakes may
be toxic to the developing embryo. Schroeder and Mitchener
(1971) reported that 5 mg Ni/L of water as nickel chloride as
a soluble salt through three generations increased the num-
ber of runts born and the number of perinatal deaths in rats.
Smith et al. (1993) fed 10, 50, and 250 mg/L water to rats
through two generations and found increased perinatal mor-
tality only with the two higher intakes. Ambrose et al. (1976)
fed 250, 500, or 1,000 mg Ni/kg diet as nickel sulfate through
three generations and observed increased stillborns only in
the Fl generation. However, a decreased number of pups
were weaned in all generations from rats fed 500 or 1,000
mg Ni/kg diet. These reproduction findings need to be re-
peated or confirmed, because all of them were obtained from
experiments that were either flawed or subject to misinter-
pretation by their statistical design and inconsistencies in the
reported quantity-response relationships. Triipschuch et al.
(1996) found that 250 or 500 mg Ni/kg as nickel sulfate in
the diet of hens increased the mortality of hatched chicks;
1,000 mg Ni/kg diet increased the number of dead, mal-
formed, and nonviable chicks in eggs and increased mortal-
ity after hatching.
Factors Influencing Toxicity
Iron, magnesium, zinc, vitamin C, cysteine, protein, and
some pesticides may influence nickel toxicity (400 mg/kg
diet as nickel chloride). Iron-deficient chicks were found to
be more susceptible to nickel toxicity, as judged by growth
depression, than iron-adequate chicks (Blalock and Hill,
1985). A review (McCoy and Kenny, 1992) summarized
findings suggesting that magnesium can antagonize toxic
effects of nickel, especially those induced in vitro or by in-
jected nickel. Mathur et al. (1982) observed that high dietary
zinc enhanced signs of nickel toxicosis such as depressed
growth, feed efficiency, and feed intake. It has been reported
that increasing dietary vitamin C (Chatterjee et al., 1979)
and cysteine (Griffith et al., 1942) alleviated nickel toxicosis
in rats, and increasing dietary protein from 10 percent to 30
percent decreased nickel toxicosis in chicks (Hill, 1979).
Oral administration of dimethyldithiocarbamate pesticides
(ferbam, ziram, or sodium dimethyldithiocarbamate) or
thiram together with nickel as nickel chloride increased the
concentration of nickel in several tissues of rats (Borg and
Tjalve, 1988). The increase in tissue nickel apparently oc-
curred through the formation of lipophilic nickel-pesticide
chelates that facilitate the transfer of nickel through the gas-
trointestinal tract. This suggests that some pesticides can fa-
cilitate nickel toxicity (Hopfer et al., 1987).
TISSUE LEVELS
Nickel is widely distributed in tissues in concentrations
generally between 0.01 and 0.2 mg/kg WW (see Table 22-2)
when dietary nickel is not excessive (<25 mg/kg). Nickel
does not accumulate with age in any organ, but, as with other
mineral elements, overcoming homeostatic mechanisms by
the addition of soluble nickel salts to drinking water or diet
elevates tissue and blood nickel concentrations. Kidney ap-
parently is the organ most sensitive to an increased ingestion
of nickel. A kidney nickel concentration >1 mg/kg WW may
be an indicator of nickel toxicosis. The highest kidney nickel
concentration reported has been about 29 mg/kg WW for
rats fed 1,000 mg/kg diet (Schnegg and Kirchgessner, 1976).
Because monkeys, which probably respond similarly to hu-
mans, exhibited no signs of toxicosis when fed 250, 500, and
1,000 mg Ni/kg diet as nickel catalyst, nickel soap, and
nickel carbonate for 24 weeks (Phatak and Patwardhan,
1950), the data in Table 22-2 indicate that no animal tissue
or fluid used as a food will contain enough nickel to be of
toxicological concern for humans.
MAXIMUM TOLERABLE LEVELS
The highest dietary level at which nickel has no adverse
effect, or the lowest level that induces signs of toxicosis,
varies with species. For example, no adverse effects were
seen in dogs or monkeys fed 1,000 mg Ni/kg diet as water
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280
MINERAL TOLERANCE OF ANIMALS
insoluble nickel compounds (Phatak and Patwardhan, 1950),
but signs of nickel toxicosis were observed in chicks fed
300, pigs fed 375, and rats fed 100 mg Ni/kg diet as water
soluble compounds (see Table 22-1). The rat findings sug-
gest that to assure safety, the maximum tolerable level for
animals without toxicity data should be no more than 100
mg/kg diet. In the previous edition of this document (NRC,
1980), 50 mg Ni/kg diet was suggested as a maximum toler-
able level for cattle. This suggestion seems conservative be-
cause steers fed 50 mg Ni/kg diet (Oscar and Spears, 1988),
chicks and pigs fed 250 mg Ni/kg diet, and dogs fed 1,000
mg Ni/kg diet (Ambrose et al., 1976) for extended periods of
time were not adversely affected (see Table 22-1). Thus, a
maximum tolerable level for cattle may be near 100 mg Ni/
kg diet, for chicks and pigs may be near 250 mg Ni/kg diet,
and for dogs may be near 1,000 mg Ni/kg diet. Because most
animal feed contains <10 mg/kg, nickel toxicity under nor-
mal environmental conditions is not a concern for domestic
animals. However, emissions from industry such as nickel
refineries can increase plant nickel concentrations 10-fold
(Anke et al., 1995). In these localized environments, nickel
toxicity may be a concern for animals.
As stated above, nickel is considered a carcinogen when
inhaled or injected, and an allergen when inhaled or upon
dermal contact by sensitive individuals. Except for the pos-
sibility that individuals with a nickel allergy may be sensi-
tive to diets high in dietary nickel, there is no evidence for
humans of adverse effects associated with exposure to nickel
through consumption of a normal diet. The Institute of Medi-
cine (2001) used two rat studies to obtain the NOAEL of 5
mg/kg BW/day to use for the calculation of the tolerable
upper intake level (UL) for humans. Using this value and an
uncertainty factor of 300 resulted in a UL of 0.017 mg/kg
BW/day for adults; this translates to about 1.0 mg/day of
soluble nickel salts.
FUTURE RESEARCH NEEDS
There are no apparent pressing research needs in regard
to nickel toxicity through the oral route. However, establish-
ing a biochemical function for nickel, the form and
bioavailability of nickel found naturally in feed, and a clearer
understanding of the mechanisms involved in the absorption
of nickel from the gastrointestinal tract, would be helpful in
clarifying the limits at which nickel is beneficial and detri-
mental to animals.
SUMMARY
Nickel is essential for lower forms of life where it partici-
pates in hydrolysis and redox reactions, regulates gene ex-
pression, and stabilizes certain structures. Nickel generally
is not accepted as essential for higher animals and humans
because it lacks a defined biochemical function. Electrother-
mal atomic absorption spectrometry with Zeeman back-
ground correction is the method of choice for the analysis of
nickel in biological samples that have been acid-digested.
Because of its ubiquity, contamination is a major problem in
nickel analyses. It is generally accepted that <10 percent of
nickel ingested is absorbed by mechanisms not completely
understood. The small amount of nickel absorbed is excreted
mainly in the urine. Because there apparently are mecha-
nisms for the homeostatic regulation of nickel, life-threaten-
ing toxicosis through oral intake is low. Extended periods of
time consuming relatively high amounts of soluble nickel
(i.e., >100 mg/kg diet) are required to induce signs of chronic
nickel toxicosis in animals. The toxic dietary concentration
is 10-100 times greater than the concentration normally
found in animal feeds. The most commonly reported signs
of toxicosis observed under experimental conditions are de-
pressed growth, feed intake and feed efficiency, hematologi-
cal changes, and perhaps kidney damage. Suggested mecha-
nisms involved in nickel toxicity include reduced palatability
of the diet, interference with the absorption or use of other
essential nutrients (e.g., copper, iron, and zinc), and alter-
ation of cellular redox status. A suggested maximum toler-
able limit for cattle is 100 mg/kg diet, and for chicks and
pigs is 250 mg Ni/kg diet. Except for a few localized areas of
the world where industry has increased nickel in the envi-
ronment, nickel toxicity is not a concern for domestic ani-
mals.
REFERENCES
Ambrose, A. M., P. S. Larson, J. F. Borzelleca, and G. R. Hennigar, Jr.
1976. Long-term toxicologic assessment of nickel in rats and dogs. J.
Food Sci. Technol. 13:181-187.
Anke, M., M. Griin, and H. Ki'onemann. 1980a. The capacity of different
organs to indicate the nickel level. Pp. 237—244 in 3. Spurenelement-
Syposium, M. Nickel, H. Anke, J. Schneider, and C. Bruckner, eds.
Jena: Friedrich-Schiller-Universitat.
Anke, M., M. Griin, and H. BCronemann. 1980b. Distribution of nickel in
nickel-deficient goats and their offspring. Pp. 69—72 in Nickel-Toxicol-
ogy, S. S. Brown and F. W. Sunderman Jr., eds. London: Academic Press.
Anke, M., B. Groppel, and A. Hennig. 1984. Nickel, an essential trace ele-
ment. Pp. 404—418 in Mengen-und Spurenelemente, Vol. 2, M. Anke,
C. Bruckner, H. Gurtler, and M. Griin, eds. Leipzig: Karl-Marx-
Universitat.
Anke, M., L. Angelow, M. Glei, M. Muller, and H. Ilhng. 1995. The bio-
logical importance of nickel in the food chain. Fresenius J. Anal. Chem.
352:92-96.
Benson, J. M., A. F. Eidson, R. L. Hanson, R. F. Henderson, and C. H.
Hobbs. 1989. A rapid digestion method for analysis of nickel com-
pounds in tissue by electrothermal atomic absorption spectrometry. J.
Appl. Toxicol. 9:219-222.
Blalock, T. L., and C. H. Hill. 1985. Studies on the effects of iron deficiency
on the toxicities of cadmium, cobalt, nickel, and vanadium. Pp. S— 648—
S— 654 in Health Effects and Interactions of Essential and Toxic Ele-
ments (Nutrition Research Supl. I), M. Abdulla, B. M. Nau", and R. K.
Chandra, eds. New York: Pergamon Press.
Borg, K., and H. Tjalve. 1988. Effect of thiram and dithiocarbamate pesti-
cides on the gastrointestinal absorption and distribution of nickel in
mice. Toxicol. Lett. 42:87-98.
Brown, P. H., R. M. Welch, and E. E. Gary. 1987. Nickel: a micronutrient
essential for higher plants. Plant Physiol. 85:801-803.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
NICKEL
281
Brown, P. H., R. M. Welch, and J. T. Madison. 1990. Effect of nickel defi-
ciency on soluble anion, amino acid, and nitrogen levels in barley. Plant
Soil 125:19-27.
Cain, B. W., and E. A. Pafford. 1981. Effects of dietary nickel on survival
and growth of mallard ducklings. Arch. Environ. Contam. Toxicol.
10:737-745.
Casey, C. E. 1976. Concentrations of some trace elements in human and
cows' milk. Proc. Univ. Otago Med. Sch. 54:7-8.
Chatterjee, K., D. Chakarborty, K. Majumdar, A. Bhattacharyya, and G. C.
Chatterjee. 1979. Biochemical studies on nickel toxicity in weanling
rats — influence of vitamin C supplementation. Internat. J. Vit. Nutr.
Res. 49:264-275.
Chaudhry, H. S., and K. Nath. 1985. Nickel-induced hyperglycemia in the
freshwater fish, Colisafasciatus. Water Air Soil PoUut. 24:173—176.
Clary, J. J. 1975. Nickel chloride-induced metabolic changes in the rat and
guinea pig. Toxicol. Appl. Pharmacol. 31:55-65.
Cronin, E., A. D. Di Michiel, and S. S. Brown. 1980. Oral challenge in nickel-
sensitive women with hand eczema. Pp. 149-152 in Nickel Toxicology,
S. S. Brown and F. W. Sunderman Jr., eds. New York: Academic Press.
Dieter, M. P., C. W. Jameson, A. N. Tucker, M. I. Luster, J. E. French, H. L.
Hong, and G. A. Boorman. 1988. Evaluation of tissue disposition, myelopoi-
etic, and immunologic responses in mice after long-term exposure to nickel
sulfate in the drinking water. J. Toxicol. Environ. Health 24:357—372.
Eastin, W. C, Jr., and T. J. O'Shea. 1981. Effects of dietary nickel on
mallards. J. Toxicol. Environ. Health 7:883-892.
Eidelsburger, U., G. I. Stangl, and M. Kirchgessner. 1996. The effect of
nickel, iron, and cobalt on nickel absorption in nickel-deficient and
nickel-control rats using everted intestinal segments. Trace Elem.
Electrol. 13:182-185.
Eskew, D. L., R. M. Welch, and E. E. Cary. 1983. Nickel: an essential micro-
nutrient for legumes and possibly all higher plants. Science 222:62 1-623.
Fairchild, E. J., R. J. Lewis, and R. L. Tatken, eds. 1977. Pp. 590-592 in
Registry of Toxic Effects of Chemical Substances, Vol. II. DHEW Publ.
No. (NIOSH) 78-104-B.
Foulkes, E. C, and D. M. McMullen. 1986. On the mechanism of nickel
absorption in the rat jejunum. Toxicology 38:35^2.
Gill, T. S., and J. C. Pant. 1981. Toxicity of nickel to the fish Puntius
conchonius (Ham.) and its effects on blood glucose and liver glycogen.
Comp. Physiol. Ecol. 6:99-102.
Gmelin, C. G. 1826. Experiences sur Taction de la baryte, de la strontiane,
du chi'ome, du molybdene, du tungstene, du tellure, de Tosmium, du
platine, de Tiridium, du rhodium, du palladium, du nickel, du cobalt, de
I'urane, du cerium, du fer et du manganese sur I'organisme animal.
Bull. Sci. Med. 7:110-117.
Griffith, W. E., P. L. Pavcek, and D. J. Mulford. 1942. The relation of the
sulphur amino acids to the toxicity of cobalt and nickel in the rat. J.
Nutr. 23:603-612.
Grijn, M., M. Anke, A. Regius, and S. Szentmihalyi. 1980. The nickel status
of cow, sheep, and horse in the GDR and Hungary. Pp. 245-251 in 3.
Spurenelement-Symposium, Nickel, M. Anke, H.-J. Schneider, and C.
BrUckner, eds. Jena: Friedrich-Schiller-Universitat.
Hill, C. H. 1979. The effect of dietary protein levels on mineral toxicity in
chicks. J. Nutr. 109:501-507.
Hopfer, S. M., J. V. Linden, W. N. Rezuke, J. E. O'Brien, L. Smith, F.
Walters, and F. W. Sunderman Jr. 1987. Increased nickel concentra-
tions in body fluids of patients with chronic alcoholism during disul-
firam therapy. Res. Comm. Chem. Pathol. Pharmacol. 55:101-109.
lOM (Institute of Medicine). 2000. Ai'senic, boron, nickel, silicon, and va-
nadium. Pp. 502-553 in Dietaiy Reference Intakes for Vitamin A, Vita-
min K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese,
Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, D.C.:
National Academy Press.
Kasprzak, K. 1987. Nickel. Pp. 145-183 in Genotoxic and Carcinogenic
Metals: Environmental and Occupational Occun'ence and Exposure, L.
Fishbein, A. Furst, and M. A. Mehlman, eds. Princeton, NJ: Princeton
Scientific Publishing.
Khangarot, B. S., and V. S. Durve. 1982. Note on the acute toxicity of zinc,
and the interactions of zinc and nickel to a freshwater teleost Channa
punctatus (Bloch). Indian J. Anim. Sci. 52:722-725.
Kim, E. J., H.-J. Chung, B. Suh, Y. C. Hah, and J.-H. Roe. 1998. Transcrip-
tional and post-translational regulation by nickel of sodN gene encoding
nickel-containing superoxide dismutase from Streptomyces coelicolor
MuUer. Mol. Microbiol. 27:187-195.
Kirchgessner, M., and F. X. Roth. 1977. Zum Einfluss von Ni-Zulagen auf
das Wachstum von Ferkeln. Z. Tierphysiol. Tierernaehr. Futtermittelkd.
39:277-281.
Kirchgessner, M., A. Schnegg, and F. X. Roth. 1980a. Zur Wirkung hoher
alimentarer Nickel-Zulagen. Pp. 309—313 in 3. Spurenelement-Sympo-
sium, Nickel, M. Anke, H.-J. Schneider, and C. Bruckner, eds. Jena:
Friedrich-Schiller-Universitat.
Kirchgessner, M., R. Sporl, and D. A. Roth-Maier. 1980b. Exkretion im
Kot und scheinbare Absorption von Kupfer, Zink, Nickel und Mangan
bei nichtgraviden und graviden Sauen mit unterschiedlicher
Spurenelementversorgung. Z. Tierphysiol. Tierernhr. Futtermittelkd.
44:98-111.
Kirchgessner, M., D. A. Roth-Maier, and R. Sporl. 1983. Spurenelement-
bilanzen (Cu, Zn, Ni, und Mn) laktierender Sauen. Z. Tierphysiol.
Tierernhr. Futtermittelkd. 50:230-239.
Kirchgessner, M., A.-M. Reichlmayr-Lais, andR. Maier. 1984a. Ni-Reten-
tion und Ni-Gehalte in Organen und Geweben nach unterschiedlicher
Ni-Versorgung bei Ratten. Z. Tierphysiol. Tierernahrg. Futtermittelkde.
52:27-34.
Kirchgessner, M., D. A. Roth-Maier, E. Grassman, and H. Mader. 1984b.
Verlauf der Fe-, Cu-, Zn-, Ni-, und Mn-Konzentration in Sauenmilch
wahrend einer ftinfwochigen Laktationsperiode. Arch. Teierernahrg.
32:853-858.
Langmyhr, F. J., and S. Orre. 1980. Direct atomic absorption spectrometric
determination of chromium, cobalt, and nickel in fish protein concen-
trate and dried fish solubles. Anal. Chim. Acta 1 18:307-31 1.
Ling, J. R., and R. M. Leach, Jr. 1979. Studies on nickel metabolism: inter-
action with other minerals. Poult. Sci. 58:591-596.
Marzouk, A., and F. W. Sunderman, Jr. 1985. Biliary excretion of nickel in
rats. Toxicol. Lett. 27:65-71.
Mathur, A. K. 1983. Effect of toxic amounts of dietary nickel in rats. Z.
Tierphysiol. Tierernahrg. Futtermittelkde 49:153-156.
Mathur, A. K., A. M. Reichlmayr-Lais, and M. Kirchgessner. 1982.
Wachstum, Futterverwertung und Proteingehalt einzelner Organe bei
unterschiedlicher Zink- und Nickelversorgung. Z. Tierphysiol.
Tierernhr. Futtermittelkd. 47:101-109.
McCoy, H., and M. A. Kenny. 1992. A review of biointeractions of Ni and
Mg. II. Immune system and oncology. Magnesium Res. 5:223-232.
Mtiller-Fassbender, M. B. Elsenhans, A. T. McKie, and K. Schumann.
2003. Different behaviour of ^-^Ni and -""'Fe during absorption in iron-
deficient and iron-adequate jejunal rat segments ex vivo. Toxicology
185:141-153.
Nation, J. R., M. F. Hare, D. M. Baker, D. E. Clark, and A. E. Bourgeois.
1985. Dietary administration of nickel: effects on behavior and
metallothionein levels. Physiol. Behav. 34:349—353.
Nieboer, E., R. T. Tom, and W. E. Sanford. 1988. Nickel metabolism in
man and animals. Pp. 91-121 in Metal Ions in Biological Systems, Vol.
23, Nickel and Its Role in Biology, H. Sigel and A. Sigel, eds. New
York: Marcel Dekker.
Nielsen, F. H. 1987. Nickel. Pp. 245-273 in Trace Elements in Human and
Animal Nutrition, 5th ed.. Vol. 1, W. Mertz, ed. San Diego: Academic
Press.
Nielsen, F. H. 1998. Ultratrace elements in nutrition: current knowledge
and speculation. J. Trace Elem. Exp. Med. 11:251—254.
Nielsen, F. H. 2001. The emergence of boron, nickel, silicon, vanadium,
and arsenic as elements of nutritional relevance. Pp. 93-104 in Trace
Elements in Nutrition, Health, and Disease, N. Antoniades, G. N.
Schrauzer, N. Renard, and J. Wozniak, eds. Montreal: Institut-Rosell-
The Americas.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
282
MINERAL TOLERANCE OF ANIMALS
Nielsen, F. H., and T. J. Zimmerman. 1981. Interactions among nickel,
copper, and iron in rats. Growth, blood parameters, and organ wt/body
wt ratios. Biol. Trace Elem. Res. 3:83-98.
Nielsen, F. H., T. R. Shuler, T. J. Zimmerman, M. E. Collings, and E. O.
Uthus. 1979. Interaction between nickel and iron in the rat. Biol. Trace
Elem. Res. 1:325-335.
Nielsen, F. H., T. R. Shuler, T. G. McLeod, and T. J. Zimmerman. 1984.
Nickel influences iron metabolism through physiologic, pharmacologic,
and toxicologic mechanisms in the rat. J. Nutr. 1 14:1280—1288.
Nielsen, F. H., T. J. Zimmerman, T. R. Shuler, B. Brossart, and E. O. Uthus.
1989. Evidence for a cooperative relationship between nickel and vita-
min B|2 in rats. J. Trace Elem. Exp. Med. 2:21-29.
Nomoto, S., and F. W. Sunderman, Jr. 1988. Presence of nickel in alpha-2-
macroglobulin isolated from human serum by high performance liquid
chromatography. Ann. Clin. Lab. Set. 18:78—84.
NRC (National Research Council). 1975. Medical and Biologic Effects of
Environmental Pollutants. Nickel. Washington, D.C.: National Acad-
emy Press.
NRC. 1980. Nickel. Pp. 345-363 in Mineral Tolerance of Domestic Ani-
mals. Washington. D.C.: National Academy Press.
O'Dell, G. D., W. J. Miller, W. A. King, S. L. Moore, and D. M. Blackmon.
1970. Nickel toxicity in the young bovine. J. Nutr. 100:1447-1454.
O'Dell, G. D., W. J. Miller, and S. L. Moore, W. A. King, J. C. Filers, and
H. Jurecek. 1971. Effect of dietary nickel level on excretion and nickel
content of tissues in male calves. J. Anim. Sci. 32:769—773.
Omokhodion, F. O., and J. M. Howard. 1994. Trace elements in the sweat
of acclimatized persons. Clin. Chem. Acta 231:23-28.
Oscar, T. P., and J. W. Spears. 1998. Nickel-induced alterations of in vitro
and in vivo ruminal fermentation. J. Anim. Sci. 66{9):2313-2324.
Pandey, R., and S. P. Singh. 2001. Seminal toxicity of nickel sulfate in
mice. Biol. Trace Elem. Res. 82:211-215.
Pandey, R., R. Kumar, S. P. Singh, D. K. Saxena, and S. P. Srivastava.
1999. Male reproductive effect of nickel sulphate in mice. Biometals
12:339-346.
Patriarca, M., T. D. B. Lyon, and G. S. Fell. 1997. Nickel metabolism in
humans investigated with an oral stable isotope. Am. J. Clin. Nutr.
66:616-621.
Phatak, S. S., and V. N. Patwardhan. 1950. Toxicity of nickel. J. Sci. Ind.
Res. 9B:70.
Predki, P. F., D. M. Whitfield, and B. Sarkar. 1992. Characterization and
cellular distribution of acidic peptide and oligosaccharide metal-bind-
ing compounds from kidneys. Biochem. J. 281:835—841.
Ptashynski, M. D., R. M. Pedlar, R. F. Evans, K. G. Wautier, C. L. Baron,
and J. F. Klaverkamp. 2001. Accumulation, distribution, and toxicology
of dietary nickel in lake whitefish (Coregonus clupeaformis) and lake
trout (Salvelinum namaycush). Comp. Biochem. Physiol. Part C.
Toxicol. Pharmacol. 130:145-162.
Ptashynski, M. D., R. M. Pedlar, R. E. Evans, C. L. Baron, and J. F.
Klaverkamp. 2002. Toxicology of dietary nickel in lake whitefish
(Coregonus clupeaformis). Aquatic. Toxicol. 58:229-247.
Ray, D.,S.K. Banerjee, andM.Chatterjee. 1990. Bioaccumulation of nickel
and vanadium in tissues of the catfish Clarias batrachus. J. Inorg.
Biochem. 38:169-173.
Regius, A., E. Sztics, M. Szilagyi, M. Anke, S. Szentmihalyi, and M.
Kemenes. 1983. Nickel-versorgung und biochemische Parameter bei
JungbuUen. Pp. 34-39 in 4. Spurenelement-Symposium. Jena:
Friedrich-Schiller-Universitat.
Sarkar, B. 1984. Nickel metabolism. Pp. 367-384 in Nickel in the Human
Environment, F. W. Sunderman Jr., A. Aitio, A. Berlin, C. Bishop, E.
Buringh, W. Davis, M. Gounar, P. C. Jacquignon, E. Mastromatteo, J.
P. Rigaut, C. Rosenfeld, R. Saracci, and A. Sors, eds. Lyon: Interna-
tional Agency for Research on Cancer.
Schnegg, A., and M. Kirchgessner. 1975. Veranderungen des
hamoglobingehaltes, der erythrozytenzahl und des hamatokrits bei
nickelmangel. Nutr. Metab. 19:268-278.
Schnegg, A., and M. Kirchgessner. 1976. Zur Toxizitat von alimentar
verabreichtem Nickel. Landwirtsch. Forsch. 29:177—185.
Schnegg, A., and M. Kirchgessner. 1977. Nickelgehalte in Rattenorganen
bei Nickelmangel. Zentralbl. Veterinaermed. Reihe A 24:394-401.
Schroeder, H. A., and M. Mitchener. 1971. Toxic effects of trace elements
on the reproduction of mice and rats. Arch. Environ. Health 23:102-106.
Smialowicz, R. J. 1998. Nickel. Pp. 163—194 in Immunotoxicity of Envi-
ronmental and Occupational Metals, J. T. Zelikoff and P. T. Thomas,
eds. London: Taylor & Francis.
Smith, M. K., E. L. George, J. A. Stober, H. L.A. Feng, and G. L. Kimmel.
1993. Perinatal toxicity associated with nickel chloride exposure.
Environ. Res. 61:200-211.
Solomons, N. W., F. Viteri, T. R. Shuler, and F. H. Nielsen. 1982.
Bioavailability of nickel in man. Effects of foods and chemically de-
fined dietary constituents on the absorption of inorganic nickel. J. Nutr.
112:39-50.
Spears, J. W., E. E. Jones, L. J. Sansell, and D. Ai'mstrong. 1984. Effect of
dietary nickel on growth, urease activity, blood parameters, and tissue
mineral concentrations in the neonatal pig. J. Nutr. 1 14:845—853.
Stangl, G. I., and M. Kirchgessner. 1996. Nickel deficiency alters liver lipid
metabolism in rats. J. Nutr. 126:2466-2473.
Stangl, G. I., and M. Kirchgessner. 1997. Effect of nickel deficiency on
fatty acid compostion of total lipids and individual phospholipids in
brain and erythrocytes of rats. Nutr. Res. 17:137-147.
Stangl, G. I., U. Eidelsburger, and M. Kirchgessner. 1998. Nickel defi-
ciency alters nickel flux in rat everted intestinal sacs. Biol. Trace Elem.
Res. 61:253-262.
Stangl, G. I., D. A. Roth-Maier, and M. Kirchgessner. 2000. Vitamin B-12
deficiency and hyperhomocysteinemia are partly ameliorated by cobalt
and nickel supplementation in pigs. J. Nutr. 130:3038-3044.
Sunderman, F. W., Jr. 1980. Analytical biochemistry of nickel. Pure Appl.
Chem. 52:527-544.
Sunderman, F. W., Jr., B. Dingle, S. M. Hopfer, and T. Swift. 1998a. Acute
nickel toxicity in electroplating workers who accidentally ingested a
solution of nickel sulfate and nickel chloride. Am. J. Ind. Med.
14:257-266.
Sunderman, F. W., Jr., S. M. Hopfer, and M. C. Crisostomo. 1988b. Nickel
analysis by electrothermal atomic absorption spectrometry. Methods
Enzymol. 158:382-391.
Sunderman, F. W., Jr., S. M. Hopfer, K. R. Sweeney, A. H. Marcus, B. M.
Most, and J. Creason. 1989. Nickel absorption and kinetics in human
volunteers. F^oc. Soc. Exp. Biol. Med. 191:5-11.
Sutherland, J. E., and M. Costa. 2002. Nickel. Pp. 349^07 in Heavy Metals
in the Environment, B. Sarkar, ed. New York: Marcel Dekker.
Tabata, M., and B. Sarkar. 1992. Specific nickel(II)-transfer process be-
tween the native sequence peptide representing the nickel(II)-transport
site of human albumin and L-histidine. J. Inorg. Biochem. 45:93-104.
Tallkvist, J., and H. Tjalve. 1997. Effect of iron-deficiency on the disposi-
tion of nickel in rats. Toxicol. Lett. 92:131-138.
Tallkvist, J., and H. Tjalve. 1998. Transport of nickel across monolayers of
human intestinal Caco-2 cells. Toxicol. Appl. Pharmacol. 151:117-122.
Triipschuch, A., M. Anke, H. Illing-Gtinther, M. Mtiller, and E. Hartmann.
1996. Toxicological aspects of nickel in hen, cock, and chicken. Pp.
127-136 in New Perspectives in the Research of Hardly Known Trace
Elements and Their Role in Life Processes. I. Pais, ed. Budapest: Uni-
versity of Horticulture and Food Industry.
USGS (U.S. Geological Survey). 2003. Nickel statistics and information.
Online. Available at http://minerals.usgs.gov/minerals/pubs/commod-
ity/nickel/. Accessed April 22, 2005.
Vyskocil, A., C. Viau, and M. Cizkova. 1994. Chronic nephrotoxicity of
soluble nickel in rats. Hum. Exp. Toxicol. 13:689-693.
Weber, C. W., and B. L. Reid. 1968. Nickel toxicity in growing chicks. J.
Nutr. 95:612-616.
Weber, C. W., and B. L. Reid. 1969. Nickel toxicity in young growing
mice. J. Anim. Sci. 28:620-623.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
NICKEL 283
Welch, R. M. 1981. The biological significance of nickel. J. Plant Nutr. Yokoi, K., E. O. Uthus, and F. H. Nielsen. 2003. Nickel deficiency dimin-
3:345-356. ishes sperm quantity and movement in rats. Biol. Trace Elem. Res.
Whanger, P. D. 1973. Effects of dietary nickel on enzyme activities and 93:141-153.
mineral contents in rats. Toxicol. Appl. Pharmacol. 25:323-331.
Wilson, J. H., E. J. Wilson, and P. L. Ruszler. 2001. Dietary nickel im-
proves male broiler {Gallus domesticus) bone strength. Biol. Trace
Elem. Res. 83:239-249.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
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23
Phosphorus
INTRODUCTION
Phosphorus (P) represents 0.12 percent of the Earth's
crust and has an atomic number of 15 and an atomic weight
of 30.97. In nature, the free elemental form of phosphorus is
too reactive to exist. Thus, phosphorus is often found com-
bined with oxygen as inorganic or organic phosphates
(Berner, 1997). The organic phosphates used as insecticides
or herbicides are highly toxic, and are beyond the scope of
this review. The inorganic phosphates share the same basic
anionic unit of orthophosphate: a tetrahedron structure of
one phosphorus atom surrounded by four oxygen atoms, and
the chemical forms of these salts can be simply classified as
monovalent (sodium, potassium, and hydrogen); divalent
(calcium and magnesium); ammonium; and aluminum
(Weiner et al., 2001). The inorganic phosphates are widely
used as chemical fertilizers, food and feed supplements, and
industrial compounds including detergents, fire extinguish-
ers, toothpaste, and textile processors. Igneous rocks are the
ultimate source of phosphorus, and pellet phosphorite and
guano are the two major sedimentary deposits for the pro-
duction of feed phosphates (McDowell, 2003). In 2002, ap-
proximately 36 million tons of marketable phosphate rock
ore were mined in the United States, mainly in Florida and
North Carolina (USGS, 2003). Morocco and Western Sa-
hara, China, and Russia are the next three largest producers
and reserves of phosphate rock in the world.
ESSENTIALITY
As the sixth most abundant element in the body, phos-
phorus is involved in virtually every aspect of metabolism.
In bone, phosphorus serves as a structural component of crys-
talline hydroxyapatite: Ca|Q(P04)g(0H),, and is deposited in
the organic matrix during mineralization. Therefore, phos-
phorus deficiency causes rickets in young animals and os-
teomalacia in adult animals. In soft tissues, phosphorus plays
both structural and metabolic roles as a component of phos-
pholipids, DNA, RNA, nucleotides (e.g., ATP, cAMP, uri-
dine di-P-glucose), and enzyme cofactors. In extracellular
fluids, approximately 30 percent of phosphorus exists as in-
organic phosphate ions that help maintain osmotic pressure,
acid-base balance, neuron activity, and appetite (Berner,
1997). In ruminants, phosphorus is essential for proper func-
tioning of rumen microorganisms (NRC, 2001; Guyton et
al., 2003). Dietary nutrient requirements of phosphorus (non-
phytate) by various species range from 0.2 to 0.8 percent,
and may be affected by age, physiological stage, perfor-
mance, and dietary levels of calcium and vitamin D
(McDowell, 2003). Based on performance results, Erickson
et al. (2002) suggested that the phosphorus requirement for
finishing calves was <0.16 percent of diet DM and could be
met by typical grass-based feedlot cattle diets without
supplemental inorganic phosphorus.
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Total phosphorus contents in feeds, feces, urine, and tis-
sues are readily determined using colorimetric methods
(Garcia-Bojaliletal., 1988; Cymbaluk and Christison, 1989;
AOAC, 1995), a gravimetric procedure (AOAC, 1995), or
an inductive coupling plasma atomic emission spectrometry
instrument (Hutcheson et al., 1992). Initially, feed or fecal
samples are ground, urinary samples are evaporated, and
bone samples are crushed and the fat is extracted. These
samples can then be dry-ashed in a muffle furnace (550°-
600°C) (Boling et al., 2000) or wet-digested by either sulfu-
ric acid-hydrogen peroxide or perchloric-nitric acid (Budde
and Crenshaw, 2003) and diluted to appropriate concentra-
tions for analysis. Inorganic phosphorus concentrations in
serum or plasma samples are assayed directly using sodium
molybdate and Elon (p-methylaminophenol sulfate) solution
(Gomori, 1942), after the samples are deproteinated with
trichloroacetic acid (Gentile et al., 2003). This method does
not measure phosphorus associated with phospholipids.
290
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PHOSPHORUS
291
There are two challenges related to phosphorus analysis.
One is the lack of simple and reliable methods to determine
various chemical forms of phosphorus, such as phytate-P
and its intermediate metabolites in feed and digesta (Rapp et
al., 2001; Applegate et al., 2003). Phytate-P represents a
large portion of phosphorus in plant-based diets that is poorly
available to nonruminant species (Lei and Stahl, 2001). In
addition, dietary phytate-P intake by certain species may af-
fect their actual tolerable levels of dietary phosphorus. Thus,
an effective analysis of phytate and its hydrolytic products
will help cope with these problems. The other challenge is
the need for accurate and sensitive assessments of phospho-
rus status in vivo. Although biopsies of ribs, toes, or tail-
bones (Little and Minson, 1977; Combs etal., 1991a) as well
as x-ray equipment, dual photon absorptiometry, radio-
graphic photometry, and ultrasound (Ternouth, 1990; Will-
iams et al., 1991b) have been applied to assay for body phos-
phorus status, ash contents in selected entire bones
postmortem are still the commonly used criterion for that
purpose (Williams et al., 199 la; Boling et al., 2000; Erickson
et al., 2002). Urinary hydroxyproline concentrations and
pyridinium X-links (McLean et al., 1990) have been sug-
gested as a prognostic tool to determine bone demineraliza-
tion in racing horses (Price et al., 1995). Serum concentra-
tions of osteocalcin, a small noncollagenous bone protein,
may be a good indicator of bone turnover in growing pigs
(Carter et al., 1996).
REGULATION AND METABOLISM
Absorption and Metabolism
Both active transport and passive diffusion are suggested
as the mechanisms of phosphate absorption in small intes-
tines (Berner, 1997). Active transport occurs in the proximal
small intestine and is a sodium-dependent event that is pro-
moted by the active metabolite of vitamin D3 (Danisi and
Straub, 1980). Passive diffusion takes place mainly in the
jejunum and ileum, and is directly related to the dietary phos-
phorus intake and the lumen phosphorus concentrations.
Using growing pigs (40-58 kg) fitted with a simple T-can-
nula at the distal ileum, Ajakaiye et al. (2003) demonstrated
that the large intestine played no major role in the digestion
of phosphorus associated with soybean meal. In contrast,
Schryver et al. (1972) showed that the dorsal large colon and
the small colon were the major sites of net phosphorus ab-
sorption from various feed sources in ponies. They found no
effect of either the calcium content or the source of feedstuff
on the site of absorption.
The apparent absorption coefficients of dietary supple-
mental inorganic phosphates normally fall between 70 and
90 percent for both ruminants and nonruminants
(Braithwaite, 1986; Challa et al., 1989; Cromwell, 1992).
However, phosphorus in plant feeds, mainly as phytate-P,
can be efficiently digested by ruminants, due to their rumen
microorganisms (Field et al., 1984; NRC, 2001). The appar-
ent absorption coefficients of phosphorus in total rations for
dairy cows range from approximately 30 to 60 percent
(Knowlton et al., 2001; Valk et al., 2002; Wu et al., 2003;
Borucki Castro et al., 2004; Weiss and Wyatt, 2004). Wether
lambs fed concentrate-based diets containing 9 percent
highly weathered soil with high phosphorus-fixation capac-
ity had apparent phosphorus absorption between 4 and 19
percent, but true absorption up to 54 percent (Garcia-Bojalil
et al., 1988). Pregnant and lactating does absorbed (appar-
ent) 23-42 percent of phosphorus in a diet of alfalfa, concen-
trates, and minerals (Fredeen et al., 1988). Growing pigs
absorbed (apparent) 24-51 percent of phosphorus in soy-
bean meal (Ajakaiye et al., 2003), whereas weanling pigs
absorbed only 13 percent of phosphorus in a corn-soy diet
(Spencer et al., 2000). Growing horses fed high forage diets
(73-77 percent alfalfa) or high concentrate diets (63-65 per-
cent grain and grain by-products) absorbed (apparent) 17-39
percent of total dietary phosphorus, and the apparent absorp-
tion coefficient decreased as dietary phosphorus rose from
0.68 to 1.06 percent (Cymbaluk and Christison, 1989). Like-
wise, dietary phosphorus level and body phosphorus status
affected the apparent absorption of phosphorus in fish
(Vielma and Lall, 1998). When dietary phosphorus was in-
creased from 0.4 to 1.33 percent, the pooled apparent ab-
sorption coefficient was reduced from 73.8 to 63.6 percent.
The phosphorus-replete fish had lower phosphorus absorp-
tion than the phosphorus-deficient ones.
The absorbed phosphorus may be retained in the body,
used for milk or egg production, or excreted into feces and
urine. The circulating blood phosphorus is present as both
phospholipids and inorganic phosphates. In lactating cows,
milk phosphorus as a percentage of dietary phosphorus in-
take decreased from approximately 65 to 22 percent when
dietary phosphorus increased from 0.33 to 0.67 percent
(Knowlton and Herbein, 2002; Guyton et al., 2003). How-
ever, milk phosphorus concentrations or milk yields were
not affected by those levels of dietary phosphorus intake
(Knowlton and Herbein, 2002; Dou et al., 2003). Large quan-
tities of phosphorus (30-90 g/day) are secreted in saliva dur-
ing rumination, serving as the major source of phosphorus
flowing into the rumen of cattle and sheep (Challa and
Braithwaite, 1989; Valk et al., 2002; Guyton et al., 2003).
Approximately 68-81 percent of the salivary phosphorus, in
the form of sodium or potassium phosphates, is absorbable
after being recycled to the small intestine in bull calves
(Challa et al., 1989). Excessive phosphate is excreted prima-
rily via feces (Lei et al., 1993b; Knowlton et al., 2001; Dou
et al., 2002, 2003; Bravo et al., 2003; Weiss and Wyatt,
2004). Kidney (urine) plays an important role in phosphorus
excretion in nonruminants and ruminants fed high levels of
concentrate (Underwood and Suttle, 1999). In all cases, there
is a certain amount of endogenous phosphorus loss, even in
phosphorus deficiency. That phosphorus loss in feces of
growing goats was extrapolated to be 0.067 g/day (Vitti et al..
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MINERAL TOLERANCE OF ANIMALS
2000). In growing pigs, the endogenous phiosphorus loss in
feces accounted for 8 percent and 18 percent of tiie recom-
mended total and available phosphorus requirements, respec-
tively (Ajakaiye et al., 2003). Urinary phosphorus excretion
was increased in weanling pigs fed an alkalinogenic diet over
those fed an acidogenic diet (Budde and Crenshaw, 2003).
Metabolic Interactions, Regulations, and Mechanism of
Toxicities
Body phosphate homeostasis in nonruminant species is
maintained primarily by three organs/tissues — intestine, kid-
ney, and bone — and three hormones — parathyroid hormone
(PTH), l,25-(OH)2D3, and calcitonin. These organs and hor-
mones function cooperatively in regulating absorption, ex-
cretion, and deposition/resorption of phosphates in the body,
maintaining a constant exchanging pool among various phos-
phates in the plasma. In the small intestine, active 1,25-
(OH)-,D3 promotes phosphate absorption, independent of its
effect on calcium absorption (Peterlik and Wasserman, 1978;
Kabakoff et al., 1982). In the bone, l,25-(OH)2D3 enhances
mobilization (resorption) of phosphate and calcium
(Kowarski and Schachter, 1969). In the kidney, 1,25-
(OH)2D3 promotes phosphate reabsorption, whereas PTH
and calcitonin (Lang et al., 1981) exert the exact opposite
roles. Homeostasis of phosphorus in ruminants is maintained
primarily by salivary recycling (NRC, 2001). Although sig-
nificant differences in liver, muscle, and plasma concentra-
tions of l,25-(OH)2D3 were found among three biological
types of beef cattle (Montgomery et al., 2004), dietary phos-
phorus intake, ranging from 0.7 to 3 times the maintenance
requirement, had no effect on plasma concentrations of 1,25-
(OH),D3 in aged dairy cows (Barton et al., 1987). In fish,
phosphorus homeostasis is also mediated by absorption in
the intestine, reabsorption in the kidney, and deposition in
bones (Vielma and Lall, 1998). However, the exact molecu-
lar mechanisms of the regulation, including the role of vita-
min D and the importance of an appropriate
calcium:phosphorus ratio, are largely unclear (Lall, 2002).
Normal phosphorus nutrition and metabolism requires
adequate levels of dietary calcium and an appropriate ratio
of calcium:phosphorus (Littledike and Goff, 1987). Without
adequate available calcium, phosphates cannot be deposited
into the bones. However, excess dietary calcium forms in-
soluble complexes with phosphate or phytate in the intes-
tine, rendering phosphorus unavailable for absorption (Lei
et al., 1994; Liu et al., 2000). In addition, high levels of se-
rum calcium inhibit the synthesis of l,25-(OH)2D3, reducing
phosphorus absorption in intestines (Lau et al., 1984). There-
fore, it is difficult to produce or distinguish clinical signs of
the primary phosphorus deficiency or toxicity, without con-
founding calcium or vitamin D nutrition. In many cases,
phosphorus toxicity is produced by a relative excess of phos-
phorus in relation to low calcium. As high plasma phospho-
rus concentrations, associated with high dietary phosphorus
intake, cause the lowering of plasma calcium, the parathy-
roid gland is subsequently stimulated to release more PTH to
increase plasma calcium by accelerating bone resorption and
renal phosphate excretion. Prolonged bone resorption leads
to pronounced bone loss, so that the demineralized skeleton
may be replaced by fibrous connective tissues (Bartter, 1964;
NRC, 1980).
SOURCES AND BIOAVAILABILITY
Plant feeds, inorganic phosphate supplements, and bone,
meat, poultry, and fish meals serve as the major sources of
phosphorus for animals. Bioavailability of phosphorus from
these sources is estimated by a variety of criteria. In some
cases, the digestibility of phosphorus, as discussed above, is
simply considered equivalent to bioavailability. Most times,
phosphorus bioavailability is determined based on the effec-
tiveness of a given source, relative to that of selected, highly
available sodium or calcium phosphates (Cromwell, 1992),
in improving performance, bone strength and integrity, and
biochemical responses. Temperate or tropical forages con-
tain 2.3-3.5 g P/kg (DM basis, Minson, 1990), and the phos-
phorus availability ranges from 64 to 86 percent to sheep
(Field et al., 1984; Scott et al., 1995) and cattle (Martz et al.,
1990). Plant protein feeds such as oilseed meals contain
higher levels of phosphorus than those in cereals (5-12 vs.
2.7-4.3 g P/kg DM) (Reddy et al., 1982). Only 12-35 per-
cent of the total phosphorus in most of these feeds is avail-
able to swine and poultry because of the high concentrations
of phytate-phosphorus (Kornegay, 1996). In contrast, wheat,
triticale, rye, and their byproducts have much higher phos-
phorus bioavailability (~50 percent) to nonruminant species
due to their high intrinsic phytase activities (Pointillart, 199 1 ;
Han et al., 1997). The recently developed low-phytate corn
has higher phosphorus availability to swine and poultry than
normal corn (Spencer et al., 2000; Sands et al., 2001). Low-
phytate soybean meal also has higher phosphorus
bioavailability than normal soybean meal (Cromwell et al.,
2000). The apparent digestibility of total ration phosphorus
for dairy cows ranges from 30 to 60 percent (Knowlton et
al., 2001 ; Valk et al., 2002; Wu et al., 2003; Weiss and Wyatt,
2004).
The phosphorus content in commonly used mineral salts
for animal feeds ranges from 9 to 24 percent. Bone meal
contains approximately 12.5 percent of phosphorus. More
than 95 percent of phosphorus is available to swine and poul-
try from the following sources: hydrated dicalcium phos-
phate, monosodium phosphate, ammonium phosphate, fish
meal, meat meal, meat and bone meal, monocalcium phos-
phate, potassium phosphate monobasic, monosodium phos-
phate, phosphoric acid, poultry by-product meal, tricalcium
phosphate, and urea phosphate (Scares, 1995). In compari-
son, phosphorus in bone meal, blood meal, Curacao Island
phosphate, defluorinated phosphates, and dried poultry waste
is slightly less available (85-90 percent, Coffey et al., 1994).
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PHOSPHORUS
293
However, phosphorus in metaphosphates and pyrophos-
phates is poorly available to nonruminants (Soares, 1995).
Inorganic phosphorus is virtually completely (99 percent)
available to fish, whereas the organic phosphorus is approxi-
mately 40 percent available (Roy and Lall, 2003).
There are several important issues related to the phospho-
rus supplementation. First, ground rock phosphate may be
contaminated with high levels of fluoride (3-4 percent), re-
sulting in fluoride toxicity. Second, the recent occurrence of
bovine spongiform encephalopathy has resulted in restric-
tions against supplementing bone and meat meals of rumi-
nant origin in diets. Third, inorganic phosphorus is a nonre-
newable resource, and the readily available inorganic
phosphorus deposit on Earth may be exhausted in 2080 at
the current extraction rate (Forsberg et al., 2003). Last, and
most important, high levels of manure phosphorus from the
undigested phytate-phosphorus and/or excessive supplemen-
tation may cause environmental pollution. In many parts of
the world, the phosphorus content of manure becomes the
first factor limiting the manure application to arable land
(Kornegay, 1996; Weiss and Wyatt, 2004; Koelsch, 2005).
Microbial phytases have been developed and supple-
mented into diets for swine, poultry, and fish to reduce phos-
phorus pollution of the environment from their waste (Lei
and Porres, 2003). There is a dose-dependent effect of
phytase on phytate-phosphorus bioavailability to both swine
and poultry (Nelson et al., 1971; Simons et al., 1990,
Cromwell et al., 1993), and 500 units of phytase activity per
kilogram of feed may reduce dietary inorganic phosphorus
supplementation by half and manure phosphorus concentra-
tion by 30-50 percent (Lei et al., 1993b; Augspurger et al.,
2003). In addition, phytase can improve bioavailability of
calcium, iron, and zinc by releasing them from phytate (Lei
et al., 1993a,b; Stahl et al., 1999). However, degradation of
phytate may release chelated lead (Pallauf and Rimbach,
1997; Zacharias et al., 1999), and render animals susceptible
to oxidative stress mediated by high levels of dietary iron
(Porres et al., 1999).
TOXICOSIS
Toxicosis from phosphorus is rather rare in food-produc-
ing animals. Although plant-based diets may meet nutrient
requirements of phosphorus for ruminants (Wu et al., 2001;
Erickson et al., 2002), concentrations and the
bioavailabilities of phosphorus in those diets are too low to
meet the needs for nonruminant species. Inorganic phospho-
rus supplements as feed ingredients are fairly expensive.
Moreover, phosphate is readily excreted via urine, and
thereby is well-tolerated (Underwood and Suttle, 1999).
Thus, animals can tolerate a wide range of dietary phospho-
rus intakes if their diets are balanced with calcium. In many
cases, the phosphorus toxicity is associated with metabolic
disorders of calcium absorption and function, produced by a
relative excess of phosphorus in relation to low calcium.
Nevertheless, high levels of phosphorus may still be detri-
mental to animals even in the presence of adequate calcium
(Laflamme and Jowsey, 1972; Carstairs et al., 1981;
Matsuzaki et al., 1997).
Single Dose and Acute
Based on the review of 96 published and unpublished (by
industry) studies in laboratory species (rats, mice, hamsters,
rabbits, and guinea pigs), Weiner et al. (2001) concluded
that all tested groups of inorganic phosphates, including
phosphoric acid (Randall and Robinson, 1990), exhibited
low acute oral toxicities. Among all the salts, tetrasodium
pyrophosphate (Na^PjO^) showed the lowest LD^q (1.38 g
of compound/kg BW) and sodium trimetaphosphate
(NaPOj)^ showed the highest LDjQ (10.6 g of compound/kg)
in rats.
Chronic
Urolithiasis (urinary calculi) can be produced by a relative
excess of phosphorus in relation to calcium in ruminants. The
malady is caused by the formation of stones or calculi in the
kidney or bladder, resulting in obstruction of urine excretion,
particularly in males. The continuous buildup of urine in the
bladder eventually ruptures the bladder or urethra, followed
by abdominal distension, depression, and death due to uremia.
The incidence was approximately 70 percent in male lambs
fed a high level of phosphorus (0.8 percent) and low calcium
(0.44 percent), and also occurred in lambs fed lower levels of
phosphorus (Table 23-1, Emerick and Embry, 1963, 1964).
Different forms of sodium phosphates appeared to have equal
ability to produce calculi, but elevating dietary calcium levels
partially protected against the incidence in sheep (Bushman et
al., 1965). Grazing sheep (45 kg BW) tolerated orthophospho-
ric acid and monosodium phosphate, administrated in water,
up to 1 .5 and 3.0 g of phosphorus per day for 70 days, respec-
tively (McMeniman, 1973). However, all sheep died of re-
ceiving orthophosphoric acid at 3 g of phosphorus per day.
Nutritional secondary hyperparathyroidism can be induced
in horses by low calcium, high phosphorus diets (Joyce et al.,
1971). The disorder is also called fibrous osteodystrophy and
is produced by an increased serum inorganic phosphorus and
a decreased serum calcium concentration. As mentioned
above, the low serum calcium stimulates the secretion of PTH,
causing bone resorption and the replacement of the deminer-
alized skeleton by fibrous connective tissue (Bartter, 1964).
When horses are fed high levels of wheat bran that contains
high phosphorus (1.15 percent) and low calcium (0.14 per-
cent), their facial bones become enlarged by the invasion of
the fibrous connective tissue in the area with significant cal-
cium mobilization. Thus, it is sometimes called "bran disease"
or "big head disease." A diet with a calcium:phosphorus ratio
of 0.8: 1.0 or lower may produce the symptom within 6 to 12
months (NRC, 1989). In this case, the high phosphorus intake
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MINERAL TOLERANCE OF ANIMALS
decreases calcium absorption, plasma calcium concentration,
and renal calcium excretion, but increases both rates of cal-
cium deposition and removal in bones (Schryver et al., 1971;
Argenzio et al., 1974).
No signs of toxicosis were seen in Holstein-Friesian cows
fed 0.69 percent dietary phosphorus (dry basis) for 14 weeks
prepartum through 22 weeks of lactation (DeBoer et al.,
1981). However, a similar level of dietary phosphorus (0.64
percent) reduced magnesium absorption in pregnant dairy
heifers (Schonewille et al., 1994), compared with a lower
level of phosphorus (0.22 percent). Primiparous cows fed
0.5 percent phosphorus (DM basis) showed depressed milk
production during the second and third months of lactation
compared to those fed 0.4 percent phosphorus (Carstairs et
al., 1981). As high blood phosphorus inhibits the production
of active vitamin D, high phosphorus intake (80 g/cow/d)
during late pregnancy may increase the incidence of milk
fever and hypocalcemia at parturition (Reinhardt and
Conrad, 1980). However, feeding cows three times the main-
tenance requirement of phosphorus (0.69 percent phospho-
rus) for 28 days precalving showed an effect on the inci-
dence of parturient paresis (Barton et al., 1987). Cows fed
dietary phosphorus up to 0.67 percent (DM basis) showed
no adverse response in milk production in long (2- to 3-year)
experiments (Wu et al., 2000, 2001; Knowlton and Herbein,
2002) or under field conditions (Cerosaletti et al., 2004).
Similarly, there was no difference in health or reproductive
performance between cows fed 0.37 and 0.57 percent of
phosphorus (dry basis) (Lopez et al., 2004a,b).
With appropriate dietary calcium:phosphorus ratios (1.3
to 2: 1), pigs exhibited no adverse response in growth perfor-
mance and/or bone traits to various dietary phosphorus lev-
els up to 0.9 percent (Reinhart and Mahan, 1986; Combs et
al., 199 1 b,c; Hall etal., 1991). However, dietary phosphorus
in excess of 1 percent resulted in a quadratic decrease in feed
use efficiency in growing pigs (Crenshaw, 1986). High di-
etary phosphorus, combined with very low calcium, also pro-
duced nutritional secondary hyperparathyroidism in pigs
(Brown et al., 1966). Depressed egg production and eggshell
quality was observed in laying hens fed 0.8-1.2 percent
phosphorus (Harms et al., 1965; Charles and Jensen, 1975).
The acid-base balance was disturbed by feeding high levels
of acidogenic monobasic phosphate [Ca(H2P04)T]
(Keshavarz, 1994). Egg production was reduced from 90 to
70 percent and feed intake was reduced from 105 to 78 g per
hen per day when monobasic phosphate was supplemented
at 1 percent phosphorus. In contrast, no adverse effect was
produced by supplemental dibasic phosphate (CaHP04) at
2.0-2.4 percent phosphorus on performance or at 1.3 percent
phosphorus on eggshell quality. Feeding broilers with 0.55-
0.83 percent nonphytate-phosphorus (0.8-1.1 percent total
phosphorus) rendered the birds susceptible to tibial dyschon-
droplasia, and the disorder could be alleviated by feeding
high levels of calcium (1.5-1.7 percent) (Edwards and
Veltmann, 1983).
Rapid bone loss and detached incisor teeth were seen in
beagles fed a purified diet containing 1.2 percent phospho-
rus and 0.12 percent calcium (Krook et al., 1971). These
disorders were associated with accelerated bone resorption
mediated by PTH (Krook et al., 1971; Laflamme and Jowsey,
1972). When young adult dogs were fed three condensed
sodium phosphates (poly-, tripoly-, and trimeta-phosphate)
at 100 mg compound/kg per day for 30 days, no adverse
effect was observed (Hodge, 1964). But, dogs fed higher
levels of these phosphates (1-4 g/kg per day) for 5 months
showed weight loss, alterations in eosinophil counts or in the
proportion of neutrophils, increased heart weights, hypertro-
phy of the left ventricle, and tubular damage in the kidney.
When dogs were fed 800 mg of dipotassium phosphate/kg
per day for 14 or 38 weeks (Schneider et al., 1980a,b), the
animals were vomiting, cachectic, and high in urine creati-
nine and blood urea nitrogen. There was also renal damage
(disseminated tubular atrophy, focal scar tissue, and nephro-
calcinosis).
Accelerated bone resorption was produced by 1 .2 percent
dietary phosphorus in adult rats fed a diet containing the
same level of calcium (Anderson and Draper, 1972). Cumu-
lative excretion of "^^Ca was increased, but urinary calcium
excretion was decreased in rats fed 0.6 to 1.8 percent phos-
phorus compared to those fed 0.3 percent phosphorus (0.6
percent calcium) (Draper et al., 1972). Rats fed 1.8 percent
or higher disodium phosphate, sodium tripolyphosphate, and
tetrasodium pyrophosphate for 6 months or longer exhibit
growth retardation, increased kidney weight, and renal cal-
cification (Hahn, 1961). Nephrocalcionosis appeared in rats
fed 1.2 percent phosphorus or high levels (Matsuzaki et al.,
1997, 2001). These rats also had increased kidney weight
and calcium and phosphorus concentrations, elevated urine
volume, and high urine concentrations of albumin, N-acetyl-
beta-d-glucosaminidase activity, and beta 2-microglobulin.
Similar impacts of excess dietary phosphorus in relation to
calcium have also been seen in other laboratory species
(Table 23-1). When dietary phosphorus levels exceeded 1.2
percent, both Atlantic salmon reared in fresh water (Vielma
and Lall, 1998) and juvenile haddock reared in seawater (Roy
and Lall, 2003) showed depressed BW and feed use effi-
ciency and increased mortality. The magnesium and zinc
concentrations in the fish vertebrae ash were inversely cor-
related with dietary phosphorus levels (Vielma and Lall,
1998).
A number of inorganic phosphates have been tested in a
series of standard systems, and no genotoxicity, mutagenic-
ity, teratogenicity, or reproductive toxicity was observed at
adequate or high levels (Weiner et al., 2001).
Factors Influencing Toxicity
Since high dietary phosphorus can often cause secondary
reductions in Ca absorption, phosphorus toxicity may be pre-
vented or alleviated by feeding higher levels of dietary cal-
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PHOSPHORUS
295
cium. Excessive dietary magnesium promotes ttie formation
of urinary calculi in sheep fed high phosphorus diets by en-
hancing the formation of magnesium phosphates that are in-
tegral to the growth of the phosphate calculi (Suttle and Hay,
1986). The acidogenic effects of monobasic phosphates on
the performance or eggshell quality of laying hens can be
ameliorated by alkaline salts of sodium or potassium bicar-
bonate (Keshavarz, 1994). Female rats are more prone to the
high-phosphorus-induced nephrocalcinosis than male rats
(Matsuzaki et al., 2002). Polyphosphate salts produce more
severe nephrocalcinosis and kidney dysfunction than mono-
phosphates in rats (Matsuzaki et al., 1999). Sodium alumi-
num phosphate, with a low solubility, has a lower toxicity
than other phosphates (Weiner et al., 2001).
TISSUE LEVELS
Phosphorus comprises approximately 1 percent of BW.
As 85 percent of body phosphorus is in bone, it has the high-
est phosphorus concentration of all tissues. On a dry, fat-free
basis, different bones of various species contain 9-13 per-
cent phosphorus that represents 11-20 percent of bone ash
(Table 23-2). In most cases, bone ash, instead of bone phos-
phorus, is used to measure the effects of dietary supplemen-
tal phosphorus or phytase (Auspurger et al., 2003) because
bone ash has a fairly constant concentration of phosphorus.
However, deposits of phosphorus in bone, particularly in
long bones, decrease with dietary phosphorus depletion
(Underwood and Suttle, 1999; Wu et al., 2001), but remain
fairly constant if dietary phosphorus levels are met or above
the nutrient requirements (Draper et al., 1972).
Although 14-20 percent of the body phosphorus is in the
soft tissues (Berner, 1997; Underwood and Suttle, 1999;
McDowell, 2003), phosphorus concentrations in these tis-
sues have been reported in only a few studies. Based on the
limited data, the values range from 0.4 to 0.8 percent on a
dry basis in several species (Table 23-2). As the main target
organ of phosphorus toxicity, kidney can deposit high levels
of phosphorus (up to 7.8 percent) and calcium (Matsuzaki et
al., 1997). Effects of dietary phosphorus on plasma or serum
inorganic phosphorus concentration have been assayed in
many studies. The plasma inorganic phosphorus concentra-
tion, ranging from 20 to 100 mg/L, is slightly lower than that
in serum, but much lower than that in the whole blood. Al-
though the inorganic phosphorus in the blood represents only
0.3 percent of total body phosphorus, it is often sampled to
assay for the body phosphorus status because it is very re-
sponsive to dietary phosphorus intake (De Boer et al., 1981;
Reinhart and Mahan, 1986; Williams et al., 1991c; Erickson
et al., 2002; Gentile et al., 2003; Lopez et al., 2004a,b). The
phosphorus concentrations of milk from different species
range from 0.6 to 1.6 g/L, but do not vary greatly with di-
etary phosphorus intakes within a given species (Table 23-
2). In fish, both plasma and vertebrae phosphorus contents
were increased as dietary phosphorus levels rose to approxi-
mately 1 percent (Roy and Lall, 2003; Vielma and Lall,
1998).
MAXIMUM TOLERABLE LEVELS
Assuming the presence of adequate levels of dietary cal-
cium, the previous NRC (1980) committee suggested the
following maximum tolerable levels of phosphorus (percent
of diet): cattle, 1; sheep, 0.6; swine, 1.5; poultry, 1; laying
hen, 0.8 percent; horse, 1; and rabbit, 1. Although there are
insufficient new data, in particular from studies designed for
testing maximum tolerance, to completely revise all these
levels, several modifications and additions seem to be neces-
sary. The maximum tolerable level of phosphorus for cattle
is suggested to change from 1 to 0.7 percent (DM basis).
This is because the 1 percent level stated by the previous
committee was not specifically documented or justified and
recent studies have shown that cattle performance or health
were not affected by feeding dietary phosphorus up to 0.7
percent (DM basis, DeBoer et al., 1981; Knowlton and
Herbein, 2002). As limited research has shown a decline in
feed efficiency in pigs fed dietary phosphorus in excess of 1
percent (Crenshaw, 1986), it is appropriate and practically
relevant to reduce the maximum tolerable level of phospho-
rus for swine from 1.5 to 1 percent. While the improved
phytate-phosphorus use by supplemental phytases in diets
for swine and poultry may shift the maximum tolerable lev-
els of phosphorus downward, the release of phytate-bound
calcium by phytase (Lei et al., 1993a) can help these animals
cope with excess phosphorus. However, the increasing con-
cern over manure phosphorus pollution of environment in
the areas of intensive animal agriculture favors the lowering
of dietary phosphorus levels. There is a limited amount of
fish data to suggest the maximum tolerable level of phos-
phorus for this species as approximately 1 percent.
Based on the results from the studies presented in Table
23-1, rodents may be able to tolerate 0.6 percent phosphorus
in diets. Weiner et al. (2001) have reviewed multiple
subchronic (28-100 days) and chronic (21-104 weeks) tox-
icity studies of inorganic phosphates in laboratory animals,
and concluded that kidney is the primary target organ of high
phosphorus doses and that nephrocalcinosis and other renal
disorders are due to the excessive phosphorus and calcium
loads. A single subchronic and chronic NOEL (no-observed-
effect level)/NOAEL(no-observed-adverse-effect level) has
been suggested as 103 and 225 mg of compound/kg BW per
day for all classes of inorganic phosphates, respectively
(Weiner et al., 2001). Based on animal data, humans can
tolerate up to 1 percent phosphorus in the diet or 70 mg/kg
BW per day over a lifetime (Weiner et al., 2001).
FUTURE RESEARCH NEEDS
Recently, microbial phytases have been used in diets for
nonruminants to improve their use of phytate-phosphorus
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MINERAL TOLERANCE OF ANIMALS
and to reduce their phosphorus excretion to the environment.
Because of the release of phytate-phosphorus and the che-
lated calcium or other metals by these enzymes, the impact
on the maximum tolerable phosphorus levels in their diets
for swine and poultry should be examined.
SUMMARY
Direct toxic effects of phosphorus in food-producing
animals, particularly in simple-stomached species, are more
of a scientific issue than a practical concern. This is be-
cause (1) the amount of bioavailable phosphorus in plant-
based feeds is low; (2) supplemental inorganic phosphorus
is expensive; and (3) inorganic phosphates are intrinsically
well tolerated and readily excreted via urine. Single large
doses of phosphorus or short-time exposure to high levels
of phosphorus produce only minor effects in the animals.
However, prolonged exposure to high levels of dietary
phosphorus does cause metabolic disorders such as uroli-
thiasis in ruminants, nutritional secondary hyperparathy-
roidism in horses, and nephrocalcinosis in rats. Many of
these phosphorus toxic effects are only observed when cal-
cium intake is marginal or low. Most species, including
fish, may tolerate 1 percent phosphorus in their diets,
whereas the tolerable level is lower for sheep based on their
susceptibility to urolithiasis.
REFERENCES
Agboola, H. A., V. R. Caliill, H. R. Conrad, H. W. Ockerman, N. A. Parrett,
and R. F. Plimpton. 1988. Tlie effects of a liigh monosodium pliosphate
and alplia tocopherol supplemented milk replacer diet on veal muscle
color and composition. J. Anim. Sci. 66:1676-1685.
Ajakaiye, A., M. Z. Fan, T. Archbold, R. R. Hacker, C. W. Forsberg, and J.
P. Phillips. 2003. Determination of true digestive utilization of phos-
phorus outputs associated with soybean meal for growing pigs. J. Anim.
Sci. 81:2766-2775.
Anderson, G. H., and H. H. Draper. 1972. Effect of dietary phosphorus on
calcium metabolism in intact and parathyroidectomized adult rats. J.
Nutr. 102:1123-1132.
AOAC. 1995. Official Methods of Analysis, 16th ed. Washington, D.C.:
Association of Official Analytical Chemists.
Applegate, T. J., D. M. Webel, and X. G. Lei. 2003. Efficacy of a phytase
derived from Escherichia coli and expressed in yeast on phosphorus
utilization and bone mineralization in turkey poults. Poult. Sci.
82:1726-1732.
Argenzio, R. A., J. E. Lowe, H. F. Hintz, andH. F. Schiyver. 1974. Calcium
and phosphorus homeostasis in horses. J. Nutr. 104:18-27.
Augspurger, N. R., D. M. Webel, X. G. Lei, and D. H. Baker. 2003. Effi-
cacy of E. coli phytases expressed in yeast for releasing phytate-bound
phosphorus in young chicks and pigs. J. Anim. Sci. 81:47^83.
Bai'ton, B. A., N. A. Jorgensen, andH. F. DeLuca. 1987. Impact of prepar-
tum dietary phosphorus intake on calcium homeostasis at parturition. J.
Dairy Sci. 70:1186-1191.
Bartter, F. C. 1964. Disturbances of phosphorus metabolism. Pp. 315-339
in Mineral Metabolism, vol. 2, part A, C. L. Comar and F. Bronner, eds.
New York: Academic Press.
Berner, Y. N. 1997. Phosphorus. Pp. 63-92 in Handbook of Nutritionally
Essential Mineral Elements, B. L. O'Dell and R. A. Sunde, eds. New
York: Marcel Dekker.
Boling, S. D., D. M. Webel, 1. Mavromichalis. C. M. Parsons, and D. H.
Baker. 2000. The effects of citric acid on phytate-phosphorus utilization
in young chicks and pigs. J. Anim. Sci. 79:682-689.
Borucki Castro, S. 1., L. E. Phillip, V. Girard, and A. Tremblay. 2004.
Altering dietary cation-anion differences in lactating dairy cows to
reduce phosphorus excretion to the environment. J. Dairy Sci.
87:1751-1757.
Braithwaite, G. D. 1986. Phosphorus requirements of ewes in pregnancy
and lactation. J. Agric. Sci., Cambridge. 106:271-278.
Bravo, D., D. Sauvant, C. Bogaert, and F. Meschy. 2003. 111. Quantitative
aspects of phosphorus excretion in ruminants. Reprod. Nutr. Dev.
43:285-300.
Brown, W. R., L. Krook, and W. G. Pond. 1966. Atrophic rhinitis in swine.
Etiology, pathogenesis, and prophylaxis. Cornell Vet. 56 (Suppl. 1):3-
108. Budde, R. A., and T. D. Crenshaw. 2003. Ctu'onic metabolic acid
load induced by changes in dietary electrolyte balance increased chlo-
ride retention but did not compromise bone in growing swine. J. Anim.
Sci. 81:197-208.
Bushman, D. H., R. J. Emerick, and L. B. Embry. 1965. Incidence of uri-
nary calculi in sheep as affected by various dietary phosphates. J. Anim.
Sci. 24:671-675.
Carstairs, J. A., R. R. Neitzel, and R. S. Emery. 1981. Energy and phospho-
rus status as factors affecting postpartum performance and health of
dairy cows. J. Dairy Sci. 64:34-41.
Carter, S. D., G. L. Cromwell, T. R. Combs, G. Colombo, and P. Fanti.
1996. The determination of serum concentrations of osteocalcin in grow-
ing pigs and its relationship to end-measures of bone mineralization. J.
Anim. Sci. 74:2719-2729.
Cerosaletti, P. E., D. G. Fox, and L. E. Chase. 2004. Phosphorus reduction
through precision feeding of dairy cattle. J. Dairy Sci. 97:2314—2323.
Challa, J., and G. D. Braithwaite. 1989. Phosphorus and calcium metabo-
lism in growing calves with special emphasis on phosphorus homeosta-
sis. 4. Studies on milk-fed calves given different amounts of dietary
phosphorus but a constant intake of calcium. J. Agric. Sci., Cambridge
113:285-289.
Challa, J., G. D. Braithwaite. and M. S. Dhanoa. 1989. Phosphorus homeo-
stasis in growing calves. J. Agric. Sci., Cambridge. 112:217-226.
Charles. O. W., and L. Jensen. 1975. Effect of phosphorus levels on laying
hen performance. Poult. Sci. 54:1744 (Abstr).
Coffey, R. D., K. W. Mooney, G. L. Cromwell, and D. K. Aaron. 1994.
Biological availability of phosphorus in defluorinated phosphates with
different phosphorus solubilities in neutral ammonium citrate for chicks
and pigs. J. Anim. Sci. 72:2653-2660.
Combs, N. R., E. T. Kornegay, M. D. Lindemann, D. R. Notter, and F. H.
Welker. 1991a. Evaluation of a bone biopsy technique for determining
the calcium and phosphorus status of swine from weaning to market
weight. J. Anim. Sci. 69:664-672.
Combs, N. R., E. T. Kornegay. M. D. Lindemann, andD. R. Notter. 1991b.
Calcium and phosphorus requirements of swine from weaning to mar-
ket weight: I. Development of response curves for performance. J. Anim.
Sci. 69:673-681.
Combs, N. R., E. T. Kornegay, M. D. Lindemann, D. R. Notter, J. H. Wil-
son, and J. P. Mason. 1991c. Calcium and phosphorus requirements of
swine from weaning to market weight: II. Development of response
curves for bone criteria and comparison of bending and shear bone test-
ing. J. Anim. Sci. 69:682-693.
Crenshaw, T. D. 1986. Reliability of dietary Ca and P levels and bone min-
eral content as predictors of bone mechanical properties at various time
periods in growing swine. J. Nutr. 116:2155-2170.
Cromwell, G. L. 1992. The biological availability of phosphorus in
feedstuffs for pigs. Pig News Info. 13:75.
Cromwell, G. L., T. S. Stahly, R. D. Coffey, H. J. Monegue, and J. H.
Randolph. 1993. Efficacy of phytase in improving the bioavailability of
phosphorus in soybean meal and corn-soybean meal diets for pigs. J.
Anim. Sci. 71:1831-1840.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
PHOSPHORUS
297
Cromwell, G. L., S. L. Traylor, M. D. Lindemann, T. E. Stauber, and
D. W. Rice. 2000. Bioavailability of phosphorus in low-oligosaccharide,
low-phytate soybean meal for pigs. J. Anim. Sci. 78 (Suppl. 2):71
(Abstr.).
Cymbaluk, N. F., and G. I. Christison. 1989. Effects of dietary energy and
phosphorus content on blood chemistry and development of growing
horses. J. Anim. Sci. 67:951-958.
Danisi, G., and R. W. Straub. 1980. Unidirectional influx of phosphate
across the mucosal membrane of rabbit small intestine. Pflugers Ai'ch.
385:117-122.
DeBoer, G., J. G. Buchanan-Smith, G. K. MacLeod, and J. S. Walton. 1981.
Responses of dairy cows fed alfalfa silage supplemented with phospho-
rus, copper, zinc, and manganese. J. Dairy Sci. 64:2370-2377.
Dou, Z., K. F. Knowlton, R. A. Kohn, Z. Wu, L. D. Satter, G. Zhang, J. D.
Toth, and J. D. Ferguson. 2002. Phosphorus characteristics of dairy fe-
ces affected by diets. J. Environ. Qual. 31:2058-2065.
Dou, Z., J. D. Ferguson, J. Fiorini, J. D. Toth, S. M. Alexander, L. E. Chase,
C. M. Ryan, K. F. Knowlton, R. A. Kohn, A. B. Peterson, J. T. Sims,
and Z. Wu. 2003. Phosphorus feeding levels and critical control points
on dairy farms. J. Dairy Sci. 86:3787-3795.
Draper, H. H., T. L. Sie, and J. G. Bergan. 1972. Osteoporosis in aging rats
induced by high-phosphorus diets. J. Nutr. 102:1133—1142.
Edwards H. M., Jr., and J. R. Veltmann, Jr. 1983. The role of calcium and
phosphorus in the etiology of tibial dyschondroplasia in young chicks.
J. Nutr. 113:1568-1575.
Emerick, R. J., and L. B. Embry. 1963. Calcium and phosphorus levels
related to the development of phosphate urinary calculi in sheep. J.
Anim. Sci. 22:510.
Emerick, R. J., and L. B. Embry. 1964. Effects of calcium and phosphorus
levels and diethylstilbestrol on urinary calculi incidence and feedlot
performance of lambs. J. Anim. Sci. 23:1079.
Erickson, G. E., T. J. Klopfenstein, C. T. Milton, D. Brink, M. W. Orth, and
K. M. Whittet. 2002. Phosphorus requirement of finishing feedlot
calves. J. Anim. Sci. 80:1690-1695.
Fazekas, 1. G. 1954. Enlargement of parathyroid glands by simple acidic
compounds. Virchows Archiv. 324:531-542.
Field, A. C, J. A. Woolhams, R. A. Dingwall, and C. S. Munro. 1984.
Animal and dietary variation in the absorption and metabolism of phos-
phorus by sheep. J. Agric. Sci., Cambridge 10:283-291.
Forsberg, C. W., J. P. Phillips, S. P. Golovan, M. Z. Fan, R. G. Meidinger,
A. Ajakaiye, D. Hilborn, and R. R. Hacker. 2003. The Enviropig physi-
ology, performance, and contribution to nutrient management advances
in a regulated environment: the leading edge of change in the pork in-
dustry. J. Anim. Sci. 81(E. Suppl. 2):E68-E77.
Fredeen, A. H., E. J. DePeters, and R. L. Baldwin. 1988. Characterization
of acid-base disturbances and effects on calcium and phosphorus bal-
ances of dietary fixed ions in pregnant or lactating does. J. Anim. Sci.
66:159-173.
Garcia-Bojalil, C. M., C. B. Ammerman, P. R. Henry, R. C. Littell, and W.
G. Blue. 1988. Effects of dietary phosphorus, soil ingestion, and dietary
intake level on performance, phosphorus utilization, and serum and ali-
mentary tract mineral concentrations in lambs. J. Anim. Sci. 66:1508—
1519.
Gentile, J. M., K. R. Roneker, S. E. Crowe, W. G. Pond, and X. G. Lei.
2003. Effectiveness of an experimental consensus phytase in improving
dietary phytate-phosphorus utilization by weanling pigs. J. Anim. Sci.
81:2751-2757.
Gomori, G. 1942. A modification of the colorimetric phosphorus determi-
nation for use with the photoelectric colorimeter. J. Lab. Clin. Med.
27:955-960.
Guyton. A. D., J. M. McKinney, and K. F. Knowlton. 2003. The effect of
steam-flaked or dry ground corn and supplemental phytic acid on phos-
phorus partitioning and ruminal phytase activity in lactating cows. J.
Dairy Sci. 86:3972-3982.
Hahn, F. 1961. Toxicology of the polyphosphates. Z. Ernaehrungswiss.
1:55-64.
Hall, D. D., G. L. Cromwell, and T. S. Stahley. 1991. Effects of dietary
calcium, phosphorus, calcium: phosphorus ratio and vitamin K on per-
formance, bone strength, and blood clotting status of pigs. J. Anim. Sci.
69:646-655.
Han, Y. N., F. Yang, A. G. Zhou, E. R. Miller, P. K. Ku, M. G. Hogberg,
and X. G. Lei. 1997. Supplemental phytases of microbial and cereal
sources improve dietary phytate phosphorus utilization by pigs from
weaning through finishing. J. Anim. Sci. 75:1017—1025.
Harms, R. H., B. L. Damron, and P. W. Waldroup. 1965. Influence of high
phosphorus levels in caged layer diets. Poult. Sci. 44:1249-1253.
Hodge, H. C. 1964. Summaries of toxicological data: toxicity studies on
phosphates. Food Cosmet. Toxicol. 2:147-154.
Hogan, A. G., W. O. Regan, and W. B . House. 1950. Calcium phosphate
deposits in guinea pigs and the phosphorus content of the diet. J. Nutr.
41:203-212.
House, W. B., and A. G. Hogan. 1955. Injury to guinea pigs that follows a
high intake of phosphates. J. Nutr. 55:507-517.
Hutcheson, J. P., L. W. Greene, G. E. Carstens, and F. M. Byers. 1992.
Effects of zeranol and two dietary levels of calcium and phosphorus on
performance, carcass and bone characteristics, and calcium status in
growing lambs. J. Anim. Sci. 70:1346—1351.
Joyce, J. R., K. R. Pierce, W. M. Romane, and J. M. Baker. 1971. Clinical
study of nutritional secondary hyperparathyroidism in horses. J. Am.
Vet. Med. Assoc. 158:2033.
Kabakoff, B., N. C. Kendrick, and H. F. DeLuca. 1982. 1,25-
Dihydroxyvitamin D3 stimulated active uptake of phosphate by rat je-
junum. Am. J. Physiol. 243:E470-E475.
Keshavarz, K. 1994. Laying hens respond differently to high dietary levels
of phosphorus in monobasic and dibasic calcium phosphate. Poult. Sci.
73:687-703.
Knowlton, K. F., and J. H. Herbein. 2002. Phosphorus partitioning during
early lactation in dairy cows fed diets varying in phosphonis content. J.
Dairy Sci. 85:1227-1236.
Knowlton, K. F., J. H. Herbein, M. A. Meister-Weisbarth, and W.A. Wark.
2001. Nitrogen and phosphorus partitioning in lactating Holstein cows
fed different sources of dietary protein and phosphorus. J. Dairy Sci.
84:1210-1217.
Koelsch, R. 2005. Evaluating livestock system environmental performance
with whole-farm nutrient balance. J. Environ. Qual. 34:149—155.
Kornegay, E. T. 1996. Nutritional, environmental, and economic consider-
ations for using phytase in pig and poultry diets. Pp. 277-302 in Nutri-
ent Management of Food Animals to Enhance and Protect the Environ-
ment, E. T. Kornegay, ed. Boca Raton, FL: CRC Press.
Kowarski, S., and D. Schachter. 1969. Effects of vitamin D on phosphate
transport and incorporation into mucosal constituents of rat intestinal
mucosa. J. Biol. Chem. 244:211-217.
Krishnarao, G. V. G., and H. H. Draper. 1972. Influence of dietary phos-
phate on bone resorption in senescent mice. J. Nutr. 102: 1 143-1 145.
Krook, L., L. Lutwak, P. Hendrikson, F. Kallfelz, C. Hirsch, B. Romanus,
L. F. Belanger, J. R. Marier, and B. E. Sheffy. 1971. Reversibility of
nutritional osteoporosis: physicochemical data on bones from an ex-
perimental study in dogs. J. Nutr. 101:233-246.
Laflamme, G. H., and J. Jowsey. 1972. Bone and soft tissue changes with
oral phosphate supplements. J. Clin. Invest. 51:2834—2840.
Lall, S. P. 2002. The minerals. Pp. 259-307 in Fish Nutrition. 3rd ed. J. E.
Halver and R. W. Hardy, eds. San Diego, CA: Elsevier Science.
Lang, F., R. Greger, and F. G. Knox. 1981. Editorial review: factors modu-
lating the renal handling of phosphate. Renal Physiol. 4:1-16.
Lau, K., S. Chen, andB.Eby. 1984. Evidence for the role of P04 deficiency
in antihypertensive action of a high-Ca diet. Am. J. Physiol. 246:H324—
H331.
Lei, X. G., and C. H. Stahl. 2001. Biotechnological development of effec-
tive phytases for mineral nutrition and environmental protection. Appl.
Microbiol. Biotechnol. 57:474-481.
Lei, X. G., and J. M. Porres. 2003. Phytase enzymology, application, and
biotechnology. Biotechnol. Lett. 25:1787-1794.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
298
MINERAL TOLERANCE OF ANIMALS
Lei, X. G., P. K. Ku, E. R. Miller, and M. T. Yokoyama. 1993a. Supplemen-
tal microbial phytase improves bioavailability of dietary zinc to wean-
ling pigs. J. Nutr. 123:1117-1123.
Lei, X. G., P. K. Ku, E. R. Miller, and M. T. Yokoyama. 1993b. Supple-
menting corn-soybean meal diets with microbial phytase linearly im-
proves phytate phosphorus utilization by weanling pigs. J. Anim. Sci.
71:3359-3367.
Lei, X. G., P. K. Ku, E. R. Miller, M. T. Yokoyama, and D. E. Ullrey. 1994.
Calcium level affects the efficacy of supplemental microbial phytase in
corn-soybean meal diets for pigs. J. Anim. Sci. 72:139-143.
Little, D. A., and D. J. Minson. 1977. Variation in the phosphorus content
of bone samples obtained from the last three ribs of cattle. Res. Vet. Sci.
23:393-394.
Littledike, E. T., and J. P. Goff. 1987. Interactions of calcium, phosphonis,
magnesium, and vitamin D that influence their status in domestic meat
animals. J. Anim. Sci. 65:1727-1743.
Liu, J., D. W. Bollinger, D. R. Ledoux, and T. L. Veum. 2000. Effects of
dietary calcium :phosphorus ratios on apparent absorption of calcium
and phosphorus in the small intestine, cecum, and colon of pigs. J. Anim.
Sci. 78:106-109.
Lopez, H., F. D. Kanitz, V. R. Moreira, L. D. Satter, and M. C. Wiltbank.
2004a. Reproductive performance of dairy cows fed two concentrations
of phosphorus. J. Dairy Sci. 87:146-157.
Lopez, H., F. D. Kanitz, V. R. Moreira, M. C. Wiltbank, and L. D. Satter.
2004b. Effect of dietary phosphorus on performance of lactating dairy
cows: milk production and cow health. J. Dairy Sci. 87:139-146.
Martz, F. A., A. T. Belo, M. F. Weiss, R. I. Belyell, and J. P. Goff 1990.
True absorption of calcium and phosphorus from alfalfa and corn silage
when fed to lactating cows. J. Dairy Sci. 73:1288-1295.
Matsuzaki, H., M. Uehara, K. Suzuki, Q. L. Liu, S. Sato, Y. Kanke, and S.
Goto. 1997. High-phosphorus diet rapidly induces nephrocalcinosis and
proximal tubular injury in rats. J. Nutr. Sci. Vitaminol. (Tokyo)
43:627-641.
Matsuzaki, H., T. Kikuchi, Y. Kajita, R. Masuyama, M. Uehara, S. Goto,
and K. Suzuki. 1999. Comparison of various phosphate salts as the di-
etary phosphorus source on nephrocalcinosis and kidney function in
rats. J. Nutr. Sci. Vitaminol. (Tokyo) 45:595-608.
Matsuzaki, H., R. Masuyama, M. Uehara, K. Nakamura, and K. Suzuki.
2001. Greater effect of dietary potassium tripolyphosphate than of po-
tassium dihydrogenphosphate on the nephi'ocalcinosis and proximal tu-
bular function in female rats from the intake of a high-phosphorus diet.
Biosci. Biotechnol. Biochem. 65:928-934.
Matsuzaki, H., S. Katsumata, R. Masuyama, M. Uehara, K. Nakamura, and
K. Suzuki. 2002. Sex differences in kidney mineral concentrations and
urinary albumin excretion in rats given high-phosphorus feed. Biosci.
Biotechnol. Biochem. 66:1737-1739.
McDowell, L. R. 2003. Minerals in Animal and Human Nutrition, 2nd ed.
Amsterdam: Elsevier.
McLean, R. W., R. E. Hendricksen, D. B. Coates, and W. H. Winter. 1990.
Phosphorus and beef production in northern Australia. 6. Dietary at-
tributes and their relation to cattle growth. Trop. Grassl. 24:197-208.
McMeniman, N. P. 1973. The toxic effect of some phosphate supplements
fed to sheep. Aust. Vet. J. 49:150-152.
Minson, D. J. 1990. Phosphorus. Pp. 230-264 in Forage in Ruminant Nutri-
tion. New York: Academic Press.
Montgomery, J. L., J. R. Blanton, Jr., R. L. Horst, M. L. Galyean, K. J.
Morrow, Jr., D. B. Wester, and M. F. Miller. 2004. Effects of biological
type of beef steers on vitamin D, calcium, and phosphorus status. J.
Anim. Sci. 82:2043-2049.
Nelson, T. S., T. R. Shieh, R. J. Wodzinski, and J. H. Ware. 1971. Effect of
supplemental phytase on the utilisation of phytate phosphorus by chicks.
J. Nutr. 101:1289-1293.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
NRC. 1989. Nutrient Requirements of Horses. Washington. D.C.: National
Academy Press.
NRC. 2001. Nutrient Requirements of Dairy Cattle. Washington, D.C.:
National Academy Press.
Pallauf, J., and G. Rimbach. 1997. Nutritional significance of phytic acid
and phytase. Arch. Anim. Nutr. 50:301-319.
Peterlik, M., and R. H. Wasserman. 1978. Effect of vitamin D on
transepithelial phosphate transport in chick intestine. Am. J. Physiol.
234:E379-388.
Pointillart, A. 1991. Enhancement of phosphorus utihzation in growing pigs
fed phytate-rich diets by using rye bran. J. Anim. Sci. 69:1 109-1 1 15.
Pones, J. M., C. H. Stahl, W. H. Cheng, Y. X. Fu, K. R. Roneker, W. G.
Pond, and X. G. Lei. 1 999. Dietary intrinsic phytate protects colon from
lipid peroxidation in pigs with moderately high iron intake. Proc. Soc.
Exp. BioL Med. 221:80-86.
Price, J. S., B. Jackson, R. Eastell, A. E. Goodship, A. Blumsohn, I. Wright,
S. Stoneham, L. E. Lanyon, and R. G. G. Russell. 1995. Age-related
changes in biochemical markers of bone metabolism in horses. Equine
Vet. J. 27:210-217.
Randall, D. J., and E. C. Robinson. 1990. Acute toxicologic evaluation of vari-
ous concentrations of phosphoric acid. J. Am. Coll. Toxicol. B :69— 70.
Rapp, C, H. J. Lantzsch, and W. Drochner. 200 1 . Hydrolysis of phytic acid
by intrinsic plant and supplemented microbial phytase {Aspergillus
niger) in the stomach and small intestine of minipigs fitted with re-
entrant cannulas 3. Hydrolysis of phytic acid (IPj) and occurrence of
hydrolysis products (IPj, IP^, IP3, and IP,). J. Anim. Physiol. Anim.
Nutr. 85:420-^30.
Reddy, N. R., S. K. Sathe, and D. K. Salunkhe. 1982. Phytates in legumes
and cereals. Adv. Food Res. 28:1-92.
Reinhardt, T. A., andH. R. Conrad. 1980. Modeof action of pharmacologi-
cal doses of cholecalciferol during parturient hypocalcemia in dairy
cows. J. Nutr. 110:1589-1596.
Reinhart, G. A., and D. C. Mahan. 1986. Effect of various calcium:
phosphorus ratios at low and high dietaiy phosphonis for starter, grower,
and finishing swine. J. Anim. Sci. 63:457^66.
Roy, P. K., and S. P. Lall. 2003. Dietary phosphorus requirement of juvenile
haddock (Melanogrammus aeglefmus L.). Aquaculture 221:451^68.
Sands, J. S., D. Ragland, C. Baxter, B. C. Joern, T. E. Sauber, andO. Adeola.
2001. Phosphorus bioavailability, growth performance, and nutrient
balance in pigs fed high available phosphorus corn and phytase. J. Anim.
Sci. 79:2134-2142.
Schneider, P., R. MuUer-Peddinghaus, G. Papritz, G. Trieb, G. Trautwein,
and H. Uebergerg. 1980a. Die Kaliumhydrogenphosphat-induzierte
nephropathie des hundes: II. Glomerulare Veranderungen. Vet. Pathol.
17:720-737.
Schneider, P., G. Papritz, R. Muller-Peddinghaus, M. Bauer, H. Lehmann,
H. Uebergerg, and G. Trautwein. 1980b. Die Kaliumhydrogenphosphat-
induzierte nephropathie des hundes: I. Pathogenese der tubulusatrophie.
Vet. Pathol. 17:699-719.
Schonewille, J. T., A. T. Van'T Klooster, and A. C. Beynen. 1994. High
phosphorus intake depresses apparent absorption of magnesium in preg-
nant heifers. J. Anim. Physiol. Anim. Nutr. 71:15-21.
Schryver, H. F., H. F. Hintz, and P. H. Craig. 1971. Calcium metabolism in
ponies fed a high phosphorus diet. J. Nutr. 101:259-264.
Schryver, H. F., H. F. Hintz, P. H. Craig, D. E. Hogue, and J. E. Lowe.
1972. Site of phosphorus absorption from the intestine of the horse. J.
Nutr. 102:143-148.
Scott, D., A. A. J. Rajaratne, and W. Buchan. 1995. Factors affecting faecal
endogenous phosphorus loss in the sheep. J. Agric. Sci., Cambridge.
124:145-151.
Simons, P. C. M., H. A. J. Versteegh, A. W. Jongbloed, P. A. Kemme, P.
Slump, K. D. Bos, M. G. E. Walters, R. F. Beudeker, and G. J.
Verschoar. 1990. Improvement of phosphorus availability by microbial
phytase in broilers and pigs. Br. J. Nutr. 64:525-540.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
PHOSPHORUS
299
Scares, J. H., Jr. 1995. Phosphorus bioavailability. Pp. 257-294 in
Bioavailability of Nutrients for Animals: Amino Acids, Minerals, and
Vitamins, C. B. Ammerman, D. H. Baker, and A. J. Lewis, eds. New
York: Academic Press.
Spencer, J. D., G. L. AUee, and T. E. Sauber. 2000. Phosphorus
bioavailability and digestibility of normal and genetically modified lo w-
phytate corn for pigs. J. Anim. Sci. 78:675-681.
Stahl, C. H., Y. M. Han, K. R. Roneker, W. A. House, and X. G. Lei. 1999.
Phytase improves iron bioavailability for hemoglobin synthesis in young
pigs. J. Anim. Sci. 77:2135-2142.
Suttle, N. F., and L. Hay. 1986. Urolithiasis. Pp. 250-254 in Diseases of
Sheep, 2nd ed., W. B. Martin, and 1. D. Aitken, eds. Oxford: Blackwell
Scientific Publications.
Ternouth, J. H. 1990. Phosphorus and beef production in Northern Austra-
lia. 3. Phosphorus in cattle — a review. Trop. Grassl. 24:159—169.
Underwood, E. J., and N. F. Suttle, 1999. The Mineral Nutrition of Live-
stock, 3rd ed. New York: CABl Publishing.
USGS (U.S. Geological Survey). 2003. Online. Available at http://
minerals.usgs.gov/minerals/pubs/commodity/phosphate_rock/. Ac-
cessed on December 22, 2003.
Valk, H., L. B. J. Sebek, and A. C. Beynen. 2002. Influence of phosphorus
intake on excretion and blood plasma and saliva concentrations of phos-
phorus in dairy cows. J. Dairy Sci. 85:2642-2649.
Vielma, J., and S. P. Lall. 1998. Control of phosphorus homeostasis of
Atlantic salmon {Salmo salar) in fresh water. Fish Physiol. Biochem.
19:83-93.
Vitti, D. M. S. S., E. Kebreab, J. B. Lopes, A. L. Abdalla, F. F. R. De
Carvalho, K. T. De Resende, L. A. Crompton, and J. France. 2000. A
kinetic model of phosphorus metabolism in growing goats. J. Anim.
Sci. 78:2706-2712.
Weiner, M. L., W. F. Salminen, P. R. Larson, R. A. Barter, J. L. Kranetz,
andG. S. Simon. 2001. Review: toxicological review of inorganic phos-
phates. Food Chem. Toxicol. 39:759-786.
Weiss, W. P., and D. J. Wyatt. 2004. Macromineral digestion by lactating
daily cows: estimating phosphorus excretion via manure. J. Dairy Sci.
87:2158-2166.
Williams, S. N., L. A. Lawrence, L. R. McDowell, N. S. Wilkinson, P. W.
Ferguson, and A. C. Warnick. 1991a. Criteria to evaluate bone
mineralisation in cattle. 1. Effect of dietary phosphorus on chemical,
physical, and mechanical properties. J. Anim. Sci. 69:1232-1242.
Williams, S. N., L. R. McDowell, L. A. Lawrence, N. S. Wilkinson, P. W.
Ferguson, and A. C. Warnick. 1991b. Criteria to evaluate bone
mineralisation in cattle. 11. Noninvasive techniques. J. Anim. Sci.
69:1243-1254.
Williams, S. N., L. R. McDowell, A. C. Warnick, N. S. Wilkinson, and L.
A. Lawrence. 1991c. Phosphorus concentrations in blood, milk, feces,
bone, and selected fluids and tissues of growing heifer as affected by
dietary phosphorus. Livest. Res. Rural Dev. 3:67-78.
Wu, Z., L. D. Satter, and R. Soja. 2000. Milk production, reproductive
performance, and fecal excretion of phosphorus by diary cows fed three
amounts of phosphorus. J. Dairy Sci. 83:1028-1041.
Wu, Z., L. D. Satter, A. J. Blohowiak, R. H. Stauffacher, and J. H. Wilson.
200 1 . Milk production, estimated phosphorus excretion, and bone char-
acteristics of dairy cows fed different amounts of phosphorus for two or
three years. J. Dairy Sci. 84:1738-1748.
Wu, Z., S. K. Tallam, V. A. Ishler, and D. D. Archibald. 2003. Utilization of
phosphorus in lactating cows fed varying amounts of phosphorus and
forage. J. Dairy Sci. 86:3300-3308.
Zacharias, B. H., H. J. Lantzsch, and W. Drochner. 1999. Influence of mi-
crobial phytase and dietary calcium on the accumulation of lead in dif-
ferent organs of pigs. Biol. Trace Elem. Res. 70:243—249.
Copyright © National Academy of Sciences. All rights reserved.
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24
Potassium
INTRODUCTION
Potassium (K) was first discovered in 1807 by Sir
Humplirey Davy, wtio isolated it from potash (Peterson,
1997). Potassium ranks seventh in the order of abundance of
elements in the Earth's crust with a concentration of 26,000
mg/kg by weight (McDowell, 2003). It is the third most
abundant element found in the body of most animals. Potas-
sium is a silvery, white metal in its pure state. Its atomic
number is 19, and it is a member of the alkali group of met-
als, which also include lithium, sodium, rubidium, cesium,
and francium. Potassium exists in three natural occurring
isotopes with the mass numbers 39, 40, and 41 with the rela-
tive abundances of 93.1, 0.012, and 6.9 percent, respectively
(Aikawa, 1983). The atomic weight of potassium is 39.098
and its specific gravity is 0.86. It melts at 63°C and boils at
around 760°C.
Potassium is a very strong reducing metal and therefore is
not found in its pure form in nature, but readily combines
with other elements to form salts (McDowell, 2003). Potas-
sium has a valence of H-1 and joins to other elements or
groups of elements through ionic bonds. The potassium com-
pounds that have been used as supplements in diets to test
the effects of potassium include potassium chloride (KCl),
potassium bicarbonate (KHCO3), potassium carbonate
(KjCOj), potassium acetate (CH3CO2K), potassium citrate
monohydrate (KjCgHjO^-HjO), potassium sulfate (K2SO4),
tripotassium phosphate (K3PO4), potassium iodide (KI), and
potassium gluconate (CgH(j07K).
ESSENTIALITY
Potassium was determined to be an essential element in
the diet of several animals in the early 19th century
(McDowell, 2003). Nonruminant animals generally have a
lower requirement for potassium than ruminants. The potas-
sium requirement of various species has been published in
several National Research Council (NRC) publications. The
dietary potassium requirement of chickens ranges from 1,500
mg/kg for leghorn layers to 3,000 mg/kg for broilers from 0-
8 weeks of age (NRC, 1994). The dietary potassium require-
ment of turkeys ranges from 7,000 mg/kg at 0-4 weeks to
4,000 mg/kg at 20-24 weeks (NRC, 1994b). The potassium
requirement of swine is between 1 ,500 mg/kg to 3,000 mg/kg
with younger animals requiring a higher dietary concentra-
tion than older animals (NRC, 1998). The dietary potassium
requirement of sheep is 5,000-8,000 mg/kg of dry matter
(NRC, 1985). Beef feedlot cattle have an estimated potas-
sium requirement of 6,000 mg/kg of diet dry matter while
the requirement for gestating beef cows is between 5,000
mg/kg and 7,000 mg/kg (NRC, 2000). Lactating dairy cows
have the highest dietary potassium requirement at about
10,000 mg/kg of diet dry matter (NRC, 2001). Potassium is
the mineral found in the highest concentration in milk (1,500
mg/L) and, therefore, lactating cattle require a higher potas-
sium intake than nonlactating cattle (NRC, 200 1). Weil et al.
(1988) calculated the dietary potassium requirement for the
growing dairy calf to be between 3,400 and 5,800 mg/kg of
diet dry matter.
Research reviewed by McDowell (2003) showed that
stress of animals tended to increase the requirement for po-
tassium. Research in Florida found dairy cows subjected to
heat stress improved feed intake and milk production as the
amount of potassium in the diet was increased from 6,600
mg/kg to 10,800 mg/kg of diet dry matter (NRC, 2001). The
NRC (200 1) recommended a dietary concentration of 15,000
mg/kg dry matter for lactating dairy cows under thermal
stress. Smith and Teeter (1987) found broilers subjected to
35°C temperatures required dietary potassium of 15,000 to
20,000 mg/kg. Hutcheson et al. (1984) calculated that the
amount of potassium required for transported calves was 247
mg/kg of body weight for the first two weeks after transport,
approximately 20 percent more than what was recommended
for calves that had not been transported. Juvenile tilapia re-
quire 2,000 to 3,000 mg/kg potassium in their diet (Shiau
and Hsieh, 2001). Hills et al. (1982) found the dietary potas-
306
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POTASSIUM
307
slum requirement for kittens increased from 3,000 to 5,000
mg/kg wfien protein content of the diet increased from 33 to
68 percent.
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Tfie current mettiods used for analysis of potassium wittiin
body fluids include flame ptiotometry, ion-selective elec-
trodes, and atomic absorption spectrophotometry (Peterson,
1997). Electron probe microanalysis is used to determine
potassium concentration within individual cells. Neutron
activation analysis is used to measure the concentration of
potassium within platelets (Glick, 1983). Erroneous results
in the concentration of potassium within specimens normally
result from improper preparation of the specimen for analy-
sis rather than intrinsic effects within the analysis. A variety
of blood-handling processes can result in invalid potassium
results. Potassium concentration fluctuates diurnally; there-
fore, choice of sampling time should be considered. Cold
temperature, mixing extent, and vigor can cause movement
of potassium from within cells into the extracellular fluids,
increasing potassium results. Other factors that can affect
potassium results include choice of serum or plasma, length
of storage time, skin-puncture and blood sampling technique,
and metabolic state (Glick, 1983). Very high blood ammo-
nia levels can sometimes interfere with potassium analysis if
methods besides flame photometry are used (Glick, 1983).
Total body potassium content can be estimated by using the
natural isotopes by whole body counting or examining the
distribution of administered radioactive isotope (for ex-
ample, "^^K) (Peterson, 1997). However, total body potas-
sium measurements are usually of little value, and it is the
extracellular potassium concentration that is important in
determining the potassium status of animals. Measurement
of potassium status through blood, serum, or plasma analy-
sis in animals is not a totally reliable indicator because of the
discussion above and its regulation in the body.
REGULATION AND METABOLISM
Absorption and Metabolism
Most potassium is absorbed from the upper portion of the
small intestine of nonruminant and ruminant animals through
simple diffusion (McDowell, 2003). Potassium absorption
also takes place in the rumen and omasum in ruminants. A
small amount of potassium is absorbed in the lower part of
the small intestine and in the large intestine in both
nonruminants and ruminants. The true digestibility of potas-
sium is 95 percent or greater in most feedstuffs (McDowell,
1992). A significant amount of the potassium absorbed in
ruminants is from the saliva excretions, which are high in
potassium, and in some cases potassium is used in saliva to
replace sodium (McDowell, 1992). Disturbances of the in-
testinal tract, such as diarrhea, can reduce the absorption of
potassium.
The role of potassium within the body includes acid-base
regulation, osmotic pressure maintenance, nerve impulse
transmission, muscle contraction, and carbon dioxide and
oxygen transport (NRG, 2001). It is also involved in phos-
phorylation of creatine, pyruvate kinase activity, cellular
uptake of amino acids and synthesis of protein, carbohydrate
metabolism, and maintenance of normal cardiac and renal
tissue, and as an activator or cofactor in many enzymatic
reactions. Ninety-eight percent of the potassium within the
body is located within the cells, with 2 percent of it located
in the extracellular fluid. Potassium accounts for 75 percent
of the total cations within body cells and sodium accounts
for approximately 90 percent of the total cations in the extra-
cellular fluid (McDowell, 1992).
The main excretory route for potassium is urine. The hor-
mone aldosterone is indirectly responsible for the regulation
of potassium through its effect on sodium reabsorption in the
kidney. Fecal loss of potassium in dairy cattle is estimated at
2,200 mg of K/kg of dietary dry matter intake (NRG, 2001).
Under heat stress conditions, ruminants and horses can lose
significant amounts of potassium through sweat.
IVIetabolic Interactions
Potassium interacts with sodium and chlorine within the
body to maintain acid-base balance and electrical and chemi-
cal concentration gradients (Kem and Trachewsky, 1983).
The concentration of potassium within the cell is normally in
the range of 100-160 mM (3,900-6,200 mg/L) while the
concentration outside the cell is 3.5-5 mM (137-195 mg/L).
In contrast, the sodium concentration inside the cell is 3-30
mM (69 to 690 mg/L) while concentration outside the cell is
130-145 mM (3,000 to 3,300 mg/L). The contrasting con-
centrations of potassium in cells and sodium outside cells
create a chemical concentration gradient in which potassium
would rapidly diffuse into the extracellular fluid while so-
dium would rapidly diffuse into the intracellular fluid if al-
lowed to cross the cell membrane. These chemical gradients
are maintained by energy generated within the cells (Kem
and Trachewsky, 1983) through the use of a number of cel-
lular pumps, including the primary transporters Na-K-AT-
Pase and H-K-ATPase and the secondary transporters
electroneutral lNa:2CI: IK cotransporter and potassium con-
ductivity channels (Peterson, 1997).
The distribution of potassium within the body is regu-
lated by a number of compounds including insulin, cat-
echolamines, and aldosterone (Peterson, 1997). Insulin is
released into the blood stream if potassium rises by as little
as a few tenths of an mMol. Insulin then stimulates the up-
take of potassium in the liver and skeletal muscles by in-
creasing Na-K-ATPase pump activity. There is a rise in ex-
tracellular concentration of potassium with exercise.
Exercise causes the release of catecholamines from the adre-
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MINERAL TOLERANCE OF ANIMALS
nal gland, which then trigger the rise of potassium in plasma
through stimulation of the Na-K-ATPase pump that drives
potassium back into cells. Cellular uptake of potassium is
also accelerated by hyperpolarization. Aldosterone is neces-
sary for normal rates of potassium excretion. Aldosterone
influences potassium excretion by activating sodium chan-
nels that allow the entrance of sodium from the lumen of the
nephron and the excretion of potassium (Peterson, 1997).
The excretion of potassium always rises as the presence of
the hormone aldosterone increases. The concentration of al-
dosterone increases when animals are under stress, therefore
possibly explaining the increase in potassium requirements
of animals raised and housed within stressful conditions.
SOURCES AND BIOAVAILABILITY
Environmental Exposure
The potassium level in forages ranges from slightly less
than 10,000 mg/kg to more than 50,000 mg/kg of plant dry
matter. Potassium is normally higher in forages than grains
and plant protein feeds. The potassium level in forages can
be quite variable and dependent on the species and variety,
maturity, fertilization with potassium and nitrogen sources,
crop management procedures, and environmental and soil
conditions. Cool season grasses contain higher concentra-
tions of potassium than warm season grasses; temperate le-
gumes contain higher levels of potassium than tropical le-
gumes (Underwood and Suttle, 1999). Mature pastures,
winter pastures containing weathered forage, and hay that
has been rained on can have levels of potassium below that
required by ruminants (NRC, 2001; McDowell, 2003). The
level of potassium in grains, plant protein feeds, and by-
products feeds is generally less than the requirements of lac-
tating dairy cows (NRC, 2001); however, it is generally
adequate for meeting the potassium requirement of
nonruminant animals that require less potassium in the diet
than ruminants. The potassium concentration in grains
ranges from 3,000 to 8,000 mg/kg, in vegetable proteins from
10,000 to 25,000 mg/kg, and in animal products from 3,000
to 20,000 mg/kg (McDowell, 2003). BioavailabiUty of po-
tassium from most forages and grains is 85 percent or higher
(Miller, 1995; NRC, 2001).
Supplementation Considerations
Potassium is readily provided in most feedstuffs and
therefore its deficiency has not been recognized as a possible
nutrition problem until recently. The amount of potassium in
most diets for lactating dairy cows is normally greater than
15,000 mg/kg; therefore, no additional supplementation of
potassium is needed (NRC, 2001). Supplementation of po-
tassium can become necessary to meet nutritional require-
ments of lactating dairy cows and other ruminants as the
percentage of energy concentrates and by-products increases
in diets, especially as the recent trend in the industry is to-
ward the increased feeding of concentrates and by-product
feeds such as brewer's grains, distiller's dried grains, corn
gluten meal, and cottonseed hulls (McDowell, 2003).
Nonruminants generally do not require potassium supple-
mentation, especially in high protein diets, as protein sources
generally contain the highest concentration of potassium for
feedstuffs classified as concentrates. The inorganic sources
of supplemental potassium that are readily available for ab-
sorption in the gastrointestinal tract include KCl, KHCO3,
K^COj, K2SO4, C^HjKOj, and KjCgHjO^HjO (NRC,
20"01)."
TOXICOSIS
Potassium toxicosis in healthy animals is rare. This is due
to the body's ability to readily excrete potassium as well as
regulate absorption. The major causes of hyperkalemia (a
rise in the level of potassium to greater than 195 mg/L in the
extracellular fluids) are excessive potassium intake (rarely
the primary cause of hyperkalemia), reduced renal losses,
and redistribution of potassium (Peterson, 1997). Renal
losses of potassium can be reduced by acute renal failure,
mineral corticoid deficiency, or potassium sparing diuretics.
Hemolysis, necrosis, muscle injury, catecholamine antago-
nists, insulin deficiency, and abnormal skeletal muscle chan-
nels can lead to the redistribution of potassium causing hy-
perkalemia (Peterson, 1997). Hyperkalemia and hypo-
kalemia are both associated with potentially fatal
arrhythmias (Peterson, 1997). The responses of animals ad-
ministered different levels of potassium are summarized in
Table 24-1.
Low Levels
In a study involving 4-week-old Holstein and Jersey
calves gaining 0.73 kg/day fed diets ranging in potassium
from 5,500 to 13,200 mg/kg, Weil et al. (1988) found no
toxic effects across the dietary range in potassium. In a sec-
ond study, Weil et al. (1988) fed 6-week-old Holstein calves
diets containing 3,400 or 5,800 mg/kg of the dry matter as
potassium. Calves fed the 5,800 mg/kg potassium diet gained
faster (0.74 kg/day versus 0.60 kg/day) and had a higher
feed intake than calves fed the lower potassium diet.
Hutcheson et al. (1984) conducted several studies on the
effects of potassium, added as KCl, in diets on calves for two
weeks following shipping to feedlots. Concentrations of po-
tassium in the diets tested ranged from 9,000 to 31,000 mg/
kg. They concluded calf performance improved and blood
packed cell volume increased as the potassium in the diet
increased from 7,000 to 22,000 mg/kg. Mortality rate of the
calves also decreased when potassium was included in the
ration at the levels of 13,000 and 22,000 mg/kg. The level of
sodium in the serum increased as the level of potassium in
the diet increased (Hutcheson et al., 1984).
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POTASSIUM
309
A set of experiments conducted by Teeter and Smith ( 1 986)
found no adverse effects wiien potassium, as KCl, was sup-
plied in water witii a corn-soybean base diet containing 7,300
mg/lcg wiien fed to week-old ciiicken pullets for two weeks
under near optimal environmental conditions. Potassium sup-
plied in the water at levels from 500 to 1,500 mg/L had no
effect on body weight gain or feed efficiency. Under heat stress
conditions (35°C, 70 percent relative humidity), offering the
same water and dietary concentrations of potassium resulted
in improved average daily gain in broilers receiving water
containing 1,000 and 1,500 mg/L potassium, but blood pH
and feed efficiency were not improved (Teeter and Smith,
1986). Another experiment found that weight gain was im-
proved by providing 2,400 to 3,600 mg/kg potassium in water
(Smith and Teeter, 1987). Supplementation of drinking water
with KCl to heat-stressed broilers at levels up to 1 ,500 mg/kg
KCl improved average daily gain to 27.4 g/day while supple-
mentation with KjCOj reduced average daily gain to 18.6
g/day, which was significantly below the average of 23.1
g/day without any potassium supplementation (Teeter and
Smith, 1986). Water consumption was also reduced with the
addition of K-iCOj under environmentally stressful conditions
(Teeter and Smith, 1986).
A set of experiments conducted by Smith et al. (2000)
tested the excreta moisture response in laying hens to the
excess of several dietary minerals including potassium. The
increase in the dietary concentration of potassium from 2,300
to 20,000 mg/kg caused a linear increase in water intake,
water to feed ratio, and excreta moisture (1 1.95 ± 2.02 g/kg
for each 1 g/kg increase in diet potassium content). The feed
intake decreased linearly as the potassium concentration in
the diet increased.
Two carcinogenesis studies in rats (Lina et al., 1994; Lina
and Kuijpers, 2004) found base-forming potassium com-
pounds such as KHCO3 are strong promoters of urinary blad-
der carcinogenesis, while neutral potassium salts such as KCl
are weak promoters. Lina et al. (1994) conducted an experi-
ment in which rats were fed a control diet, or the control diet
plus 7,800 or 15,600 mg/kg potassium as KHCO3, or the
control diet plus 15,600 mg/kg potassium as KCl. These di-
ets were fed from 4 to 130 weeks to male and female rats.
Both diets containing KCl and KHCO3 increased urinary
volume and potassium levels, while only KHCO3 caused an
increase in urinary pH. Potassium bicarbonate supplementa-
tion resulted in hyperplasia, papollomas, and transitional cell
carcinomas of the urinary bladder compared to only a few
neoplastic lesions in KCl fed rats. Potassium bicarbonate
induces metabolic alkalosis as shown by an increase in the
base excess in blood, urinary pH, and urinary net base excre-
tion, whereas KCl had no effect on the metabolic acid-base
balance (Lina and Kuijpers, 2004). High levels of both KCl
and KHCO3 increased levels of potassium in the serum and
caused a decrease in growth rate. The chronic stimulation of
the adrenal cortex by K+ in the diets containing KCl and
KHCO3 caused hypertrophy of the adrenal zona
glomerulosa. From week 13 of supplementation onward,
KHCO3 caused the onset of oncocytic tubules while there
was only a slight effect in those rats supplemented with KCl
at 18 months. Lina and Kuijpers (2004) concluded that in the
case of potassium supplementation, the different responses
observed between KCl and KHCO3 supplementation repre-
sented the physiological adaptation of the metabolic pro-
cesses to base-forming salts.
High Levels
Studies using differing types and amounts of potassium
have found that the palatability of various diets generally
decreased as the percentage of potassium in the diet in-
creased. Neathery et al. (1980) tested the palatability of four
different sources of potassium with Holstein bull calves in
16 cafeteria-style feeding experiments. The feedstuffs con-
tained potassium from different sources (KCl, K,C03,
KHCO3, and C2H3KO2) in the amounts of 20,000, 40,000, or
60,000 mg/kg. The most palatable potassium sources were
KHCO3 and C2H3KO2, followed by KCl and with K2CO3
being the least palatable. When calves were fed only one
source of potassium (KCl) at 20,000 mg/kg of the diet, there
was no adverse effect on voluntary feed intake or growth.
However, at 60,000 mg/kg of the diet, a decrease in volun-
tary feed intake and weight gain was observed.
A dietary concentration of 29,000 mg/kg potassium as
supplied by K3C5H50yH20 caused reduced feed intake and
weight gain when fed to rats for 17 days (Everts et al., 1996).
Both a low level of potassium (1,000 mg/kg) and high level
(29,000 mg/kg) of potassium in the diet from K3CgH507-H20
caused increased water intake and urinary excretion.
In a study with meadow voles, Mickelson and Christian
(1991) found that as potassium concentration in the diet in-
creased above 5,000 mg/kg, meadow voles selectively chose
against consumption of a higher potassium diet. Potassium
from a variety of sources was included in high potassium
diets (390,000 mg/kg KCl, 360,000 mg/kg K.SO^, 80,000
mg/kg of K2CO3, K3C5H5O7, K3PO4, and 10,000 mg/kg KI)
for feeding to voles. As concentration of potassium in the
diet approached 35,000 mg/kg, voles chose to eat with in-
creasing selectivity. There was no significant health or meta-
bolic effects related to consumption of the high potassium
diet except for a significant increase in water consumption.
Goff and Horst (1997) demonstrated that the feeding of
potassium or sodium above dietary requirements in diets fed
to dairy cows before parturition increased the incidence of
milk fever in them. Jersey dairy cows entering their fourth or
greater lactation were fed diets supplemented with KHCO3
to achieve dietary potassium concentrations of 11,000,
21,000, or 3I,000mg/kg. Incidence of milk fever increased
as potassium in the diet increased; 2 of 20 cows, 10 of 20
cows, and 11 of 23 cows exhibited milk fever with diets
containing 11,000, 21,000, or 31,000 mg/kg potassium, re-
spectively. Lina et al. (2004) found that KHCO3 is a strong
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MINERAL TOLERANCE OF ANIMALS
base-forming salt and that it has the effect of increasing urine
and blood pH. This effect, plus a reduction in plasma hy-
dro xyproline levels, was also found by Goff andHorst (1997)
for diets containing KHCO3 and NaHCOj Two different lev-
els of calcium were also tested. It was concluded that dietary
calcium concentration was not a major risk factor in the cause
of milk fever, but the concentration of cations, especially
potassium, could induce alkalosis in prepartum milk cows
that reduces the dairy cow's ability to maintain calcium ho-
meostasis (Goff and Horst, 1997). High potassium appears
to induce milk fever or hypocalcaemia by reducing the sen-
sitivity of bone and renal tissue to parathyroid hormone. In
the kidney, the reduced sensitivity results in a decreased con-
version of vitamin D3 to 1,25-dihydroxyvitamin D3, which
is responsible for increasing absorption of calcium from the
gut and increased mobilization of calcium from bone.
In ruminants, high potassium diets generally inhibit the
absorption of magnesium from the gastrointestinal tract, par-
ticularly the rumen (Goff and Horst, 1997). Fisher et al.
(1994) added K2CO3 to a base diet containing 16,000 mg/kg
potassium to raise potassium levels to 31,000 and 46,000
mg/kg for feeding to dairy cows. The diet containing 46,000
mg/kg potassium caused a reduction in milk yield. As potas-
sium level in the diet increased, plasma potassium levels in-
creased and plasma magnesium levels decreased, indicating
high levels of potassium interfere with the absorption of
magnesium. The high dietary concentration of potassium
also interfered with the utilization of calcium by reducing
levels in urine and milk. Water intake and urine output in-
creased as the level of potassium in the diet increased (Fisher
et al., 1994). Ram et al. (1998) postulated that magnesium
absorption from the rumen is regulated by transport mecha-
nisms both sensitive and insensitive to potassium. They con-
cluded from feeding diets to wethers of 10,000 and 36,000
mg/kg potassium containing KHCO3 and 1,300, 2,500, and
3,700 mg/kg magnesium from magnesium oxide that 36,000
potassium in the diet increased the concentration of potassium
in the rumen and reduced magnesium absorption by 0.32 g/
day. Increasing magnesium in the diet at either high or low
dietary potassium concentrations could offset the reduction
in magnesium absorption (Ram et al., 1998). Leonhard-
Marek and Martens (1996) used sheep rumen epithelium in
vitro to show a decrease in mucosal-to-serosal magnesium
flux (indicating decreased magnesium absorption) when lu-
minal potassium concentrations were increased up to 80 mM.
The effect of mucosal potassium on magnesium absorption
was concentration-dependent with the depressing effect of
potassium concentration showing a logarithmic behavior.
From 5 to 80 mM mucosal potassium concentration, magne-
sium absorption decreased by a factor of almost 3; however,
above 80 mM potassium concentration, no further decrease
in magnesium absorption was observed. This research indi-
cates the development of hypomagnesemia in ruminants
feeding on lush, high-potassium pasture forages results from
the potassium depolarizing rumen membranes and reducing
the magnesium uptake into rumen epithelial cells. Jittakhot
et al. (2004) fed diets containing 20,700, 48,000 or 75,500
mg of potassium per kg DM with either 40,600 or 69,100 mg
of magnesium/day to 6 ruminally fistulated dry cows. Di-
etary potassium concentrations were achieved by feeding
KHCO3 and MgO was used as the magnesium source. At the
highest magnesium supplementation level, magnesium ab-
sorption was significantly decreased as potassium levels in-
creased (12,800, 8,900, and 4,800 mg/day). At the low mag-
nesium supplementation, magnesium absorption was similar
at 20,700 and 48,000 potassium levels (5,300 mg/day); how-
ever, it decreased to 800 mg/day at the 75,500 potassium
level. It was concluded there was a negative linear correla-
tion between rumen potassium level and absorption of mag-
nesium as measured by urinary excretion.
Schonewille et al. (1999a) fed three grass diets contain-
ing either 26,000 mg/kg potassium, 43,000 mg/kg potas-
sium, or 26,000 mg/kg plus KHCO3 to achieve a similar
potassium concentration to the 43,000 mg/kg diet to dry,
nonpregnant cows. Both of the 43,000 mg/kg diets equally
increased the concentration of potassium in the rumen be-
fore and after feeding and resulted in an apparent magne-
sium absorption from the rumen of about 2 percent com-
pared to 10.8 percent for the 26,000 mg/kg potassium diet.
Schonewille et al. (1999b) conducted a study testing the
effects of KHCO3, KCl, and K-citrate, supplemented to
provide 41,000 mg/kg potassium in the diet, on magnesium
absorption in wethers. Both KHCO3 and K-citrate signifi-
cantly reduced apparent magnesium absorption by 9.5 and
6.5 percent, respectively, while KCl tended to reduce ap-
parent magnesium absorption by 5.5 percent. The consump-
tion of KHCO3 and K-citrate produced a significant
transruminal potential difference while KCl did not. The
authors concluded that the type of anion in potassium salts
has an effect on magnesium absorption in addition to the
effect of potassium concentration.
Neathery et al. (1979) drenched 6-month-old Holstein
calves with 290 to 2,800 mg of potassium (using KCl) per
kilogram of body weight. They found that the sodium con-
tent of the plasma generally increased about 1 hour after
dosing. Respiration rates increased following dosing while
carbon dioxide pressure, pH, and bicarbonate in the blood
decreased. Clinical toxicosis signs, including excitability,
muscle tremors of the legs, and excessive salivation, were
observed with potassium doses greater than 580 mg K/kg
BW. Some of the calves in the groups that received 1,730,
2,310, and 2,880 mg K/kg BW died. This study concluded
that ruminants can safely consume large amounts of potas-
sium in feeds if consumption is spread over time; however,
when massive doses of potassium are given at one time, a
breakdown in the homeostasis of potassium occurs resulting
in death. Similar effects can be observed in horses with
hyperkalemic periodic paralysis disease, a hereditary genetic
defect, when high dietary potassium levels are fed, such as
with the feeding of alfalfa hay (Reynolds et al., 1998).
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POTASSIUM
311
Factors Influencing Toxicity
Potassium in and of itself is a relatively nontoxic element
that is required in relatively large amounts to sustain life.
However, disturbances in potassium metabolism can result
in it being toxic. Most commonly, the physiological disor-
ders that can lead to situations that have the potential to cause
potassium toxicosis include impaired renal potassium excre-
tion, acidosis, hypoaldosteronism, insulin deficiency, cellu-
lar injury, drugs, and genetics (Kaufman and Papper, 1983).
In certain quarter horse families, the genetically inherited
disease hyperkalemia periodic paralysis results in high lev-
els of potassium in the blood, causing muscles to contract
more readily than normal (Meyer et al., 1999). Feeding diets
with less than 10,000 mg/kg potassium helps minimize the
disease (Reynolds et al., 1998).
The form of potassium in diets can influence its toxicity.
Inclusion of K-citrate and KHCO3 in diets to raise potassium
levels to 40,000 mg/kg decreased magnesium absorption,
while the inclusion of KCl to achieve 40,000 mg/kg potas-
sium in the diet only increased the potassium concentration
in the rumen. These effects may be due to the basic salt prop-
erties of K-citrate and KHCO3 compared to KCl, which is a
neutral salt (Schonewille et al., 1999b). Raising magnesium
levels in the diet can offset the effects of potassium on mag-
nesium absorption. Teeter and Smith (1986) found that KCl
exacerbated the toxic effects of NH^Cl supplementation in
chickens. Research reviewed in the NRC (1980) showed that
animals can adapt to higher levels of potassium if the
amounts supplied are increased incrementally. Sodium salts
under some conditions can reduce the effects of high dietary
potassium (NRC, 1980).
TISSUE LEVELS
Potassium is the third most abundant mineral in the body
after calcium and phosphorus, representing approximately 0.3
percent of the body's dry matter (McDowell, 2003). Two-
thirds of it is located in the skin and muscle. Studies summa-
rized by the NRC (1980) showed that rats fed 50,000 mg/kg
potassium diets had elevated amounts of potassium in the skel-
etal and heart muscles, kidney, and thymus; however, tissue
levels of potassium were not significantly different than when
5,000 mg/kg potassium diets were fed (Meyer et al., 1950). A
study by Drescher et al. (1958) found that there were no dif-
ferences in the carcass or heart muscles for rats fed levels of
potassium ranging from 0.60 to 15 mg K/kg BW. Thus, tissue
levels of potassium are not very sensitive or indicative of di-
etary potassium levels.
MAXIMUM TOLERABLE LEVELS
The NRC (1980) set the maximum tolerable amount of
potassium at 30,000 mg/kg for all ruminant and
nonruminant species. A similar single maximum tolerable
dietary level of potassium for all species under all condi-
tions and fed all forms of potassium could not be estab-
lished based on the research reviewed. In rats and other
nonruminant animals, dietary concentrations above 10,000
mg/kg potassium can lead to some reduction in weight gain,
feed intake, and increased urinary excretion. However, ac-
tual toxicity of potassium is dependent on the health and/or
metabolic state of the animal and the potassium compound
fed. Research reviewed by the NRC (1998) suggests that
pigs can tolerate up to 10 times their requirement of potas-
sium. Potassium salts like KHCO3 that affect acid-base
balance within the body are less tolerated than neutral po-
tassium salts like KCl (Schonewille et al., 1999b). Dairy
cows have a wide tolerance and requirement for potassium
in diets. Cows close to parturition are at an increased risk
for milk fever (hypocalcaemia) as dietary concentrations
of potassium increase and cation balance of the diet be-
comes more positive (Goff and Horst, 1997). In contrast,
lactating dairy cows, and particularly those under heat
stress, have requirements for potassium above 15,000
mg/kg and can tolerate 30,000 mg/kg potassium diets.
However, magnesium supplementation needs to increase
in the diets of ruminants as dietary potassium levels in-
crease above 15,000 mg/kg to decrease the probability of
developing grass tetany (Schonewille et al., 1999a,b). Re-
search suggests that ruminants can tolerate higher than
30,000 mg/kg potassium levels in their diet. In the spring,
many grazing ruminants consume forages containing more
than 40,000 to 50,000 mg/kg potassium. Conservatively
safe maximum tolerable levels for nonruminants would be
10,000 mg/kg and for ruminants 20,000 mg/kg.
FUTURE RESEARCH NEEDS
The risk of potassium toxicity is low from current
feedstuff s and water sources; therefore, tolerance levels are
not well established and will need additional research if more
accurate defined tolerance levels in healthy animals are de-
sired. Future research is needed on the interaction of potas-
sium fed in large excess of an animal's requirement on the
metabolic and physiological functions of other minerals.
Excess potassium feeding to dairy cows at parturition has
been shown to result in hypocalemia but effects on other
minerals (such as sodium and magnesium) and the compli-
cations resulting need additional research.
SUMMARY
Potassium is an essential nutrient that is found mainly in
the cells of the animal body and is an important element in
metabolic functions. The dietary needs for each species of
animal vary, with ruminants generally requiring a higher
level of potassium provided in the diet than nonruminants.
Potassium is a fairly common element in most feedstuffs;
therefore, while it is a nutritionally important element, its
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MINERAL TOLERANCE OF ANIMALS
essentiality has not been researched until relatively recently.
Most diets provide adequate levels of this element and do
not contain toxic levels of potassium. Potassium can be toxic
if it is given in large enough doses, or if the body's potas-
sium homeostatic system is compromised. Factors that in-
fluence its toxicity include the metabolic state of the animal,
compound consumed, and interactions with other elements.
The toxic effects of potassium include cardiac arrest, grass
tetany through interference in magnesium absorption, and
milk fever, although other metabolic pathways can cause
both milk fever and grass tetany. The levels of potassium
within the tissues are only slightly affected by the concentra-
tion of potassium within the diet.
REFERENCES
Aittawa, J. K. 1983. Tlie role of potassium in biological evolution. Pp. 2—8
in Potassium: Its Biological Significance. R. Whang, ed. Boca Raton,
FL: CRC Press.
Dresclier, A. N., N. B. Talbot, P. A. Meara, M. Ten-y, and J. D. Crawford.
1958. A study of the effects of excessive potassium intake upon body
potassium stores. J. Clin. Inves. 37:1316.
Everts, H. B., H. K. Jang, R. C. Boston, and N. L. Canolty. 1996. A com-
partmental model predicts that dietary potassium affects lithium dy-
namics in rats. J. Nutr. 126:1445-1454.
Fisher, L. J., N. Dinn, R. M. Tait, and J. A. Shelford. 1994. Effect of Level
of Dietary Potassium on the Absorption and Excretion of Calcium and
Magnesium by Lactating Cows. Can. J. Anim. Sci. 74:503-509.
Click, M. R. 1983. Methodology for potassium analysis. Pp. 9-22 in Potas-
sium: Its Biologic Significance, R. Whang, ed. Boca Raton, FL: CRC
Press.
Goff, J. P., and R. L. Horst. 1997. Effects of the addition of potassium or
sodium, but not calcium, to prepartum rations on milk fever in dairy
cows. J. Dairy Sci. 80:176-186.
Hills, D. L., J. G. Morris, and Q. R. Rogers. 1982. Potassium requirement of
kittens as affected by dietary protein. J. Nutr. 112:216-222.
Hutcheson, D. P., N. A. Cole, and J. B. McLaren. 1984. Effects of pretransit
diets and post-transit potassium levels for feeder calves. J. Anim. Sci.
58:700-707.
Jittakhot, S., J. T. Schonewille, H. Wouterse, C. Yuangklang, and A. C.
Beynen. 2004. Apparent magnesium absorption in dry cows fed at
3 levels of potassium and 2 levels of magnesium intake. J. Dairy
Sci. 87:379-385.
Kaufman, C. E., and S. Papper. 1983. Hyperkalemia. Pp. 77-95 in Potassium:
Its Biologic Significance, R. Whang, ed. Boca Raton, FL: CRC Press.
Kem, D. C, andD. Trachewsky. 1983. Potassium metabolism. Pp. 25-35 in
Potassium: Its Biologic Significance, R. Whang, ed. Boca Raton, FL:
CRC Press.
Leonhard-Marek, S., and H. Martens. 1996. Effects of potassium on mag-
nesium transport across rumen epithelium. Am. J. Physiol. 34:G1034-
G1038.
Lina, B. A. R., V. M. H. Hollanders, and M. H. M. Kuijpers. 1994. The Role
of Alkalizing and Neutral Potassium-Salts in Urinary-Bladder Carcino-
genesis in Rats. Carcinogenesis 15:523-527.
Lina, B. A. R., and M. H. M. Kuijpers. 2004. Toxicity and carcinogenicity
of acidogenic or alkalogenic diets in rats; effects of feeding NH4CI,
KHC03 or KCI. Food Chem. Toxicol. 42:135-153.
McDowell, L. R. 1992. Potassium. In Minerals in Animal and Human Nu-
trition, L. R. McDowell, ed. San Diego, CA: Academic Press, Inc.
McDowell, L. R. 2003. Potassium. In Minerals in Animal and Human Nu-
trition, L. R. McDowell, ed. San Diego, CA: Academic Press, Inc.
Meyer, J. H., R. R. Gunert, and M. T. Zepplin. 1950. Effect of dietary levels
of sodium and potassium on growth and on concentrations in blood
plasma and tissues of white rat. Am. J. Physiol. 162:184.
Meyer, T. S., M. R. Fedde, J. H. Cox, and H. H. Erickson. 1999.
Hyperkalaemic periodic paralysis in horses: a review. Equine Vet. J.
31:362-367.
Mickelson, P. A., and D. P. Christian. 1991. Avoidance of high-potassium
diets by captive meadow voles. J. Mammal. 72:177-182.
Miller, E. 1995. Potassium bioavailability. Pp. 295-301 in Bioavailability
of Nutrients for Animals, C. B. Ammerman, D. H. Baker, and A. J.
Lewis, eds. San Diego, CA: Academic Press.
NRC (National Research Council). 1980. Potassium. Pp. 378-391 in Min-
eral Tolerance of Domestic Animals. Washington, D.C.: National Acad-
emy Press.
NRC. 1985. Nutrient requirements and signs of deficiency. Pp. 2-25 in
Nutrient Requirements of Sheep. Washington, D.C. : National Academy
Press.
NRC. 1994a. Nutrient requirements of chickens. Pp. 19-34 in Nutrient
Requirements of Poultry, 9th rev. ed. Washington, D.C: National Acad-
emy Press.
NRC. 1994b. Nutrient requirements of turkeys. Pp. 35-39 in Nutrient
Requirements of Poultry, 9th rev. ed. Washington, D.C: National Acad-
emy Press.
NRC. 1998. Minerals. Pp. 47-70 in Nutrient Requirements of Swine. Wash-
ington, D.C: National Academy Press.
NRC. 2000. Minerals. Pp. 54-74 in Nutrient Requirements of Beef Cattle.
Washington, D.C: National Academy Press.
NRC. 2001. Minerals. Pp. 105-161 in Nutrient Requirements of Dairy
Cattle. Washington, D.C: National Academy Press.
Neathery, M. W., D. G. Pugh, W. J. Miller, R. H. Whitlock, R. P. Gentry,
and J. C Allen. 1979. Potassium toxicity and acid-base balance from
large oral doses of potassium to young calves. J. Dairy Sci. 62:1758-
1765.
Neathery, M. W., D. G. Pugh, W. J. Miller, R. P. Gentry, and R. H. Whitlock.
1980. Effects of sources and amounts of potassium on feed palatability
and on potassium toxicity in dairy calves. J. Dairy Sci. 63:82-85.
Peterson, L. N. 1997. Potassium in nutrition. Pp. 153-183 in Handbook of
Nutritionally Essential Mineral Elements, B. L. O'Dell and R. A. Sunde,
eds. New York: Marcel Dekker.
Ram, L., J. T. Schonewille, H. Martens, A. T. Van't Klooster, and A. C
Beynen. 1998. Magnesium absorption by wethers fed potassium bicar-
bonate in combination with different dietary magnesium concentrations.
J. Dairy Sci. 81:2485-2492.
Reynolds, J. A., G. D. Potter, L. W. Greene, G. Wu, G. K. Carter, M. T.
Martin, T. V. Peterson, M. Murray-Gerzik, G. Moss, and R. S. Erkert.
1998. Genetic-diet interactions in the hyperkalemic periodic paralysis
syndrome in quarter horses fed varying amounts of potassium: I. Potas-
sium and sodium balance, packed cell volume and plasma potassium
and sodium concentrations. J. Equine Vet. Sci. 18:591-600.
Schonewille, J. T., A. T. Van't Klooster, H. Wouterse, and A. C Beynen.
1999a. Effects of intrinsic potassium in artificially dried grass and
supplemental potassium bicarbonate on apparent magnesium absorp-
tion in dry cows. J. Dairy Sci. 82:1824-1830.
Schonewille, J. T., A. C Beynen, A. T. Van't Klooster, H. Wouterse, and L.
Ram. 1999b. Dietary potassium bicarbonate and potassium citrate have
a greater inhibitory effect than does potassium chloride on magnesium
absorption in wethers. J. Nutr. 129:2043-2047.
Shiau, S., and J. Hsieh. 2001. Quantifying the dietary potassium require-
ment of juvenile hybrid tilapia. Br. J. of Nutr. 85:21 3—2 1 8.
Smith, A., S. P. Rose, R. G. Wells, and V. Pirgozlieu. 2000. Effect of excess
dietary sodium, potassium, calcium and phosphorus on excreta mois-
ture of laying hens. Br. Poult. Sci. 41 :598-607.
Copyright © National Academy of Sciences. All rights reserved.
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inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
POTASSIUM 313
Smith, M.O., and R.G. Teeter. 1987. Potassium balance of ttie 5 to 8-weeii- Underwood, E. J., and N. F. Suttle. 1999. Potassium. Pp. 213-229 in The
old broiler exposed to constant heat or cyclic high temperature stress Mineral Nutrition of Livestock. New York: CABl Publishing,
and the effects of supplemental potassium chloride on body weight gain Weil, A. B., W. B. Tucker, and R. W. Hemken. 1988. Potassium require-
andfeed efficiency. Pouh. Sci. 66:487^92. ment of dairy calves. J. Dairy Sci. 71:1868-1872.
Teeter, R. G., and M. O. Smith. 1986. High chronic ambient temperature
stress effects on broiler acid— base balance and their response to supple-
mental ammonium chloride, potassium chloride, and potassium carbon-
ate. Poult. Sci. 65:1777-1781.
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25
Selenium
INTRODUCTION
Selenium (Se) has an atomic number of 34 and an atomic
weighit of 78.96. As a semimetal (metalloid) element, sele-
nium has four natural oxidation states (-2, 0, +4, and +6)
(NRC, 1983; Barceloux, 1999). In the -2 state, selenium ex-
ists as metallic selenide (NajSe), hydrogen selenide (HjSe),
or dimethyl selenide. A strong reducing agent and a rela-
tively strong acid, hydrogen selenide is a very toxic gas at
room temperature, and decomposes to form elemental sele-
nium and water in air. Many naturally occurring minerals
contain selenides of heavy metals (EHC 58, 1986). Methy-
lated selenides are the primary detoxification compounds in
the body; dimethyl selenides emit a strong garlic odor and
can be detected in the breath of animals exposed to high
levels of selenium. The state of selenium is found in el-
emental selenium. At physiological pH, the primary form of
selenium exists as Se^^ in selenocysteine. The elemental se-
lenium (Se") has several allotropic forms including a red
powder, red crystals, a dark brown moss, and a silver gray
form. It boils at 684°C, and is very stable, highly insoluble,
and unavailable to plants. The +4 state of selenium occurs as
selenite in compounds such as sodium selenite (NajSeOj),
selenium dioxide (SeOj), and selenious acid (HjSeOj). This
state of selenium can be oxidized slowly to the H-6 state in
alkaline solution and in the presence of oxygen, or be readily
reduced to elemental selenium by reagents such as ascorbic
acid or sulfur dioxide. The weakly dibasic selenious acid can
be formed from the reaction of selenium dioxide with water,
and sometimes acts as an oxidizing instead of a reducing
agent. Compounds containing the -1-6 state of selenium in-
clude sodium selenate (Na,Se04), selenium trioxide (SeOj),
or selenic acid (H2Se04). From these compounds, selenium
is stable, soluble, and highly available to plants under alka-
line conditions. Thus, the H-6 state of selenium is potentially
the form of this element most toxic to the environment.
Selenium and sulfur belong to the same group (Via) in
the Periodic Table, thus these elements share similar atomic
sizes, bond energies, ionization potentials, and electron af-
finities (Tinggi, 2003). A large number of selenium ana-
logues of organic sulfur compounds such as
selenomethionine have been identified in plants, animals,
and microorganisms. However, there are at least two major
differences between selenium and sulfur (Tinggi, 2003).
First, selenium tends to be reduced in biological systems in
contrast to sulfur, which tends to be oxidized in those sys-
tems. Second, the acid strengths of selenium are greater than
those of sulfur (e.g., pKa of HjSe = 3.7; pKa of HjS = 6.9).
The strong acid strength of selenium enables the element, as
selenol compounds (R-SeH), to be easily dissociated at
physiological pH in catalytic reactions.
There are six stable isotopes of selenium (74, 76, 77, 78,
80, and 82) with natural abundances of 0.87, 9.02, 7.85,
23.52, 49.82, and 9.19 percent, respectively (EHC 58, 1986).
The natural isotopic pattern is useful in determining sele-
nium-containing fragments in mass spectrometry. Radioiso-
topes of selenium do not exist in nature, but can be produced
by neutron activation or by radionuclear decay. The com-
monly used tracer in experiments is ^^Se with a half-life of
120 days. There are also two short half-life radioactive sele-
nium isotopes (^^™Se and ^'Se with half-lives of 17.5 sec-
onds and 18.6 minutes, respectively).
The Earth's crust contains approximately 0.09 mg of Se/kg,
rendering the element the 69th in order of abundance
(McDowell, 2003). It is found mainly in cretaceous rocks,
volcanic materials, some seafloor deposits, and glacial drift
in central Canada and North Dakota in the form of metallic
selenides (NRC, 1980). In soil, selenium is present as basic
selenite [(Fe2gOH)Se03], calcium selenate (CaSe04),
elemental selenium, and organic compounds derived from
plants (NRC, 1983). Weathering of selenium-containing
rocks is the primary source of soil selenium, along with
that from volcanic activity, dust, phosphate fertilizers, and
water. The industrial applications of selenium are mainly
for manufacturing rectifiers, xerographic copy machines.
321
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MINERAL TOLERANCE OF ANIMALS
photoelectric cells, glass, ceramics, rubber, pigments, and
metal-plating solutions (NRC, 1980).
ESSENTIALITY
Although the biological significance of selenium was ini-
tially recognized with its toxicity to livestock, selenium de-
ficiency is a more widespread practical problem. The nutri-
tional essentiality of selenium was first established by its
role in preventing diseases such as liver necrosis in rats, exu-
dative diathesis in chicks, hepatosis dietetica in swine, white
muscle disease in ruminants, and reproduction failure in vari-
ous species (NRC, 1983). There are many clinical and sub-
clinical signs of selenium deficiency in animals (McDowell,
2003). However, most of these clinical signs are not pro-
duced by selenium deficiency alone, but rather in combina-
tion with vitamin E deficiency (Oldfield, 2003). In some ar-
eas of China, selenium deficiency is associated with an
endemic cardiomyopathy called Keshan disease in children
and women of child-bearing age (Chen et al., 1980). Accel-
erated mutations of myocarditic coxsackievirus B3 from
avirulent forms to the virulent forms in selenium deficiency
might contribute to the occurrence of this disease (Beck et
al., 1995). An osteoarthropathy in humans called Kashin-
Beck disease (reported in China) is also considered a sele-
nium-responsive disease (Ge and Yang, 1993).
Since the milestone discovery of selenium as an integral
part of cellular glutathione peroxidase (Rotruck et al., 1973),
significant progress has been made in understanding the
molecular and biochemical functions of selenium. In mam-
mals, selenium is an essential component of at least 12 en-
zymes: four glutathione peroxidases that use glutathione to
break down hydroperoxides; three iodothyronine 5'-
deiodinases that catalyze the deiodination of L-thyroxine to
the biologically active thyroid hormone 3,3'5-triiodothyro-
nine; three thioredoxin reductases that reduce oxidized pro-
teins; a selenophosphate synthetase 2 that is involved in se-
lenium activation of selenocysteine synthesis; and a
methionine-R-sulfoxide reductase (selenoprotein R) (Brown
and Arthur, 2001; Gladyshev et al., 2004). There are three
characterized selenium-containing proteins: selenoprotein P
that accounts for 60 percent of selenium in plasma,
selenoprotein W that may be related to white muscle dis-
ease, and a 15 kDa selenoprotein that may be related to can-
cer (Brown and Arthur, 2001). In all these selenium-contain-
ing enzymes or proteins, selenium exists as the
selenocysteine moiety that is encoded by UGA, normally a
stop codon, and incorporated into the peptide by a mecha-
nism called "co-translation," a process that involves four
gene products, three reactants, and a unique mRNA sequence
named selenocysteine insertion element (SECIS) in the 3'
untranslated region (Sunde, 1997). Without this sequence,
the translation of selenium-containing proteins truncates at
the UGA codon. Using this unique sequence and other sig-
nature characteristics of the known selenoproteins, another
1 1 new selenoproteins have been identified from the human
genome. These are glutathione peroxidase 6 and
selenoproteins H, I, K, M, N, O, R, S, T, and V (Gladyshev
et al., 2004). Because cysteine replaces selenocysteine in the
mouse and rat glutathione peroxidase 6, the rodent
selenoproteome consists of 24 instead of the 25
selenoproteins suggested in humans. Overexpression or
knockout of selected selenoprotein genes in mice has been
applied to elucidate the metabolic functions of specific
selenoproteins. This approach has led to exciting discoveries
of new roles of glutathione peroxidase 1 (Cheng et al., 1998;
Fu et al., 2001; McClung et al., 2004); glutathione peroxi-
dase 2 (Esworthy et al., 2003; Chu et al., 2004); and
selenoprotein P (Burk et al., 2003; Hill et al., 2003). The
selenium requirements of various species including fish fall
between 0.1 and 0.38 mg/kg of diet (NRC, 1993). Although
the RDA for adult humans is 55-70 |Jg/day, supranutritional
levels of selenium supplementation, in the form of selenium-
enriched yeast, have been reported to reduce mortality due
to lung, colon, and prostate cancers (Clark et al., 1996).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Although several methods can be used for selenium de-
termination, the volatility and instability of certain forms of
selenium and the non-homogeneity of sample materials are
the common challenges for all analytical procedures (NRC,
1983). Thus, adequate precaution is required for sample col-
lection, preparation, and storage to avoid loss of or contami-
nation with selenium. Fluorometry is the most commonly
used, and perhaps the most sensitive (detection limit to 2 |ig
Se/L) method for assay of total selenium in feeds, feces,
water, urine, and tissues (Olson et al., 1975). Samples are
wet-digested in mixtures of nitric, sulfuric, and perchloric
acids, with or without additives such as hydrogen peroxide
to destroy organic matter and free the selenium. A pre-diges-
tion or concentration procedure may be added to remove
excessive fat or to reduce the sample size. After the released
selenious acids react with 2,3-diaminonaphthalene to form
fluorescent piazselenol, it is extracted from an acid solution
(pH 1-2) with either decahydronapthalene or cyclohexane
and detected at an emission wavelength of 520 nm and an
excitation wavelength of 390 or 366 nm. Although the fluo-
rometric method has become an official assay for detecting
selenium, it has certain limitations, and precautions must be
taken when using this method (EHC 58, 1986). First, all
traces of nitric acid in the digestion sample should be re-
moved by heating it in a perchloric acid fume hood until
perchloric acid fumes appear (about 15-20 min). Caution
should be taken to avoid explosions. Secondly, the
trimethylselenonium moiety in urine, some plants, and kid-
ney samples may be resistant to wet digestion, requiring ex-
tended digestion time. Thirdly, animal samples should be
digested in fresh forms to avoid losses of volatile selenium
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SELENIUM
323
compounds. Finally, the sensitivity of the fluorometric analy-
sis may be improved by re-distilling cyclohexane and re-
extracting 2,3-diaminonapthalene in 0.1 M hydrochloric
acid.
Atomic absorption spectrometry can also be used for se-
lenium analysis (NRC, 1983). If samples contain relatively
high levels of selenium, flame atomization is useful, but at-
omization of selenium as hydrogen selenide is more sensi-
tive and specific (EHC 58, 1986). It is possible to perform a
direct analysis of selenium in certain samples without diges-
tion by using an improved atomic absorption method based
on Zeeman effect background (Cheng et al., 1999). Neutron
activation analysis of selenium is very accurate, sensitive,
and specific (EHC 58, 1986; Sunde, 1997). Thermal neutron
activation is the most commonly used procedure for irradiat-
ing samples, producing ^^Se, ^'Se, and ^^™Se. Based on cer-
tain values, constants, or the irradiation and counting of sele-
nium standards, the selenium content of the assayed sample
can be determined by the detected radioactivity (van der Lin-
den et al., 1974). In neutron activation analysis, sample de-
struction is not essential, but is preferred for the chemical
separation of selenium. The limitation of neutron activation
analysis of selenium is the unavailability of adequate equip-
ment and the time required for the analysis. During recent
years, speciation of selenium compounds in plant or animal
samples using HPLC-ICP-MS (inductively coupled plasma-
mass spectrometry) or HPLC-ESI (electronspray ionization)-
MS has become a new focal point of selenium biology with
limited success (Zayed et al., 1998; Kotrebai et al., 2000;
Polatajko et al., 2004).
REGULATION AND METABOLISM
Absorption and Metabolism
For both ruminants and nonruminants, various forms of
selenium are readily absorbed (up to 98 percent) in the small
intestines, particularly the distal part for selenate (White et
al., 1989; Vendeland et al., 1992). Selenocysteine and
selenomethionine are absorbed via an active amino acid
transport mechanism (Xia et al., 2000), whereas selenite is
absorbed by simple diffusion, and selenate by a sodium-me-
diated carrier shared with sulfate (Wolffram et al., 1986,
1988; Barceloux, 1999). No homeostatic control of selenium
absorption has been identified or presumably exists as di-
etary selenium levels or body selenium status has no appar-
ent impact on its absorption efficiency (Vendeland et al.,
1992; Windisch and Kirchgessner, 2000a, b). However, se-
lenium absorption does vary, depending on its chemical
form, the animal species, and a number of dietary factors.
Organic selenium, such as selenomethionine or selenium-
enriched wheat and yeast, has a greater absorption rate than
inorganic selenium in many species (Heinz et al., 1996; Kim
and Mahan, 2001a,b). Selenate is better absorbed than selen-
ite (Vendeland et al., 1992), and both are better absorbed
than elemental selenium (Barceloux, 1999). Due to the
reduction of selenite and selentate, and the formation of
insoluble particles in the rumen, cattle and sheep have lower
absorption of selenium with greater variations than non-
ruminant species (Wright and Bell, 1966). High levels of
dietary sulfur, lead, alfalfa hay, and cyanogenetic glycosides,
along with high or low levels of dietary calcium, reduce
selenium absorption in ruminants (Neathery et al., 1990;
Ivancic and Weiss, 2001; Spears, 2003).
The absorbed selenium becomes associated with proteins
in the plasma and carried to tissues. More than 95 percent of
^^Se disappeared from the blood after 6 hours following ad-
ministration to calves (Neathery et al., 1990). In selenium
adequacy, selenoprotein P represents >60 percent of plasma
selenium in rats (Read et al., 1990). Increasing dietary sele-
nium from 0.62 to 11.9 mg/kg resulted in a decrease of the
portion of plasma selenium as selenoprotein P from 40-48
percent to 24-32 percent, resulting in more plasma selenium
bound to plasma glutathione peroxidase and albumin (Hintze
et al., 2002). Knockout of selenoprotein P interrupts the
transport of selenium from liver to peripheral tissues such as
testis (Hill et al., 2003). This implies that selenoprotein P is
involved in the transport of selenium to tissues. A significant
amount of selenium is associated with albumin in animals or
humans with excessive selenium intake, especially the natu-
rally occurring organic forms of selenium (Xia et al., 2000).
In rhesus monkeys receiving 0.5 mg Se/L in drinking water,
68 percent of erythrocyte selenium was associated with
erythrocyte glutathione peroxidase when sodium selenite
was given, in comparison with 34 percent for
selenomethionine (Butler et al., 1990). In selenium-adequate
animals, kidney and liver have the highest selenium content,
followed by spleen and pancreas (Kim and Mahan, 2001a,b;
Lawler et al., 2004; Cristaldi et al., 2005). Muscle has mod-
erate levels of selenium content, but accounts for the largest
pool of body selenium because of its mass (Hintze et al.,
2002). When organic selenium is fed to sheep and cattle at
the same dietary level as inorganic selenium, it results in
higher selenium concentrations in muscle, liver, kidney, and
plasma in both species (Ullrey et al., 1977). Seleno-
methionine or selenium-enriched yeast is also more efficient
in raising blood, milk, and tissue selenium in both humans
and animals (Thompson et al., 1982; Knowles et al., 1999;
Mahan et al., 1999; Mahan, 2000). The placenta or mam-
mary gland transfer of selenium in cattle is quite effective
(van Saun et al., 1989; Abdelrahman and Kincaid, 1995;
Enjalbert et al., 1999), with a higher efficiency for the or-
ganic forms than the inorganic forms (Langlands et al., 1990;
Zachara et al., 1993; Ortman and Pehrson, 1999). Approxi-
mately 6 to 20 percent of ingested dietary selenium goes into
milk in lactating Holstein cows (Ivancic and Weiss, 2001).
Animals can excrete selenium via feces and exhalation,
but urine is the primary excretion route and plays a quantita-
tively greater role in selenium homeostasis (Ellis et al., 1997;
Windisch and Kirchgessner, 2000b; Ivancic and Weiss,
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MINERAL TOLERANCE OF ANIMALS
2001). Fecal selenium excretion is also an important route in
animals fed high levels of dietary selenium (Ellis et al.,
1997). Trimethylselenonium accounted for 2 percent of uri-
nary selenium in rats fed 0.25 mg Se/kg (as selenite), but
rose to 35-40 percent in rats supplemented with a high level
of selenium in water (4 mg Se/L) (Janghorbani et al., 1990).
The route, amount, and time course of selenium excretion
are affected by the levels of selenium intake, the form of
selenium, body selenium status, and dietary levels of cop-
per, lead, mercury, and arsenic (NRC, 1983).
Metabolic Interactions, Regulations, and Mechanism of
Toxicities
Metabolic pathways of various fonns of selenium in the body
are not fully understood, but it is clear that all fonns of selenium
are incorporated into selenium-dependent enzymes or proteins
in a "co-translation" fashion. Using serine as the carbon source,
selenite or selenate can be converted into selenocysteine (Sunde,
1997). The process requires the reduction of selenite to elemen-
tal selenium first and then to selenide (Ganther and Hsieh,
1974). Besides serving as a substrate of selenophosphate syn-
thetase for the synthesis of selenocysteine, selenide can bind to
selenium-binding proteins or be methylated sequentially into
different end metabolites such as methaneselenol,
dimethylselenide or trimethylselenonium (Hsieh and Ganther,
1977). Selenomethionine is readily metabolized into [Se]-
adenosyl methionine (Markham et al., 1980) and subsequently
into selenocysteine that may be degraded, catalyzed by a spe-
cific lyase, to release elemental selenium (Esaki et al., 1982).
Because selenomethionine can be incorporated into proteins in
place of methionine, expression of selenoenzymes and tissue
selenium distribution in animals fed selenomethionine are af-
fected by dietary levels of methionine (Waschuleswski and
Sunde, 1988). Metabolism of methylselenocysteine or
selenocystine resembles that of selenite instead of
selenomethionine (Martin and Hurlbut, 1976; Deagen et al.,
1987).
Expression of selenoenzyme mRNA and activity is
largely regulated by dietary selenium level or body selenium
status (Lei et al., 1997a, 1997b, 1998; Mahan, 2000; Kaur et
al., 2003). Efforts have been made to model the flux of sele-
nium among tissues (Patterson and Zech, 1992). Metabolic
interactions of selenium with other nutrients or factors occur
at different levels. As mentioned above, body selenium bal-
ance seems to be regulated primarily by excretion. Dietary
sulfate and several heavy metals significantly increase sele-
nium excretion and reduce selenium absorption or retention
(Jensen, 1975; Donaldson and McGowan, 1989; Ivancic and
Weiss, 2001; Hamilton, 2004). The strong antagonism be-
tween selenium and heavy metals such as mercury also oc-
curs during the selenium passage across the placenta or mam-
mary gland (Parizek et al., 1980).
At the metabolic functional level, selenium is closely as-
sociated with vitamins E and C, polyunsaturated fatty acids.
iron, sulfur-containing amino acids, and iodine. It is very
difficult, if not impossible, to produce clinical signs without
a combined deprivation of both selenium and vitamin E
(Underwood and Suttle, 1999). The general belief is that
these two antioxidant nutrients scavenge free radicals at dif-
ferent sites and spare each other. However, the molecular
mechanism of such interaction is unclear. High levels of di-
etary vitamin E (up to 100-fold the requirement) could not
replace the role of selenium-dependent glutathione peroxi-
dase in protecting mice against acute oxidative stress induced
by pro-oxidants (Cheng et al., 1999). High levels of dietary
polyunsaturated fatty acids or iron aggravate dietary sele-
nium deficiency, whereas high levels of dietary methionine
or vitamin C ameliorate selenium deficiency (NRC, 1983).
As a component of three iodothyronine 5'-deiodinases, sele-
nium cannot play its role in maintaining normal thyroid hor-
mone without adequate iodine in the diet (Brown and Arthur,
2001).
Despite many decades of research, mechanisms of sele-
nium toxicity still remain unclear. Three possibilities have
been postulated (Raisbeck, 2000; Spallholz and Hoffman,
2002; Goldhaber, 2003). First, the possible substitution of
selenium for sulfur, due to their similar chemical properties,
in important biochemical reactions and structures such as
disulfide bonds, may disrupt normal function and cell integ-
rity. It has been suggested that replacing sulfur with sele-
nium in keratin is related to the abnormality in hair and hoof
produced by selenosis (Raisbeck, 2000). Secondly, the reac-
tion between selenite and glutathione consumes or depletes
cellular-free and protein-bound thiol levels, disturbing rel-
evant enzyme activities (Vernie et al., 1978). Lastly, free
radicals such as superoxide anions may be produced by the
reactions of certain forms of selenium with tissue thiols,
causing oxidative injuries to tissues (Hoffman, 2002; Kaur
et al., 2003; Balogh et al., 2004). This oxidation hypothesis
has received considerable attention (Barceloux, 1999). How-
ever, any single theory may not explain all modes of action
due to the diverse chemical properties and metabolism of
various selenium compounds.
SOURCES AND BIOAVAILABILITY
Soil selenium, via the growing of plant feeds and foods,
serves as the primary source of selenium for the nutrition of
humans and of grazing animals. However, the plant sele-
nium content depends on the amount of water-soluble or
available selenium, but not the total selenium in the soil
(NRC, 1983). The former is determined by the parent mate-
rials, pH, aeration, humus, and total iron contents of the soil
(Sun et al., 1985). Thus, selenium toxicosis, in particular to
grazing animals, likely occurs in some areas of Colorado,
South Dakota, North Dakota, northern Nebraska, Manitoba,
Alberta, and Saskatuan that have arid or semi-arid climates,
soils with pH levels above 7.0, and soils developed from
shale (Davis et al., 2000a,b). In the high pH, well-aerated
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SELENIUM
325
soils, the predominant form of selenium is selenate, which is
most soluble, mobile, and readily taken up by plants (Davis
et al., 2000a, b). In contrast, Hawaiian and Puerto Rican soils
contain selenium as high as 10-15 mg/kg, but do not pro-
duce toxic seleniferous vegetation because of the acidic pH
(4.5-6.5) and the presence of ferric hydroxide (Lakin, 1972).
Most soils contain 0.1 to 2 mg of Se/kg. Both topsoil and
subsoil should be sampled for selenium analysis because
subsoil may have a higher pH and selenium content than
topsoil. Soil selenium may be increased by applying manure
from selenium-supplemented animals, selenium fertilizer,
and selenium-bearing fly ash. Normal soil contains <2 mg of
total Se/kg or <50 |Jg of water soluble Se/kg, and plants
growing thereon contain <1 mg of Se/kg (Kappel et al.,
1984). Seleniferous soils exceed all three of these selenium
levels (Hintze et al., 2002; Lawler et al., 2004). Based on
detailed and specific analysis of soil selenium distribution,
U.S. soil is mapped into four types (Kubota and Allaway,
1972):
1. low — approximately 80 percent of all forages and
grain contain <0.05 Se mg/kg;
2. variable — approximately 50 percent of the plants con-
tain >0.1 Se mg/kg;
3. adequate — approximately 80 percent of all forages and
grains contain >0.1 mg Se/kg; and
4. local areas where selenium accumulator plants contain
>50 mg Se/kg.
The Great Lakes area and the Northeast, part of the West
Coast, and Florida belong to the low selenium region. Pas-
tures and forages from areas with selenium-responsive dis-
eases contain as low as 0.02-0.05 mg Se/kg, but at least 0. 1
mg Se/kg (dry basis) in many other areas (Underwood and
Suttle, 1999). Cereal grains and other seeds contain 0.006
to 3 mg Se/kg, depending on soil selenium (NRC, 1983).
Mean selenium concentrations in the feeds for cattle in
Louisiana (Kappel et al., 1984) ranged from 0.057 to 0.295
mg/kg of dry feed, among which bahia grass, mixed
ryegrass and oats, corn silage, and sorghum silage were
<0.1 mg/kg whereas Bermuda grass, alfalfa hay, and con-
centrates were >0.1 mg/kg.
In seleniferous areas, accumulator plants such as Astraga-
lus racemosus found in Wyoming and South Dakota, and
annual legume Neptunia amplexicaulis found in Queensland,
Australia, accumulate selenium at levels of 1,000-3,000 mg
Se/kg, and sometimes even reach 4,000-15,000 mg Se/kg
(Davis et al., 2000a, b). Soluble organic methyl-
selenocysteine and selenocystathionine represent the pre-
dominant forms of selenium in these accumulator plants
(Underwood and Suttle, 1999). A variety of plants can also
absorb high levels of selenium from seleniferous soils up to
1,000 mg Se/kg. These plants are called indicators because
they can be used to locate seleniferous soils. These plants are
also called converters because it is believed that they absorb
selenium from geological formations, such as virgin shales,
and convert it into soluble compounds for the use by other
plant vegetation. But, there is little direct evidence to sup-
port such a role by these plants (Raisbeck, 2000). Most ordi-
nary plants grown on normal soil contain <3 mg Se/kg, and
may reach 8-14 mg Se/kg when grown in seleniferous soils
(NRC, 1983; Hintze et al., 2002; Lawler et al., 2004). The
major form of selenium in seeds and forages is seleno-me-
thionine (Allaway et al., 1967; Olson et al., 1970), including
selenocystine, selenocysteine, and methylselenomethionine
(NRC, 1983).
Supplementation of selenium-containing minerals is
the most effective method to meet the selenium require-
ment of many species, in particular the nonruminants. The
most commonly used sources in the United States are so-
dium selenite and sodium selenate. Other sources of sele-
nium include calcium selenite (Mahan and Magee, 1991)
and selenium dioxide. Various selenium-enriched yeast
preparations are available and appear to have higher
bioavailability than sodium selenite in raising tissue, egg,
milk, and blood selenium levels, but lower bioavailability
for repleting selenium-dependent glutathione peroxidase
activity in pigs (Mahan, 2000). Bioavailability (digest-
ibility) of selenium to Atlantic salmon follows the order
from the highest to lowest: selenomethionine > selenite
> selenocystine > fish meal (Bell and Cowey, 1989). The
following approaches are used to enhance selenium in-
takes by grazing animals: (1) a free-choice selenium min-
eral supplement; (2) selenium fertilization of pasture;
(3) injection of selenium; (4) a selenium drench; and
(5) selenium ruminal bolus (McDowell, 2003). The sele-
nium-fortified salt mixture has also been used for sele-
nium delivery to the grazing animals. Wheat and hay
grown on seleniferous soils have been tested for enrich-
ing tissue selenium in beef cattle (Hintz, et al., 2002;
Lawler et al., 2004). Bioavailabilities of selenium in pet
foods range from 27 to 53 percent, and a factor of 30 per-
cent has been suggested for selenium in standard diets of
dogs and cats (Wedekind et al., 1998). It is very important
to mention that selenium is regulated by the federal gov-
ernment as a food additive. Sources of selenium and lev-
els of supplementation for various species are covered by
federal regulation (Title 21 Code of Federal Regulations,
part 573.920). Sources of selenium that are not listed in
this regulation are not permitted.
Selenium from normal surface or ground water (up to 1-
3 |Jg/L) in many parts of the world contributes little or in
negligible amounts to nutrition or toxicosis (NRC, 1983).
Although some natural water may contain selenium up to
400 mg/L, public water supplies seldom exceed 10 |Jg Se/L
(Barceloux, 1999). Irrigation of seleniferous soils or indus-
trial contamination can substantially elevate water selenium
to levels (>10 |Jg /L) toxic to fish and wildlife such as in the
San Joaquin Valley in California (Hamilton, 2004). Water
containing 10-25 |Jg Se/L may bear a garlicky odor, and
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MINERAL TOLERANCE OF ANIMALS
water containing 100-200 |ig Se/L has an astringent taste
(Pletnikova, 1970). Seawater contains approximately 0.04-
0.12 pg Se/L (Barceloux, 1999).
TOXICOSIS
Selenosis or selenium poisoning occurs in three situations.
First, grazing animals may suffer from subacute (blind stag-
gers) or chronic (alkali disease) selenium toxicosis in selenif-
erous areas such as the Rocky Mountain and Great Plains re-
gions of the western United States. Although the high
selenium plants, including obligate and facultative selenium
accumulators, have poor palatability and garlic-sulfur odor
that do not attract animals to eat them, overgrazing and/or
starvation may leave those animals no choice. High levels of
selenium intake may also result from excessive soil ingestion
(up to 15 percent of total DM intake) in periods of drought or
on heavily stocked pasture in late autumn or winter (Rogers et
al., 1990). Secondly, environmental contamination of agricul-
tural drain water, sewage sludge, and industrial activities in-
cluding fly ash from coal plants, oil refineries, and mining of
phosphates and metal ores can cause selenium toxicosis in
aquatic animals. Examples include fish kills and bird deformi-
ties at Belews Lake, NC (>10 \ig Se/L); Martin Lake, TX;
Kesterson Reservoir, CA (22 to 31 \ig Se/L); and aquatic re-
sources in southeastern Idaho and British Columbia
(Barceloux, 1999; Hamilton, 2004). Because of its
bioaccumulative nature in the food chain, selenium has be-
come a primary concern among many elements studied under
these conditions. Thirdly, selenium toxicosis can also be pro-
duced in various species by high levels of selenium supple-
mentation under experimental conditions or poor manage-
ment. In most cases, the selenium-intoxicated animals show
depressed growth performance, elevated selenium concentra-
tions in tissues, histopathology, clinical signs, or death.
Single Dose and Acute
Death may occur within a few hours or after several days,
if animals consume a large quantity of accumulator plants
such as Astragalus racemosus, which contains 100-9,000
mg of Se/kg (McDowell, 2003). These animals emit gar-
licky breath odor in exhaling dimethyl selenide and have an
abnormal gait. After a short-distance walk, they show an ini-
tial characteristic stance with head lowered and ears dropped.
The subsequent signs include vomiting, dyspnea, tetanic
spasms, and labored respiration. Eventually they die of res-
piratory or circulatory failure (Raisbeck, 2000). Pathologi-
cal changes include congestion of liver and kidney, en-
docarditis, myocarditis, and petechial haemorrages of the
epicardium (NRC, 1983).
Grace (1994) suggested that the LD^q of sodium selenite
for ruminants orally was 1.9-8.3 mg Se/kg BW. An oral dose
of 9-20 mg of Se/kg B W may be lethal to calves (Puis, 1 994) .
In sheep, the oral LD^q of sodium selenite is suggested as
10-15 mg Se/kg BW (Puis, 1994). Goats (6-8 months old)
died of a single dose of 40 mg of sodium selenite/kg BW
within 96 hours (Ahmed et al., 1990). For pigs, an oral dose
of 4.2 mg of Se/kg of BW for 3 days is lethal (Puis, 1994).
For poultry, the acute oral LD^q is 33 mg of Se/kg BW
(Puis, 1994). A recent Polish study (Szeleszczuk et al., 2004)
indicated that the lethal dose of selenium sodium selenite for
one-day-old male chicks was 2 mg of Se/chick. The minimal
lethal oral dose is 1.5-3 mg Se/kg BW for sodium selenite or
sodium selenate in rabbits, rats, dogs, and cats (NRC, 1983;
Puis, 1994). In a clinical case, a 3-year-old female Chihuahua
dog was killed by a single IM injection of selenium at 2.5
mg/kg BW (Janke, 1989). The dog had congested capillaries
in alveolar septae and abundant proteinaceous fluid in
alveolar lumina. Liver and kidney from the dog had 12.9 and
12.1 mg Se/kg, respectively, in comparison with the nonnal
concentrations of <3 mg Se/kg. The oral LD^q for sodium
selenite ranges from 2.3 to 13 mg Se/kg BW in rabbits,
guinea pigs, mice, and rats (EHC 58, 1986; Janke, 1989).
The LDjq for methyl selenide, trimethylselenonium, or
elemental selenium is 3- to 500-fold higher than that for
selenite in these species (NRC, 1983). Hamilton and Buhl
(1990) observed only increased surfacing behavior in
Chinook salmon and Coho salmon exposed to seleno-DL-
methionine up to 21.6 mg Se/L for 96 hours. Selenite was
significantly more toxic to both species than selenate, as the
estimated 96-hour LCjq was 13.4-17.0 mg Se/L for the
former and 1 14-149 mg Se/L for the latter, respectively, in
Chinook salmon in different waters.
Selenium injections are often administered to ruminants,
especially neonatal ruminants, as a rapid means of selenium
supplementation. The toxicity threshold for injected sele-
nium is much lower than that for ingested selenium. Inject-
able selenium is usually composed of sodium selenate, so-
dium selenite, or barium selenate, commonly prepared to
supply vitamin E as well, and generally administered at a
rate of 0.06-0. 1 mg Se /kg of BW at intervals of 1-6 months
(Meads et al., 1980). Toxicoses are occasionally encountered
following injection of selenium primarily because the con-
centration of selenium in the injectable preparation is under-
estimated or the preparation was given to supply vitamin E
without considering the selenium content of the injection.
The LDjq of intramuscular injection of selenite to 8- to 10-
week -old lambs is 0.5 mg Se/kg BW (Caravaggi et al., 1970).
Subcutaneous injection of selenite at a dose of 0.7 mg Se/kg
BW killed 50 percent of 10- to 1 1-month-old wethers (Grace,
1994). The LD^q of subcutaneous selenate injection is 1 mg
Se/kg BW in lambs and 1.9 mg Se/kg BW in adult cattle
(Grace, 1994). For pigs, a dose of 1.2-2 mg injectable Se/kg
BW is acutely toxic (Puis, 1994).
Subacute
"Blind staggers" is often considered a subacute selenosis
in grazing animals. Sometimes it is also described as a
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SELENIUM
327
chronic selenosis produced by a relatively long exposure
(weeks to months) to selenium-accumulator plants
(Underwood and Suttle, 1999). The affected animals initially
manifest signs of wandering, stumbling over objects, anor-
exia, and visual impairment, followed by increased severity
of these signs plus development of weak front legs. Because
the initial signs are not apparent, the toxicosis may not be
noticed until the final stage when the animals show blind-
ness, paralysis of the tongue and swallowing mechanism,
rapid and labored respiration, salivation, and low body tem-
perature. Once these clinical signs appear, animals usually
collapse and die within a few hours. As the neuropathology
of blind staggers cannot be reproduced by high levels of pure
selenium alone, other factors including alkaloid poisoning,
starvation, and polioencephalomacia might be responsible
for or confounded with the disorder (O'Toole and Raisbeck,
1995).
Chronic
Ruminants and Horses
Alkali disease is a "classical" chronic selenosis in graz-
ing cattle, horses, and sheep resulting from long exposure
(>30 days) to seleniferous forages and grains containing 5-
40 mg of Se/kg (NRC, 1983). This malady is usually associ-
ated with nonaccumulator plants instead of the obligate and
facultative selenium accumulators, and can also be produced
by overfeeding inorganic selenium or seleniferous feeds in
these and other species (Kim and Mahan, 2001a; Kaur et al.,
2003). The affected cattle, horses, and swine exhibit bilater-
ally symmetric alopecia and dystrophic hoof growth
(Raisbeck, 2000). Other signs in cattle and horses include
loss of appetite, unthriftiness, liver atrophy and cirrhosis,
nephritis, myocardial necrosis, loss of vitality, loss of hair,
and lameness (Table 25-1). Their hooves become elongated
and slough off after prolonged exposure to high levels of
selenium (O'Toole and Raisbeck, 1995). The lameness and
pain associated with deformed hooves may make the ani-
mals reluctant to move for food or water, thereby dying of
thirst and starvation (Underwood and Suttle, 1999). Because
of the efficient transfer of selenium by the placental and
mammary gland, calves and foals in seleniferous areas may
be born with deformed hooves or show the deformity during
the suckling period (Raisbeck, 2000).
Typical chronic selenosis, including hoof deformation
and alopecia, was produced by feeding yearling steers 0.28
(as selenomethionine) or 0.8 (as selenite) mg Se/kg BW for
120 days (O'Toole and Raisbeck, 1995). Similar signs were
also produced in calves fed sodium selenite at 0.25 mg Se/kg
BW for 16 weeks (Kaur et al., 2003). These animals also
exhibited elevated oxidative stress including lipid
peroxidation of tissues. However, feeding steers selenifer-
ous wheat or hay to supply 11.9 mg Se/kg of diet or 65 |ig
Se/kg BW for >100 days resulted in significantly increased
tissue selenium concentrations, but no signs of toxicity
(Hintze et al., 2002; Lawler et al., 2004). Adult Holstein
cows tolerated sodium selenite at up to 87-1 18 |ig Se/kg BW
for 128 days (Ellis et al., 1997). Reduced growth perfor-
mance and reduced blood packed cell volume were seen in
3-day-old calves fed 10, but not 5, mg Se/kg of diet (as
sodium selenite) (Jenkins and Hidiroglou, 1986). There are
no recent reports on experimentally produced selenium
toxicosis in horses, but field cases of naturally occurring
selenosis have been documented (Raisbeck et al., 1993;
Witte and Will, 1993). The signs of toxicosis included hoof
lesions and loss of mane and tail, without neurological dis-
orders. Alfalfa samples from the affected areas contained up
to 19-58 mg of Se/kg (Witte and Will, 1993).
Death and toxic selenium levels in tissues were observed
after sheep grazed for 4 weeks on high selenium forage
(<49 mg Se/kg DM) and drank high-selenium water (340-
415 \ig Se/L) (Fessler et al., 2003). However, no toxicosis
was produced in sheep grazing on forages containing <13
mg Se/kg DM with normal water (<1.7 pg Se/L). Ewes en-
dured selenium from sodium selenite (24 mg Se/kg diet) or
Astragalus (29 mg Se/kg) incorporated into alfalfa pellets
for 88 days, with only minor wool loss noted on the neck
and sides of some ewes (Panter et al., 1995). Goats receiv-
ing repeated daily doses of 0.25, 0.5, or 1 mg of sodium
selenite/kg BW for 225 days showed no clinical signs of
toxicosis or histological changes (Ahmed et al., 1990).
However, death was noted when the quantity of selenium
was increased to 5 mg/kg.
Swine
Growth depression seems to be one of the most sensitive
indicators of chronic selenosis in swine. Feeding pigs with
sodium selenite at 0, 4, 8, 12, 16, and 20 mg Se/kg of diet
had three effects: (1) a linear decrease in daily gain and feed
intake; (2) a quadratic increase in hair selenium; and (3) a
linear increase in blood selenium (Goehring et al., 1984a, b).
External signs of selenosis such as hoof lesion and paralysis
appeared in some pigs given 12 or 20 mg Se/kg. These re-
sults suggested that the toxic level of selenium in a corn-
soybean meal diet for crossbred pigs was between 4 and 8
mg Se/kg of diet. In another study with growing pigs (12.5
kg BW) fed sodium selenite or calcium selenite for 35 days,
growth and feed intake were reduced in pigs fed 10, but not
5, mg Se/kg compared with those fed 0.3 mg Se/kg (Mahan
andMagee, 1991). Hair loss and separation of the hoof at the
coronary band site occurred in pigs fed 10 mg Se/kg of diet
as sodium selenite, but at 15 mg Se/kg as selenium-enriched
yeast (Kim and Mahan, 2001a). Sodium selenite seemed to
be more potent than selenium-enriched yeast in reducing
growth performance, altering bile color, and elevating
plasma glutamic oxalacetic transaminase activity. If the se-
lenium intake is sufficiently high to severely reduce feed
intake, pigs consistently develop neurological signs such as
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328
MINERAL TOLERANCE OF ANIMALS
bilateral malacia of grey matter in the spinal cord (Goehring
et al., 1984b; Raisbeck, 2000). Neurological signs of paraly-
sis developed in growing pigs (8-10 weeks old) fed sele-
nium at 25 mg/kg diet for 6 weeks (Panter et al., 1996). How-
ever, the incident rate was 100 percent (5/5), 80 percent (4/
5), and 40 percent (2/5) in pigs fed Astragalus bisulcatus,
sodium selenite, and seleno-DL-methionine, respectively.
Polioencephalomalacia also developed in pigs fed Astraga-
lus bisulcatus. As the severity of the pathological changes
was not directly related to tissue or blood selenium concen-
trations, other factors such as swainsonine (the toxic chemi-
cal in locoweed) might contribute to the responses in the
Astragalus bisulcatus-tTeated group (Panter et al., 1996).
ties increased in the 16 and 64 mg Se/L groups. Reduced
BW gain, decreased food and water intake, and increased
dopamine metabolites in brain striatum resulted from giving
young mice selenium in drinking water at 3 or 9 mg Se/L for
14 days as sodium selenite, but not as selenomethionine
(Tsunoda et al., 2000). During a 50-week experiment, so-
dium selenite added to drinking water of rats at 8 mg Se/L
caused a 50 percent reduction in BW gain, decreased white
blood cell counts, and increased serum alkaline phosphatase
and glutamic oxaloacetice transaminase activities (Jacobs
and Forst, 1981b). However, those rats treated with 4 mg
Se/L showed no adverse response compared with the con-
trols (1 mg Se/L).
Poultry
Weight gain and feed efficiency in chicks were depressed
when dietary selenium level was 5 mg/kg or higher (Jensen,
1975, 1986; Elzubeir and Davis, 1988; Donaldson and
McGowan, 1989; Vanderkop andMacNeil, 1990). One study
showed no adverse effect of 5 mg of Se/kg on growth perfor-
mance of chicks (Jensen and Chang, 1976), but another study
showed adverse effects of 1 and 3 mg of Se/kg (sodium se-
lenite) on growth and tissue integrity of hybro-type chicks
(Dafalla and Adam, 1986). The effect of sodium selenite
seems to be more severe than that of selenomethionine
(Lowry and Baker, 1989). Egg production and hatchability
were decreased in emu hens during a 4-month selenium
supplementation at 1.55 mg Se/kg DM (Kinder et al., 1995).
Egg production was increased by 23 percent in the following
years by decreasing selenium supplementation. When day-
old ducklings were fed a wheat basal diet containing 30 mg
Se/kg of diet as seleno-L- or DL-methionine, or selenized
yeast, for two weeks, survival was 36, 100, and 88 percent,
respectively (Heinz et al., 1996). When the basal diet was
changed to a commercial duck feed, no mortality occurred
with these sources. In another duckling study with three dif-
ferent sources of selenium at 10 mg Se/kg, no effect on health
or survival of mallards was observed (Heinz and Hoffman,
1996).
Laboratory Animals
Feeding 4-week-old hamsters either sodium selenite or
selenomethionine at 5.0 mg Se/kg of diet for 21 days pro-
duced no adverse effects (Julius et al., 1983). However, in-
creasing dietary selenium level to 10 mg /kg or higher caused
growth depression and (or) mortality. Similarly, rats given
sodium selenite in drinking water at 4 mg Se/L for 1-2 years
showed no changes in BW or survival compared with the
controls (Jacobs and Forst, 1981a). In another 35-day ex-
periment, rats given 64 mg Se/L of drinking water died by
day 18. The survival was also decreased in rats given 8 and
16 mg Se/L. BW gain was decreased and serum alkaline
phosphatase and glutamic oxaloacetic transaminase activi-
Flsh
Because of the fish kills and bird deformities at Belews
Lake, NC, Kesterson Reservoir, CA, and other sites, great
progress on selenium toxicity in the aquatic species has been
made during the last two decades. Hamilton (2004) has pro-
vided an excellent review on the background, progress, and
current status of the field. Canadian researchers demon-
strated that for rainbow trout, the minimal requirement of
selenium was between 0.15 and 0.38 mg/kg of dry feed, the
definite toxic level was 13 mg Se/kg diet, and the possible
toxic level with prolonged exposure was 3 mg Se/kg. The
massive disappearance of several fish species in Belews
Lake, NC, was related to the rather high selenium level (5-
10 l-ig/L) in the water. Studies on fish die-off s in Colorado
and Wyoming indicated that the selenium toxicosis in fish
was via the food chain. Based on mortality, growth depres-
sion, reproduction impairment, and migration, Hamilton
(2004) listed the following adverse selenium levels for rain-
bow trout, Chinook salmon, fathead minnow, striped bass,
bluegill, and razorback sucker: 2.4-70 mg Se/kg of dry feed
(diets), and 47-472 pg/L (water). In most cases, reduced
growth or survival occurred at dietary selenium levels close
to 3 mg/kg or at whole-body selenium residues close to 4
mg/kg. The sources of selenium in these studies included
sodium selenite, selenomethionine, and various types offish.
Selenomethionine seemed to be the most toxic form of sele-
nium for fish.
Reproduction
Selenosis in poultry results in poor hatchability and de-
formed, rudimentary, or lack of legs, toes, wings, beaks, and
eyes in the young (Latshaw et al., 2004). The chick embryo is
very sensitive to selenium toxicity as shown by the 100 per-
cent mortality of all embryos within 48 hours post administra-
tion of selenium (sodium selenite) at 0.02 mg per embryo
(Szeleszczuk et al., 2004). Hatchability of eggs is affected by
very low dietary selenium levels (Ort and Latshaw, 1978) that
normally do not produce any effect in other species. A field
study indicated that egg production and hatchability were de-
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SELENIUM
329
creased in hens during a 4-montli supplementation of sele-
nium at 1 .55 mg Se/kg DM (Kinder et al., 1995). This level of
dietary selenium also resulted in dead embryos and a high
incidence of leg deformities in surviving chicks. These
changes were partially reversed in the following years when
selenium supplementation was decreased to 0.52 mg Se/kg.
When adult male and female ducklings were given three
sources of selenium at 10 mg Se/kg, hatching of fertile eggs
was significantly lower for females fed seleno-DL-methion-
ine (7.6 percent) or seleno-L-methionine (20 percent) than for
controls (41.3 percent, 0.56 mg Se/kg) (Heinz and Hoffman,
1996). Both seleno-L-methionine and seleno-DL-methionine
significantly decreased the number of 6-day-old ducklings
produced per hen, and the former also decreased the survival
percentage of young to 6 days old. Comparatively, the
selenized yeast showed either no or much less effect on these
measures, implying a lower toxicity. Recent studies on the
adverse effects of high dietary selenium levels on reproduc-
tion of birds have been reviewed by Hamilton (2004).
The impacts of high selenium on reproductive perfor-
mance in ruminants are far less clear than in avian species.
Although there are field reports on decreased conception in
cattle and sheep, no direct evidence has been produced ex-
perimentally (Raisbeck, 2000). BW gain, estrous cycle
length and frequency, and lambing of yearling ewes were
not affected by feeding a high level of sodium selenite (24
mg Se/kg of diet) or Astragalus (29 mg Se/kg) incorporated
into alfalfa pellets for 88 days (Panter et al., 1995). When
sows were fed a basal diet (0.13 mg Se/kg) supplemented
with selenium (as sodium selenite) at 0, 2, 4, 8, or 16 mg/kg
from the first estrous cycle through 9 weeks postpartum,
conception rate, protein and fat content of colostrum or milk,
number of piglets born, and piglet mortality were not af-
fected by dietary selenium levels (Poulsen et al., 1989). Pig-
lets born from sows on the two highest selenium levels
tended to have lower birth weights than the controls, but the
differences were not significant. Weaning weights of piglets
(21 days) tended to be negatively influenced by selenium
treatment (P = 0.08). At 9 weeks of age, piglet BWs and
daily feed intakes (from 3 to 9 weeks) were lower in the two
highest dose groups compared to the controls. A circular dark
band was seen in the hoofs of some sows on high selenium
supplementation. When gilts were fed 0.3, 3, 7, and 10 mg
Se/kg of diet as sodium selenite or selenium-enriched yeast
from 25 kg BW through the first parity, both sources of sele-
nium were toxic at the two highest levels (Kim and Mahan,
2001b). It is intriguing that the organic selenium had more
severe effects on reproductive performance of the gilts dur-
ing gestation, whereas inorganic selenium was more detri-
mental to the nursing pigs during lactation.
Teratogenicity
Chick eggs and embryos are very susceptible to the ter-
atogenic effect of selenium. Injecting sodium selenite into
eggs up to 0.6 mg Se/kg resulted in 50 percent dead and 50
percent abnormal embryos (EHC 58, 1986). Methylselenic
acid seems to be more potent in this regard than selenate,
selenite, and selenomethionine. Breeding ring-necked
pheasants receiving feed containing 9.3 mg of Se/kg had
deformed beaks and abnormal eyes in 10 percent of chicks
hatched and deformities in more than 50 percent of all em-
bryos developed, including those that died in the shell
(Latshaw et al., 2004). The eggs without embryonic devel-
opment contained 2.05 mg of Se/kg. Likewise, teratogen-
esis is a biomarker of selenium toxicosis in fish and wild
birds at the embryo-larval stage, and can be found in sele-
nium-contaminated ecosystems such as in San Luis Drain,
CA (Hamilton, 2004). Fish deformities include lordosis,
kyphosis, scoliosis, and abnormal head, mouth, gill cover,
and fin. Deformity was produced in mallard (adults or
ducklings) by feeding 8-25 mg Se/kg of diet as selenite,
selenomethionine, or selenized yeast (Heinz and Hoffman,
1996; Hamilton, 2004). Except for the deformed hooves,
teratogenic effect of selenium in mammals is inconclusive.
The relatively lower selenium accumulation in fetus than
in eggs may be partially responsible for the stronger resis-
tance of mammals to the teratogenic effect of selenium than
that of birds (Barceloux, 1999).
Carcinogenicity and IVIutagenicity
Although several earlier studies suggested that high
levels of selenium promoted carcinogenesis, recent animal
experiments and human epidemiological and intervention
studies (Clark et al., 1996) have shown the opposite role
of selenium. Thus, selenium salts are not listed as a sus-
pected carcinogen by the International Agency for Research
on Cancer or the U.S. National Toxicology Program
(Barceloux, 1999).
Humans
Endemic human selenium toxicosis has been reported in
seleniferous areas of China when whole blood selenium level
was > 1 mg/L and daily selenium intake was >900 mg (Yang
and Zhou, 1994). The common symptoms of all patients in-
cluded broken hair strands or nail damage. Chronic selenium
toxicosis may also develop in individuals inhaling selenium
fumes or ingesting overdoses of potent selenium tablets
(Sunde, 1997). Symptoms include nausea and vomiting, nail
thickening and ridging, hair loss, fatigue, irritability, abdomi-
nal cramps, watery diarrhea, paresthesis, dryness of hair, and
garlicky breath (Barceloux, 1999).
Factors Influencing Toxicity
While the mechanism of selenium toxicity remains un-
clear, factors influencing its toxicity have been well studied.
These factors include species, age, and physiological status
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MINERAL TOLERANCE OF ANIMALS
of the target animals, chemical form and nutritional nature
of selenium, and dietary (water) conditions.
Species, Age, and Status of Animals
Poultry, fish, and aquatic birds seem to be more suscep-
tible to the teratogenic effect of selenium than mammals
(Barceloux, 1999; Hamilton, 2004). Adverse effects of high
selenium intake on egg hatchability in poultry and reproduc-
tion in swine are evident (Kim and Mahan, 2001b). Sheep
may be somewhat more resistant to toxicity of selenium from
organic sources than are cattle and horses (Raisbeck, 2000).
Susceptibility of different fish species to selenium toxicity
varies greatly. For example, Coho salmon are more sensitive
than Chinook salmon to inorganic selenium (Hamilton and
Buhl, 1990). The elimination of fish species from contami-
nated aquatic communities is highly selective (Hamilton,
2004). Young animals are less tolerant of selenium than adult
animals (Hamilton and Buhl, 1990; Raisbeck, 2000). Vita-
min E-deficient animals are more susceptible to selenium
toxicity than are vitamin E-adequate animals (NRC, 1983).
Ctiemicai Form and Nutritional Nature of Selenium
As in the case of bioavailability, the relative toxicity of a
given selenium compound is affected by its chemical form
and solubility. The highly insoluble elemental selenium is
much less toxic to many species than other more soluble forms
such as selenite and selenate (NRC, 1983). It is generally true
that organic forms of selenium are more effective in raising
tissue selenium concentrations than the inorganic selenite or
selenate (Kim and Mahan, 2001a; Hintze et al., 2002). How-
ever, the relative toxicity of selenium is not directly related to
tissue selenium levels (Panter et al., 1996). Depression of
growth performance was less by the same amount (15 mg/kg)
of selenium as selenomethionine than as selenite in chicks
(Lowry and Baker, 1989). Similarly, seleno-DL-methionine
was less toxic to Chinook salmon and Coho salmon than se-
lenite or selenate (Hamilton and Buhl, 1990). However, the
opposite was true in other studies (O'Toole and Raisbeck,
1995; Hamilton, 2004). The same level of selenium from As-
tragalus bisulcatus produced more severe and disseminated
lesions in pigs than that from sodium selenite or
selenomethionine, suggesting that factors other than selenium
might contribute to or modulate selenium toxicity (Panter et
al., 1996). In mallard ducklings, both DL and L forms of
selenomethionine were more toxic than selenized yeast (Heinz
and Hoffman, 1996). Selenite is taken up more efficiently than
selenate by aquatic plants, and is more toxic to aquatic inver-
tebrates and fish (Hamilton and Buhl, 1990).
Dietary Conditions
Certain dietary conditions and factors can enhance or re-
duce selenium toxicity. In general, selenium is more toxic to
animals if it is added in semi-purified diets than in practical
diets (Heinz et al., 1996). Appetite and growth were impaired
in swine fed 8 mg Se/kg of DM as selenite in a corn-soybean
meal diet, but not in a wheat and oats diet (Goehring et al.,
1984b). High levels of dietary protein and sulfur-containing
amino acids (Hamilton, 2004) may help reduce selenium tox-
icity. Cyanogenic glycosides (Palmer et al., 1980) are con-
sidered the mediator of protection by linseed meal against
chronic selenium toxicosis (Jensen and Chang, 1976). Di-
etary supplementation of sodium nitroprusside (Elzubeir and
Davis, 1988) or monensin (Jensen, 1986; Vanderkop and
MacNeil, 1990) has been shown to reduce selenium toxico-
sis in chicks. High levels of dietary sulfate and sulfur may
protect against selenium toxicity as the former increases uri-
nary excretion of selenate in rats (Halverson et al., 1962),
and the latter decreases absorption of selenite in lactating
cows (Ivancic and Weiss, 2001).
A number of trace elements including antimony, arsenic,
bismuth, cadmium, copper, germanium, mercury, silver, and
tungsten can affect selenium use (Rahim et al., 1986) and
thus attenuate selenium toxicity in mammals, fish, and birds
(Jensen, 1975; Donaldson and McGowan, 1989; Hamilton,
2004). The protection of arsenic compounds against sele-
nium toxicosis has been shown in various species fed differ-
ent forms of selenium (Levander, 1977; Lowry and Baker,
1989; Hamilton, 2004). A possible mechanism is the en-
hanced biliary excretion of selenium by arsenic. High levels
of copper reduced selenium retention in tissues of fish, but
had no biological effect (Hamilton, 2004). Long-term inges-
tion of moderate levels of copper might affect selenium dis-
tribution and retention in sheep (White et al., 1989). The
antagonistic interaction between selenium and mercury (El-
Begearmi et al., 1977; Urano et al., 1997; Hoffman and
Heinz, 1998) is of great significance in fish for food safety
and environmental protection. Although many have reported
simultaneous bioaccumulation of these two elements, no
evidence exists for a natural joint deposition of both in fishes,
crustaceans, or mollusks (Hamilton, 2004). Mercury accu-
mulation in fish carcass is reduced by relatively low levels
of selenium addition, but may be increased by adding high
levels of selenium (Klaverkamp et al., 1983). As combined
selenium and mercury exposure is more toxic than separate
exposures to aquatic life (Hoffman and Heinz, 1998), there
is limited practical value of selenium and mercury antago-
nism. The consistent effects of other elements on the toxicity
of different forms of selenium and the practical implications
are unclear.
TISSUE LEVELS
Puis (1994) provided a comprehensive list of selenium
concentrations in selected tissues and fluids in various spe-
cies fed dietary selenium (mg/kg feed) at deficient (<0.10),
marginally adequate (0.10-0.25), adequate (0.3-2), high (3-
5), chronically toxic (>5), or acutely toxic levels (>20-80).
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SELENIUM
331
Data from the recent individual studies are summarized in
Table 25-2. In most cases, kidney has the highest selenium
concentration among all tissues assayed. The concentrations
of selenium in kidney of steers fed nonnal to moderate di-
etary levels of selenium are about 2-2.5 mg/kg DM (Hintze
et al., 2002; Lawler et al., 2004), whereas the concentrations
of selenium in kidney of chicks and laying hens fed corn-soy
or corn-torula yeast basal diets (0.03-0.10 mg Se/kg) range
from 0.18 to 0.32 mg/kg (Latshaw, 1975; Osman and
Latshaw, 1976). When fed selenium-adequate diets,
liver:kidney selenium concentration ratios are approximately
1/3 in steers (Lawler et al., 2004), 1/10 in calves (Ammerman
et al., 1980), 1/4 in pigs (Kim and Mahan, 2001a,b), and 1/2
in rats (Janhorbani et al., 1990). However, these two tissues
seem to share similar selenium concentrations in chicks
(Osman and Latshaw, 1976), laying hens (Latshaw, 1975),
and hamsters (Julius et al., 1983). Spleen has slightly lower
selenium concentrations than liver in both cattle (Lawler et
al., 2004) and swine (Kim and Mahan, 2001a, b). Muscle has
the lowest selenium concentrations among all assayed tis-
sues across all species. Other soft tissues such as lung, heart,
pancreas, and brain have selenium concentrations that fall
between liver and muscle (Panter et al., 1996; Kim and
Mahan, 2001a,b). All tissues can accumulate more selenium
with increasing dietary selenium supplementation, and the
elevation can reach 40- to 50-fold over the baseline or nor-
mal levels (Kim and Mahan, 2001a). In various species, or-
ganic selenium sources are more effective than inorganic
selenium salts in raising tissue selenium levels (Lowry and
Baker, 1989; Butler et al., 1990; Kim and Mahan, 2001a,b;
Lawler et al., 2004), and selenomethionine seems to be most
potent in this regard (Heinz and Hoffman, 1996; Panter et al,
1996).
Plasma selenium concentrations in various species range
from 0.02 to 0.20 mg/L, and can be increased up to 3.2 mg/L
in pigs fed selenized yeast at 20 mg Se/kg of diet (Stowe and
Herdt, 1992; Kim and Mahan, 2001a). Red blood cells con-
tain higher selenium concentrations than plasma (Salbe and
Levander, 1990). Milk of U.S. cows contains 20-40 |ig Se/L
(Maus et al., 1980). A New Zealand study (Knowles et al.,
1999) showed that milk produced by cows grazing on pas-
ture identified as marginal to deficient in selenium (0.035
mg Se/kg of DM) contained 2.1 to 8.3 |Jg Se/L, varying with
seasons. Treating cows with drenches of sodium selenite or
selenized yeast at 2 or 4 mg Se/day for 133 days resulted in
1.5-5.5 times greater milk selenium concentrations (up to
25.3 [ig Se/L). Approximately 71 percent of whole milk se-
lenium was associated with casein, which from the selenium-
treated cows contained as much as 1 .4 mg Se/kg (Knowles et
al., 1999). Sow milk contains approximately 40 mg Se/L,
and a 10-fold increase over the baseline was produced by
feeding gilts with selenized yeast at 10 mg Se/kg diet (Kim
and Mahan, 2001b). Colostrum contains higher levels of se-
lenium concentration than regular milk (Abdelrahman and
Kincaid, 1995), and the level is also highly dependent on
dietary selenium intake (Kim and Mahan, 2001b). Egg white
contains approximately 0.4-0.5 mg Se/kg of DM, and can be
increased to 2.47 mg Se/kg diet by feeding a moderately
high level of organic selenium (0.42 mg Se/kg) (Latshaw,
1975; Jacobs et al., 1993). Concentrations of selenium in the
eggs laid by mallards, shortly after placement on a diet that
was 10 mg Se/kg as the DL or L form of selenomethionine,
were elevated from 0.41 mg/kg in the control group (wet
basis) to 9.1 mg/kg (Heinz and Hoffman, 1996). The eleva-
tion was greater (P <0.05) than that produced by selenized
yeast (22- vs. 16-fold).
Hair of cattle from areas of soil with normal amounts of
selenium contains 1-4 mg Se/kg of DM, and may reach 10-
30 mg Se/kg in seleniferous regions (Lawler et al., 2004).
Gilts fed 0.3 mg Se/kg diet as selenite had a hair selenium
concentration of 0.49 mg/kg (fresh basis), and reached 8-1 1
mg/kg in groups fed 7-10 mg Se/kg as selenized yeast (Kim
and Mahan, 2001b). In swine, hooves had slightly lower se-
lenium concentrations than hair, but were still as high as 29
mg/kg (fresh basis) in pigs fed 15 mg Se/kg as selenized
yeast (Kim and Mahan, 2001a,b). Hair, hoof, and nail have
been used for determining body selenium status, but caution
should be given in sampling these tissues and interpreting
the results because other factors such as dietary methionine
affect the selenium content of these tissues (Salbe and
Levander, 1990).
Through a homeostasis mechanism (via reduced intake or
depuration), the juvenile fathead minnow reduced the whole
body selenium concentration from the initial value of ap-
proximately 14 mg/kg to that close to the selenium concen-
trations in the food (5-11 mg of Se/kg) (Hamilton, 2004).
Criteria based on tissue selenium are considered more reli-
able than selenium concentrations in water for predicting
adverse effects of selenium in fish (Hamilton, 2004).
MAXIMUM TOLERABLE LEVELS
Selenium is considered rather toxic, and selenium poison-
ing can be a practical problem in grazing animals (Ullrey,
1992). The rather recent fish kills and bird deformities related
to selenium bioaccumulation from agricultural irrigation and
industrial contamination at several aquatic resources
(Hamilton, 2004) have highlighted the immediate risk of sele-
nium toxicity to the ecosystems. Meanwhile, the illustration
of possible anti-cancer action by superanutritional levels of
selenium in humans (Clark et al., 1996; Ip, 1998) has led to an
interest in producing selenium-enriched meats, milk, and eggs
by feeding animals with selenized grain, hay, or yeast (Lawler
et al., 2004). Thus, establishing the accurate maximum allow-
able tolerable levels of selenium for various species has broad
implications. The challenge is that these levels vary widely
with the form and source of selenium, exposure duration, na-
ture of diet, and end points of tolerance.
The maximum tolerable level of a mineral is the dietary
level that, when fed for a defined period of time, will not
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332
MINERAL TOLERANCE OF ANIMALS
impair animal health and performance. A single level of 2
mg Se/kg of diet was suggested by the former NRC commit-
tee (NRC, 1980) as the maximum tolerable level for all spe-
cies. This recommendation has been challenged (Underwood
and Suttle, 1999; McDowell, 2003) as an underestimate of
selenium tolerances by several species, especially for the
ruminants under practical dietary conditions (Cristaldi et al.,
2005). Based on the data presented in Table 25-1, various
types of cattle showed no adverse response to 5-12 mg Se/kg
of DM or 65-150 |Jg Se/kg of BW for up to 4 months. Sheep
seem to be more tolerant of selenium than cattle as they dis-
played no toxic signs when fed 9-10 mg Se/kg DM (as se-
lenite) (Echevarria et al., 1988; Cristaldi et al., 2005) or when
grazing forages containing <13.0 mg Se/kg DM (Fessler et
al., 2003). Only minor wool loss was observed in ewes fed
24-29 mg Se/kg DM as selenite or Astragalus bisculcatus
(Panter et al., 1995). Therefore, it is reasonable to increase
the maximum tolerable level of selenium for ruminants to
5 mg of Se/kg DM. This level seems to be appropriate for
horses as well.
Compared with the selenium-adequate controls, pigs fed
3-5 mg Se/kg diet in several studies showed no inferior
growth, reproduction, or health (Goehring et al., 1984a,b;
Mahan and Magee, 1991; Kim and Mahan, 2001a,b; Poulsen
et al., 1989). Because growth rate and feed intake were re-
duced by 5 mg Se/kg diet in one study with weanling pigs
(Moxon and Mahan, 1981), and pigs are rather efficient in
absorbing dietary selenium, it seems appropriate to set the
maximum tolerable level of selenium for swine at 4 mg
Se/kg of DM. Growth and appetite were reduced by adding
selenite into drinking water of chicks at 4 mg of Se/L
(equivalent to 7 mg Se/kg feed intake) (Cantor et al., 1984)
or into feed above 5 mg of Se/kg (Jensen, 1975). As hatch-
ability of eggs is very sensitive to selenium toxicity and
5 mg Se/kg DM appears to be the borderline for this effect
(Ort and Latshaw, 1978) and also for the growth depression
effect (Jensen and Chang, 1976; Jensen, 1986), the maxi-
mum tolerable level of selenium for poultry is set at 3 mg of
Se/kg of feed.
Based on many laboratory and field studies (Hamilton,
2004), the selenium thresholds for adverse effects in fish and
aquatic birds are ?)—A mg/kg DW in diet and 2-5 |Jg/L in
water. Thus, a tentative maximum tolerable level of sele-
nium is suggested as 2 mg of Se/kg of dry feed for fish and
aquatic birds. Apparently, more research is needed for de-
fined levels and appropriate safety factors for these species.
A study by Levander (1986) indicated that a dietary sele-
nium concentration of 5 mg/kg was toxic to dogs. Although
an upper limit of 2.0 mg of Se/kg of dog foods has been
suggested by AAFCO (2001) for regulatory purposes, there
are no data for this committee to set a maximum tolerable
levels of selenium for dogs or cats (Wedekind et al., 2004).
A study in China (Yang and Zhou, 1994) indicates that
600 |Jg Se/day is considered the maximum individual safe
selenium intake for humans. The current RDA is 55 |Jg/day
for both men and women, and the tolerable upper intake level
(UL) for adults is set at 400 |ig/day by the Dietary Reference
Intakes committee. Institute of Medicine (lOM, 2000). As
eggs and muscle produced by animals fed diets supple-
mented with maximal tolerable levels of selenium, in par-
ticular with organic forms, may contain 0.7-2.5 mg Se/kg
(Table 25-2), a consumption of 200 to 600 g of such prod-
ucts by a person per day could exceed the suggested UL.
Thus, proper caution must be exercised whenever animal
diets are supplemented with selenium.
FUTURE RESEARCH NEEDS
Maximum tolerable levels of selenium for given species in
the future should be specifically defined with different forms
of selenium, duration of exposure time, and nature of diet.
Basic research on the impact of high levels of selenium on
gene expression and cell signaling related to cell death and
survival may help in understanding the molecular mechanisms
of selenium toxicity. Effects of different dietary sources and
levels of selenium on the expression and function of the
selenoproteins other than glutathione peroxidase- 1 should be
studied in various farm animals. Impacts of feeding selenized
feedstuffs to food animals on environmental accumulation, in
particular on the possible toxicity to fish and aquatic birds,
should be examined. Potential human nutrition and health ben-
efits and risks of selenium-enriched animal products, gener-
ated from feeding animals with selenized plants or yeast, merit
careful and long-term research.
SUMMARY
Selenium is a semimetal (metalloid) with four natural
oxidation states (-2, 0, H-4, and +6), and it shares similar
chemical and biological properties with sulfur. Up to now, a
total of 12 selenium-dependent enzymes and 13 seleno-
proteins have been identified in humans. The synthesis of
seleno-enzymes or proteins is featured by the incorporation
of selenium into the peptide as a selenocysteine moiety
through a "co-translation" mechanism. Although the meta-
bolic roles of many selenoproteins remain unknown, it is
clear that the selenoenzymes are involved in antioxidation
and thyroid hormone metabolism. Many sources of selenium
are readily absorbed in the small intestine by animals and
humans, and regulation of body selenium retention may
occur via urinary excretion. In all species, selenium contents
of tissues, blood, and milk (eggs) can be increased up to 50-
fold of the normal baseline by dietary selenium supplemen-
tation. Organic selenium sources seem to be more effective
than inorganic selenium salts, and selenomethionine may be
more effective than selenized plants in raising tissue sele-
nium concentrations.
Plant selenium contents depend on the amount of sele-
nium in soil in which they grow, and vary greatly in different
regions. Thus, both selenium deficiency and selenium toxi-
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SELENIUM
333
cosis are practical problems around the world. Selenium de-
ficiency produces selenium-responsive diseases such as liver
necrosis in rats, exudative diathesis in chicks, hepatosis
dietetica in swine, white muscle disease in ruminants, and
reproduction failure in various species. Selenium toxicosis
may occur in animals grazing in seleniferous areas, in fish
and birds that inhabit contaminated aquatic sites, and in ani-
mals overdosed with selenium under experimental condition
or poor management. Sub-acute (blind staggers) and chronic
(alkali disease) selenosis are more frequently seen than the
acute toxicosis. Depression of growth performance is a very
sensitive indicator of chronic selenium toxicosis across dif-
ferent species. Loss of hair and deformed hooves are also a
feature of chronic selenosis in swine, cattle, and horses. Pigs
consistently show neurological pathology under selenium
toxicosis. Fish and birds including chicks and ducks are more
susceptible to the teratogenic effect of selenium than mam-
mals. Young animals are more sensitive to selenium toxicity
than adult or old animals. Relative toxicity of different sele-
nium supplements is largely related to their water solubility
and nutrient bioavailability, and can be modulated by di-
etary factors such as protein, sulfate, vitamin E, and a num-
ber of trace elements including arsenic, copper, and mer-
cury. Selenium is not listed as a suspected carcinogen. The
maximum tolerable levels (mg/kg of diet or DM) of sele-
nium are suggested as follows: ruminants, 5; swine, 4; poul-
try, 3; and fish and aquatic birds, 2.
REFERENCES
AAFCO (Association of American Feed Control Officials). 2001. Official
Publication. Harrisburg, PA.
Abdelrahman, M. M., and R. L. Kincaid. 1995. Effect of selenium supple-
mentation of cows on maternal transfer of selenium to fetal and new-
born calves. J. Dairy Sci. 78:625-630.
Ahmed, K. E., S. E. I. Adam, O. F. Idrill, and A.A. Wahbi. 1990. Experi-
mental selenium poisoning in Nubian Africa goats. Vet. Hum. Toxicol.
32:249-251.
AUaway, W. H.,E. E. Cary, andC.F. Ehlig. 1967. The cycling of low levels
of selenium in soils, plants, and animals. Pp. 273-296 in Selenium in
Biomedicine, O. H. Muth, ed. Westport, CT: AVI.
Ammerman, C. B., H. L. Chapman, G. W. Bowman, J. P. Fontenot, C. P.
Bagley, and A. L. Moxon. 1980. Effect of supplemental selenium for
beef cows on the performance and tissue selenium concentrations of
cows and suckling calves. J. Anim. Sci. 51:1381.
Balogh, K., M. Weber, M. Erdelyi, and M. Mezes. 2004. Effect of excess
selenium supplementation on the glutathione redox system in broiler
chiciien. Acta Vet. Hung. 52:403^11.
Barceloux, D. G. 1999. Selenium. Clin. Toxicol. 37:145-172.
Beclc, M. A., Q. Shi, V. C. Morris, and O. A. Levander. 1995. Rapid genomic
evolution of a nonvirulent coxsacitievirus B3 in selenium-deficient mice
results in selection of identical virulent isolates. Nature Med. 1:405^06.
Bell, J. G., and C. B. Cowey.1989. Digestibility and bioavailability of di-
etary selenium from fishmeal, selenite, selenomethionine, and
selenocystine in Atlantic salmon (Salmo salar). Aquaculture 81:61—68.
Brown, K. M., and J. R. Arthur. 2001. Selenium, selenoproteins, and human
health: a review. Public Health Nutr. 4:593-599.
Burii, R. F., K. E. Hill, and A. K. Motley. 2003. Selenoprotein metabolism
and function: evidence for more than one function for selenoprotein P.
J. Nutr. 133:1517S-1520S.
Butler, J. A., P. D. Whanger, A. J. Kaneps, andN. M. Patton. 1990. Metabo-
lism of selenite and selenomethionine in the Rhesus monlcey. J. Nutr.
120:751-759.
Cantor, A. H., and M. L. Scott. 1975. Influence of dietary selenium on
tissue selenium levels in turkeys. Poult. Sci. 54:262-265.
Cantor, A. H., D. Nash, and T. H. Johnson. 1984. Toxicity of seleniumin
drinking water of poultry. Nutr. Rep. Int. 29:683-688.
Caravaggi, C, F. L. Clark, and A. R. Jackson. 1970. Acute selenium toxic-
ity in lambs following intramuscular injection of sodium selenite. Res.
Vet. Sci. 11:146-149.
Chen, X., G. Yang, J. Chen, X. Chen, Z. Wen, and K. Ge. 1980. Studies on
the relations of selenium to Keshan disease. Biol. Trace Elem. Res.
2:91-104.
Cheng, W. H., Y. S. Ho, B. A. Valentine, D. A. Ross, G. F. Combs, Jr., and
X. G. Lei. 1998. Cellular glutathione peroxidase is the mediator of body
selenium to protect against paraquat lethality in transgenic mice. J. Nutr.
128:1070-1076.
Cheng, W. H., B. A. Valentine, and X. G. Lei. 1999. High levels of dietary
vitamin E do not replace cellular glutathione peroxidase in protecting
mice from oxidative stress. J. Nutr. 129:1951-1957.
Chu, F. F., R. S. Esworthy, P. G. Chu, J. A. Longmate, M. M. Huycke,
S. Wilczynski, and J. H. Doroshow. 2004. Bacteria-induced intestinal
cancer in mice with disrupted Gpxl and Gpx2 genes. Cancer Res.
64:962-968.
Clark, L. C, G. F. Combs, Jr., B. W. Turnbull, E. H. Slate, D. K. Chalker, J.
Chow, L. S. Davis, R. A. Glover, G. F. Graham, E. G. Gross, A. Krongrad,
J. L. Lesher, Jr., H. K. Pai'k, B. B. Sanders, Jr., C. L. Smith, and J. R.
Taylor. 1996. Effects of selenium supplementation for cancer prevention
in patients with carcinoma of the skin. JAMA 276:1957-1963.
Cristaldi, L. A., L. R. McDowell, C. D. Buergelt, P. A. Davis, N. S.
Wilkinson, and F. G. Martin. 2005. Tolerance of inorganic selenium in
wether sheep. Small Rumin. Res. 56:205-216.
Dafalla, R., and S. E. Adam. 1986. Effects of various levels of dietary sele-
nium on hybro-type chicks. Vet. Hum. Toxicol. 28:105-108.
Davis, J. G., T J. Steffens, T E. Engle, K. L. Mallow, and S. E. Cotton.
2000a. Diagnosing Selenium Toxicity. Natural Resources Series. No.
6. 109. Cooperative Extension, Colorado State University. Online. Avail-
able at http://www.ext.colostate.edu/pubs/natres/06109.html. Accessed
April 18, 2005.
Davis, J. G., T. J. Steffens, T. E. Engle, K. L. Mallow, and S. E. Cotton.
2000b. Preventing Selenium Toxicity. Natural Resources Series. No.
6.110. Cooperative Extension, Colorado State University. Online. Avail-
able at http://www.ext.colostate.edu. Accessed April 18, 2005.
Deagen, J. T, J. A. Butler, M. A. Beilstein, and P. D. Whanger. 1987.
Effects of dietary selenite, selenocystine, and selenomethionine on
selenocysteine lyase and glutathione peroxidase activites and on sele-
nium levels in rat tissues. J. Nutr. 1 17:91-98.
Donaldson, W. E., and C. McGowan. 1989. Lead toxicity in chickens. In-
teraction with toxic dietary levels of selenium. Biol. Trace Elem. Res.
20:127-133.
Echevarria, M. G., P. B. Hem-y, C. B. Ammerman, and P. V. Rao. 1988.
Effects of time and dietary selenium concentration as sodium selenite
on tissue selenium uptake by sheep. J. Anim. Sci. 66:2299-2305.
EHC 58. 1986. International Program on Chemical Safety Environ-
mental Health Criteria 58, Selenium. Online. Available at http://
www.inchem.org/documents/ehc/ehc/ehc58.htm/. Accessed July 23,
2003.
El-Begearmi, M. M., M. L. Sunde, and H. E. Ganther. 1977. A mutual
protective effect of mercury and selenium in Japanese quail. Poult. Sci.
56:313-322.
Ellis, R. G., T. H. Herdt, and H. D. Stowe. 1997. Physical, hematologic, bio-
chemical, and immunologic effects of supranutritional supplementation
with dietary selenium in Holstein cows. Am. J. Vet. Res. 58:760—764.
Elzubeir, E. A., and R. H. Davis, 1988. Effect of dietary sodium nitroprus-
side as a source of cyanide on the selenium status of chicks given diets
of varying selenium concentration. Br. Poult. Sci. 29:769—777.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
334
MINERAL TOLERANCE OF ANIMALS
Enjalbert, F., P. Lebreton, O. Salat, and F. Schelcher. 1999. Effects of pre-
or postpartum selenium supplementation on selenium status in beef cows
and their calves. J. Anim. Sci. 77:223-229.
Esaki, N., T. Nakamura, H. Tanaka, and K. Soda. 1982. Selenocysteine
lyase, a novel enzyme that specifically acts on selenocysteine. J. Biol.
Chem. 257:4386^391.
Esworthy, R. S., S. W. Binder, J. H. Doroshow, and F. F. Chu. 2003. Micro-
flora trigger colitis in mice deficient in selenium-dependent glutathione
peroxidase and induce Gpx2 gene expression. Biol. Chem. 384:597-607.
Fessler, A. J., G. Moller, P. A. Talcott, and J. H. Exon. 2003. Selenium
toxicity in sheep grazing reclaimed phosphate mining sites. Vet. Hum.
Toxicol. 45:294-298.
Fisher, D. D., S. W. Saxton, R. D. Elliott, and J. M. Beatty. 1995. Effects of
selenium sources on Se status of lactating cows. Vet. Clin. Nutr.
2(2):68-74.
Fu, Y. X., H. Sies, and X. G. Lei. 2001. Opposite roles of selenium-depen-
dent glutathione peroxidase- 1 in superoxide generator diquat- and
peroxyntrite-induced apoptosis and signaling. J. Biol. Chem.
276:43004-43009.
Ganther, H. E., and H. S. Hsieh. 1974. Mechanisms for the conversion of
selenite to selenides in mammalian tissues. Pp. 339-353 in Trace Ele-
ment Metabolism in Animals-2, W. G. Hoekstra, J. W. Suttee, H. E.
Ganther, and W. Mertz, eds. Baltimore, MD: University Park Press.
Ge, K., and G. Yang. 1993. The epidemiology of selenium deficiency in the
etiological study of endemic diseases in China. Am. J. Clin. Nutr. Suppl.
57:259S-263S.
Gladyshev, V. N., G. V. Kryukov, D. E. Fomenko, and D. L.Hatfield. 2004.
Identification of trace element-containing proteins in genomic data-
bases. Annu. Rev. Nutr. 24:579-596.
Goehring, T. B., 1. S. Palmer, O. E. Olson, G. W. Libal, and R. C.
Wahlstrom. 1984a. Effects of seleniferous grains and inorganic sele-
nium on tissue and blood composition and growth performance of rats
and swine. J. Anim. Sci. 59:725-732.
Goehring, T. B., 1. S. Palmer, O. E. Olson, G. W. Libal, and R. C.
Wahlstrom. 1984b. Toxic effects of selenium on growing swine fed
corn-soybean meal diets. J. Anim. Sci. 59:733-737.
Goldhaber, S. B. 2003. Trace element risk assessment: essentiality vs. tox-
icity. Regul. Toxicol. Pharmacol. 38:232-242.
Grace, N. D. 1994. Selenium. In Managing Trace Element Deficiencies, N.
D. Grace, ed. Palmerston North, New Zealand: New Zealand Pastoral
Agricultural Research Institute, Simon Print.
Halverson, A. W., P. L. Guss, and O. E. Olson. 1962. Effect of sulfur salts
on selenium poisoning in the rat. J. Nutr. 77:459^64.
Hamilton, S. J. 2004. Review of selenium toxicity in the aquatic food chain.
Sci. Total Environ. 326:1-31.
Hamilton, S. J., and K. J. Buhl. 1990. Acute toxicity of boron, molybde-
num, and selenium to fry of Chinook salmon and Coho salmon. Ai'ch.
Environ. Contam. Toxicol. 19:366-373.
Hasegawa, T., S. Taniguchi, M. Mihara, K. Nakamuro, and Y. Sayato. 1994.
Toxicity and chemical form of selenium in the liver of mice orally ad-
ministered selenocystine for 90 days. Arch. Toxicol. 68:91-95.
Heinz, G. H.,andD. J. Hoffman. 1996. Comparison of the effects of seleno-
L-methionine, seleno-Dl-methionine, and selenized yeast on reproduc-
tion of mallards. Environ. Pollut. 91:169-175.
Heinz, G. H., D. J. Hoffman, and L. J. LeCaptain. 1996. Toxicity of seleno-
L-methionine seleno-DL-methionine, high selenium wheat, and
selenized yeast to mallard ducklings. Aixh. Environ. Contam. Toxicol.
30:93-99.
HiU, K. E., J. Zhou, W. J. McMahan, A. K. Motley, J. F. Atkins, R. F.
Gesteland, and R. F. Burk. 2003. Deletion of selenoprotein P alters dis-
tribution of selenium in the mouse. J. Biol. Chem. 278:13640-13646.
Hintze, K. J., G. P. Lardy, M. J. Marchello, and J. W. Finley. 2002. Sele-
nium accumulation in beef: Effect of dietary selenium and geographical
area of animal origin. J. Agric. Food Chem. 50:3938-3942.
Hoffman, D. J. 2002. Role of selenium toxicity and oxidative stress in
aquatic birds. Aquat. Toxicol. 57:11-26.
Hoffman, D. J., and G. H. Heinz. 1998. Effects of mercury and selenium on
glutathione metabolism and oxidative stress in mallard ducks. Environ.
ToxicoLChem. 17:161-166.
Hsieh, H. S., and H. E. Ganther. 1977. Biosynthesis of dimethyl selenide
from sodium selenite in rat liver and kidney cell-free systems. Biochim.
Biophys. Acta 497:205-217.
lOM (Institute of Medicine). 2000. Dietary Reference Intakes for Vitamin
C, Vitamin E, Selenium, and Carotenoids. Washington, D.C.: National
Academy Press.
Ip, C. 1998. Lessons from basic research in selenium and cancer preven-
tion. J. Nutr. 128:1845-1854.
Ivancic, J., and W. P. Weiss. 2001. Effect of dietary sulfur and selenium
concentrations on selenium balance of lactating Holstein cows. J. Dairy
Sci. 84:225-232.
Jacobs, M., and C. Forst. 1981a. Toxicological effects of sodium selenite in
Sprague-Dawley rats. J. Toxicol. Environ. Health 8:575-585.
Jacobs, M., and C. Forst. 1981b. Toxicological effects of sodium selenite in
Swiss mice. J. Toxicol. Environ. Health 8:587-598.
Jacobs, K., L. Shen, H. Benemariya, and H. Deelstra. 1993. Selenium distri-
bution in egg white proteins. Z. Lebensm. Unters. Forsch. 196:236-238.
Janghorbani, M., S. Rockway, C. S. Mooers, E. M. Roberts, B. T. G. Ting,
and M. D. Sitrin. 1990. Effect of chronic selenite supplementation on
selenium excretion and organ accumulation in rats. J. Nutr. 120:274—279.
Janke, B. H. 1989. Acute selenium toxicosis in a dog. J. Am. Vet. Med.
Assoc. 195:1114-1115.
Jenkins, K. J., and M. Hidiroglou. 1986. Tolerance of the preruminant calf
for selenium in milk replacer. J. Dairy Sci. 69:1865—1870.
Jensen, L. S. 1975. Modification of a selenium toxicity in chicks by dietary
silver and copper. J. Nutr. 105:769-775.
Jensen, L. S. 1986. Effect of monensin on response of chicks to deficient
and toxic levels of dietary selenium. Poult. Sci. 65:1 163-1 166.
Jensen, L. S., and C. H. Chang. 1976. Fractionation studies on a factor in
linseed meal protecting against selenosis in chicks. Poult. Sci.
55:594-599.
Julius, A. D., M. H. Davies, and D. F. Birt. 1983. Toxic effects of dietary
selenium in the Syrian hamster. Ann. Nutr. Metab. 27:296-305.
Kappel, L. C, R. H. Ingraham, E. B. Morgan, J. M. Dixon, L. Zeringue, D.
Wilson, and D. K. Babcock. 1984. Selenium concentrations in feeds
and effects of treating pregnant Holstein cows with selenium and vita-
min E on blood selenium values and reproductive performance. Am. J.
Vet. Res. 45:691-694.
Kaur, R., S. Sharma, and S. Rampal. 2003. Effect of subchronic selenium
toxicosis on lipid peroxidation, glutathione redox cycle, and antioxidant
enzymes in calves. Vet. Hum. Toxicol. 45:190-192.
Kim, Y. Y., and D. C. Mahan. 2001a. Comparative effects of high dietary
levels of organic and inorganic selenium on selenium toxicity of
growing-finishing pigs. J. Anim. Sci. 79:942-948.
Kim, Y. Y., and D. C. Mahan. 2001b. Prolonged feeding of high dietary
levels of organic and inorganic selenium to gilts from 25 kg B W through
one parity. J. Anim. Sci. 79:956-966.
Kinder, L. L., C. R. Angel, and N. B. Anthony. 1995. Apparent selenium
toxicity in emus (Dromaius novaehollandiae). Avian Dis. 39:652—657.
Klaverkamp, J. F., W. A. Macdonald, W. R. Lillie, and A. Lutz. 1983. Joint
toxicity of mercury and selenium in salmonid eggs. Arch. Environ.
Contam. Toxicol. 12:415^19.
Knowles, S. O., N. D. Grace, K. Wurms, and J. Lee. 1999. Significance of
amount and form of dietary selenium on blood, milk, and casein sele-
nium concentrations in grazing cows. J. Dairy Sci. 82:429^37.
Kotrebai, M., M. Birringer, J. F. Tyson, E. Block, and P. C. Uden. 2000.
Selenium speciation in enriched and natural samples by HPLC-ICP-MS
and HPLC-ESl-MS with perfluorinated carboxylic acid ion-pairing
agents. Analyst 125:71-78.
Kubota, J., and W. H. AUaway. 1972. Geographic distribution of trace
element problems. Pp. 525-554 in Micronutrients in Agriculture,
J. J. Mortvedt, ed. Madison, Wl: SSSA.
Copyright © National Academy of Sciences. All rights reserved.
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inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
SELENIUM
335
Lakin, H. W. 1972. Selenium. Geol. Soc. Am. Bull. 83:181-192.
Langlands, J. P., G. E. Donald, J. E. Bowels, and A. J. Smith. 1990.
Selenium supplements for grazing sheep. 1. A comparison between
soluble salts and other forms of supplement. Anim. Feed Sci.
Technol. 28:1-13.
Latshaw, J. D. 1975. Natural and selenite selenium in the hen and egg. J.
Nutr. 105:32-37.
Latshaw, J. D., T. Y. Morishita, C. F. Sarver, and J. Thilsted. 2004. Sele-
nium toxicity in breeding ring-necked pheasants (Phasianus colchicus).
Avian Dis. 48:935-939.
Lawler, T. L., J. B. Taylor, J. W. Finley, and J. S. Canton. 2004. Effect of
supranutritional and organically bound selenium on performance, car-
cass characteristics, and selenium distribution in finishing beef steers. J.
Anim. Sci. 82:1488-1493.
Lei, X. G., D. A. Ross, J. E. Parks, and G. F. Combs, Jr. 1997a. Effects of
dietary selenium and vitamin E concentration on phospholipid hydrop-
eroxide glutathione peroxidase expression in reproductive tissues of
pubertal maturing male rats. Biol. Trace Element Res. 59:195-206.
Lei, X. G., D. A. Ross, and K. R. Roneker. 1997b. Comparison of age-
related differences in expression of phospholipid hydroperoxide glu-
tathione peroxidase mRNA and activity in various tissues of pigs. Comp.
Biochem. Physiol. 117B:109-114.
Lei, X. G., H. M. Dann, D. A. Ross, W.-H. Cheng, G. F. Combs, Jr., and K.
R. Roneker. 1998. Dietary selenium supplementation is required to sup-
port full expression of three selenium-dependent glutathione peroxi-
dases in various tissues of weanling pigs. J. Nutr. 128:130—135.
Levander, O. A. 1977. Metabolic interrelationships between arsenic and
selenium. Environ. Health Perspect. 19:159—164.
Levander, O. A. 1986. Selenium. Pp. 209-279 in Trace Elements in Hu-
mans and Animal Nutrition, 5th ed., W. Mertz, ed. Orlando, FL: Aca-
demic Press.
Lowry, K. R., and D. H. Baker. 1989. Amelioration of selenium toxicity by
arsenicals and cysteine. J. Anim. Sci. 67:959—965.
Mahan, D. C. 2000. Effect of organic and inorganic seleniumsources and
levels on sow colostrum and milk selenium content. J. Anim. Sci.
78:100-105.
Mahan, D. C, and P. L. Magee. 1991. Efficacy of dietary sodium selenite
and calcium selenite provided in the diet at approved, marginally toxic,
and toxic levels to growing swine. J. Anim. Sci. 69:4722^725.
Mahan, D. C, T. R. Cline, and B. Richert. 1999. Effects of dietary levels of
selenium-enriched yeast and sodium selenite as selenium sources fed to
growing-finishing pigs on performance, tissue selenium, serum glu-
tathione peroxidase activity, carcass characteristics, and loin quality. J.
Anim. Sci. 77:2172-2179.
Markham, G. D., E. W. Hafner, C. W. Tabor, and H. Tabor. 1980.
Adenosylmethionine synthetase from Escherichia coli. J. Biol. Chem.
255:9082-9092.
Martin, J. L., and J. A. Hurlbut. 1976. Tissue selenium levels and growth
responses of mice fed selenomethionie, Se-methylselenocysteine, or
sodium selenite. Phosphorus Sulfur Relat. Elem. 1:295—300.
Maus, R. W., F. A. Martz, R. L. Belyea, and M. F. Weiss. 1980. Relation-
ship of dietary selenium to selenium in plasma and milk from dairy
cows. J. Dairy Sci. 63:532—537.
Meads, W. J., J. Osborn, and A. B. Grant. 1980. The effect of single doses
of selenium salts on whole blood levels of selenium in ewes on a sele-
nium-deficient diet. N. Z. Vet. J. 28 (l-2):20-2.
McClung, J. P., C. A. Roneker, W. Mu, D. J. Lisk, P. Langlais, F. Liu, and
X. G. Lei. 2004. Development of insulin resistance and obesity in mice
overexpressing cellular glutathione peroxidase. Proc. Natl. Acad. Sci.
101:8852-8857.
McDowell, L. R. 2003. Minerals in Animal and Human Nutrition, 2nd ed.
Amsterdam: Elsevier.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
NRC. 1983. Selenium in Nutrition, rev. ed. Washington, D.C.: National
Academy Press.
Neathery, M. W., J. L. Varnadoe, W. J. Miller, C. T. Crowe, A. S. Fielding,
and D. M. Blackmon. 1990. Effects of high dietary lead on the metabo-
lism of intravenously dosed selenium-75 in dairy calves. J. Dairy Sci.
73:1107-1112.
Oldfield, J. E. 2003. Some recollections of early swine research with sele-
nium and vitamin E. J. Anim. Sci. 81:E145-E148.
Olson, O. E., E. J. Novcek, E. 1. Whitehead, and 1. S. Palmer. 1970. Inves-
tigation of selenium in wheat. Phytochemistry 9:1181—1188.
Olson. O. E., 1. S. Palmer., and E. E. Gary. 1975. Modification of the offi-
cial fluorometric method for selenium in plants. J. Assoc. Off. Anal.
Chem. 58:117-121.
Ort, J. F., and J. D. Latshaw. 1978. The toxic level of sodium selenite in the
diet of laying chickens. J. Nutr. 108:1114-1120.
Ortman, K., and B. Pehrson. 1999. Effect of selenate as a feed supplement
to dairy cows in comparison to selenite and selenium yeast. J. Anim.
Sci. 77:3365-3370.
Osman, M., and J. D. Latshaw. 1976. Biological potency of selenium from
sodium selenite, selenomethionine, and selenocystine in the chick. Poult.
Sci. 55:987-994.
O'Toole, D., and M. F. Raisbeck. 1995. Pathology of experimentally in-
duced chronic selenosis (alkali disease) in yearling cattle. J. Vet. Diagn.
Invest. 7:364-373.
Palmer, 1. S., O. E. Olson, A. W. Halverson, R. Miller, and C. Smith. 1980.
Isolation of factors in linseed oil meal protective against chronic seleno-
sis in rats. J. Nutr. 1 10:145-150.
Panter, K. E., L. F. James, andH. F. Mayland. 1995. Reproductive response
of ewes fed alfalfa pellets containing sodium selenate or Astragalus
bisulcatus as a selenium source. Vet. Hum. Toxicol. 37:30—32.
Panter, K. E., W. J. Hartley, L. F. James, H. F. Mayland, B. L. Stegelmeier,
and P. O. Kechele. 1996. Comparative toxicity of selenium from seleno-
DL-methionine, sodium selenate, and Astragalus bisulcatus in pigs.
Fundam. Appl. Toxicol. 32:217-223.
Parizek, J., J. Kalouskova, J. Benes, and L. Pavlik. 1980. Interactions of
selenium-mercury and selenium-selenium compounds. Ann. N.Y. Acad.
Sci. 355:347-360.
Patterson, B. H., andL. A. Zech. 1992. Development of a model for selenite
metabolism in humans. J. Nutr. 122:708-714.
Pletnikova, 1. P. 1970. Biological effect and safe concentration of selenium
in drinking water. Hyg. Sanit. 35:176-181.
Polatajko, A., M. Sliwka-Kaszynska, N. Dernovics, R. Ruzik, J. R. Encinar,
and J. Szpunar. 2004. A systematic approach to selenium speciation in
selenized yeast. J. Anal. At. Spectrom 19:114—120.
Poulsen, H. D., V. Danielsen T. K. Nielsen, and C. Wolstnip. 1989. Exces-
sive dietary selenium to primiparous sows and their offspring. 1. Influ-
ence on reproduction and growth. Acta Vet. Scand. 30:371-378.
Puis, R. 1994. Mineral Levels in Animal Health, Second Edition: Diagnos-
tic Data. Clearbrook, British Columbia, Canada: Sherpa International.
Pp. 93-109.
Rahim, A. G. A., J. R. Arthur, and C. F. Mills. 1986. Effects of dietary
copper, cadmium, iron, molybdenum, and manganese on selenium utili-
zation by the rat. J. Nutr. 1 16:403^1 1.
Raisbeck, M. F. 2000. Selenosis. Vet. Clin. North Am. Food Anim. Pract.
16:465^80.
Raisbeck, M. F., E. R. Dahl, D. A. Sanchez, E. L. Belden, and D. O'Toole.
1993. Naturally occurring selenosis in Wyoming. J. Vet. Diagn. Invest.
51:84-87.
Read, R., T. Bellew, J. G. Yang, K. E. Hill, 1. S. Palmer, and R. F.
Burk. 1990. Selenium and amino acid composition of selenoprotein
P, the major selenoprotein in rat serum. J. Biol. Chem. 265:17899-
17905.
Rogers, P. A. M., S. P. Arora, G. A. Fleming, R. A. P. Crinion, and J. G.
McLaughlin. 1990. Selenium toxicity in farm animals: treatment and
prevention. Irish Vet. J. 43:151-153.
Rotruck, J. T., A. L. Pope, H. E. Ganther, A. B. Swanson, D. G. Hafeman,
and W. G. Hoekstra. 1973. Selenium: biochemical role as a component
of glutathione peroxidase. Science 179:588-590.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
336
MINERAL TOLERANCE OF ANIMALS
Salbe, A. D., and O. A. Levander. 1990. Effect of various dietary
factors on tlie deposition of selenium in the hair and nails of rats. J.
Nutr. 120:200-206.
Spallholz, J. E., and D. J. Hoffman. 2002. Selenium toxicity: cause and
effects in aquatic birds. Aquat. Toxicol. 57:21-37.
Spears, J. W. 2003. Trace mineral bioavailability in ruminants. J. Nutr.
133:1506S-1509S.
Stowe, H. D., and T. H. Herdt. 1992. Clinical assessment of selenium status
of livestock. J. Anim. Sci. 70:3928-3933.
Sun, S., F. Zhai, L. Zhou, and G. Yang. 1985. The bioavailabihty of soil
selenium in Keshan disease and high selenium areas. Chin. J. End. Dis.
4:21-28.
Sunde, R. A. 1997. Selenium. Pp. 493-556 in Handbooii of Nutritionally
Essential Mineral Elements, B. L. O'Dell and R. A. Sunde, eds. New
York: Marcel Dekker.
Szeleszczuk, P., E. Karpinska, W. Bielecki, G. Koroaska, and W.
Borzemska. 2004. Evaluation of lithium and selenium toxicity for
chicken embryos and one-day-old chicks. Medycyna-Weterynaryjna
60:492-295.
Thompson, C. D., M. F. Robinson, D. R. Campbell, and H. M. Rea. 1982.
Effect of prolonged supplementation with daily supplements of
selenomethionine and sodium selenite on glutathione peroxidase activ-
ity in blood of New Zealand residents. Am. J. Clin. Nutr. 36:24—31.
Tinggi, U. 2003. Essentiality and toxicity of selenium and its status in Aus-
tralia: a review. Toxicol. Lett. 137:103-10.
Tsunoda, M., V. J. Johnson and R. P. Sharma. 2000. Increase in dopamine
metabolites in murine striatum after oral exposure to inorganic but not
organic form of selenium. Ai'ch. Environ. Contam. Toxicol. 39:32-37.
Ullrey, D. E. 1992. Basis for regulation of selenium supplements in animal
diets. J. Anim. Sci. 70:3922-3927.
Ullrey, D. E., P. S. Brady, P. A. Whetter, P. K. Ku, and W. T. Magee. 1977.
Selenium supplementation of diets for sheep and beef cattle. J. Anim.
Sci. 45:559.
Underwood, E. J., and N. F. Suttle, 1999. The Mineral Nutrition of Live-
stock, 3rd ed. New York: CABl Publishing.
Urano, T., N. Imura, and A. Naganuma. 1997. Inhibitory effect of selenium
on biliary secretion of methyl mercury in rats. Biochem. Biophys. Res.
Comm. 239:862-867.
Vanderkop, P. A., and J. D. MacNeil. 1990. The effect of sodium selenite
supplementation on monensin-induced growth inhibition and residue
accumulation in broiler chicks. Vet. Hum. Toxicol. 32:1-5.
van der Linden, R., F. De Corte, and J. Hoste. 1974. Activation analysis of
biological material with ruthenium as a multi-element comparator. Anal.
Chim. Acta 71:263-275.
van Saun, R. J., T. H. Herdt, and H. D. Stowe. 1989. Maternal and fetal
selenium concentrations and their interrelationships in dairy cattle. J.
Nutr. 119:1128-1137.
Vendeland, S. C, J. A. Butler, and P. D. Whanger. 1992. Intestinal absorp-
tion of selenite, selenate, and selenomethionine in the rat. J. Nutr.
Biochem. 3:359-365.
Vernie, L. N., H. B. Ginjarr, 1. T. Wilders, and W. S. Bont. 1978. Amino
acid incorporation in a cell-free system derived from rat liver studied
with the aid of selenodiglutathione. Biochim. Biophys. Acta
518(3):507-517.
Waschuleswski, 1. H., and R. A. Sunde. 1988. Effect of dietary methionine
on utilization of tissue selenium from dietary selenomethionine for glu-
tathione peroxidase in the rat. J. Nutr. 1 18:367-374.
Wedekind, K. J., R. Beyer, and G. F. Combs, Jr. 1998. Is selenium addition
necessary in pet foods? FASEB J. 1 1 :A360.
Wedekind, K. J., S. Yu, and G. F. Combs, Jr. 2004. The selenium require-
ment of the puppy. J. Anim. Physiol. Anim. Nutr. 88:340-347.
White, C. L., T. K. Cadwalader, G. W. Hoekstra, and A. L. Pope. 1989. The
metabolism of ''Se— selenomethionine in sheep given supplementary
copper and molybdenum. J. Anim. Sci. 67:2400-2408.
Windisch. W., and M. Kirchgessner. 2000a. P. 173 in Trace Elements in
Man and Animals-10, P. W. Fisher, M. R Labbe, K. A. Cockell, and R.
S. Gibson, eds. New York: Kluwer Academic/Plenum Publishers.
Windisch, W., and M. Kirchgessner. 2000b. P. 883 in Trace Elements in
Man and Animals-10, P. W. Fisher, M. R Labbe, K. A. Cockell, and R.
S. Gibson, eds. New York: Kluwer Academic/Plenum Publishers.
Witte, S. T., and L. A. Will. 1993. Investigation of selenium sources associ-
ated with chronic selenosis in horses of western Iowa. J. Vet. Diagn.
Invest. 5:128-131.
Wolffram, S., E. Anliker, and E. Scharrer. 1986. Uptake of selenate and
selenite by isolated brush border membrane vesicles from pig, sheep,
and rat intestine. Biol. Trace Elem. Res. 10:293-306.
Wolffram, S., B. Grenacher, and E. Scharrer. 1988. Transport of selenate
and sulphate across the intestinal brush border membrane of pig je-
junum by two common mechanisms. Q. J. Exp. Physiol. 73:103—111.
Wright, P. L., and M. C. Bell. 1966. Comparative metabolism of selenium
and tellurium in sheep and swine. Am. J. Physiol. 211 :6— 10.
Xia, Y., J. Buuler, M. Janhorbani, P. Ha, P. Whanger, J. Olesik, and L.
Daniels. 2000. P. 175 in Trace Elements in Man and Animals-10. P. W.
Fisher, M. R. Labbe, K. A. Cockell, and R. S. Gibson, eds. New York:
Kluwer Academic/Plenum Publishers.
Yang, G., and R. Zhou. 1994. Further observances on the human maximum
safe dietary selenium intake in a seleniferous area of China. J. Trace
Elem. Electrol. Health Dis. 8:159-165.
Zachara, B. A., V. Frafikowska, H. Lejman, C. Kimber, and M. Kaptur.
1993. Selenium and glutathione peroxidase in blood of lambs born to
ewes injected with barium selenate. Small Ruminant Res. 1 1:135-141.
Zayed, A., C. M. Lytle, and N. Terry. 1998. Accumulation and volatil-
ization of different chemical species of selenium by plants. Planta
206:284-292.
Copyright © National Academy of Sciences. All rights reserved.
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344
MINERAL TOLERANCE OF ANIMALS
TABLE 25-2 Selenium Concentrations in Fluids and Tissues of Animals
Animals
Quantity
Source
Whole
Blood (B),
Plasma (P),
Hoof or
or Serum
Milk,
Nail,
(S), mg/L
lig/L
mg/kg
Female
0.5 mg Se/L in water
Sodium selenite
rhesus
0.5 mg Se/L in water
Selenomethionine
monkeys (6 kg.
3 year old) for
11- mo trial" ^^
^1 ^^^^^B
^^B
Rats,
Basal diet (0.25 mg Se/kg)
Sodium selenite
0.56 (P)
adult
Basal + water (4 mg/L)
Sodium selenite
0.68 (P)
Sprague-
Dawley
(268-332 g)
Rats, ^™
^^ 0.5 mg Se/kg ^^^^^^^^^^V
Sodium selenite ^^^^V
0.35 (P)
weanling male
mg Se/kg ^^^^^^^H
Selenomethionine ^^^H
0.40 (P)
Sprague- ^_
^— 1.5 mg Se/kg ^^^^^^^^|
Sodium selenite ^^^H
0.37 (P)
Dawley rats ^|
^M mg Se/kg ^^^^^^^^^1
Selenomethionine ^^^H
0.50 (P)
for 8 week ^|
^M mg Se/kg ^^^^^^^^^1
Sodium selenite ^^^H
0.40 (P)
trial" ^
2.5 mg Se/kg ^^^^^^^^|
Selenomethionine
0.63 (P)
Syrian
0.25 mg Se/kg diet
Sodium selenite
0.17 (B)
hamsters.
10 mg Se/kg diet
Sodium selenite
0.49 (B)
4 wk old
20 mg Se/kg diet
Sodium selenite
0.78 (B)
for 21-d
40 mg Se/kg diet
Sodium selenite
1.11(B)
trial"
80 mg Se/kg diet
Sodium selenite
2.35 (B)
Male chicks.
Corn- soy basal diet
8 d old for
-h 15 mg Se/kg
Sodium selenite ^^^^h
14 d
-h 15 mg Se/kg
Selenomethionine
Chicks,
Corn-torula yeast basal diet, 0.03 mg Se/kg
4 wk old
+ 0.06 mg Se/kg
Sodium selenite
-H 0.06 mg Se/kg
Selenomethionine
-H 0.06 mg Se/kg
Selenocysteine
Laying hens
Corn-soy basal, 0.10 mg Se/kg
-H 0.32 mg Se/kg
Sodium selenite
^^^^H
^H Corn-soy basal, 0.42 mg Se/kg ^^^^^|
Turkeys,
Practical diets, 0.13-0.20 mg Se/kg
0.19 (P)
14-20
-H 0.10 mg Se/kg
Sodium selenite
0.19 (P)
wk old"
-H 0.20 mg Se/kg
Sodium selenite
0.20 (P)
Young pigs.
Control, 0.4 mg Se/kg diet
0.3 (B)
8-10 wk old
25 mg Se/kg
Seleno-DL-methionine
5.6 (B)
for 6-wk
25 mg Se/kg
Astragalus bisulcatus
2.0 (B)
experiment"
25 mg Se/kg
Sodium selenate
2.4 (B)
Growing
Basal
0.11 (P)
crossbreed
5 mg Se/kg
Sodium selenite
0.66 (P)
pigs (25 kg )
10 mg Se/kg
Sodium selenite
I. 10 (P)
for 12 wk«
15 mg Se/kg
Sodium selenite
1.89 (P)
20 mg Se/kg
Sodium selenite
1.88 (P)
5 mg Se/kg
Selenized yeast
0.78 (P)
10 mg Se/kg
Selenized yeast
1.67 (P)
15 mg Se/kg
Selenized yeast
2.49 (P)
20 mg Se/kg
Selenized yeast
3.23 (P)
0.41"
1.26"
4.89
12.64"
5.99"
9.01"
15.99"
28.86"
18.46"
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SELENIUM
345
Hair,
mg/kg
Kidney,
mg/kg
Liver,
mg/kg
Muscle,
mg/kg
Spleen,
mg/kg
Reference
0.60°
4.20°
0.24°
0.70°
0.06"
0.68"
Butler et al.,
1990
1.23
2.85
0.68
1.61
0.13
0.18
Janghorbani et al., 1990
^^^B 0.38" ^^^H
^^^V
^^^H
^^^^^^^V Salbe ^^^^^^^^^^^^^^^^^^^^^^^1
^^H 1.23" ^^^1
^^H
^^^H
^^^^^V ^^^^^^^^^^^^^^^H
^^^1 ^^^1
^^H
^^^H
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^1 ^^^H
^^^H
^^^H
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^1
^^^1 ^^^H
^^^1
^^^H
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^1
^^^H ^^^"
^^^" 2.30"
^^^^^
^^^^^^^^^^^^^^^^^^^^^^^^^1
0.60"
0.50"
0.26"
1.46"
1.56"
.024"
1.88"
5.36"
0.31"
3.18"
7.22"
0.46"
5.41"
10.10"
0.60"
0.7-2.0
14.0-19.0
53.2
0.18
0.15
0.05
1.33
0.78
0.14
1.18
0.68
0.19
1.45
0.77
0.13
0.66"
0.20"
0.66"
0.20"
0.66"
0.20"
Julius et al., 1983
Lowry and
Baker, 1989
Osman and
Latshaw, 1976
0.32
0.43
0.33
Latshaw, 1975
0.74
0.82
0.42
■
^^^^^^^^^^H
1.92
^^^H
Cantor and
Scott, 1975
7.2"
2.3"
2.1"
Panter et al.,
1996
1
118.3"
64.6"
75.9"
16.6"
12.4"
4.9"
J
20.1"
12.9"
7.1"
J
1.66"
0.40"
0.15"
0.24"
3.11"
3.09"
0.33"
0.81"
6.67"
6.40"
0.28"
1.28"
8.78"
7.12"
0.32"
1.47"
8.57"
8.41"
0.32"
1.89"
5.30"
5.59"
3.38"
2.41"
9.71"
11.57"
5.93"
4.89"
13.77"
17.47"
10.31"
7.24"
16.29"
17.69"
7.65"
8.31"
Kim and Mahan, 2001a
continued
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346
MINERAL TOLERANCE OF ANIMALS
TABLE 25-2 Continued
Animals
Crossbred
steers (351 kg
BW) for 120-d
feeding
Adult
Holstein cows
for 90-136 d
(396-772 kg)
Holstein cows
Calves,
8 mo old"
Yearling
ewes (50-80
kg) for 88-d
trial
Quantity
Source
Whole
Blood (B),
Plasma (P),
Hoof or
or Serum
Milk,
Nail,
(S), mg/L
mg/L
mg/kg
Gilts, from
0.3 mg Se/kg
Sodium selenite
0.19 (S)
40
0.27°
25 kg to first
3.0 mg Se/kg
Sodium selenite
0.38 (S)
170
0.50"
parity"
7.0 mg Se/kg
Sodium selenite
0.65 (S)
180
1.42°
10.0 mg Se/kg
Sodium selenite
0.82 (S)
760
2.00"
0.3 mg Se/kg
Selenized yeast
0.20 (S)
90
0.84"
3.0 mg Se/kg
Selenized yeast
0.50 (S)
650
3.61"
7.0 mg Se/kg
Selenized yeast
1.37 (S)
1,610
16.17"
^^H
^H 10.0 mg Se/kg ^^^^^m
^^^^^^H Selenized yeast H
^^ 1.74 (S)
4,140
12.27" ^^^^^H
9.5 Mg/kg BW
65.0 ng/kg BW
65.0 ng/kg BW
65.0 ng/kg BW
Sodium selenite
High Se hay
High Se wheat
374-kg
Animals from seleniferos area ^^H
1
^^^^^^^^^^^^M
Yearling
0.62 mg Se/kg diet ^H
■ Control
(P) ^^^^^^^^^^^^^^^1
steers from
1 1.9 mg Se/kg diet ^H
1 High Se hay
(P) ^^^^^^^^^^^^^H
seleniferous
Animals from non-seleniferos area
__^^^^^^^^^^^^^^^^^
or non-
0.62 mg Se/kg diet
Control
^^^^^^^^^^^^^1
seleniferous
1 1.9 mg Se/kg diet ^^^^^^^^
_ High Se wheat/hay
^^^^^^^^^^^^^^^1
areas for 105-d
^^^^^^^^
m
^^^^^^^^^^^^^^^^^^
feeding trial
^^^^^^^^^^^^^1
mg Se/cow/d
3 mg Se/cow/d (5.3 ^ig/kg BW)
20 mg Se/cow/d (34.5 |jg/kg BW)
50-100 mg Se/cow/d (86.9 ng/kg BW)
Sodium selenite
Sodium selenite
Sodium selenite
0.05 (S)
0.06 (S)
0.075 (S)
0.10-0.25 (S)
Holstein cows ^^|
^P Control ^^^^^^^1
^^^^^^^■^^^^H
^P 0.11(B)
^^^^^^^^^^H
60 d prepartum
+ 3 mg Se/cow/d ^^^^|
^ Sodium selenite ^
H 0.13(B)
(colostrum) ^^^^^^^^^^^|
for 120 d
^^
^^^
^^^^^^
0. 1 mg Se/kg DM
0.1 mg Se/kg DM
Sodium selenite
Se-yeast
0.16(B)
0.15(B)
18
21
Primiparous
Basal (0.11 mg Se/kg DM)
0.10 (B)
^^^^^^^^H
Swedish red
+ 3 mg Se/cow/d (0.28 mg Se/kg DM)
Sodium selenite
0.14(B)
^^^^^^^^^^^H
and white
+ 3 mg Se/cow/d (0.28 mg Se/kg DM)
Sodium selenate
0.14(B)
^^^^^^^^^^^H
cows
+ 3 mg Se/cow/d (0.28 mg Se/kg DM)
Se-yeast
0.17 (B)
^^^^^^^^^^^H
Roughage and concentrate
+ 0.1 mg Se/kg
+ 0.2 mg Se/kg
Sodium selenite
Sodium selenite
0.021 (P)
0.022 (P)
0.024 (P)
Holstein calves,
Basal, 0.2 mg Se/kg ^^M
^^H
0.08 (B)
3 d old for
1 mg Se/kg ^^H
^^^^V Sodium selenite
0.10 (B)
6- to 8-wk
mg Se/kg ^^^^^^1
^^^^1 Sodium selenite
0.19(B)
experiment
mg Se/kg ^^^^^1
^^^^1 Sodium selenite
0.26 (B)
10-40 mg Se/kg ^^^^^H
^^^^B Sodium selenite
0.24-2.08 (B)
Control, 0.8 mg Se/kg (in alfalfa)
24 mg Se/kg
29 mg Se/kg
Sodium selenite
Astragalus bisculcatus
0.45 (B)
2.4 (B)
1.3 (B)
Lambs, ^^H
^^^B Complete roughage and grain, 0.06 mg Se/kg
0.032 (P) ^^^^^^^^^^^^^^^^1
46 kg" ^1
^^H + 30 mg Se/kg in salts
^^^1 Complete roughage and grain
Sodium selenite ^B
(P) ^^^^^^^^^^^^^^^H
^^^^^^^^1
^^H + 0.20 mg Se/kg
Sodium selenite ^H
^^^^^^^^^^^^^^^^^1
^^^^^^^^1
^^H + 0.20 mg Se/kg
Organic form of Se
(P) ^^^^^^^^^^^^^^^^^P
^^^^^^^^^
^^^ + 0.30 mg Se/kg
Sodium selenite
(P) ^^^^^^^^^^^^^^^^^^
+ 0.30 mg Se/kg
Organic form of Se
0.16 (P)
"Fresh (wet) tissue basis.
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SELENIUM
347
Hair,
mg/kg
Kidney,
Liver,
mg/kg
Muscle,
mg/kg
Spleen,
mg/kg
Reference
0.49°
2.14°
0.58°
0.15°
0.34°
Kim and Mahan, 2001b
1.38°
2.56°
2.11°
0.17°
0.66°
2.15°
3.99°
3.60°
0.24"
0.92°
2.83°
4.42°
3.43°
0.23"
1.62°
0.86°
2.49°
0.75°
0.28"
0.42°
5.12°
4.99°
2.77°
1.69"
1.59°
7.96°
8.69°
7.16°
4.14"
4.22°
^^^H
9.29°
8.93°
5.33"
5.20° H
1.80
8.4
2.33
1.33
2.00
4.00
10.05
9.91
1.55
2.60
5.93
10.86
6.56
3.32
3.82
10.54
12.89
10.79
4.41
5.16
Lawler et al., 2004
^^^^^
et ^^^^^^^^^^^^^^^V
^^^^^^p
0.97
1.20
^^^^^^^^^^^^^^^K
^
4.69
2.09
^^^^^^^Bl
H^
0.89
0.40
^^^^^^^H
^v
5.94
1.56
^^H
-1.2
-1.4
-4.3
-6.5-15.0
Ellis et al., 1997
Abdelrahman and
Kincaid, 1995
Fisher et al., 1995
1.01"
0.09°
0.03"
1.22"
0.11°
0.04"
1.29"
0.11°
0.04"
2.93
1.09
0.27
3.08
3.43
0.32
3.42
4.74
0.034
4.02
9.90
0.59
5-32
28-188
0.6-1.1
Ammerman et al., 1980
Panter et al., 1995
0.99"
0.19°
0.06"
1.24"
0.27°
0.07"
1.26"
0.38°
0.09"
1.30"
0.62°
0.17"
1.22"
0.53°
0.11"
1.35"
0.66°
0.16"
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26
Silicon
INTRODUCTION
Silicon (Si) in its elemental form is a shiny metallic-look-
ing substance that is hard and brittle with a crystalline struc-
ture similar to that of diamond. Silicon is the second most
abundant element in the Earth's crust; 27.7 percent of the
lithosphere is silicon. It occurs in nature mostly in the oxide
and silicate form. Silicon dioxide (SiOj) occurs mainly in
the crystalline form as quartz or sand. Asbestos, feldspars,
clays, and micas are examples of silicate minerals.
Silicon is prepared commercially by heating silica and
carbon to 1,600 °-l,800°C in an electric furnace (Hunter and
Aberg, 1975). At this temperature carbon takes oxygen from
silica to form carbon monoxide. Whereas silica is the term
often used for naturally occurring substances composed
mainly of silicon dioxide, silicone (organosiloxane) is the
term used for synthetic polymers with a structure of alternat-
ing oxygen and silicon atoms (Hunter and Aberg, 1975).
Adding water to silicates liberates orthosilicic acid, which
apparently is an important biological form of silicon.
Orthosilicic acid (Si(OH)4), also known as monosilicic acid
or monomeric silica, polymerizes in neutral solutions at con-
centrations greater than 2 mmol/L. Some lower forms of life
and plants may use this reaction to form polymeric silica, or
phytolithic silica, for structure and growth. In higher ani-
mals and humans, monosilicic acid is thought to be a circu-
lating form of silicon. Precipitated silica, or colloidal silicic
acid (approximate formula of HjSiOj), is an insoluble form
of silicon and occurs in nature as opal. The condensation of
orthosilicic acid to form precipitated silica is a method for
making silica gel, an adsorbent.
Silicon is tetravalent and has a strong affinity for oxygen.
The chemistry of silicon is similar to that of carbon, its sister
element (Wannagat, 1978). Silicon forms silicon-silicon, sili-
con-hydrogen, silicon-oxygen, silicon-nitrogen, and silicon-
carbon bonds. Thus, organosilicon compounds are analogues
of organocarbon compounds. However, the substitution of
silicon for carbon, or vice versa, in organocompounds re-
sults in molecules with different properties because silicon
is larger and less electronegative than carbon. A review of
the aqueous chemistry of silicon shows that it is quite com-
plex (Knight and Kinrade, 2001).
Elemental silicon is used as a processing aid in the
manufacture of aluminum, aluminum alloys, iron and steel,
and as the basic raw material to synthesize silicones
(Corathers, 2002). The semiconductor industry, which
manufactures chips for computers from high-purity silicon,
accounts for only a small percentage of silicon use
(Corathers, 2002). Silicon is a major component of ceram-
ics, building materials, and glasses. Amorphous silica is
used extensively in the food and pharmaceutical industries.
It is used as an anti-caking agent for dry powders, a disper-
sion agent for dry powders in liquids to prevent clumping,
an anti-settling or suspending agent, a stabilizer in oil-wa-
ter emulsions, a thickening or thixotropic agent (viscosity
control/dough modifier), a gelling agent, a flavor carrier,
an extrusion aid, a clarification and separation aid, a gen-
eral excipient (pharmaceuticals and cosmetics), and a sup-
port matrix for immobilization of enzymes (Villota and
Hawkes, 1986). Colloidal silicic acid is used in beauty
products, and in acne and gastritis medications.
ESSENTIALITY
Silicon is nutritionally essential for some lower forms
of life (Carlisle, 1984). Silicon has a structural role in dia-
toms, radiolarians, and some sponges. It may be essential
for some higher plants (e.g., rice). Diatoms, which are uni-
cellular microscopic plants, have an absolute requirement
for silicon as monomeric silicic acid for normal cell growth.
The diatom, Cylindrotheca fusiformis, has five silicon
transporter genes that tightly control silicon uptake and use
in cell wall formation (Hildebrand et al., 1998). Findings
from experiments comparing low intakes (<2.0 mg/kg diet)
with physiological intakes (4.5-35 mg/kg diet) suggest that
silicon has an essential role in collagen and glycosami-
348
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SILICON
349
noglycan formation or function, and thus influences bone
formation, wound iiealing, and ectopic calcification in rats
(Seaborn and Nielsen, 1993, 2002c). However, silicon is
generally not accepted as an essential nutrient for higher
animals, apparently because of the lack of a clearly defined
specific biochemical function.
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
The colorimetric determination of silicate using the am-
monium molybdate reaction is quite sensitive but is prone to
forming molybdenum blue (the final product of the colori-
metric assay) in the presence of substances other than the
yellow ammonium molybdate silicate complex (Schwarz,
1978). Thus, analytical techniques using inductively coupled
plasma-atomic emission spectrometry (ICP-AES), direct
current plasma atomic emission spectrometry (DCP-AES),
or electrothermal atomic absorption spectrometry (ETAAS)
have become methods generally used for the determination
of silicon in biological and clinical samples (Klemens and
Heumann, 2001). Recently, an inductively-coupled plasma-
high resolution isotope dilution mass spectrometric (ICP-
HRIDMS) method (Klemens and Heuman, 2001) was de-
veloped that may give more accurate determinations of
silicon than in the past. Because the isotope-dilution step is
performed during microwave-assisted sample decomposition
in a closed system, loss of analyte after opening the diges-
tion vessel has no effect on the analytical result (unlike other
analytical methods).
Regardless of the instrumentation used, a major prob-
lem in silicon analysis is the high risk of contamination
because of its ubiquity. This is probably the reason that
more modern techniques and instrumentation indicate that
silicon concentrations reported in the older biological and
food composition literature often are too high. The use of
clean room techniques to avoid dust, avoiding contact
with glass, and use of water and reagents purified to re-
move silicon (Klemens and Heumann, 2001) are practices
that help reduce contamination of samples to be analyzed.
The digestion of biological samples to solubilize silicon
is also a demanding task because of the low solubility of
silica in acid media. Two methods that can be used are
digesting with an acid mixture containing hydrofluoric
acid or with an alkaline medium (Van Dyck et al., 1998;
Hauptkorn et al., 2001). The hydrofluoric acid method is
hazardous and care must be taken to prevent the etching
of glassware (containing silicon). Currently, the most ac-
ceptable method is a nonoxidative alkaline digestion pro-
cedure using tetramethylammonium hydroxide and a
high-pressure, microwave-assisted autoclave digestion
system (Hauptkorn et al., 2001). Because of concerns
about contamination and inadequate digestion, the valid-
ity of any silicon analysis can only be assured by the use
of quality control procedures.
REGULATION AND METABOLISM
Absorption and Metabolism
A study with guinea pigs indicated that silicon is absorbed
mainly as monomeric silicic acid (Sauer et al., 1959). In hu-
mans, monosilicic acid in foods and beverages is readily ab-
sorbed and excreted in urine (Baumann, 1960). Some of the
absorbed monosilicic acid can come from food polymeric
silica, which can be partly dissolved by fluids of the gas-
trointestinal tract. The mechanisms involved in the intestinal
absorption and blood transport of silicon are unknown. Sili-
con is not bound to protein in plasma, where it is believed to
exist almost entirely as undissociated monomeric silicic acid
(Carlisle, 1984; Berlyne et al., 1986). Connective tissues, in-
cluding aorta, bone, skin (and its appendages), tendon, and
trachea, contain much of the silicon that is retained in the body
(Carlisle, 1984; Adler et al., 1986), where it is thought to be
present as a silanolate, an ether or ester derivative of silicic
acid (Schwarz, 1974). Absorbed silicon is mainly eliminated
via the urine, where it probably exists as orthosilicic acid and/
or magnesium orthosilicate (Carlisle, 1984; Berlyne et al.,
1986). The upper limits of urinary excretion apparently are set
by the rate and extent of silicon absorption and not by the
excretory ability of the kidney because peritoneal injection of
silicon can elevate urinary excretion above the upper limit
achieved by dietary intake (Sauer et al., 1959). The form of
dietary silicon determines whether it is well absorbed. For
example, humans absorbed only ~1 percent of a large dose of
an aluminosilicate compound but absorbed >70 percent of a
single dose of methylsilanetriol salicylate, a drug developed
for the treatment of circulatory ischemia (Allain et al., 1983).
The amount in the diet also affects silicon absorption. In rats,
guinea pigs, cattle, and sheep, urinary excretion of silicon in-
creases with an increasing intake of siliceous substances, but
reaches a maximum that is not exceeded by increasing the
intake (Bailey, 1981). For example, in sheep, the amount of
silicon increased in urine as dietary silica increased from 0.10
to 2.84 percent, but reached a maximum of 250 mg of silica
per day, which was less than 4 percent of the total intake (Jones
and Handreck, 1965). Similar results were found in another
study with sheep where only 0.8 percent of silica was absorbed
from a diet supplying 20 grams per day (Bailey, 1981). These
studies indicated that <1 percent of the silicon in diets that
predispose to the formation of calculi in cattle and sheep is
excreted in the urine. It has been suggested that the maximum
urinary output of monosilicic acid is attained in ruminants
when enough soluble silicon is ingested to saturate the
reticulo-rumen fluid with monosilicic acid (Jones and
Handreck, 1965).
IVIetabolic Interactions and IVIechanisms of Toxicity
Ingested silicon has a relatively low order of toxicity. The
most common pathological condition that may occur with a
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MINERAL TOLERANCE OF ANIMALS
high intake of silicon is urolithiasis (Bailey, 1981). A low
output of water in urine relative to the output of orthosilicic
acid, resulting in high urinary concentration or supersatura-
tion of orthosilicic acid, apparently is a necessary condition
for calculus formation. The formation of calculi is promoted
by other urine properties, including a high pH (Schreier and
Emerick, 1986; Emerick and Lu, 1987) and the presence of
specific proteins (Bailey, 1981). In addition to urolithiasis, a
high intake of silicon might interfere with the absorption or
use of some essential nutrients, particularly zinc. An antago-
nism between zinc and silicon explains why dietary silicon
decreases the zinc concentration in plasma and tissues of rats
(Emerick and Kayongo-Male, 1990; Najda et al., 1992). In
contrast to zinc, copper use or absorption apparently is en-
hanced by high dietary silicon in rats and turkeys (Emerick
and Kayongo-Male, 1990; Najda etal., 1992; Kayongo-Male
and Palmer, 1998). Also, relatively high dietary silicon (600
mg/kg) was protective against aluminum neurotoxicity char-
acterized by depressed zinc and increased aluminum con-
centrations in brain that were apparently exacerbated by sili-
con deprivation (Carlisle and Curran, 1987; Carlisle et al.,
1991).
SOURCES AND BIOAVAILABILITY
Forages and cereal grains high in fiber (e.g., oats and bar-
ley) are the major sources of silicon for animals (Bailey,
1981; Bowen and Peggs, 1984; Pennington, 1991). Silicon,
present in plants as silica and soluble silicates, and in or-
ganic combinations, is bound to the cellulosic cell structure
(Bailey, 1981). Hydrated silica known as opaline silica or
silica gel is commonly deposited in plants in the form of
particles called phytoliths. Each plant has a characteristic
phytolith shape and these shapes vary enonnously between
plants (Carlisle, 1984). Soil type, plant species, transpiration
rate, and nutrient supply affect the silica content of plants.
Contamination of feeds, especially hay and pasture herbage,
with soil elevates their content of silicon. The amount of
silicon provided by the diet in areas where urolithiasis is a
problem for ruminants can be extremely high (Bailey, 1981).
The graminous species that constitute the main diet of af-
flicted animals contain high amounts of silica (up to 6 per-
cent) DW. It has been estimated that yearling steers weigh-
ing 300 kg consuming native range hay or grass in the
semi-arid Northern Great Plains of North America would
consume about 500 g of silica per day. Sheep on common
diets in Australia consume up to 20 g of silica per day and,
when grazing on native grass, might consume as much as
40 g per day. Natural waters apparently are not a major
source of silicon because they contain only 0.8-44 mg/L
(Farmer, 1986). Other sources of silicon in animal feeds are
grit added to some poultry diets, and sand added to some
feeds as a "bulking" agent.
Early balance studies in animals indicated that almost all
ingested silicon is unabsorbed. As indicated above; the low
absorption probably was the result of intakes of silicon that
exceeded the amount needed to achieve maximal absorp-
tion. Thus, these studies do not indicate the bioavailability
of silicon when consumed in low or milligram quantities
from various foods and feeds. A recent study with humans
consuming diets providing about 30 mg of silicon per day
indicated that a substantial amount of food silicon is ab-
sorbed. Jugdaohsingh et al. (2002) found that an average of
41 percent of dietary silicon was excreted in the urine (an
indicator of absorption). Silicon in grains and grain products
was readily absorbed, as indicated by a mean urinary excre-
tion of 49 ± 34 percent of intake. In several of the grain
products, silicon was as available as it was from fluids. For
example, urinary silicon excretion was 41-86 percent from
corn flakes, white rice, and brown rice, and 50-86 percent
from mineral waters. Silicon in fruits and vegetables, except
green beans and raisins, was readily absorbed, with mean
urinary excretion 21 ± 29 percent of intake.
Additives in prepared feeds, foods, confections, and phar-
maceuticals are another source of oral silicon. Amorphous
silicates are considered safe additions to foods. Their use as
anti-caking agents, for example, is permitted in amounts up
to 2 percent by weight. A GRAS (Generally Recognized As
Safe) committee concluded that silicates added to foods to
enhance their physical properties are relatively inert and thus
not bioavailable. Sodium zeolite A, a hydrated aluminosili-
cate that breaks down into monosilicic acid and aluminum in
the gut (Benke and Osborn, 1979), has been used as a dietary
supplement to increase chicken eggshell thickness (Roland,
1988), prevent parturient paresis in dairy cows (Thilsing-
Hansen and Jorgensen, 2001), and decrease bone-related in-
juries in horses (Frey et al., 1992; Nielsen et al., 1993). The
mean absorption of silicon from Zeolite A administered
orally to dogs as a capsule, solution, or suspension was re-
ported to be 2.33, 3.44, and 2.74 percent, respectively (Cefali
et al., 1996).
TOXICOSIS
The toxic effect of high silica exposure through inhala-
tion or injection, which can cause lung and renal damage, is
not relevant to the mission of this document and thus will not
be presented. Also, unlike the predecessor of this document
(NRC, 1980), this review will not tabulate studies that show
relatively high amounts of orally ingested silicon (generally
between 250 and 500 mg/kg diet) as having no or beneficial
effects. Examples of beneficial effects include prevention of
aluminum toxicity to fish by silicic acid addition to water
(Birchall et al., 1989) and improvement of growth, reduction
of rachitic lesions, and enhancement of bone strength in cal-
cium-deficient chicks by 0.75 percent and 1.5 percent di-
etary zeolite (Leach et al., 1990; Watkins and Southern,
1991). This contrasts with the exacerbation by 0.5-1.0 per-
cent dietary zeolite of signs of phosphorus deficiency, in-
cluding decreased feed efficiency, tibial ash, egg produc-
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SILICON
351
tion, and egg weight; zeolite did not affect these variables
when dietary phosphorus was adequate (Roland, 1990;
Moshtaghian et al., 1991). It is unclear whether the primary
interaction is between phosphorus and silicon or phosphorus
and aluminum. Although not a true toxicity action, a detri-
mental effect of silicon for ruminants is that it depresses DM
digestibility of forages (Van Soest and Jones, 1968). Most
silicon compounds are essentially nontoxic to humans when
taken orally. Magnesium trisilicate, an over-the-counter ant-
acid, has been used by humans for more than 40 years with
only minimal apparent deleterious effects reported. Carlisle
(1984) stated in a review that, as of 1964, only nine cases of
urinary calculi containing silicon and associated with high
and long-term use of magnesium silicate had been recorded.
Acute
The acute toxicity of silicon (as silica) is low. No signifi-
cant acute toxicity or mortality has been reported in animals
given doses of up to 3,000 mg/kg BW per day. An oral dose
of 3 g of sand given to Leghorn cockerels did not affect true
metabolizable energy of a laying hen diet or corn (Sibbald,
1980). Various handbooks have reported very high oral sili-
con LDjg values for rats and mice. For rats and mice, respec-
tively, these include >22.5 and >15 g/kg as silicon dioxide
(Hartley and Kidd, 1987), 1.1-1.6 and 1.1 g/kg (Gosselin et
al., 1984; International Technical Information Institute,
1988) as sodium silicate, and 1.28 and 2.4 g/kg as sodium
metasilicate (Clayton and Clayton, 1981-1982). The oral
LDjQ for amorphous hydrophobic silica (food additive) was
reported to be >7.9 g/kg for rodents (Lewinson et al., 1994).
The World Health Organization (1970) indicated that the
probable lethal dose of oral silica or magnesium trisilicate
for humans is over 15 g/kg BW, and for sodium silicate is
between 0.5 and 5 g/kg BW. The LCjq for carp was reported
as >10,000 mg/L/72 h (Hartley and Kidd, 1987).
Chronic
Table 26-1 summarizes the doses and effects of a chronic
consumption of high amounts of silicon by various animals
and humans. The table indicates that extremely high amounts
of silicon are needed to have just relatively minor effects on
growth. For animals, the most serious toxic effect of silicon
is the formation of kidney stones in ruminants. Silicon uroli-
thiasis is a concern in range animals in western Australia,
western regions of Canada, and the arid northwestern United
States where pasture plants contain high amounts of opaline
silica. In other parts of the world, silicon toxicity is not a
serious problem under practical farm or ranch conditions.
Siliceous calculi have been found in the urinary tracts of at
least 50 percent, and in some cases as many as 80 percent, of
cattle in North American range herds (Bailey, 1981). Dis-
placement of large calculi from the bladder to the urethra
can obstruct the normal flow of urine and distend the abdo-
men to produce the condition known as "water belly." If
treatment is not begun within a day or two, the obstruction is
fatal because it causes the rupture of the bladder or urethra.
Mortality as high as 5-10 percent has been found in sheep in
areas of Australia where calculi most commonly occur, and
up to 5 percent among range steers in problem areas of North
America (Bailey, 1981).
An early study with female rats provided water contain-
ing 280 and 561 mg Si/L as sodium metasilicate for 2.5 years
and found a decrease in young born and weaned (Smith et
al., 1973). Amorphous silica apparently is nontoxic to repro-
duction. Rats, mice, rabbits, and hamsters fed 1,350, 1,340,
1,600, and 1,600 mg Si/kg BW per day, respectively, did not
exhibit any developmental toxicosis or teratogenicity (Food
and Drug Research Laboratories, 1973).
Factors Influencing Toxicity
Dietary fiber may affect silicon toxicity because in hu-
mans it significantly depressed silicon balance (Kelsay et
al., 1979). Sex and age of animals apparently affect the re-
sponse to high dietary silicon. Supplementing drinking wa-
ter with sodium silicate to provide 280 mg Si/L depressed
weight gain in female but increased gain in male rats (Smith
et al., 1973), and 374 mg Si/L had a similar effect in sheep
(Smith et al., 1972). In an experiment where rats aged 3-7
weeks at the start were fed a urolithic diet containing 2 per-
cent tetraethylorthosilicate, the incidence of urolithiasis de-
creased 8.8 percent with each week increase in age (Emerick,
1986).
TISSUE LEVELS
Silicon is widely distributed in tissues. Highest concen-
trations are found in bone, nails, tendons, and vascular tis-
sue. Table 26-2 shows representative silicon concentrations
in some organs and fluids from various animals and humans.
Many of these data were obtained by using older colorimet-
ric analytical procedures; thus, the values given should be
considered only approximate. Nonetheless, this table shows
that no animal tissue or fluid used as a food will accumulate
silicon to the extent that it is of toxicological concern for
humans.
MAXIMUM TOLERABLE LEVELS
Because it is relatively nontoxic, establishing maximum
tolerable levels for animals is difficult. The lack of develop-
mental toxicosis or teratogenicity in several nonruminant
animal species at intakes of 1,340-1,600 mg Si/kg BW per
day as amorphous silicon dioxide (Food and Drug Research
Laboratories, 1973) indicates that the tolerable level for this
form of silicon is high. The maximum tolerable level for the
more bioavailable silicates (e.g., sodium metasilicate) is less
than that for silica, but still high based on findings of Smith
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352
MINERAL TOLERANCE OF ANIMALS
et al. (1973). They found that long-term (2.5 years) consump-
tion of water containing 280 and 561 mg Si/L as sodium
metasilicate moderately decreased reproductive performance
of rats (less young born and weaned). Ruminants apparently
tolerate higher intaJces of silicates than nonruminants. No
calculi were found in sheep fed diets containing up to 0.57
percent (5,700 mg/kg) silicon as sodium silicate (Emerick et
al., 1959). Drinking water containing 374 mg Si/L as sodium
silicate had equivocal effects on the growth of growing-fin-
ishing lambs (Smith etal., 1972). Prabowo and Spears (1992)
found that supplementing a coastal Bermuda grass-based diet
(containing 0.72 percent silica) with 1.5 percent silicic acid
(4,350 mg Si/kg) only had minor effects on the metabolism
of some minerals in lambs. The findings suggest that the
added soluble forms of silicon were converted into insoluble
forms in the gastrointestinal tract (Prabowo and Spears,
1992). Considering that diets containing up to 600 mg Si/kg
as metasilicate were found beneficial to chicks and rats
(Carlisle, 1984), and that 4,350 mg Si/kg diet as silicic acid
had only minor effects in lambs, the maximum tolerable level
of 2,000 mg Si/kg diet suggested for animals in 1980 (NRC,
1980) seems reasonable for soluble silicon compounds.
Much higher tolerable levels are appropriate for insoluble
forms of silicon (e.g., 50,000 mg/kg diet).
No acute oral silicon toxicity signs have been identified
for humans. The occurrence of silica stones in people on
long-term antacid therapy with magnesium trisilicate has
been reported. Because of the inadequacy of available data,
no maximum tolerable level for humans has been estab-
lished in the United States. In the United Kingdom, a Safe
Upper Level of 12 mg/kg BW per day has been suggested
for humans based on an animal study performed by
Takizawa et al. (1988). This value seems conservative, con-
sidering that Takizawa et al. (1988) found NOAELs of
50,000 mg/kg diet supplemental dietary silica, equivalent
to 2,500 mg/kg BW per day for rats, and 7,500 mg/kg BW
per day for mice. Thus, the amount of silicon in tissues of
animals fed high silicon diets are not of concern for human
health.
FUTURE RESEARCH NEEDS
There are no apparent pressing research needs in the area
of silicon toxicity. However, the determination of mecha-
nisms involved in silicon absorption and transport, mecha-
nisms in and factors affecting silica urolith formation, and
the silicon concentrations in various organs of domestic ani-
mals and humans, would further the understanding of the
toxicological properties of various silicon compounds.
SUMMARY
Next to oxygen, silicon is the most abundant element in the
Earth's crust. Silicon is tetravalent and has a strong affinity
for oxygen, and thus occurs in nature mostly as the oxide or
silicate. The chemistry of silicon is similar to carbon. Silicon
is essential for some lower forms of life where it has a struc-
tural role. Silicon generally is not accepted as essential for
higher animals and humans because it lacks a defined bio-
chemical function. Analytical techniques that use ion-coupled
plasma have become preferred for the analysis of silicon in
biological materials. Ashing of samples is a critical step in the
accurate analysis of silicon in low amounts because of con-
tamination and low silica solubility concerns. Dietary silicon
in low amounts is well absorbed (~50 percent) based on hu-
man findings. Based on studies mainly with ruminants, only a
small amount of silicon (generally less than 4 percent) is ab-
sorbed when the diet contains high amounts of silicon as silica.
Forages and cereal grains high in fiber are the major sources
of silicon for animals. The harmful effects of an excessive
intake of silicon in animals include a depression in roughage
DM digestibility and formation of urinary calculi for rumi-
nants, and depressed growth and abnormal reproduction for
rats. Extremely high intakes of silicon are required to have
minor effects on growth and reproduction. The maximum tol-
erable level for silicon as amorphous silicon dioxide is > 1,300
mg/kg BW per day for animals. The maximum tolerable level
for silicon as "soluble silica" (e.g., sodium metasilicate) of
2,000 mg/kg diet seem appropriate. Except for a few areas in
the world where conditions are right for urolithiasis, silicon
toxicity is not a major problem for domestic animals.
REFERENCES
Adler. A. J., Z. Etzion, and G. M. Berlyne. 1986. Uptake, distribution, and
excretion of ' ' silicon in normal rats. Am. J. Physiol. 25 1 :E670-E673.
Attain, P., A. Cailleux, Y. Mauras, J. C. Renier. 1983. Etude de I'absorption
digestive du silicium apres administration unique chez rhomme sous
forme de salicylate de methyl silane triol. Therapie 38:171—174.
Bailey, C. B. 1967. Siliceous urinary calculi in calves: prevention by addi-
tion of sodium chloride to the diet. Science 155:696-697.
Bailey, C. B. 1981. Silica metabolism and silica urolithiasis in ruminants: a
review. Can. J. Anim. Sci. 61:219—235.
Baumann, H. 1960. Verhatten der Kieselsaure im menschlichen Blut und
Harn. Hoppe-Seyler's Z. Physiol. Chem. 320:1 1-20.
Benke, G. M., and T. W. Osborn. 1979. Urinary silicon excretion by rats
following oral administration of silicon compounds. Food Cosmet.
Toxicol. 17:123-127.
Berlyne, G. M., A. J. Adler, N. Ferran, S. Bennett, and J. Holt. 1986. Silicon
metabolism. I. Some aspects of renal silicon handling in normal man.
Nephron 43:5-9.
Birchall, J. D., C. Exley, J. S. Chappell, and M. J. Phillips. 1989. Acute
toxicity of aluminum to fish eliminated in silicon-rich acid waters. Na-
ture 338:146-148.
Bowen, H. J. M., and A. Peggs. 1984. Determination of the silicon content
of food. J. Sci. Food Agric. 35:1225-1229.
Carlisle, E. M. 1984. Silicon. Pp. 257-291 in Biochemistry of the Essential
Ultratrace Elements, E. Frieden, ed. New York: Plenum Press.
Carlisle, E. M., and M.J. Curran. 1987. Effect of dietary silicon and alumi-
num on silicon and aluminum levels in rat brain. Alzheimer Dis. Assoc.
Disord. 1:83-89.
Carlisle, E. M., M. J. Curran, and T. Duong. 1991. The effect of interrela-
tionships between silicon, aluminum, and the thyroid on zinc content in
brain. Pp. 12-16— 12-17 in Trace Elements in Man and Animals 7, B.
Momcilovic, ed. Zagreb: IMI.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
SILICON
353
Cefali E. A., J. C. Nolan, W. R. McConnell, and D. L. Walters. 1996.
Bioavailability of silicon and aluminum from Zeolite A in dogs. J.
Pharmacol. 127:147-154.
Clayton, G. D., and F. E. Clayton. 1981-1982. Patty's Industrial Hygiene
and Toxicology, Vol. 2A, 2B, 2C, Toxicology, 3rd ed. New York: John
Wiley and Sons.
Corathers, L. A. 2002. Silicon. Pp. 68.1-68.12. In U.S. Geological Survey
Minerals Yearbook — 2002. Washington, D.C.: U.S. Government Print-
ing Office.
Emerick, R. J. 1986. Animal age and duration of exposure to a urolithic diet
as factors influencing silica urolithiasis incidence in an animal model.
Nutr. Rep. Int. 34:907-913.
Emerick, R. J., and H. Kayongo-Male. 1990. Interactive effects of dietary
silicon, copper, and zinc in the rat. J. Nutr. Biochem. 1:35^0.
Emerick, R. J., and D. Lu. 1987. A possible synergism of dietary phosphate
and urine-acidifying salts in preventing silica urolithiasis in a rat model.
J. Nutr. 117:1603-1608.
Emerick, R. J., and L. B. Embry, and O. E. Olson. 1959. Effect of sodium
silicate on the development of urinary calculi and the excretion of vari-
ous urinary constituents in sheep. J. Anim. Sci. 18:1025.
Farmer, V. C. 1986. Sources and speciation of aluminum and silicon in
natural waters. Pp. 4—23 in Silicon Biochemistry, D. Evered and M.
O'Connor, eds. Chichester: John Wiley and Sons.
Food and Drug Research Laboratories, Inc. 1973. Teratologic evaluation of
FDA 71-48 (Syloid; silica aerogel). Reports prepared under DHEW
Contract No. FDA 71-260. Maspeth, NY. 56 pp.
Frey, K. S., G. D. Potter, T. W. Odom, D. M. Senor, V. D. Reagan, V. H.
Weir, J. Elslander, S. P. Webb, E. L. Moms, W. B. Smith, and K. E.
Wiegand. 1992. Plasma silicon and radiographic bone density in
weanling Quarter Horses fed sodium zeolite A. J. Equine Vet. Sci.
12:291-295.
Gosselin, R. E., R. P. Smith, and H. C. Hodge. 1984. Clinical Toxicology of
Commercial Products, 5th ed. Baltimore: Williams and Wilkins.
Hartley, D., and H. Kidd, eds. 1987. The Agrochemicals Handbook, 2nd ed.
Lechworth, Herts, England: The Royal Society of Chemistry.
Hauptkorn, S., J. Pavel, and H. Seltner. 2001. Determination of silicon in
biological samples by ICP-OES after non-oxidative decomposition un-
der alkaline conditions. Fresenius J. Anal. Chem. 370:246-250.
Hidiroglou, M., M. Ivan, and M. Ihnat. 1981. Silicon in plasma of sheep.
Am. J. Vet. Res. 42:138-139.
Hildebrand, M., K. Dahlin, and B. E. Volcani. 1998. Characterization of a
silicon transporter gene family in Cylindrotheca fiisiformis: sequences,
expression analysis, and identification of homologs in other diatoms.
Mol. Gen. Genet. 260:480^86.
Hunter, M. J., and Aberg, B. 1975. The element silicon and its relation to
eai1h, man and life processes. Acta Pharmacol. Toxicol. Suppl. 36:9-16.
International Technical Information Institute. 1988. Toxic and Hazardous
Industrial Chemicals Safety Manual. Tokyo: International Technical
Information Institute.
Jones, L. H. P., and K. A. Handreck. 1965. The relation between the silica
content of the diet and the excretion of silica by sheep. J. Agric. Sci.
65:129-134.
Jugdaohsingh, R., S. H. C. Anderson, K. L. Tucker, H. Elliott, D. P. Kiel, R.
P. H. Thompson, and J. J. Powell. 2002. Dietary silicon intake and ab-
sorption. Am. J. Clin. Nutr. 75:887-893.
Kayongo-Male, H., and X. Jia. 1999. Silicon bioavailability studies in young
rapidly growing rats and turkeys fed semipurified diets. A comparative
study. Biol. Trace Elem. Res. 67:173-186.
Kayongo-Male, H., and I. S. Palmer. 1998. Copper-silicon interaction stud-
ies in young, rapidly growing turkeys fed semipurified starter diets. Biol.
Trace Elem. Res. 63:195-204.
Kelsay, J. L., K. M. Behall, and E. S. Prather. 1979. Effect of fiber from
fruits and vegetables on metabolic responses of human subjects. II. Cal-
cium, magnesium, iron, and silicon balances. Am. J. Clin. Nutr.
32:1876-1880.
Klemens, P., and K. G. Heumann. 2001. Development of an ICP-HRIDMS
method for accurate determination of traces of silicon in biological and
clinical samples. Fresenius J. Anal. Chem. 371:758-763.
Knight, C. T. G., and S. D. Kinrade. 2001. A primer on the aqueous chem-
istry of silicon. Stud. Plant Sci. 8:57-84.
Lang, K. J., B. D. Nielsen, K. L. Waite, G. M. HiU, and M. W. 2001. Supple-
mental silicon increases plasma and milk silicon concentrations in
horses. J. Anim. Sci. 79:2627-2633.
Leach, R. M., Jr., B. S. Heinrichs, and J. Burdette. 1990. Broiler chicks fed
low-calcium diets. I. Influence of zeolite on growth rate and parameters
of bone metabolism. Pouh. Sci. 69:1539-1543.
LeVier, R. R. 1975. Distribution of silicon in the adult rat and rhesus mon-
key. Bioinorg. Chem. 4:109-115.
Lewinson, J., W. Mayr, and H. Wagner. 1994. Characterization and toxico-
logical behavior of synthetic amorphous hydrophobic silica. Reg.
Toxicol. Pharmacol. 20:37-57.
McCullagh, K. G., and L. A. Ehrhart. 1974. Silica urolithiasis in laboratory
dogs fed semisynthetic diets. J. Am. Vet. Med. Assoc. 164:712.
Moshtaghian, C. M., C. M. Parsons, R. W. Leeper, P. C. Harrison, and K.
W. Koelkebeck. 1991. Effect of sodium aluminosilicate on phosphorus
utilization by chicks and laying hens. Poult. Sci. 70:955—962.
Najda, J., J. Gminski, M. Drozdz, and A. Danch. 1992. Silicon metabolism.
The interrelations of inorganic silicon (Si) with systemic iron (Fe),
zinc (Zn), and copper (Cu) pools in the rat. Biol. Trace Elem. Res.
34:185-195.
Najda, J., M. Goss, J. Gminski, L. Weglarz, K. Siemianowicz, and Z.
Olszowy. 1994. The antioxidant enzymes activity in the conditions of
systemic hypersilicemia. Biol. Trace Elem. Res. 42:63-70.
Nielsen, B. D., G. D. Potter, E. L. Morris, T. W. Odom, D. M. Senor, J. A.
Reynolds, W. B. Smith, M. T. Martin, and E. H. Bird. 1993. Training
distance to failure in young racing quarter horses fed sodium zeolite A.
J. Equine Vet. Sci. 13:562-567.
NRC (National Research Council). 1980. Silicon. Pp. 421^30 in Mineral
Tolerance of Domestic Animals. Washington, D.C.: National Academy
Press.
Pennington, J. A. T. 1991. Silicon in foods and diets. Food Addit. Contam.
8:97-118.
Prabowo, A., and J. W. Spears. 1992. Dietary silica effects on mineral me-
tabolism in lambs. Asian- Austustralas. J. Anim. Sci. 5:279-283.
Roland, D. A., Sr. 1988. Further studies of effects of sodium aluminosili-
cate on egg shell quality. Poult. Sci. 67:577-584.
Roland, D. A., Sr. 1990. The relationship of dietary phosphorus and sodium
aluminosilicate to the performance of commercial leghorns. Poult. Sci.
69:105-112.
Sauer, F., D. H. Laughland, and W. M. Davidson. 1959. Silica metabolism
in guinea pigs. Can. J. Biochem. Physiol. 37:183-191.
Schreier, C. J., and R. J. Emerick. 1986. Diet calcium carbonate, phospho-
rus, and acidifying and alkalizing salts as factors influencing silica uroli-
thiasis in rats fed tetraethylorthosilicate. J. Nutr. 116:823-830.
Schwarz, K. 1974. Recent dietary trace element research, exemplified by
tin, fluorine, and silicon. Fed. Proc. 33:1748-1757.
Schwarz, K. 1978. Significance and function of silicon in warm-blooded
animals. Review and outlook. Pp. 207—230 in Biochemistry of Silicon
and Related Problems, G. Bendz and I. Linquist, eds. New York: Ple-
num Press.
Seaborn, C. D., and F. H. Nielsen. 1993. Silicon: a nutritional beneficence
for bones, brain, and blood vessels? Nutr. Today 28:13-18.
Seaborn, C. D., and F. H. Nielsen. 2002a. Silicon deprivation and arginine and
cystine supplementation affect bone collagen and bone and plasma trace
mineral concentrations in rats. J. Trace Elem. Exp. Med. 1 5 : 1 1 3—1 22.
Seaborn, C. D., and F. H. Nielsen. 2002b. Dietary silicon and arginine af-
fect mineral element composition of rat femur and vertebra. Biol. Trace
Elem. Res. 89:239-250.
Seaborn, C. D., and F. H. Nielsen. 2002c. Silicon deprivation decreases
collagen formation in wounds and bone, and ornithine transaminase en-
zyme activity in liver. Biol. Trace Elem. Res. 89:251-261.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
354
MINERAL TOLERANCE OF ANIMALS
Sibbald, I. R. 1980. The effects of dietary cellulose and sand on the com-
bined metabolic plus endogenous energy and amino acid outputs of adult
cockerels. Poult. Sci. 59:836-844.
Smith, G. S., A. L. Neuman, A. B. Nelson, andE. E. Ray. 1972. Effects of
"soluble silica" upon growth of lambs. J. Anim. Sci. 34:839-845.
Smith, G. S., A. L. Neumann, V. H. Gledhill, and C. Z. Arzola. 1973. Ef-
fects of "soluble silica" on growth, nutrient balance, and reproductive
performance of albino rats. J. Anim. Sci. 36:271-278.
Stewart, S. R., R. J. Emerick, and R. H. Pritchard. 1990. High dietary cal-
cium to phosphorus ratio and alkali-forming potential as factors pro-
moting silica urolithiasis in sheep. J. Anim. Sci. 68:498-503.
Stewart, S. R., R. J. Emerick, and H. Kayongo-Male. 1993. Silicon-zinc
interactions and potential roles for dietary zinc and copper in minimiz-
ing silica urolithiasis in rats. J. Anim. Sci. 71:946-954.
Takizawa, Y., F. Hirasawa, E. Noritomo, M. Aida, H. Tsunoda, and S.
Uesugi. 1988. Oral ingestion of syloid to mice and rats and its chronic
toxicity and carcinogenicity. Acta Med. Biol. 36:27—56.
Thilsing-Hansen, T., and R. J. Jorgensen. 2001. Hot topic: prevention of
parturient paresis and subclinical hypocalcemia in dairy cows by zeolite
A administration in the dry period. J. Dairy Sci. 84:691-693.
VanDyck, K., R. Van Cauwenbergh, H. Robberecht, andH. Deelstra. 1998.
Determination of silicon in biological tissues. Pp. 39^3 in Metal Ions
in Biology and Medicine, Vol. 5, P. CoUery, P. Bratter, V. Negretti de
Bratter, L. Khassanova, and J. C. Etienne, eds. Paris: John Libbey
Eurotext.
Van Dyck, K., H. Robberecht, R. Van Cauwenbergh, V. Van Vlaslaer, and
H. Deelstra. 2000. Indication of silicon essentiality in humans. Serum
concentrations in Belgian children and adults, including pregnant
women. Biol. Trace Elem. Res. 77:25-32.
Van Soest, P. J., and L. H. P. Jones. 1968. Effect of silica in forages upon
digestibility. J. Dairy Sci. 51:1-5.
Villota, R., and J. G. Hawkes. 1986. Food applications and the toxicological
and nutritional implications of amorphous silicon dioxide. CRC Crit.
Rev. Food Sci. Nutr. 23:289-321.
Wannagat, U. 1978. Sila-pharmaca. Nobel Symp. 40:447-472.
Watkins, K. L., andL. L. Southern. 1991. Effect of dietary sodium zeolite A
and graded levels of calcium on growth, plasma, and tibia characteris-
tics of chicks. Pouh. Sci. 70:2295-2303.
World Health Organization International Programme on Chemical Safety.
1970. Toxicological evaluation of some food colors, emulsifiers, stabi-
lizers, anti-caking agents and certain other substances. FAO (Food and
Agriculture Organization) Nutrition Meetings Report Series No. 46A
WHO/FOOD ADD/70.36.
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27
Sodium Chloride
INTRODUCTION
The Earth's oceans are, on average, 2.68 percent salt.
Ocean-dwelling fish and other animals must constantly deal
with excessively high salt environments. Salt is rare and dif-
ficult to find in most of the land areas of the world that sup-
port plant growth and therefore most terrestrial animals have
had to develop mechanisms for strict conservation of salt, in
particular the sodium ion of salt. Since the dawn of time,
animals have instinctively forged trails to inland salt depos-
its, known as rock salt, to satisfy their need for salt. Salt was
highly prized in ancient times as obtaining salt was one of
the necessities of life. Though we take the availability of salt
for granted, wars were fought over salt, and roads were built
for the sole purpose of transporting it.
Salt is used for many commercial purposes as well, in-
cluding water softening, de-icing our roadways, and meat
preservation. Sir Humphrey Davy first separated salt into its
constituent parts of sodium (Na) and chlorine (CI) in 1807.
The properties of chlorine and sodium place them among the
most important of the basic raw materials that industry uses.
Chlorine compounds of commercial importance include hy-
drochloric acid, chloroform, and sodium hypochlorite. Im-
portant sodium compounds include sodium carbonate (soda),
sodium sulfate, sodium bicarbonate (baking soda), sodium
phosphate, and sodium hydroxide.
ESSENTIALITY
Both the sodium and chloride elements of salt are essen-
tial nutrients for virtually all forms of life. Sodium and chlo-
ride are indispensable for maintenance of osmotic and acid-
base balance. Sodium is the chief cation and chloride is the
chief anion of the extracellular fluids. Blood is approxi-
mately 0.9 percent salt. Nerve and muscle resting membrane
potentials are highly dependent on proper sodium and chlo-
ride concentrations. The chemistry of sodium in the body is
almost entirely that of a monovalent cation — it rarely forms
covalent bonds in the body with the exception of certain so-
dium compounds found in bone. Therefore sodium contrib-
utes greatly to the osmolarity of body fluids. Chloride is the
ionized form of chlorine, a halogen, so it will readily accept
an electron and its chemistry is entirely nonmetallic. When
in solution, sodium ions attract a large number of water mol-
ecules, forming a water shell around each sodium ion. Potas-
sium and chloride ions have a much smaller water shell
around them. It is believed these water shields must be shed
before these ions can cross the cell membrane. The size of
the hydrated sodium ion, and the energy required to remove
the water shell from sodium, prevent sodium from crossing
cell membranes as easily as potassium and chloride do
(Harper et al., 1997).
Salt may be the only mineral compound for which ani-
mals truly develop a craving. Salt deficiency is often accom-
panied by observations of animals with pica, or abnormal
appetite, evidenced by their chewing or licking of wood,
rocks, soil, urine, and bones. Eventually osmotic and acid-
base disturbances cause a reduction in appetite. Animals fail
to grow, develop rough hair coats, and lactation comes to a
halt. Poultry will rapidly develop dehydration and become
easily agitated. Long-term salt deficiency will cause death
from dehydration. Most animals of economic importance to
terrestrial agriculture require between 0.1-0.4 percent so-
dium and 0.3-0.5 percent chloride in their diet for optimal
growth and productivity. Most plant origin feedstuffs are low
in sodium and salt is added to most diets to meet the sodium
requirements of the animal. For most species, the chloride
requirement of the diet is adequately met by the combination
of chloride from feedstuffs and from the salt added to meet
the animal's sodium requirement.
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Flame photometry, atomic absorption, and ion-sensitive
electrodes can be used to measure sodium. Ion-sensitive
357
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358
MINERAL TOLERANCE OF ANIMALS
electrodes or electrometric methods based on formation of
insoluble silver chloride during titration with silver nitrate
are used to determine chloride content of body fluids and in
diet components. The concentrations of chloride and sodium
in biological fluids are commonly expressed as mEq/L, while
feed analyses continue to express sodium and chloride con-
tent as a percentage of the feed.
Sodium content of body fluids and from feed sources is
readily determined by atomic absorption spectrophotometry.
For feed samples, the organic matrix can be destroyed by dry
ashing in a muffle furnace. The remaining ash is dissolved in
acid and the sodium determined by atomic absorption spec-
trophotometry. Cesium or potassium chloride is often added
to the sample to control ionization within the sample. The
presence of high concentrations of mineral acids following
wet ashing of the sample can reduce the sodium signal.
Chloride level in biological fluids such as serum, plasma,
and urine can be determined by a colorimetric method. Chlo-
ride in biological fluids is reacted with Hg[SCN], at an acidic
pH to produce a reddish-brown colored complex. The opti-
cal density of the color produced has a direct relationship
with the chloride concentration in the solution.
Chloride ion concentration in body fluids and in dry-ashed
feed samples dissolved in dilute nitric acid can also be mea-
sured with a chloride ion-selective electrode. The chloride
ion-selective electrode is a pellet of silver chloride in direct
contact with the sample solution. Because silver chloride has
extremely low solubility in water, the silver chloride pellet
never reaches chemical equilibrium with the sample water.
Instead, a small amount of chloride ion dissolves into the
sample. The resulting relative surplus of silver ions at the
surface of the pellet creates a measurable electrical potential
that varies with the concentration of chloride ions in the
sample. This potential is measured with an external refer-
ence electrode, and then scaled to chloride ion concentra-
tion. Ion-selective electrodes are sensitive only to the ion-
ized form of chloride. Un-ionized forms of chloride (for
instance, insoluble salts or organic compounds), will not be
detected. All chloride sensors suffer interferences from other
ions, working best when the concentrations of bromide, io-
dide, cyanide, silver, and sulfide ions are much lower than
the chloride ion concentration.
REGULATION AND METABOLISM
Between 85 and 95 percent of consumed sodium and chlo-
ride within diets is absorbed across the wall of the gas-
trointestinal tract. Absorption of sodium and chloride occurs
primarily in the upper small intestine but can occur through-
out the intestinal tract. Large amounts of sodium and chlo-
ride enter the gastrointestinal tract in salivary, pancreatic,
gastric, bile, and intestinal epithelial cell secretions. Sodium
must be secreted in large amounts in the upper small intes-
tine to create the concentration gradient that will power fa-
cilitated transport of diet-derived glucose and amino acids
across the intestinal mucosa. Chloride is secreted into the
lumen of the stomach to create a low pH vital to proteolysis.
Low pH also provides protection from ingested bacteria.
These sodium and chloride ions are quickly reabsorbed by
the intestinal tract distal to their point of secretion. When
they are not, an osmotic diarrhea will ensue. Diarrhea can
rapidly deplete extracellular stores of these minerals with
life-threatening consequences to tissue perfusion and acid-
base balance.
Most terrestrial animals evolved in an environment with a
scarce supply of sodium. Therefore an intricate mechanism
designed to be extremely adept at conservation of sodium
developed. Key to this process is the very efficient absorp-
tion of sodium from the intestinal tract. When sodium is ab-
sorbed in excess of needs it is readily excreted by the kid-
neys, if water is available. Excretion of sodium in urine,
salivary, and intestinal secretions is controlled by the com-
plex interplay of several hormones. The principal hormone,
aldosterone, is secreted by the adrenal glands in response to
a decline in plasma sodium concentration or systemic blood
pressure. Aldosterone causes increased renal conservation
of sodium while increasing renal potassium excretion. Atrial
natriuretic peptide secreted by the cardiac atrial cells in re-
sponse to hypertension increases renal excretion of sodium.
Vasopressin, secreted by the posterior pituitary in response
to excessively high blood osmolarity, will stimulate renal
reabsorption of water to lower plasma sodium concentra-
tion. Several gastrointestinal hormones, such as gastrin, gas-
tric inhibitory peptide, secretin, and vasoactive intestinal
peptide can affect the rate of secretion of chloride and so-
dium into the lumen of the gut. Chloride metabolism is inti-
mately tied to sodium metabolism, as factors that stimulate
sodium excretion generally tend to increase chloride excre-
tion. However, in order to produce a low pH in the lumen of
the stomach, chloride secretion into the lumen is enhanced
while sodium absorption from the lumen is increased.
Aquatic animals have different challenges than terrestrial
animals. Nearly all species of animal, whether vertebrate or
invertebrate, will maintain their extracellular and intracellu-
lar osmotic concentrations between 250 and 400 mOsm.
Why this particular level provided an evolutionary advan-
tage remains conjecture, but one theory contends that when
extracellular fluids exceed 400 mOsm the cell must use
amino acids and urea to help maintain intracellular osmotic
pressures (Steele et al., 2004). This represents an inefficient
use of amino acids and may also lead to problems with dis-
position of nitrogen.
Ocean-dwelling crustaceans, fish, and higher vertebrates
will typically be in an environment that is 1,000 mOsm, with
salt contributing the bulk of osmotic particles to the solution.
Sodium chloride represents about 77 percent of the total dis-
solved solids in seawater, with calcium, magnesium, and car-
bonate comprising the largest proportion of the remaining sol-
ute. Because their gills and skin (consider the Asiatic
crab-eating frog) are not totally impervious to water, marine
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SODIUM CHLORIDE
359
animals are constantly trying to retain water within their bod-
ies since the high salt water environment they reside in draws
water away from their body. Unfortunately, their only option
for obtaining water is to drink seawater. To survive they must
have a mechanism to excrete the salts in seawater and retain
the water to osmoregulate. Kidneys cannot make urine that is
more concentrated (has higher osmolarity) than the extracel-
lular fluids, so renal excretion of salt will not be adequate.
Therefore these species must use other organs specialized in
excretion of sodium and chloride. For most ocean-dwelling
fish this organ is the gill, which is equipped with high num-
bers of sodium-potassium ATP-ase pumps capable of remov-
ing sodium from the blood and pumping it against its concen-
tration gradient back into the sea. Chloride appears to follow
the sodium by moving down the electrical gradient created by
the movement of the sodium. Though birds have skin that is
less impervious to water loss than the gills of fish or the skin
of amphibians, they also lose water, which must be replen-
ished. Seabirds have special glands located in the region of the
ethmoid turbinates of the skull that extract salt from seawater,
allowing them to live on the oceans of the world. Myriad other
adaptations exist in nature to allow osmoregulation when liv-
ing in the ocean (Schmidt-Nielsen, 1974).
Vertebrates living within fresh water face the opposite
problem. Since their bodies have greater osmolarity than the
water bathing them, water is constantly trying to enter their
body. They do not drink water, as more water than they can
use is absorbed across their gills and/or skin. In addition to
avoiding excessive water gain they also must try to avoid
salt loss from their body as salt will tend to diffuse from the
extracellular fluids to the fresh water. These species excrete
water via their kidneys, which form a very dilute urine.
Though salt is not in great supply in their environment, fresh-
water fish adapt to constant salt loss by utilizing extremely
powerful methods to absorb any existing sodium and chlo-
ride from the water across their gills. Amphibians use their
skin in a similar fashion. Freshwater species are often able to
absorb sodium from water that is as low as 6-7 |jM sodium,
while their own extracellular fluids are approximately 100
mM sodium, a 10,000-fold difference in concentration
(Stobbart, 1965). Freshwater fish find osmoregulation easier
in hard water than in pure water — it is easier to maintain
extracellular fluids at 300 mOsm in water that is 5-10 mOsm
than when the water is 1-2 mOsm!
Unfortunately, some other cations and anions that are
considered toxic, such as mercury, can also be absorbed by
the mechanisms designed to help the freshwater inhabitant
absorb sodium and chloride to osmoregulate. Just as they are
very efficient at pulling sodium and chloride from the water
they may also inadvertently concentrate contaminants that
might be within that fresh water. In many cases higher salt in
the fresh water can allow the salt to out-compete minerals
such as mercury, cadmium, chromium, and zinc for binding
sites during absorption, and reduce the uptake of these tox-
ins from the water (Hall and Anderson, 1995).
In all species, when sodium or chloride is added sepa-
rately to the diet (not as sodium chloride) the acid-base sta-
tus of the animal is likely to change. This aspect of sodium
and chloride metabolism — which is often the factor deter-
mining the toxic level of these individual minerals — is de-
scribed in detail in the section on Minerals and Acid-Base
Balance.
SOURCES AND BIOAVAILABILITY
Almost one-third of the irrigated land on Earth is not
suitable for growing crops because it is contaminated with
high levels of salt. High soil salinity causes both hyperionic
and hyperosmotic stress effects on plants, and the conse-
quence of these on the ability of the plant to take up and
retain water can be plant demise (Hasegawa et al., 2000).
As a result, terrestrial plants, by and large, do not contain
enough sodium to meet the dietary sodium requirement of
animals. Most grasses and legumes will contain less than
0.05 percent sodium. In coastal areas, winds can carry sea
salt a short distance inland and this salt is sometimes de-
posited in relatively high concentrations on the outside of
plants grown in these areas, producing forages much higher
in sodium and chloride. However, internally these plants
remain low in sodium.
Chloride content of plants is much more variable and gen-
erally reflects soil chloride content and fertilization practices.
Alfalfa, grasses, corn, wheat, and other common crop plants
often range from 0.2-1.2 percent chloride. One variable that
commonly affects plant chloride content is whether potash
was used to supply potassium to the crop. The potassium re-
quirements of crops are generally described on the basis of
potash, K^05, equivalents. However, more than 90 percent of
the potash sold in the United States is actually muriate of pot-
ash, better known as potassium chloride, originating from
huge deposits in Saskatchewan. Crops that are heavily fertil-
ized with "potash" are likely to be relatively high in chloride.
Animal-derived dietary components such as meat meal,
blood meal, and fish meal are very high in sodium content.
Blood meal is about 0.4 percent sodium and Menhaden fish
meal can be 0.8 percent sodium. Carnivorous animals con-
suming diets high in animal-derived products do not gener-
ally require salt supplementation.
All salt available in the United States for addition to diets
of animals is at least 98 percent NaCI and must comply with
the National Research Council's Food Chemicals Codex
Sodium Chloride Monograph (NRC, 1996a). It specifies that
salt may contain up to 2 percent impurities. Included in the 2
percent, salt may commonly contain up to 13 mg/kg sodium
ferrocyanide or up to 25 mg/kg of green ferric ammonium
citrate to prevent caking in table salt. In addition potassium
iodide is often added at levels of 0.006 to 0.010 percent to
prevent iodine deficiency disorders (iodized salt). Dextrose,
when added (typically at about 0.04 percent), acts as a stabi-
lizer for potassium iodide in salt. Otherwise the potassium
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MINERAL TOLERANCE OF ANIMALS
iodide tends to dissociate into "free" iodine, whicti vapor-
izes and may be lost from tiie salt. "Halite" is a lower grade
of rock salt sold for de-icing driveways and for nonfood uses.
It isn't pure enough to meet the standards of "food grade."
Impurities often color it gray or even brown.
Sodium salts commonly used in the feed industry include
sodium phosphate, sodium carbonate and bicarbonate, so-
dium sulfate, and sodium selenite. In all the above salts, the
toxic dose of the salt is dictated by the anion of the salt rather
than the sodium of the salt, unless the sodium is causing an
uncompensated metabolic alkalosis. Chloride is a common
anion found in combination with many of the cationic macro
and trace minerals, such as calcium chloride, manganese
chloride, and magnesium chloride. Because the chloride an-
ion is generally better absorbed than the cation in these salts,
ingestion in excessively high amounts would be expected to
cause acidification of the extracellular fluids, which can be
life threatening.
TOXICOSIS
Sodium toxicity and chloride toxicity can occur sepa-
rately, primarily because of the effect these ions can have on
acid-base physiology (see chapter on Minerals and Acid-
Base Balance). However, when fed as sodium chloride, the
effects on acid-base physiology are negligible. The remain-
der of this chapter will only consider the effects of sodium
chloride toxicity to the animal when fed in this form.
Single Dose Toxicity
A summary of the studies demonstrating the effects of a
single dose of salt on health of animals is presented in Table
27-1. Salt administered directly into the mouth of animals,
such as the dog and cat, can irritate the stomach, which will
cause emesis (vomiting) within 10 minutes. Although better
methods for inducing emesis exist, such as administration of
Syrup of Ipecac or 3 percent hydrogen peroxide, veterinar-
ians sometimes prescribe emergency administration of salt
to dogs suspected of ingesting toxic substances to help rid
them of the toxin. The quantity of salt that induces emesis in
dogs is 1-3 teaspoons (5-20 g), administered in the back of
the throat to ensure swallowing (Davis, 1980). Beyond eme-
sis, life-threatening hypernatremia (high blood sodium) can
develop in animals given this bolus dose of salt, especially if
water is not offered immediately after vomition, or if
vomition fails to occur. Gastric bleeding can also be observed
in some dogs. Horses and rats cannot be induced to vomit —
they lack the striated muscle in their esophagus necessary
for retrograde flow of stomach contents.
In rats, the LD^q for salt is reported to be 3.75 g salt/kg
BW. Note that this dose of salt given to the rat could not be
lost through vomition. Hypernatremia was the cause of death
(Boyd and Shanas, 1963). There are no data on the LD^q of a
single oral dose of salt for larger animals.
The voluntary ingestion of salt, when offered as salt
alone, is unlikely to ever be great enough to cause toxicity.
However when mixed with other palatable foods it is pos-
sible to ingest a toxic amount of salt. In one case report, an
Airedale terrier developed continuous seizure activity after
ingesting a salt-flour mixture used as sculpting clay for
small figurines. Serum concentrations of sodium (211 mEq/L;
normal = 145-158 mEq/L) and chloride (180 mEq/L; nor-
mal = 105-122 mEq/L) were greatly elevated. Brain so-
dium level (108 mEq/L; normal = <80 mEq/L) was be-
lieved responsible for swelling in the brain, which caused
the convulsive seizures (Khanna et al., 1997). In another
report, a pot-bellied pig ingested enough potato chips to
develop hypernatremia, causing ataxia and apparent blind-
ness (Holbrook and Barton, 1994).
Rapid establishment of ataxia and death occurred in
chickens given 4 g salt/kg BW administered into the crop
(Blaxland, 1946). A single cow was given two oral drenches
of 454 g of salt mixed with one pint of water within a 24-
hour period — which would approximate 2 g salt/kg BW. The
cow developed diarrhea, ataxia, and knuckling over at the
fetlocks but eventually recovered (Jones, 1930).
Access to water can greatly affect the toxicity of salt. Pigs
given 2.5 g salt/kg BW as an oral drench, and not permitted
access to water, developed ataxia and tremors, and died
within 2 days. The same amount of salt given to pigs with
access to water had no observable effects (Todd et al., 1964).
Hard-working horses lose great amounts of salt and water
in their sweat. Rehydration therapy of 0.9 percent (9,000
mg/kg) physiological saline solutions can be offered to the
horse, and horses will voluntarily consume up to 12 L of this
fluid. They must have access to fresh water later. Long term,
horses cannot tolerate water that supplies more than 10 times
their daily salt requirement (Nyman et al., 1996; Butudom et
al., 2004).
Freshwater fish can withstand rather dramatic increases
in saline content of their water for short periods of time.
Aquarium enthusiasts take advantage of this fact to remove
parasites from the gills of fish — the parasites find the salin-
ity of the water lethal but the fish can recover when placed
back into fresh water. Most freshwater fish will tolerate wa-
ter that is 3 percent salt (slightly more salt than seawater) for
up to 10 minutes (Swann and Fitzgerald, 1993). Lower salin-
ity can be tolerated longer.
Acute Toxicity
Salt intoxication occurs in two phases. During the first
phase, ingested sodium is rapidly absorbed into the blood,
causing a rapid rise in blood sodium and chloride concentra-
tions, especially if water is restricted and prevents renal
excretion of sodium. As plasma sodium rises above 160 mEq/L
there is a strong tendency for water to move from the cere-
brospinal fluid into the plasma. If severe enough, intracellu-
lar water will be drawn from the cells in the brain. This re-
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SODIUM CHLORIDE
361
suits in cellular dehydration and brain shrinkage. As the brain
shrinks away from the calvaria the blood supply to brain
cells can be disrupted, causing hemorrhage and thrombosis
(Finbergetal., 1959; Harber et al., 1996). If cell dehydration
is severe enough convulsions and death follow. If this first
episode is not severe enough to kill the animal, a second
phase of salt intoxication may occur over the next few days.
In order to avoid dehydration during hypernatremia, brain
cells will increase the osmolarity of their intracellular spaces.
This is, in part, accomplished by cell uptake of sodium, chlo-
ride, and potassium from the cerebrospinal fluid. However,
of greater importance is the accumulation of organic osmoles
such as taurine, glutamate, glutamine, and phosphocreatine
within the intracellular fluids of brain cells. If the
hypernatremia is rapidly corrected, as might occur if water is
suddenly offered to an animal that had limited access to wa-
ter for a prolonged period, the osmolarity of the extracellular
fluids would fall below that of the brain cell intracellular
fluids. Water would tend to move into the cells, causing brain
cells to swell. This occurs because the brain cells cannot
remove the organic osmoles from the intracellular spaces
quickly. Brain cells become hyperosmotic compared to the
extracellular fluids. Since the bones encasing the brain can-
not expand to accommodate the edematous cells, pressure
builds on the brain cells and causes necrosis of brain cells.
This can cause convulsions and death (Hogan et al., 1969).
In veterinary medicine it is more common for animals to be
observed in this second phase of salt intoxication. This syn-
drome is occasionally referred to as "water intoxication," as
the rapid restoration of normal blood osmolarity by water
ingestion is often the factor precipitating clinical symptoms.
Correction of severe salt toxicity or water deprivation should
therefore occur over a period of 2-3 days so that the brain's
adaptive mechanisms to prevent cellular dehydration and
cerebral edema are not overwhelmed (Angelos and Van
Metre, 1999). A summary of the studies demonstrating the
effects of acute oral exposure to salt of animals is presented
in Table 27-2.
Suckling calves fed a milk replacer containing 2.6 per-
cent salt exhibited nervous symptoms and pathological in-
creases in blood sodium and chloride concentrations. These
animals had no access to water other than that used to re-
constitute the milk replacer (Pearson and Kallfelz, 1982).
It was suggested that a high salt whey had mistakenly been
used in the milk replacer, since whey produced during the
manufacture of certain types of cheese can be as much as 8
percent salt.
Lactating dairy cows provided with 4 percent salt in a
grain mix, fed for 14 days at the rate of 1 kg/2 kg milk pro-
duced, exhibited no adverse effects, and the composition of
the milk was not changed (Demott et al., 1968). These cows
were fed hay and silage ad libitum so the estimated total salt
content of the diet was approximately 0.8-1 percent. These
cows also had full access to water. Pigs can tolerate 3 per-
cent salt in their diet, even if water intake is restricted, but
not eliminated. However, 5.3 percent salt in the diet cannot
be tolerated if water is not provided ad libitum (Done et al.,
1959).
Sudden introduction of water and/or salt to animals de-
prived of these substances can also cause toxicosis. Six of a
group of 100 feeder lambs that had been deprived of so-
dium chloride, then more recently deprived of water, de-
veloped water deprivation — sodium chloride intoxication
soon after water and a mineral supplement containing so-
dium chloride were reintroduced. The clinical signs in-
cluded somnolence, intense thirst, and generalized muscle
fasciculations. Serum chemical analyses revealed profound
hypernatremia and hyperchloremia. Postmortem examina-
tion of the dead lambs revealed microscopic evidence of
cerebral edema and cerebrocorticonecrosis (Scarratt et al.,
1985). Trueman and Clague (1978) reported high mortality
in steers fed a salt supplement and then put into paddocks
without water for 30 hours.
The poultry industry generally avoids addition of more
salt to a diet than the birds need because the birds drink more
water to permit salt excretion. The additional water lost in
the urine causes the litter in the house to become wet, which
greatly decreases air quality within the house. The study of
Smith et al. (2000) demonstrates that for every 0.25 percent
increase in salt content of the diet there will be an additional
9 g water excreted per g of feces. Typical poultry rations are
less than 0.5 percent salt. Within 1-2 days of being fed a diet
that was 1.85 percent salt, a commercial flock of 5-1 1 -day-
old turkey poults experienced 4 percent mortality preceded
by respiratory distress and ascites in affected birds (Swayne
et al., 1986). A commercial flock of growing turkeys fed a
diet with 8 percent salt exhibited diarrhea within two days
and a 6.7 percent mortality rate over the five days the birds
were fed the diet (Wages et al., 1995).
Scrivner (1946) found that 1 percent sodium chloride in
the feed for turkey poults was without effect, whereas 1 per-
cent salt in the drinking water resulted in 100 percent mor-
tality characterized by edema and ascites within 48 hours.
Some birds died rapidly, before they could develop ascites.
At 2 percent salt in the feed, half the poults developed edema
and ascites.
About 150 migrating waterfowl died and another 250 be-
came weak and lethargic from suspected salt poisoning after
resting in White Lake, a highly saline lake in North Dakota.
Frigid temperatures made fresh water in other lakes unavail-
able, forcing the birds to ingest the saline waters. Sick birds
recovered when removed from the salt water and released
into freshwater marshes. Brain sodium levels were higher in
dead geese submitted for necropsy than in controls
(Windingstad et al., 1987). Another interesting cause of
death, which may be termed a salt toxicity, occurs in water-
fowl resting on highly saline ponds. If the temperature drops
dramatically the salt begins to precipitate and crystallize
within the feathers of the sleeping birds floating in the water.
The weight of the salt crystals prevents the birds from flying
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MINERAL TOLERANCE OF ANIMALS
and they drown or are stranded, which forces them to drink
these highly saline waters (Wobeser and Howard, 1987;
Gordus et al., 2002).
Chronic Salt Toxicity
A summary of the studies demonstrating the effects fol-
lowing long-term exposure to salt via diet or water on
health of animals is presented in Table 27-3. The daily salt
requirement for mature beef cattle is less than 30 g/head/
day. Voluntary salt intake often exceeds minimum needs.
However there are limits to the amount of salt that cattle
will eat voluntarily and salt can be used to restrict the con-
sumption of highly palatable or expensive supplemental
feeds by animals at pasture where daily feeding is imprac-
tical. In such instances, daily voluntary intake of salt will
average 1 .5 g salt/kg BW for most classes of cattle. In some
studies, cows reach their voluntary salt intake limit at I g/
kg BW while in other studies, salt intake will not be af-
fected until the cow has consumed 2 g salt/kg BW (Riggs et
al., 1953; Rich et al., 1976; Schauer et al., 2004). When salt
is added to a supplement to limit intake, adult beef cows
can consume about 500 g salt/day over long periods of time
without adverse effects provided they have plenty of drink-
ing water. Excessive addition of salt to such supplements
will cause excessive feed restriction and cause reduced per-
formance in the cattle.
In ponies, supplemental grain intake could be restricted
by inclusion of salt at 16 percent of the grain supplement.
Feeding supplemental grain that was 8 percent or less salt
was not sufficient to keep the ponies from eating all the grain
put before them in one day (Parker, 1984). Ponies weighing
200 kg were fed 5 percent salt diets at 1 .5 percent of BW/day
for four weeks without deleterious effect. Since their total
salt intake was 175 g/day, the ponies tolerated 0.88 g salt/kg
BW when expressed on a BW basis.
In animals with access to water, the tolerable concentra-
tion of salt in the diet is very high. When total dietary salt fed
to lambs or ewes exceeded 7.6 percent, there was a small
reduction in weight gain of lambs and in lambs produced per
ewe (Meyer and Weir, 1954; Jackson et al., 1971). Lambs
weighing 27 kg were fed 5.85 percent salt rations for nearly
four months with no deleterious effects (Jackson et al., 197 1).
Assuming these lambs were consuming 2 percent of their
BW in DM/day, these lambs were safely ingesting 1 .8 g salt/
kg BW. Beef steers weighing 370 kg were fed a 9.33 percent
salt diet with no adverse effects (Meyer etal., 1955). Assum-
ing these steers were consuming 2 percent of their BW in
DM/day, these steers were safely ingesting 1.86 g salt/kg
BW. However, newly weaned calves suffered a reduction in
feed intake and growth rate when the diet was 7 percent salt.
Those calves fed a 4.75 percent salt diet grew normally
(Leibholz et al., 1980). Assuming these calves weighed 70
kg and were consuming 2.5 percent of their BW in DM/day,
these calves were safely ingesting 1.2 g salt/kg BW.
Paver et al. (1953) fed chicks up to 3.52 percent salt diets
with no observable toxic effects. However, day-old turkey
poults may be more susceptible to salt toxicity than day-old
broiler chicks. Day-old turkey poults fed 0.7, 1.2, and 1.7
percent salt diets for 14 days had similar feed intake and
rates of growth. Though poults fed 2.7 percent salt diets grew
normally, many died due to lung congestion and myocardial
abnormalities within 7 days of the initiation of the study
(Morrison et al., 1975). Roberts (1957) was able to feed
mature turkeys up to 4 percent salt diets with no adverse
effects. In the Roberts study it was noted that water intake
increased dramatically in birds given the high salt diet, al-
lowing increased renal excretion of salt. In the study of
Morrison et al., it was noted that the poults failed to increase
water intake with increasing salt. This difference in behavior
likely played a role in the increased mortality among young
poults given the higher salt diets. Young fowl are generally
considered more susceptible to salt toxicosis than older birds
because their kidneys are too immature to excrete sodium
and chloride rapidly when placed on a high salt diet
(Mohanty and West, 1969).
Zentek and Meyer (1995) found that dogs fed a diet con-
taining approximately 2.9 percent sodium (7.4 percent salt)
reduced their intake of the diet. The diet induced vomiting in
at least one dog. Boemke et al. (1990) found that potassium
excretion and potassium balance were negatively impacted
in dogs fed diets that were greater than 2 percent sodium (5
percent salt). Based on potassium balance alone their data
suggest the maximum tolerable salt level in the diet is 3.75
percent. Cats can tolerate very high levels of salt in the diet
when water is provided. Burger (1979) found that cats pre-
ferred lower salt diets but would consume diets that were
3.8 percent salt without ill effects. Kittens grow well and
suffer no ill effects when fed diets that are 2.5 percent salt,
though they prefer to eat lower salt diets (Yu et al., 1997).
The tolerance for salt in the drinking water is much lower
than the tolerance for salt in the diet. It is useful to keep in
mind that the ocean's waters are about 2.68 percent salt, and
blood is about 0.9 percent salt. Growing sheep can tolerate 1
percent salt in the drinking water for an extended period of
time with no observable adverse effects. However, when salt
content of drinking water exceeds 1.5 percent there is a re-
duction in weight gain, and at 2 percent salt in the water,
overt signs of weakness and marked weight reduction occur
(Pierce, 1957). Pregnant sheep forced to drink water that was
1.3 percent salt had an increased rate of stillborn lambs and
elevated blood chloride levels (Potter and Mcintosh, 1974).
Growing cattle exhibited reduced growth when drinking
water was 1.25 percent salt (Weeth and Haverland, 1961).
Lactating dairy cows forced to drink 0.25 percent salt
water (1,000 mg/L sodium and 1,500 mg/L chloride) pro-
duced less milk, but did not exhibit hypernatremia or a re-
duction in feed intake (Jaster et al., 1978). Brackish water
containing just 287 mg/L sodium and 580 mg/L chloride in
conjunction with other minerals was responsible for reduced
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SODIUM CHLORIDE
363
water consumption and reduced milk production in lactating
dairy cows (Solomon et al., 1995). The lower tolerance for
brackish water suggests the salt may not have been the only
factor contributing to the decreased performance of cows
drinking brackish water.
Young birds can be adversely affected by drinking water
that is as low as 0.4 percent salt (Krista, 1961). Older birds
are somewhat more tolerant. Egg production of laying hens
is not affected when water is 0.7 percent salt, but 1 percent
salt in the water greatly reduces egg production (Krista,
1961).
Prepartum diets high in sodium and/or potassium have
been implicated as causes of udder edema in cattle. Studies
by Hemken et al. (1969), Conway et al. (1977), and Jones et
al. (1984) demonstrated an increased incidence or severity
of udder edema with sodium chloride supplementation. In
the experiments of Hemken et al. (1969), restriction of so-
dium chloride and water intake reduced the severity and in-
cidence of udder edema in pregnant heifers. A lower inci-
dence and severity of udder edema were found when diets
contained no supplemental salts of sodium or potassium
(Randall et al., 1974). In a controlled study, heifers were fed
one of four diets: (1) no added sodium or potassium, (2) 227
g/day sodium chloride added, (3) 227 g/day potassium chlo-
ride added, or (4) 227 g/day sodium chloride and 227 g/day
potassium chloride added. These diets were fed during the
last 40 days before expected parturition. Addition of sodium
or potassium chloride increased the severity of udder edema.
The combination of adding both sodium and potassium chlo-
ride increased the severity numerically but not statistically
(Randall et al., 1974).
Nestor et al. (1988) reported the findings of a 2 X 2 facto-
rial experiment in which prepartum rations contained two
levels of supplemental potassium bicarbonate (0 versus 272
g/head per day) and two levels of supplemental sodium chlo-
ride (23 versus 136 g/head per day). The severity of udder
edema was greater when pregnant heifers were fed additional
potassium bicarbonate or sodium chloride separately, but the
combination of feeding both supplemental sodium chloride
and potassium bicarbonate did not increase udder edema
scores. The failure to get an additive effect of sodium and
potassium is difficult to understand. However it is possible
that feeding just one of the minerals, either sodium or potas-
sium alone, upsets the aldosterone balance of the body more
than when they are fed in combination. If this system is not
functioning properly, excessive retention of sodium or po-
tassium could occur, which may be contributing to the edema
of the udder and ventral abdomen. Perhaps the ratio of these
two minerals in a diet is critical to the function of the renin-
angiotensin-aldosterone endocrine system.
Factors Influencing Toxicity
The major determining factor in salt intoxication is the
availability of drinking water. Acute salt toxicity is essen-
tially eliminated if animals can use water to rid their bodies
of unwanted salt to regulate blood osmolarity.
TISSUE LEVELS
Normal blood sodium concentration is between 130 and
150 mEq/L for most species (Table 27-4). Normal blood
chloride concentration is 95-110 mEq/L. Hypernatremia,
with the possibility of clinical signs affecting the nervous
system, can be observed when mammalian blood sodium
concentration exceeds 160 mEq/L (Senturk and Huseyin,
2004). Plasma sodium concentrations above 225 mEq/L and
plasma chloride concentrations above 125 mEq/L are lethal
in mammals and birds. Cerebrospinal fluid sodium is nor-
mally 130-142 mEq/L in cattle and pigs. During salt toxicity
cerebrospinal fluid sodium concentration is generally above
160 mEq/L (Puis, 1994). Brain tissue levels of sodium and
chloride do not always correlate well with salt intoxication
especially if clinical symptoms are occurring during the re-
hydration phase of the intoxication (Wells et al., 1984). High
dietary salt concentration has little effect on tissue salt con-
tent, unless access to fresh water is restricted. Drinking water
that is high in salt can cause hypernatremia and increased
salt content of the brain.
MAXIMUM TOLERABLE LEVELS
In the absence of water, or if salt is in the only available
drinking water, there is an increased risk of salt toxicity.
However, it is beyond the scope of this report to set a maxi-
mum tolerable level that considers all these possible circum-
stances. The maximum tolerable level for salt in the diet of
the species listed below is calculated with the assumption
that water is freely available to the animals. The maximum
tolerable level is based on the level of salt that can be safely
fed without causing either a reduction in feed intake that
affects production, or induction of clinical signs of salt in-
toxication such as diarrhea or nervous system dysfunction.
Sodium absorbed independent of chloride, from sources such
as sodium bicarbonate, will cause morbidity due to induc-
tion of metabolic alkalosis at levels well below those that
will affect bodily fluid osmolarity. Similarly, chloride ab-
sorbed independent of sodium, from sources such as calcium
chloride, risks induction of severe metabolic acidosis. These
situations are described in the chapter on Minerals and Acid-
Base Balance, and will not be discussed further here.
In ruminants and horses, about 1 g salt/kg BW can be
consumed without adversely affecting feed intake (Riggs et
al., 1953; Rich et al., 1976; Schryver et al., 1987; Schauer et
al., 2004). Beyond these levels feed intake and productivity
could be observed to decline in some animals, though there
is considerable variation in the capacity for voluntary salt
intake between individual animals. Assuming 1 g salt/kg BW
is the maximum total load of salt the body can adapt to with-
out adversely affecting diet intake, it is possible to predict
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MINERAL TOLERANCE OF ANIMALS
the maximal concentration of salt that can be in a diet with-
out adversely affecting intake and therefore growth or per-
formance of the animal. A 410-kg beef steer in a feedlot
might be expected to consume 9 kg DM/day (2.2 percent of
BW) each day (NRC, 1996b). Its voluntary salt intake would
be about 410 g. Any diet containing more than 410 g salt/9
kg DM or 4.55 percent salt would be expected to limit intake
of the steer. For a 650-kg lactating dairy cow consuming 3.3
percent of her BW each day, a similar calculation predicts
that the cow could tolerate up to 3 percent salt in her diet
without adversely affecting feed intake. A 450-kg horse con-
suming 1.5 percent of its BW in DM could tolerate a 6.6
percent salt diet.
There is only one applicable study in poultry, the study by
Morrison et al. (1975) in turkey poults, and it suggests the
tolerance for dietary salt of poultry may be higher than in
mammals. If we assume that at 2 weeks of age the turkey
poults weighed about 270 g and consumed about 25 g diet/day,
the 1.7 percent salt diets that were safely fed to the poults
supplied 1.57 g salt/kg BW. Although there are concerns to
the industry in terms of wet droppings when birds are fed high
salt diets, the maximum tolerable amount of salt that can be
fed to poultry without affecting feed intake is 1.5 g/kg BW.
No long-term toxicity studies on the effects of high salt
diets have been conducted in pigs. However, based on short-
term studies by Done et al. (1959), adverse effects of salt
were only seen with >5 percent salt diets and only when
access to water was restricted. This study also suggested pigs
readily tolerate 3 percent salt in the diet. Assuming these
pigs were eating 3 percent of their BW in DM/day these pigs
were safely consuming 0.9 g salt/kg BW. It is likely that 5
percent salt diets, providing about 1.5 g salt/kg BW, would
be tolerated if water were freely accessible, but data from
long-term studies on high salt diets do not exist. The maxi-
mum tolerable salt load for pigs is therefore conservatively
set at 1.0 g salt/kg BW.
Cats can safely consume diets that are 3.8 percent salt but
they prefer lower salt diets. Since the studies of Burger
(1979) involved adult cats, an assumption that these were 4-
kg cats consuming about 1.6 percent of their BW in DM/day
can be made. This is a maximal tolerable limit of just 0.6 g
salt/kg BW. Kittens safely consumed a 2.5 percent salt diet
(Yu et al., 1997). The kittens can be assumed to have
weighed approximately 800 g and consumed about 5.5 per-
cent of their BW in DM/day. Therefore they were safely
consuming about 1.37 g salt/kg BW. Unfortunately data do
not exist to allow a more precise estimate in cats. The study
of Boemke et al. (1990), which used potassium balance as a
criteria for safety, suggests the maximum tolerable dietary
salt level for dogs is 3.75 percent. Assuming these adult dogs
weighed 15 kg and were consuming 1.7 percent of their BW
in DM/day, dogs can safely consume 0.64 g salt/kg BW.
While it is expected that feed intake would be reduced
once the maximum salt load is reached, there are instances
where animals will consume toxic amounts of salt. Usually
this is associated with the rapid ingestion of a newly offered
high salt diet. In these cases, clinical illness can be observed
in animals fed very high salt diets, even when adequate wa-
ter is supplied. At what dietary salt level this occurs is diffi-
cult to define. In young growing birds, diets that are 2.7 per-
cent salt lead to rapid mortality (Morrison et al., 1975). At
this dietary salt level it is estimated that the birds are con-
suming 2.5 g salt/kg BW. In suckling calves fed 2.6 percent
salt milk replacer, toxicity and mortality were observed
(Pearson and Kallfelz, 1982). The salt load on these calves
can be estimated to have been 3.1 g salt/kg BW. The studies
by Meyer et al. (1955) suggested reduced lambing rates in
32-kg ewes fed a 13.1 percent salt diet. Assuming the ewes
consumed 2 percent of their BW in diet DM/day, the salt
load that caused this toxicity in the sheep was approximately
2.6 g salt/kg BW. For all species it is likely that animals
consuming more than 2.5 g salt/kg BW will suffer adverse
effects that include increased mortality.
It is beyond the scope of this report to determine the con-
centration of salt in the water at which each freshwater and
saltwater fish species will no longer be able to regulate its
internal osmolarity. Some fish can, with time, learn to
osmoregulate in both fresh and sea water during various
times of their lives. In general, freshwater fish will not toler-
ate water that is more than 1 .5 g sodium chloride/L ( Arenzon
et al., 2003), and ocean-dwelling fish will not survive when
sodium chloride in the water exceeds 3 percent, though some
fish are adapted to survive in inland lakes and seas with a
somewhat greater salt content (Wang et al., 2003). The Dead
Sea is so-called because no fish or even brine shrimp will
survive in its waters, which are 300 g/L salt, about ten times
the salinity of the oceans.
FUTURE RESEARCH NEEDS
There seems to be little research that precisely defines
the effects of salt on feed intake in cats and dogs. Also in
these pet species, there is little reported work on the ef-
fect of salt in the diet on dogs and cats with hypertrophic
cardiomyopathies.
An area of great concern, but one that has few data, con-
cerns the role of salt in the pathogenesis of udder edema, a
common affliction of dairy cows. Graded levels of salt be-
low those previously reported to induce udder edema in the
studies of Hemkenetal. (1969) and Nestor etal. (1988) need
to be added to dry cow diets and tested for their effect on
udder edema. This could allow definition of a maximum tol-
erable level of salt in diets intended for dry dairy cows, a
level above which udder edema is likely.
REFERENCES
Angelos, S. M., and D. C. Van Metre. 1999. Treatment of sodium balance
disorders. Water intoxication and salt toxicity. Vet. Clin. N. Am. Food
Anim. Pract. 15:587-607.
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inemi Tnlemnce nf Animals- Sennnd Revised Edition
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SODIUM CHLORIDE
365
Arenzon, A., R. F. Pinto, P. Colombo, and M.T. Raya-Rodriguez. 2003.
Assessment of the freshwater annual fish Cynopoecilus melanotaenia as
a toxicity test organism using three reference substances. Environ.
Toxicol. Chem. 22:2188-2190.
Barlow, J. S., S. J. Slinger, and R. P. Zimmer. 1948. The reaction of grow-
ing chicks to diets varying in sodium chloride content. Poult. Sci.
27:542-549.
Blaxland, J. D. 1946. The toxicity of sodium chloride for fowls. Vet. J.
102:152
Boemke, W., U. Palm, G. Kaczmarczyk, and H. W. Reinhardt. 1990. Effect
of high sodium and high water intake on 24-h potassium balance in
dogs. Z. Versuchstierkd. 33:179-185.
Bohstedt, G., and R. H. Grummer. 1954. Salt poisoning of pigs. J. Anim.
Sci. 19:933-939.
Boyd, E. M., and M. N. Shanas. 1963. The acute oral toxicity of sodium
chloride. Arch. Int. Pharmacodyn. Ther. 144:86-96.
Burger, I. 1979. Water balance in the dog and cat. Pedigree Digest 6:10—11.
Butudom, P., D. J. Barnes, M. W. Davis, B. D. Nielsen, S. W. Eberhart, and
H. C. Schott II. 2004. Rehydration fluid temperature affects voluntary
drinking in horses dehydrated by furosemide administration and endur-
ance exercise. Vet. J. 167:72-80.
Conway, J. F., H. H. Olson, and G. C. McGoy. 1977. Effects of sodium
chloride supplementation on the incidence and severity of mammary
edema and on senjm sodium levels in pre-parturient cows and heifer. J.
Dairy Sci. 60(Suppl.l):110 (Abstr.).
Davis, L. L. 1980. Gastrointestinal pharmacology. P. 278 in Veterinary
Gastroenterology, N. V. Anderson, ed. Philadelphia: Lea & Febiger.
Demott, B. J., S. A. Hinton, E. W. Swanson, and J. T. Miles. 1968. Influ-
ence of added sodium chloride in grain ration on the freezing point of
milk. J. Dairy Sci. 51:1363-1365.
Done, J. T., J. D. J. Harding, and M. K. Lloyd. 1959. Meningo-Encephalitis
eosinophilica of swine. II. Studies on the experimental reproduction of
the lesions by feeding sodium chloride and urea. Vet. Rec. 71:92-98.
Finberg, L., C. Luttrell, and H. Redd. 1959. Pathogenesis of lesions in the
nervous system in hypernatremic states. II. Experimental studies of gross
anatomic changes and alterations of chemical composition of the tis-
sues. Pediatrics 23:46—53.
Gordus, A. G., H. L. Shivaprasad, and P. K. Swift. 2002. Salt toxicosis in
ruddy ducks that winter on an agricultural evaporation basin in Califor-
nia. J. Wildl. Dis. 38:124-131.
Hall, L. W., Jr., and R. D. Anderson. 1995. The influence of salinity on the
toxicity of various classes of chemicals to aquatic biota. Crit. Rev.
Toxicol. 25:281-346.
Harber, E. S., M. G. O'Sulhvan, M. J. Jayo, and C. S. Carlson. 1996. Cere-
bral infarction in two cynomolgus macaques (Macaca fascicularis) with
hypernatremia. Vet. Pathol. 33:431^34.
Hardy, R. M. Hypernatremia. 1989. Vet. Clin. N. Am. Small Anim. Pract.
19:231-240.
Harper, M. E., J. S. Willis, and J. Patrick. 1997. Sodium and chloride in
nutrition. In Handbook of Nutritionally Essential Mineral Elements, B.
L. O'Dell and R. A. Sunde, eds. New York: Marcel Dekker.
Hasegawa, P. M., R. A. Bressan, J. K. Zhu, and H. J. Bohnert. 2000. Plant
cellular and molecular responses to high salinity. Annu. Rev. Plant
Physiol. Plant Mol. Biol. 51:463^99.
Hemken, R. W., W. H. Choate, and R. D. Plowman. 1969. Sah and water
intakes as related to udder edema. J. Anim. Sci. 28:874 (Abstr.).
Hogan, G. R., P. R. Dodge, S. R. Gill, S. Master, J. F. Sotos. 1969. Pathogen-
esis of seizures occurring during restoration of plasma tonicity to normal
in animals previously chronically hypernatremic. Pediatrics 43:54—64.
Holbrook, T. C, and M. H. Barton. 1994. Neurologic dysfunction associ-
ated with hypernatremia and dietary indiscretion in Vietnamese pot-
bellied pigs. Cornell Vet. 84:67-76.
Jackson, H. M., R. P. Ki'omann, and E. E. Ray. 1971. Energy retention in
Iambs as influenced by various levels of sodium and potassium in the
rations. J. Anim. Sci. 33:872-877.
Jaster, E. H., J. D. Schuh, and T. N. Wegner. 1978. Physiological effects
of saline drinking water on high-producing dairy cows. J. Dairy Sci.
61:66-71.
Jones, T. H. 1930. Salt poisoning in a cow. Vet. Rec. 10:10.
Jones, T. O., R. Knight, and R. K. Evans. 1984. Chronic udder oedema in
milking cows and heifers. Vet. Rec. 115:218-219.
Khanna, C, H. J. Boermans, and B. Wilcock. 1997. Fatal hypernatremia in
a dog from salt ingestion. J. Am. Anim. Hosp. Assoc. 33:113-117.
Krista, L. M., C. W. Carlson, andO. E. Olson. 1961. Some effects of saline
waters on chicks, laying hens, poults, and ducklings. Poult. Sci.
40:938-943.
Leibholz, J., R. C. Kellaway, G. T. Hargreave. 1980. Effects of sodium
chloride and sodium bicarbonate in the diet on performance of calves.
Anim. Feed Sci. Technol. 5:309-314.
Meyer, J. H., and W. C. Weir. 1954. The tolerance of sheep to high intakes
of sodium chloride. J. Anim. Sci. 13:443^50.
Meyer, J. H., W. C. Weir, N. R. Ittner, and J. D. Smith. 1955. The influence
of high sodium chloride intakes by fattening sheep and cattle. J. Anim.
Sci. 14:412^17.
Mohanty, G. C, and J. L. West. 1969. Pathologic features of experimental
sodium chloride poisoning in chicks. Avian Dis. 13:762—773.
Morrison, W. D., A. E. Ferguson, J. R. Pettit, and D. C. Cunnigham. 1975.
The effects of elevated levels of sodium chloride on ascites and related
problems in turkeys. Poult. Sci. 54:146-154.
NRC (National Research Council). 1996a. Food Chemicals Codex — Sodium
Chloride Monograph. Washington, D.C.: National Academy Press.
NRC. 1996b. Nutrient Requirements of Beef Cattle. Washington, D.C.:
National Academy Press.
Nestor, K. E. Jr., R. W. Hemken, and R. J. Harmon. 1988. Influence of
sodium chloride and potassium bicarbonate on udder edema and se-
lected blood parameters. J. Dairy Sci. 71:366-372.
Nyman, S., A. Jansson, K. Dahlborn, and A. Lindholm. 1996. Strategies for
voluntary rehydration in horses during endurance exercise. Equine Vet.
J. (Suppl.) 22:99-106.
Parker, M. I. 1984. Effect of sodium chloride in feed preference and on
control of feed and water intake in ponies. M.S. thesis, Cornell Univer-
sity, Ithaca, NY.
Paver, H., A. Robertson, and J. E. Wilson. 1953. Observations on the toxic-
ity of salt for young chickens. J. Comp. Path. 63:31.
Pearson, E. G., and F. A. Kallfelz. 1982. A case of presumptive salt poison-
ing (water deprivation) in veal calves. Cornell Vet. 72:142-149.
Pierce, A. W. 1957. Studies on salt tolerance of sheep for sodium chloride
in the drinking water. Aust. J. Agric. Res. 8:711—717.
Potter, B. J., and G. H. Mcintosh. 1974. Effect of salt water ingestion on
pregnancy in the ewes and on lamb survival. Aust. J. Agric. Res. 25:909—
913.
Puis, R. 1994. Mineral Levels in Animal Health: Diagnostic Data, 2nd ed.
Clearbrook, BC, Canada: Sherpa International.
Randall, W. E., R. W. Hemken, L. S. Bull, and L. W. Douglas. 1974. Effect
of dietary sodium and potassium on udder edema in Holstein heifers. J.
Dairy Sci. 57:472^75.
Rich, T. D., S. Armbruster, and D. R. Gill. 1976. Limiting Feed Intake with
Salt (G76-324-A). Lincoln, NE: University of Nebraska Cooperative
Extension, University of Nebraska-Lincoln. Available at http://
ianrpubs.unl.edu/beef/g324.htm. Accessed April 18, 2005.
Riggs. J. K., R. W. Colby, and L. V. Sells. 1953. The effects of self-feeding
salt-cottonseed meal mixtures to beef cows. J. Anim. Sci. 12:379-393.
Roberts, R. E. 1957. Salt tolerance of turkeys. Poult. Sci. 36:672-673.
Scarratt, W. K., T. J. Collins, and D. P. Sponenberg.1985. Water depriva-
tion-sodium chloride intoxication in a group of feeder lambs. J. Am.
Vet. Med. Assoc. 186:977-978.
Schauer, C. S., G. P. Lardy, W. D. Slanger, M. L. Bauer, and K. K. Sedivec.
2004. Self-limiting supplements fed to cattle grazing native mixed-grass
prairie in the northern Great Plains. J. Anim. Sci. 82:298-306.
Schmidt-Nielsen, B. 1974. Osmoregulation: effect of salinity and heavy
metals. Fed. Proc. 33:2137-2146.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
366
MINERAL TOLERANCE OF ANIMALS
Schryver, H. F., M. T. Parker, P. D. Daniluii, K. I. Pagan, J. Williams, L. V.
Soderholm, and H. F. Hintz. 1987. Salt consumption and the effect of
salt on mineral metabolism in horses. Cornell Vet. 77:122-131.
Scrivner, L. H. 1946. Experimental edema and ascites in poults. J. Am. Vet.
Med. Assoc. 108:27-32.
Senturk, S., and C. Huseyin. 2004. Salt poisoning in beef cattle. Vet. Hum.
Toxicol. 46:26-27.
Smith, A., S. Rose, R. G. Wells, and V. Pirgozliev. 2000. Effect of excess
dietary sodium, potassium, calcium, and phosphorus on excreta mois-
ture of laying hens. Br. Poult. Sci. 41 :598-607.
Solomon, R., J. Miron, D. Ben-Ghedalia, and Z. Zomberg. 1995. Perfor-
mance of high-producing dairy cows offered drinking water of high and
low salinity in the Arava desert. J. Dairy Sci. 78:620-624.
Steele, S. L., P. H. Yancey, and P. A. Wright. 2004. Dogmas and controver-
sies in the handling of nitrogenous wastes: osmoregulation during early
embryonic development in the marine little skate Raja erinacea; re-
sponse to changes in external sahnity. J. Exp. Biol. 207:2021-2031.
Stobbart, R. H. 1965. The effect of some anions and cations upon the fluxes
and net uptake of sodium in the larva of Auedes aegypti (L). J. Exp.
Biol. 42:29^3.
Swann, L., and S. Fitzgerald. 1993. Use and application of salt in aquacul-
ture. University of Missouri-Columbia Extension Service Bulletin
#MX393, October.
Swayne, D. E., A. Shlosberg, and R. B. Davis. 1986. Salt poisoning in
turkey poults. Avian Dis. 30:847-852.
Todd, J. R., G. H. Lawson, and C. Dow. 1964. An experimental study of salt
poisoning in the pig. J. Comp. Pathol. 74:331-337.
Trueman, K. F., and D. C. Clague. 1978. Sodium chloride poisoning in
cattle. Aust. Vet. J. 54:89-91.
Wages, D. P., M. D. Ficken, M. E. Cook, and J. Mitchell. 1995. Sah toxico-
sis in commercial turkeys. Avian Dis. 39:158-161.
Wang, Y. S., R. J. Gonzalez, M. L. Patrick, M. Grosell, C. Zhang, Q. Feng,
J. Du, P. J. Walsh, and C. M. Wood. 2003. Unusual physiology of scale-
less carp, Gymnocypris przewalskii, in Lake Qinghai: a high altitude
alkaline saline lake. Comp. Biochem. Physiol. A Mol. Integr. Physiol.
134:409-^21.
Weeth, H. J., and L. H. Haverland. 1961. Tolerance of growing cattle for
drinking water containing sodium choloride. J. Anim. Sci. 20:518-523.
Wells, G. A., G. Lewis, S. A. Hawkins, and P. L. Don. 1984. Evaluation of
brain chloride determinations in the diagnosis of water deprivation/so-
dium salt intoxication in pigs. Vet. Rec. 114:631-365.
Windingstad, R. M., F. X. Kartch, R. K. Stroud, andM. R. Smith. 1987. Salt
toxicosis in waterfowl in North Dakota. J. Wildl. Dis. 23:443-446.
Wobeser, G., and J.Howard. 1987. Mortality of waterfowl on a hypersaline
wetland as a result of salt encrustation. J. Wildl. Dis. 23:127-134.
Yu, S., Q. R. Rogers, and J. G. Morris. 1997. Absence of a salt (NaCl)
preference or appetite in sodium-replete or depleted kittens. Appetite
29:1-10.
Zentek, J., and H. Meyer. 1995. Normal handling of diets — are all dogs
created equal? J. Small Anim. Pract. 36:354-359.
Copyright © National Academy of Sciences. All rights reserved.
&
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28
Sulfur
INTRODUCTION
Sulfur (S) is one of the few elements known and described
in detail in the ancient world and was referred to as Sulpur in
Latin. In Genesis liquid sulfur (which is elemental sulfur
with a temperature >132°C) was referred to as "brimstone"
and was associated with the fires of hell, probably because
elemental sulfur occurs in a yellow, relatively pure state in
the vicinity of volcanoes and hot springs. It is also widely
distributed in nature as iron pyrites, galena, sphalerite, cin-
nabar, stibnite, gypsum, epsom salts, celestite, barite, and
other such substances. Sulfur has an atomic number of 16
and an atomic weight of 32.06.
Sulfur is a pale yellow, odorless, brittle solid, which is in-
soluble in water but soluble in carbon disulfide. Organic com-
pounds containing sulfur, such as methionine, are very impor-
tant to normal life. Calcium sulfate, ammonium sulfate, carbon
disulfide, sulfur dioxide, and hydrogen sulfide are but a few of
the many important inorganic compounds of sulfur.
The sulfur atom in organic and inorganic compounds can
be present in at least five oxidation states: -2 (sulfide, or-
ganic thiols such as cysteine and glutathione, and most other
organosulfur compounds); (elemental sulfur); +2 (sulfenic
acid); +4 (inorganic sulfite, and sulfinic acids such as
cysteinesulfinic acid and hypotaurine); and +6 (inorganic
sulfate, and sulfonic acids such as taurine and cysteic acid).
Sulfur atoms in sulfur-containing amino acids are divalent
(-2) and thus in the most reduced state, and the sulfur atom
of sulfate is in the fully oxidized hexavalent (+6) state.
Until 2000, sulfur was commercially recovered from
wells sunk into the salt domes along the Gulf Coast of the
United States. Using the Frasch process, heated water was
forced into the wells to melt the sulfur, which was then
brought to the surface. Sulfur also occurs in natural gas and
petroleum as hydrogen sulfide and other forms. These were
once emitted as a waste during coal washing or during com-
bustion, but are now recovered and used. Bituminous coal
used in the coke-making processes is about 0.6 to 2.6 per-
cent sulfur, depending on the grade of coal purchased. In the
past, burning of coal and other fossil fuels released large
amounts of sulfur dioxide into the atmosphere, which was
converted to sulfuric acid when it contacted water and caused
acidification of lakes and rivers downwind of the emissions.
Today, much of the sulfur is removed from coal before it is
burned and scrubbers within the smokestacks allow recov-
ery of a good deal of the remaining sulfur, which has greatly
reduced sulfurous emissions, though they still remain a con-
cern. Much of the sulfur harvested is used to produce sulfu-
ric acid, which in turn, is used in chemical reactions to pro-
duce a wide variety of products, including phosphate
fertilizer and white paper. Sulfuric acid production is the
major end use for sulfur, and consumption of sulfuric acid
has been regarded as one of the best indexes of a nation's
industrial development. More sulfuric acid is produced in
the United States every year than any other chemical. Sulfur
compounds are also used in the production of gunpowder
and fungicides, the vulcanization of rubber, and the manu-
facture of synthetic fibers such as rayon. Sulfur in the form
of sulfites is commonly added to foods as a preservative.
In 2003, approximately 8.8 million tons of sulfur were
produced in the United States, with 45 percent of that com-
ing from the petroleum refineries of Texas and Louisiana.
Still the United States imported nearly 3 million tons of sul-
fur to meet domestic industrial needs for sulfur — mostly as
sulfuric acid. Agricultural chemicals, primarily for fertilizer
production, accounted for 70 percent of all sulfur used in the
United States in 2003 (USGS, 2004).
ESSENTIALITY
The body is approximately 0.15 percent sulfur by weight.
The sulfur is primarily incorporated into a number of or-
ganic molecules vital to life, making sulfur an essential nu-
trient. Sulfur-containing compounds include several sulfur-
containing amino acids and their metabolites (methionine,
cysteine, cystine, homocysteine, taurine, cystathionine, and
372
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SULFUR
373
cysteic acid), thiamine, biotin, lipoic acid, co-enzyme-A,
glutathiione, chondroitin sulfate and cartilage mucopolysac-
charides, fibrinogen, heparin, ergothionine, and certain
forms of estrogens. These compounds are found in nearly all
tissues of the body. Many of these sulfur-containing com-
pounds required by the body can be synthesized from me-
thionine. Unfortunately, no vertebrate is capable of produc-
ing methionine from inorganic sulfur in the diet. Therefore,
organic sulfur in the form of methionine is an essential nutri-
ent in the diet of all vertebrate animals. Two other essential
sulfur-containing compounds cannot be produced from me-
thionine and must also be supplied in the diet of vertebrates
(or produced by microbes in the forestomachs). These are
thiamine and biotin, which are classified as water soluble B
vitamins. Cystine can also be converted to many of the sul-
fur-containing compounds required by the body and can
spare methionine for other purposes if it is present in the
diet, but because cystine can be made from methionine it is
not considered essential. There is evidence that some inor-
ganic sulfur in the form of sulfates can be absorbed and in-
corporated into organic compounds such as taurine and car-
tilage mucopolysaccharides. As much as 15 percent of the
dietary requirement for cystine can be replaced by inorganic
sulfate present in the diet (Sasse and Baker, 1974; Soares,
1974). Examined in its entirety, the contribution of inorganic
sulfur sources to the essential functions of sulfur in the body
are small. Diets that contain just 0.05 percent sulfur will satu-
rate the ability of the body to use dietary inorganic sulfur for
production of some of the organic sulfur-containing com-
pounds (Anderson et al., 1975). However, no amount of in-
organic sulfate added to the diet can replace methionine, thia-
mine, or biotin.
Some important species differences exist with respect to
the essentiality of this element. For instance cats (the entire
family Felidae) cannot synthesize taurine from methionine,
so taurine becomes an essential nutrient in feline diets. Be-
cause vertebrate tissues cannot produce methionine, thia-
mine, and biotin from inorganic sulfur in the diet, there is no
dietary requirement for inorganic sulfur in nonruminant spe-
cies. Bacteria within the rumen can synthesize methionine,
thiamine, and biotin in quantities that are high enough to
support much of the need for methionine of the host rumi-
nant. For most ruminants, sulfur must be between 0.18 and
0.24 percent of the diet to allow the microbes of the foregut
to produce sufficient sulfur-containing compounds to sup-
port bacterial growth for good rumen function and to pro-
vide sulfur-containing compounds to meet the demands of
the host ruminant. In these species, methionine, thiamine,
and biotin do not ordinarily need to be added to the diet.
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Various methods exist for determination of sulfur content
of feedstuffs, forages, and water samples. Turbidometric
tests for sulfur have been used for a long time. Samples of
water, diet, or feedstuffs are analyzed by wet ashing the
sample in nitric acid and mixing the sample with barium
chloride to form barium sulfite precipitates. The resulting
turbidity of the solution can be measured by spectrophotom-
etry at 440 nm and the turbidity increases with sulfur content
of the sample. The method suffers some variability problems
as the barium sulfate crystallization process does not always
form uniform crystals.
Sulfur content of feeds can also be determined by com-
busting the dry samples of feed or forage in an oxygen-rich
atmosphere at 1350°C. Any sulfur-containing compounds
break down, freeing sulfur, which is then oxidized to form
sulfur dioxide (SO,). The SOjgas produced during combus-
tion of the sample flows through an infrared detection cell
that measures the concentration of SO,. Though SO, is mea-
sured, it is most common to convert that determination back
into percentage of sulfur when reporting analyses of diet or
forage samples.
In some cases, such as water samples, a sulfide ion-spe-
cific electrode can be used to measure sulfide ions in aque-
ous solutions quickly and accurately. The sulfur atoms of the
sulfur compounds in water (sulfide and sulfates) are first
converted to inorganic sulfide by acid treatment so they will
be detected by the electrode. The presence of silver in the
water could interfere with the determination but because of
the extreme insolubility of silver sulfide, the two ions are
virtually never present in solution together (Ubuka, 2002).
REGULATION AND METABOLISM
Organic sulfur-containing compounds are absorbed
across the intestinal wall by specific transport processes. The
sulfur-containing amino acids are incorporated into proteins
or they are used to produce other organic sulfur-containing
compounds. Eventually, all these organic sulfur-containing
compounds will be catabolized to inorganic sulfate. Inor-
ganic sulfur compounds that might be in the diet such as
sulfides, sulfites, and sulfates are generally converted to sul-
fides or sulfates prior to absorption. Sulfate is a nonmetabo-
lizable strong anion and can add acidity to the fluids of the
body (see chapter on Minerals and Acid-Base Balance). In
ruminants, most dietary sulfur, whether ingested as amino
acids or inorganic sulfur, is reduced to sulfide within the
rumen by certain types of bacteria that use sulfur as an elec-
tron acceptor. Sulfide can be incorporated into microbial pro-
tein by certain types of bacteria or the sulfide can be ab-
sorbed into the portal circulation where it is quickly and
efficiently (in most cases) oxidized to sulfate in the liver.
Sulfates fed to animals are relatively well absorbed. Ru-
minants can absorb an estimated 77-87 percent of sulfur
from sodium sulfate or calcium sulfate (gypsum) (Bouchard
and Conrad, 1973). From studies of the effects of sulfur on
acid-base status it would appear that, on a molar basis,
sulfate is absorbed at about 30 percent the efficiency of
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374
MINERAL TOLERANCE OF ANIMALS
chloride (Goff, et al. 2004). Inorganic sulfur in the form of
elemental sulfur is poorly available for absorption by ani-
mals. It is about 35-65 percent as available for absorption as
sulfate (Henry and Ammerman, 1995) and is relatively in-
soluble in water. It is likely that some small proportion is
converted to sulfide, which would have deleterious effects if
not rapidly converted to sulfate by the liver.
Sulfur is taken up by tissue cells mainly in the divalent
state as sulfur-containing amino acids. These are then me-
tabolized via the quadrivalent state (sulfinic acids), and fi-
nally oxidized to the hexavalent fonn (sulfates). The great
majority of dietary sulfates entering the body or produced in
the body during catabolism of organic sulfur-containing
compounds are eventually excreted in the urine (Harrington
and Lemann, 1970; Magee et al., 2004). Inorganic sulfur,
absorbed across the intestinal tract, adds to the strong anion
sulfate in the blood and affects the acid-base balance of the
body as described previously.
SOURCES AND BIOAVAILABILITY
The primary sources of sulfur in the diet of most species
are the sulfur-containing amino acids. Plants can use inor-
ganic sulfur in the soil to produce methionine, thiamine, and
biotin and serve as an important source of sulfur-containing
compounds for vertebrates. Plants high in protein, such as
alfalfa, are about 0.3 percent sulfur, while relatively low pro-
tein corn silage is about 0. 14 percent. Meat and poultry prod-
ucts (especially feather meal) are much higher in protein and
also higher in sulfur-containing amino acids. Rendered meat
meal is about 0.51 percent sulfur and fish meal can be as
high as 1.16 percent sulfur (NRC, 2001). Corn gluten feed
and corn steep liquor (by-products of the refinement of corn
for ethanol), corn syrup, corn gluten, corn oil, and cornstarch
have gained popularity as livestock feeds. They tend to be
high in sulfur content (0.45 percent to 0.85 percent sulfur)
and due to their low prices they may comprise a large pro-
portion of the diet of some ruminants.
Typical diets for cattle and small ruminants that are ad-
equate in protein or that will provide adequate microbial-
derived protein contain about 0.20 percent sulfur. For horses,
diets that are adequate in protein contain about 0.15 percent
sulfur. For swine, the typical corn-soybean meal diet provid-
ing adequate protein for growth will be about 0.20 percent
sulfur. Dogs and cats are often fed diets that are formulated
with meat and tend to be higher in protein. These diets are
often as high as 0.50 percent sulfur depending on the amount
of meat in the diet.
Calcium sulfate (gypsum) and magnesium sulfate
(epsom salts) are used as calcium and magnesium sources
in animal diets. Potassium sulfate is used in ruminant diets
as a source of potassium for electrolyte balance and sulfur
for rumen bacteria. Ammonium sulfate is used in some di-
ets as an acidifying agent. The cationic trace minerals zinc,
copper, manganese, and iron are often added to diets as the
sulfate salts — primarily because the sulfate salts are soluble
in water and therefore, often are among the most
bioavailable of the inorganic forms of these trace minerals.
Many of the mineral supplements used to meet the phos-
phorus requirements of animals contain a significant
amount of sulfur. For instance, dibasic ammonium phos-
phate is about 2.16 percent sulfur and dicalcium phosphate
is approximately 1.14 percent sulfur.
There are six sulfiting agents (sulfur dioxide, sodium
and potassium metabisulfite, sodium and potassium
bisulfite, and sodium sulfite) currently being used to help
prevent spoilage and discoloration in foods, and these are
used almost exclusively in processed food products. These
agents have been banned by the Food and Drug Adminis-
tration for use on fresh fruits and vegetables that are meant
to be consumed raw and on fresh meat and poultry prod-
ucts. Sulfites are still used to help prevent black spot in
shrimp and its use in shrimp is supposed to be labeled if the
sulfite residue is 10 ppm or more. Certain humans are sen-
sitive to sulfites and have asthmatic attacks or headaches
following its ingestion. It is unknown if these symptoms
occur in animals. If one considers that the major threat of
sulfite residues for humans comes from red wines, it is un-
likely to be a major problem for animals.
TOXICOSIS
The toxicity of sulfur is highly dependent on the form of
the sulfur ingested. Elemental sulfur is generally very unre-
active and very innocuous in nonruminant species. It is also
less soluble in rumen fluid than other oxidized forms of sul-
fur and tends to be less toxic in ruminants as well, though
rumen bacteria are capable of further reducing elemental
sulfur to more toxic compounds, such as hydrogen sulfide.
Hydrogen sulfide (HjS) is an extremely toxic sulfur-con-
taining compound. Very low amounts of this gas can prove
rapidly fatal. Inhaled H2S is a particular concern for swine
confinement operations where the pigs are kept on slatted
floors above a manure pit where H,S may be produced dur-
ing anaerobic digestion of the manure. Death occurs shortly
after exposure of pigs to 470 ppm HjS in the atmosphere.
Levels as low as 15-20 ppm HjS inhaled over a period of
two months can cause fibrosis of pulmonary tissues
(O'Donoghue and Graessner, 1962). Production of HjS by
bacteria within the rumen can be fatal to ruminants and will
be discussed in depth in the section on ruminant
polioencephalomalacia.
There are many sulfur-containing compounds that can be
injurious to animals when ingested over the short or long
term. Plants of the Brassica family (kale, cabbage, broccoli)
are included as a major part of the ration of ruminants in
some parts of the world. These plants contain isothiocyanates
that can interfere with thyoperoxidase activity in the thyroid
gland, blocking thyroxine production and thus leading to
hypothyroidism and goiter. Kale poisoning, or a severe
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SULFUR
375
haemolytic anaemia, was discovered in cattle in Europe in
the 1930s, but its link with the hydrolytic product of S-me-
thyl cysteine sulfoxide was only shown years later (Smith,
1980). The effects of other bioactive sulfur-containing com-
pounds present in plants are reviewed by Stoewsand (1995)
and will not be considered further in this review. Humans
have figured out how to use sulfur-containing compounds
for biological warfare. For example, sulfur mustard killed
thousands of men and horses during the First World War and
was employed by Iraq against Iran from 1984-1987. It causes
severe local blistering burns if it touches the skin or is in-
haled (Rice, 2003).
Sulfur-containing organic compounds are commonly
found among the myriad compounds causing toxicosis in
animals maintained on pastures within oil fields. Cattle will
voluntarily ingest petroleum and chemicals used in the ex-
ploration, production, and transportation of crude petroleum
(Coppock et al., 1996). Sulfur-containing gases in oil fields
are irritating to the mucosa of the eye and respiratory tract.
One other sulfur compound deserves some mention. Dim-
ethyl sulfoxide (DMSO) is widely used in horses and other
animals as a topical anti-inflammatory (sometimes illegally).
It is capable of crossing the skin and entering the tissues
under the skin. It is also a very good solvent and can solubi-
lize substances that are not readily soluble in water. In and of
itself DMSO is not very toxic, even when ingested orally.
Because DMSO is a good solvent and is capable of crossing
the skin, it is sometimes used to drag other drugs across the
skin directly into the inflamed joint or other area of the body
for localized treatment. It is the combining of DMSO with
other substances that makes topical application of DMSO
potentially dangerous (Brayton, 1986). As an example, com-
bining DMSO with a topical counter-inflammatory joint
treatment containing mercury caused systemic mercury poi-
soning in a horse (Schuh et al., 1988).
The 1980 NRC publication Mineral Tolerance of Domes-
tic Animals presented an exhaustive review of the toxicities
of inhaled, intravenous, and subcutaneous doses of various
organic and inorganic sulfur compounds. This review will
only focus on toxicities caused by oral ingestion of inorganic
sulfur compounds and the sulfur-containing amino acids
(Table 28-1). Oral ingestion of sulfate salts such as calcium
sulfate or magnesium sulfate can also affect acid-base bal-
ance of the body. This aspect of sulfur toxicity is described
in the chapter entitled "Minerals and Acid-Base Balance."
Single Dose
There are few data on the toxicity of a single dose of
sulfur compounds in domestic species. At one time elemen-
tal sulfur, often referred to as "flowers of sulfur," was used
extensively in veterinary and human medicine as a purgative
and was thought to have a variety of curative properties.
Ales (1907) described a situation where 300 g of a flowers of
sulfur gruel had been administered to five horses to treat
"collar gall" — i.e., sores where the yoke or the harness collar
rubbed against the neck of the horse. Within three hours the
horses exhibited violent abdominal pain and colic, had a fetid
diarrhea, and collapsed. One died and the others recovered
over a period of days.
In a similar case, 20 yearling heifers were given about
250 g elemental sulfur mixed with a small amount of corn
grain as part of a "treatment" for ringworm. All animals de-
veloped a severe watery diarrhea and the "rotten egg" smell
characteristic of hydrogen sulfide was noted around the
cattle. Several of the heifers died within the first day with
more than half of the animals dying over the next three days
(Julian and Harrison, 1975).
Toxicity of Sulfur
It is commonly noted in studies with nonruminant species
that switching animals to a high sulfur diet or water source has
a cathartic effect, though wetter feces do not seem to affect
animal performance in and of themselves. There are no re-
ports of acute toxicosis (poor performance observed with less
than 10 days of consumption) for sulfur in nonruminant spe-
cies. In ruminants, the data implicating high sulfur diets as the
cause of death from polioencephalomalacia does not warrant
distinguishing between acute and chronic effects of high sul-
fur exposure. Ruminants and nonruminants will be consid-
ered separately as the etiology of toxicosis is very different in
the two groups of animals.
Nonruminants
Pigs are able to consume diets that are up to 0.42 percent
sulfur (supplemented with potassium sulfate) for 4 months
with no deleterious effects (Dale et al., 1973). Diets using
higher dietary levels of sulfur have not been reported. Pig-
lets and sows can tolerate drinking water that is 3,000 mg
sulfate/L (1,000 mg sulfur/L) with no deleterious effects on
growth or reproduction. These levels of sulfate in the water
do have a cathartic effect and increase the water content of
the feces, but this does not affect the health of the pig (Pater-
son et al., 1979).
Leach et al. (1960) found that increasing dietary sulfur
from 0.41 to 1.20 percent decreased growth rate of chicks
dramatically. When using calcium sulfate (gypsum) to in-
crease the dietary sulfur, these results might be explained
away as being due to induction of a metabolic acidosis in the
chicks (see chapter on Minerals and Acid-Base Balance).
However, similar results were observed when a mixture of
sodium and potassium sulfate, which would not be expected
to acidify the chick's blood, was added to the diet, suggest-
ing an effect of sulfur on growth independent of effects on
acid-base balance. Egg production decreased in laying hens
given drinking water that was 10,000 mg sulfate/L (3,333
mg S/L) when magnesium sulfate was used as the source of
sulfate, but not if sodium sulfate was used to supply the
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376
MINERAL TOLERANCE OF ANIMALS
sulfate. Egg production was markedly reduced when hens
were given 12,000 mg sulfate/L drinking water with sodium
sulfate as the source of sulfate (Krista et al., 1961). Adams
et al. (1975) titrated the effects of drinking water with 250,
1,000, 4,000, and 16,000 mg sulfate/L on laying hen perfor-
mance. They used either magnesium sulfate or sodium sul-
fate as the source of sulfate. Feed consumption was signifi-
cantly depressed and egg production was decreased in birds
given water 4,000 mg sulfate/L, regardless of sulfate
source. However, nearly 15 percent of birds given 4,000 mg
sulfate/L water using magnesium sulfate as the source of
sulfate died, while sodium sulfate did not kill the birds. All
birds given 16,000 mg sulfate/L water died.
The use of sulfites to preserve meat meant for pet food is
not without problems (and is not permitted by many coun-
tries). The addition of sulfur dioxide to meat can rapidly in-
activate thiamine within the rest of the diet. A cat with aller-
gic dermatitis was fed a diet of fresh meat preserved with
sulfites and a multivitamin supplement for 38 days to ex-
clude food allergy as a cause of its dermatopathy. The cat
died as a result of acute thiamine deficiency (Steel, 1997).
Dogs and cats consuming meat preserved with sodium
metabisulfite containing from 400 to 1,480 mg sulfur diox-
ide/kg developed ataxia, depression, and in some cases con-
vulsions over a period of several months (Studdert and
Labuc, 1991). Although sulfur dioxide is highly regulated in
meat meant for human consumption, some meat intended for
pet foods is still preserved with it, usually by soaking it in a
brine of sodium metabisulfite.
Little is known of sulfur toxicity in fish. Sulfur dioxide
emitted from smokestacks, and its deposition as sulfuric acid
rain, has impaired surface water quality in the Adirondack
and Catskill regions of New York by lowering pH levels,
decreasing acid-neutralizing capacity, and increasing alumi-
num concentrations — all of which are thought to contribute
to reduced diversity and abundance of aquatic species in
lakes and streams. There are also linkages between acidic
deposition and fish mercury contamination and eutrophica-
tion of estuaries (Driscoll et al., 2003).
Methionine and Cysteine Toxicity
Methionine is approximately 21.5 percent sulfur and cys-
teine is about 26.5 percent sulfur. The addition of 5 g me-
thionine/kg diet to a basal ration that was 0.35 percent me-
thionine and 0.35 percent cysteine (bringing total diet sulfur
to about 0.17 percent) was fed to growing chicks with no
deleterious effects. However, increasing the basal diet me-
thionine to 1.35 percent caused a 40 percent decrease in
growth of the chicks (Katz and Baker, 1975). The added
methionine raised total sulfur in the diet to just 0.38 per-
cent — a dietary sulfur level Leach et al. (1960) used as a
level for the control diet in their studies, suggesting the tox-
icity of methionine is independent of the sulfur the methion-
ine brings to the diet.
Cats given DL-methionine (1 g/kg BW/day) developed
severe hemolytic anemia with marked increase of methemo-
globin (MetHb) concentration and Heinz-body formation 6-
10 days after treatment began (Maede et al., 1987).
Ruminants and Polioenceplialomalacia
Ruminants comprise the principal species likely to de-
velop sulfur toxicosis, which most commonly presents as
rapidly developing central nervous system symptoms such
as ataxia, blindness, and seizures, often followed by death.
These adverse effects of sulfur in the diet or water are quite
different from the adverse effects of sulfur in nonruminants,
in which sulfate entering the small and large intestine causes
an osmotic diarrhea as the most significant observable clini-
cal finding. Brain lesions are most commonly described as
polioencephalomalacia — swelling of the cerebrum, evi-
denced by flattened gyri and shallow sulci. The cerebral cor-
tex may be thinned. The distribution is symmetrical. Histo-
logical section may reveal a pale layer near the junction of
the gray and white matter. The affected areas of the cortex
will fluoresce under ultraviolet light.
Rumen microbes generally convert a good proportion of
the dietary sulfur to sulfide, which can be absorbed and
converted to sulfate by the liver or go on to form hydrogen
sulfide or sulfur dioxide (which are gases) within the ru-
men. Dougherty et al. (1965) discovered that during the
eructation process ruminants normally inhale rumen gases
into the lung. They further demonstrated that large amounts
of hydrogen sulfide generated in the rumen could be ab-
sorbed across the lungs during eructation and would cause
symptoms of central nervous system disruption in the
sheep. When they placed high amounts of hydrogen sulfide
into the rumen of a sheep with a blocked trachea so that
rumen gases could not be drawn into the lungs, there were
no clinical signs observed, providing direct evidence that
inhalation of the rumen gases was a required factor con-
tributing to the appearance of clinical symptoms. The hy-
drogen sulfide gas does not cross the rumen wall and enter
the blood. Hydrogen sulfide is a potent inhibitor of cyto-
chrome C oxidase, vital to cellular respiration (Beauchamp
et al., 1984), and since the brain has a very high energy
requirement it is logical that sulfur intoxication would be
associated with symptoms of central nervous system fail-
ure and brain lesions.
Hydrogen sulfide can build up in the gas cap above the
rumen fluid, with HjS concentration in these gases being
many fold higher than concentrations of H,S in the rumen
fluid (Gould et al., 1997; Loneragan et al., 1998). Rumen gas
HjS concentrations peaked about 1-3 weeks after cattle were
placed on a higher sulfur diet (0.37 percent sulfur from so-
dium sulfate) and this corresponded to the time when clini-
cal symptoms appeared in the cattle. After this peak, hydro-
gen sulfide levels in rumen gas decreased and no further
clinical cases of polioencephalomalacia developed, which
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SULFUR
377
must reflect some kind of adaptation of rumen microbes to
the fiigfier-sulfur diets (Gould et al., 1997).
Other workers have demonstrated that sulfur dioxide can
cleave thiamine. Cleavage of thiamine is suggested as a cause
of thiamine deficiency in the ruminant, leading to
cerebrocortical necrosis (Edwin and Jackman, 1982). The
lesions of polioencephalomalacia commonly described dur-
ing sulfur intoxication of ruminants are similar, but not iden-
tical, to the cerebrocortical necrosis associated with thiamine
deficiency (Jeffrey et al., 1994). Further, most cases of
polioencephalomalacia attributed to sulfur intoxication are
not accompanied by decreased blood thiamine concentra-
tions (Gould, 2000).
The SOj generated in the rumen will also react with water
in the rumen to form sulfuric acid, which is thought to be
responsible for hemorrhagic lesions in the wall of the rumen
above the rumen fluid level and abdominal pain in animals
dying of acute sulfur intoxication (Julian and Harrison, 1975;
Kandylis, 1984).
Most reports of polioencephalomalacia are made in beef
cattle or lambs on high concentrate diets. Gould et al. (1991)
reported that 5 of 9 growing steers fed a diet that was 0.36
percent sulfur developed polioencephalomalacia. Low et al.
(1996) reported that 21 of 70 growing lambs fed a 0.43 per-
cent sulfur high concentrate diet developed symptoms or le-
sions of polioencephalomalacia. Zinnetal. (1997) found that
increasing diet sulfur from 0.20 to 0.25 percent using ammo-
nium sulfate as the sulfur source caused a reduction in feed
intake and average daily gain and reduced carcass quality of
feedlot steers. It is not known if the ammonium added to the
diet, which was primarily composed of steam flaked corn,
caused this response or if the sulfate was truly responsible
for this response. Ammonium added to diets of neutral or
alkaline pH is sometimes converted to ammonia, which is
volatile and irritating to cows and as a consequence reduces
intake of the diet. Rumsey et al. (1978) used elemental sul-
fur as a sulfur source and reported no problems in feedlot
steers fed a 0.42 percent sulfur diet, but steers fed a 0.98
percent sulfur diet went completely off feed. Slyter et al.
(1988) fed purified diets that were up to 1.72 percent sulfur
from elemental sulfur to newly weaned calves for up to 50
days with no deleterious effects. Dairy cows are rarely re-
ported to suffer from polioencephalomalacia, despite the fact
that addition of sulfate (in the form of anionic salts) to bring
diet sulfur to 0.5 percent is commonly practiced as a means
of controlling milk fever in cows in late gestation (Block,
1984; Oetzel et al., 1988; Gaynor et al., 1989).
Water coming from wells can often contain high concen-
trations of sulfur, usually in the form of sulfate. Water qual-
ity reports typically express sulfur content of water in units
of sulfate/L. Concentrations as high as 5,000 mg sulfate/L
are not uncommon (NRC, 1977). Embry et al. (1959) failed
to observe any adverse effects in cattle drinking water that
was 7,000 mg sodium sulfate/L (4,760 mg sulfate/L) but
observed toxicosis in cattle drinking 10,000 mg sodium sul-
fate/L (6,800 mg sulfate/L). A series of studies (Weeth and
Hunter, 1971; Weeth and Capps, 1972) examined the effect
of drinking water with added sodium sulfate on feed intake
and water intake of growing beef heifers fed predominantly
hay rations, culminating in the conclusion that 2,500 mg sul-
fate/L (or 834 mg sulfur/L) represents the maximal safe con-
centration of sulfate in drinking water (Digest! and Weeth,
1976). However the study of Loneragan et al. (2001) dem-
onstrated that significant decreases in BW and carcass yield
occurred when drinking water for feedlot steers was 1,219
mg sulfate/L but not when water was 582 mg sulfate/L.
Miscellaneous Considerations
High dietary sulfur can reduce the availability of trace
minerals to ruminants, probably through formation of in-
soluble sulfides and other complexes with the trace minerals
within the rumen. The copper-sulfur-molybdenum interac-
tion in the rumen can form copper tetrathiomolybdate, which
renders the copper unavailable to the animal. Increasing diet
sulfur from 0.2 to 0.4 percent can cause a 50 percent reduc-
tion in copper absorbed from the diet (Suttle, 1991). Simi-
larly, increasing diet sulfur content reduced true digestibility
of dietary selenium from 50.5, when no sulfate was added to
the diet, to 46.0, and to 42.3 percent as diet sulfur was in-
creased by 0.2 and 0.4 percent, respectively. The high di-
etary sulfur level placed these cows in negative selenium
balance (Ivancic and Weiss, 2001).
Sodium metabisulfite and sodium sulfite are also used to
preserve silage, especially wilted grass or alfalfa silage in-
tended for ruminants. When properly conducted, the major-
ity of sulfur dioxide produced from the sulfite is converted
to sulfuric acid, bringing the pH down to preserve the ensiled
material. Cows receiving 9-10 g sulfur per day, as sulfur
dioxide incorporated into their diet, exhibited no deleterious
effects (Weigand et al., 1972). However, adding 15 g sulfur
from sodium sulfite decreased rumen production of acetate,
which was associated with a reduction in milk fat synthesis
(Alhassan et al., 1969).
Methionine Toxicity
Methionine imbalance can also be toxic to ruminants. Abe
et al. (2000) examined the occurrence of methionine imbal-
ance and toxicity using thirty 70- and 100-kg bull calves.
The animals had been trained to maintain reflex closure of
the reticular groove after weaning at 5 weeks of age. Calves
received a corn-soybean meal diet. Postruminal administra-
tion of 6 g of DL-methionine each day increased ADG, feed
intake, gain/feed, and nitrogen retention compared with a
control group receiving nitrogen-free supplement. Adminis-
tration of 12 g of DL-methionine per day did not improve
these variables. Addition of 18 and 24 g methionine per day
resulted in BW loss and decreased gain/feed and nitrogen
utilization efficiency. In a study by Satter et al. (1975), the
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378
MINERAL TOLERANCE OF ANIMALS
toxicity of DL-metliionine and methionine hiydroxy analog
infused into tfie rumen or abomasum was gauged by relative
feed consumption. A continuous intraruminal infusion of at
least 3 days' duration of DL-methionine equivalent to about
2.5 percent or more of dietary DM intake was required to
reach a toxic amount. This was approximately four times the
amount necessary when it was infused into the abomasum.
Methionine hydroxy analog equivalent to about 1 percent or
more of dietary DM intake was toxic when infused into ei-
ther the rumen or abomasum. This is in large excess of the
amount of methionine analog typically added to diets.
Factors Affecting Toxicity
Nonruminants are relatively secure from the acute mor-
tality from sulfur toxicosis observed in ruminants. Gener-
ally, nonruminants respond to excessive dietary sulfur by
reducing feed intake. Within ruminants there is great dispar-
ity in dietary levels at which toxicosis is observed. Several
factors are likely involved. Feedlot animals are often fed di-
ets that are 90 percent concentrate and very low in fiber. In
contrast, dairy cows are rarely fed diets that are more than 60
percent concentrate. Readily fermentable carbohydrate in the
diet appears to increase the activity of sulfate, reducing bac-
teria and causing more H,S to be produced. High grain diets
also reduce rumen pH, which can also increase the toxicity
of dietary sulfur. HjS trapped in solution within the rumen
fluid becomes less soluble as the pH decreases, causing the
amount of HjS in the gas cap to increase (Gould, 2000).
Diets that are 0.4 percent sulfur can induce polio-
encephalomalacia in feedlot cattle fed on high concentrate,
low fiber diets. Yet dairy cattle have commonly been fed
0.5 percent sulfur diets with no reports of polio-
encephalomalacia. The data suggest that the tolerance for
dietary sulfur is dependent on dietary concentrate content.
Spears and Lloyd (2005) found that 0.46 percent sulfur diets
were well tolerated in corn silage-based diets, but caused a
dramatic reduction in feed intake and gain when a 0.46 per-
cent sulfur high concentrate diet, typical of feedlot diets, was
administered. Water sulfate tolerance seems to also be
dependent on diet. Loneragan et al. (2001) demonstrated a
dramatic reduction in growth and carcass yield when water
sulfate exceeded 600 mg/L. These steers were fed a finish-
ing ration that was a high-concentrate diet. In the study of
Digesti and Weeth (1976), heifers fed a grass hay diet ad
libitum could drink water that was 2,500 mg sulfate/ L with
no health or growth problems.
The mineral content of the diet may also play a role in the
susceptibility to polioencephalomalacia from dietary sulfur.
Gould et al. (1991) demonstrated that 0.36 percent sulfur
feedlot diets could result in polioencephalomalcia. In this
study it may be important to note that the basal ration barely
met the animals' requirement for copper. Copper and some
other trace minerals have a high affinity for sulfides. Though
this generally renders the trace mineral unavailable, it may
provide some small degree of protection from
polioencephalomalacia by reducing conversion of sulfide
into neurotoxic hydrogen sulfide within the rumen.
When water is an important source of dietary sulfur, the
risk of polioencephalomalacia may be increased during hot
weather as animals drink more water.
TISSUE LEVELS
Measurement of ruminal gas sulfide concentration is a
relatively sensitive indicator of the predilection of cattle to
develop polioencephalomalacia. Rumen gas sulfide is nor-
mally less than 500 mg/L but typically rises above 3,000 mg/L
in cows developing polioencephalomalacia (Gould et al.,
1997; Loneragan et al., 1998). Blood sulfur in cattle is
between 1.5 and 1.8 mg/ml. The concentration of sulfur in
soft tissues of the body is generally between 1,000 and
2,000 mg/kg WW and does not change appreciably in
response to diet (Table 28-2). Tissue sulfur content consists
of sulfur contained within methionine and cysteine of tissue
proteins and sulfur present as sulfate within tissues.
MAXIMUM TOLERABLE LEVELS
The maximum tolerable level of sulfur in diets of
nonruminant and ruminant animals will be considered sepa-
rately. For nonruminant (simple-stomached) animals the
criteria for determining the maximum tolerable level of sul-
fur is the highest dietary level that can be safely fed without
affecting health or performance. When the maximum toler-
able level of dietary sulfur is exceeded, the typical reaction
of these animals is a reduction in feed intake, which may or
may not be accompanied by osmotic diarrhea. It is difficult
to find data to justify a maximum tolerable level for dietary
or water sulfur concentration in nonruminant species. For
swine the maximum tolerable dietary sulfur level is 0.4 per-
cent. Swine can tolerate water that is 3,000 mg sulfate/L
(1,000 mg sulfur/L). Dogs and cats fed diets consisting pri-
marily of meat will generally consume diets that are 0.5 per-
cent sulfur with no ill effects. Dogs and cats fed diets com-
posed of large amounts of fish may be receiving diets that
are even higher in sulfur. For example, menhaden fish meal
is 1.16 percent sulfur (NRC, 2001). No reported studies ex-
amined the effects of high dietary sulfur in these species.
Therefore since cats and dogs typically consume diets that
are 0.5 percent sulfur, the maximum tolerable level of sulfur
in the diet of these species will be set at 0.6 percent.
Data on poultry only exist for chickens but it is reason-
able to assume most birds will respond similarly to the
chicken. Chicks can safely tolerate 0.4 percent sulfur diets.
Their tolerance may be higher but in the only existing study,
the next highest dose of sulfur tested was 1.2 percent and
this depressed growth (Leach et al., 1960). Though data of
Kristaet al. (1961) suggest chickens may tolerate as much as
10,000 mg sulfate in drinking water, the data of Adams et al.
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SULFUR
379
(1975) do not justify setting this level as the maximal toler-
able level. Because Adams et al. (1975) demonstrated
reduced performance when water contained 4,000 mg
sulfate/L, it seems prudent to set the maximum tolerable level
for sulfate in drinking water of birds to 1,000 mg/L (333 mg
sulfur/L), based on the upper level tested in Adams' study
(1975).
Cattle fed diets typical of beef animals in the finishing
phase have a lower tolerance for sulfur, based on avoidance of
polioencephalomalacia or reduced weight gain, than do cattle
fed higher forage diets. Therefore two maximum tolerable lev-
els for sulfur are applicable — depending on the diet the animal
is being fed. Cattle and sheep fed diets with less than 15 per-
cent forage are at risk of polioencephalomalacia when diet
sulfur is as low as 0.35 percent. Therefore the maximum toler-
able level of sulfur in diets that are more than 85 percent con-
centrate is 0.30 percent. Drinking water for cattle, and prob-
ably other ruminants, fed these high concentrate diets should
contain less than 600 mg sulfate/L (200 mg sulfur/L). The
maximum tolerable dietary sulfur level based on avoidance of
polioencephalomalacia for cattle and other ruminants fed di-
ets with at least 40 percent forage is 0.50 percent sulfur. Cattle
and other ruminants on these higher forage diets can safely
drink water that is 2,500 mg sulfate/L (834 mg sulfur/L). Data
on dietary sulfur interactions with copper and selenium avail-
ability in ruminants would dictate that sulfur content of cattle
diets be limited to the requirement of the animal, which is 0.2
percent dietary sulfur for dairy and 0.15 percent in beef cattle
and other ruminants. Though this may be an important factor
affecting trace mineral absorption, the data do not warrant
using this criterion when determining the maximum tolerable
dietary sulfur level.
FUTURE RESEARCH NEEDS
The dearth of experimental evidence available does not
allow a very precise definition of the maximum tolerable
dietary sulfur level for many species. For instance, there are
no published studies on the effects of dietary or water sulfur
content on the health and performance of horses. Also, the
maximum tolerable sulfur levels for nonruminant species
described in this chapter are often well below the levels of
dietary sulfur known to produce deleterious effects. How-
ever, no studies that have examined these intermediate expo-
sures to dietary sulfur exist.
Further work may elucidate the role diet has on the high
susceptibility of feedlot beef animals to sulfur in their diets
and drinking water. Since rumen bacterial population shifts
are implicated in the greater susceptibility to sulfur toxicity
of ruminants on high concentrate diets, identification of the
rumen microbes responsible for hydrogen sulfide generation
in the rumen may suggest methods for protecting the cattle
from polioencephalomalacia. For example, a practical un-
answered question concerns the effect monensin might have
on sulfur toxicity in cattle.
SUMMARY
Excessive dietary sulfur is rarely a practical concern in
nonruminant species. Ingredients used to formulate rations
for these species would not be expected to pose a risk of the
animal manifesting sulfur toxicosis. Even in cattle fed feed-
lot finishing diets, where death from polioencephalomalacia
can occur with 0.35 percent sulfur diets, it is uncommon for
feedstuffs to cause dietary sulfur to exceed 0.25 percent.
However, in many sections of the country, the water that
animals are forced to drink can be very high in sulfate. From
a practical standpoint water represents the greatest source of
exposure of animals to sulfur. When cattle are fed high con-
centrate diets, water sulfur concentrations in excess of
200 mg/L can be associated with reduced performance. In
contrast, finishing swine on similar diets can tolerate water
that is 1,000 mg sulfur/L.
REFERENCES
Abe, M., H. Okada, D. Matsumura, H. Sato, M. Funaba, and T. Iriki. 2000.
Methionine imbalance and toxicity in calves. J. Anim. Sci. 78:2722-2730.
Adams, A.W., F. E. Cunningham, and L. L. Munger. 1975. Some effects on
layers of sodium sulfate and magnesium sulfate in their drinking water.
Poult. Sci. 54:707-714.
Ales. 1907. Case of poisoning by sulphur in the horse. Vet. J. 63:524.
Alhassan, W. S., L. F. Krabill, and L. D. Satter. 1969. Manipulation of the
ruminal fermentation. I. Effect of sodium sulfite on bovine ruminal fatty
acid concentration and milk composition. J. Dairy Sci. 52:376-379.
Anderson, D. M., and S. C. Stothers. 1978. Effects of saline water high in
sulfates, chlorides and nitrates on the performance of young weanling
pigs. J. Anim. Sci. 47:900-907.
Anderson, J. O., R. E. Warnick, and R. K. Dalai. 1975. Replacing dietary
methionine and cystine in chick diets with sulfate or other sulfur com-
pounds. Pouh. Sci. 54:1122-1128.
Beauchamp, R. O., Jr., J. S. Bus, J. A. Popp, C. J. Boreiko, and D. A.
Andjelkovich. 1984. A critical review of the literature on hydrogen sul-
fide toxicity. Crit. Rev. Toxicol. 13:25-97.
Block, E. 1984. Manipulating dietary anions and cations for prepartum dairy
cows to reduce incidence of milk fever. J. Dairy Sci. 67:2939—2948.
Bouchard, R., andH. R. Conrad. 1973. Sulfur requirement of lactating dairy
cows. II. Utilization of sulfates, molasses, and lignin-sulfonate. J. Dairy
Sci. 56:1429-1434.
Brayton, C. F. 1986. Dimethyl sulfoxide (DMSO): a review. Cornell Vet.
76:61-90.
Coppock, R. W., M. S. Mostrom, E. L. Stair, and S. S. Semalulu. 1996.
Toxicopathology of oil field poisoning in cattle; a review. Vet. Hum.
Toxicol. 38:36-^2.
Dale, S. E., R. C. Ewan, V. C. Speer, and D. R. Zimmerman. 1973. Copper,
molybdenum, and sulfate interaction in young swine. 1973. J. Anim.
Sci. 37:913-917.
Digesti, R. D., and H. J. Weeth. 1976. A defensible maximum for inorganic
sulfate in drinking water of cattle. J. Anim. Sci. 42:1498—1502.
Dougherty, R. W., C. H. Mullenax, and M. J. Allison. 1965. Physiological
phenomena associated with eructation in ruminants. P. 159 in Physiol-
ogy of Digestion in the Ruminant, R. W. Dougherty, ed. Washington,
D.C.: Butterworths.
DriscoU, C. T., K. M. Driscoll, M. J. Mitchell, and D. J. Raynal. 2003.
Effects of acidic deposition on forest and aquatic ecosystems in New
York State. Environ. Pollut. 123:327-336.
Edwin, E. E., and R. Jackman. 1982. Ruminant thiamine requirement in
perspective. Vet. Res. Commun. 5:237-250.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
350
MINERAL TOLERANCE OF ANIMALS
Embry, L. B., M. A. Hoelscher, and R. C. Wahlstrom. 1959. Salinity and
livestock water quality. SD Agric. Exp. St. Bull. 481:5-9.
Freeman, D. E., P. L. Ferrante, and J. E. Palmer. 1992. Comparison of the
effects of intragastric infusions of equal volumes of water, dioctyl so-
dium sulfosuccinate, and magnesium sulfate on fecal composition and
output in clinically normal horses. Am. J. Vet. Res. 53:1347—1353.
Gaynor, P. J., F. J. Mueller, J. K. Miller, N. Ramsey, J. P. Goff, and R. L.
Horst. 1989. Parturient hypocalcemia in jersey cows fed alfalfa haylage-
based diets with different cation to anion ratios. J. Dairy Sci. 72:2525—
2531.
Goff, J. P., R. Ruiz, and R. L. Horst. 2004. Relative acidifying activity of
anionic salts commonly used to prevent milk fever. J. Dairy Sci.
87:1245-1255.
Gould, D. H. 2000. Update on sulfur-related polioencephalomalacia. Vet.
Clin. N. Am. Food Anim. Pract. 16:481^96.
Gould, D. H., B. A. Cummings, and D. W. Hamar. 1997. In vivo indicators
of pathologic ruminal sulfide production in steers with diet-induced
polioencephalomalacia. J. Vet. Diagn. Invest. 9:72-76.
Gould, D. H., M. M. McAllister, J. C. Savage, and D. W. Hamar. 1991.
High sulfide concentrations in rumen fluid associated with nutritionally
induced polioencephalomalacia in calves. Am. J. Vet. Res. 52:1164—
1169.
Harrington, J. T., and J. Lemann, Jr. 1970. The metabolic production and
disposal of acid and alkali. Med. Clin. N. Am. 54:1543-1554.
Henry, P. R., and C. B. Ammerman. 1995. Sulfur bioavailability. In
Bioavailability of Nutrients for Animals: Amino Acids, Minerals, Vita-
mins, C. B. Ammerman, D. H. Baker, and A. J. Lewis, eds. San Diego,
CA: Academic Press.
Ivancic, J., Jr., and W. P. Weiss. 200 1 . Effect of dietary sulfur and selenium
concentrations on selenium balance of lactating Holstein cows. J. Dairy
Sci. 84:225-232.
Jeffrey, M., J. P. Duff, R. J. Higgins, V. R. Simpson, R. Jackman, T. O.
Jones, S. C. Mechie, and C. T. Livesey. 1994. Polioencephalomalacia
associated with the ingestion of ammonium sulphate by sheep and cattle.
Vet. Rec. 34:343-348.
Julian, R. J., and K. B. Harrison. 1975. Sulphur poisoning in cattle. Can.
Vet. J. 16:28-29.
Kandylis, K. 1984. Toxicology of sulfur in ruminants: review. J. Dairy Sci.
67:2179-2187.
Katz, R. S., and D. H. Baker. 1975. Toxicity of vai'ious organic sulfur com-
pounds for chicks fed crystalline amino acid diets containing threonine
and glycine at their minimal dietary requirements for maximal growth.
J. Anim. Sci. 41:1355-1361.
Krista, L. M., C. W. Carlson, and O. E. Olsen. 1961. Some effects of saline
waters on chicks, laying hens, poults, and ducklings. Poult. Sci.
40:938-944.
Leach, R. M., T. R. Ziegler, and L. C. Noms. 1960. The effect of dietary
sulfate in the growth rate of chicks fed a purified diet. Poult. Sci.
39:1577-1582.
Loneragan, G. H., D. H. Gould, R. J. Callan, C. J. Sigurdson, and D. W.
Hamar. 1998. Association of excess sulfer intake and an increase in
hydrogen sulfide concentrations in the ruminal gas cap of recently
weaned beef calves with polioencephalomalacia. J. Am. Vet. Med
Assoc. 213:1599-1604.
Loneragan, G. H., J. J. Wagner, D. H. Gould, F. B. Garry, andM. A. Thoren.
2001. Effects of water sulfate concentration on performance, water
intake, and carcass characteristics of feedlot steers. J. Anim. Sci.
79:2941-2948.
Low, J. C, P. R. Scott, F. Howie, M. Lewis, J. FitzSimons, and J. A. Spence.
1996. Sulphur-induced polioencephalomalacia in lambs. Vet. Rec.
138:327-329.
Maede, Y., T. Hoshino, M. Inaba, and S. Namioka. 1987. Methionine toxi-
cosis in cats. Am. J. Vet. Res. 48:289-292.
Magee, E. A., R. Curno, L. M. Edmond, and J. H. Cummings. 2004. Contri-
bution of dietary protein and inorganic sulfur to urinary sulfate: toward
a biomarker of inorganic sulfur intake. Am. J. Clin. Nutr. 80:137-142.
NRC (National Research Council). 1977. Drinking Water and Health.
Washington, D.C.: National Academy Press.
NRC. 2001. Nutrient Requirements of Dairy Cattle, 7th rev. ed. Washing-
ton, D.C.: National Academy Press.
O'Donoghue, J. G., and F. E. Graessner. 1962. Effects of sulfur dioxide on
guinea pigs and swine. Can. J. Comp. Med. Vet. Sci. 26:255.
Oetzel, G. R., J. D. Olson, C. R. Curtis, and M. J. Fettman. 1988. Ammo-
nium chloride and ammonium sulfate for prevention of parturient pare-
sis in dairy cows. J. Dairy Sci. 71:3302-3309.
Paterson, D. W., R. C. Wahlstrom, G. W. LibaL and O. E. Olson. 1979.
Effects of sulfate in water on swine reproduction and young pig perfor-
mance. J. Anim. Sci. 49:664—667.
Rice, P. 2003. Sulphur mustard injuries of the skin. Pathophysiology and
management. Toxicol. Rev. 22:1 1 1-118.
Rumsey, T. S. 1978. Effects of dietary sulfur addition and Synovex-S ear
implants on feedlot steers fed an all-concentrate finishing diet. J. Anim.
Sci. 46:463.
Sasse, C. E., and D. H. Baker. 1974. Sulfur utilization by the chick with
emphasis on the effect of inorganic sulfate on the cystine-methionine
interrelationship. J. Nutr. 104:244-251.
Salter, L. D., R. L. Lang, J. W. Van Loo, M. E. Carlson, and R. W. Kepler.
1975. Adverse effect of excess methionine or methionine hydroxy ana-
log on feed consumption in cattle. J. Dairy Sci. 58:521-525.
Schuh, J. C, C. Ross, and C. Meschter. 1988. Concurrent mercuric blister
and dimethyl sulphoxide (DMSO) application as a cause of mercury
toxicity in two horses. Equine Vet. J. 20:68-71.
Slyter, L. L., W. Chalupa, and R. R. Oltjen. 1988. Response to elemental
sulfur by calves and sheep fed purified diets. J. Anim. Sci. 66:1016-1027.
Smith, R. H.. 1980. Kale poisoning: the brassica anaemia factor. Vet. Rec.
107:12-15.
Soares, J. H., Jr. 1974. Experiments on the requirement of inorganic sulfate
by the chick. Poult. Sci. 53:246-252.
Spears, J. W., and K. E. Lloyd. 2005. Effect of dietary sulfur and sodium
bicarbonate on performance of growing and finishing steers. J. Anim.
Sci. 83 (Supplement l):(Abstr.).
Steel, R. J. 1997. Thiamine deficiency in a cat associated with the preserva-
tion of "pet meat" with sulphur dioxide. Aust. Vet. J. 75:719—721.
Stoewsand, G. S. 1995. Bioactive organosulfur phytochemicals in Brassica
oleracea vegetables — a review. Food Chem. Toxicol. 33:537-543.
Studdert, V. P., and R. H. Labuc. 1991. Thiamine deficiency in cats and
dogs associated with feeding meat preserved with sulphur dioxide. Aust.
Vet. J. 68:54-57.
Suttle, N. F. 1991. The interactions between copper, molybdenum, and sul-
phur in ruminant nutrition. Annu. Rev. Nutr. 11:121-140.
Ubuka, T. 2002. Assay methods and biological roles of labile sulfur in ani-
mal tissues. J. Chromatogr. B Analyt. Technol. Biomed. Life Sci.
781:227-249.
USGS (U.S. Geological Survey). 2004. Mineral Commodity Summaries.
Washington, D.C.: U.S. Department of the Interior, United States Gov-
ernment Printing Office. P. 162.
Weeth, H. J., and D. L. Capps. 1972. Tolerance of growing cattle for sul-
fate-water. J. Anim. Sci. 34:256-260.
Weeth, H. J., and J. E. Hunter. 1971. Drinking of sulfate-water by cattle. J.
Anim. Sci. 32:277-281.
Weigand, E., M. Kirchgessner W. Granzer and K. Ranfft. 1972. Feeding
large amounts of sulfite to dairy cows. Tolerance to SO-, and SOj con-
tent of milk. Zentralbl. Veterinarmed. A. 19:490-501.
Zinn, R. A., E. Alvarez, M. Mendez, M. Montano, E. Ramirez, and Y. Shen.
1997. Influence of dietary sulfur level on growth performance and di-
gestive function in feedlot cattle. J. Anim. Sci. 75:1723-1728.
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29
Tin
INTRODUCTION
Tin (Sn) has an atomic number of 50 and appears in group
4A of the periodic table at the boundary between metals and
nonmetals. It exists naturally in both the divalent (stannous
or tin 2+) and tetravalent (stannic or tin 4+) oxidation states.
Industrially important forms of inorganic tin include stan-
nous chloride, stannic oxide, and stannous fluoride, and
industrially important compounds containing organic tin in-
clude dimethyltin, dibutyltin, tributyltin, dioctyltin,
triphenyltin, and trichlohexyltin families (ATSDR, 2003).
Tin is a relatively scarce element; its abundance in the
Earth's crust is about 2 mg/kg. The major sources of tin in
2002 were mines in China, Peru, and Indonesia, and recy-
cling of scrap tin (Carlin, 2002). No tin has been mined in
the United States since 1993.
Tin is a soft, malleable metal that is used as a protective
coating for iron and steel cans and containers (2 1 percent of
total use). Tin is also a component of various alloys, includ-
ing pewter, brass, the solders for joining pipes or electrical/
electronic circuits, and bearing alloys. Its use in electrical
solders, construction, and transportation constitutes 24, 11,
and 14 percent of total use, respectively (Carlin, 2002).
Organotin compounds are used in various pesticides and as
stabilizers of plastics (Kumpulainen and Koivistoinen,
1977). Tin is used as an anticaries agent in dentifrices and as
a reducing agent of ^'"technetium for nuclear medicine
(Schafer and Femfert, 1984).
ESSENTIALITY
Schwarz et al. (1970) reported that low levels of tin (0.5-
2 mg/kg diet of tin) supplied as stannic sulfate promoted
growth in suboptimally growing rats fed purified amino acid-
based diets and housed in plastic isolator systems. These
observations have not been confirmed and experts doubt that
tin is essential because of other limitations in the diets that
Schwarz fed to rats (Schroeder et al., 1964; Mertz, 1986).
Limited data suggest that tin has cariostatic properties.
Rats fed diets supplemented with 15 to 75 mg/kg diet of tin
were found to develop fewer caries in some studies
(McDonald and Stookey, 1973; Stookey et al., 1974). Tin
fluoride was found to have more antiplaque properties
against Streptococcus mutans than other fluoride compounds
(Ferretti et al., 1982; Leverett et al., 1984).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Prior to the mid-1980s the preferred methods for analyses
of inorganic tin were spectrophotometric methods that re-
quired separation of the tin by distillation, precipitation, or
extraction (Horwitz, 1979; Greger and Baler, 1981). These
analyses were more sensitive than standard atomic absorp-
tion spectrometry. However, ATSDR (2003) reported that
the methods most commonly used for analyses of tin in bio-
logical and environmental materials in 2003 involved induc-
tively coupled plasma atomic emission analysis and flame or
furnace atomic absorption. The samples are generally di-
gested in acid and sometimes extracted with a resin.
Both gas chromatography and high performance liquid
chromatography are used to separate and identify organotin
compounds (ATSDR, 2003). However, the methods for de-
termination of specific tin compounds are less well devel-
oped than for total tin. No ongoing studies involving analyti-
cal techniques of tin or tin compounds were identified in a
search of Federal Research in Progress in 2003 (ATSDR,
2003).
REGULATION AND METABOLISM
Absorption and iVietaboiism
Generally rats (Hiles, 1974; Fritsch et al., 1977; Greger
and Johnson, 1981; Johnson and Greger, 1985) and humans
(Calloway and McMuUen, 1966; Tipton et al., 1969;
386
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rev
387
Johnson and Greger, 1982) fed 100 mg/kg diet of tin as
stannous chloride excreted more than 90 percent of the tin in
the feces. However, human subjects fed very low levels (0.11
mg/day of tin) of inorganic tin often lost only 50 percent of
their tin intake in feces (Johnson and Greger, 1982). Sullivan
et al. (1984) found that neonatal rats absorbed tin more than
adult rats when both were gavaged with solutions containing
"■'Sn (0.9 percent versus 0.01 percent of dose, respectively).
Some of the tin, especially tin 2+ lost in the feces, may be
of endogenous origin. Hiles (1974) noted that 12. 1 percent of
a single intravenous dose of "''Sn 2+ appeared in the feces but
only 3.1 percent of a single intravenous (IV) dose of "''Sn 4+
appeared in the feces. Moreover, when "^Sn 2+ was injected
into rats with their bile ducts cannulated, 11.5 percent of the
dose was collected in the bile; virtually none of the ^^^Sn from
an rV dose of "^Sn 4+ was collected in the bile.
Little tin is excreted in the urine of rats (Hiles, 1974;
Fritsch et al., 1977) or humans (Tipton et al., 1969; Johnson
and Greger, 1982; Perry and Perry, 1959). Urinary losses of
tin reflect large differences in tin intake. Eight human sub-
jects excreted four times more tin (122 versus 29 |Jg/day of
tin) when fed 50 mg as stannous chloride rather than 0.11
mg tin daily (Johnson and Greger, 1982).
Absorption of some organotin compounds (e.g.,
triethyltin and trimethyltin) is high (Kimbrough, 1976). For
example, the lethal dose of triethyltin is the same whether
administered intraperitoneally (IP) or orally. The lethal oral
dose of trimethyltin tin is about twice the lethal ip dose
(Kimbrough, 1976). The absorption of dimethyltin is also
much more rapid than of inorganic tin (Noland et al., 1983).
Little has been reported on the excretion of organotin com-
pounds, which may have two phases. Initially after injec-
tion, "■'Sn as bis-tributyltin oxide is rapidly lost from the
bodies of mice. After ten days, the tin from the tributyltin is
lost at a rate parallel to that of inorganic tin (Brown et al.,
1977).
SOURCES AND BIOAVAILABILITY
Most fresh foods naturally contain less than 1 mg/kg of
tin (Schroeder et al., 1964; Greger, 1988). Thus the amount
of tin in the diets of livestock is small but humans and pets
may be exposed to dietary tin from other sources.
Food additives are a minor source of dietary tin for hu-
mans (NRC, 1979; Greger, 1988). Stannous chloride is a
GRAS-approved coloring agent, preservative, and
sequestrant. A variety of organotin compounds have been
used as ascaricides and fungicides (Schafer and Femfert,
1984). Dibutyltin compounds have been used as
anthelmintics for poultry (Barnes and Stoner, 1959). Alkyl
tin compounds have been widely used as stabilizers and cata-
lysts in plastics that come in contact with food (Sherlock and
Smart, 1984) but the migration of tin from these compounds
into foods is thought to be small (Kumpulainen and
Koivistoinen, 1977).
The major source of dietary tin for humans (and probably
for some pets) is canned foods (Schroeder et al., 1964;
Greger and Baier, 1981; Sherlock and Smart, 1984; Blunden
and Wallace, 2003). Foods packed in cans that were totally
coated with lacquer generally contain <4 mg/kg food of tin
(Greger and Baier, 1981). Light-colored foods (e.g., pine-
apple, grapefruit and orange juices, applesauce, tomato
paste), which are often packed in unlacquered cans to pre-
vent discoloration (Sistrunk and Gascoigne, 1983), contained
40-150 mg/kg food of tin when the cans were first opened
(Greger and Baier, 1981; Sherlock and Smart, 1984). How-
ever, the amount of tin in canned foods is affected by storage
conditions. Canned foods accumulated more tin when stored
for several months, especially if ambient temperatures were
high (Calloway and McMullen, 1966; Nagy et al., 1980) or
if the foods had high nitrate levels or had a low pH (Davis et
al., 1980; Sherlock and Smart, 1984). The biggest accumula-
tion of tin in food occurred when food was stored in opened,
unlacquered cans. Several acidic foods (grapefruit sections,
crushed pineapple, and tomato sauce) stored in opened,
unlacquered cans in the refrigerator for 1 week accumulated
more than 250 mg/kg food of tin (Greger and Baier, 1981).
Public water supplies in the United States were reported
to contain 1.1 to 2.2 |Jg/L of tin in 1977, and seawater was
reported to contain 0.2 to 0.3 |Jg/L of tin (NRC, 1977). Waste
from industrial uses of inorganic tin compounds (in dyeing
fabrics, weighting silks, tinning vessels, and producing lac-
quers, nail polishes, and varnishes) and agricultural uses of
organotin compounds as pesticides contributed tin to public
water supplies. Similarly, stannous fluoride is used in many
dentifrices and consequently reaches municipal sewers
(NRC, 1977). Little of this tin is believed to remain in the
water supply because many tin salts are insoluble in water
(NRC, 1977). However, Hallas et al. (1982) noted that mixed
inoculums of microorganisms from Chesapeake Bay sedi-
ments transformed inorganic tin to organotin compounds,
such as dimethyltin and trimethyltin.
Bioavailability
Rats absorbed a single dose of 20 mg of tin 2+ more effi-
ciently than of tin 4+ (2.85 versus 0.65 percent) but the anion
components (fluoride, ascorbate, or pyrophosphate) of di-
etary tin did not affect absorption (Hiles, 1974). Fritsch et al.
(1977) observed that changes (in terms of sucrose, ascorbic
acid, potassium nitrate, albumen, oil, or ethanol) in diet did
not affect the absorption of "■'Sn, but Kojima et al. (1978)
noted that organic acids increased the absorption of dietary
tin. Johnson and Greger (1985) observed that a 3-fold in-
crease in dietary zinc levels (e.g., from ~15 to ~52 mg/kg
diet zinc as zinc sulfate) increased fecal losses of tin when
rats were fed 100-200 mg/kg diet of tin.
The various organotin compounds differ in
bioavailability. Mammals appear to absorb trimethyltin and
triethyltin much more than other organotin compounds
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MINERAL TOLERANCE OF ANIMALS
(Kimbrough, 1976; Mushak et al., 1982). The bioavailability
of organotin compounds in aqueous solutions is greatest at
neutral and slightly alkaline pH and is reduced in the pres-
ence of dissolved organic carbon (Rudel, 2003).
TOXICOSIS
Inorganic Tin
There are a few key signs of toxicosis in animals and
humans, injected, fed once, or chronically fed inorganic tin.
Common mechanisms underlie these signs and symptoms.
Hence the toxicosis of inorganic tin is organized by types of
symptoms or signs (Table 29-1).
Gastrointestinal Symptoms
There are only a few reports on the toxic effects in hu-
mans of single large doses of inorganic tin (Warburton et
al., 1962;Benoyetal., 1971; Barker and Runte, 1972). The
symptoms included nausea, abdominal cramping, diarrhea,
and vomiting and generally developed after individuals
consumed canned juices or acidic beverages prepared in
tinned vessels. These beverages contained 500 to 2,000
mg/L of tin.
Other animals may be less sensitive to inorganic tin than
humans. Benoy et al. (1971) found that 20 to 30 percent of
cats but none of the dogs dosed with juices containing 1 ,370
mg/L of tin vomited. No signs of toxicosis were observed in
cats or rats dosed with citric acid solutions containing up to
1 ,200 mg/L of tin, or in dogs and cats fed foods that con-
tained 400-470 mg/kg food of tin. Mushak et al. (1982) ob-
served no toxic effects in rat neonates orally dosed with 500
mg/kg BW of tin.
Chronic feeding of inorganic tin also affects the gut. Rats
fed a diet containing 0.8 percent tin chloride (about 300 mg/
kg B W/day of tin) for 1 3 weeks experienced pancreatic atro-
phy (Dreef van der Meulen et al., 1974). The gastrointestinal
tracts of rats fed high levels of tin (= 2,000 mg/kg diet of tin)
for 28 days hypertrophied (Johnson and Greger, 1984). In-
creased cell turnover in the small intestines was noted in rats
fed 900 mg/kg of tin (Janssen et al., 1985).
Growth and Zinc Utilization
The effects of inorganic tin on growth are dependent on
the dose and form of the tin fed. Growth of rats was usually
depressed when dietary tin levels were elevated above 500
mg/kg diet of tin (deGroot, 1973; de Groot et al., 1973;
Dreef van der Meulen et al., 1974; Johnson and Greger,
1984). The ingestion of soluble tin compounds (e.g., stan-
nous chloride, stannous sulfate, and stannous oxalate) af-
fected growth more than insoluble tin compounds (e.g., stan-
nous oxide, stannous oleate, and stannous sulfide) (de Groot
et al., 1973). However, the addition of 5 mg/L of tin as stan-
nous chloride to the water provided to mice for 540 days did
not affect their growth (Schroeder and Balassa, 1967).
Feed intakes of rats were sometimes depressed when ani-
mals were fed >500 mg/kg diet of tin (Johnson and Greger,
1984; Rader, 1991). Pekelharing et al. (1994) reported a hn-
ear inverse response of feed intake to dietary tin levels from
10-200 mg/kg diet of tin.
It is well established that zinc deficiency will depress food
intake and growth of animals (Mertz, 1986). The effect of tin
on growth was partially due to the interaction between tin
and zinc. Rats fed 500 mg/kg diet of tin and =>15mg/kg diet
of zinc as zinc sulfate for 23 days have suppressed levels of
zinc in bones and soft tissues (Greger and Johnson, 1981;
Johnson and Greger, 1984). Among rats fed 100-200 mg/kg
diet of tin, tibia zinc levels were depressed after 21 days
(Johnson and Greger, 1984) and tibia, kidney, and plasma
zinc concentrations were depressed after 28 days (Rader,
1991; Pekelharing et al., 1994).
At least part of this effect was due to the effect of dietary
tin on apparent absorption of zinc. Johnson et al. (1982)
found that human subjects lost an additional 2 mg zinc daily
in feces when fed 50 mg tin versus 0.1 mg tin daily; this
resulted in significantly poorer overall retention of zinc by
these subjects. Valberg et al. (1984) confirmed these results
and found that a dose of 36 mg inorganic tin depressed the
absorption by humans of ^^Zn from 4 mg of zinc as zinc
chloride or from a turkey test meal. The mechanism by which
tin affects zinc absorption appears to be dose dependent.
Johnson and Greger (1984) found that when rats were fed
high levels (~ 2,000 mg/kg diet of tin and =15 mg/kg diet of
zinc as zinc sulfate), their gastrointestinal tracts were hyper-
trophied and endogenous losses of zinc in the feces were
significantly increased. Janssen et al. (1985) observed in-
creased cell turnover in the small intestines of rats fed 900
mg/kg diet of tin. However, Johnson and Greger (1984) ob-
served that when moderate levels of tin (200-500 mg/kg diet
of tin and ''15 mg/kg diet of zinc as zinc sulfate) were fed,
endogenous losses of zinc in feces were constant but the true
absorption of zinc tended to be depressed.
Hematological Status and Iron, Copper,
and Selenium Utilization
The ingestion of high levels of tin ( 3,000 mg/kg diet of
tin) as stannous chloride induced anemia in rats (deGroot,
1973; deGroot et al., 1973). Others observed reduced hema-
tocrits among rats fed 500 mg/kg diet of tin as compared to
pair-fed controls (Janssen et al., 1985) and rats fed about 300
mg/kg B W/day of tin (Dreef van der Meulen et al., 1974).
Moderate intakes of tin (100 mg/kg diet of tin) induced ane-
mia in rats only if the rats were also fed low levels of copper
(Riecks and Rader, 1990; Rader, 1990; Rader et al. 1991).
The effects of dietary tin on other measures of iron status
were not consistent among studies despite similar protocols
(i.e., stannous chloride was used as the source of dietary tin
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389
in purified diets; the feeding periods lasted 21-28 days; and
growing rats were used). The ingestion of moderate levels of
tin ( 200 mg/kg diet of tin) depressed plasma iron concen-
trations in rats fed 35 mg/kg diet of iron (Beynen et al., 1992)
but not serum iron concentrations in rats fed 35 or 250 mg/kg
diet of iron (deGroot, 1973); depressed transferrin satura-
tion, but did not increase total iron binding capacity of serum
(Beynen et al., 1992); depressed plasma and spleen iron con-
centrations (Beynen et al., 1992), but not liver, kidney, or
tibia concentrations of iron in rats fed ~37 mg/kg diet of iron
(Greger and Johnson, 1981; Johnson and Greger, 1985).
It is doubtful that the anemia induced by ingestion of tin
was caused primarily by tin suppressing iron absorption. The
injection of tin (>1 mg/kg BW of Sn+^) into in situ rat intes-
tinal segments reduced the absorption of ^^Fe (<0.3 mg/kg
BW of iron) (Schafer and Forth, 1983). However, others
could not demonstrate that tin affected iron absorption of
rats fed =>36 mg/kg diet of iron and 100 mg/kg of tin (Rader
etal., 1991) or humans fed daily ~19 mg of iron and -50 mg
of tin (Johnson, etal., 1982). In contrast, the effect of dietary
tin on tissue concentrations of copper and copper-containing
proteins appeared to be dose dependent. The plasma copper
levels of rats fed high levels of tin ( 500 mg/kg diet of tin)
were depressed to less than 20 percent of the levels found in
control animals. Kidney and liver levels of copper were also
severely depressed in these animals (Greger and Johnson,
1981; Johnson and Greger, 1985). Ingestion of 200 mg/kg
diet of tin usually depressed copper concentrations in soft
tissues among rats fed adequate levels of essential elements
(=5 mg/kg diet of copper, ~37 mg/kg diet of iron, and =16
mg/kg of zinc) (Greger and Johnson, 1981; Johnson and
Greger, 1985). Ingestion of only 100 mg/kg diet of tin re-
duced serum ceruloplasmin levels and sometimes liver cop-
per concentrations in rats fed adequate levels of copper (=5
mg/kg diet of copper, ='36 mg/kg diet of iron, and =32 mg/kg
diet of zinc) but consistently reduced liver copper concentra-
tions among rats fed marginally adequate levels of copper
(0.5 mg/kg diet of copper) (Riecks and Rader, 1990; Rader,
1991; Rader etal., 1991). Ingestion of 100 mg/kg diet of tin
was also associated with depression of serum superoxide
dismutase (a copper-containing enzyme) activity especially
among rats fed marginally adequate levels of copper (Riecks
and Rader, 1990; Rader, 1991; Rader et al., 1991). Anemia
is a common symptom of copper deficiency. Moreover,
deGroot (1973) demonstrated that the addition of copper to
diets of rats eliminated the anemia induced by feeding 150
mg/kg diet of tin.
Johnson et al. (1982) found that the addition of 50 mg tin
daily (equivalent to 100 mg/kg dry diet of tin) to the diets of
humans for 20 days had no effect on the apparent absorption
of copper or on plasma copper or ceruloplasmin concentra-
tions. This may reflect adequate copper intake by the sub-
ject. Yu and Beynen (1995) reported that oral tin depressed
true absorption of copper but that decreases in biliary excre-
tion of copper compensated so that apparent absorption ap-
peared unchanged. Accordingly, animals with marginal cop-
per status might not be able to compensate when tin de-
presses the true absorption of copper.
In theory, tin may also induce anemia by affecting heme
synthesizing and catabolizing enzymes. Injection of tin into
mice (Chiba et al., 1985) and rabbits (Zareba et al., 1986)
depressed erythrocyte 5-amino levulinic acid dehydratase (5-
ALAD is a heme synthesis enzyme) activity. Injections of
tin induced hemeoxygenase (an enzyme involved in heme
catabolism) activity in the kidneys and livers of rats (Kappas
and Maines, 1976; Dwivedi et al, 1985). However, only the
ingestion of very high doses of tin (2,000 not 200 mg/kg
diet of tin) depressed the activity of blood 5-ALAD in rats
(Johnson and Greger, 1985).
The effect of injected tin (as stannous chloride) on 5-
ALAD could be counteracted by also injecting zinc into rab-
bits (Zareba et al., 1986) or sodium selenite into mice (Chiba
et al., 1985). Interestingly, dietary interactions have been
demonstrated not only for tin and zinc (as already discussed)
but also for tin and selenium. Hill and Matrone (1970)
showed that high dietary level of tin depressed the apparent
absorption of selenium from chick intestinal segments.
Greger et al. (1982) demonstrated that human subjects fed
50 versus 0.11 mg/day of tin apparently absorbed signifi-
cantly less selenium.
Bone and Calcium Utilization
Yamaguchi et al. (1982b) observed that the hydro xypro-
line content of the femoral epiphyses was decreased in rats
given tin orally (1 mg/kg BW of tin twice a day for 28 days).
Ogoshi et al. (1981) observed that the compressive strength
of femurs of young rats given tin (300 mg/L of tin) in their
drinking water was significantly decreased. Japanese re-
searchers have observed that oral exposure (3 mg/kg BW of
tin twice daily for 90 days) to tin depressed the activity of
acid, and sometimes alkaline, phosphatases in serum, duode-
num, and bone (Yamaguchi et al., 1980, 1981).
It is doubtful that these effects of tin on bone were prima-
rily modulated through effects on calcium metabolism. The
Japanese workers have found that oral exposure to levels of
tin as low as 50 mg/kg diet of tin depressed calcium concen-
trations in bone and serum but elevated calcium levels in
kidneys of growing rats (Yamamoto et al., 1976; Yamaguchi
etal., 1980, 1981). Johnson and Greger (1985) also observed
that moderate levels of inorganic tin (100 mg/kg diet of tin)
depressed the calcium content (but not concentration) of
tibias but observed no changes in plasma calcium level of
weanling rats fed recommended levels (=5,000 mg/ kg diet
of calcium). Oral exposure to tin (30 mg/kg BW by gavage)
was found to increase biliary volume and calcium content in
rats (Yamaguchi and Yamamoto, 1978) but had no effect on
fecal or urinary calcium losses in rats fed 1 1,000 mg/kg diet
of calcium (Yamaguchi et al., 1982a) or humans fed =800 mg
calcium daily (Johnson and Greger, 1982).
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MINERAL TOLERANCE OF ANIMALS
Organic Tin Compounds
In general, organotin compounds are more toxic than in-
organic tin (ATSDR, 2003). However, tlie toxicity of vari-
ous organotin compounds varies greatly.
Relative Effects of Oral Doses of Various Organotin
Compounds in Mammals
The LDjQ of triphenyltin acetate, triphenyltin hydroxide,
and tricyclohexyltin hydroxide given orally to rats was 360-
540 mg/kg BW of tin whereas the LDjq of these compounds
when injected (IP) into rats was 11.9-13 mg/kg BW of tin
(Kimbrough, 1976). In contrast, the LDjq's of trimethyltin
and triethyltin administered orally was 10-30 mg/kg of tin
and administered IP was 7-16 mg/kg of tin (Dyer et al.,
1982b).
Mushak et al. (1982) observed that trimethyltin, triethyltin,
and tri-n-butyltin were more toxic than other triorganotin and
diorganotin compounds. Oral doses of trimethyltin (0.66
mg/kg BW of tin), triethyltin (1.3 mg/kg BW of tin), tri-n-
propyltin (4.2 mg/kg BW of tin), and tri-n-butyltin (1.0 mg/kg
BW of tin) killed at least some of the neonatal rats dosed.
Similar oral doses of tin as tricyclohexyltin, triphenyltin,
diethyltin, and dimethyltin produced no fatalities and did not
affect weight gain of the pups.
The effect of organotin compounds in these studies on
feed intake was important. For example, rat pups orally
dosed with tri-n-butyltin ( 1 mg/kg BW) appeared to die of
starvation (Mushak et al., 1982). Rats injected with
triethyltin (1.5 mg/kg BW of tin) reduced feed intake
abruptly (DeHaven et al., 1982). MacPhail (1982) demon-
strated that trimethyltin and triethyltin induced flavor aver-
sions in rats.
Some of the differences in toxicity of various organotin
compounds reflected the greater gut absorption of
trimethyltin and triethyltin than other organotin compounds
(Kimbrough, 1976). The speed of elimination of organotin
compounds and hence the retained tissue levels of tin may
also be important. For example, higher concentrations of tin
were found in the tissues of rats during the first 24 hours
after injections of 6 mg/kg of triethyltin than after similar
doses of trimethyltin, but the rate of loss of triethyltin from
the tissues was also more rapid (Cook et al., 1984). How-
ever, tissue levels of tin did not predict the ultimate toxicity
of organotin compounds. Mushak et al. (1982) demonstrated
that although pups orally dosed with a variety of organotin
compounds (1-30 mg/kg BW) accumulated tin in their
brains, kidneys, and livers, only rat pups dosed with
trimethyltin and triethyltin showed any neurotoxic effects.
Rats appear to be less sensitive to organotin compounds
than rabbits, guinea pigs, sheep (Kimbrough, 1976), and
mice (Wenger et al., 1982). Dyer et al. (1982b) found larger
rats to be more sensitive than smaller rats.
The comparative toxicity of various organotin com-
pounds to fish was generally similar to the comparative
toxicity of the organotin compounds to mammals, de Vries
et al. (1991) exposed rainbow trout during the early life
stages (1 10 days) to organotin compounds. The diorganotin
compounds (dibutyltin and diphenyltin) were three orders
of magnitude less toxic than triorganotin compounds
(tributyltin, triphenyltin, and tricyclohexyltin).
Tricyclohexyltin was most toxic; no fish survived expo-
sure to 3 nm for I week. The NOEL for dibutyltin and
diphenyltin was 160 nM (40 and 60 |Jg/kg water) and for
tributyltin and triphenyltin was 0.12 nM (40 and 50 ng/kg
water).
Not only is tributyltin more toxic to fish than dibutyltin, it
also has accumulated more in fish tissues. Farmed fish in the
area of Naples, Italy, were more apt (85 percent of fish
sampled) to accumulate tributyltin (2-260 |Jg/kg) than
dibutyltin (10 percent offish sampled and levels of 1-26 |Jg/kg)
(Amodio-Cocchieri et al., 2000).
Trimethyltin Toxicosis
Rats injected with trimethyltin developed spontaneous
seizures, tail mutilation, vocalization, and hyperactivity; cell
loss was largely confined to the inferior pyramidal cells
(Dyer et al., 1982b). Similarly, rats dosed orally once with
trimethyltin (7 mg/kg of tin) developed hyperactivity and
lost pyramidal cells (Rupert et al., 1982; Dyer et al., 1982a).
Like in the rat, hyperactivity was a symptom of toxicity in
mice but extensive necrosis was observed in the granule
cells, not the pyramidal neurons, of the hippocampus (Chang
et al., 1982).
Triethyltin Toxicosis
Orally administering triethyltin compounds for 14-27
days produced an edema in the myelin of the central nervous
system and depressed food and water intake of rats
(Kimbrough, 1976; Squibb et al., 1980; Mushak et al., 1982).
Rats fed 20 mg/kg diet of tin as triethyltin for about 2 weeks
developed paralysis in their hind limbs; symptoms regressed
when exposure ceased (Magee et al., 1957). Rat pups dosed
orally with 1, but not 0.3, mg/kg of tin as triethyltin exhib-
ited tremors and microscopic changes in myelin (Mushak et
al., 1982). Feeding rats a diet low (<0.4 percent of total en-
ergy) in a-linolenic acid made them more sensitive to IP in-
jections of triethyltin (Bourre et al., 1989).
The effects of triethyltin toxicity have been observed in
humans (Barnes and Stoner, 1959; ATSDR, 2003). In 1954
in France, Stalinon (a pharmaceutical containing diethyltin
diodine and linoleic acid) was sold for treatment of Staphy-
lococcal skin infections, osteomyelitis, anthrax, and acne.
About 100 people using the product died. Other symptoms
included headache, vomiting, abdominal pain, visual distur-
bances, rapid weight loss, and paralysis. Recovery after dis-
continuing use of the product was slow and often incom-
plete. The product was contaminated with triethyltin and the
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391
toxic dose was estimated to be 70 mg of triethyltin in 8 days.
However, other organotin compounds were found in the
product.
Tri-n-butyltin and Dibutyltin Toxicosis
Single large oral doses of tributyltin (500 mg/kg BW),
but not ingestion of a diet with 2.5 mg/kg/day of tributyltin
oxide for 106 weeks, produced hemorrhages in the digestive
tracts of mice (ATSDR, 2003). Rats dosed with 1 mg/kg
BW/day of tin as tributyltin acetate for 24 days developed
fibrosis in the portal triad region of the liver with inflamma-
tion of the bile ducts (Mushak et al., 1982).
Several groups of investigators observed that single oral
doses of dibutyltin to rats (50 mg/kg) and hamsters (30 mg/kg)
and chronic ingestion of dibutyltin chloride (23, but not 7.7,
mg/kg BW/day) by rats for 2 weeks inflamed the wall of the
bile duct (ATSDR, 2003). If the inflammation of the bile
duct caused perforation of the duct, fibrosis in the pancreas
and liver occurred among animals in which the pancreatic
and bile ducts are combined (e.g., rats, mice, hamsters) but
not in animals with separate ducts (i.e., rabbits and guinea
pigs) (Kimbrough, 1976; ATSDR, 2003).
Additional Side Effects of Diorganotin Compounds
Teratological effects, especially of the skeleton, have
been observed when pregnant rats are fed di-n-butyltin ac-
etate (>10 mg/kg/day), but not n-butyltin trichloride (even at
doses of 400 mg/kg/day), for 10 days during gestation (Noda
et al., 1992).
Gastric intubation of rats and chicks for 10-14 days with
the dichloride salts of dimethyltin, dibutyltin, and dioctyltin
resulted in depression of the thymus weights of young rats
and depression of the weight of the bursa Fabricii in chick-
ens (Renhof etal., 1980). Trout exposed to >800 M dibutyltin
and >0.6 nM tributyltin for 133 days did not exhibit atrophy
of the thymus but were less resistant to an intraperitoneal
challenge with a secondary pathogenic bacterium (deVries
etal., 1991).
TISSUE LEVELS
The Agency for Toxic Substances and Disease Registry
(2003) reported that no studies were found concerning the
distribution of tin in tissues of humans after oral administra-
tion of inorganic or organic tin. The overall apparent reten-
tion of tin by human subjects in balance studies (whether the
tin was naturally present, a contaminant from cans, or as
stannous chloride) was low (i.e., not significantly different
than equilibrium) (Callaway and McMullen, 1966; Tipton et
al., 1969; Johnson and Greger, 1982b).
However, tin has been found in at least trace amounts in
most mammalian tissue (Schroeder et al., 1964; Schafer and
Femfert, 1984). Generally, all soft tissues contained <1 mg/kg
of tin but bone contained 0.5-8.0 mg/kg of tin (ATSDR, 2003).
(All tissue tin concentrations are reported in this report on a wet
weight basis unless noted otherwise.)
Rats fed diets (21-28 days) supplemented with inorganic
tin (100-2,000 mg/kg diet of tin as stannous chloride) (Johnson
and Greger, 1985) or orally dosed (twice a day for 90 days)
with a solution of inorganic tin (0.3-3.0 mg/kg BW/day of tin
as stannous chloride) (Yamaguchi et al., 1980) accumulated
tin in their tibias, kidneys, and livers generally in proportion to
their exposure to tin. The average tin concentrations in kid-
neys and livers of control rats in these studies ranged from
0. 14-0.52 mg/kg wet tissue of tin and of rats orally dosed with
tin ranged from 0.24-8.5 mg/kg wet tissue of tin; the average
tin concentrations in bone of control rats ranged from 0.3-2. 1
mg/kg wet bone of tin and of rats orally dosed with tin ranged
from 4.3^5.7 mg/kg wet bone of tin (Table 29-2).
Ingested organic tin compounds (i.e., trimethyltin,
triethyltin, tributyltin, and tripropryltin) accumulated more
in the liver than in other soft tissues and even the levels in
the liver were less than 0.6 |Jg/g wet tissue among neonatal
rats that developed clinical signs (Mushak et al., 1982).
No data are available on the accumulation of tin in tissues
of livestock fed controlled levels of tin. However, farmed
fish in the area of Naples, Italy, were more apt (85 percent of
fish sampled) to accumulate tributyltin (2-260 |Jg/kg) than
dibutyltin (10 percent offish sampled and levels of 1-26 |Jg/kg)
(Amodio-Cocchieri et al., 2000).
MAXIMUM TOLERABLE LEVELS
Acute responses to inorganic tin have been observed when
humans consumed a single dose of beverages containing 0.5-
2.0 mg/Loftin(Warburton etal., 1962; Benoy et al., 1971;
Barker and Runte, 1972). Chronic symptoms (i.e., decreased
zinc absorption) were observed in humans fed 50 mg/day of
tin for 20 days (Johnson et al., 1982). These subjects prob-
ably consumed about 0.5 kg dry weight of diet per day or
about 100 mg/kg dry diet of tin.
The Agency for Toxic Substances and Disease Registry
(2003) suggested a NOAEL of 32 mg/kg/day of tin for
chronic oral exposure to inorganic tin based on limited
work with rats. If the rats weighed 200 g and consumed 15 g
diet per day, the toxic signs occurred when about 400 mg/kg
diet of tin was consumed. These calculations did not
consider data cited in this document. Several studies cited
observed adverse effects (lowered status and impaired ab-
sorption of zinc and copper and anemia) in rats fed 100-
200 mg/kg diet of tin (deGroot, 1973; Greger and Johnson,
1981; Johnson and Greger, 1984; Riecks and Radar, 1990;
Radar etal., 1991; Pekelharing etal., 1994; Yu and Beynen,
1995).
Since the estimates in rats and humans are similar and no
data are available for livestock, it is suggested that livestock
should not be fed chronically more than 100 mg inorganic
tin/kg diet.
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MINERAL TOLERANCE OF ANIMALS
Based on limited data primarily in rats, the Agency for
Toxic Substances and Disease Registry (2003) suggested the
following LOAELs for oral exposure to various organotin
compounds for humans: dibutyltin, 3.8 mg/kg/day;
tributyltin, 1 mg/kg/day; triethyltin, 0.66 mg/kg/day; and
trimethyltin, 1 mg/kg/day. If a 200-g rat consumed 15 kg
diet per day, chronic toxic effects would be expected to oc-
cur when diets contained more than 50 mg/kg diet of
dibutyltin, more than 13 mg/kg diet of tributyltin or
trimethyltin, or 9 mg/kg diet of triethyltin. These guidelines
also appear logical for livestock.
FUTURE RESEARCH NEEDS
Future research on inorganic tin should focus on the in-
teractions of inorganic tin with essential minerals because
that data will yield the most sensitive indications of adverse
effects of ingested inorganic tin. Almost no research could
be found on the toxicity of tin compounds to livestock. A
few studies with a variety of species would make application
of data collected with rats to livestock possible.
Chronic studies on the metabolism (excretion and break-
down of compounds in the gut and liver) of organotin com-
pounds are needed. Without these studies, interpretations of
studies in which rats were injected with organotin com-
pounds are often questionable. More information is also
needed on interconversions of inorganic tin and organotin
compounds by microorganisms in landfill leaches and lake
and estuary sediments. The latter information is particularly
important to those concerned with the toxicity of organotin
compounds to fish.
SUMMARY
Tin is not considered to be an essential element. Exposure
of livestock to high levels of inorganic tin is unlikely. If it
occurred, the animals, which were in marginal nutritional
status in regard to zinc or copper, would be most sensitive to
chronic high doses of inorganic tin.
Organotin compounds are many times more toxic than
inorganic tin. The symptoms of organotin compound toxico-
sis are also different than those of inorganic tin.
REFERENCES
Amodio-Coccliieri, R., T. Cirillo, M. Amorena, M. Caralieve, A. Lucisano,
and U. Del Prete. 2000. Alkyltins in farmed fisli and shellfish. Intl. J.
FoodSci.Nutr. 51:147-151.
ATSDR (Agency for Toxic Substances and Disease Registry). 2003. Toxi-
cological profile for tin. U.S. Department of Health and Human Ser-
vices, Public Health Service. Atlanta, GA. Available at http://
www.atsdr.cdc.gov/toxprofiles/tp55.html. Accessed December 29,
2003.
Earlier, W. H., Jr., and V. Runte. 1972. Tomato juice-associated gastroen-
teritis. Am. J. Epidem. 96: 219-226.
Barnes, J. M., and H. B. Stoner. 1959. The toxicology of tin compounds.
Pharmacof Rev. 11:211-231.
Benoy, C. J., P. A. Hooper, and R. Schneider. 1971. The toxicity of tin in
canned fruit juices and solid foods. Food Cosmet. Toxicol. 9:645-656.
Beynen, A. C, H. L. Pekelharing, and A. G. Lemmens. 1992. High intakes
of tin lower iron status in rats. Biol. Trace Elem. Res. 35:85-88.
Blunden, S., and T. Wallace. 2003. Tin in canned food: a review and under-
standing of occurrence and effect. Food Cosmet. Toxicol. 41:1651-
1662.
Bourre, J. M., M. Francois, A. Youyou, O. Dumont, M. Piciotti, D. Pascal,
andG. Durand. 1989. The effects of dietary a-linolenic acid on the com-
position of nerve membranes, enzymatic activity, amplitude of electro-
physiological parameters, resistance to poisons, and performance of
learning tasks in rats. J. Nutr. 1 19:1880-1892.
Brown, R. A., C. M. Nazario, R. S. deTirado, J. Castrillon, and E. T. Agard.
1977. A comparison of half-life of inorganic and organic tin in the
mouse. Environ. Res. 13:56-61.
Calloway, D. H., and J. J. McMullen. 1966. Fecal excretion of iron and tin
by men fed stored canned foods. Am. J. Clin. Nutr. 18:1—5.
Carlin J. F., Jr. 2002. Tin. U.S. Geological Survey. Available at http://
mineral.usgs.gov/minerals/ pubs/commodity /tin/index.html. Accessed
December 29, 2003.
Chang, L. W., T. M. Tiemeyer, G. R. Wenger, and D. E. McMillan. 1982.
Neuropathology of mouse hippocampus in acute trimethyltin intoxica-
tion. Neurobehav. Toxicol. Teratol. 4:149-156.
Chiba, M., N. Fujimoto, and M. Kikuchi. 1985. Protective effect of sele-
nium on the inhibition of erythrocyte 5-aminolevulinate dehydratase
activity by tin. Toxicol. Lett. 24:235-241.
Cook, L. L., K. E. Stine, and L. W. Reiter. 1984. Tin distribution in adult rat
tissues after exposure to trimethyltin and triethyltin. Toxicol. Appl.
Pharmacol. 76:344-348.
Davis. D. R., C. W. Cockrell, and K. J. Wiese. 1980. Can pitting in green
beans. Relation to vacuum, pH, nitrate, phosphate, copper and iron con-
tent. J. Food Sci. 45:141 1-1415.
DeGroot, A. P. 1973. Subacute toxicity of inorganic tin as influenced by
dietary levels of iron and copper. Food Cosmet. Toxicol. 1 1 :955-962.
DeGroot, A. P., V. J. Feron, and H. P. Til. 1973. Short-term toxicity studies
on some salts and oxides oftin in rats. Food Cosmet. Toxicol. 11:19—30.
DeHaven, D. L., M. J. Wayner, F. C. Barone, and S. M. Evans. 1982. Ef-
fects of triethyltin on ingestive behavior at ad lib. reduced, and recov-
ered body weight. Neurobehav. Toxicol. Teratol. 4:127-133.
deVries, H., A. H. Penninks, N. J. Snoeij, and W. Seinen. 1991. Compara-
tive toxicity of organotin compounds to rainbow trout (Oncorhynchus
mykiss) yolk sac fry. Sci. Total Environ. 103:229-243.
Dreef van der Meulen, H. C, V. J. Feron, and H. P. Til. 1974. Pancreatic
atrophy and other pathological changes in rats following feeding of st-
annous chloride. Pathol. Eur. 9:185-192.
Dwivedi, R. S., G. Kaur, R. C. Srirastava, and C. R. K. Murti. 1985. Role of
tin on heme and drug biotransformation mechanism of partially hepate-
ctomized rats. Indus. Health 23:1-7.
Dyer, R. S., T. L. Deshields, and W. F. Wonderlin. 1982a. Trimethyltin-
induced changes in gross morphology of the hippocampus. Neurobehav.
Toxicol. Teratol. 4:141-147.
Dyer, R. S., T. J. Walsh, W. F. Wonderlin, and M. Bercegeay. 1982b. The
trimethyltin syndrome in rats. Neurobehav. Toxicol. Teratol. 4:127—
133.
Ferretti, G. A.. J. M. Tanzer, and N. Tianoff. 1982. The effect of fluoride
and stannous ions on Streptococcus mutans. Caries Res. 16:298-307.
Fritsch, P., G. de Saint Blanquat, and R. Derache. 1977. Effect of vari-
ous dietary components on absorption and tissue distribution of
orally administered inorganic tin in rats. Food Cosmet. Toxicol.
15:147-149.
Greger, J. L. 1988. Tin and aluminum. Pp. 291-323 in Trace Minerals in
Food. K. T. Smith, ed. New York: Marcel Dekker.
Greger, J. L., and M. Baier. 1981. Tin and iron content of canned and
bottled food. J. Food Sci. 46:1751-1754.
Greger, J. L., and M. A. Johnson. 1981. Effect of dietary tin on zinc, cop-
per, and iron utilization by rats. Food Cosmet. Toxicol. 19:163-166.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
rev
393
Greger, J. L., S. A. Smith, M. A. Jolinson, and M. J. Baier. t982. Effects of
dietary tin and aluminum on selenium utilization by adult males. Biol.
Trace Elem. Res. 4:269-278.
Hallas, L. E., J. C. Means, and J. J. Cooney. 1982. Methylation of tin by
estuarine microorganisms. Science 215:1505-1507.
Hiles, R. A. 1974. Absorption, distribution and excretion of inorganic tin in
rats. Toxicol. Appl. Pharmacol. 27:366-379.
Hill, C. H., and G. Matrone. 1970. Chemical parameters in the study on in
vivo and in vitro interactions of transition elements. Fed. Proc. 29: 1474—
1481.
Horwitz, W. 1979. Review of tin analysis. J. Assoc. Off. Anal. Chem.
62:1251-1264.
Janssen, P. J., M. C. Bosland, J. P. van Heeds, B. J. Spit, M. I. Willems, and
C. F. Kuper. 1985. Effects of feeding stannous chloride on different parts of
the gastrointestinal tract of the rat. Toxicol. Appl. Pharmacol. 78:19-28
Johnson, M. A., and J. L. Greger. 1982. Effects of dietary tin on tin and
calcium metabolism of adult males. Am. J. Clin. Nutr. 35:655-660.
Johnson, M. A., andJ.L. Greger. 1984. Absorption, distribution and endog-
enous excretion of zinc by rats fed various dietary levels of inorganic tin
and zinc. J. Nutr. 114:1843-1852.
Johnson, M. A., and J. L. Greger. 1985. Tin, copper, iron and calcium me-
tabolism of rats fed various dietary levels of inorganic tin and zinc. J.
Nutr. 115:615-624.
Johnson, M. A., M. J. Baier, and J. L. Greger. 1982. Effects of dietary tin on
zinc, copper, iron, manganese and magnesium metabolism of adult
males. Am. J. Clin. Nutr. 35:1332-1338.
Kappas, A., andM. D. Maines. 1976. Tin: a potent inducer of heme oxyge-
nase in kidney. Science 192:60-62.
Kimbrough, R. D. 1976. Toxicity and health effects of selected organotin
compounds. A review. Environ. Health Perspect. 14:51-56.
Kojima, S., K. Saito, and M. Kiyozumi. 1978. Studies on poisonous metals.
IV. Absorption of stannic chloride from rat alimentary tract and effect
of various food components on its absorption. Yakugaku Zasshi
98:495-502.
Kumpulainen, J., and P. Koivistoinen. 1977. Advances in tin compound
analysis with special reference to organotin pesticide residues. Residue
Rev. 66:1-18.
Leverett, D. H., W. D. McHugh, and O. E. Jensen. 1984. Effect of daily
rinsing with stannous fluoride on plaque and gingivitis: final report. J.
Dent. Res. 63:1083-1086
MacPhail, R. C. 1982. Studies on the flavor aversions induced by trialkyltin
compounds. Neurobehav. Toxicol. Teratol. 4:225—230.
Magee, P. N., H. B. Stoner, and J. M. Barnes. 1957. The experimental pro-
duction of oedema in the central nervous system of the rat by triethyl
compounds. J. Pathol. Bacteriol. 73:107-124.
McDonald, J. L., and G. K. Stookey. 1973. Influence of whole grain prod-
ucts, phosphates and tin upon dental caries in the rat. J. Nutr. 103:1528—
1532.
Mertz, W. 1986. Tin. Pp. 441^146 in Trace Elements in Human and Animal
Nutrition, vol. 2, 5th ed. Orlando, EL: Academic Press.
Mushak, P., M. R. Krigman, and R. B. Mailman. 1982. Comparative
organotin toxicity in the developing rat: somatic and morphological
changes and relationship to accumulation of total tin. Neurobehav.
Toxicol. Teratol. 4:209-215.
Nagy, S., R. Rouseff, and S. V. Ting. 1980. Effects of temperature and
storage on the ion and tin contents of commercially canned single-
strength orange juice. J. Agric. Food Chem. 28: 1 166-1 169.
Noda T., T. Yamano, M. Shimizu, M. Saitoh, T. Nakamura, A. Yamada,
and S. Morita. 1992. Comparative teratogenicity of di-n-butyltin
diacetate with n-butyltin trichloride in rats. Arch. Environ. Contam.
Toxicol. 23:216-222.
Noland, E. A., P. T. McCauley, and R. J. Bull. 1983. Dimethyltin dichlo-
ride: investigations into its gastrointestinal absorption and transplacen-
tal transfer. J. Toxicol. Environ. Health 12:89-98.
NRC (National Research Council). 1977. Drinking Water and Health.
Washington, D.C.: National Academy Press.
NRC. 1979. Committee on the GRAS List Survey-Phase III: The 1977
Survey of Industry on the Use of Food Additives. Washington, D.C.:
National Academy Press.
Ogoshi, K., N. Kurumatani, Y. Aoki, T. Moriyama, and Y. Nanzai. 1981.
Decrease in compressive strength of the femoral bone in rats adminis-
tered stannous chloride for a short period. Toxicol. Appl. Pharmacol.
58:331-332.
Pekelharing, H. L., A. G. Lemmens, and A. C. Beynen 1994. Iron, copper,
and zinc status in rats fed on diets containing various concentrations of
tin. Br. J. Nutr. 71:103-109.
Perry, H. M., E. J. Perry. 1959. Normal concentrations of some trace metals
in human urine: changes produced by ethylenediaminetetra acetate. J.
Clin. Invest. 38:1452-1463.
Rader, J. I. 1991. Anti-nutritive effects of dietary tin. Adv. Exp. Med. Bio.
289:509-524.
Rader J. L., S. C. Hight, P. Whittaker, and S. G. Capar. 1991. Interactions
among dietary tin, copper, and carbohydrate in Long-Evans rats. J. Trace
Elem. Exp. Med. 4:135-147.
Renhof, M., U. Kretzer, T. Schurmeyer. H. Skupnik, and F. H. Kemper.
1980. Toxicity of organotin compounds in rats and chicks. Arch.
Toxicol. Suppl. 4:148-150.
Riecks, M., and J. I. Rader. 1990. Effects of dietary tin and copper on rat hepa-
tocellular antioxidant protection. Proc. Soc. Exp. Biol. Med. 95:12-128.
Rudel, H. 2003. Case study: bioavailability of tin and tin compounds.
Ecotoxicol. Environ. Safe. 56:180-189.
Rupert, P. H., T. J. Walsh, L. W. Reiter, andR. S. Dyer. 1982. Trimethyltin-
induced hyperactivity: time course and pattern. Neurobehavioral
Toxicol. Teratol. 4:135-139.
Schilfer, S.G.,U. Femfert. 1984. Tin — a toxic heavy metal? A review of the
literature. Regulat. Toxicol. Pharmacol. 4:57—69.
Schafer, S. G., and W. Forth. 1983. The influence of tin, nickel, and cadmium
on the intestinal absorption of iron. Ecotoxicol. Environ. Safe. 7:87—95.
Schroeder, H. A., and J. J. Balassa. 1967. Arsenic germanium, tin, and
vanadium in mice: effects on growth, survival and tissue levels. J. Nutr.
92:245-252.
Schroeder, H. A., J. J. Balassa, and I. H. Tipton. 1964. Abnormal trace
metals in man. Tin. J. Chronic Dis. 17:483-502.
Schwarz, K., D. B. Milne, and E. Vinyard. 1970. Growth effects of tin
compounds in rats maintained in trace element-controlled environment.
Biochem. Biophys. Res. Commun. 40:22-29.
Sherlock, J. C, and G. A. Smart. 1984. Tin in foods and the diet. Food
Addit. Contam. 1 :277-282.
Sistrunk, W. A., and H. L. Gascoigne. 1983. Stability of color in "concord"
grape juice and expression of color. J. Food Sci. 48:430^33, 440.
Squibb, R. E., N. G. Carmichale, and H. A. Tilson. 1980. Behavioral and
neuromoiphological effects of triethyl tin bromide in adult rats. Toxicol.
Appl. Pharmacol. 55:188-197.
Stookey, G. K., J. L. McDonald, S. B. Hughes, R. E. Smith, and R. D.
Strange. 1974. The influence of tin (II) and oat hulls upon dental caries
in the rat. Arch. Oral Biol. 19:107-1 12.
Sullivan, M. F., B. M. Miller, and J. C. Goebel. 1984. Gastrointestinal ab-
sorption of metals (^'CR, <'^Za, ^'^MTc, ifiiCd, '"Sn, "*^Pm, and -3**Po)
by rats and swine. Environ. Res. 35:439^53.
Tipton, I. H., P. L. Stewart, and J. Dickson. 1969. Patterns of elemental
excretion in long-term balance studies. Health Phys. 16:455^62.
Valberg, L. S., P. R. Flanagan, and M. J. Chamberlain. 1984. Effects of
iron, tin, and copper on zinc absorption in humans. Am. J. Clin. Nutr.
536-541.
Warburton, S., W. Udler, R. M. Ewert, and W. S. Haynes. 1962. Outbreak of
foodborne illness attributed to tin. U.S. Publ. Health Rep. 77:798-800.
Wenger, G. R., D. E. McMillan, and L. W. Chang. 1982. Behavioral toxi-
cology of acute trimethyltin exposure in the mouse. Neurobehavior.
Toxicol. Teratol. 4:157-161.
Yamaguchi, M., K. Sugii, and S. Okada. 1982b. Inhibition of collagen syn-
thesis in the femur of rats orally administered stannous chloride. J.
Pharmcobio-Dyn. 5:388-393.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
394
MINERAL TOLERANCE OF ANIMALS
Yamaguchi, M., R. Saito, and S. Okada. 1980. Dose-effect of inorganic tin
on biocliemical indices in rats. Toxicology 16:267-273.
Yamaguchi, M., K. Sugii, and S. Okada. 1981. Changes of mineral compo-
sition and its related enzyme activity in the femur of rats orally admin-
istered stannous chloride. J. Pharmcobio-Dyn. 4:874—878.
Yamaguchi, M., K. Sugii, and S. Okada. 1982a. Tin decreases femoral cal-
cium independently of calcium homeostasis in rats. Toxicol. Lett.
10:7-10.
Yamaguchi, M., and T. Yamamoto. 1978. Effect on tin on calcium content
in the bile of rats. Toxicol. Appl. Pharmacol. 45:611-616.
Yamamoto, T., M. Yamaguchi, and H. Sato. 1976. Accumulation of cal-
cium in kidney and decrease of calcium in serum of rats treated with tin
chloride. J. Toxicol. Environ. Health 1:749—756.
Yu, S., and A. C. Beynen. 1995. High tin intake reduces copper status in rats
through inhibition of copper absorption. Br. J. Nutr. 73:863-869.
Zareba, G., J. Chmielnicka, and G. Kustra. 1986. Interaction of tin and zinc
in some processes of heme biosynthesis in rabbits. Ecotoxicol. Environ
Safe. 11:144-152.
Copyright © National Academy of Sciences. All rights reserved.
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inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
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30
Vanadium
INTRODUCTION
Vanadium (V), atomic number 23, is a brighit wiiite (NRC,
1980) or a soft silvery gray metal in the pure state (WHO,
2001). Vanadium was named after Vanadis, the Norse god-
dess of beauty, youth, and luster, in 1830 by Nils Sefstrom,
due to the striking colors of vanadium-containing crystals
and salts (Nechay et al., 1986). The two natural isotopes for
vanadium are V-^° and V-^' of which V^' occurs at a 99.76
percent frequency in the environment (Stoecker and
Hopkins, 1984). Metallic vanadium, a corrosion-resistant
metal, does not occur in a pure form in nature, but exists in
the oxidative states -1 to +5 with +3, +4, and +5 being the
most common. The pentavalent state (H-5) is the most com-
mon form of the element found in the environment with H-3
and +4 states being quickly oxidized in the presence of water
to H-5. The most stable forms of vanadium are the quadri-
valent salts (Barceloux, 1999). Vanadium pentoxide, a red-
yellow or green crystalline powder, is the most commonly
available form of vanadium (WHO, 2001). The compounds
containing vanadium that are generally used in the toxicology
studies are ammonia metavanadate (NH4VO3); sodium
metavanadate (NaVOj); sodium ortho vanadate (Na3V04); cal-
cium orthovanadate (Ca3(V03)2); vanadyl sulphate (VOSO4);
vanadium pentoxide (VjOj); vanadyl sulphate pentahydrate
(VOS04-5H20); and bis(maltolato)oxovanadium (BMOV).
Vanadium is present in more than 50 naturally occur-
ring minerals, and in oil and coal. The most important
minerals containing vanadium used for industrial pur-
poses are patronite (contains 10 percent vanadium and
iron oxides), carnotite (K20-2U203-V205-3H20), roscoelite
(2K20-2Al203(Mg, Fe)O-3V2O5-10SiO2-4H2O), and vana-
dinite (9PbO-3V205-PCl2) (Budavari et al, 1989). Vanadium
is mined in South Africa, Russia, the United States, Finland,
and China. Vanadium pentoxide is contained in a vanadium
slag produced during the smelting of iron ore (WHO, 2001).
Vanadium pentoxide may also be present in amounts as high
as 10-15 percent in the dust, soot, boiler scale, and fly ash
that accumulates from the burning of vanadium-rich oils,
certain oils that are found in Venezuela and Mexico (Leonard
and Gerber, 1994). Vanadium is used in relatively small por-
tions in some steels: cutting steel, high-strength steel, and
wear-resistant iron (NRC, 1980). Vanadium reviews have
been provided by the NRC, 1980; Jandhyala and Hom, 1983;
Stoecker and Hopkins, 1984; Lagerkvist et al., 1986; WHO,
1988; Barceloux, 1999; and WHO, 2001.
ESSENTIALITY
Vanadium is an essential element in various enzymes in
algae, bacteria, fungi, and lichens (Nielsen, 2000). The en-
zymes include haloperoxidases, which catalyze the oxida-
tion of halide ions by hydrogen peroxide to facilitate the
formation of a carbon-halide bond. Some bacteria require
vanadium for the enzymatic reaction of reducing nitrogen
gas to ammonia.
There are conflicting reports as to the essentiality of va-
nadium for animals. The National Research Council (NRC,
1980) concluded that in the species tested, vanadium is es-
sential for normal growth and proper physiological function.
However, Nielsen (1995) concluded vanadium research con-
ducted between 1971 and 1974 (NRC, 1980) was inconclu-
sive as the amount of vanadium in control treatments was
higher than the amount of vanadium available in normal di-
ets, and the form of vanadium used in the studies had a very
high availability. This led to difficulty in determining if the
results from these studies were deficiency signs or if the level
of vanadium used in the controls actually had significant
pharmacological actions (Nielsen, 1985; French and Jones,
1993; Nielsen, 1995). The composition of the diet also has
been found to affect the response of rats to vanadium and
many of the early deficiency studies on vanadium fed diets
that were not balanced for nutrients (Nielsen, 1985).
Reviews by Nielsen (1995, 2000) found circumstantial
evidence that vanadium was an essential nutrient for rats and
goats. Anke et al. (1986, 1989) conducted a set of experi-
398
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VANADIUM
399
ments on goats to determine vanadium essentiality. Goats
that received less tlian 10 ng V/g of diet had higher incidents
of abortion, produced less milk in the first 56 days of lacta-
tion, and had a lower conception rate on first insemination
than goats fed the 0.5 or 2 |jg V/g diet. Approximately 40
percent of the kids from the vanadium-deficient goats died
within 7 to 91 days of life (Anke et al„ 1989). Only 8 percent
of the kids from the goats that received 2 [ig V/g diets died
during the same time. The vanadium-deficient goats had
higher serum creatine and p-lipoprotein, and lower serum
glucose levels (Anke et al., 1986). They also had skeletal
deformations in the forelegs and a thickening of the forefoot
tarsal joints (Anke et al., 1986). Uthus and Nielsen (1990)
found vanadium-deprived rats had a higher thyroid weight
and thyroid-to-body weight ratio than controls fed 1 [ig V/g
diet. Other deficiency signs of vanadium in rats were
decreased erythrocyte glucose-6-phosphate hydrogenase,
cecal total carbonic anhydrase, and an altered response to
high and low dietary iodide (Nielsen, 1996). However,
because a defined biochemical function has not been identi-
fied in higher animals, vanadium is currently not considered
an essential element.
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Concerns on the reliability of tests to analyze vanadium
have been raised (Lagerkvist et al., 1986). The low amount
of vanadium in the environment and especially in animal
and plant tissues makes it difficult to measure amounts accu-
rately using older methods of analysis. Contamination of
samples from vanadium present in air and other sources such
as stainless steel and cutting steels can alter the amounts in a
sample. Seller (1995) reviewed the methods available for
analyzing the vanadium content in biological materials. In
the past, spectrophotometric methods have been used to de-
termine low concentrations of vanadium, but the risk of er-
roneous results due to the laborious sample preparation and
the lack of sensitivity of the test is high. The most common
method for vanadium analysis in biological materials is
atomic absorption spectrometry (Seller, 1995), but it only
has a detection limit down to 0.2 ng/ml, whereas neutron
activation analysis (NAA) can be used to detect lower levels
(Lagerkvist et al., 1986). The NAA method can detect vana-
dium below 0.2 ng/ml and has been used to detect the erro-
neous results of methods used for vanadium analysis in ear-
lier studies.
sorbed from the digestive tract at an efficiency of 1 percent
or less. Conklin et al. (1982) reported the uptake of 40 |ig of
vanadium given orally to rats as radioactive VjO^ was 2.6
percent. Roshchin et al. (1980) found similar results to
Conklin et al. (1982), but other studies have reported less
than 5 percent absorption (French and Jones, 1993) to more
than 10 percent absorption of ingested vanadium (Bogden et
al., 1982; Wiegmann et al., 1982). Studies cited by French
and Jones (1993) suggest that the length of the fasting period
and composition of the experimental diet may have resulted
in higher dietary efficiencies. Thompson et al. (2002) tested
the bioavailability of three vanadium-containing com-
pounds — ammonium metavanadate, vanadyl sulfate, and
bis(maltolato)oxyvanadium — that differ in chelation and
oxidation states in male rats weighing 180-210 g. They
found neither oxidation state nor complexation alone were
adequate predictors of relative absorption or tissue vanadium
uptake. In general for nonruminants, most ingested vana-
dium is converted to vanadyl (VO^"*") in the stomach; how-
ever, vanadate (HV04^") escaping conversion is absorbed
three to five times more effectively from the gastrointestinal
tract then vanadyl (Nielsen, 1995). The excretion of absorbed
vanadium is fairly rapid with 40-60 percent of a given dose
eliminated in one to three days after exposure (Barceloux,
1999). Absorbed vanadium is excreted mainly by the kidneys
(NRC, 1980; Nielsen, 1995) with a minor amount excreted
in the feces. Skin is only a minor route of exposure for vana-
dium (Barceloux, 1999).
Metabolic Interactions
Vanadium's high number of oxidative states makes it a
very multifunctional element in the body and likely contrib-
utes to its ability to have effects at relatively low levels. In
mammals, vanadium can function as a growth factor, a mito-
gen, and an anti-diabetic agent (Davison et al., 1997). Vana-
dium compounds have been shown to mimic the biological
actions of insulin (Dai etal., 1995; Tsiani and Fantus, 1997).
Vanadyl readily binds to nucleic acids, amino acids, phos-
phates, phospholipids, glutathione, oxalate, citrate, and lactate
excreta (Nechay, 1984). Vanadium inhibits a large number
of enzyme systems in vitro including ATPases, phosphates,
and phosphoric transfer enzymes. The vanadate ion is one of
the most potent inhibitors of the NaVK"^ ATPase pump
(Jandhyala and Hom, 1983; Barceloux, 1999). However,
specific activation or inhibition of an enzyme by vanadium
has not been found (Nielsen, 1995).
REGULATION AND METABOLISM
Absorption and IVIetabolism
French and Jones (1993) and Nielsen (1995) have pro-
vided reviews on the regulation and metabolism of vana-
dium. Studies cited in NRC (1980) indicate vanadium is ab-
SOURCES AND BIOAVAILABILITY
Environmental Exposure
Vanadium pentoxide is the most important vanadium-
containing compound used in industry. High amounts of
vanadium can be present in the air around industrial
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400
MINERAL TOLERANCE OF ANIMALS
complexes that use vanadium pentoxide. The WHO (2001)
reported air levels of vanadium range from 0.001 to 1,460
ng/m-^. The concentration of vanadium in the ocean crust is
approximately 250 mg/kg, and 160 mg/kg in the continental
crust (Leonard and Gerber, 1994). Rain in North America
and Europe has been found to contain 1.1-46 |Jg/L of vana-
dium (Galloway et al., 1982). Both fresh water and sea water
contain less than 3 |Jg/L (Hamada, 1998). Vanadium con-
centrations in marine organisms are quite variable with
planktonic organisms estimated to be 1 mg/kg DM and fish
.08-3 mg/kg DM (WHO, 2001). The average concentration
of vanadium in soils worldwide is approximately 100 mg/kg
(WHO, 2001). The average concentration in the United States
was found to be 60 mg/kg and ranged between < 7 mg/kg to
500 mg/kg (WHO, 2001).
Food is the major source of exposure to vanadium for the
general population. Vanadium is usually present in food in
the form of vanadyl (French and Jones, 1993) and at concen-
trations of less then 1 ng V/g (Barceloux, 1999). Foods that
are relatively high in vanadium (0.05-2 |Jg/g) include black
pepper, mushrooms, parsley, dill seed, shellfish, and some
prepared foods (Nielsen, 1991). Dairy products, meat, sea-
food, and whole grains have vanadium concentrations in the
5-30 ng/g range (McDowell, 2003). The estimated dietary
intake of vanadium by humans is 10-60 |Jg/day (Barceloux,
1999).
A concern in animal feed is the concentration of vanadium
in rock phosphates used as phosphorus sources in diets. The
NRG (1980) reported that some rock phosphates may contain
up to 6,000 mg/kg vanadium. Goncentrations of vanadium in
phosphorus sources vary by purity, with monocalcium phos-
phates ranging from 46-796 mg/kg, dicalcium phosphates
ranging from 36-185 mg/kg, and thermochemically produced
defluorinated phosphates ranging from 20-164 mg/kg
(Sullivan et al., 1994). Grazing animals can be exposed to
higher levels of vanadium through unavoidable ingestion of
soil (NRG, 1980; McDowell, 2003).
Supplementation Considerations
Nielsen (2000) reported that vanadium has become a com-
ponent in a large number of pills and other dietary supple-
ments to enhance strength and ward off diabetes. This trend is
caused by the discovery that vanadium mimics the action of
insulin in animal models (Poucheret et al., 1998). However,
Domingo's (2000) review on diabetes studies with rats found
that there are many complications associated with supplement-
ing vanadium for this purpose, and toxic effects from long-
term buildup of vanadium in the tissues is of great concern.
TOXICOSIS
Reviews on vanadium toxicity have been provided by the
NRG (1980), Leonard and Gerber (1994), and Domingo
(1994, 1996, 2000). The major clinical signs and effects of
vanadium toxicosis are a reduction in weight gain of grow-
ing animals, weight loss in adult animals, and death. In rats,
toxic levels of vanadium ingestion led to reductions in repro-
duction, reduced fluid intake, diarrhea, and changes in be-
havior and learning patterns. In laying hens, elevated vana-
dium intake has led to reduced egg production, feed intake,
feed conversion efficiency, and albumin quality as measured
by Haugh units. Vanadium appears to inhibit enzymes and
damage cells through lysis. Vanadate has been found to activate
cardiac adenylate cyclase and inhibits the (Na, K)-ATPase
pathway and many other phosphohydrolase enzymes through
its ability to mimic phosphate in a transitional state (Kustin,
1998).
Higti Quantities and Acute
Llobet and Domingo (1984) reported the LDjq (14-day)
for rats and mice given oral administration of sodium
metavanadate (NaVOj) and vanadyl sulphate pentahydrate
(VOS04-5H20). For rats, the LD,,, was 98 mg/kg-' BW for
NaVOj and 448 mg/kg-' BW for V0S04-5H20. In mice, the
LD50 (14-day) was 74.6 mg/kg"' BW for NaVO, and 467.2
mg/kg-' BW for VOS04-5H20. The toxicity of vanadium
increases as the valence increases and for vanadyl (V"^"*) the
LDjQ (14-days) was determined to be 90.3 and 94.2 mg/kg
BW for mice and rats, respectively. The LDjg (14-day) for
vanadate (V"*"^) was determined to be 40 and 31.2 mg/kg-'
BW in mice and rats, respectively. Toxicity of orally ingested
vanadium is dependent on the valence of the vanadium ele-
ment with higher valences being more toxic and having a
lower LDjQ than lower valances.
Hansard et al. (1982) determined the toxicity of ammo-
nium metavanadate, calcium orthovanadate, and calcium
pyrovanadate given by capsule to 41 -kg BW wethers. An
initial dose equivalent to 100 mg of elemental vanadium of
each compound was given. Quantity was increased by 50 mg
per two-day intervals to determine the amount of vanadium
necessary to decrease feed intake to 75 percent of control-
fed wethers. The initial decline in feed intake was observed
at vanadium intakes of 400-500 mg/head/day or 9.6-12 mg/kg
BW. The decline in feed intake was accompanied by
diarrhea. All three compounds were similar in toxicity as
they brought about the decline in feed intake at approxi-
mately the same time. Tissue analysis of the sheep showed
extensive mucosal hemorrhage of the small intestine and
petechial subcapsular hemorrhage of the kidneys for all com-
pounds dosed. Acute toxicosis was determined by giving 3
sheep a dose of 40 mg of vanadium as NH4V03/kg BW. The
toxic levels killed two sheep within 80 hours and elevated
the vanadium content in kidney, spleen, bone, muscle, liver,
and lung tissues of the others.
NRG (1980) reported that a dose of 20 mg V/kg BW given
orally to calves as ammonium vanadate resulted in diarrhea,
dehydration, emaciation, and prostration that lasted for
3 days. The gross pathological changes were hemorrhagic
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VANADIUM
401
inflammation of the intestinal tract, ruminal ulcers, diffuse
hemorrhage around the kidney and heart, and congestion of
the liver and lungs.
The WHO (2001) has summarized the toxicity (LC50) of
vanadium compounds for fresh- and saltwater fish. The LC^q
(96 hour) for freshwater trout and salmon ranged from 6-24
mg of vanadium per liter of water. Toxicity of vanadium
appears to increase with increasing water hardness and as
pH increases from 5.5 to 8.8 (Stendahl and Sprague, 1982).
Low Quantities and Clironic
Toxicosis via ingestion of vanadium through food is very
uncommon in humans. The most common animal models
used in vanadium toxicology literature are chickens and rats.
The ingestion of vanadium can alter the function of the ru-
men. An in vitro study found the addition of 7 mg/kg of
vanadium as sodium ortho- or metavanadate to the rumen
fluid of lambs reduced DM digestibility (NRC, 1980).
A number of studies on the toxicity of vanadium in the diet
and water are summarized in Table 30-1. A decrease in the
albumin quality of eggs from laying hens was apparent when
contaminated phosphorus sources provided as little as 4.6 mg/kg
of vanadium in the total diet (Sell et al., 1982). Reductions in
albumin quality were proportional to the concentration of
vanadium from NH4VO3 in the diet. At 27.5 mg/kg vanadium
in diets of laying hens, albumin quality and egg production
were significantly lower at the end of the first 4 weeks of the
study than lower dietary treatments, and chickens did not
recover as fast from this high dosage after vanadium was
reduced in the diet (Sell et al., 1982). Growing chicks fed diets
containing 50 mg/kg of vanadium as calcium orthovanadate
gained less weight (205 vs. 237 g) during the first 28 days of
life and had lower liver, gizzard, spleen, and bursa weights,
but not as a percent of BW, compared to chicks fed a control
starter diet (Kubena et al., 1985). Fifty-week-old laying hens
fed 40 mg/kg of added vanadium in their diet for 7 weeks had
decreased albumin quality (18.7 Haugh unit decrease), low-
ered egg weights (by 3.8 g), lowered egg production (by 28.8
percent per day), and a loss in BW of 149 g (Ousterhout and
Berg, 1981). The total feed intake for hens fed a 40 mg/kg
added vanadium diet was 880 g less than the control hens over
the seven-week treatment period.
Paternain et al. (1990) found that administrating vanadyl
sulphate pentahydrate by gavage to pregnant mice at quanti-
ties of 75 and 150 mg/kg"' BW on days 6-15 of gestation
resulted in a reduction in maternal weight that was dose re-
lated, and lower liver and kidney weights than control mice.
However, administration of vanadium at either dosage by
gavage did not affect feed intake.
Hilton and Bettger (1988) reported that rainbow trout refused
diets containing 493 mg V/kg of diet. Concentrations as low as
10.2 mg of sodium orthovanadate/kg of diet reduced weight
gain during a 12-week feeding period.
Factors Influencing Toxicity
Domingo (1996) reviewed the influence of vanadium on
reproduction and development in rats and mice and found
the effects of vanadium toxicosis were dependent on many
factors, including the valence of the vanadium compound,
the chemical form of the vanadium compound, the period of
dosing, the length of exposure, and the size of the dose. The
toxicity of vanadium compounds tends to increase as the
valence increases (Nechay et al., 1986). Vanadium toxicity
is fairly low when it is ingested, moderate when it is inhaled,
and high when it is injected (Nechay et al., 1986).
Various studies have tested the ability of different com-
pounds to reduce the toxicity of vanadium. Benabdeljelil and
Jensen (1990) conducted a series of experiments testing the
effectiveness of ascorbic acid and chromium in countering
the negative effects of dietary vanadium on interior egg
quality. Ascorbic acid fed at 100-5,000 mg/kg of diet effec-
tively protected hens against decreases in interior egg quality
at 10 mg/kg of diet feeding of vanadium, but did not prevent
a reduction in total egg weight. Chromium at 10 or 50 mg/kg
in diets containing 10 mg/kg vanadium did not prevent a
decrease in albumin quality. This also was true when chro-
mium was added at 30 or 150 mg/kg to diets containing 30
mg/kg added vanadium. A study by Miles et al. (1997) found
that the antioxidants vitamin E, ascorbic acid, and beta-
carotene could be used in diets containing 10 mg/kg vanadium
to partially restore interior egg quality. Ousterhout and Berg
(1981) found that the inclusion of ascorbic acid at 0.4-0.5
percent of the diet effectively protected the hen from
reductions in albumin quality, BW, and egg production from
vanadium levels of up to 40 mg/kg. However, ascorbic acid
didn't counteract vanadium's reduction in egg weight. Re-
placing soybean meal with 20 percent cottonseed meal had
the same effect as the ascorbic acid. Ousterhout and Berg
(1981) found that adding ethylenediamine tetraacetic acid at
levels four to eight times the molar concentration of vana-
dium and varying the protein percentage in the diet using
soybean meal had no consistent effect in countering the
effects of vanadium. Replacing the grain with sucrose and
replacing the soybean meal with herring fish meal were
found to intensify the negative affects of vanadium on per-
formance. Studies by Kubena et al. (1985, 1986) found a
toxicity-enhancing synergism between orchratoxin A and
vanadium in male chicks. Diets containing as little as 2.5
mg/kg orchratoxin A and 12.5 mg of vanadium resulted in
lower weight gain than when orchratoxin A was fed alone.
The chelating agent, Tiron (sodium 4, 5-
dihydroxybenzamine-l,3-disulfonate), when administered at
235-470 mg/kg BW to rats that have received 16 mg/kg BW
othorvanadate orally per day for 6 weeks, was shown to be
an effective antidote in vanadium-loaded rats (Sanchez et
al., 1999). Vanadium-loaded rats exhibited altered behavior
of avoidance to stimuli in an open field, but reverted back to
normal behavior with Tiron injections. Yamaguchi et al.
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402
MINERAL TOLERANCE OF ANIMALS
(1989) found that injections of zinc sulfate (15.3 pmol of
Z/100 g BW) when administered simultaneously with
20 pmol of V/100 g BW in weanling rats prevented the toxic
effects of vanadium on bone metabolism. However,
Zaporowska and Wasilewski (1992) found that including
zinc (in drinking water) with the dose of vanadium caused
the rats to have a more pronounced reduction of feed intake
than the vanadium itself.
TISSUE LEVELS
The distribution of vanadium varies throughout the dif-
ferent tissues in the body (Table 30-2 and Table 30-3); most
vanadium accumulates in the organ tissues. The highest con-
centrations are in the liver, kidney, and bone (French and
Jones, 1993). Feeding 9.6-12 mg/kg BW of vanadium from
ammonium metavanadate, calcium pyro vanadate, or calcium
orthovanadate to wethers increased vanadium levels in
muscle, lung, liver, and kidney tissue by 10-, 13-, 8- and 33-
fold, respectively, over control-fed wethers with tissue level
increases similar across all three sources of vanadium
(Hansard et al., 1982). In an acute experiment with three
sheep dosed with vanadium at 40 mg/kg BW, vanadium
levels in kidney tissue were increased 69-fold at the time of
death (Hansard et al., 1982). Vanadium concentration in the
kidney tissue was the highest of all tissues tested, averaging
25.83 mg/kg on a DM basis. The lowest tissue vanadium
concentration was in muscle, averaging 0.63 mg/kg DM.
Paternain et al. (1990) found vanadyl sulphate
pentahydrate administered orally at doses of 37.5, 75, and
150 mg/kg BW/day to pregnant mice on days 6-15 of gesta-
tion linearly increased concentrations of vanadium in the
liver, kidney, spleen, whole fetus, and placenta as dosage
level increased. Sanchez et al. (1998) administered
metavanadate orally to rats at 4.1, 8.2, and 16.4 mg/kg of
BW/day for 8 weeks. Tissues levels of vanadium increased
as the amount of vanadium dosed increased. Lowest tissue
concentration of vanadium was in the brain, followed by
muscle, liver, kidneys, bone, and spleen — except at the 16.4
mg/kg dose where bone became the tissue with the highest
vanadium concentration. Tissue concentrations ranged from
0.029 |Jg V/g tissue WW in brain at the 4.1 mg/kg dose to
2.852 |jg V/g tissue WW in bone at the 16.4 mg/kg dose.
Other tissue contents are summarized in Tables 30-2 and 30-3.
MAXIMUM TOLERABLE LEVELS
NRC (1980) suggested the maximum tolerable dietary
levels for vanadium: 50 mg/kg for cattle and 10 mg/kg for
poultry. More recent research indicates poultry can tolerate
up to 25 mg/kg of vanadium in diets and possibly up to
50 mg/kg (depending on the source of vanadium) without
significant decreases in weight gain or health effects (Table
30-1). However, egg albumin quality declines at levels as
low as 4.6 mg/kg of vanadium in diets and egg weights de-
crease proportionally as the amount of vanadium in diets
increase. Thus, for concerns about egg quality, the previous
10 mg/kg of diet maximum tolerable level appears appropri-
ate, but slightly high for maximum egg quality. In mice, the
maximum tolerable levels are not clearly definable with ad-
verse effects on weight gain and reproduction occurring be-
tween 6 and 17 mg/kg BW intake of vanadium per day. Rats
change their learning behavior at intakes of vanadium as low
as 1 .7 mg/kg BW/day, but intakes above 7 mg/kg B W appear
necessary to observe decreased weight gain. At intakes of
10 mg V/kg BW, sheep have reduced feed intake and
develop diarrhea.
FUTURE RESEARCH NEEDS
The effect of vanadium per se and vanadium sources on
toxicosis and on physiological changes in rats and poultry
has been researched. Information on health, alterations in
production, and even toxicity of vanadium in many domestic
animal species, particularly ruminants, and fish is unavail-
able. Additional research on the interaction of antioxidants,
mycotoxins, and overall nutrient content of the diet and va-
nadium toxicity is needed.
SUMMARY
Vanadium has recently been found to be an essential ele-
ment in rats and goats. Vanadium is present in the environ-
ment in low but adequate levels. There is a low risk of ani-
mals suffering from a deficiency in vanadium; however,
vanadium toxicity can occur and in certain species at fairly
low intake levels. In vitro, vanadium has been shown to in-
hibit (Na, K)-ATPase and influence the function of other
enzyme systems. Vanadium administered to sheep at an ever-
increasing rate caused a strong drop in feed intake at the
400-500 mg/day level. When administered a 40 mg/kg dose
of vanadium as sodium orthovanadate, sheep died within 80
hours. Signs of toxicosis of vanadium in laying hens are usu-
ally a reduction in albumin quality at dietary vanadium lev-
els as low as 5 mg/kg of diet; as levels increase, egg produc-
tion decreases, growth rate stops, and laying hens can
atrophy. Levels of 100 mg/kg of vanadium in laying hens'
diets can cause death. Low levels of vanadium have been
shown to modify behavior in rats and mice. The largest con-
cern for vanadium in feedstuff s is the concentration of vana-
dium in phosphorus mineral sources, as vanadium concen-
trations in other feedstuff s are low.
REFERENCES
Anke, M., B. Groppel, K. Grulin, M. Langer, and W. Ai-nhold. 1989. The
essentiality of vanadium for animals. Pp. 17-27 in 6th International
Trace Element Symposium, University of Leipzig- Jena, Germany.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
VANADIUM
403
Anke, M., B. Groppel, K. Gruhn, T. Kosla, M. Szilagyi. 1986. New research on
vanadium deficiency in raminants. Pp. 1266-1275 in 5. Spurenelement—
Symposium der Karl Marx-Universiteat Leipzig and der Friedrich—
Schiller— Universiteat Jena, M. Anke, W. Bauman, H. Braunlick, Chi'.
Brackner, and B. Groppel, eds. Germany: University of Leipzig- Jena.
Barceloux, D. G. 1999. Vanadium. Clin. Toxicol. 37:(2)265-278.
Benabdeljelil, K., andL. S. Jensen. 1990. Effectiveness of ascorbic acid and
chromium in counteracting the negative effects of dietary vanadium on
interior egg quality. Poult. Sci. 69:781—786.
Bogden, J. D., H. Higashino, M. A. Lavenhar, J. W. Baumen, Jr., F. W.
Kemp, and A. Aviv. 1982. Balance and tissue distribution of vanadium
after short-term ingestion of vanadate. J. Nutr. 1 12:2279-2285.
Bressman, R. B., R. D. Miles, C. W. Comer, H. R. Wilson, and G. D.
Butcher. 2002. Effect of dietary supplementation of vanadium in com-
mercial egg-type laying hens. J. Appl. Poult. Res. 11:46-53.
Budavari, S., M. J. O'Neil, A. Smith, and P. H. Heckelman, eds. 1989. The
Merck Index 1 1th ed. Rahway, NJ: Merck & Co.
Conklin, A. W., C. S. Skinner, T. L. Felten, and C. L. Sanders. 1982. Clear-
ance and distribution of intratrachially instilled "^^vandium compounds
in the rat. Toxicol. Lett. 1 1 : 199-203.
Dai, S., H. Thompson, and J. H. McNeill. 1994. One-year treatment of
streptozotocin-induced diabetic rats with vanadyl sulphate. Pharmacol.
Toxicol. 74:101-109.
Dai, S., E. Vera, and J. H. McNeill. 1995. Lack of hematological effect of
oral vanadium treatment in rats. Pharmacol. Toxicol. 76:263-264.
Davis, E. G., R. D. Miles, G. D. Butcher, and C. W. Comer. 2002. Effects of
dietary vanadium on performance and immune responses of commer-
cial egg-type laying hens. J. Appl. Anim. Res. 22:113—124.
Davison, A., L. Kowalski, X. Yin, and S. S. Tsang. 1997. Vanadium as a
modulator of cellular regulation — The role of redox reactivity . Pp. 229—
233 in Trace Elements in Man and Animals — 9: Proceedings of the
Ninth International Symposium on Trace Elements in Man and Ani-
mals, P. W. F. Fischer, M. R. L'Abbe, K. A. Cockell, and R. S. Gibson,
eds. Ottawa, Canada: National Research Council Research Press.
Domingo, J. L. 1994. Metal-induced developmental toxicity in mammals: a
review. J. Toxocol. Env. Health 42:123-141.
Domingo, J. L. 1996. Vanadium: a review of the reproductive and develop-
mental toxicity. Reprod. Toxicol 10:175-182.
Domingo, J. L. 2000. Vanadium and diabetes. What about vanadium toxic-
ity? Mol. Cell. Biochem. 203:185-187.
Domingo, J. L., J. M. Llobet, J. M. Tomas, and J. Corbella. 1985. Short-
term toxicity studies of vanadium in rats. J. Appl. Toxocol. 5:418^21.
Eyal, A., and E. T. Moran, Jr. 1984. Egg changes associated with reduced
interior quality because of dietary vanadium toxicity in the hen. Poult.
Sci. 63:1378-1385.
French, R. J., and P. J. H. Jones. 1993. Role of vanadium in nutrition: me-
tabolism, essentiality, and dietary considerations. Life Sci. 52:339-346.
Galloway, J., J. Thomton, S. Norton, H. Volchok, and R. MacLean. 1982.
Trace metals in atmospheric deposition: a review and assessment.
Atmos. Environ. 16:1677-1700.
Ganguli, S., D. J. Reuland, L. A. Franklin, D. D. Deakins, W. J. Johnston,
and A. Pasha. 1994. Effects of maternal vanadate treatment on fetal
development. Life Sci. 55:(16)1267:1276.
Hansard 11, S. L., C. B. Ammerman, P. R. Henry, and C. F. Simpson. 1982.
Vanadium metabolism in sheep. 1. Comparative and acute toxicity of
vanadium compounds in sheep. J. Anim. Sci. 55:344—349.
Hilton, J., andW. Bettger. 1988. Dietary vanadium toxicity in juvenile rain-
bow trout: a preliminary study. Aquatic Toxicol. 12:63—71.
Jandhyala, B. S., and G. J. Hom. 1983. Physiological and pharmacological
properties of vanadium. Life Sci. 33:1325-1340.
Kubena, L. F., and T. D. Phillips. 1983. Toxicity of vanadium in female
leghorn chickens. Poult. Sci. 62:47-50.
Kubena, L. F., R. B. Harvey, O. J. Fletcher, T. D. Phillips, H. H.
MoUenhauer, D. A. Witzel, and N. D. Heidelbaugh. 1985. Toxicity of
ochratoxin A and vanadium on growing chicks. Poult. Sci. 64:620-628.
Kubena, L. F., R. B. Harvey, T. D. Phillips, and O. J. Fletcher. 1986. Influ-
ence of ochratoxin A and vanadium on various parameters in growing
chicks. Poult. Sci. 65:1671-1678.
Kustin, K. 1998. Perspectives on vanadium biochemistry. Pp. 170-185 in
Vanadium Compounds: Chemistry, Biochemistry, and Therapeutic Ap-
plications, A. S. Tracey and D.C.Crans, eds. Washington, D.C.: Ameri-
can Chemical Society.
Lagerkvist, B., G. F. Nordberg, and V. Vouk. 1986. Vanadium. Pp. 639-
663 in Handbook on the Toxicology of Metals, 2nd ed., L. Friberg, G. F.
Nordberg, and V. Vouk, eds. Amsterdam: Elsevier Science Publishers
B.V.
Leonard, A., and G. B. Gerber. 1994. Mutagenicity, carcinogenicity, and
teratogenicity of vanadium compounds. Mutat. Res. 317:81—88.
Llobet, J. M., and J. L. Domingo. 1984. Acute toxicity of vanadium com-
pounds in rats and mice. Toxicol. Lett. 23:227-231.
Llobet, J. M., M. T. Colomina, J. J. Sirvent, J. L. Domingo, and J. Corbella.
1993. Reproductive toxicity of vanadium in male mice. Toxicology
80:199-206.
McDowell, L. R. 2003. Chromium, newly discovered, and other trace ele-
ments. Pp. 497-521 in Minerals in Animal and Human Nutrition.
Amsterdam: Elsevier Science Publishers B.V.
Miles, R. D., S. F. O'Keefe, G. D. Butcher, C. W. Comer, and D. Williams.
1997. Influence of vitamin E, ascorbic acid, and beta-carotene on laying
hens fed diets containing 10 ppm supplemental vanadium. Poult. Sci.
76(Suppl. l):61(Abstr.).
Morgan, A. M., and O. S. El-Tawil. 2003. Effects of ammonium
metavanadate on fertility and reproductive performance of adult male
and female rats. Pharmacol. Res. 47:75-85.
NRC (National Research Council). 1980. Vanadium. Pp. 534-552 in Min-
eral Tolerance of Domestic Animals. Washington, D.C.: National Acad-
emy Press.
Nechay, B. R. 1984. Mechanisms of action of vanadium. Annu. Rev.
Pharmacol. Toxicol. 24:501-524.
Nechay, B. R., L. B. Nanninga, P. S. E. Nechay, R. L. Post, J. J. Grantham,
1. G. Macara, L. F. Kubena, T. D. Phillips, and F. H. Nielsen. 1986. Role
of vanadium in biology. FASEB J. 45:123-132.
Nielsen, F. H. 1985. The importance of diet composition in ultratrace ele-
ment research. J. Nutr. 1 15:1239-1247.
Nielsen, F. H. 1991. Nutritional requirements for boron, silicon, vanadium,
nickel, and arsenic: current knowledge and speculation. FASEB J.
5:2661-2667.
Nielsen, F. H. 1993. Ultratrace elements of possible importance in human
health: an update. Prog. Chn. Biol. Res. 380:355-376.
Nielsen, F. H. 1995. Vanadium in mammalian physiology and nutrition.
Met. Ions Biol. Syst. 31:543-573.
Nielsen, F. H. 1996. How should dietary guidance be given for mineral
elements with beneficial actions or suspect of being essential? J. Nutr.
126:2377S-2385S.
Nielsen, F. H. 2000. Importance of making dietary recommendations for ele-
ments designated as nutritionally beneficial, pharmacologically benefi-
cial, or conditionally essential. J. Trace Elem. Exp. Med. 13:113-129.
Ousterhout, L. E., and L. R. Berg. 1981. Effects of diet composition on
vanadium toxicity in laying hens. Poult. Sci. 60:1152—1159.
Paternain, J. L., and J. L. Domingo, M. Gomez, A. Ortega, and J. Corbella.
1990. Developmental toxicity of vanadium in mice after oral adminis-
tration. J. Appl. Toxicol. 10:181-186.
Poggioli, R., R. Arletti, A. Bertolini, C. Frigeri, and A. Benelli. 2001.
Behavioral and developmental outcomes of prenatal and postnatal
vanadium exposure in the rat. Pharmacol. Res. 43:341—347.
Poucheret, P., S. Verma, M. D. Grynpas, and J. H. McNeill. 1998. Vana-
dium and diabetes. Mol. Cell. Biochem. 188:73-80.
Roman, R. J., J. V. Bonventre, P. Silva, and C. Lechene. 1981. Sodium
orthovanadate diuresis in rats. J. Pharmacol. Exp. Ther. 218:168-174.
Roshchin, A. V., E. K. Ordzhonikidze, and 1. V. Shalganova. 1980. Vana-
dium — toxicity, metabolism, carrier state. J. Hyg. Epidemiol. Microbiol.
Immunol. 24:377-383.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
404
MINERAL TOLERANCE OF ANIMALS
Sanchez, D. J., M. T. Colomina, and J. L. Domingo. 1998. Effects of vana-
dium on activity and learning in rats. Physiol. & Behav. 63:345-350.
Sanchez, D. J., M. T. Colomina, J. L. Domingo, and J. Corbella. 1999.
Prevention by sodium 4,5-dihydroxybenzene— 1,3-disulfonate (Tiron)
of vanadium-induced behavioral toxicity in rats. Biol. Trace Elem. Res.
69:249-259.
Seller. H. G. 1995. Analytical procedures for the determination of vana-
dium. Met. Ions Biol. Syst. 31:671-688.
Sell, J. L., J. A. Ai-thur, and 1. L. Williams. 1982. Adverse effect of dietary
vanadium, contributed by dicalcium phosphate, on albumen quality.
Poult. Sci. 61:2112-2116.
Sell, J. L., C. Y. Davis, and S. E. Scheideler. 1986. Influence of cottonseed
on vanadium toxicity and vanadium distribution in body tissues of lay-
ing hens. Poult. Sci. 65:138-146.
Stendahl, D., and J. Sprague. 1982. Effects of water hardness and pH on
vanadium lethality to rainbow trout. Water Res. 16:1479-1488.
Stoecker, B. J., and L. L. Hopkins. 1984. Vanadium. Pp. 239-255 in Bio-
chemistry of the Essential Ultra Trace Elements, E. Frieden, ed. New
York: Plenum Publishers.
Sullivan, T. W., J. H. Douglas, and N. J. Gonzalez. 1994. Levels of various
elements of concern in feed phosphates of domestic and foreign origin.
Poult. Sci. 73:520-528.
Sutly, J. P., R. D. Miles, C. W. Comer, and M. Balaban. 2001. The influence
of vanadium on pigmentation of brown-shelled eggs. Poult. Sci.
80:1039(Abtr.).
Thompson, K. H., Y. Tsukada, Z. Xu, M. Battell, J. H. McNeill, and C.
Orvig. 2002. Influence of chelation and oxidation state on vanadium
bioavailability, and their effects on tissue concentrations of zinc, cop-
per, and iron. Biol. Trace Elem. Res. 86:31^14.
Toussant, M. J., and J. D. Latshaw. 1994. Evidence of multiple metabolic
routes in vanadium's effects on layers. Ascorbic acid differential effects
on prepeak egg production parameters following prolonged vanadium
feeding. Poult. Sci. 73:1572-1580.
Tsiani, E., and 1. G. Fantus. 1997. Vanadium compounds: biological actions
and potential as pharmacological agents. Trends Endocrinol. Metab.
8:51-58.
Uthus, E. O., and F. H. Nielsen. 1990. Effect of vanadium, iodine and their
interaction on growth, blood variables, liver trace-elements and thyroid
status indexes in rats. Magnesium Trace Elem. 9:1 19— 226.
WHO (World Health Organization). 1988. Vanadium. Pp. 1-170 in Envi-
ronmental Health Criteria 81. Geneva: WHO.
WHO (World Health Organization). 2001. Vanadium pentoxide and other
inorganic vanadium compounds. Concise International Chemical As-
sessment Document 29. Geneva: WHO. Online. Available at http://
www.inchem.org/documents/cicads/cicads/cicad29.htm. Accessed
April 22, 2005.
Wiegmann, T. B., H. D. Day and R. V. Patak. 1982. Intestinal absorption
and excretion of radioactive vanadium f^^VO,) in rats and the effect of
Al(OH)3. J. Toxocol. Environ. Health 10:233-245.
Yamaguchi, M., H. Oishi, and Y. Suketa. 1989. Effect of vanadium on bone
metabolism in weanling rats: zinc prevents the toxic effects of vana-
dium. Exp. Med. 189:47-53.
Zaporowska, H., and W. Wasilewski. 1992. Combined effect of vanadium
and zinc on certain selected hematological indices in rats. Comp.
Biochem. Physiol. 103C: 143-147.
Zaporowska, H., and W. Wasilewski. 1991. Significance of reduced food
and water consumption in rats intoxicated with vanadium. Comp.
Biochem. Physiol. 99C:349-352.
Copyright © National Academy of Sciences. All rights reserved.
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31
Zinc
INTRODUCTION
Zinc (Zn) has an atomic number of 30 and appears in
group 12 of the Periodic Table. In biological systems, zinc is
virtually always in the divalent state. Zinc typically forms
complexes with a coordination number of 4 and with a tetra-
hedral disposition of ligands around the metal. Zinc is a
strong Lewis acid, meaning that it is an electron acceptor. It
does not exhibit redox chemistry. Zinc readily forms com-
plexes with amino acids, peptides, proteins, and nucleotides.
It has a particular affinity for thiol and hydroxy groups and
for amine electron donors.
Zinc is a bluish-grey element. A large proportion of all
zinc is used to galvanize metals such as iron to prevent cor-
rosion. The oxide (ZnO) is used in the manufacture of paints,
rubber products, cosmetics, pharmaceuticals, floor cover-
ings, plastics, printing inks, soap, textiles, electrical equip-
ment, and other products. It is also used in ointments. The
sulfide (ZnS) is used in making luminous dials, x-ray and
TV screens, paints, and fluorescent lights. In 2001, more
than 9 million tons of zinc were produced. Approximately
47 percent was used for galvanizing, 19 percent in brass and
bronze, 14 percent in zinc-based alloys, 9 percent in chemi-
cals, and the remaining 1 1 percent in other uses.
ESSENTIALITY
Zinc essentiality in plants was established in 1869
(Raulin, 1869), in experimental animals in 1934 (Todd et al.,
1934), in swine in 1955 (Tucker and Salmon, 1955), and in
humans in 1961 (Prasad et al., 1961). Additional zinc is
needed for growth and lactation. The efficiency of zinc ab-
sorption increases during pregnancy and lactation in rats
(Davies and Williams, 1977). Milk of most animals gener-
ally contains 3-5 mg/L of zinc (McDowell, 2003). The use
of a factorial approach to estimate the zinc requirements of
sheep and cattle during growth, pregnancy, and lactation is
discussed by Underwood and Suttle (1999). Milk zinc con-
centrations in humans are not influenced by maternal zinc
status or dietary zinc intakes (Krebs et al., 1985).
The biochemical basis for essentiality is traced to the dis-
covery of zinc as a requirement for activity of carbonic an-
hydrase in 1940 (Kielin and Mann, 1940) and zinc finger
protein domains in 1985 (Vallee et al., 1991). Since discov-
ery of zinc deficiency in humans, interest in the biochemical
and clinical aspects of zinc nutrition has increased exponen-
tially. Approximately 300 enzymes are associated with zinc
(Cousins and King, 2004). Because of its stability and coor-
dination flexibility, zinc is able to carry out many diverse
biological functions in protein, nucleic acid, carbohydrate,
and lipid metabolism (Vallee and Falchuk, 1993). Zinc is
required for DNA replication and transcription and is a co-
factor for many zinc-dependent gene regulatory proteins.
Zinc deficiency arrests growth and development and pro-
duces system dysfunction (Cousins and King, 2004). The
biological functions of zinc can be divided into three catego-
ries: catalytic, structural, and regulatory (Cousins, 1996).
The clinical signs of zinc deficiency include reduced
growth, feed intake, and feed efficiency; listlessness; reduced
testicular growth; parakeratotic lesions that are most severe
on the legs, neck, head, and around the nostrils; failure of
wounds to heal, and alopecia (Ott et al., 1965). Thymus atro-
phy and impaired immune function have also been observed
in zinc-deficient animals (Ferryman et al., 1989).
DIFFICULTIES IN ANALYSIS AND EVALUATION
Analytical procedures for zinc include atomic absorption
spectrophotometry and inductively-coupled plasma emission
spectrophotometry (Sunderman, 1973). Zinc reference stan-
dards are available from the National Institute of Standards
and Technology. Before analysis, any organic material asso-
ciated with the zinc must be destroyed. A microwave diges-
tion system using nitric acid in a closed system with high
temperature and pressure is the method of choice. Alterna-
tives include wet ashing with sulfuric acid or nitric acid or
413
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414
MINERAL TOLERANCE OF ANIMALS
dry ashing in a muffle furnace. Wfien ashing temperatures
exceed 500°C, losses occur via volatilization. Extreme care
must be taken to prevent contamination of samples; these
measures include the use of ultra-pure reagents, deionized
water, acid-washed glassware, and zinc-free laboratory sup-
plies. Blanks should be included in all analyses.
Of the zinc radioisotopes, only *^Zn (half-life, 245 days)
has been widely used in research. Stable isotopes of zinc and
corresponding natural abundances are ^'*Zn, 49 percent; ^^Zn,
29 percent; '^''Zn, 4 percent; ^^Zn, 19 percent; and ™Zn, 1
percent. These have been effectively used in human studies
of zinc metabolism (Turnlund and Keyes, 1990).
REGULATION AND METABOLISM
Absorption
Zinc is absorbed all along the intestinal tract, but the high-
est rates of absorption occur in the jejunum of humans and
nonruminant animals. In ruminants, there is also absorption
from the rumen (Georgievskii et al., 1979). Zinc uptake by
the small intestine occurs via two processes: (1) a
nonmediated (nonsaturable) process that is not affected by
dietary zinc intake and (2) a mediated (saturable) process
that is stimulated by zinc depletion (Solomons and Cousins,
1984; Cousins, 1996). The nonsaturable process does not
require energy and may reflect paracellular zinc uptake or
diffusion of zinc into the cell (Cousins, 1996). The net result
of these two processes is that fractional zinc absorption is
inversely related to dietary levels of zinc. Numerous dietary
factors affect the apparent absorption of zinc. These factors
include feed source, phytate, amino acids, and the presence
or absence of other divalent cations such as iron, calcium,
and copper (Hambidge et al., 1986; Lonnerdal, 1989; Abdel-
Mageed and Oehme, 1990a). In general, high intakes of iron,
calcium, and phytate reduce the availability of zinc for ab-
sorption, whereas certain amino acids (i.e., histidine, cys-
teine) enhance its absorption.
Thus, the efficiency of zinc absorption in animals can
vary widely from as little as 15 percent to more than 60 per-
cent (McDowell, 2003). Under usual conditions, about one-
third of the dietary zinc consumed by humans is absorbed
(King and Keen, 1999). Studies in experimental animals sug-
gest that zinc transporter proteins assist in regulating zinc
absorption and whole body homeostasis (Harris, 2002). Up-
take and retention of dietary zinc is greater in growing than
in mature organisms (Weigand and Kirchgessner, 1979).
Transport
Albumin appears to be the major portal carrier for newly
absorbed zinc (Cousins, 1989). Changes in the systemic level
of albumin may alter zinc absorption. Total plasma zinc is
bound primarily to albumin (70 percent) or a-2 macroglobu-
lin (20-30 percent). There is a large molar excess of albumin
compared with zinc, which assures that an adequate trans-
port system exists. Other plasma proteins that bind zinc in-
clude transferrin, histidine-rich glycoprotein, and perhaps
metallothionein. Plasma zinc concentrations respond mark-
edly to external stimuli, including fluctuations in zinc in-
take, fasting, and various acute stresses, such as infection
(King and Keen, 1999). Most reductions in plasma zinc lev-
els are believed to reflect increased hepatic zinc uptake, per-
haps resulting from hormonal control.
Excretion
The primary route of zinc excretion is in the feces (Miller,
1970). Fecal zinc represents unabsorbed dietary zinc as well
as zinc that is secreted into the gut from the body and is not
subsequently absorbed (i.e., endogenous fecal zinc). The
endogenous fecal losses are a mix of pancreatic and intesti-
nal secretions (King et al., 2000). Meals stimulate endog-
enous zinc secretion, and over half of zinc in the intestinal
lumen postprandially comes from endogenous secretions
(Matseshe et al., 1980). Both total and endogenous fecal ex-
cretion of a tracer dose of ^^Zn and of stable dietary zinc
were significantly reduced in calves and goats fed low zinc
diets (Hambidge et al., 1986).
Urinary and integumental zinc losses comprise less than
20 percent of the total losses under normal conditions
(Underwood and Suttle, 1999; King et al., 2000; McDowell,
2003). Urinary losses rise with trauma, muscle catabolism,
and the administration of chelating agents such as EDTA
(Hambidge et al., 1986). Urinary zinc levels do not respond
to changes in zinc intake unless the diet is virtually free of
zinc (King and Keen, 1999). Urinary excretion of zinc by
sheep and calves is generally <1 mg per day with little effect
due to zinc supply in the diet.
Regulation
The results of tracer studies and isolated cells suggest that the
zinc-binding protein, metallothionein (MT), is involved in the
regulation of zinc metabolism. It appears that MT is inducible by
dietary zinc via the metal response element (MRE) and MTF-1
mechanism of transcriptional regulation (Cousins, 1996). An in-
crease in cellular MT is associated with increased zinc binding
within the cells. Metallothionein may act as a Zn"*"^ buffer, con-
trolling the free Zn"*"' level or helping to control an intracellular
zinc pool that is responsive to both hormones and diet. Zinc trans-
porters that regulate influx or efflux further allow cells to adapt to
differences in zinc intake independent of MT. C3'tokines, prima-
rily interleukins 1 and 6, influence zinc metabolism (Cousins,
1996). Acute infection where proinflammatory cytokines are re-
leased leads to secretion of cj^okines that increases zinc uptake
into liver, bone marrow, and thymus and reduces the amount
going to bone, skin, and intestine.
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ZINC
415
Metabolic Interactions
Interactions with other divalent cations in the intestinal
lumen may also influence zinc bioavailability. High indi-
vidual doses of iron (25, 50, or 75 mg) in a water solution
inhibited the absorption of zinc from a 25-mg zinc dose
(Solomons and Jacob, 1981), but the interaction is less pro-
nounced when intakes are closer to "physiological levels"
(Lonnerdal, 2000). Nevertheless, there are reports of iron
supplementation reducing zinc absorption in individuals with
increased iron and zinc needs (e.g., pregnant and lactating
women, patients with ileostomies; O'Brien et al., 2000;
Chung et al., 2002; Troost et al., 2003). The interaction be-
tween calcium intake at high supplementation levels and zinc
absorption has not been resolved (Wood and Zheng, 1997).
Modest increases in copper intake do not interfere with zinc
absorption (August et al., 1989). High levels of tin and cad-
mium inhibit zinc absorption, but the extent to which lower,
physiological levels affect absorption in humans is unknown.
Although most of these interactions have been described in
studies of humans, it is assumed the same interactions occur
in animals.
Mechanisms of Toxicity
Excessive accumulation of zinc within the cells is thought
to disrupt the function of essential biological molecules, such
as protein, enzymes, and DNA. This leads to the clinical
signs of chronic toxicosis. Alterations in the protein can dis-
rupt function and lead to toxic consequences. Also, exces-
sive amounts of zinc in the gastrointestinal tract can lead to
reduced copper absorption from the diet, leading to a sys-
temic copper deficiency (Sandstead, 1995).
Acute excessive intakes of zinc can be a local irritant to
tissues and membranes causing gastrointestinal distress, with
signs including nausea, vomiting, abdominal cramps, and
diarrhea (Abdel-Mageed and Oehme, 1990a). High luminal
zinc concentrations may also damage the brush border mem-
brane of the small intestine and allow zinc to enter the cell
and bind nonspecifically to cellular proteins and other
ligands (ATSDR, 2003).
Zinc is relatively nontoxic to birds and mammals. Rats,
pigs, poultry, sheep, cattle, and humans exhibit considerable
tolerance to high intakes of zinc. Nevertheless, zinc toxico-
sis has occurred in a number of species. Exposure to exces-
sive zinc is primarily by ingestion. Other possible pathways
for zinc exposure are water and air. Sources of exposure in-
clude drinking water, feed, and polluted air. Initial signs of
zinc toxicosis in animals usually consist of reduced feed in-
take, growth rate, and other measures of performance or
signs of secondary deficiencies of other minerals, such as
copper. High levels of zinc also affect rumen metabolism,
probably via a toxic effect on ruminal microorganisms (Ott
etal., 1966b).
SOURCES AND BIOAVAILABILITY
Sources
Diet
Pasture herbage zinc content ranges from 17 to 60 mg/kg
dry weight with most values falling between 20 and 30 mg/kg.
Industrial pollution increases the zinc content of grass from
5- to 50-fold (Mills and Dalgarno, 1972). The zinc concen-
tration in plants usually falls with advancing maturity, and
leguminous plants invariably carry higher zinc levels than
grasses grown and sampled under the same conditions
(Hambidge et al., 1986). Heavy dressings with lime and to a
lesser extent with superphosphate can greatly reduce pasture
zinc levels. Cereal grains typically contain 20-30 mg/kg
zinc, whereas soybean, peanut, and linseed meal contain 50-
70 mg/kg. Fishmeal, whale meal, and meat meal may con-
tain 90-100 mg/kg zinc (Hambidge et al., 1986). When ani-
mal diets need to be supplemented to provide adequate zinc,
the usual form is either zinc sulfate or zinc oxide. Other
forms such as zinc acetate, zinc carbonate, zinc citrate, zinc
chloride, and zinc picolinate and also zinc-amino acid com-
plexes and zinc proteinates are occasionally used (Baker and
Ammerman, 1995). When the purpose is to provide pharma-
cological levels of zinc to enhance growth of chicks and
young pigs, zinc oxide is usually added.
Water
The standard for zinc level in drinking water is 5 mg/L
(NRC, 1978). EPA also recommends that drinking water
should contain no more than 5 mg/L of zinc because of taste
(ATSDR, 2003). This concentration is almost never reached
in surface water, municipal drinking water supplies, or in
drinking water collected from the home tap. Industrial pollu-
tion, such as that derived from dumping plating baths or
mining operations, can produce very high concentrations of
zinc. Streams tend to become purified by precipitation of zinc
with clay sediments or hydrous iron and manganese oxides.
A concentration of 25 mg/L zinc was recommended as a safe
upper limit in drinking water for livestock and poultry (NRC,
1978). Storage of food and water in galvanized containers
can contaminate the contents with large amounts of zinc,
particularly under acidic conditions. Other potential sources
of excess zinc include pesticides, fungicides, and industrial
pollution.
Bioavailability
The bioavailability of zinc is the fraction of zinc intake
that is retained and used for physiological functions. Zinc
absorption is determined by three factors: the animal's zinc
status, the total zinc content of the diet, and the availability
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476
MINERAL TOLERANCE OF ANIMALS
of soluble zinc from the diet's food components (Lonnerdal,
2000). If the animal's zinc status is discounted, zinc absorp-
tion is largely determined by its solubility in the intestinal
lumen, which in turn is affected by the chemical form of zinc
and the presence of specific inhibitors and enhancers of zinc
absorption. A comprehensive report on the bioavailability of
zinc for animals was published by Baker and Ammerman
(1995).
In general, zinc is absorbed more efficiently from aque-
ous sources in the absence of food and from animal prod-
ucts. Phytate (myoinositol hexaphosphate), which is present
in plant products, especially cereals and legumes, irrevers-
ibly binds zinc in the intestinal lumen and accounts for the
lower efficiency of absorption from plant foods. The nega-
tive effect on absorption is exerted by the inositol
hexaphosphates and pentaphosphates (Lonnerdal, 2000).
Phytates with less phosphate have little to no effect on zinc
absorption. Fiber is often implied as having a negative effect
on zinc absorption, but this is usually because most high
fiber foods are also high phytate foods (Lonnerdal, 2000).
The binding of zinc to low molecular weight ligands or
chelators that can be absorbed also has a positive effect on
zinc absorption because the solubility of zinc is increased.
Certain chelators (e.g., EDTA), amino acids (histidine or
methionine), and organic acids (citrate) have been used to
enhance zinc absorption. These have been shown to have
mixed benefit. Recently, plant breeding or genetic engineer-
ing strategies that either reduce the content of inhibitors (e.g.,
phytate) or increase the expression of compounds that en-
hance zinc absorption (e.g., amino acids) have been consid-
ered to improve the bioavailability of zinc from plant foods
(Lonnerdal, 2003).
In recent years, bioavailability has become more impor-
tant in livestock diets as producers attempt to reduce the
amount of zinc excreted in feces. In pigs, when retention
was used as an indication of absorption, zinc proteinate, zinc
polysaccharide, and zinc methionine were reported to be su-
perior to inorganic forms (oxide and sulfate) (Kessler et al.,
1996; Rupic et al., 1997). However, Wedekind et al. (1994)
reported that neither zinc methionine nor zinc lysine were as
bioavailable to pigs as zinc sulfate. Cheng et al. (1998) found
that zinc lysine did not improve zinc absorption compared
with zinc sulfate, but the addition of lysine, beyond that con-
tained in the zinc source, reduced hepatic zinc. Using mul-
tiple linear regression slope ratios of bone zinc in the chick,
Cao et al. (2000b) reported that the absorption of zinc-pro-
teinate, zinc-amino acid chelate, and zinc-polysaccharide
were 83-139 percent of zinc sulfate (set at 100 percent). With
this same technique, Sandoval et al. (1997a) found zinc ox-
ide was 74 percent as available as the sulfate form. Edwards
and Baker (1999) reported that various zinc oxide sources
fed to chicks were 93 to 39 percent absorbed relative to zinc
sulfate. Cao et al. (2000b) reported that slope ratios of liver,
kidney, and pancreas zinc concentrations and liver MT in
lambs were 130, 113, and 1 10 percent for a zinc proteinate.
a zinc amino acid chelate, and a zinc methionine, respec-
tively, compared with 100 percent for zinc sulfate.
TOXICOSIS
Exposure by Feed
Acute
Acute, high-dose oral exposure to zinc compounds gener-
ally results in gastrointestinal distress with clinical signs of
nausea, vomiting, abdominal cramps, and diarrhea; expo-
sure levels resulting in these effects in several different spe-
cies range from 2 to 8 mg Zn/kg/day (ATSDR, 2003). The
irritant effect of zinc sulfate led to its former use as an emetic.
Common sources of zinc contamination include galvanized
coating on iron and steel (cages and nails, metal nuts from
transport cages, and fencing), automotive parts, batteries,
fungicides, and topical medications. The less soluble salts of
zinc such as the oxide and stearate are commonly found in
protective ointments and cosmetics and do not usually cause
acute zinc toxicosis.
Acute zinc toxicosis has been reported in dogs and hu-
mans (Murphy, 1970; Hornfeldt and Koepke, 1984). It is
characterized by an intravascular hemolytic anemia, gas-
trointestinal upset from direct irritation, and, potentially,
multiorgan failure. There have been reports of dogs that have
ingested large amounts of zinc from pennies, metal nuts from
the dog's kennel, and other foreign metal objects (Hornfeldt
and Koepke, 1984; Caldwell, 1994; Gandini et al., 2002;
Mikszewski et al., 2003). Pennies minted after 1982 are made
predominantly of zinc (96-98 percent) with a copper (2.5
percent) coating. Clinical signs include anorexia, gastrointes-
tinal distress, hemolytic anemia, acute pancreatitis,
hepatomegaly, and renal disease (Gandini et al., 2002;
Mikszewski et al., 2003).
Acute zinc toxicosis also occurred in sheep given 3 g of
zinc in 20 ml of a solution of zinc sulfate using a drenching
gun in a study of the use of zinc to prevent lupinosis (Allen
et al., 1986). Two pellets, each containing 2.5 g of zinc,
were given immediately after the drench. Nineteen of the
230 sheep died within 3 days of the treatment. Necropsies
showed severe fibrosing pancreatitis, abdominal lesions,
and mild kidney changes. A reduction in feed intake was
noted in those animals that survived. Previous studies have
shown that sheep tolerate a single administration of 3 g of
zinc when given by ruminal intubation. But, when given
with a drenching gun, zinc is likely to cause intoxication
because the concentrated solution of zinc stimulates irrita-
tion and closure of the esophageal groove and severe le-
sions of the abomasum (Smith et al., 1979). The liver, kid-
ney, and bone seem to be able to accumulate zinc to
tolerable concentrations before other organs, such as the
pancreas, go into failure.
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ZINC
417
Chronic
Zinc toxicity is difficult to relate to the pfiysical and
chemical properties of this element because it is not believed
to be carcinogenic, mutagenic, or teratogenic, and it does not
have a classical genetically caused storage disease. As Vallee
and Falchuk (1993) stated, "Zinc is the only pre-, post-, and
transitional element that has proven to be essentially nontoxic."
A major effect of chronically excessive zinc intake is insuf-
ficient tissue copper caused by inducing metallothionein and
increasing copper-bound metallothionein in intestinal cells
and decreasing copper absorption. This causes a copper
deficiency anemia (ATSDR, 2003). Other effects of chronic
zinc toxicosis include reductions in immune function (de-
crease in lymphocyte stimulation by phytohemagglutinin)
and high-density lipoprotein (HDL) cholesterol (Cousins,
1996). A summary of experiments on chronic zinc toxicity is
presented in Table 31-1. High dietary zinc intake in chickens
produced a pause in egg production and molting via precipi-
tous decreases in food intake (McCormick and Cunningham,
1984). Feeding zinc to chickens at 500 mg/kg diet produced
dysfunction of pancreatic acinar cells and exocrine status
(Lu et al., 1990). It is unclear why the pancreas seems to be
so sensitive to chronically high intakes of zinc, but studies
suggest that pancreatic accumulation is related to the
metallothionein content of that tissue (Oh et al., 1979).
A natural occurrence of zinc toxicosis in male Holstein
veal calves provides useful information on the metabolic
consequences of chronic zinc toxicosis in growing ruminants
(Graham et al., 1987). Due to an error in manufacturing, an
additional amount of zinc sulfate was added to the milk re-
placer. The mean concentration of milk replacer totaled
about 700 mg/kg rather than 150 mg/kg; total zinc intake
averaged 1 .5 to 2 g per day. The high-zinc milk replacer was
fed for 35 days. Clinical signs appeared 23 days after feed-
ing the high-zinc milk replacer. Of the 85 calves examined,
75 percent had pneumonia, 73 percent had ocular signs,
54 percent had diarrhea, 40 percent were anorectic, 1 8 per-
cent were bloated, 9 percent had cardiac arrhythmias, 3.5
percent had convulsions, and 3.5 percent were polydipsic/
polyphagic. Nineteen percent of the calves died. Necropsy
data showed that tissue manganese, copper, and iron levels
were normal (Graham et al., 1988). However, infarcts in
liver, kidney, and heart tissue were observed. Marked atro-
phy and necrosis of pancreatic acinar tissue were observed.
Calves with a cumulative intake of more than 45 g of zinc for
35 days were 60 times more likely to die than calves exposed
to less than 45 g. These data suggest that the zinc intake of
preruminants should be less than 500 mg/kg diet. A subse-
quent study showed that only 700 or 1,000 mg/kg of dietary
zinc fed to preruminant calves altered weight gain, food in-
take, and feed efficiency (Jenkins and Hidiroglou, 1991).
The effect of chronically high intakes of zinc on copper
metabolism has been studied extensively in chicks, ruminants,
and experimental animals. Rama and Planas (1981) fed 80 or
5,000 mg/kg zinc with adequate copper and iron to one-day-
old chicks. The concentrations of iron and copper were
decreased in the plasma and liver. An intramuscular injection
of iron corrected these depressed concentrations, whereas an
oral iron supplement only partially returned hepatic iron to
normal. However, when copper was injected, all copper
parameters returned to normal including ceruloplasmin, but
iron was not corrected. The authors concluded that the inter-
ference of zinc was at the intestinal level. Administration of
diets containing 2,000 or 4,000 mg/kg zinc dramatically in-
creased liver, pancreas, and bone zinc levels while reducing
both gain and gain/feed markedly (Southern and Baker, 1983).
Excess dietary zinc also reduced liver copper deposition.
Sheep are a unique livestock species because they are
extremely sensitive to copper intake and have low hepatic
copper concentrations at birth compared with their concen-
trations at 30 and 60 days of age (Saylor and Leach, 1980).
This pattern is in contrast to other mammals where copper
concentrations are highest in the liver at birth. Saylor and
Leach (1980) found that when sheep were fed 543 mg/kg
zinc, ceruloplasmin activity, plasma copper concentration,
and hematocrits were reduced, but hepatic zinc and copper
were not changed. Dosing sheep with 1 g Zn/10 mL of solu-
tion directly into the rumen three times per week for 2-14
weeks induced renal lesions and elevated plasma creatinine
concentrations (Allen and Masters, 1985). Excess dietary
zinc, 750 mg/kg diet, induced severe copper deficiency in
pregnant ewes and caused a high incidence of abortions and
stillbirths (Campbell and Mills, 1979). Supplemental copper
failed to prevent the adverse effects of high zinc on weight
gain, feed consumption, efficiency of feed use, and lamb
viability. The authors speculated that a depressed feed in-
take of the ewes given the high-zinc diets caused the high
mortality rates of the lambs.
L' Abbe and Fischer (1984) reported that 120-240 mg/kg
zinc decreased hepatic superoxide dismutase and cardiac
cytochrome c oxidase activities in the rat, suggesting that
copper deficiency could result from zinc concentrations that
were only four times that recommended.
Hill et al. (1983) reported that when sows were fed 5,000
mg/kg zinc for two parities, copper was reduced and iron
was increased in the livers of their offspring at birth. How-
ever, the same group (Carlson et al., 1999) showed that when
newly weaned pigs were fed 3,000 mg/kg zinc for 4 weeks,
copper and iron in the liver were not altered compared with
pigs fed 150 mg/kg zinc. If the pigs were weaned at 1 1 days
of age, copper concentration in the kidney increased; if pigs
were weaned at 24 days of age copper concentration was not
changed. These data suggest that the severity of zinc excess
can be reduced by dietary provision of adequate iron. Barone
et al. (1998) found that fetal rats from dams fed 1,000 mg/kg
zinc had higher hepatic zinc and copper and higher plasma
iron than fetuses from dams fed 32 mg/kg zinc. However,
plasma copper and hepatic iron were not different.
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418
MINERAL TOLERANCE OF ANIMALS
An interaction between zinc and copper has also been
observed in humans. Administration of zinc as a therapeutic
agent to sicJcle cell anemia patients caused hypocupremia
(Prasad et al., 1978) that could be reversed by copper supple-
mentation. Similarly, self-supplementation with zinc for
"prostate trouble" resulted in sideroblastic anemia that was
reversed in 80 days when supplements were discontinued
(Patterson et al., 1985).
The mechanism underlying the interaction between zinc
and copper probably involves metallothionein. Both zinc and
cadmium induce MT (Tacnet et al., 1991). Using gel filtra-
tion analysis, Evans et al. (1970) reported that both cadmium
and zinc displaced copper from sulfhydryl binding sites on
MT, and, therefore, antagonized copper metabolism.
Exposure by Water
The mean concentrations of zinc in ambient water and
drinking water range from 0.02 to 0.05 mg/L and from 0.01
to 0.1 mg/L, respectively. The concentration of zinc in
drinking water can often be higher than the concentration
in the raw water from which the drinking water was ob-
tained because zinc may leach from transmission and dis-
tribution pipes. The concentration of zinc in standing water
from galvanized household water pipes was 1.3 mg/L
(ATSDR, 2003).
The bioavailability of zinc given in water is very high.
Consequently, zinc has been added to the drinking water
of ruminants to improve their zinc intake (Smith, 1980).
The addition of 0.25, 0.5, and 1.0 g Zn/L reduced water
consumption by 8, 35, and 54 percent compared to con-
trols over a 9-week period. The effect was greatest in the
early weeks of the experiment. Moderate pancreatic
damage was recorded in the animals in the high zinc
treatment group. It appeared that the unpalatable nature
of high aqueous zinc solutions was insufficient to pre-
vent toxicosis.
Factors Influencing Toxicity
The types and severity of adverse effects are related to
zinc exposure level and duration; animal age, sex, species,
and nutritional status; and composition of the diet. In gen-
eral, young animals and reproducing females are more vul-
nerable than adult, nonreproducing animals. Young animals
may be more vulnerable than older animals because they
tend to have a higher efficiency of zinc absorption. Exposure
to high levels of zinc in the diet prior to and/or during gesta-
tion has been associated with increased fetal resorptions, re-
duced fetal weights, altered tissue concentrations of fetal iron
and copper, and reduced growth in the offspring (ATSDR,
2003). Administration of 200 mg Zn/kg/day to dams
throughout gestation reduced growth and tissue levels of iron
and copper in fetal rats (ATSDR, 2003), but no changes were
seen when the diet provided 100 mg Zn/kg/day, suggesting
that the placenta was able to act as an effective barrier to
zinc at the lower dietary level.
Ruminants seem to be more susceptible to zinc toxicity
compared to rats, pigs, and poultry (Abdel-Mageed and
Oehme, 1990a). This may be due to the adverse effects of
the high zinc intake on ruminal microorganisms. At high
levels of zinc intake in lambs there was a reduction in the
volatile fatty acid concentration and acetic acid to propionic
acid ratio in the rumen (Ott et al., 1966a). Cellulose diges-
tion by ruminal bacteria in vitro was reduced by zinc con-
centrations in the medium of 10-20 pg/mL (Martinez and
Church, 1970).
The chemical form of administered zinc influences its
toxic effects. Sheep given a single intraruminal dose (120,
240, or 480 mg Zn/kg BW) or a thrice-weekly dose of 240
mg Zn/kg BW for 4 weeks showed a divergent response to
the chemical form of zinc administered (Smith and Embling,
1984). Sheep receiving the EDTA-zinc had an increase in
urinary zinc but only a transient elevation in plasma zinc,
whereas zinc sulfate caused a marked, sustained increase in
plasma zinc. The effect of supplemental zinc on mortality
varies with the form of zinc given. Six of the seven animals
receiving multiple doses of zinc sulfate died, whereas none
of the animals receiving zinc oxide or zinc EDTA died.
Major pancreatic injury occurred in sheep dosed with sulfate
or oxide, but only mild changes were observed in sheep
dosed with zinc EDTA. Diarrhea was mild and transitory in
the EDTA-dosed sheep, but more severe and persistent in
those dosed with sulfate. These divergent effects of the
chemical forms on zinc toxicity presumably are related to
zinc bioavailability from the different forms. Zinc sulfate is
considered to be highly available and readily absorbed. Zinc
oxide is less soluble and available for absorption. The EDTA
probably acts as a chelator and facilitates the excretion of
excessive zinc levels in tissues. Diethylenetriaminepentaacetic
acid (DTP A) and cyclohexanediaminetetraacetic acid (CDTA)
are also effective against zinc intoxication (Abdel-Mageed
and Oehme, 1990b).
The presence or absence of other cations in the diet can
also influence zinc toxicity. The interaction between zinc
and copper is described earlier in this chapter. Elevation of
dietary calcium from 0.7 to 1.1 percent was effective in pro-
tecting against the toxic effects of 4,000 mg Zn/kg diet in
young pigs (Abdel-Mageed and Oehme, 1990b).
TISSUE LEVELS
The zinc content of the bodies of adult animals (milli-
grams per kilogram of crude defatted tissue) ranges from 25
for swine to 50 for rabbits (Georgievskii et al., 1979). In
newborn animals, the zinc contents are somewhat lower:
from 10 for swine to 30 for cattle (mg per kg of crude defatted
tissue). Tissue distribution of zinc, however, varies consid-
erably, with some tissues (e.g., the prostate) having a very
high concentration. Approximately 85 percent of the total
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ZINC
419
body zinc is in skeletal muscle and bone. About 95 percent
of body zinc is intracellular, with 40 percent of the cellular
zinc found in the nucleus. A variable amount of cytosolic
zinc may reside in vesicles and may serve as a cellular zinc
reserve. The amount of "free" Zn-"^ in cells appears to be
very low (O'Halloran, 1993; Outten and O'Halloran, 2001).
Zinc contents of various tissues, averaged from several
different species fed diets without excess zinc, are as follows
(Georgievskii et al., 1979): blood (mg/L) 0.6-5; liver (mg/kg
fresh) 40-65; hide (mg/kg fresh) 3-6; and skeletal muscle
(mg/kg fresh) 5-9.
Zinc concentrations of selected fluids and tissues are pre-
sented in Table 31-2. These data indicate that excess intakes
cause zinc to be deposited in the liver, pancreas, kidney, and
bone. There is little or no accumulation in milk from dairy
cows and skeletal muscle of various species (Table 31-2) or
spleen of sheep (Rosa et al., 1986; Henry et al., 1997).
MAXIMUM TOLERABLE LEVELS
A summary of data on the maximum tolerable level of
zinc intake for animals published since 1980 is given in Table
31-1. Cat diets providing up to 230 mg Zn/kg BW/day as
zinc oxide for several months did not produce any adverse
effects (Drinker et al., 1927). When 600 mg Zn/kg of diet
was fed to adult cats for six weeks, plasma zinc concentra-
tion rose to 120 |Jg/dL compared to 90 |Jg/dL in cats fed 100
mg Zn/kg (Sterman et al., 1986). No clinical abnormalities
were reported, suggesting that the safe upper limit of dietary
zinc for adult cats is 600 mg/kg, at least for short periods of
time. Dogs fed diets that provided up to 80 mg Zn/kg BW/
day in the form of zinc oxide for several months suffered no
ill effects (Drinker et al., 1927).
Based on data published before 1980, the maximum tol-
erable level of zinc for poultry was set at 1,000 mg/kg diet
(NRC, 1980). Although earlier studies indicated that this
level of zinc was tolerated without decreased growth or feed
efficiency in diets adequate in all nutrients, recent studies
indicate that this level can result in negative effects. Lesions
in the pancreas and gizzard of chicks fed 1,000 mg/kg were
reported by Dewar et al. (1983). When diets were marginally
deficient in iron, 1,000 mg/kg also resulted in depressed
growth (Blalock and Hill, 1988). Mild histological changes
in the thyroid were observed in chicks fed 200 mg Zn/kg
diet, and this level decreases plasma levels of thyroxin in
laying hens (Kaya et al., 2001; 2002); however, functional
or pathological consequences of these changes have not been
demonstrated. Zinc caused decreased growth and signs of
pancreatic pathology when supplemented at 500 mg/kg to
purified diets (Lu and Combs, 1988; Lu et al., 1990). More
recently, several studies (Sandoval et al., 1997a, 1998, 1999;
Cao, 2000b) have reported reductions in feed intake and
weight gain when zinc exceeded 500 mg/kg diet, especially
when the source was zinc sulfate. Taken together, evidence
supports lowering the maximum tolerable level for poultry
to 500 mg/kg diet.
The maximum tolerable level of zinc for swine is difficult
to establish. Several studies reviewed in the 1980 report
(NRC, 1980) demonstrated that pigs tolerated zinc at levels
of 1 ,000 mg/kg of diet for many weeks, but 2,000 mg/kg diet
resulted in signs of toxicosis. The current maximum allow-
able zinc content in pig diets in Europe is 250 mg/kg, but this
is based on environmental concerns. Recently, numerous
experiments have demonstrated that supplementing weaned
pig diets with 1,500-3,000 mg/kg zinc as zinc oxide stimu-
lates their growth (Hill et al., 2000; Mavromichalis et al.,
2000; Carlson et al., 2004; Davis et al., 2004). Most of these
experiments have been for only 3 or 4 weeks, but a few have
lasted 5 or 6 weeks. Furthermore, most studies have used
zinc oxide, which is less bioavailable to pigs than zinc sul-
fate (Wedekind et al., 1994). Because of this, the maximum
tolerable level is left unchanged as 1,000 mg/kg of diet. De-
spite their prohibition in the EU, growth promotion levels of
zinc are used for short periods in many other countries. Al-
though not considered in determining the maximum toler-
able level, the potential negative environmental impact of
excessive zinc intakes is an important consideration
(Jondreville et al., 2003).
The maximum tolerable concentration of zinc for cattle
was previously set at 500 mg/kg (NRC, 1980); recent re-
search supports this recommendation. Young calves fed milk
replacer tolerated 500 mg Zn/kg of diet for 5 weeks without
adverse effects; but 700 mg/kg of diet reduced gain, feed
intake, and feed efficiency (Jenkins and Hidiroglou, 1991).
In one experiment, dairy cattle were fed a diet with a zinc
content of 1,000 mg/kg for 16 weeks with no adverse effects.
For sheep, the previous maximum tolerable level was set
at 300 mg/kg of diet, and there is insufficient new evidence
to justify a change. In one experiment (Henry et al., 1997),
levels as high as 2,100 mg/kg were fed for as long as 30 days
without reducing feed intake, but tissues were not examined
for histological lesions.
Because there is little accumulation of zinc in skeletal
muscle or milk, excess intake of zinc by animals has little
consequence for human health. Very high intakes of zinc do
cause some increase in zinc content of kidney and liver
(Table 31-2) but not heart (Henry et al., 1997).
FUTURE RESEARCH NEEDS
Maximum tolerable levels for many species, including
horses, dogs, and cats, are not well established, and these
species merit further research. Pharmacological levels of zinc
intake have been shown to be effective in promoting growth
in livestock. Further studies are needed to determine the op-
timal levels, sources, and duration of feeding of pharmaco-
logical levels to achieve the optimum benefit and the least
environmental impact.
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420
MINERAL TOLERANCE OF ANIMALS
SUMMARY
Zinc is an essential nutrient for all animal species and is
required for a wide variety of metabolic functions. Different
compounds of zinc differ widely in bioavailability and prob-
ably in toxicity. Although animals are able to tolerate much
higher levels of zinc than of many other minerals, signs of
toxicosis generally develop when dietary concentrations ex-
ceed 1,000 mg/kg. In addition to reduced feed intake and
growth rate, signs of toxicosis often involve damage to the
pancreas. Swine are more tolerant than most other species of
high zinc levels. Indeed, levels as high as 3,000 mg/kg of
diet for periods of 3 or 4 weeks promote growth and feed
efficiency of young pigs.
REFERENCES
Abdel-Mageed, A. B., and F. W. Oehme. 1990a. A review of the biochemi-
cal roles, toxicity, and interactions of zinc, copper, and iron: I. Zinc.
Vet. Hum. Toxicol. 32:34-39.
Abdel-Mageed, A. B., andF. W. Oehme. 1990b. A review on biochemical
roles, toxicity, and interactions of zinc, copper, and iron: IV. Interac-
tions. Vet. Hum. Toxicol. 32:456^58.
Allen, J. G., and H. G. Masters. 1985. Renal lesions and tissue concentra-
tions of zinc, copper, iron, and manganese in experimentally zinc in-
toxicated sheep. Res. Vet. Sci. 39:249-251.
Allen, J. G., H. G. Masters, R. L. Peet, K. R. Mullins, R. D. Lewis, S. Z.
Skirrow, and J. Fry. 1983. Zinc toxicity in ruminants. J. Comp. Pathol.
93:363-377.
Allen, J. G., P. W. Morcombe, H. G. Masters, D. S. Petterson, and T. A.
Robertson. 1986. Acute zinc toxicity in sheep. Aust. Vet. J. 63:93-95.
ATSDR (Agency for Toxic Substances and Disease Registry). 2003. Zinc.
Online. Available at http://www.atsdr.cdc.gov/toxprofiles/tp60.html.
Accessed May 3. 2005.
August, D., M. Janghorbani, and V. R. Young. 1989. Determination of zinc
and copper absorption at three dietary Zn-Cu ratios by using stable iso-
tope methods in young adults and elderly subjects. Am. J. Clin. Nutr.
50:1457-1463.
Bafundo, K. W., D. H. Baker, and P. R. Fitzgerald. 1984. Lead toxicity in
the chick as affected by excess copper and zinc and by Eimeria
acervulina infection. Poult. Sci. 63:1594—1603.
Baker, D. H., and C. B. Ammerman. 1995. Zinc bioavailability. Pp. 367-
398 in Bioavailability of Nutrients for Animals: Amino Acids, Miner-
als, and Vitamins, C. B. Ammerman, D. H. Baker, and A. J. Lewis, eds.
San Diego: Academic Press.
Barone, A., O. Ebesh, R. G. Harper, and R. A. Wapnir. 1998. Placental
copper transport in rats: effects of elevated dietary zinc on fetal copper,
iron and metallothionein. J. Nutr. 128:1037-1041.
Blalock, T. L., and C. H. Hill. 1988. Studies on the role of iron in zinc
toxicity in chicks. Biol. Trace Elem. Res. 17:17-29.
Bradley, R. W., and J. B. Sprague. 1985. The influence of pH, water hard-
ness, and alkalinity on the acute lethality of zinc to rainbow trout (Salmo
gairdneri). Can. J. Fish. Aquat. Sci. 42:731-736.
Caldwell, D. E. 1994. Zinc toxicity in the dog. Canine Pract. 19(6):6-7.
Campbell, J. K., and C. F. Mills 1979. The toxicity of zinc to pregnant
sheep. Environ. Res. 201:1—13.
Cao, J., P. R. Henry, C. B. Ammerman, R. D. Miles, and R. C. Littell.
2000a. Relative bioavailability of basic zinc sulfate and basic zinc chlo-
ride for chicks. J. Appl. Poult. Res. 9:513-517.
Cao, J., P. R. Henry, R. Guo, R. A. Holwerda, J. P. Toth, R. C. Littell, R. D.
Miles, and C. B. Ammerman. 2000b. Chemical characteristics and rela-
tive bioavailability of supplemental organic zinc sources for poultry and
ruminants. J. Anim. Sci. 78:2039-2054.
Carlson. M. S., G. M. Hill, and J. E. Link. 1999. Early and traditionally
weaned nursery pigs benefit from phase-feeding pharmacological con-
centrations of zinc oxide: effect on metallothionine and mineral concen-
trations. J. Anim. Sci. 77:199-1207.
Carlson, M. S., C. A. Boren, C. Wu, C. E. Huntington, D. W. Bollinger, and T.
L. Veum. 2004. Evaluation of various inclusion rates of organic zinc either
as polysaccharide or proteinate complex on the growth performance,
plasma, and excretion of nursery pigs. J. Anim. Sci. 82:1359-1366.
Cheng, J., E. T. Kornegay, and T. Schell. 1998. Influence of dietary lysine
on the utilization of zinc from zinc sulfate and a zinc-lysine complex by
young pigs. J. Anim. Sci. 76:1064—1074.
Chung, C. S., D. A. Nagey, C. Veillon, K. Y. Patterson, R. T. Jackson, and
P. B. Moser- Veillon. 2002. A single 60-mg iron dose decreases zinc
absorption in lactating women. J. Nutr. 132:1903-1905.
Clearwater, S. J., A. M. Farag, and J. S. Meyer. 2002. Bioavailability and
toxicity of diet-borne copper and zinc to fish. Comp. Biochem. Physiol.
C. 132:269-313.
Cousins, R. J. 1989. Systemic transport of zinc. Pp. 79—93 in Zinc in Hu-
man Biology, C. F. Mills, ed. London: Springer- Verlag.
Cousins, R. J. 1996. Zinc. Pp. 293-306 in Present Knowledge in Nutrition,
E. E. Ziegler and L. J. Filer, Jr., eds. Washington, D.C.: ILSI Press.
Cousins, R. J., and J. C. King 2004. Zinc. In Modern Nutrition in Health and
Disease. M. E. Shils, A. C. Ross, and R. J. Cousins., eds. Philadelphia:
Lea and Febiger.
Davies, N. T., and R. B. Williams 1977. The effect of pregnancy and lacta-
tion on the absorption of zinc and lysine by the rat duodenum in situ. Br.
J. Nutr. 38:417-^23.
Davis, M. E., D. C. Brown, C. V. Maxwell, Z. B. Johnson, E. B. Kegley,
and R. A. Dvorak. 2004. Effect of phosphorylated mannans and phar-
macological additions of zinc oxide on growth and immunocompetence
of weanling pigs. J. Anim. Sci. 82:581—587.
Dean, C. E., B. M. Hargis, and P. M. Hargis. 1991. Effects of zinc toxicity
on thyroid function and histology in broiler chicks. Toxicol. Lett.
(Amst.) 57:309-318.
Dewar, W. A., P. A. Wight, R. A. Pearson, and M. J. Gentle. 1983. Toxic
effects of high concentrations of zinc oxide in the diet of the chick and
laying hen. Br. Poult. Sci. 24:397^04.
Donmez, H. H., M. A. Karsli, I. Meral, N. Donmez, and N. §im§ek. 2001.
Effects of increasing zinc supplementation in drinking water on growth
and thyroid gland function and histology in broiler chicks. Dtsch.
Tieraerztl. Wochenschr. 109:438-442.
Donmez, N., H. Htiseyin Donmez, E. Keskin, and I. felik. 2002. Effects of
zinc supplementation to ration on some hematological parameters in
broiler chicks. Biol. Trace Elem. Res. 87:125-131.
Drinker, K. R, P. K. Thompson, and M. Marsh. 1927. An investigation of
the effect of long-continued ingestion of zinc, in the form of zinc oxide,
by cats and dogs, together with observations upon the excretion and
storage of zinc. Am. J. Physiol. 80:31—64.
Edwards, H. M., and D. H. Baker. 1999. Bioavailability of zinc in several
sources of zinc oxide, zinc sulfate, and zinc metal. J. Anim. Sci.
77:2730-2735.
Ellis, T. M., H. G. Masters, and C. Mayberry. 1984. Examination of the
susceptibility of different breeds of sheep to zinc intoxication. Aust.
Vet. J. 61:296-298.
Evans, G. W., P. F. Majors, and W. E. Cornatzer. 1970. Mechanism for
cadmium and zinc antagonism of copper metabolism. Biochem.
Biophys. Res. Comm. 40:1142-1148.
Everall, N. C, N. A. A. Macfarlane, and R. W. Sedgwick. 1989. The inter-
actions of water hardness and pH with the acute toxicity of zinc to the
brown trout, Salmo trutta L. J. Fish Biol. 35:27—36.
Farmer, G. J., D. Ashfield, and H. S. Samant. 1979. Effects of zinc on
juvenile Atlantic salmon Salmo salar: acute toxicity, food intake,
growth, and bioaccumulation. Environ. Pollut. 19:103-117.
Gandini, G., G. Bettini, M. Pietra, L. Mandrioli, and E. Carpene. 2002.
Clinical and pathological findings of acute zinc intoxication in a puppy.
J. Small Anim. Pract. 43:539-542.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
ZINC
421
Georgievskii, V. I., B. N. Annenkov, and V. I. Samokhin. 1979. Mineral
Nutrition of Animals. London: Butterworths.
Graham, T. W., M. C. Thurmond, M. S. Clegg, C. L. Keen, C. A. Holmberg,
M. R. Slanker, and W. J. Goodger. 1987. An epidemiological study of
mortality in veal calves subsequent to an episode of zinc toxicosis on a
California veal calf operation using zinc sulphate-supplemented milk
replacer. J. Am. Vet. Med. Assoc. 190:1296-1301.
Graham, T. W., C. A. Holmberg, C. L. Keen, M. C. Thurmond, and M. S.
Clegg. 1988. A pathologic and toxicologic evaluation of veal calves fed
large amounts of zinc. Vet. Pathol. 25:484^91.
Hambidge, K. M., C. E. Casey, and N. F. Krebs. 1986. Zinc. Pp. 1-37 in
Trace Elements in Human and Animal Nutrition, W. Mertz, ed. Or-
lando, FL: Academic Press.
Harris, E. D. 2002. Cellular transporters for zinc. Nutr. Rev. 60:121-124.
Henry, P. R., R. C. Littell, and C. B. Ammerman. 1997. Effect of high
dietary zinc concentration and length of zinc feeding on feed intake and
tissue zinc concentration in sheep. Anim. Feed Sci. Technol. 66:237-
245.
Hill, G. M., E. R. Miller, and H. D. Stowe. 1983. Effect of dietary zinc
levels on health and productivity of gilts and sows through two parities.
J. Anim. Sci. 57:114-122.
Hill, G. M., G. L. Cromwell, T. D. Crenshaw, C. R. Dove, R. C. Ewan, D.
A. Knabe, A. J. Lewis, G. W. Libal, D. C. Mahan, G. C. Shurson, L. L.
Southern, and T. L. Veum. 2000. Growth promotion effects and plasma
changes from feeding high dietary concentrations of zinc and copper to
weanling pigs (regional study). J. Anim. Sci. 78:1010-1016.
Hornfeldt, C. S., and T. E. Koepke 1984. A case of suspected zinc toxicity
in a dog. Vet. Hum. Toxicol. 26:214.
Jenkins, K. J., and M. Hidiroglou. 1991. Tolerance of the preruminant calf
for excess manganese or zinc in milk replacer. J. Dairy Sci. 74:1047—
1053.
Jondreville, C. P. S. Revy, and J. Y. Dourmad. 2003. Dietary means to
better control the environmental impact of copper and zinc by pigs from
weaning to slaughter. Livest. Prod. Sci. 84:147-156.
Kargin, F., and H. Y. (Jogun. 1999. Metal interactions during accumulation
and elimination of zinc and cadmium in tissues of the freshwater fish
Tilapia nilotica. Bull. Environ. Contamin. Toxicol. 63:511-519.
Kaya, S., T. Kececi, and S. Haliloglu. 2001. Effects of zinc and vitamin a
supplements on plasma levels of thyroid hormones, cholesterol, glu-
cose, and egg yolk cholesterol of laying hens. Res. Vet. Sci. 71:135-
139.
Kaya, S., M. Ortatatli, and S. Haliloglu. 2002. Feeding diets supplemented
with zinc and vitamin A in laying hens: effects on histopathological
findings and tissue mineral contents. Res. Vet. Sci. 73:251-257.
Kessler, J., A. D. Faria, and M. lost. 1996. Organic zinc compounds in
piglet feeding. Agraforschung 3:547-550.
Kielin, D., and J. Mann 1940. Carbonic anhydrase: purification and nature
of the enzyme. Biochem. J. 34:1163-76.
King, J. C, and C. L. Keen. 1999. Zinc. Pp. 223-239 in Modern Nutrition in
Health and Disease, M. E. Shils, J. A. Olson, M. Shike, and A. C. Ross,
eds. Philadelphia: Lea and Febiger.
King, J. C, D. M. Shames, and L. R. Woodhouse. 2000. Zinc homeostasis
in humans. J. Nutr. 130:1360S-1366S.
Krebs, N. F., K. M. Hambidge, M. A. Jacobs, and J. O. Rasbach. 1985. The
effects of a dietary zinc supplement during lactation on longitudinal
changes in maternal zinc status and milk zinc concentrations. Am. J.
Clin. Nutr. 41:560-570.
L'Abbe, M. R., and P. W. Fischer. 1984. The effects of high dietary zinc
and copper deficiency on the activity of copper-requiring
metalloenzymes in the growing rat. J. Nutr. 114:813-822.
Lonnerdal, B. 1989. Intestinal absorption of zinc. Pp. 33-55 in Zinc in Hu-
man Biology, C. F. Mills, ed. London: Springer- Verlag.
Lonnerdal, B. 2000. Dietary factors influencing zinc absoiption. J. Nutr.
130:1378S-1383S.
Lonnerdal, B. 2003. Genetically modified plants for improved trace ele-
ment nutrition. J. Nutr. 133(5 Suppl 1):1490S-1493S.
Lovegrove, S. M., and B. Eddy. 1982. Uptake and accumulation of zinc in
juvenile rainbow trout, Salmo gairdneri. Environ. Biol. Fishes 7:285-
289.
Lu, J., and G. F. Combs, Jr. 1988. Effect of excess dietary zinc on pancre-
atic exocrine function in the chick. J. Nutr. 118:681— 689.
Lu, J. X., G. F. Combs, Jr., and J. C. Fleet. 1990. Time-course studies of
pancreatic exocrine damage induced by excess dietary zinc in the chick.
J. Nutr. 120:389-397.
Martinez, A., and D. C. Church. 1970. Effect of various mineral elements
on in vitro rumen cellulose digestion. J. Anim. Sci. 31:982-990.
Matseshe, J. W., S. F. Phillips, J. R. Malagelada, and J. T. McCall. 1980.
Recovery of dietary iron and zinc from the proximal intestine of healthy
man: studies of different meals and supplements. Am. J. Clin. Nutr.
33:1946-1953.
Mavromichalis, 1., C. M. Peter, T. M. Parr, D. Ganessunker, and D. H.
Baker. 2000. Growth-promoting efficacy in young pigs of two sources
of zinc oxide having either a high or a low bioavailability of zinc. J.
Anim. Sci. 78:2896-2902.
McCormick, C. C, and D. L. Cunningham 1984. High dietary zinc and
fasting as methods of forced resting: a performance comparison. Poult.
Sci. 63:1201-1206.
McDowell, L. R. 2003. Minerals in Animal and Human Nutrition.
Amsterdam: Elsevier.
Mikszewski, J. S., H. M. Saunders, and R. S. Hess. 2003. Zinc-associated
acute pancreatitis in a dog. J. Small Anim. Pract. 44:177—180.
Miller, W. J. 1970. Zinc nutrition of cattle: a review. J. Dairy Sci. 53:1 123-
1135.
Miller, W. J., H. E. Amos, R. P. Gentry, D. M. Blackmon, R. M. Durrance,
C. T. Crowe, A. S. Fielding, and M. W. Neathery. 1989. Long-term
feeding of high zinc sulfate diets to lactating and gestating dairy cows.
J. Dairy Sci. 72:1499-1508.
Mills, C. F.. and A. C. Dalgarno 1972. Copper and zinc status of ewes and
lambs receiving increased dietary concentrations of cadmium. Nature
239:171.
Murphy, J. L. 1970. Intoxication following ingestion of elemental zinc.
JAMA 12:2119-2120.
NRC (National Research Council). 1978. Metabolic and Biologic Effects of
Environmental Pollutants. Zinc. Washington, D.C.: National Academy
Press.
NRC (National Research Council). 1980. Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
O'Brien, K. O., N. Zavaleta, L. E. Caulfield, J. P. Wen, and S. A. Abrams.
2000. Prenatal iron supplements impair zinc absorption in pregnant Pe-
ruvian women. J. Nutr. 130:2251-2255.
Oh, S. H., H. Nakaue, J. T. Deagen, P. D. Whanger, and G. H. Ai'scott.
1979. Accumulation and depletion of zinc in chick tissue
metallothioneins. J. Nutr. 109:1720-1729.
O'Halloran, T. V. 1993. Transition metals in control of gene expression.
Science 46:715-725.
Ott, E. A., W. H. Smith, M. Stob, H. E. Parker, and W. M. Beeson. 1965.
Zinc deficiency syndrome in the young calf. J. Anim. Sci. 24:735-741.
Ott, E. A., W. H. Smith, R. B. Harrington, M. Stob, H. E. Parker, and W. M.
Beeson. 1966a. Zinc toxicity in ruminants. 111. Physiological changes in
tissues and alterations in rumen metabolism in lambs. J. Anim. Sci.
25:424-431.
Ott, E. A., W. H. Smith, R. B. Harrington, H. E. Parker, and W. M. Beeson.
1966b. Zinc toxicity in ruminants. IV. Physiological changes in tissues
of beef cattle. J. Anim. Sci. 25:431^38.
Outten, C. E., and T. V. O'Halloran. 2001. Femtomolar sensitivity of
metalloregulatory proteins controlling zinc homeostasis. Science
292(5526) :2488-2492.
Palafox, A. L., and E. Ho-A. 1980. Effect of zinc toxicity in laying White
Leghorn pullets and hens. Poult. Sci. 59:2024-2028.
Patterson, W. P., M. Winkelmann, and M. C. Perry. 1985. Zinc-induced
copper deficiency: megamineral sideroblastic anemia. Ann. Intern. Med.
103:385-386.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
422
MINERAL TOLERANCE OF ANIMALS
Ferryman, L. E., D. R. Leach. W. C. Davis, W. D. Micitelson, S. R. Heller,
H. D. Ochs, J. A. Ellis, and G. Brummerstedt. 1989. Lymphocyte alter-
ations in zinc-deficient calves with lethal trait A46. Vet. Immunol.
Immunopathol. 21:239-248.
Prasad, A. S., J. A. Halsted, and M. Nadimi. 1961. Syndrome of iron defi-
ciency anaemia hepatosplenomegaly, hypogonadism, dwarfism, and
geophagia. Am. J. Med. 31:532-546.
Prasad, A. S., G. J. Brewer, E. B. Schoomaker, and P. Rabbani. 1978. Hy-
pocupremia induced by zinc therapy in adults. JAMA 240:2166-2168.
Rama, R., and J. Planas. 1981 . Effects of dietary zinc on iron metabolism in
chickens. Biol. Trace Elem. Res. 3:287-299.
Raulin, J. 1869. Etudes cliniques sur la vegetation. Ann. Sci. Nat. Bot. Biol.
Veg. 11:93.
Rosa, 1. v., C. B. Ammerman, and P. R. Henry. 1986. Interrelationship of
dietary copper, zinc, and iron on performance and tissue mineral con-
centration in sheep. Nutr. Rep. Int. 34:893-902.
Rupic, v., L. Ivandija, S. Luterotti, andM. Dominis-Kramaric. 1997. Influ-
ence of inorganic and organic zinc on its concentration in blood serum,
bones, and hair and on catalytical activity of some serum enzymes in
pigs. Acta Vet. Brno 66:75-85.
Sandoval, M., P. R. Henry, C. B. Ammerman, R. D. Miles, and R. C. Littell,
1997a. Relative bioavailability of supplemental zinc sources for chicks,
J. Anim. Sci. 75:3195-3205.
Sandoval, M., P. R. Henry, R. C. Littell, R. J. Cousins, and C. B
Ammerman. 1997b. Estimation of the relative bioavailability of zinc
from inorganic zinc sources for sheep. Anim. Feed Sci. Techno!
66:223-235.
Sandoval, M., P. R. Henry, X. G. Luo, R. C. Littell, R. D. Miles, and C. B,
Ammerman. 1998. Performance and tissue zinc and metallothionein
accumulation in chicks fed a high dietary level of zinc. Poult. Sci
77:1354-1363.
Sandoval, M., P. R. Henry, R. C. Littell, R. D. Miles, G. D. Butcher, and C,
B. Ammerman. 1999. Effect of dietary zinc source and method of oral
administration on performance and tissue trace mineral concentration of
broiler chicks. J. Anim. Sci. 77:1788-1799.
Sandstead, H. H. 1995. Requirements and toxicity of essential trace ele-
ments, illustrated by zinc and copper. Am. J. Clin. Nutr. 61(3
Suppl):621S-624S.
Saylor, W. W., and R. M. Leach. 1980. Intracellular distribution of copper
and zinc in sheep: effect of age and dietary levels of the metals. J. Nutr.
110:448^59.
Smith, B. L. 1980. Effect of high concentrations of zinc sulfate in the drink-
ing water of grazing yearling dairy cattle. N. Z. J. Agric. Res. 23:175—
178.
Smith, B. L., and P. P. Embling 1984. The influence of chemical form of
zinc on the effects of toxic intraruminal doses of zinc to sheep. J. Appl.
Toxicol. 4:92-96.
Smith, B. L., G. W. Reynolds, and P. P. Embling. 1979. Effect of method of
oral administration of zinc sulfate on acute zinc toxicity in the sheep. N.
Z.J. Exp. Agric. 7:107-110.
Solomons, N. W., and R. A. Jacob 1981. Studies on the bioavailability of
zinc in humans: effects of heme and nonheme iron on the absorption of
zinc. Am. J. Clin. Nutr. 34:475-482.
Solomons, N. W., and R. J. Cousins. 1984. Zinc. Pp. 125-197 in Absorption
and Malabsorption of Mineral Nutrients, N. W. Solomons and I. H.
Rosenberg, eds. New York: Alan R. Liss.
Southern, L. L., and D. H. Baker. 1983. Zinc toxicity, zinc deficiency, and
zinc-copper interrelationship in Eimeria acervulina-infected chicks. J.
Nutr. 113:688-696.
Sterman, M., M. Shouse, M. Fairchild, and O. Belsito. 1986. Kindled sei-
zure induction alters and is altered by zinc absorption. Brain Res.
383:382-386.
Sunderman, F. W., Jr. 1973. Atomic absorption spectrometry of trace metals
in clinical pathology. Hum. Pathol. 4:549-582.
Tacnet, F., P. Ripoche, M. Roux, and J. M. Neumann. 1991. 'ip-NMR
study of pig intestinal brush-border membrane structure: effect of zinc
and cadmium ions. Eur. Biophys. J. 19:317:322.
Todd, W. R., C. A. Elvehjem, and E. B. Hart. 1934. Zinc in the nutrition of
the rat. Am. J. Physiol. 107:146-156.
Troost, F. J., R. J. M. Brummer, J. R. Dainty, J. A. Hoogewerff, V. J. Bull,
and W. H. M. Saris. 2003. Iron supplements inhibit zinc but not copper
absorption in vivo in ileostomy subjects. Am. J. Cin. Nutr. 78:1018-
1023.
Tucker, H., and W. Salmon 1955. Parakeratosis or zinc deficiency in the
pig. Proc. Soc. Exp. Biol. Med. 88:613-616.
Turnlund, J. R., and W. R. Keyes 1990. Automated analysis of stable iso-
topes of zinc, copper, iron, calcium, and magnesium by thermal ioniza-
tion mass spectrometry using double isotope dilution for tracer studies
in humans. J. Micronutr. Anal. 7:1 17-145.
Underwood, E. J., and N. F. Suttle. 1999. The Mineral Nutrition of Live-
stock, 3rd ed. New York: CABI Publishing.
Vallee, B. L., and K. H. Falchuk 1993. The biochemical basis of zinc physi-
ology. Physiol. Rev. 73:79-118.
Vallee, B. L., J. E. Coleman, and D. S. Auld. 1991. Zinc fingers, zinc clus-
ters, and zinc twists in DNA-binding protein domains. Proc. Nat. Acad.
Sci. USA 88:999-1003.
Wedekind, K. J., A. J. Lewis, M. A. Giesemann, and P. S. Miller. 1994.
Bioavailability of zinc from inorganic and organic sources for pigs fed
corn-soybean meal diets. J. Anim. Sci. 72:2681-2689.
Weigand, E., and M. Kirchgessner 1979. Change in apparent and true ab-
sorption and retention of dietary zinc with age in rats. Biol. Trace Elem.
Res. 1:347-358.
Williams, S. N., R. D. Miles, M. D. Quart, and D. R. Campbell. 1989.
Short-term high-level zinc feeding and tissue zinc concentration in ma-
ture laying hens. Poult. Sci 68:539-545.
Wood, R. J., and J. J. Zheng 1997. High dietary calcium intakes reduce zinc
absorption and balance in humans. Am. J. Clin. Nutr. 65:1803-1809.
Wright, D. E., N. R. Towers, and D. P. Sinclair. 1978. Intake of zinc sul-
phate in drinking water by grazing beef cattle. N. Z. J. Agric. Res.
21:215-221.
Copyright © National Academy of Sciences. All rights reserved.
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32
Other Minerals
INTRODUCTION
There are several elements that are unlikely to be of toxi-
cological concern under natural conditions to domestic ani-
mals, and therefore are not reviewed in separate chapters in
this document. However, the tolerable levels of these ele-
ments may be of interest because of possible exposure
through supplements promoted in response to findings sug-
gesting essentiality (rubidium, tungsten), growth stimulation
(rare earths, titanium), or some other beneficial effect
(lithium, germanium, strontium); pharmaceutical formula-
tions (antimony, silver); or anthropogenic sources (uranium).
Thus, succinct information related to toxicity about these
elements is presented in this chapter. To keep this chapter to
a reasonable length, some sections included in other chap-
ters (e.g., methods of analysis) have been omitted from this
chapter.
ANTIMONY
Antimony (Sb) is a lustrous, silver-white metal with a
bluish tinge that is commercially derived mostly from stib-
nite ore (Sb^Sj). Abundant deposits are found in China,
Mexico, Bolivia, South Africa, and Tajikistan. The estimates
of the abundance of antimony in the Earth's crust range from
0.2 to 0.5 mg/kg (USGS, 2004). The major use of antimony
metal is as a hardener of lead in storage batteries; other alloy
uses of the metal include solder, sheet and pipe metal, bear-
ings, castings, and pewter. Antimony oxide is primarily used
in flame-retardant formulations for children's clothing, toys,
aircraft, and automobile seat covers; other uses for the oxide
include paints, ceramics, and fireworks, and as enamels for
plastics, metal, and glass.
Biological interest in antimony developed when the triva-
lent antimony compound potassium antimonyl tartrate
(KSbC4H407 • VjHjO) was found to be an effective treatment
for schistosomiasis, or bilharziasis, and subsequently for
leishmaniasis. Treatment of schistosomiasis requires the in-
travenous administration of potassium antimonyl tartrate at
a near lethal dose of 36 mg/kg (Dieter et al., 1991). Cur-
rently, treatment of leishmaniasis requires parenteral admin-
istration of pentavalent antimony compounds (Croft and
Yardley, 2002). Other organic drugs that can be taken orally
have been or are being developed to replace antimony com-
pounds that need invasive methods of administration. Anti-
mony taken orally has no known essential or beneficial meta-
bolic function in living organisms.
Sources and Metabolism
Potentially toxic doses of antimony may happen as a con-
sequence of industrial processing and use of antimony,
preparation or storage of food in containers improperly
glazed with enamels containing antimony, and accidental or
intentional ingestion of excessive amounts of antimony com-
pounds. Enamel glazes utilizing antimony trioxide as an
opacifier, particularly if low in silica, are readily attacked by
food acids. Monier-Williams (1925, 1934) reported that a 1
percent citric acid solution dissolved 10 mg Sb/L from an
enameled container. Reported reliable values for antimony
in foods and feedstuffs are few. Most human foods contain
no more than a few |Jg Sb/kg (Nielsen, 1986). Nuts are rela-
tively high in antimony (50-300 |Jg/kg DW) (Purr et al.,
1979). Clemente et al. (1978) reported that the daily dietary
intake of Italians was 1.5 [Jg of antimony. Becker etal. (1975)
found that the antimony content of swine feeds, piglet starter
rations, fishmeals, and various mixed feeds was generally
between 20 and 60 |Jg/kg. An occasional feed sample con-
tained over 100 |-ig/kg.
Soluble antimony compounds, such as antimonites and
tartrates, are poorly absorbed. For example, only 2 percent
of initial body burden of either trivalent or pentavalent anti-
mony tartrate was present 4 days after a gavage administra-
tion, and over 60 percent of this was in the gastrointestinal
tract (Felicetti et al., 1974). In most rodents, trivalent anti-
mony is excreted primarily in the feces and pentavalent anti-
428
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OTHER MINERALS
429
mony primarily in ttie urine (Otto and Maren, 1950). In hu-
mans, trivalent antimony is excreted in the bile after conju-
gation with glutathione (Bailly et al., 1991), and both va-
lence states are excreted in the urine (Otto et al., 1947). A
review (NRC, 1980a) found that trivalent antimony concen-
trates in the liver of all species studied and in the erythro-
cytes of many species, including humans. Pentavalent anti-
mony has a lesser affinity for the liver than trivalent
antimony and concentrates more in the spleen. Human eryth-
rocytes are almost impermeable to pentavalent antimony.
Metabolic Interactions and Mechanisms of Toxicity
Thiol-containing enzymes are inhibited in vitro by anti-
mony salts. Thus, enzyme inhibition may be one mechanism
through which antimony is toxic. Antimony has been shown
to suppress in vitro arsenic genotoxicity (Gebel, 1998).
Toxicosis and Maximum Tolerable Levels
Generally, compounds containing trivalent antimony are
more toxic than pentavalent antimony. Regardless of valence
state, however, the inherent oral toxicity of antimony com-
pounds is low. Lifetime studies with mice fed drinking water
supplemented with antimony potassium tartrate to provide 5
mg/L revealed no demonstrable toxic effects on males and
only a slight decrease in life span and longevity and some
suppression of growth of females (Schroeder et al., 1968b). A
similar lifetime study with rats found no effect on growth but
a decrease in life span in both sexes (Schroeder et al., 1970).
In 14-day studies, drinking water doses of antimony potas-
sium tartrate estimated at 0, 16, 28, 59, 94, and 168 mg/kg BW
in rats and 0, 59, 98, 174, 273, and 407 mg/kg BW in mice
were poorly absorbed and relatively nontoxic (Dieter et al.,
199 1). The NOAEL was determined to be 2,500 mg antimony
potassium tartrate/L drinking water in both rats and mice
(Lynch etal., 1999). Diets containing 1,000, 5,000, and 20,000
mg/kg antimony trioxide fed for 90 days had no effect on
growth, feed consumption, and clinical variables (Hext et al.,
1999). Poon et al. (1998) provided rats with drinking water
containing 0.5, 5, 50, and 500 mg/L potassium antimony tar-
trate to male and female rats for 13 weeks and found toxico-
logical signs at the highest concentration. These signs included
depressed body weight; hematuria; decreased red blood cell
and platelet counts; increased corpuscular volume; and mild
histological changes in the thyroid, liver, pituitary gland,
spleen (males), and thymus (females). Rabbits may have a
lower tolerance to antimony. After 5 to 20 days, some rabbits
fed 15 mg of potassium antimonyl tartrate (5.5 mg antimony)
per kg BW exhibited fatty degeneration and parenchymal
necrosis of the liver (Pribyl, 1927). Rabbits fed 2 to 6 mg
potassium antimonyl tartrate (0.7 to 2.2 mg antimony) per kg
BW exhibited no pathology.
Acute toxicity induced by feeding relatively high amounts
of potassium antimonyl tartrate was examined in rabbits
(Oelkers, 1937). A single oral dose of 125 mg per kg BW (46
mg/kg antimony) was fatal in all cases; 120 mg/kg BW (44
mg/kg antimony) was almost certainly fatal in 24 to 36 hours;
and 115 mg/kg BW (42 mg/kg antimony) was fatal to 50
percent of the animals. Bradley and Fredrick (1941) found
the minimum lethal dose of potassium antimonyl tartrate
expressed as antimony was 300 mg/kg BW for rats. After
drinking lemonade containing 0.013 percent antimony, 70
people became acutely ill with burning stomach pains, colic,
nausea, and vomiting; most recovered within three hours
(Dunn, 1928; Monier-Williams, 1934). A person consuming
300 mL of lemonade would have received a dose of approxi-
mately 36 mg of antimony, or approximately 0.5 mg/kg for a
70-kg adult.
The signs of antimony toxicity caused by non-oral routes
are extensive and have been reviewed (Winship, 1987).
Setting maximum tolerable limits for domestic animals is
not possible because of the lack of data. The rabbit data sug-
gest that a daily intake of 3 mg Sb/kg BW is an appropriate
conservative limit. The previous edition of this book (NRC,
1980a) suggested a maximum tolerable limit of 70-150 mg
Sb/kg dry diet for the rabbit.
Tissue Levels
Antimony occurs in low amounts in animal and human
tissue. Smith (1967) found that median value for a variety of
human organs fell between 0.05 and 0.15 mg/kg dry weight.
Yukawa et al. (1980) found that means of human organs
except the lung ranged from 0.01 to 0.03 mg Sb/kg fresh
weight. Suminoetal. (1975) found 0.01 and 0.11 mg Sb/kg
fresh tissue, with the highest amounts being in the skin and
adrenal gland. Hamilton et al. (1972/1973) found antimony
in all human tissues but in lower amounts than those above;
mean concentrations were between 0.005 and 0.02 mg/kg
fresh tissue. A review of reported blood concentrations for
humans indicated that the normal concentration apparently
is less than 1 |Jg/L (Nielsen, 1986).
GERMANIUM
Germanium (Ge) is a lustrous, gray-white brittle metal-
loid with a diamond-like crystalline structure (Furst, 1987).
It is similar in chemical and physical properties to silicon
and obtained chiefly from germanite, an ore that contains
about 7 percent germanium and 22 other elements. Varying
average abundances of germanium in the Earth's crust have
been reported, including 1.5 mg/kg (Furst, 1987) and 7 mg/kg
(Chase et al., 2003). Germanium is used in transistors and in
integrated circuits, alloys, and glass (where it increases the
index of refraction).
Biological interest in germanium was stimulated when it
was discovered that some of its organic complexes inhibit
tumor formation in animal models (Sato et al., 1985). The
suggested mechanism behind tumor inhibition is that
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430
MINERAL TOLERANCE OF ANIMALS
germanium enhances immune function. Tliis hias resulted in
the promotion of over-the-counter supplements containing
germanium (e.g., germanium-132 or carboxyethyl germanium
sesquioxide and lactate-citrate-germanate) as anticancer
agents. Additionally, germanium is promoted for the treat-
ment of numerous conditions that could be affected by im-
proved immune function including rheumatoid arthritis, os-
teoarthritis, candidiasis, and chronic viral infections (Chase
et al., 2003). Recently, carboxyethyl germanium sesquioxide
supplementation (18 mg/kg diet) was found to improve trans-
verse bone strength and bone mineral density in rats with
experimental osteoporosis (Matsumoto et al., 2002). Germa-
nium is not considered essential, but low dietary germanium
compared to more normal intakes alters bone and liver min-
eral composition and decreases tibial DNA in rats (Seaborn
and Nielsen, 1994). Compared to when the diet was supple-
mented with 1 mg Ge/kg diet, 10 mg Ge/kg diet as germa-
nium dioxide stimulated growth in rats (Venugopal and
Luckey, 1978) and chickens (Li et al., 1993).
Sources and Metabolism
Because of the limited nutritional interest in germanium,
very few reports have appeared that indicate the germanium
content of animal feedstuffs. The most extensive germanium
analysis of foods was performed by a colorimetric method
almost 40 years ago (Schroeder and Balassa, 1967a). Based
on recent animal tissue analyses by more modern techniques,
the values reported by Schroeder and Balassa (1967a) pro-
vide a reasonable idea of germanium intakes by animals and
humans. Almost all of the 125 foods and beverages they ana-
lyzed contained detectable amounts of germanium, but only
4 of them contained more than 2 mg Ge/kg wet weight, and
only 15 others contained more than 1 mg Ge/kg. The values
they reported for grains included (in mg/kg wet weight): rye,
0.64; wheat, 0.64; oats, 0.20; brown rice, 0.10; and degermed
cornmeal, 0.41. Purina cat chow contained 0.33 mg Ge/kg,
and a rat diet composed of skim milk, corn oil, and rye con-
tained 0.32 mg/kg. The findings of Schroeder and Balassa
(1967a) indicate that most diets of domestic animals would
contain less than 1 mg Ge/kg and human diets would pro-
vide about 1.5 mg/day. Water is not a significant source of
gennanium.
Over 96 percent of an oral dose of 6.94 mg germanium
as germanium dioxide given to rats by stomach tube was
rapidly absorbed from the gastrointestinal tract and ex-
creted mainly via urine (Rosenfeld, 1954). Less than 5 per-
cent was excreted through the bile. Little is known about
the metabolism of germanium ingested with ordinary diets.
However, based on their analysis of foods and urine,
Schroeder and Balassa (1967a) concluded that, like in rats,
dietary germanium is well absorbed in humans and excreted
largely via the kidneys. They calculated that adults ingest
about 1.5 mg Ge/day, and 1.4 mg appears in the urine and
0.1 mg in the feces.
Metabolic Interactions and Mechanisms of Toxicity
The mechanisms through which germanium has toxic ef-
fects, including causing nephropathy and peripheral nerve
disorders, have not been precisely defined. Arginine and
enalapril prevent nephropathy caused by long-term germa-
nium dioxide intake (Nodera and Yanagisawa, 2003); this
suggests that oxidative stress involving nitric oxide might
have a role in germanium toxicity. High dietary germanium
can affect the metabolism or tissue distribution of several
other mineral elements in animals; this may be the basis for
some of the biological effects of germanium. Providing 5
mg Ge/L drinking water for life depressed the chromium
concentration in heart, kidney, and spleen and increased the
copper concentration in livers of rats (Schroeder and Nason,
1976). High doses of germanium protected against acute se-
lenium toxicity and increased urinary selenium excretion
(Paul et al., 1989). Zinc administration prevented the de-
crease in bone alkaline phosphatase activity and DNA con-
tent induced in rats by an oral dose of 2.2 mg Ge/100 g BW
for 3 days (Yamaguchi and Uchiyama, 1987). Germanium
supplementation has been found to reverse changes in rats
caused by a silicon deprivation (Seaborn and Nielsen, 1994).
Toxicosis and Maximum Tolerable Levels
Germanium has a low order of toxicity. The oral LDjq of
germanium dioxide is 3.7 g/kg for male rats, and 6.3 g/kg for
male mice (Hatano et al., 1981). Germanium dioxide toxic-
ity in mice and rats results in tremors, sedation, cyanosis,
vasodilation, hypothermia, and respiratory failure resulting in
death. The oral LD^q for germanium sesquioxide is 1 1.7 g/kg
and 11.0 g/kg for male and female rats, respectively, and
12.5 g/kg and 11.4 g/kg for male and female mice, respec-
tively (Tao and Bolger, 1997). In order to induce chronic
germanium toxicity in rodents, more than 100 times the nor-
mal concentration of usually less than 1 mg Ge/kg diet is
required. Germanium dioxide in amounts of 10 mg Ge/kg
diet stimulated growth, 100 mg Ge/kg had little or no effect,
and 1,000 mg Ge/kg was toxic to rats (Venugopal and
Luckey, 1978) and chicks (Li et al., 1993). Nakano et al.
(1987) provided rats with drinking water containing 0, 100,
or 500 mg germanium dioxide/L; the rats provided the high-
est amount had pathological changes in the kidneys, skeletal
muscles, and myocardium. Rats fed 150 mg GeOj/kg/day
for 13 weeks exhibited decreased body weight and patho-
logical changes in the kidney, liver, and heart (Sanai et al.,
1990). No toxic effects or renal histological abnormalities
were seen in rats fed 120 mg germanium sesquioxide/kg BW
for 24 weeks, but toxic effects were seen in rats given an
equal amount of germanium as germanium dioxide (75 mg/kg
BW) (Sanai et al., 1991a). The germanium dioxide group
exhibited increased blood urea nitrogen and serum phos-
phate, decreased creatinine clearance, weight loss, anemia,
and liver dysfunction. Tubular degeneration and tubulo-
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OTHER MINERALS
431
interstitial fibrosis were seen in tiie kidney. In contrast to tlie
study of Sanai et al. (1991a), Ciiase et al. (2003) described a
study in wiiicfi botti germanium dioxide and germanium
sesquioxide fed at a level of 50 mg/kg diet resulted in some
renal pathology. The only effect a lifetime exposure to 5 mg
Ge/L in their drinking water had on mice and rats was a
slightly shortened life span (Schroeder and Balassa, 1967b;
Schroeder et al., 1968a). The germanium exposure slightly
reduced the incidence of tumors in rats. The major concern
about germanium toxicity in humans is that consuming large
doses in supplements over extended periods of time can lead
to nephrotoxicity and death. At least 3 1 cases of germanium-
associated nephrotoxicity, including 9 fatalities, have been
reported (Chase et al., 2003). Anorexia, weight loss, fatigue,
nausea, vomiting, anemia, and muscle weakness accompa-
nied renal failure. In most of these cases, the individual con-
sumed a few hundred grams of a germanium compound over
several months.
Based on the findings with rodents, the maximum toler-
able level of germanium is greater than 10 mg/kg diet but is
less than 50 mg/kg diet for domestic animals. Sanai et al.
(1991b) has indicated 37.5 mg germanium dioxide/kg BW/day
is tolerated by rats.
Tissue Levels
Because of the lack of reports, germanium analyses of
foods and of human and rodent tissues have to be used to
estimate the germanium content of tissues from domestic
animals. These analyses indicate that the germanium concen-
tration in most tissues is relatively low with normal dietary
intakes. Schroeder and Balassa (1967a) found the following
concentrations (mg/kg wet weight) in foods: pork chops, 0.75;
chicken liver, 0.20; beef liver, 0.36; ground beef, 0.47; lamb
hver, 0.15; haddock filet, 0.28; codfish filet, 0.42; salmon,
1.23; and milk, 1.51. Hamilton et al. (1972/1973) found the
following concentrations in human tissues (mg/kg wet
weight): liver, 0.04; kidney, 9; and muscle, 0.03. Mice fed a
diet containing 0.32 mg Ge/kg and provided drinking water
containing 5 mg Ge/L as sodium germanate for life had in-
creased concentrations of germanium (mg/kg wet weight) in
liver (3.12 versus 0.12) and kidney (2.63 versus 0.49) com-
pared to controls fed regular drinking water (Schroeder and
Balassa, 1967a). The increase in germanium concentrations
was not as marked in rats treated the same as the mice, with
kidney being 0.62 vs. 0.18 and liver being 0.27 vs. 0.14 mg
Ge/kg wet weight (Schroeder et al., 1968b). These rodent results
indicate that tissue levels found in domestic animals with
elevated intakes of germanium would not produce foods high
enough in germanium to be of toxicological concern for humans.
LITHIUM
Lithium (Li) is a soft, silver-white alkali metal that has
only half the density of water (Wikepedia, 2004a). With a
mean concentration of 50-65 mg/kg, lithium is 27th in el-
emental abundance in the Earth's crust. The minerals lepido-
lite, spodumene, petalite, and amblygonite are the more im-
portant sources of the lightest metal lithium. Lithium is
primarily used in heat transfer alloys, batteries, lubricants,
and mood-stabilizing drugs.
Biological interest in lithium focuses mainly around its
use as a mood-stabilizing drug (Birch, 1995), but some inter-
est stems from findings suggesting that it has other benefi-
cial, perhaps essential, functions in higher animals, and can
be used as a food aversion substance for grazing animals.
Lithium deprivation (less than 1.5 mg/kg diet) has been re-
ported to depress fertility, birth weight, lifespan, liver
monoamine oxidase activity, and the activity of several liver
and blood enzymes used in the citrate cycle, glycolysis, and
nitrogen metabolism in goats (Anke et al., 1991). In rats,
lithium deprivation (5-15 |Jg/kg diet) depressed fertility,
birth weight, litter size, and weaning weight (Patt et al., 1978;
Pickett and O'Dell, 1992). In addition, the lithium content
was depressed in testes, seminal vesicles, and epididymis.
Lithium concentrations were relatively high in the pituitary
and adrenal glands and remained constant through two gen-
erations regardless of dietary lithium. These findings sug-
gest lithium may have a role in the regulation of some endo-
crine function. Large doses of lithium chloride given by
gavage while providing a toxic plant material for consump-
tion result in an aversion to the consumption of those mate-
rials by grazing cattle and sheep. For example, a 200 mg/kg
BW dose of lithium chloride created aversion to larkspur
(Ralphs, 1997) and locoweed (Ralphs et al., 1997) in cattle,
and a 160 mg/kg BW dose resulted in aversion to vermeerbos
by sheep (Snyman et al., 2002). In humans, low lithium in-
takes from water supplies (little or no lithium compared to
70-170 |Jg/L) have been associated with increased rates of
suicides, homicides, drug use, and other crimes (Schrauzer
and Shrestha, 1990; Schrauzer, 2002). Lithium also has been
shown to have insulinomimetic (Rossetti et al., 1990) or an-
tidiabetic (Hu et al., 1997) actions.
Sources and Metabolism
Lithium is taken up by all plants. However, because it
apparently is not required for growth and development, the
uptake is dependent upon the available lithium in the soil.
Thus, similar foods and feeds grown on different soils can
have widely different lithium concentrations. This variance
probably explains the large range (8.6 to 546 |ig/day) for
reported daily lithium intakes by humans (Van Cauwenbergh
et al., 1999). The limited number of reports that give the
lithium concentration in materials used as animals feeds in-
dicates that forage and grains generally are good sources of
lithium but vary with the soil on which they are grown. For
example, Anke et al. (1991) reported the following concen-
trations (mg/kg DW) for feedstuffs grown on lithium-rich
and lithium-poor soils, respectively: red clover, 3.0 and 1.4;
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MINERAL TOLERANCE OF ANIMALS
rye, 4.1 and 1.0; wheat, 2.9 and 0.7; barley, 1.1 and 0.7; and
oats, 1 and 0.5. These data indicate that animal diets nor-
mally contain a few milligrams of lithium per kilogram.
However, it should be noted that there are some plants that
can accumulate lithium in very high concentrations; for ex-
ample, up to 1,000 mg Li/kg can occur in nightshade species
(Schrauzer, 2002). Drinking water also can be a significant
source of lithium as some ground water may reach 0.5 mg/L
and up to 100 mg Li/L are found in some natural mineral
waters (Schrauzer, 2002). Concentrations of 1.5 and 5.2 mg
Li/L have been found in river water from lithium-rich re-
gions of northern Chile (Zaidivar, 1989). Most drinking wa-
ter contains less than 25 |Jg/L (Anke et al., 1997).
Ingested lithium in the form of soluble salts is essentially
100 percent absorbed by the small intestine and is excreted
primarily by the kidneys. Several studies have indicated that
lithium transfer in the gastrointestinal tract occurs by
paracellular transport via the tight junctions and pericellular
spaces and not by passage through the cell (Birch et al.,
1994). Lithium is not protein-bound and distributes through-
out body water with only small differences between extra-
cellular and intracellular concentrations (Schrauzer, 2002).
Lithium distribution and excretion is similar to that of so-
dium. About 90 percent of lithium excretion occurs via urine;
most of the rest is excreted via the feces, with about 20 per-
cent arising from the bile and the remainder through the in-
testinal wall (Anke et al., 1997).
Metabolic Interactions and Mechanisms of Toxicity
Probably the most important interaction involving lithium
is that with sodium. The replacement of lithium with sodium
apparently can have undesirable consequences. Pickett and
O'Dell (1992) reported that increased sodium in the diet ex-
acerbated the impaired reproductive performance induced
by lithium deprivation in rats.
Other possible interactions in addition to that with so-
dium may be involved in lithium toxicity. Lithium may dis-
place potassium, magnesium, and calcium from membrane
or enzyme sites with resultant impaired functions. For ex-
ample, the Li'"*" ion has been shown to interfere with numer-
ous magnesium-dependent enzymes including adenylate cy-
clase, Mg^''"-ATPase, cholinesterase, DNA polymerase,
pyruvate kinase, tyrosine aminotransferase, and tryptophan
hydroxylase (Geisler and Mork, 1990). Magnesium enzymes
involved in the inositol signaling pathway (which also in-
volves calcium) are inhibited by lithium. It has been stated
that the biochemical and toxicological effects of lithium can
be explained by its selective interference with the
phosphoinositide cycle (Ragan, 1990; Anke et al., 1997).
Toxicosis and Maximum Tolerable Levels
The toxicity of oral lithium for domestic animals has been
studied mostly in Germany by Anke and colleagues (1991,
1997). Food consumption was reduced by 50 mg Li/kg diet
by chickens, 125 mg Li/kg diet by pigs, and 100 mg Li/kg
diet by cattle (Anke, 1991). Other signs of toxicity found by
Anke et al. (1991) included depressed weight gain, egg pro-
duction, and egg weight in chickens fed 100 or 150 mg Li/kg
diet; less weight gain in cattle fed 100 or 200 mg Li/kg diet;
and less weight gain and enormous water consumption in
pigs fed 500 mg Li/kg diet. Pigs fed 1,000 mg Li/kg diet died
within 92 days. No significant toxicity signs were seen in
chickens fed 25 mg Li/kg diet, or in cattle fed 10 or 50 mg
Li/kg diet. Pigs fed 17 to 84 mg Li/kg diet showed increased
serum lithium concentrations and less biting activity among
unacquainted pigs, but weight gain and feed efficiency were
not affected (McGlone et al., 1980). Regius et al. (1993)
found that 25 mg Li/kg diet tended to improve growth and
reduce mortality of lambs, but 50 mg Li/kg diet depressed
growth of lambs.
The clinical control of bipolar illness in humans is
achieved by doses of 900 to 1,500 mg lithium carbonate/day
or 169 to 282 mg Li/day. These dosages elevate the normal
serum lithium concentration from 2-20 |Jg/L to 2,780-
55,550 Mg/L. Higher blood lithium concentrations can have
toxic side effects of tremor, dizziness, drowsiness, and diar-
rhea (Weiner, 1991).
Based on the findings with chickens, cattle, pigs, and
sheep, the maximum tolerable lithium level for domestic
animals is about 25 mg/kg diet. This amount apparently does
not cause food aversion and thus decreased food intake, nor
does it cause apparent toxicity signs not related to decreased
food intake.
Tissue Levels
The concentration of lithium in animal and human tissue
and fluids is very dependent upon lithium intake. For example,
the following mean concentrations were found in tissues
(|ig/kg DW) and fluids (mg/L) from rats fed 2 or 500 |Jg Li/kg
diet as lithium carbonate, respectively, for three generations:
liver, 1.6 and 12; heart, 2.3 and 25; skeletal muscle, 4.6 and
34; kidney, 2.9 and 40; bone, < 7 and 304; whole blood, 0.9
and 35; and blood serum, 2.3 and 67 (Patt et al., 1978; Pickett
and O'Dell, 1992). Tissue lithium concentrations in domes-
tic animals fed normal diets probably are similar to those of
rats fed the diet containing 500 |ig Li/kg.
RARE EARTHS
The rare earths are a relatively abundant group of 17 ele-
ments composed of scandium (Sc), yttrium (Y), and the lan-
thanides cerium (Ce), dysprosium (Dy), erbium (Er), eu-
ropium (Eu), gadolinium (Gd), holmium (Ho), lanthanum
(La), lutetium (Lu), neodymium (Nd), praseodymium (Pr),
promethium (Pm), samarium (Sm), terbium (Tb), thulium
(Tm), and ytterbium (Yb). "Rare" earths is a historical mis-
nomer; persistence of the term reflects unfamiliarity rather
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OTHER MINERALS
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than true rarity. Some rare earth elements are as abundant in
the Earth's crust as more familiar metals such as chromium,
nickel, copper, zinc, molybdenum, tin, tungsten, and lead.
The abundances of the elements in the Earth's crust range
from 60 mg/kg for cerium (25th in abundance of the 78 com-
mon elements) to 0.5 mg/kg for thulium and lutetium
(Hedrick, 2001). The elemental forms of rare earths are iron
gray to lustrous metals that are typically soft, malleable, duc-
tile, and usually reactive, especially at elevated temperatures
or when finely divided. The principal economic sources of
rare earths are the minerals bastnasite, monazite and loparite,
and the lateritic ion-adsorption clays. The rare earth elements
are used in a wide variety of applications including glass
polishing and ceramics; petroleum refining catalysts; auto-
motive catalytic converters; metallurgical additives and al-
loys; rare earth phosphors for lighting, televisions, computer
monitors, radar, and x-ray intensifying film; and permanent
magnets (Hedrick, 2001).
Biological and toxicological interest in the rare earth ele-
ments have arisen from the common practice in mainland
China to add their soluble salts, especially lanthanum and
cerium salts, to fertilizers for the purpose of increasing crop
yields (Guo, 1988). The rare earth elements have been shown
to increase in crops the rates of photosynthetic light reac-
tions, chlorophyll content, and transport of photosynthetic
end products from leaves to seeds (Chen et al., 2001; Fashui
et al., 2002). A review of the literature by He et al. (1999)
indicates that appropriate supplementation of rare earth ele-
ments can increase the feed conversion and weight gain of
beef cattle, sheep, pigs, rabbits, chickens, and ducks; the milk
production of dairy cattle; the egg production of hens; and
the output, survival rate, and feed conversion of grass carp
and prawn. He and Rambeck (2000) suggested that rare earth
elements may be useful as safe and inexpensive alternatives
to antibiotics as growth promoters in animal feed. Horovitz
(1993) has suggested that scandium and yttrium have ben-
eficial effects in animals and humans. Cerium has been found
to stimulate collagen and noncollagen protein synthesis in
rat hearts (Prakash Kumar et al., 1995). Whether this stimu-
lation is beneficial or not is uncertain because it has been
speculated that this could lead to cardiac fibrosis (Prakash
Kumar and Shivakumar, 1998).
Sources and Metabolism
Surprisingly little has been published about the concen-
tration of rare earth elements in foods and feedstuffs consid-
ering their use to increase crop production in some coun-
tries, especially China. Iyengar (1998) indicated that the
human daily dietary intake of cerium was less than 15 |Jg and
scandium was less than 0.5 |Jg. Kavas-Ogly et al. (1998)
reported that various Uzbek foods made mostly from grains
contained 1.1 to 1.2 pg Sc/kg. The scandium concentration
in 27 different Uzbek food dishes ranged from 0.8 to 5.9 [Jg/
kg. The concentration of scandium in Brazilian diets was
found to range between 1.0 and 1.8 pg/kg (Favaro et al.,
1997).
Very limited information is available on the metabolism
of the rare earth elements. They apparently are poorly ab-
sorbed (less than 1 percent) and therefore can be used as
nonabsorbable fecal markers (Fairweather-Tait et al., 1997).
A study with mice indicated that absorbed rare earth ele-
ments are rapidly accumulated in teeth and bones (Zhang et
al., 1988). After 73 days of feeding 0.83 Mg Y H- Yb/day,
these rare earth elements ranged from nondetectable to traces
in most other organs (Zhang et al., 1988). An exception was
gallbladder, which contained 22.68 mg of Y H- Yb/kg; this
high concentration suggests that the bile is a significant ex-
cretory route for the rare earth elements.
Metabolic Interactions and Mechanisms of Toxicity
The ionic forms of rare earth elements share biologically
important properties with divalent calcium. Because they
have similar ionic radii, coordination chemistry, and affinity
for oxygen donor groups, rare earth ions strongly interact
with Ca^"^-binding sites on a wide range of proteins (Enyeart
et al., 2002). Thus, the toxicological and beneficial effects of
the rare earth elements probably result from them displacing
or being a surrogate for calcium in various biological func-
tions. For example, in the rat model of chronic renal failure,
there is an association between lanthanum accumulation and
mineralization defects characteristic of osteomalacia
(Vanholder et al., 2002). Findings with plants suggest that
Eu-'"'' can replace Ca^"*" in the calcium/calmodulin-dependent
phytochrome signal transduction system and promote plant
development by enhancing the transport of calcium across
the plasma membrane (Zeng et al., 2003).
Toxicosis and Maximum Tolerable Levels
The rare earth elements are relatively nontoxic to ani-
mals. When rats were administered daily oral doses of 0, 40,
200, and 1,000 mg LaCl3-7H20/kg BW for 28 days, only the
1,000 mg/day dose irritated the stomach mucosa and changed
some liver enzymes suggestive of a hepatotoxic effect
(Ogawa, 1992). When rats were gavaged with daily doses of
0, 40, 200, and 1,000 mg EuCl3-6H20/kg BW for 28 days,
both the 200 and 1,000 mg/kg doses significantly decreased
body weight gain because of a reduction in food consump-
tion (Ogawa et al., 1995). However, hyperkeratosis of the
forestomach and eosinocyte infiltration of the stomach mucosa
occurred only in rats dosed with 1,000 mg/kg BW/day. Based
on these findings, it was concluded that NOAEL for the
europium salt was 200 mg/kg BW/day. Feeding a rare earth
mixture containing mostly chlorides of lanthanum, cerium,
and praseodymium such that the final dietary concentration
of lanthanum was 36-43 mg/kg and cerium was 49-57 mg/kg
had only beneficial effects in pigs (He and Rambeck, 2000).
Considering that the mixture contained other rare earth
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MINERAL TOLERANCE OF ANIMALS
elements, these findings indicate thiat diets containing over
100 milligrams of rare earth elements per kilogram are safe.
Subchronic and chronic toxicity studies showed no abnor-
mal or specific pathological changes in monkeys dosed with
100 mg/kg BW or in rats dosed with 200 or 1,800 mg/kg BW
of a mixture of rare earth nitrates (Ce, La, Nd, Pr, and Sm) (Ji
and Cui, 1988) Rat fetuses did not show any teratogenicity
when dams were fed up to 330 mg of the nitrate mixture/kg
BW. The oral LD^q for the mixture ranged from 1,397 to
1,876 mg/kg BW for mice, rats, and guinea pigs.
Based on the limited toxicity studies done, the maximum
tolerable level for the rare earth elements is high. Diets con-
taining 100 mg/kg should be considered safe. Because
feedstuffs apparently contain low amounts of the rare earth
elements, they are of toxicological concern only when
supplemented in excessive amounts.
Tissue Levels
The concentrations of most rare earths in animal and
human tissue and fluids are quite low. Fujimori et al. (1996)
found that the lanthanum, cerium, and neodymium concen-
trations in human serum were 360, 584, and 212 ng/L,
respectively. The serum concentrations of praseodymium,
samarium, gadolinium, dysprosium, europium, and ytterbium
ranged from 34.6 to 53.2 ng/L, and the concentrations of
europium, terbium, holium, thulium, and lutetium ranged
between 4.6 and 10.5 ng/L. Katoh et al. (2002) found lantha-
num and scandium arithmetic mean concentrations (|Jg/kg
DW) were, respectively, in human heart, 32 and 5; kidney,
64 and 4; liver, 285 and 5; and muscle, 55 and 4. Benes et al.
(2000) found cerium and lanthanum geometric mean con-
centrations (pg/kg wet weight) were, respectively, in human
kidney, 4 and 3; liver, 43 and 27; and bone, 49 and 27. The
lanthanum concentration in human milk was found to range
between < 0.05 to 3.7 |jg/L (Krachler et al., 1998; Rossipal et
al., 1998). After 73 days of feeding 0.83 Mg Y H- Yb/day to
mice, Zhang et al. (1988) found the following concentra-
tions of the combined elements (mg/kg wet weight): in mice
liver, 0.229; kidney, 0.521; heart, 0.929; blood, 0.942;
muscle, below detection limit; and bone, 2.464.
RUBIDIUM
Rubidium (Rb) is a soft, silvery-white alkali metal that
can be liquid at room temperature, ignites spontaneously in
air, and reacts violently with water (Wikipedia, 2004b).
Rubidium is the 16th most abundant element in the Earth's
crust (310 mg/kg) and is commercially obtained from the
minerals lepidolite and pollucite. Rubidium compounds are
used for chemical and electronic applications, and in fire-
works for a purple color.
Biological interest in rubidium has resulted from findings
suggesting that it is beneficial, or possibly essential, for
higher animals. Compared to goats fed 1 or 10 mg Rb/kg
diet, goats fed less than 0.28 mg Rb/kg diet exhibited de-
creased food intake, growth, milk production, and life ex-
pectancy, and increased spontaneous abortions (Anke et al.,
1993). These rather general deprivation findings have not
been confirmed in another research setting and do not indi-
cate a possible biochemical function. Rubidium has a
physiochemical relationship to potassium and thus may act
beneficially through being a nutritional substitute for potas-
sium. Evidence for this is that adding rubidium to potas-
sium-deficient diets prevented the occurrence of characteris-
tic lesions in kidneys and muscles of rats (Follis, 1943).
Sources and Metabolism
Very little reported rubidium analyses of animal feeds
exist. Becker et al. (1975) found that rubidium concentra-
tions in swine feeds, piglet starter rations, and various mixed
feeds ranged from 2.6 to 26. 1 mg/kg DW. The rubidium con-
centrations in most animal feedstuffs probably are in this
range based on analysis of human foods that are similar to
those fed to animals (Varo et al., 1980a, b; Anke and
Angelow, 1995).
The absorption, distribution, and excretion of rubidium in
animals are similar to potassium. Findings from studies us-
ing brush border membrane vesicles isolated from rabbit je-
junum indicate that rubidium and potassium use the same
transport system (Gunther and Wright, 1983). Thus, ru-
bidium is rapidly and highly absorbed by mammals (Schafer
and Forth, 1983). Also, human studies indicate that rubidium
is actively transported from the mother to fetus (Krachler et
al., 1999). The major route of rubidium excretion is through
urine, with a kidney clearance rate slightly less than potas-
sium (Kunin et al., 1959). The intestine also is involved in
rubidium excretion. Schafer and Forth (1983) found that ru-
bidium was excreted against a concentration gradient from
blood into the lumen of both the small and large intestine of
rats. Anke and Angelow (1995) reported that 30 percent of
ingested rubidium is excreted through the feces and 70 per-
cent through the urine by humans.
Metabolic Interactions and Mechanisms of Toxicity
In addition to absorption and excretion findings, a depri-
vation study also indicated that the major metabolic interac-
tion involving rubidium is that with potassium. Yokoi et al.
(1994) found that rats fed diets containing 0.54 mg Rb/kg,
compared to those fed 8.12 mg Rb/kg, had increased potas-
sium in the plasma, kidney, and tibia, but decreased potas-
sium in testis. In addition, the rubidium deprivation de-
creased phosphorus in the heart and spleen, decreased
calcium in the spleen, and increased magnesium in the tibia.
These changes suggest that rubidium intake can affect phos-
phorus, calcium, and magnesium metabolism. Rubidium also
might interact with selenium. It has been suggested that high
dietary selenium may depress rubidium absorption because
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OTHER MINERALS
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rubidium concentrations decreased as selenium concentra-
tions increased in serum, erytlirocytes, and breast millc of
lactating women in seleniferous areas of Venezuela (Negretti
de Bratter et al., 2000).
The mechanism for rubidium toxicity most likely is the
inefficient replacement of potassium in critical biochemical
functions. For example, when injected in a dose that substi-
tutes for more than 40 percent of intracellular potassium,
rubidium may cause cardiac arrhythmia, generalized con-
vulsions, and death (Meltzer, 1991). Because it mimics po-
tassium, rubidium may be toxic through the same mecha-
nisms as those for potassium toxicity.
Toxicosis and IVIaximum Tolerable Levels
The most significant oral toxicity study is that performed
by Glendening et al. (1956). They found that rats fed diets
containing 0.1 percent rubidium (1,000 mg/kg) had slightly
depressed growth and gave birth to young that did not sur-
vive when fed the same diet. The growth of rats fed diets
containing 0.2 percent rubidium (2,000 mg/kg) was severely
depressed, and the rats did not reproduce. Other signs of
toxicity with dietary rubidium at 0. 1 percent and above were
poor hair coat, sore noses, sensitivity, extreme nervousness
leading to convulsions in advanced stages, and finally death.
Purified diets containing 0.02 percent (200 mg/kg) rubidium
were not toxic to rats. Rubidium chloride injected intraperi-
toneally induces irritability and aggressive behavior in rats
(Stolk et al., 1971) and monkeys (Meltzer et al., 1969). The
rubidium treatment increases the release and turnover of
brain stem norepinephrine (Stolk et al., 1970).
The rat study of Glendening et al. (1956) indicates that
the maximum tolerable level for rubidium is somewhere be-
tween 0.02 percent and 0.1 percent (200 and 1,000 mg/kg) of
the diet and would be between 20 to 100 times greater than
levels normally found in animals diets. Thus, rubidium is not
a toxicological concern for animals. Toxicological intakes
of rubidium would only occur with intentional dosing or
supplementing with high amounts of rubidium salts.
Tissue Levels
Rubidium occurs in relatively high amounts in tissues and
fluids. Ward and Abou-Shakra (1993) summarized the re-
ported concentrations of rubidium in human serum and
plasma; the means ranged from 150 to 265 |Jg/L. They also
analyzed normal human tissues and found the following
mean rubidium concentrations (mg/kg WW): liver, 8; kid-
ney, 6.5; and bones, 1. Yokoi et al. (1994) found that dietary
rubidium affected tissue and fluid rubidium concentrations
in rats. They found the following rubidium concentrations
(mg/kg WW) in rats fed 0.54 and 8.12 mg Rb/kg diet, re-
spectively: heart, 0.74 and 9.83; liver, 1.49 and 20.5; kidney,
1.09 and 13.8; muscle, 1.18 and 15.0; tibia, 0.97 and 4.27;
and blood (mg/L), 0.46 and 5.5. Anke and Angelow (1995)
found the following mean concentrations of rubidium (|Jg/g
DW) in liver and kidney, respectively, for cattle, 36 and 31.8;
sheep, 33.6 and 40.3; pigs, 13.6 and 14.3; and cats, 16.4 and
17. Toxic intakes of rubidium markedly increase the
rubidium concentration in tissues. Glendening et al. (1956)
found that 0.25 percent (2,500 mg/kg) compared to less than
0.02 percent (200 mg/kg) dietary rubidium increased
rubidium concentrations from 100 to 200 mg/kg DW to
8,000 to 17,000 mg/kg DW in liver, heart, muscle, and
kidney of rats.
SILVER
Silver (Ag) is a white lustrous metal whose concentration
in the Earth's crust is about 0. 1 mg/kg. Silver of commercial
value is primarily a by-product of the mining of nonferrous
base metals such as copper, lead, and zinc. Major uses of
silver are in the manufacture of tableware, jewelry, decora-
tive items, and coinage. Industrial and technical uses include
photographic materials, electrical and electronic products,
catalysts, brazing alloys, dental amalgam, and bearings
(Hilliard, 2003). Use in coinage and photographic materials
has declined markedly recently.
No essential metabolic function for silver has been iden-
tified in animals. However, Brauner and Wood (2002) found
that 1 compared to 0.1 [ig Ag/L as silver nitrate in moder-
ately hard water increased the rate of growth and
ionoregulatory development in rainbow trout. Biological and
toxicological interest in silver mainly arose from findings
showing that it affects vitamin E, selenium, and copper me-
tabolism and has possible use as a drinking water disinfec-
tion agent. Recently there has been a revival in the promo-
tion of colloidal silver supplements for the prevention and
treatment of many human diseases.
Sources and Metabolism
There are no reports showing the silver concentrations in
common feedstuffs. Bowen (1966) indicated that land plants
in general have a mean concentration of 60 |Jg Ag/kg. Thus,
diets apparently are not a significant source of silver for ani-
mals or humans.
Studies on the metabolism of ingested silver are limited.
Scott and Hamilton (1950) found that a radiotracer dose of
silver administered by stomach tube was 99 percent excreted
in the feces by rats at 4 days post-dosing. Intramuscularly
and intravenously administered radiosilver were also elimi-
nated via the feces. Recent findings show that silver is ex-
creted in the bile and indicate that silver and copper share a
common transport system for their hepatobiliary removal
(Dijkstra et al., 1996). A study of the distribution of silver in
mice that were provided drinking water containing 0.03 mg
Ag/L as radiolabeled silver nitrate for one to two weeks
found that the highest concentrations of the radiolabel
occurred in musculus soleus, cerebellum, spleen, duodenum.
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MINERAL TOLERANCE OF ANIMALS
and myocardial muscle (in rank order) (Pelkonen et al.,
2003).
Metabolic Interactions and Mechanisms of Toxicity
In the 1950s, silver, provided as silver nitrate in drinking
water (Shaver and Mason, 1951) of rats or as silver acetate
(20 mg Ag/kg) in the diet of chicks (Dam et al., 1958), was
found to be more toxic to vitamin E-deficient than vitamin
E-adequate animals. These observations led to studies show-
ing an antagonistic relationship between silver and selenium.
Dip lock et al. (1967) found that providing vitamin E-defi-
cient rats with drinking water containing 0.15 percent silver
acetate resulted in liver necrosis and mortality that could be
totally prevented by tocopherols, partially prevented by add-
ing 1 mg Se/kg diet, and only marginally alleviated by an
additional 0.15 percent dietary methionine. Bunyan et al.
(1968) found that a diet containing lard and combined with
drinking water containing 0.15 percent silver as silver ac-
etate resulted in green exudates in chicks that were prevented
by either vitamin E or selenium. Peterson and Jensen (1975a)
found that 1 mg Se/kg diet or 100 lU vitamin E/kg diet pre-
vented depressed growth and mortality in chicks caused by
900 mg Ag/kg diet as silver nitrate. Adding 0.15 percent
cystine to the diet stimulated growth but did not prevent the
mortality, largely from exudative diathesis. Jensen (1975)
found that 1,000 mg Ag/kg diet as silver nitrate prevented
growth depression and mortality caused by 80 mg Se/kg diet.
Radiotracer studies and biochemical changes indicate that
silver interferes with the absorption of selenium. Feeding
250 mg Ag/kg diet as silver acetate decreased blood sele-
nium and glutathione peroxidase activity in rats (Yoshida,
1993); silver also increased serum thyroxine concentration.
Hill et al. (1964) reported that 25 mg Cu/kg diet were
totally effective in preventing mortality and depressed
growth, hemoglobin, and aorta elastin content caused by
feeding 200 mg Ag/kg diet to chicks.
Peterson and Jensen (1975b) observed that increased heart
weight, mortality, and decreased aorta elastin induced by 900
mg Ag/kg practical diet was effectively prevented by a
supplement of 50 mg Cu/kg; depressed growth was only par-
tially corrected. In turkeys, 900 mg Ag/kg diet depressed
growth, reduced packed cell volume, increased heart size,
and caused gizzard musculature degeneration. The gizzard
degeneration was completely prevented by the addition of 1
mg Se/kg diet and partially prevented by the addition of 50
lU vitamin E/kg diet (Jensen et al., 1974). The microcytic,
hyperchromic anemia was prevented by the addition of 50
mg Cu but not 5 mg Cu per kg diet; both copper treatments
reduced heart size.
Silver apparently antagonizes copper metabolism by in-
terfering with the copper-transporting and oxidase functions
of ceruloplasmin. Developmental abnormalities and prena-
tal deaths caused by feeding silver chloride to rat dams
throughout term were prevented by injections of ceruloplas-
min (Shavlovski et al., 1995). Findings have been obtained
that indicate silver competes with copper for incorporation
into the site of apo-ceruloplasmin that results in the active
holo-ceruloplasmin (Hirasawa et al., 1994, 1997; Sugawara
and Sugawara, 2000).
The antagonistic relationships between silver and sele-
nium and between silver and copper indicate that the mecha-
nism through which silver has toxic effects in animals is by
interfering with copper and selenium uptake and function.
Also, because silver is easily reduced, it could initiate
peroxidation that requires higher intakes of nutrients, such
as copper, selenium, and vitamin E, involved in protection
from reactive oxygen species (Whanger and Weswig, 1978).
The manifestations of acute silver toxicity in fish are the
result of the failure to maintain constant concentrations of
sodium and chloride ions in blood plasma (Hogstrand and
Wood, 1998). For freshwater fish, this apparently occurs by
ionic silver preventing active Na"*" and CI" uptake by inhibit-
ing gill basolateral Na"*", K^-ATPase activity (Wood et al.,
1999). In marine fish, the intestine appears to be the primary
toxic site of action.
Toxicosis and Maximum Tolerable Levels
Feeding a diet containing 100 mg Ag/kg as silver sulfate
to one-day-old chicks did not adversely affect growth, mor-
tality, hemoglobin concentration, and elastin content of the
aorta (Hill et al., 1964). Higher dietary concentrations of
silver induced signs associated with copper and selenium
deficiency including depressed growth, hemoglobin and aortic
elastin, increased mortality and heart weight, and exudative
diathesis in chicks (Hill et al., 1964; Bunyan et al., 1968;
Petersen and Jensen, 1975a,b). In turkeys, 300 mg Ag/kg diet
depressed growth, and 900 mg Ag/kg diet induced gizzard
musculature dystrophy, enlarged hearts, and decreased
packed red blood cell volume, in addition to depressed
growth (Jensen et al., 1974). In growing rats, signs of silver
toxicity included depressed growth, increased mortality,
liver necrosis, and a generalized deposition of silver in tis-
sues (argyrosis) (Shaver and Mason, 1951; Diplock et al.,
1967). A lifetime administration of 1,000 mg Ag/L of drink-
ing water produced an intense pigmentation of many tissues
in rats (Olcott, 1948, 1950). The argyrosis was most marked
in the basement membrane of the glomeruli, the portal vein,
and other parts of the liver; the choroid plexus of the brain;
the choroid layer of the eye; and in the thyroid gland. Argyria
in people caused by the use of colloidal silver still occurs
(Gulbranson et al., 2000).
Rainbow trout fed 3.1 mg/kg diet as biologically incorpo-
rated silver in trout meal showed no adverse effects when
compared to trout fed 0.05 mg Ag/kg diet (Galvez et al.,
2001). Ionic silver in water is highly toxic to fish, with fresh-
water fish more sensitive to the silver ion than marine fish
(Hogstrand and Wood, 1998). The 96-hour LCjq concentra-
tion for rainbow trout in synthetic soft water was determined
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OTHER MINERALS
437
to be 13.3 |ig total Ag/L and 3.3 |ig dissolved Ag/L (Morgan
and Wood, 2004).
Silver is a relatively nontoxic element when ingested with
a diet that contains rich amounts of copper, selenium, and
vitamin E. Because no adverse effects were seen in chicks
fed 100 mg Ag/kg diet, the maximum tolerable level for do-
mestic animals probably is about this amount. The World
Health Organization allows silver ions up to 0.1 mg/L in
drinking water for disinfection. A maximum tolerable limit
for fish is probably higher than 3 mg Ag/kg diet based on the
study of Galvez et al. (2001) and about 1 \ig ionic Ag/L in
water (Brauner and Wood, 2002).
Tissue Levels
Only limited information is available about silver con-
centrations in tissues and fluids of domestic animals. How-
ever, they are probably very low under normal conditions.
Cow's milk was found to contain 27 to 54 pg Ag/L (Murthy
and Rhea, 1968). Hamilton et al. (1972/1973) found the fol-
lowing mean silver concentrations (mg/kg fresh weight) in
human tissues: kidneys, 0.002; liver, 0.006; muscle, 0.002;
and whole blood, 0.008. Versieck and Cornells (1980) found
that reported values for the silver concentrations in plasma
and serum varied widely from 0.68 to 1 13 |Jg/L. They con-
cluded, however, that the normal concentration is less than
1 ^tg/L.
STRONTIUM
Strontium (Sr) is a soft silver-white or yellowish alkaline
earth metal whose concentration in the Earth's crust aver-
ages 0.04 percent, which makes it the 15th element in abun-
dance (Ober, 2002). Strontium is highly reactive and turns
yellow with the formation of oxide when exposed to air.
Strontium is recovered from strontianite (SrCOj) and celes-
tite (SrSO^), its two principal naturally occurring mineral
forms. Strontium is used mainly in color television picture
tube faceplates; other important uses for strontium are ferrite
ceramic magnets and pyrotechnics (Ober, 2002).
Strontium has not been shown to be essential for either
plants or animals. Rygh (1949) reported that strontium dep-
rivation depressed growth, impaired the calcification of
bones and teeth, and increased dental caries incidence in rats
and guinea pigs, but these findings have not been confirmed.
Biological interest in strontium was small until it was estab-
lished that ^°Sr, a by-product of nuclear fission and a beta-
emitter with a long half-life (28.78 years), can substitute for
calcium in bone. This substitution occurs because strontium
naturally exists as a divalent cation and has an atomic radius
similar to calcium. Recently, interest in strontium has fo-
cused on its ability, especially in the form strontium ranelate
(a compound containing the organic acid, ranelic acid, and
two atoms of strontium), to increase bone formation and
uncouple bone formation from bone resorption (Marie et al..
1993, 2001). Strontium ranelate is a promising pharmaceuti-
cal for the treatment of postmenopausal osteoporosis
(Meunier et al., 2002).
Sources and Metabolism
In general, foods and feedstuffs of plant origin are appre-
ciably richer sources of strontium than are animal products,
except where the latter include bone. Strontium tends to be
concentrated in the bran rather than in the endosperm of
grains. The strontium content is higher in leafy dicotyledons
than in monocotyledons; thus, for animals, strontium intakes
would be much higher from leguminous than from gramine-
ous forages. Mitchell (1957) reported that the strontium con-
centration (mg/kg DW) in red clover growing on different
soils ranged from 53 to 115 (mean 74) and ryegrass ranged
from 5 to 18 (mean of 10). Schroeder et al. (1972) deter-
mined the strontium concentrations (mg/kg) in several items
that are used as animal feeds; these included wheat, 3.46;
oats, 3.01; millet, 1.29; buckwheat, 3.84; barley, 0.98; and
hay, 9.4. As reviewed by Nielsen (1986) and Anke et al.
(2000b), the human daily strontium intake from food is usu-
ally no more than a few milligrams. This intake is consistent
with the strontium analyses of foods performed by Schroeder
et al. (1972), who found most foods contained between 0.5
and 5.0 mg Sr/kg. Water may significantly add to the intake
of strontium. Schroeder et al. (1972) estimated that water
provides 10 percent of the daily intake of strontium for hu-
mans. A review by Wasserman et al. (1977) indicated that
most drinking water contains less than 1 mg Sr/L, but higher
concentrations (e.g., 1.6 mg/L) have been found in some
waters (Wolf etal., 1973).
The metabolism of strontium is similar to calcium. Stron-
tium and calcium use the same mechanisms for absorption
from the gastrointestinal tract, concentrate in bone, and are
excreted mainly in the urine after absorption. Strontium can
substitute for calcium in a variety of physiological processes
including blood clotting, bone formation, and muscular con-
traction. However, these processes are slowed when stron-
tium is substituted for calcium. Also, wherever there is a meta-
bolically controlled passage of ions across a membrane (e.g.,
gastrointestinal absorption, renal excretion, lactation, and pla-
cental transfer), calcium is transported more effectively than
strontium (Comar and Wasserman, 1964). This discrimina-
tion between calcium and strontium apparently develops as an
organism matures. Mechanisms discriminating against the
uptake of strontium in favor of calcium develop gradually in
rats (Sugihira et al., 1990), and there is a discrimination against
strontium in favor of calcium in the tubular reabsorption of
these elements that is not fully developed in young rats before
weaning (Sugihira and Suzuki, 1991).
Seifert et al. (2002) found an apparent strontium absorp-
tion of 20 percent from a mixed diet by humans. This apparent
absorption is similar to the 20 to 25 percent range found by
Spencer etal. (1960) using a tracer dose of ^-^Sr. A vegetarian
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MINERAL TOLERANCE OF ANIMALS
diet will markedly reduce the apparent absorption of stron-
tium (Anke et al., 2000b). Although absorbed strontium is
excreted via the kidney, some apparently is excreted in the
bile. Schafer and Forth (1983) found that strontium is
excreted against a considerable concentration gradient from
blood into bile. Sweat also may be a significant route of
excretion of strontium (Consolazio et al., 1964).
Strontium is poorly retained by humans. In adults, net
retention is essentially zero, or a steady state exists
(Wasserman et al., 1977). The small amount of strontium
retained by the body is incorporated in bones and teeth.
Strontium incorporation occurs mainly by exchange with
calcium on bone crystal surfaces and is dependent upon the
amount ingested (Dahl et al., 2001). However, findings with
rats, monkeys, and humans indicate that the incorporation of
strontium in bone reaches a plateau during repeated oral ad-
ministration of high amounts as strontium ranelatae or stron-
tium chloride. Stopping the strontium administration results
in a rapid decrease in bone strontium content because that on
the crystal surface is rapidly eliminated (Dahl et al., 2001).
In new bone, only a few strontium atoms may be incorpo-
rated into the crystal by ionic substitution for calcium (Dahl
etal., 2001).
Metabolic Interactions and Mechanisms of Toxicity
Strontium has a low order of toxicity; it is less toxic than
calcium. Ineffectively substituting for calcium in physiologi-
cal processes apparently is the mechanism of strontium tox-
icity. Thus, actions that would promote this substitution
would exacerbate, whereas those that would inhibit the sub-
stitution would alleviate, strontium toxicity. For example,
when young or growing animals are fed high dietary stron-
tium in combination with low dietary calcium, they develop
a condition known as "strontium rickets" (Bartley and Reber,
1961;ColvinandCreger, 1967; Colvin etal., 1972). Ethanol
ingestion decreases bone strontium content and increases the
urinary excretion of strontium (Gonzalez-Reimers et al.,
1999), whereas low dietary protein increases bone strontium
content (Gonzalez-Riemers et al., 2002). Strontium absorp-
tion is decreased by dietary fiber (Momcilovic and Gruden,
1981) and vitamin D deprivation (Moon, 1994). There is
evidence for an antagonism between strontium and fluoride
(Liu and Min, 1999).
Toxicosis and Maximum Tolerable Levels
Extremely high oral doses of strontium relative to normal
intakes are needed to elicit toxic effects in animals and hu-
mans. Dosing adult monkeys with 100, 275, and 750 mg
strontium ranelate/day for six months had no deleterious
effects on bone formation (Buehler et al., 2001); it did
decrease indices of bone resorption, which was considered
advantageous in regards to being therapeutic for osteoporosis.
Findings from a study in which osteoporotic women were
supplemented with 0.5, 1, and 2 g of strontium ranelate/day
for 2 years indicated all doses were well tolerated (Meuneir
et al., 2002). The 2 g/d dose was considered to offer the best
combination of safety and efficacy against osteoporosis. Rats
given drinking water containing 0.19 percent SrClj exhib-
ited no adverse effects (Grynpas and Marie, 1990). How-
ever, 0.40 percent SrClj in drinking water induced bone
hypomineralization and inferior bone apatite crystals. Gen-
erally, toxic effects on bone cell or mineralization are not
seen in rats and mice fed diets containing less than 1 percent
(10,000 mg/kg) strontium (Marie et al., 2001). Based on cal-
culations from available literature, Marie et al. (2001) con-
sidered 350 mg/kg/day a low nontoxic dose of strontium.
Knight etal. (1967) found that feeding diets containing 2,000
mg Sr/kg for 100 days had no adverse effect on growth or
feed efficiency of growing beef cattle.
As indicated above, excessive strontium disturbs calcium
metabolism. Thus, the intake of strontium that induces signs
of toxicity is dependent upon calcium intake. In experiments
where pigs aged 3 weeks were fed diets containing 6,700 mg
Sr/kg for 5 weeks, only mild effects of weakness and incoor-
dination were seen when the diet contained 0.89 percent cal-
cium; when the diet contained only 0.16 percent calcium,
severe incoordination and weakness that occurred by the sec-
ond week progressed to complete paralysis by the end of the
third week (Bartley and Reber, 1961). Weber et al. (1968)
fed diets containing either 3,000 or 6,000 mg Sr/kg diet and
either 0.72 percent or 1 percent calcium to chicks for 4
weeks. No adverse effects were seen in chicks fed the diet
containing 3,000 mg Sr/kg. Feeding 6,000 mg Sr/kg diet
depressed growth and calcium retention more markedly in
chicks fed the lower calcium diet. Hens fed up to 30,000 mg
Sr/kg diet containing 2.9 percent calcium for 4 weeks exhib-
ited no adverse effects, but 50,000 mg Sr/kg diet reduced
egg weight and production and feed consumption (Doberenz
et al., 1969). In a study to determine the distinction between
pharmacological and toxic doses of strontium, rats were fed
diets containing 0, 0.05 percent, 0.10 percent, and 0.50 per-
cent strontium (about 0, 7.67, 15.3, and 76.67 mg Sr/day).
All calcium metabolic variables determined, including de-
creased calcium in bone and serum, were markedly de-
pressed by the 0.5 percent (5,000 mg/kg) strontium diet
(Morohashi et al., 1994). The calcium content of bone was
increased by the 0.05 percent (500 mg/kg) strontium diet.
The study indicated that diets containing less than 0.1 per-
cent strontium (providing about 15.3 mg Sr/day) do not have
a toxic effect on calcium metabolism in rats.
As indicated above, the maximum tolerable level for
strontium is affected by the intake of calcium. When dietary
calcium is adequate, animals have a high tolerance for stron-
tium. Mature animals can tolerate higher levels than young.
The findings above indicate that cattle and swine can toler-
ate 2,000 mg Sr/kg diet (0.2 percent), chicks can tolerate
3,000 mg Sr/kg (0.3 percent), and hens can tolerate 30,000
mg Sr/kg diet (3.0 percent) when dietary calcium is adequate.
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OTHER MINERALS
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These amounts are 100 to 1,000 times greater than those
normally found in animal diets. Thus, strontium is not a toxi-
cological concern for animals. Toxicological intakes of
strontium by animals and humans would only occur with
intentional dosing or supplementing with high amounts of
strontium salts.
Tissue Levels
More than 70 years ago, Gerlach and Muller (1934) re-
ported that the strontium concentrations in a wide variety of
animal tissues ranged from 0.01 to 0.10 mg/kg, with no evi-
dence of accumulation in any particular species, soft organ,
or tissue. Forty years later, Hamilton etal. (1972/1973) found
similar concentrations in human tissues; values included (in
mg/kg fresh tissue) kidney, 0.1 ± 0.02; hver, 0.1 ± 0.03; and
muscle, 0.05 ± 0.02. A biology data book (Altman and
Dittmer, 1973) has indicated that the concentration of stron-
tium in serum is 0.057 mg/L and that in blood is 0.033 mg/L.
TITANIUM
Titanium (Ti) is a dark, gray metal whose concentration
in the Earth's crust is estimated to be 0.43 percent. Titanium
forms compounds in which it has an oxidation state of +2,
+3, or +4. Titanium is used to make aluminum, tin, and va-
nadium alloys, and ferrotitanium for the steel industry. Tita-
nium oxide is used as a white pigment for paints. Titanium
compounds are constituents of glass and ceramics and used
as a mordant for the dyeing industry. Titanium metal is used
to make dental and orthopedic implants. Titanium dioxide is
used as a color additive in human and pet foods.
No essential metabolic function in animals has been iden-
tified for titanium. However, some biological interest has
been recently promoted by findings showing some physi-
ologically soluble titanium compounds have beneficial ac-
tions in animals and plants. Pais et al. (1977) synthesized
water-soluble Ti IV ascorbate (Ti-ascorbate, trade name
TITAVIT) by combining ascorbic acid with TiCl4 in the pres-
ence of gaseous HCl. Ti-ascorbate is stable up to pH 8 and
apparently is not toxic to living systems. Pais (1983) found
that Ti-ascorbate increased the yield of various crops. The
beneficial action is hypothesized to be the result of titanium
promoting better utilization of magnesium and iron in pho-
tosynthetic activity (Carvajal and Alcaraz, 1998). Ti-ascor-
bate supplementataion (30-60 mg Ti/kg diet) improved re-
production in pigs (Pais et al., 1989) and increased egg
production, weight, and shell hardness of laying hens
(Halmagyi-Valter et al., 1988). Schroeder et al. (1963)found
that potassium titanium oxalate increased growth of mice.
Yaghoubi et al. (2000) also reported that the titanyl ion
(TiO'"*") in the form of titanyl oxalate enhanced the growth of
mice. It was hypothesized that titanium was acting as an an-
tibacterial and/or antiviral agent (Yaghoubi et al., 2000;
Schwietert et al., 2001).
Sources and Metabolism
Most titanium consumed by domestic animals probably
comes from soil contamination; soil concentrations are about
10,000 times greater than those in uncontaminated herbage
(Swaine, 1955). The titanium concentrations in a variety of
plants were determined by Bertrand and Varonca-Spirt
(1929a,b). The concentrations ranged from 0.1 to 5 mg/kg
DW with a majority near 1 mg/kg. Mitchell (1957) found
similar concentrations in red clover (mean 1 .8 and range 0.7-
3.8 mg/kg DW) and in ryegrass (mean 2 and range 0.9-4.6
mg/kg DW) grown on different soils. A brief summary of
titanium concentrations of human foods indicates that they
range from 0.2 to 6 mg/kg DW (Nielsen, 1986); exceptions
are taro (80 mg/kg) and yam (15 mg/kg). English total diets
were found to provide about 800 |Jg/day (Hamilton and
Minski, 1972/1973).
Very little is known about the metabolism of titanium. It
is generally believed that most titanium, especially that from
soil contamination, is poorly absorbed. Titanium that is ab-
sorbed is not extensively retained by either plants or ani-
mals. However, if dietary titanium is in a soluble form in the
gastrointestinal tract, it apparently is absorbed to some ex-
tent. Evidence for this is that Tipton et al. (1966) found about
equal amounts of titanium in feces and urine of individuals
consuming an average 0.37 and 0.41 mg titanium per day for
a month in their diet. Also, after the administration of titanyl
ion (TiO-"^), the ion is found in breast milk (Schwietert et al.,
2001).
Metabolic Interactions and Mechanisms of Toxicity
It is questionable whether a specific toxicity of titanium
has been demonstrated. Thus, no mechanism of toxicity can
be described. As mentioned above, titanium is thought to
have beneficial effects in plants through promoting magne-
sium and iron metabolism.
Toxicosis and Maximum Tolerable Levels
Titanium is essentially nontoxic in the amounts and forms
that usually are ingested. Thus, no specific oral toxicity of
titanium has been described and a maximum tolerable limit
cannot be suggested for any domestic animal.
Tissue Levels
The reported concentrations of human and animal tissues
are variable, with high amounts commonly found in lungs,
probably as a result of dust inhalation. Most reported values
for human tissues are between 0.2 and 1.4 mg/kg fresh tissue.
Hamilton et al. (1972/1973) reported the following mean
values in mg/kg fresh tissue for human organs: muscle, 0.2 ±
0.01; kidney cortex, 1.3 ± 0.2; kidney medulla, 1.2 ± 0.2;
liver, 1.3 ± 0.2; brain, 0.8 ± 0.05; and lung, 3.7 ± 0.9.
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MINERAL TOLERANCE OF ANIMALS
Schroeder et al. (1964) found that the titanium concentra-
tions in a variety of mouse organs were increased from 0.13-
1.10 to 1.66-8.80 mg/kg fresh tissue when dietary (water
and food) titanium was increased from 0.03 to 5.03 mg/kg.
TUNGSTEN
Tungsten (W) is a whitish-gray metal used in a wide vari-
ety of commercial, industrial, and military applications
(Shedd, 2002). The largest use is as tungsten carbide in ce-
mented carbides, which are wear-resistant materials used by
the metalworking, mining, and construction industries.
Tungsten alloys are used to make armaments, tool steels,
and wear-resistant materials and coatings, and as a substitute
for lead in bullets and shot. Tungsten metal wires, electrodes,
and contacts are used in lighting, electronic, electrical, heat-
ing, and welding applications. Tungsten chemicals are used
to make catalysts, inorganic pigments, high-temperature lu-
bricants, and semiconductors. Tungsten is one of the rarer
elements in the Earth's crust; it occurs in concentrations that
average 5 mg/kg (Standen, 1970).
Biological interest in tungsten developed when De Renzo
(1954) found that it was antagonistic to molybdenum me-
tabolism. Recently, biological interest has centered on its
enzymatic functions and pharmacological antidiabetic ac-
tion. More than a dozen tungstoenzymes in three function-
ally and phylogenetically distinct families have been identi-
fied and characterized in lower forms of life (Roy and
Adams, 2002). All known tungstoenzymes catalyze reactions
involving oxygen atom transfer and coupled electron proton
transfer, similar to reactions catalyzed by molybdoenzymes
(Roy and Adams, 2002). Both sodium tungstate (Barbera et
al., 2001) and ammonium paratungstate (Palanivel et al.,
2001) have antidiabetic action in strep tozotocin-induced dia-
betes in rats. However, sodium tungstate only transiently al-
leviated the streptozotocin-nicotinamide rat model of diabe-
tes that shares several features with human type 2 diabetes
(Fierabracci et al., 2002). Although attempts have been
made, no findings have been obtained that suggest tungsten
is essential for animals and humans. After comparing in-
takes of 60 vs. 1,000 |Jg W/kg diet in six experiments with
goats, Anke et al. (1983a) stated that their findings indicated
that tungsten is either not essential for or that 60 |Jg W/kg
diet meets the requirement of higher animals.
Sources and Metabolism
Anke et al. (1983b) found that normal feedstuffs of rumi-
nants contained average tungsten concentrations between
118 and 478 |Jg/kg dry weight.
The metabolism of tungsten has been recently reviewed by
Lagarde and Leroy (2002). Their review disclosed that a rela-
tively high percentage of tungsten is rapidly absorbed after
being ingested by a variety of animals. Beagle dogs absorbed
57-74 percent of tungsten from a solution containing 25 or 50
mg sodium tungstate/kg; absorption was 25 percent from a
weakly acidic aqueous solution of tungstic oxide. Rats gave
similar results, absorbing 40-92 percent of tungsten adminis-
tered as tungstate, but only 1 percent as tungstic acid. Dairy
cows absorbed 25 percent of a dose of '^'W-labeled tungstate.
Swine absorb at least 75 percent and sheep absorb 44-65 per-
cent of orally administered tungsten as tungstate. Urine appar-
ently is the major excretory pathway for absorbed tungsten.
The major site of long-term retention of tungsten is bone, with
retention greater in growing rather than mature bone. Gener-
ally, kidney and liver are the soft tissues that are highest in
tungsten. Lagarde and Leroy (2002) suggested that the liver
retention of tungsten may be explained by its ability to replace
molybdenum in molybdoenzymes.
Metabolic Interactions and Mechanisms of Toxicity
Tungsten and molybdenum have almost identical atomic
and ionic radii and similar chemical properties. Thus, it is
not surprising that studies with chickens, rats, goats, and
cows have shown that tungsten is an antagonist of molybde-
num (Lagarde and Leroy, 2002). High dietary tungsten de-
creased the activity of sulfite and xanthine oxidase (two liver
molybdenum enzymes) and the concentration of molybde-
num in liver. Lagarde and Leroy (2002) suggested that the
most likely mode of action of tungsten was that it replaced
molybdenum in enzymes. However, they indicated other
modes of action were possible. These actions included tung-
sten preventing the incorporation of molybdenum in en-
zymes without itself being incorporated, and inhibiting the
transport of sulfate, molybdate, sulfite, and thiosulfate in the
gut. Like molybdenum, tungsten can replace phosphate in
bone and, in rats, induce signs of copper deficiency, includ-
ing causing a progressive decline in ceruloplasmin oxidase
activity (Lagarde and Leroy, 2002).
Toxicosis and Maximum Tolerable Levels
Toxicological studies on laboratory animals indicate that
tungsten has a relatively low order of toxicity. Schroeder
and Mitchener (1975) did not observe any adverse effects in
rats given drinking water containing 5 mg W/L as sodium
tungstate for a lifetime. Kinard and Van de Erve (1941)
found that 1,000 mg W/kg diet as tungstic oxide, sodium
tungstate, and ammonium paratungstate fed to rats for 70
days slightly depressed growth. However, much higher doses
(5,000 mg W/kg diet or greater for tungstic oxide and so-
dium tungstate, 20,000-50,000 mg W/kg diet for ammonium
paratungstate) produced extensive mortality. Karantassis
(1924) found that the acute lethal oral dose for guinea pigs
was 550 mg tungstate; the guinea pigs exhibited anorexia,
colic, disorganized movements, trembling, and dyspnea.
Toxicological studies of tungsten in domestic animals are
few. Owen and Proudfoot (1968) found that 37.5 mg/kg BW
administered in 2 or 3 separate doses as sodium tungstate
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OTHER MINERALS
441
over a period of 3 weeks had no adverse effects on milk
production but markedly decreased milk xanthine oxidase
activity. Similar effects were found with goats administered
56 mg tungsten as 2 separate doses of sodium tungstate.
Higgens et al. ( 1956a,b) found that feeding 45 and 94 mg W/
kg diet (low molybdenum) as sodium tungstate for 35 days
decreased the growth rate and increased the death rate in 1-
day-old chicks. These adverse effects of tungsten were com-
pletely reversed by increasing the molybdenum content of
the diet. Older chickens may be less sensitive to tungsten
toxicity. Feeding 250 or 500 mg W/kg diet as sodium tung-
state for 30 days had no adverse effects on egg production
and hatchability of breeder chickens, but 500 mg W/kg diet
did decrease xanthine oxidase activity in tissues (Teekell and
Watts, 1959). The form of tungsten also affects its toxicity.
Mitchell et al. (2001a,b) found that eight #4 tungsten-iron
shot, or #4 tungsten-polymer shot administered orally on
days 0, 30, 60, 90, and 120 of a 150-day trial had no adverse
effects on mortality, body weights, organ weights, liver and
kidney histology, or reproduction.
The chicken studies of Higgens et al. (1956a,b) indicate
that maximum tolerable level of tungsten is quite dependent
upon the molybdenum content of the diet. However, the life-
time rat study of Schroeder and Mitchener (1975) suggests
that 5 mg W/L of water is a tolerable intake. If one accepts
that a slight decrease in tissue and milk xanthine oxidase is
not of toxicological concern, the recommendation in the pre-
vious edition of this document (NRC, 1980b) of 20 mg/kg
diet may be appropriate.
Tissue Levels
There is a lack of information about the normal amount of
tungsten in animal tissue. Kinard and Aull (1944) found that
after 100 days of consuming a diet containing 1,000 mg W/kg
as tungstic oxide, sodium tungstate, or ammonium
paratungstate, appreciable amounts of tungsten accumulated
in the bone, skin, and spleen (20-120 mg/kg fresh weight).
All other tissues contained trace quantities (i.e., less than 10
mg/kg).
URANIUM
Metallic uranium (U) is a silver-white, lustrous, dense,
and weakly radioactive material. The average concentration
of uranium in the Earth's crust is about 3 mg/kg (Anke et al.,
2000a). Uranium does not occur in concentrated deposits,
and much of the ore from which it is extracted contains less
than 0.1 percent uranium. Uranium occurs in both North
Carolina and Florida marine sedimentary phosphate minerals
and in igneous phosphate minerals from western U.S. states
in concentrations up to 250 mg/kg. Depleted uranium is a
by-product of the --^^U radionuclide enrichment process in
making fuel for nuclear reactors. Depleted uranium contains
approximately 40 percent of the radioactivity and retains all
the chemical properties of natural uranium (Sztajnkrycer and
Otten, 2004). Depleted uranium has military uses (WHO,
2003) because its high density, hardness, and pyrophoric
properties (it ignites on impact if the temperature exceeds
600°C) make it superior to classical tungsten in armor-
piercing munitions. Because of its high density, depleted
uranium is used as counterweights in aircraft and in radia-
tion shielding applications. Military use of depleted uranium
has recently become of biological concern because of
possible hazards arising from its radioactivity and chemical
toxicity. There is no evidence that uranium has an essential
or a beneficial metabolic function in animals.
Sources and Metabolism
Very little has been reported about the uranium content of
animal feedstuffs and diets. Bowen (1966) indicated that
most plants contain less than 0.04 mg/kg. The low uranium
content in plants used as animal feeds was confirmed by
Anke et al. (2000a) who found concentrations between 0.8
and 15 mg U/kg dry weight in lucerne, wheat, rape, red clo-
ver and white clover, and means of 0.58 and 0.71 mg/kg dry
weight in wheat grain and rape seed, respectively. The ura-
nium concentration in corresponding plant material from a
uranium mining area was several times higher and the ura-
nium concentration in plants decreased as they matured.
Because of the high concentrations found in some phosphate
deposits, commercial feed grade phosphate supplements may
be a major contributor to the uranium intake by domestic
animals. The uranium concentrations in commercial feed
grade phosphates containing about 18 percent phosphorus
range from 70 to 180 mg/kg (Reid and Sackett, 1977). It was
calculated that such supplements would provide 0.7 to 1.8
mg U/kg diet for farm livestock (NRC, 1980c). Drinking
water also may be a major source of uranium for domestic
animals. One study of drinking water from drilled wells
found a median concentration of 28|Jg U/L with an inter-
quartile range of 6-1 35 [ig and a maximum concentration of
1,920 |Jg/L (Kurttio et al., 2002). However, Anke et al.
(2000a) found that drinking water in Germany ranged from
0.28 to 2.4 |ig/L; some mineral waters were high in uranium,
up to 24.5 |Jg/L. The higher concentrations in drinking water
indicate that higher intakes are possible for adult humans
than the average intake of 500 pg/year (less than 1 .5 |ig/day)
through the ingestion of food and water estimated by the
World Health Organization (2003). Anke et al. (2000a)
reported that the average intake of people in Germany was
2.7 |ig/day.
Typical gut absorption by humans of uranium from food
and water is about 2 percent for soluble and about 0.2 per-
cent for insoluble uranium compounds. After reviewing and
analyzing the literature, Wrenn et al. (1985) concluded that
the average gastrointestinal absorption of ingested uranium
is 1-2 percent, and reasonably independent of age and
amount of uranium ingested. Anke et al. (2000) provided
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MINERAL TOLERANCE OF ANIMALS
evidence suggesting that absorption of uranium from thie diet
was about 6 percent. Absorbed uranium is excreted mainly
in tiie urine. Uranium does not accumulate to any extent in
the body. The small amount retained is found mostly in the
skeleton, liver, and kidneys (WHO, 2003).
Metabolic Interactions and Mechanisms of Toxicity
Oral administration of a biphosphonate (ethane- 1 -hy-
droxy- 1,1 -biphosphonate, EHBP) reduced the lethality and
kidney histopathology induced by a single orally adminis-
tered toxic dose of uranyl nitrate (350 mg/kg BW) (Martinez
et al., 2000). There is some evidence suggesting that
inorganic mercury can enhance the nephrotoxicity of ura-
nium (Sanchez et al., 2001).
By the late 1950s the mechanism of uranium toxicity in
the kidney was thought to be the binding of uranium to the
luminal membranes of renal tubular cells, which interfered
with the reabsorption of critical substances for cell respira-
tion and resulted in slow cell death (Leggett, 1989). Bone
formation depression caused by uranium toxicity was also
suggested to be caused by the binding of uranium to cell
membranes resulting in damage to osteoblasts (Ubios et al.,
1991).
Toxicosis and Maximum Tolerable Levels
Early studies of uranium toxicity suggested that it is not
very toxic. Mice fed uranyl nitrate hexahydrate in amounts
ranging from 2 to 2,370 mg/kg diet for 48 weeks exhibited
no signs of toxicity except for a decrease in growth at the
highest concentration (Tannenbaum and Silverstone, 1944).
When mice were fed 1 percent uranyl nitrate hexahydrate
(4,740 mg/kg) in the diet, after a few days they ate less food,
failed to grow or lost weight, were cold to the touch, and had
ruffled fur and arched backs. When necropsied during the
second or third week, the kidneys were enlarged, pink-gray,
and exhibited an acute necrotizing nephrosis (Tannenbaum
and Silverstone, 1944). Some animals died but those that
survived recovered with normal or near-normal growth rates
and a return of normal size and appearance of the kidney;
these findings suggest that animals can acquire a tolerance to
uranium. Hodge (1953) fed rats diets containing 474, 2,370
or 9,480 mg U/kg as uranyl nitrate hexahydrate. Rats fed
474 mg U/kg diet did not differ from controls. At 2,370 mg
U/kg diet a slight growth depression was observed. How-
ever, rats fed diets containing 9,480 mg U/kg diet had mark-
edly reduced growth and a high mortality. The body weights
of dogs fed 100 mg uranyl nitrate hexahydrate/kg BW/day
were not affected, but kidneys had characteristic histological
changes associated with uranium toxicity when the dogs
were fed diets providing as low as 20 mg/kg BW/day
(Hodge, 1953). More recent studies indicate that much lower
amounts of ingested uranium are toxic to experimental ani-
mals. Oilman et al. (1998a) found that 0.96 mg uranyl nitrate
hexahydrate/L of drinking water produced renal lesions in
rats. The histopathological lesions included apical nuclear
displacement and vesiculation, cytoplasmic vacuolation, and
dilation of the tubules; capsular sclerosis of the glomeruli;
and reticulin sclerosis and lymphoid cuffing of the intersti-
tium. Oilman et al. (1998b) also provided 0.96, 4.8, 24, 120,
or 600 mg uranyl nitrate/L drinking water to rabbits. Based
on changes in renal tubules, they concluded that the LOAEL
in males was 0.96 mg U/L for male rabbits, and 4.8 mg U/L
for female rabbits. Dose- and duration-dependent histo-
pathologies were found in the liver and kidney of lake white-
fish fed for 10, 30, and 100 days a commercial diet contami-
nated with 100, 1,000, and 10,000 mg U/kg (Cooley et al.,
2000). Lesions in the liver were focal hepatocyte necrosis
and alterations in the bile ductule epithelium. Lesions in the
kidney included tubular necrosis, inflaimnation, hemorrhaging,
depletion of hematopoietic tissues, alterations of distal
tubules and collecting ducts, tubule dilation, pigmented mac-
rophage proliferation, and glomerular lesions. The toxicity
of uranium in water for several tropical freshwater fish was
determined by Bywater et al. (1991). The 96-hour LCjq (in
mg/L) were 1.7 and 1.9 for 7- and 90-day-old black banded
rainbow fish, 1.22 for Mariana's hardyhead, 0.73 for deli-
cate blue-eyes, 0.8 for reticulated perchlet, and 1.11 and 1.46
for 7- and 90-day-old purple-spotted gudgeon.
Recent studies with mice showed that oral uranium at
relatively low doses is a reproductive, maternal, and devel-
opmental toxicant (Domingo et al., 1989; Domingo, 2001).
The NOAEL for maternal and fetal toxicity was found to be
below 5 mg/kg BW/day when uranyl acetate dihydrate was
gavaged to mice on gestation days 6 to 15 at 0, 5, 10, and 25
mg/kg/day. Male reproduction variables were not as sensi-
tive. Testicular function/spermatogenesis was not affected
by doses of uranyl acetate dihydrate as high as 80 mg/kg
BW/day given in drinking water for 64 days (Llobet et al.,
1991). However, at 80 mg/kg/day interstitial alterations and
vacuolization of Leydig cells were seen.
Based on acute toxicity studies with purple-spotted gud-
geon and chequered rainbow fish, Holdway (1992) calcu-
lated the threshold value of 200 |Jg/L water for uranium tox-
icity using growth as the most sensitive response. He
suggested that 70 |Jg U/L would be a safe uranium exposure
for fish, based on the lower 95 percent fiducial limit of the
lowest lethal concentration. Kurtitio et al. (2002) concluded
that the safe concentration of uranium in drinking water for
humans may be within the range of 2-30 |-ig/L. The WHO
(2003) concluded that a tolerable intake of uranium (based
on its chemical toxicity) from insoluble uranium compounds
with a very low absorption rate may be 5 |Jg/kg BW/day
(about 300-350 pg/day). When solubility characteristics of
uranium compounds are unknown, it would be prudent to
apply a tolerable intake of 0.5 |Jg/kg BW/day (about 30-35
fig/day) for ingestion. Because there is no information about
the toxicity of uranium in domestic animals, it is difficult to
suggest a maximum tolerable level. However, it should be
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below 568 |Jg/L because 960 |Jg uranyl nitrate hexahydrate/
L water caused renal histopathology in rats and male rabbits
(Oilman et al., 1998a,b). Hodge (1953) found that an oral
intake of 474 mg U/kg diet was not toxic to rats, and
Tannenbaum and Silverstone (1944) found no adverse
effects of 237 mg/kg diet in mice; however, renal histo-
pathology was not an endpoint in these studies. The fish
study of Cooley et al. (2000) indicates that the maximum
tolerable limit for fish is less than 100 mg/kg diet. Thus a
maximum tolerable intake for domestic animals is probably
between 100 and 400 mg/kg diet. This intake indicates that
uranium toxicity is not a concern for domestic animals
because most diets probably do not exceed 3-4 mg/kg.
Tissue Levels
On average, the human adult body contains about 90 pg of
uranium with 66 percent in the skeleton, 16 percent in liver, 8
percent in kidneys, and 10 percent in other tissues (WHO,
2003). This indicates that most tissue uranium concentrations
in animals would be quite low. Low tissue uranium concentra-
tions were confirmed by the human food analyses of Anke et
al. (2000a). They found uranium concentrations (in pg/kg fresh
weight) of 4.1 for chicken eggs, 2.1 for cattle kidney, 1.5 for
trout and herring fillets, 1 for mutton, 0.8 for beef muscle, 0.4
for pork muscle, and 0.2 for milk.
REFERENCES
Altman,P.L., andD. S.Dittmer, eds. 1973. Pp. 1751-1752 in Biology Data
Book, Vol. 3. Bethesda, MD: Fed. Am. Soc. Exp. Biol.
Anise, M., and L. Angelow. 1995. Rubidium in tlie food chain. Frensenius J.
Anal. Chem. 352:236-239.
Anlce, M., B. Groppel, M. Griin, andH. lironemann. 1983a. Die biologische
Bedeutung des Wolframs ftir due Fauna. 1. Der Einfluss einer
wolframarmen Ernahrung auf das Waclistum. Pp. 37^4 in Mengen-
und Spurenelemente, M. Anife, C. Bruckner, H. Gtirtler, and M. Grtin,
eds. Leipzig: Karl-Marx-tJniversitaet.
Anke, M., H. Kronemann. B. Groppel, M. Parschefeld. 1983b. Die
biologische Bedeutung des Wolframs ftir die Fauna. 2. Der Einfluss
einer wolframarmen Ernahrung auf die Fortpflanzungsleistung und
Lebenserwartung. Pp. 45—51 in Mengen- und Spurenelemente, M. Anke,
C. Bruckner, H. Gurtler, and M. Griin, eds. Liepzig: Karl-Marx-
Universitaet.
Anke, M., W. Arnhold, B. Groppel, and U. ICrause. 1991. The biological
importance of lithium. Pp. 148—167 in Lithium in Biology and Medicine,
G. N. Schrauzer and K. F. Klippel, eds. Weinheim: VCH Publishers.
Anke, M., L. Angelow, A. Schmidt, and H. Gurtler. 1993. Rubidium: an
essential element for animal and man? Pp. 719-723 in Trace Elements
in Man and Animals — TEMA 8, M. Anke, D. Meissner, and C. F. Mills,
eds. Gersdorf: Verlag Media Touristik.
Anke, M., W. Arnhold, M. Mtiller, H. Illing, U. Schafer, and M. Jaritz.
1997. Lithium. Pp. 465^77 in Handbook of Nutritionally Essential
Mineral Elements, B. L. O'Dell, and R. A. Sunde, eds. New York:
Marcel Dekker.
Anke, M., O. Seeber, M. Glei, W. Dorn, and R. Mtiller. 2000a. Uranium
in the food chain of humans in Central Europe — risks and problems.
Pp. 7-22 in Metal Elements in Environment, Medicine and Biology,
Vol. 4, Z. Garban, and P. Draegan, eds. Timisoara: Publishing House
"Eurobit".
Anke, M., M. Seifert, M. Jaritz, E. Losch, and E. Hartmann. 2000b. Stron-
tium transfer in the food chain of humans. Pp. 229—230 in Trace Ele-
ments in Man and Animals 10, A. M. Roussel, R. A. Anderson, and A.
E. Favrier, eds. New York: Kluwer Academic/Plenum Publishers.
Bailly, R., R. Lauweiys, J. P. Buchet, P. Mahieu, and J. Konings. 1991.
Experimental and human studies on antimony metabolism: their rel-
evance for the biological monitoring of workers exposed to inorganic
antimony. Br. J. Indust. Med. 48:93-97.
Barbera, A., R. R. Gomis, N. Prats, J. E. Rodriguez-Gil, M. Domingo, R.
Gomis, and J. J. Guinovart. 2001. Tungstate is an effective antidiabetic
agent in streptozotocin-induced diabetic rats: a long-term study.
Diabetologia 44:507-513.
Bartley, J. C. and E. F. Reber. 1961. Toxic effects of stable strontium in
young pigs. J. Nutr. 75:21-28.
Becker, R. R., A. Veglia, and E. R. Schmid. 1975. Bestimmung von
Spurenelementen mittels instrumenteller Neutronenaktivierungsanalyse.
1. Mitteillung: Spurenelementgehalt von handelsiiblichen oster-
reichischen Futtermitteln. Wien. Tieraerztl. Monatsschr. 65:47-51.
Benes, B., K. Jakubec, J. Smi'd and V. Spevackova. 2000. Determination of
thirty-two elements in human autopsy tissue. Biol. Trace Elem. Res.
75:195-203.
Bertrand, G., and C. Varonca-Spirt. 1929a. Le titane dans les plantes
phanerogames. C. R. Hebd. Seances Acad. Sci. 188:1199-1202.
Bertrand, G., and C. Varonca-Spirt. 1929b. Le titane dans les plantes cryp-
togams. C. R. Hebd. Seances Acad. Sci. 189:73.
Birch. N. J. 1995. Lithium in medicine. Pp. 1274-1281 in Handbook of
Metal-Ligand Interactions in Biological Fluids. Bioinorganic Medicine,
Vol. 2, G. Berthon, ed. New York: Marcel Dekker.
Birch, N. J., C. Padghom, and M. S. Hughes. 1994. Lithium. Pp. 441^50 in
Handbook on Metals in Clinical and Analytical Chemistry. H. G. Seller,
A. Sigel, and H. Sigel, eds. New York: Marcel Dekker.
Bradley, W. R., and W. G. Fredrick. 1941. The toxicity of antimony —
animal studies. Ind. Med. 2:15-22.
Brauner, C. J., and C. M. Wood. 2002. lonoregulatory development and the
effect of chronic silver exposure on growth, survival, and sublethal indi-
cators of toxicity in early life stages of rainbow trout (Oncorhynchus
mykiss). J. Comp. Physiol. B: Biochem, System. Environ. Physiol.
172:153-162.
Bowen, H. J. M. 1966. Trace Elements in Biochemistry. New York: Aca-
demic Press.
Buehler, J., P. Chappuis, J. L. Saffar, Y. Tsouderos, and A. Vignery. 2001.
Strontium ranelate inhibits bone resorption while maintaining bone for-
mation in alveolar bone in monkeys {Macaca fascicularis). Bone
29:176-179.
Bunyan, J., A. T. Diplock, M. A. Cawthorne, and J. Green. 1968. Vitamin E
and stress. 8. Nutritional effects of dietary stress with silver in vitamin
E-deficient chicks and rats. Br. J. Nutr. 22:165-182.
Bywater, J. F., R. Banaczkowski, and M. Bailey. 1991. Sensitivity to ura-
nium of six species of tropical freshwater fishes and four species of
cladocerans from Northern Australia. Environ. Toxicol. Chem.
10:1449-1458.
Carvajal, M., and C. F. Alcaraz. 1998. Why titanium is a beneficial element
for plants. J. Plant Nutr. 21:655-664.
Chase, T. A., M. J. Cupp, and T. S. Tracy. 2003. Germanium. Pp. 197-207
in Forensic Science: Dietary Supplements: Toxicology and Clinical
Pharmacology, M. J. Cupp and T. S. Tracy, eds. Totowa, NJ: Humana
Press.
Chen, W. J., Y. Tao, Y. H. Gu, and G. W. Zhao. 2001. Effect of lanthanide
chloride on photosynthesis and dry matter accumulation in tobacco seed-
lings. Biol. Trace Elem. Res. 79:169-176.
Clemente, G. F., L. Cigna Rossi, and G. P. Santaroni. 1978. Studies on the
distribution and related health effects of the trace elements in Italy. Pp.
23-30 in Trace Substances in Environmental HeaIth-12, D. D. Hemphill,
ed. Columbia: University of Missouri Press.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
444
MINERAL TOLERANCE OF ANIMALS
Comar, C. L., andR. H. Wasserman. 1964. Strontium. Pp. 533-572 in Min-
eral Metabolism, vol. 2, C. L. Comar and F. Bronner, eds. New York:
Academic Press.
Consolazio, C. F., R. A. Nelson, L. O. Matoush, R. C. Hughes, and P.
Urone. 1964. The trace mineral losses in sweat. U.S. Army Med. Res. &
Nutr. Lab. Report 283:1.
Cooley, H. M., R. E. Evans, and J. F. Klaverkamp. 2000. Toxicology of
dietary uranium in lake whitefish (Coregonous clupeaformis). Aquatic
Toxicol. 48:495-515.
Colvin, L. B., and C. R. Creger. 1967. Stable strontium and experimental
bone anomalies. Fed. Proc. 26:416.
Colvin, L. B., C. R. Creger, T. M. Ferguson, and H. R. Crookshank. 1972.
Experimental epiphyseal cartilage anomalies by dietary strontium.
Poult. Sci. 51:576-581.
Croft, S. L., and V. Yardley. 2002. Chemotherapy of leishmaniasis. Curr.
Pharm. Design 8:319-342.
Dahl, S. G., P. AUain, P. J. Marie, Y. Mauras, G. Boivin, P. Ammann, Y.
Tsouderos, P. D. Delmas, and C. Christiansen. 2001. Incorporation and
distribution of strontium in bone. Bone 28:446^53.
Dam, H., C. K. Nielsen, 1. Prange, and E. Sondergaard. 1958. Influence of
linoleic and linolenic acids on symptoms of vitamin E deficiency in
chicks. Nature (London) 182:802-803.
De Renzo, E. C. 1954. Studies on the nature of the xanthine oxidase factor.
Ann. N. Y. Acad. Sci. 57:905-908.
Dieter, M. P., C. W. Jameson, M. R. Elwell, J. W. Lodge, M. Hejtmancik, S. L.
Grumbein, M. Ryan, and A. C. Peters. 1991. Comparative toxicity and tissue
distribution of antimony potassium tartrate in rats and mice dosed by drinking
water or intraperitoneal injection. J. Toxicol. Environ. Health 34:51-82.
Dijkstra, M., R. Havinga, R. J. Vonk, and F. Kuipers. 1996. Bile secretion
of cadmium, silver, zinc and copper in the rat. Involvement of various
transport systems. Life Sci. 59:1237-1246.
Diplock, A. T., J. Green, J. Bunyan, D. McHale, and 1. R. Murthy. 1967.
Vitamin E and stress. 3. The metabolism of D-a-tocopherol in the rat
under dietary stress with silver. Br. J. Nutr. 21:115—125.
Doberenz, A. R., C. W. Weber, and B. L. Reid. 1969. Effect of high dietary
strontium levels on bone and egg shell calcium and strontium. Calcif.
Tissue Res. 4:180-184.
Domingo, J. L. 2001. Reproductive and developmental toxicity of natural
and depleted uranium: a review. Reprod. Toxicol. 15:603-609.
Domingo, J. L., J. L. Paternain, J. M. Llobet, and J. Corbella. 1989. The
developmental toxicity of uranium in mice. Toxicology 55:143—152.
Dunn, J. T. 1928. A curious case of antimony poisoning. Analyst 53:532-533.
Enyeart, J. J., L. Xu, and J. A. Enyeart. 2002. Dual actions of lanthanides on
ACTH-inhibited leak K* channels. Am. J. Physiol. Endocrinol. Metab.
282:E1255-E1266.
Fairweather-Tait, S. J., A. M. Minihane, J. Eagles, L. Owen, and H. M.
Crews. 1997. Can rare earth elements be used as non-absorbable fecal
markers in studies of iron absorption? Pp. 270-272 in Ninth Interna-
tional Symposium on Trace Elements in Man and Animals, P. W. F.
Fischer, M. R. L'Abbe. K. A. Cockell, and R. S. Gibson, eds. Ottawa:
NRC Research Press.
Fashui, H., W. Ling, M. Xiangxuan, W. Zheng, and Z. Guiwen. 2002. The
effect of cerium (111) on the chlorophyll formation in spinach. Biol.
Trace Elem. Res. 89:263-276.
Favaro, D. 1., M. L. Hui, S. M. Cozzohno, V. A. Maihara, M. J. Armelin, M.
B. Vasconcellos, L. K. Yuyama, G. T. Boaventura, and V. L. Tramonte.
1 997. Determination of various nutrients and toxic elements in different
Brazilian regional diets by neutron activation analysis. J. Trace Elem.
Med. Biol. 11:129-136.
Felicetti, S. A., R. G. Thomas, and R. O. McClellan. 1974. Metabolism of
two valence states of inhaled antimony in hamsters. Am. Ind. Hyg.
Assoc. J. 35:292-300.
Fierabracci, V., V. De Tata, A. Pocai, M. Novelli, A. Barbera, and P.
Masiello. 2002. Oral tungstate treatment improves only transiently al-
teration of glucose metabolism in a new rat model of type 2 diabetes.
Endocrine 19:177-184.
FoUis, R. H. 1943. Histological effects in rats resulting from adding ru-
bidium or cesium to a diet deficient in potassium. Am. J. Physiol.
138:246-250
Fujimori, E., Y. Tomosue, and H. Haraguchi. 1996. Determination of rare
earth elements in blood serum reference sample by chelating resin
preconcentration and inductively coupled plasma mass spectrometry.
Tohoku J. Exp. Med. 178:63-74.
Furr, A. K., T. F. Parkinson. C. A. Bache, W. H. Gutenmann, 1. S. Pakkala,
G. S. Stoewsand, and D. J. Lisk. 1979. Multi-element analysis of fruit
kernels. Nutr. Rep. Int. 20:841-844.
Furst, A. 1987. Biological testing of germanium. Toxicol. Indust. Health
3:167-204.
Galvez, F., C. Hogstrand, J. C. McGeer, and C. M. Wood. 2001. The physi-
ological effects of a biologically incorporated silver diet on rainbow
trout (Oncorhynchus mykiss). Aquatic Toxicol. 55:95-1 12.
Gebel, T. 1998. Suppression of arsenic-induced chromosome mutagenicity
by antimony in V79 cells. Mutat. Res. 412:213-218.
Geisler, A., and A. Mork. 1990. The interaction of lithium with magne-
sium-dependent enzymes. Pp. 125-136 in Lithium and Cell Physiol-
ogy. R. O. Bach and V. S. Gallicchio, eds. New York: Springer-
Verlag.
Gerlach, W., and R. Muller. 1934. The occun'ence of strontium and barium
in human organs and excreta. Virchows Arch. Pathol. Anat. Physiol.
294:210-212.
Oilman, A. P., D. C. Villeneuve, V. E. Secours, A. P. Yagminas, B. L.
Tracy, J. M. Quinn, V. E. Valh, R. J. Willes, and M. A. Moss. 1998a.
Uranyl nitrate: 28-day and 91 -day toxicity studies in the Sprague-
Dawley rat. Toxiocol. Sci. 41:117-128.
Oilman, A. P., D. C. Villeneuve, V. E. Secours, A. P. Yagminas, B. L.
Tracy, J. M. Quinn, V. E. Valh, and M. A. Moss. 1998b. Uranyl nitrate;
91-day toxicity studies in the New Zealand white rabbit. Toxicol. Sci.
41:129-137.
Glendening, B. L., W. G. Schrenk, and D. B. Parrish. 1956. Effects of ru-
bidium in purified diets fed rats. J. Nutr. 60:563-579.
Gonzalez-Reimers, E., F. Rodriguez-Moreno, A. Martinez-Riera, A.
Mas-Pascual, E. Delgado-Ureta, L. Galindo-Martin, M. Arnay-de la
Rosa, and F. Santolaria-Fernandez. 1999. Relative and combined
effects of ethanol and protein deficiency on strontium and barium
bone content and fecal and urinary excretion. Biol. Trace Elem. Res.
68:41-49.
Gonzalez-Reimers, E., M. Arnay-de-la-Rosa, J. Velasco- Vazquez, R.
Aleman-Vallis, M.C. Duran-Castellon, M. J. de la Vega-Prieto, L.
Galindo-Martin, and F. Santolaria-Fernandez. 2002. Effects of ethanol
and low-protein diet on bone strontium and its relation with divalent
ions metabolism. Trace Elem. Electrolytes 19:165—168.
Grynpas, M. D., and P. J. Marie. 1990. Effects of low doses of strontium on
bone quality and quantity in rats. Bone 1 1 :313-319.
Gulbranson, S. H., J. A. Hud, and R. C. Hansen. 2000. Argyria following
the use of dietary supplements containing colloidal silver protein. Cutis
66:373-374.
Gunther, R. D., and E. M. Wright. 1983. Na+, Li+, and CI" transport by
brush border membranes of rabbit jejunum. J. Membr. Biol. 74:85-94.
Guo, B. S. 1988. Rare Earths in Agriculture. Beijing: China Agricultural
Science and Technology Press.
Halmagyi-Valter, T., T. Gippert, and 1. Pais. 1988. The effect of titanium-
ascorbate on reproduction. Pp. 145-152 in New Results in the Re-
search of Hardly Known Trace Elements and Their Role in the Food
Chain, 1. Pais, ed. Budapest: University of Horticulture and Food In-
dustry.
Hamilton, E. 1., and M. J. Minski. 1972/1973. Abundance of chemical ele-
ments in man's diet and possible relations with environmental factors.
Sci. Total Environ. 1:375-394.
Hamilton, E. 1., M. J. Minski, and J. J. Cleary. 1972/1973. The concentra-
tion and distribution of some stable elements in healthy human tissue
from the United Kingdom (an environmental study). Sci. Total Environ.
1:341-374.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
OTHER MINERALS
445
Hatano, M., K. Ishimura, K. Fuciiigami, I. Ito, Y. Hongo, Y. Hosokawa, S.
Hosokawa, and I. Azuma. 1981. Toxicological studies on germanium
dioxide (GeO^) (1) Acute, subacute, chronic toxicity and successive
irritation to the eye. Oyo Yakuri 21:773-796.
He, M. L., and W. A. Rambeck. 2000. Rare earth elements — a new genera-
tion of growth promoters for pigs? Arch. Anim. Nutr. 53:323-334.
He, M. L., J. Chang, R. Arnold, R. Henkelmann, X. Lin, A. SUB, and W. A.
Rambeck. 1999. Studies on the effect of rare earth elements in piglets.
Pp. 436^143 in 19. Arbeitstagung Mengen- und Spurenelemente, M.
Anke, W. Arnhold, H. Bergmann, R. Bitsch, W. Dorn, G. Flachowsky,
M. Glei, B. Groppel, M. Griin, H. Giirtler, G. Jahreis, D. Meissner, W.
Merbach, M. Mtiller, R. Miiller, U. Schafer, and H. J. Schneider, eds.
Leipzig: Verlag Harald Schubert.
He, M. L., D. Ranz, and W. A. Rambeck. 2001. Study on the performance
enhancing effect of rare earth elements in growing and fattening pigs. J.
Anim. Physiol. Anim. Nutr. (Berl). 85:263-270.
Hedrick, J. B. 2001. Rare earths. Pp. 61.1-61.10 in U.S. Geological Survey
Minerals Yearbook - 2001. Washington, DC: U.S. Geological Survey.
Hext, P. M., P. J. Pinto, and B. A. Rimmel. 1999. Subchronic feeding study
of antimony trioxide in rats. J. Appl. Toxicol. 19:205-209.
Higgens, E. S., D. A. Richert, and W. W. Westerfeld. 1956a. Competitive
role of tungsten in molybdenum nutrition. Fed. Proc. 15:274 (Abstr.).
Higgens, E. S., D. A. Richert, and W. W. Westerfeld. 1956b. Molybdenum
deficiency and tungstate inhibition studies. J. Nutr. 59:539—559.
Hill, C. H., B. Starcher, and G. Matrone. 1964. Mercury and silver interre-
lationships with copper. J. Nutr. 83:107-1 10.
Hilliard, H. E. 2003. Silver. Pp. 152-153 in Mineral Commodity Summa-
ries. Washington, D.C.: U.S. Geological Survey.
Hirasawa, F., M. Sato, and Y. Takizawa. 1994. Organ distribution of silver
and the effect of silver on copper status in rats. Toxicol. Lett. 70:193—
201.
Hirasawa, F., Y. Kawarada, M. Sato, S. Suzuki, K. Terada, N. Miura, M.
Fujii, K. Kato, Y. Takizawa, and T. Sugiyama. 1997. The effect of sil-
ver administration on the biosynthesis and the molecular properties of
rat ceruloplasmin. Biochim. Biophys. Acta-Gen. Subj. 1336:195-201.
Hodge, H. C. 1953. Pharmacology and Toxicology of Uranium Compounds,
C. Voegtlin and H. C. Hodge, eds. New York: McGraw-Hill.
Hogstrand, C, and C. M. Wood. 1998. Toward a better understanding of
the bioavailability, physiology, and toxicity of silver in fish: implica-
tions for water quality criteria. Environ. Toxicol. Chem. 17:547—561.
Holdway, D. A. 1992. Uranium toxicity to two species of Australian tropi-
cal fish. Sci. Total. Environ. 125:137-158.
Horovitz, C. T. 1993. Could scandium and yttrium be required for life? Pp.
747- 749 in Trace Elements in Man and Animals - TEMA 8, M. Anke,
D. Meissner, and C. F. Mills, eds. Gersdorf : Verlag Media Touristik.
Hu, M., H. Wu, and C. Chao. 1997. Assisting effects of lithium on hypogly-
cemic treatment in patients with diabetes. Biol. Trace Elem. Res.
60:131-137.
Iyengar, G. V. 1998. Reevaluation of the trace element content in reference
man. Radiat. Phys. Chem. 51:545-560.
Jensen, L. S. 1975. Modification of a selenium toxicity in chicks by dietary
silver and copper. J. Nutr. 105:769-775.
Jensen, L. S., R. P. Peterson, and L. Falen. 1974. Inducement of enlarged
hearts and muscular dystrophy in turkey poults with dietary silver. Poult.
Sci. 53:57-64.
Ji, Y. J., and M. Z. Cui. 1988. Toxicological studies on safety of rare earths
used in agriculture. Biomed. Environ. Sci. 1:270—276.
Karantassis, M. T. 1924. Toxicity of tungsten and molybdenum compounds.
Ann. Med. Leg. 5:44-50.
Katoh, Y., T. Sato, and Y. Yamamoto. 2002. Determination of multielement
concentrations in normal human organs from the Japanese. Biol. Trace
Elem. Res. 90:57-70.
Kavas-Ogly, A. A., F. E. LutfuUaev, A. N. Rafiev, V. A. Onishchenko,
B. A. Abbasova, E. V. Fidirko, and M. A. Rish. 1998. Trace ele-
ments in selected Uzbek dishes. Pp. 40^8 in 18. Arbeitstagung
Mengen- und Spurenelemente, M. Anke, W. Arnhold, H. Bergmann,
R. Bitsch, W. Dorn, G. Flachowsky, M Glei, B. Groppel, M. Griin,
H. Giirtler, G. Jahreis, 1. Lombeck, B. Luckas, D. Meissner, W.
Merbach, M. Mtiller, R. Miiller, and H. J. Schneider, eds. Leipzig:
Verlag Harald Shubert.
Kinard, F. W., and J. C. Aull. 1945. Distribution of tungsten in the rat
following ingestion of tungsten compounds. J. Pharmacol. Exp. Ther.
83:53-55.
Kinard, F. W., and J. Van de Erve. 1941. The toxicity of orally-ingested
tungsten compounds in rats. J. Pharmacol. Exp. Ther. 72:196-201.
Knight, W. M., V. R. Bohman, A. L. Lesperance, and C. Blincoe. 1967.
Strontium retention in the bovine. J. Anim. Sci. 26:839-844.
Krachler, M., F. Shi Li, E. Rossipal, and K. J. Irgolic. 1998. Changes in the
concentrations of trace elements in human milk during lactation. J. Trace
Elem. Med. Biol. 12:159-176.
Krachler, M., E. Rossipal, and D. Micetic-Turk. 1999. Trace element trans-
fer from the mother to the newborn - investigations on triplets of colos-
trums, maternal and umbilical cord sera. Eur. J. Clin. Nutr. 53:486^94.
Kunin, A. S., E. H. Dearborn, B. A. Buitows, A. S. Relman, and A. M. Roy.
1959. Comparison of renal excretion of rubidium and potassium. Am. J.
Physiol. 197:1297-1302.
Kurttio, P., A. Auvinen, L. Salonen, H. Saha, J. Pekkanen, 1. Makelainen, S.
B. Vaisanen, 1. M. Penttila, and H. Komulainen. 2002. Renal effects of
uranium in drinking water. Environ. Health Perspect. 110:337-342.
Lagarde, F., and M. Leroy. 2002. Metabolism and toxicity of tungsten in
humans and animals. Pp. 741—759 in Metal Ions in Biological Systems,
Vol. 39, Molybdenum and Tungsten: Their Roles in Biological Pro-
cesses, A. Sigel and H. Sigel, eds. New York: Marcel Dekker.
Leggett, R. W. 1989. The behavior and chemical toxicity of U in the kidney:
a reassessment. Health Phys. 57:365-383.
Li, J. F., M. Kirchgessner, andU. Steinruck. 1993. Growth promoting effect
and toxicity of germanium in chickens. Arch. Geflugelkd. 57:205-210.
Liu, Y., and Z. Min. 1999. Study of strontium and boron as antidotes to
fluoride toxicity. Toxicol. Environ. Chem. 70:1-7.
Llobet, J. M., J. J. Sirvent, A. Ortega, and J. L. Domingo. 1991. Influence of
chronic exposure to uranium on male reproduction in mice. Fund. Appl.
Toxicol. 16:821-829.
Lynch, B. S., C. C. Capen, E. R., Nestmann, G. Veenstra, and J. A. Deyo.
1999. Review of subchronic/chronic toxicity of antimony potassium
tartrate. Regl. Toxicol. Phaarmacol. 30:9-17.
Marie, P. J., M. Hott, D. Modrowski, C. De Pollak, J. Guillemain, P.
Deloffre, and Y. Tsouderos. 1993. An uncoupling agent containing
strontium prevents bone loss by depressing bone resorption and main-
taining bone formation in estrogen-deficient rats. J. Bone Miner. Res.
8:607-615.
Marie, P. J., P. Ammann, G. Boivin, and C. Rey. 2001. Mechanisms of
action and therapeutic potential of strontium in bone. Calcif. Tissue Int.
69:121-129.
Martinez, A. B., R. L. Cabrini, and A. M. Ubios. 2000. Orally administered
ethane-l-hydroxy-l,l-biphosphonate reduces the lethal effect of oral
uranium poisoning. Health Phys. 78:668—671.
Matsumoto, H., G. Z. Jiang, T. Hashimoto, N. Kuboyama, J. Yamane, K.
Nonaka, and A. Fujii. 2002. Effect of organic germanium compound
(Ge- 132) on experimental osteoporosis in rats: the relationship between
transverse strength and bone mineral density (BMD) or bone mineral
content (BMC). Int. J. Oral Med. Sci. 1:10-16.
McGlone, J. J., K. W. Kelley, and C. T. Gaskins. 1980. Lithium and porcine
aggression. J. Anim. Sci. 51:447^55.
Meltzer, H. L. 1991. A pharmacokinetic analysis of long-term administra-
tion of rubidium chloride. J. Clin. Pharmacol. 31:179—184.
Meltzer, H. L., R. M. Taylor, S. R. Platman, and R. R. Fieve. 1969. Ru-
bidium: a potential modifier of affect and behaviour. Nature 223:321—
322.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
446
MINERAL TOLERANCE OF ANIMALS
Meunier, P. J., D. O. Slosman, P. D. Delmas, J. L. Sebert M. L. Brandi, C.
Albanese, R. Lorenc, S. Pors-Nielsen, M. C. De Vernejoul, A. Roces,
and J. Y. Reginster. 2002. Strontium ranelate: dose-dependent effects in
established postmenopausal vertebral ostioporosis - a 2-year random-
ized placebo controlled trial. J. Clin. Endrocrinol. Metab. 87:2060-2066.
Mitchell, R. L. 1957. The trace element content of plants. Research (Lon-
don) 10:357.
Mitchell, R. R., S. D. Fitzgerald, R. J. Aulerich, R. J. Balander, D. C. Powell,
R. J. Tempelman, R. L. Stickle, W. Stevens, and S. J. Bursian. 2001a.
Health effects following chronic dosing with tungsten-iron and tung-
sten-polymer shot in adult game-farm mallards. J. Wildl. Dis. 37:451—
458.
Mitchell, R. R., S. D. Fitzgerald, R. J. Aulerich, R. J. Balander, D. C. Powell,
R. J. Tempelmen, W. Stevens, and S. J. Bursian. 2001b. Reproductive
effects and duckling survivability following chronic dosing with tung-
sten-iron and tungsten polymer shot in adult game-farm mallards. J.
Wildl. Dis. 37:468-474.
Momcilovic, B., and N. Gruden. 1981. The effect of dietary fibre on ^'Sr
and *"Ca absorption in infant rats. Experientia 37:498^99.
Monier- Williams, G. W. 1925. The solubility of glazes and enamels used in
cooking utensils. Analyst 50:133.
Monier- Williams, G. W. 1934. Antimony in Enamelled Hollow- Ware. Min
Health Rep. Publ. Health Med. Subj. No. 73. London: Her Majesty's
Stationery Office.
Moon, J. 1994. The role of vitamin D in toxic metal absorption: a review. J.
Am. Coll. Nutr. 13:559-564.
Morgan, T. P., and C. M. Wood. 2004. A relationship between gill silver
accumulation and acute silver toxicity in the freshwater rainbow trout:
support for the acute silver biotic ligand model. Environ. Toxicol. Chem.
23:1261-1267.
Morohashi, T., T. Sano, and S. Yamada. 1994. Effects of strontium on cal-
cium metabolism in rats. L A distinction between pharmacological and
toxic doses. Jpn. J. Pharmacol. 64:155-162.
Murthy, G. K., and U. Rhea. 1968. Cadmium and silver content of market
milk. J. Dairy Sci. 51:610-612.
Nakano, T., M. Fujii, T. Terai, T. Matsuzaka, M. Kimura, and T. Toyomasu.
1987. An ultrastructural study of rats treated with germanium. J. Clin.
Electron Microscopy 20:850-851.
Negretti de Bratter, V. E., P. Bratter, E. Pinto de Lopez, and L. Garcia de
Torres. 2000. Selenium-rubidium interaction in breast milk at high
dietary selenium intake. Pp. 726—729 in Metal Ions in Biology and
Medicine, vol. 6, J. A. Centeno, P. Collery, G. Vernet, R. B.
Finkelman, H. Gibb, and J. C. Etienne, eds. Paris: John Libbey
Eurotext.
Nielsen, F. H. 1986. Other elements: Sb, Ba, B, Br, Cs, Ge, Rb, Ag, Sr, Sn,
Ti, Zr, Be, Bi, Ga, Au, In, Nb, Sc, Te, Tl, W. Pp. 415-463 in Trace
Elements in Human and Animal Nutrition, vol. 2, W. Mertz, ed.
Orlando, FL: Academic Press.
Nodera, M., and H. Yanagisawa. 2003. Preventative effects of L-arginine
and enalapril on nephropathy caused by long-term GeOj intake. Biomed.
Res. Trace Elem. 14:326-328.
NRC (National Research Council). 1980a. Antimony. Pp. 24-39 in Mineral
Tolerance of Domestic Animals. Washington, D.C.: National Academy
Press.
NRC. 1980b. Tungsten. Pp. 515-524 in Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
NRC. 1980c. Uranium. Pp. 525-533 in Mineral Tolerance of Domestic
Animals. Washington, D.C.: National Academy Press.
Ober, J. A. 2002. Strontium. Pp. 74.1-74.5 in U.S. Geological Survey
Minerals Yearbook — 2002. Washington, D.C.: U.S. Government
Printing Office.
Oelkers. H. A. 1937. Zur Pharmakologies des Antimons. Arch. Exp. Pathol.
Pharmakol. 187:56-64.
Ogawa, Y. 1992. Studies on the biological effects of lanthanum— effects of repeated
oral administration tests in rats. Jpn. J. Toxicol. Environ. Health 38:545-553.
Ogawa, Y., S. Suzuki, K. Naito, M. Saito, E. Kamata, A. Hirose, A. Oho, T.
Kaneko. M. Chiba, Y. Inaba, and Y. Kurokawa. 1995. Toxicity study of
europium chloride in rats. J. Environ. Pathol. Toxicol. Oncol. 14:1-9.
Olcott, C. T. 1948. Experimental argyrosis. IV. Morphologic changes in the
experimental animal. Am. J. Pathol. 24:813-833
Olcott, C. T. 1950. Experimental argyrosis. V. Hypertrophy of the left ven-
tricle of the heart. Arch. Pathol. 49:138-149.
Otto, G. F., and T. H. Maren. 1950. Studies on the chemotherapy of filari-
asis. VI. Studies on the excretion and concentration of antimony in blood
and other tissues following the injection of trivalent and pentavalent
antimonials into experimental animals. Am. J. Hyg. 51:370—385.
Otto, G. F., T. H. Maren, and H. W. Brown. 1947. Blood levels and excre-
tion rates of antimony in persons receiving trivalent and pentavalent
antimonials. Am. J. Hyg. 46:193-211.
Owen, E. C, and R. Proudfoot. 1968. The effect of tungstate ingestion on
xanthine oxidase in milk and liver. Br. J. Nutr. 22:331—340.
Pais, I. 1983. The biological importance of titanium. J. Plant Nutr. 6:3-131.
Pais, I., M. Feher. E. Farkas, Z. Szabo, and I. Cornides. 1977. Titanium as a
new trace element. Commun. Soil Sci. Plant Anal. 8:407^10.
Pais, I., J. Bokori, B. Nagy, M. Szilagyi, S. Fekete, and F. Kolonics. 1989.
The role of titanium-ascorbate in animal nutrition and reproduction. Pp.
1356-1360 in 6th International Trace Element Symposium, vol. 4, As,
B, Br, Co, Cr, F, Fe, Mn, Ni, Sb, Sc, Si, Sn, and Other Ultra Trace
Elements, M. Anke, W. Baumann, H. Braunlich, Chr. Briickner, B.
Groppel, and M. Griin, eds. Leipzig: Karl-Marx-Universitat.
Palanivel, R., M. Thangqvel, K. Selvendiran, and D. Sakthisekaran. 2001.
Insulino-mimetic effect of ammonium paratungstate on protein metabo-
lism in streptozotocin-induced diabetic rats. Biomedicine 21:23-30.
Patt, E. L., E. E. Pickett, and B. L. O'Dell. 1978. Effect of dietary lithium
levels on tissue lithium concentrations, growth rate, and reproduction in
the rat. Bioinor. Chem. 9:299-310.
Paul, M., R. Mason, and R. Edwards. 1989. Effect of potential antidotes on
the acute toxicity, tissue disposition and elimination of selenium in rats.
Res. Comm. Chem. Path. Pharmacol. 66:441^50.
Pelkonen, K. H. O., H. Heinonen-Tanski, and O. O. P. Hanninen. 2003.
Accumulation of silver from drinking water into cerebellum and mus-
culus soleus in mice. Toxicology 186:151-157.
Peterson, R. P., and L. S. Jensen. 1975a. Induced exudative diathesis in
chicks by dietary silver. Poult. Sci. 54:795-798.
Peterson, R. P., and L. S. Jensen. 1975b. Interrelationship of dietary silver
with copper in the chick. Poult. Sci. 54:771-775.
Pickett, E. E., and B. L. O'Dell. 1992. Evidence for dietary essentiality of
lithium in the rat. Biol. Trace Elem. Res. 34:299-319.
Poon, R., I. Chu, P. Lecavalier, V. E. Valli, W. Foster, S. Gupta, and B.
Thomas. 1998. Effects of antimony on rats following 90-day exposure
via drinking water. Food Chem. Toxicol. 36:21—35.
Prakash, Kumar, B., and K. Shivakumar. 1998. Alterations in collagen me-
tabolism and increased fibroproliferation in the heart in cerium-treated
rats. Implications for the pathogenesis of endomyocardial fibrosis. Biol.
Trace Elem. Res. 63:73-79.
Prakash, Kumar, B., S. L. D'Souza, K. Shivakumar, and K. Rathinam. 1995.
Cerium stimulates protein biosynthesis in rat heart in vivo. Biol. Trace
Elem. Res. 50:237-242.
Pribyl, E. 1927. Nitrogen metabolism in experimental subacute arsenic and
antimony poisoning. J. Biol. Chem. 74:775—781.
Ragan, C. I. 1990. The effect of lithium on inositol phosphate metabolism.
Pp. 102-120 in Lithium and Cell Physiology, R. O. Bach, and V. S.
Gallicchio, eds. New York: Springer- Verlag.
Ralphs, M. H. 1997. Persistence of aversions to larkspur in naive and native
cattle. J. Range Manage. 50:367-370.
Ralphs, M. H., D. Graham, M. L. Galyean, and L. F. James. 1997. Creating
aversions to locoweed in naive and familiar cattle. J. Range Manage.
50:361-366.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
OTHER MINERALS
447
Regius, A., M. Anke, J. Sardi, and I. Mucsy. 1993. Effect of litliium supple-
mentation on performance of ewes and growing lambs. Pp. 603-604 in
Trace Elements in Man and Animals — TEMA 8, M. Anke, D. Meissner,
and C. F. Mills, eds. Gersdorf: Verlag Media Touristik.
Reid, D. F., and W. M. Sackett. 1977. Uranium and radium in livestock feed
supplements. Health Phys. 32:535-540.
Rosenfeld, G. 1954. Studies of the metabolism of germanium. Arch.
Biochem. Biophys. 48:84-94.
Rossetti, L., A. Giaccari, E. Klein-Robbenhaar, and L. R. Vogel. 1990.
Insulinomimetic properties of trace elements and characterization of
their in vivo mode of action. Diabetes 39:1243-1250.
Rossipal, E., M. Krachler, and D. Micetic-Turk. 1998. Concentrations of
trace elements in sera of young infants fed breast milk or infant formula.
Pp. 511—515 in Metal Ions in Biology and Medicine, vol. 5, Ph. Collery,
P. Bratter, V. Negretti de Bratter, L. Khassavova, and J. C. Etienne, eds.
Paris: John Libbey Eurotext.
Roy, R., and M. W. W. Adams. 2002. Tungsten-dependent aldehyde oxi-
doreductase: a new family of enzymes containing the pterin cofactor.
Pp. 673-697 in Metal Ions in Biological Systems, vol. 39, Molybdenum
and Tungsten: Their Roles in Biological Processes, A. Sigel and H.
Sigel, eds. New York: Marcel Dekker.
Rygh, O. 1949. Recherches sur les oligo-elements. I. De Timportance du
strontium, du barium et du zinc. Bull. Soc. Chim. Biol. 31:1052-1061.
Sanai, T., N. Oochi, S. Okuda, S. Osato, S. Kiyama, T. Komota, K.
Onoyama, and M. Fujishima. 1990. Subacute nephrotoxicity of germa-
nium dioxide in the experimental animal. Toxicol. Appl. Pharmacol.
103:345-353.
Sanai, T., S. Okuda, K. Onoyama, N. Oochi, S. Takaichi, V. Mizuhira, and
M. Fujishima. 1991a. Chronic tubulointerstitial changes induce by ger-
manium dioxide in comparison with carboxyethylgermanium
sequioxide. Kidney Int. 40:882-890.
Sanai, T., K. Onoyama, S. Osato, K. Motomura, N. Oochi, Y. Oh, S. Okuda,
S. Takaichi, and M. Fujishima. 1991b. Dose dependency of germanium-
dioxide-induced nephrotoxicity in rats. Nephron 57:349-354.
Sanchez, D. J., M. Belles, M. L. Albina, J. J. Sirvent, and J. L. Domingo.
2001. Nephrotoxicity of simultaneous exposure to mercury and ura-
nium in comparison to individual effects of these metals in rats. Biol.
Trace Elem. Res. 84:139-154.
Sato, 1., B. D. Yuan, T. Nishimura, and N. Tanaka. 1985. Inhibition of
tumor growth and metastasis in association with modification of im-
mune response by novel organic germanium compounds. J. Biol. Re-
sponse Modif. 4:159-168.
Schafer, S. G., and W. Forth. 1983. Excretion of metals into the rat intes-
tine. Biol. Trace Elem. Res. 5:205-217.
Schrauzer, G. N. 2002. Lithium: occun'ence, dietary intakes, nutritional es-
sentiality. J. Am. Coll. Nutr. 21:14-21.
Schrauzer, G. N., and K. P. Shrestha. 1990. Lithium in drinking water and
the incidences of crimes, suicides, and arrests related to drug additions.
Biol. Trace Elem. Res. 25:105-113.
Schroeder, H. A., and J. J. Balassa. 1967a. Abnormal trace metals in man:
germanium. J. Chron. Dis. 20:21 1-224.
Schroeder, H. A., and J. J. Balassa. 1967b. Arsenic, germanium, tin and
vanadium in mice: effects on growth, survival and tissue levels. J. Nutr.
92:245-252
Schroeder, H. A., and M. Mitchener. 1975. Life-term studies in rats. Effects
of aluminum, barium, beryllium, and tungsten. J. Nutr. 105:421^27.
Schroeder, H. A., and A. P. Nason. 1976. Interactions of trace metals in
mouse and rat tissues: zinc, chromium, copper and manganese with 13
other elements. J. Nutr. 106:198-203.
Schroeder, H. A., W. H. Vinton, Jr., and J. J. Balassa. 1963. Effect of chro-
mium, cadmium and other trace metals on the growth and survival of
mice. J. Nutr. 80:39^7.
Schroeder, H. A., J. J. Balassa, and V. H. Vinton, Jr. 1964. Chromium, lead,
cadmium, nickel and titanium in mice: effect on mortality, tumors and
tissue levels. J. Nutr. 83:239-250.
Schroeder, H. A., M. Kanisawa, D. V. Frost, and M. Mitchener. 1968a.
Germanium, tin and arsenic in rats: effects on growth, survival, patho-
logical lesions and life span. J. Nutr. 96:37^5.
Schroeder, H. A., M. Mitchener, J. J. Balassa, M. Kanisawa, and A. P.
Nason. 1968b. Zirconium, niobium, antimony and fluorine in mice: ef-
fects on growth, survival and tissue levels. J. Nutr. 95:95-101.
Schroeder, H. A., M. Mitchener, and A. P. Nason. 1970. Zirconium, nio-
bium, antimony, vanadium and lead in rats: life term studies. J. Nutr.
100:59-66.
Schroeder, H. A., 1. H. Tipton, and A. P. Nason. 1972. Trace metals in man:
strontium and barium. J. Chronic Dis. 25:491-517.
Schwietert, C. W., S. Yaghoubi, N. C. Gerber, J. J. McSharry, and J. P.
McCue. 2001. Dietary titanium and infant growth. Biol. Trace Elem.
Res. 83:149-167.
Scott, K. G., and J. G. Hamilton. 1950. The metabolism of silver in the rat
with radiosilver used as an indicator. Univ. Calif. Publ. Pharmacol.
2:241-262.
Seaborn, C. D., and Nielsen, F. H. 1994. Effects of germanium and silicon
on bone mineralization. Biol. Trace Elem. Res. 42:151-164.
Seifert, M., W. Arnhold, M. Jaritz, S. Holzinger, and M. Anke. 2002.
Strontium verzehr, -ausscheidung und -bilanz Erwachsener. Pp. 1217—
1222 in Macro and Trace Elements (Mengen- und Spurenelemente), M.
Anke, R. MUUer, U. Schafer, and M. Stoeppler, eds. Leipzig: Schubert-
Verlag.
Shaver, S. L., and K. E. Mason. 1951. Impaired tolerance to silver in vita-
min E deficient rats. Anat. Rec. 109:382.
Shavlovski, M. M., N. A. Chebotar, L. A. Konopistseva, E. T. Zakharova,
A. M. Kachourin, V. B. Vassiliev, and V. S. Gaitskhoki. 1995.
Embryotoxicity of silver ions is diminished by ceruloplasmin — further
evidence for its role in the transport of copper. Biometals 8:122-128.
Shedd, K. B. 2002. Tungsten. Pp. 80.1-80.6 in U.S. Geological Survey
Minerals Yearbook- 2002. Washington, D.C.: U.S. Government Print-
ing Office.
Smith, H. 1967. The distribution of antimony, arsenic, copper and zinc in
human tissue. J. Forensic Sci. Soc. 2:97-102.
Snyman, L. D., R. A. Schultz, T. S. Kellerman, and L. Labuschagne. 2002.
Continuous exposure to an aversive mixture as a means of maintaining
aversion to vermeerbos (Geigeria ornativa O. Hofffm.) in the presence
of non-averted sheep. Onderstepoort J. Vet. Res. 69:321-325.
Spencer, H., M. Li, J. Samachson, and D. Laszlo. 1960. Metabolism of
strontium-85 and calcium-45 in man. Metabolism 9:916-925.
Standen, A., ed. 1970. Kirk-Othmer Encyclopedia of Chemical Toxicology,
vol. 22. New York: John Wiley & Sons.
Stolk, J. M., W. J. Nowack, and J. D. Barchas. 1970. Brain norepinephrine:
enhanced turnover after rubidium treatment. Science 168:501—503.
Stolk, J. M., R. L. Conner, and J. D. Barchas. 1971. Rubidium-induced
increase in shock-elicited aggression in rats. Psychopharmacologia
(Berl.) 22:250-260.
Sugawara, N., and C. Sugawara. 2000. Competition between copper and
silver in Fischer rats with a normal copper metabolism and in Long-
Evans Cinnamon rats with an abnormal copper metabolism. Arch.
Toxicol. 74:190-195.
Sugihira, N., and K. T. Suzuki. 1991. Discrimination between strontium
and calcium in suckling rats. Biol. Trace Elem. Res. 29:1—10.
Sugihira, N., E. Kobayashi, and K. T. Suzuki. 1990. Age-related changes in
strontium to calcium ratios in rat tissues. Biol. Trace Elem. Res. 25:79—
88.
Sumino, K., K. Hayakawa, T. Shibata, and S. Kitamura. 1975. Heavy met-
als in normal Japanese tissues. Amounts of 15 heavy metals in subjects.
Arch. Environ. Health 30:487^94.
Swaine, D. J. 1955. The Trace Element Content of Soils. Harpenden, En-
gland. Commonwealth Bureau Soil Science Technical Communication.
48:91.
Sztajnki'ycer, M. D., and E. J. Otten. 2004. Chemical and radiological tox-
icity of depleted uranium. Military Med. 169:212-216.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
448
MINERAL TOLERANCE OF ANIMALS
Tannenbaum, A., and H. Silverstone. 1944. Some aspects of the toxicology
of uranium compounds. Pp. 59-96 in Toxicology of Uranium, A.
Tannenbaum, ed. New York: McGraw-Hill.
Tao, S., and M. Bolger. 1997. Hazard assessment of germanium supple-
ments. Regul. Toxicol. Pharmacol. 25:211—219.
Teekell, R. A., and A. B. Watts. 1959. Tungsten supplementation of breeder
hens. Poult. Sci. 38:791-794.
Tipton, 1. H., P. L. Stewart, and P. G. Martin. 1966. Trace elements in diet
and excreta. Health Phys. 12:1683-1689.
Ubios, A. M., M. B. Guglielmotti, T. Steimetz, and R. L. Cabrini. 1991.
Uranium inhibits bone formation in physiologic alveolar bone modeling
and remodeling. Environ. Res. 54:17-23.
USGS (U.S. Geological Survey). 2004. Antimony statistics and informa-
tion. Available at http://minerals.usgs.gov/minerals/pubs/commodity/
antimony. Accessed April 26, 2005.
Van Cauwenbergh, R., P. Hendrix, H. Robberecht, and H. Deelstra. 1999.
Daily dietary lithium intake in Belgium using duplicate portion sam-
pling. Z. Lebensm. Unters. Forsch. A 208:153-155.
Vanholder, R., R. Cornells, A. Dhondt, and N. Lameire. 2002. The role of
trace elements in uraemic toxicity. Nephrol. Dial. Transpl 17 (Suppl):2—
8.
Varo, P., M. Nuurtamo, E. Saari, and P. Koivistoinen. 1980a. Mineral ele-
ment composition of Finnish foods. III. Annual variation in the mineral
element composition of cereal grains. Acta Agric. Scand., Suppl. 22:27-
35.
Varo, P., M. Nuurtamo, E. Saari, and P. Koivistoinen. 1980b. Mineral ele-
ment composition of Finnish foods. IV. Flours and bakery products.
Acta Agric. Scand., Suppl. 22:37-55
Venugopal, B., and T. D. Luckey. 1978. Pp. 175-180 in Metal Toxicity in
Mammals. Chemical Toxicity of Metals and Metalloids, vol. 2. New
York: Plenum Press.
Versieck, J., and R. Cornells. 1980. Normal levels of trace elements in
human blood or serum. Anal. Chim. Acta 116:217-254.
Ward, N. 1., and F. R. Abou-Shakra. 1993. Rubidium levels in human tis-
sues and fluids. Pp. 81—85 in Trace Elements in Man and Animals —
TEMA 8, M. Anke, D. Meissner, and C. F. Mills, eds. Gersdorf: Verlag
Media Touristik.
Wasserman, R. H., E. M. Rommey, M. W. Skougstad, andR. Siever. 1977.
Strontium. Pp. 73-87 in Geochemistry and the Environment, vol. 2, The
Relation of Other Selected Trace Elements to Health and Disease. Wash-
ington, D.C.: National Academy of Science.
Weber, C. W., A. R. Doberenz, R. W. Wyckoff, and B. L. Reid. 1968.
Strontium metabolism in chicks. Poult. Sci. 47:1318-1323.
Weiner, M. L. 1991. Overview of lithium toxicology. Pp. 83-99 in Lithium
in Biology and Medicine, G. N. Schrauzer and K. F. Klippel, eds.
Weinheim: VCH Publishers.
Whanger, P. D., and P. H. Weswig. 1978. Influence of 19 elements on
development of liver necrosis in selenium and vitamin E deficient rats.
Nutr. Rep. Int. 18-421-428.
WHO (World Health Organization). 2003. Depleted uranium. Available at
http://www.who.int/mediacentre/factsheets/fs257/en/. Accessed on
April 26, 2005.
Wikipedia, the free encyclopedia. 2004a. Lithium. Available at http://
en.wikipedia.org/wiki/Lithium. Accessed on April 26, 2005.
Wikipedia, the free encyclopedia. 2004b. Rubidium. Available at http://
en.wikipedia.org/wiki/Rubidium. Accessed on April 26, 2005.
Winship, K. A. 1987. Toxicity of antimony and its compounds. Adverse
Drug Reactions and Acute Poisoning Review 6:67-90.
Wolf, N., I. Gedalia, S. Yariv, and H. Zuckerman. 1973. The strontium
content of bones and teeth of human fetuses. Arch. Oral Biol. 18:233-
238.
Wood, C. M., R. C. Playle, and C. Hogstrand. 1999. Physiology and model-
ing of mechanisms of silver uptake and toxicity in fish. Environ.
Toxicol. Chem. 18:71-83.
Wrenn, M. E., P. W. Durbin, and B. Howard. 1985. Metabohsm of ingested
U and Ra. Health Phys. 48:601-633.
Yaghoubi, S., C. W. Schwietert, and J. P McCue. 2000. Biological roles of
titanium. Biol. Trace Elem. Res. 78:205—217.
Yamaguchi, M., and M. Uchiyama. 1987. Preventive effect of zinc for toxic
actions of germanium and selenium on bone metabolism in weanling
rats. Res. Exp. Med. 187:395^00.
Yokoi, K., M. Kimura, and Y. Itokawa. 1994. Effect of a low-rubidium diet
on macro-mineral levels in rat tissues. J. Jpn. Soc. Nutr. Food Sci.
47:295-299.
Yoshida, M. 1993. Changes in serum thyroid hormone levels and urinary
ketone body excretion caused by a low selenium diet or silver loading in
rats. J. Trace Elem. Electrolytes Health Dis. 7:25—28.
Yukawa, M., M. Suzuki-Yasumoto, K. Amano, andM. Terai. 1980. Distri-
bution of trace elements in the human body determined by neutron acti-
vation analysis. Arch. Environ. Health 35:36^M.
Zaldivar, R. 1989. High lithium concentrations in drinking water and plasma
of exposed subjects. Arch. Toxicol. 46:319—320
Zeng, F., H. E. Tian, Z. Wang, Y. An, F. Gao, L. Zhang, F. Li, and L. Shan.
2003. Effect of rare earth element europium on amaranthin synthesis in
Amarathus caudatus seedlings. Biol. Trace Elem. Res. 93:271—282.
Zhang, W. D., F. Q. Li, X. Y. Zhang, and Y. Chen. 1988. Effects of traces
of rare earth elements on the protozoan Blepherisma and on mice. Biol.
Trace Elem. Res. 17:81-90.
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33
Minerals and Acid-Base Balance
INTRODUCTION
The maintenance of a stable pH in ttie fluids of tfie body
is essential to life. The pH of the extracellular fluids is main-
tained at about 7.4 and generally varies less than ± 0.05 pH
units. When considering the myriad of mechanisms involved
in acid-base balance, it is important to remember that the
core problem faced by the body is maintenance of the hydro-
gen ion (H"*") concentration of the extracellular fluids. Pro-
teins within cell membranes and the proteins comprising
enzyme systems are extremely sensitive to even small
changes in H+ concentration of the fluids bathing them.
Blood pH below 7.25 or above 7.5 can alter the tertiary struc-
ture of these proteins, severely testing the ability of most
animals to survive. Less severe perturbations in blood pH
over a long term can cause pathological changes in body
tissues involved in buffering blood. For example, during pro-
longed acidosis, calcium is released from bone tissues to
raise the pH of the blood. Over time this leads to a diminu-
tion of bone strength.
DETERMINATION OF ACID-BASE BALANCE
Each animal species has a normal blood pH. Simple mea-
surement of whole blood pH can quickly identify changes in
blood pH that might be considered a threat to the health and
productivity of an animal.
At its simplest, accurate measurement of blood pH can be
made with a pH probe inserted into whole blood that is col-
lected and maintained anaerobically until the pH measure-
ment is made. Collecting or pouring whole blood into an
open test tube and inserting a standard laboratory pH meter
is inappropriate, because exposure to the atmosphere allows
exchange of carbon dioxide and oxygen, rapidly altering the
pH of the sample. Blood gas analyzers, on the other hand,
have a special port that allows contact between whole blood
and the pH probe without exposure to the atmosphere. Fur-
ther procedures are necessary to further define the biological
basis for changes in blood pH, and their interpretation can
become quite complicated.
A relatively simple method that can be employed with
most commercial blood gas analyzers is to determine blood
carbon dioxide content using a carbon-dioxide-sensitive
electrode in conjunction with blood pH determination. If
blood hemoglobin level is also determined (or estimated
from normal values for that species), it is possible to deter-
mine blood base excess from blood pH, carbon dioxide, and
hemoglobin concentrations using a mathematical formula.
Blood base excess is defined as the amount of a strong acid
(such as hydrochloric acid) needed to titrate the pH of 100-
percent-oxygenated blood with a partial pressure of 40 mm
Hg from carbon dioxide, to a pH of 7.40 at 37°C. This value
gives a suitable index for assessing the nonrespiratory com-
ponent of an acid-base abnormality. Negative values suggest
a metabolic acidosis due to accumulation of anions in the
blood of the animal, while abnormally positive values indi-
cate metabolic alkalosis due to excessive accumulation of
cations in the blood.
When determining acid-base balance, it is preferable to
use arterial whole blood. However, venous blood can also be
used, bearing in mind that the acidity of venous blood is
normally greater than that of arterial blood. More refined
assessments and interpretations of acid-base status can be
made and are often necessary if the respiratory system is
compromised in any way (Constable, 1999).
Dietary Minerals and Acid-Base Pliysiology
The role of minerals in acid-base balance is best under-
stood by a review of the Strong Ion Difference Theory of
acid-base physiology (Stewart, 1983). The basic tenet of this
theory is that the number of moles of positively charged par-
ticles (cations) in any given solution (including body fluids)
must equal the number of moles of negatively charged par-
ticles (anions) in the solution, and that the product of the
concentration of hydrogen ions and hydro xyl ions is always
449
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MINERAL TOLERANCE OF ANIMALS
equal to the dissociation constant of water, approximately
1 X lO-'l
1 . number of moles cations = number of moles anions
2. [H+] X [OH-] = 1 X 10-14
Both equations must be satisfied simultaneously. Since
pH is the negative log of the concentration of hydrogen ions,
this essentially means that the pH of a solution is dependent
on the difference between the number of negatively and posi-
tively charged particles in the solution. If positively charged
particles are added to a solution such as plasma, the number
of H+ cations will decrease and the number of OH" anions
will increase to maintain the electroneutrality of the solution
(the solution becomes more alkaline). Conversely, adding
anions to a solution causes an increase in H+ and a decline in
OH" to maintain electroneutrality, and the pH decreases (the
solution becomes more acidic).
The primary cation and anion charges in the blood occur
as bicarbonate anions, nonmetabolizable anions and cations,
and blood proteins. Each contributes to blood and body
fluid pH.
Bicarbonate Anions [HC03i
The blood HCO3" concentration is essentially determined
by the concentration of COj in the blood as predicted by the
Henderson-Hasselbach equation, pH = pKa (6.1) + log
[HC03"]/[H2C03]. Blood COj concentration is under the
control of the respiratory system and allows minute-by-
minute fine tuning of blood pH. When respiratory function
is depressed, blood COj concentrations increase, increasing
the concentration of HCO3" anions, causing blood pH to
decline. Conversely, when respiratory rate is elevated (as
can occur in heat stress), blood CO, declines, blood HCO3"
declines, and pH increases.
Concentration of Nonmetabolizable Anions and Cations
The difference between the total number of non-
metabolizable cations and anions in the blood is referred to
as the Strong Ion Difference. Strong ions enter the blood
from the digestive tract, making the cation-anion difference
of the diet the ultimate determinant of blood Strong Ion Dif-
ference. Once Strong Ions are absorbed, their concentration
in the blood is regulated by the kidneys. Adjustment of the
Strong Ion Difference of the blood is slower than respiratory
control of blood pH but is capable of inducing much greater
changes in blood pH.
In theory, all cations and anions in the diet are capable of
exerting an influence on the Strong Ion Difference of the
blood. The major cations present in feeds and the "charge"
they carry are sodium (+1), potassium (+1), calcium (+2),
and magnesium (+2). The major anions and their charges
found in feeds are chloride (-1), sulfate (-2), and phosphate
(assumed to be -3). Sulfate is also released to body fluids
during catabolism of cysteine and methionine, and high
protein diets have long been recognized as decreasing blood
and urine pH. Most carnivores, therefore, are in a state of
mild metabolic acidosis and produce urine with a pH below
6.8 as the kidneys remove the anions from the blood (return-
ing blood pH toward normal) and place them into the renal
tubular fluids (reducing the pH of the glomerular filtrate).
Herbivores tend to ingest forages where the predominant
minerals are usually potassium and calcium. Since nearly all
of the dietary potassium cations ingested are absorbed across
the digestive tract, high forage diets place most herbivores in
a state of mild metabolic alkalosis, causing them to produce
alkaline urine.
Cations or anions present in the diet will only alter the
Strong Ion Difference (electrical charge) of the blood if they
are absorbed into the blood. Under normal circumstances,
the trace elements present in most diets are absorbed in such
small amounts that they are of negligible consequence to
acid-base status. However, improper supplementation with
very high amounts of trace minerals could affect acid-base
balance. Amino acid supplements are often prepared as the
salt of the amino acid (lysine hydrochloride, monosodium
glutamate, cysteine hydrochloride). Large doses of these
compounds can be toxic due to effects on systemic acid-base
balance (as opposed to toxicity from the amino acid itself).
Organic acids within the ingesta, such as the volatile fatty
acids, are generally absorbed into the bloodstream in the
undissociated form so that they carry both a positive and
negative charge into the blood. They also are rapidly me-
tabolized within the liver so they have only a small effect on
blood pH under most circumstances. However, if an organic
acid is consumed or produced at levels that exceed the liver's
ability to metabolize it, as in the case of rumen lactic acido-
sis, the anion (lactate) can build up in the blood of the af-
fected animal and cause severe metabolic acidosis.
The difference between the number of cation and anion
particles absorbed from the diet determines the pH of the
blood. The cation-anion difference of a diet is commonly
described in terms of mEq/kg of just sodium, potassium,
chloride, and sulfate as follows:
Dietary Cation-Anion Difference (DCAD, mEq) = (mEq
Na+ + mEq K+) - (mEq Cr + mEq S")
Generally, DCAD is calculated on the basis of 100 g or 1
kg of diet. This equation is useful, though it must be kept in
mind that Ca, Mg, and P absorbed from the diet will also
influence blood pH. It might be more proper to rewrite the
common equation as DCAD = (Na -H K H- Ca H- Mg) - (CI +
S + P). Trace minerals could also be included but generally
the amount (percent of diet) of any one trace mineral needed
to cause an acid-base imbalance would be well beyond the
toxic levels as described in the individual mineral chapters
in this book. The problem with any of these equations is that
they assume all of the cations and anions present in the diet
are absorbed in equal amounts into the blood of the animal.
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MINERALS AND ACID-BASE BALANCE
451
This simply is not true. Approximately 90 percent of ingested
sodium, potassium, and chloride are absorbed into the blood.
But most other minerals are not as well absorbed and their
rate of absorption can vary with form or source of the min-
eral (solubility, particle size, etc.) and the physiological state
of the animal. Unfortunately, few data exist to allow specifi-
cation of a coefficient of absorption in front of each element
of the DC AD equation for most species.
Concentration of Proteins in ttie Blood
Proteins, such as hemoglobin and albumin, tend to be
negatively charged and are considered as anions. Their con-
centration in blood is generally dependent on liver function.
Blood protein levels are fairly constant unless there are large
changes in liver function or plasma volume. Mineral toxici-
ties affecting liver function could therefore alter blood pH.
TOXICOSIS
Acute
If the amount of cations absorbed from the diet far ex-
ceeds the amount of anions absorbed from the diet, a severe
metabolic alkalosis can develop in the animal. Conversely,
ingestion of a diet in which the absorption of the anions in
the diet far exceeds the absorption of the cations in the diet
can induce a severe metabolic acidosis in the animal.
Uncompensated Metabolic Acidosis orAil<aiosis
When highly excessive amounts of readily absorbable
cations or anions are ingested, the ability of the kidneys and
respiratory system to compensate for the added cations (in
the case of metabolic alkalosis) or anions (in the case of
metabolic acidosis) is exceeded. The animal now enters a
state of uncompensated metabolic acidosis or alkalosis. Both
situations are acutely toxic and are often lethal. The acidotic
animal will exhibit severe respiratory exertion to regain con-
trol of blood pH by removing carbon dioxide as it attempts
to reduce blood bicarbonate anions. In alkalosis, respirations
will be slowed to permit carbon dioxide and bicarbonate an-
ions to build up in the blood. Metabolic alkalosis is more
quickly lethal than is metabolic acidosis. These are acute
toxicoses and animals can die from the acid-base imbalance.
At the very least, the animals very quickly reduce intake of
the diet, and performance quickly deteriorates simply from
lack of feed intake.
Ctironic
Compensated iVIetaboiic Acidosis orAII<alosis
Mild imbalances in dietary cation-anion difference cause
mild acid-base imbalances that can often be accommodated
by increased renal excretion of cations or anions. The respi-
ratory system can also be used to raise or lower the concen-
tration of bicarbonate anion in the blood to help restore blood
pH to normal. Though these actions spare the animal's life,
the chronic imbalances in acid-base can cause a reduction in
the animal's performance.
Bone is a large depot of buffer for the body. During meta-
bolic acidosis, calcium, and to a lesser extent, other cations
such as potassium and magnesium leave bone to help buffer
the acid (excess anion) in the blood. If prolonged, metabolic
acidosis will result in bone loss and increased susceptibility
to fracture. Conversely, calcium, magnesium, and potassium
can be deposited into the extracellular fluids of bone during
periods of metabolic alkalosis, reducing the cation load of
the blood and reducing blood pH.
Prolonged changes in acid-base status can also contribute
to urolithiasis in several species. Metabolic alkalosis has
been implicated as a contributing factor in formation of
struvite (magnesium ammonium phosphate) urethral stones
in cats, and it is common to add absorbable anions to the diet
to acidify the urine and help prevent their occurrence (Allen
et al., 1997). Unfortunately, as the urine is acidified, the
amount of calcium excreted in the urine increases, which
may increase susceptibility to formation of calcium oxalate
crystals and perhaps calcium phosphate crystals (Osborne et
al., 1996).
MAXIMAL TOLERABLE DIETARY CATION-ANION
DIFFERENCE FOR ANIMAL HEALTH AND
PRODUCTIVITY
It is impossible to determine the level of a single cation or
anion in the diet that can cause metabolic alkalosis without
considering the dietary content of other cations or anions
that might also contribute to the blood pH of the animal.
Therefore, the total cation-anion difference of a diet must be
considered. Unfortunately, there is no consensus on the type
of equation needed to describe cation-anion difference of a
diet.
In general, the research conducted with poultry uses the
equation (Na + K) - CI to describe diet "electrolyte balance."
Optimal growth and performance was reported when elec-
trolyte balance was between -1-200 and H-3G0 mEq/kg diet
(Johnson and Karunajeewa, 1985; Oviedo-Rondon et al.,
2001; Borges et al., 2003). Low (<180 mEq/kg) or high
(>3G0 mEq/kg) dietary electrolyte balance reduced growth
(Johnson and Karunajeewa, 1985). Early research with poul-
try described electrolyte balance as the equivalents of Na +
K/Cl (Sauveur and Mongin, 1978). Broiler performance was
reduced when Na -I- K/CI was less than H-30 mEq/kg diet, and
significantly reduced performance of hens was observed
when Na -I- K/Cl was <10 or >50 mEq/kg (Mongin, 1981).
However, other minerals (such as calcium, magnesium,
phosphate, and sulfate) are also known to contribute to acid-
base balance in birds. For example, Halleyetal. (1987) found
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452
MINERAL TOLERANCE OF ANIMALS
that the incidence of bone problems in broilers increased as
the ratio of calcium + magnesium to phosphorus + chloride
+ sulfate decreased.
Most mammalian research into acid-base balance has
used the DCAD equation (Na + K) - CI, until more recently,
when the contribution of sulfur was recognized, resulting in
the current DCAD equation (Na + K) - (CI + S). In lactating
dairy cows, milk production and feed intake are greatest
when the diet fed to lactating cows has a DCAD of +380
mEq/kg diet (using the formula (Na + K) - CI ) (Sanchez et
al., 1994). There is a significant decrease in milk production
when DCAD falls below +200 mEq/kg or rises above +550
mEq/kg diet using the equation (Na + K) - (CI + S)
(Ghorbani et al., 1995). Prior to parturition, lowering the
DCAD (Na + K) - (CI + S) below zero has proved to be an
effective means of preventing the development of hypocal-
cemia at parturition. At the lower blood pH induced by these
diets, calcium homeostasis is improved, apparently through
increased sensitivity of bone and kidney tissues to parathy-
roid hormone (Gaynor et al, 1989).
Acid-base status can also affect tissue responsiveness to hor-
mones not involved in calcium metabolism. For instance, meta-
bolic acidosis impairs glucose tolerance and tissue response to
insulin (Cuthbert and Alberti, 1978; Bigner et al., 1996) and
growth hormone (Kuemmerle et al., 1997). However, it is diffi-
cult to discern the DCAD at which these phenomena occur.
A negative DCAD, using (Na + K) - CI, reduces growth
in pigs (Dersjant-Li et al., 200 1), while DCAD between +200
and +500 seems well tolerated. Golz and Crenshaw (1991)
noted increased ammonium excretion when DCAD was re-
duced by dietary anion addition and concluded that alter-
ations in growth caused by changes in dietary K and possi-
bly CI levels were mediated via mechanisms involving renal
NH4+ metabolism during protein catabolism.
In horses, addition of cations to the diet or by oral gavage
may increase the tolerance of the animal to anaerobic buildup of
lactic acid during exercise (Hyyppa and Posa, 1998). Greenhaff
et al. (1990) suggested the horse can tolerate as much as 0.3 g
sodium bicarbonate / kg BW, given as a single oral dose.
Water pH can affect dissolved oxygen content of water
affecting aquaculture. Warm water, freshwater species can
tolerate water with a pH between 6 and 10. Cold water, fresh-
water fish can tolerate water with a pH between 6.5 and 8.5
(Colt, 1991). The interaction between diet cation-anion
balance and blood pH and performance of fish is largely
unknown, however.
The total cation-anion load in a diet can also be toxic, inde-
pendent of effects on blood pH (Bennett et al., 2003). These
osmotic effects are discussed in the chapter on sodium
chloride (NaCI).
REFERENCES
Allen, T., J. Barteges, L. Cowgill, C. Kirk, G. Ling, J. Lulicli, C. Osborne,
Q. Rogers, A. Ruby, S. Vaden, and L. Ulrich. 1997. Colloquium on
urology. Feline Pract. 25 {Suppl.):lS-32S.
Bennett, D. C, D. A. Gray, and M. R. Hughes. 2003. Effect of saline intake
on water flux and osmotic homeostasis in Pekin ducks (Anas
platyrhynchos). J. Comp. Physiol. B. 173:27-36.
Bigner D. R., J. P. Goff, M. A. Faust, J. L. Burton, H. D. Tyler, and R. L.
Horst. 1996. Acidosis effects on insulin response during glucose toler-
ance tests in Jersey cows. J. Dairy Sci. 79:2182-2188.
Borges S. A., A. V. Fischer da Silva, J. Ariki, D. M Hooge, and K. R.
Cummings. 2003. Dietary electrolyte balance for broiler chickens ex-
posed to thermoneutral or heat-stress environments. Poult. Sci. 82:428—
435.
Colt, J.1991. Aquacultural production systems. J. Anim. Sci. 69:4183^192.
Constable, P. D. 1999. Clinical assessment of acid-base status. Strong ion
difference theory. Vet. Clin. N. Am. Food Anim. Pract. 15:447^71.
Cuthbert, C, and K. G. Alberti. 1978. Acidemia and insulin resistance in
the diabetic ketoacidotic rat. Metabolism 27(Suppl. 2):1903-1916.
Dersjant-Li Y., H. Schulze, J. W. Schrama, J. A. Verreth, and M. W.
Verstegen. 2001. Feed intake, growth, digestibility of dry matter and
nitrogen in young pigs as affected by dietary cation-anion difference
and supplementation of xylanase. J. Anim. Physiol. Anim. Nutr.
85:101-109.
Gaynor, P. J., F. J. Mueller, J. K. Miller, N. Ramsey, J. P. Goff and R. L
Horst. 1989. Parturient hypocalcemia in Jersey cows fed alfalfa haylage-
based diets with different cation to anion ratios. J. Dairy Sci. 72:2525—
2531.
Ghorbani, G. R., J. A. Jackson, and R. W. Hemken. 1995. Influence of
increasing dietary cation-anion balance on the performance of lactating
dairy cattle. Iran Agric. Res. 14:157-174.
Golz, D. I., and T. D. Crenshaw. 1991. The effect of dietary potassium and
chloride on cation-anion balance in swine. J. Anim. Sci. 69:2504—2515.
Greenhaff P. L., D. H. Snow, R. C. Harris, and C. A. Roberts. 1990. Bicar-
bonate loading in the thoroughbred: dose, method of administration and
acid-base changes. Equine Vet. J. Suppl. 9:83-85.
Halley, J. T., T. S. Nelson, L. K. Kirby, andZ. B. Johnson. 1987. Effect of
altering dietary mineral balance on growth, leg abnormalities, and blood
base excess in broiler chicks. Poult. Sci. 66:1684—1692.
Hyyppa, S., and A. R. Poso. 1998. Fluid, electrolyte, and acid-base re-
sponses to exercise in racehorses. Vet. Clin. N. Am. Equine Pract.
14:121-136.
Johnson, R. J., and H. Karunajeewa. 1985. The effects of dietary minerals
and electrolytes on the growth and physiology of the young chick. J.
Nutr. 115:1680-1690.
Kuemmerle N., R. J. Krieg, Jr., K. Latta, A. Challa, J. D. Hanna, and J. C.
Chan. 1997. Growth hormone and insulin-like growth factor in non-
uremic acidosis and uremic acidosis. Kidney Int. (Suppl.) 58:S102—
S105.
Mongin, P. 1981. Recent advances in dietary anion-cation balance: applica-
tions in poultry. Proc. Nutr. Soc. 40:285-294.
Osborne, C, J. Lulich, R. Thumchai, L. Ulrich, L. Koehler, K. Bird, and J.
Barteges. 1996. Feline urolithiasis — etiology and pathophysiology. Vet.
Clin. N. Am. Small Anim. Pract. 26:217-232.
Oviedo-Rondon, E. O., A. E. Murakami, A. C. Furlan, I. Moreira, M.
Macari. 200 1 . Sodium and chloride requirements of young broiler chick-
ens fed corn-soybean diets (one to twenty-one days of age). Poult. Sci.
80:592-598.
Sanchez, W. K., D. K. Beede, and M. A. Delorenzo. 1994. Macromineral
element interrelationships and lactational performance: empirical mod-
els from a large data set. J. Dairy Sci. 77:3096-31 10.
Sauveur, B., and P. Mongin. 1978. Interrelationships between dietary con-
centrations of sodium, potassium and chloride in laying hens. Br. Poult.
Sci. 19:475^85.
Stewart, P. A. 1983. Modern quantitative acid-base chemistry. Can. J.
Physiol. Pharmacol. 61:1444-1461.
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34
Nitrates and Nitrites
INTRODUCTION
Nitrates (NO3) and nitrites (NO^) are salts or esters of
nitric acid (HNO3) and nitrous acid (HNOj), respectively.
Common inorganic nitrates and nitrites include ammonium
nitrate (NH4NO3), calcium nitrate (Ca(N03)2), calcium ni-
trite (Ca(NO-,)2), magnesium nitrate (Mg(N03)2), potassium
nitrate (KNO3), potassium nitrite (KNOo), sodium nitrate
(NaN03), and sodium nitrite (NaNOj). Nitrate and nitrite
compounds range in color from colorless to white or slightly
yellow and are generally very soluble in water. Calcium ni-
trate (Norwegian saltpeter) and sodium nitrate (Chile saltpe-
ter) are used in fertilizers. Sodium nitrate and nitrite are used
to cure, color, and preserve meat. Nitrates and nitrites are
used as a corrosion inhibitor and in diesel fuels. They are
used to make nitrous oxide, freezing mixtures, safety explo-
sives, matches, gunpowder, and radio tubes (Budavari,
1996).
Nitrates and nitrites are also formed naturally through the
nitrification process in the biological nitrogen cycle. Ammo-
nia in the soil is oxidized by aerobic bacteria to nitrite and
then further to nitrate. Although plants can use ammonia di-
rectly, most of the ammonia in soil is converted to nitrate
where plants assimilate it and convert it into amino acids and
proteins during growth (Campbell, 1990).
ESSENTIALITY
There is no known essentiality of nitrates or nitrites by
mammals. Nitrates and nitrites are an essential component
of the nitrogen cycle (Campbell, 1990). Plants cannot con-
vert atmospheric nitrogen (N2) directly and therefore rely on
prokaryotes to reduce nitrogen to ammonia, and on symbi-
otic bacteria on root nodules and nonsymbiotic bacteria in
the soil to convert ammonia to nitrate. Nitrate is the major
nutrient form of nitrogen in most soils and is often the rate-
limiting nutrient factor for plant growth (Wright and
Davison, 1964).
DIFFICULTIES IN METHODS OF ANALYSIS AND
EVALUATION
Several methods have been developed to determine ni-
trate or nitrite content in biological fluids (Greweling et al.,
1964; Shechter et al., 1972; Schneider and Yeary, 1973;
Green et al., 1982); food (Sanderson et al., 1991); plant ma-
terial (Cataldo et al., 1975; Bedwell et al., 1995); water
(Hubble and Harper, 2000); and soils (Kuchnicki and
Webster, 1986; Szekely, 1991). Primarily, methods should
be evaluated based on accuracy, precision, sensitivity, and
the potential for interference by other ions. Other practical
considerations may include the level of difficulty, time re-
quired, costs, and sample size.
Nitrate or nitrite analytical results may vary depending on
the method of analysis. Bedwell et al. (1995) compared the
diphenylamine spot plate (SPOT), spectrophotometric
(SPEC), nitrate selective electrode (NSE), and high perfor-
mance liquid chromatographic (HPLC) methods for nitrate
analysis in forages. The SPEC and NSE methods had simi-
lar, and the most accurate, nitrate recoveries. The SPOT
method overestimated the amount of nitrate and was the least
accurate. The HPLC method overestimated nitrate content
and resulted in a number of outlier values. The NSE method
was repeatable and had a low (P <.05) coefficient of varia-
tion compared to the SPOT, SPEC, and HPLC methods. The
HPLC method has also been compared to the
phenoldisulfonic acid (PDA) and hydrazine sulfate (HS)
methods for analysis of nitrates in soil (Kuchnicki and
Webster., 1986). Organic matter interfered with nitrate re-
covery using the PDA method. The HS method was more
precise than the PDA method; however, negative values were
often obtained when analyzing soil with low nitrate addi-
tion. When one soil sample was excluded, the HPLC method
had equal precision and greater accuracy than the HS
method. The recovery of 100 mg/kg of nitrate resulted in a
rangeof97.5-112percent, 87.9-93.6 percent, and 71.4-109
percent for the HPLC, HS, and PDA methods, respectively.
453
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MINERAL TOLERANCE OF ANIMALS
Sanderson et al. (1991) compared the HPLC method to the
cadmium reduction-Griess (Cd-G) method when using fresh
and cured meats. The precision was similar between meth-
ods; however, the accuracy was greater for the HPLC
method. Using one sample, the nitrate percent recovery was
80.1 percent for HPLC and 31.1 percent for Cd-G. Overall,
the nitrate values were higher (P <.05) for the HPLC as com-
pared to the Cd-G method. Nitrate values for fresh meats
ranged from 0.384 to 1.66 mg/kg and from to 1.07 mg/kg,
while cured meats ranged from 7.69 to 190 mg/kg and from
0.583 to 60 mg/kg for HPLC and Cd-G, respectively. Nitrate
analysis by nitration of salicylic acid (NSA), dissimilatory
nitrate reductase from Escherichia coli (DNR), and the PDA
methods were compared by Cataldo et al. (1975). Using corn
and oat plant samples, the NSA and DNR methods gave simi-
lar nitrate values. The PDA method was deemed adequate
when samples contain more than 1,000 mg/kg nitrate-N.
Interference by chloride (particularly at levels greater than
40 |Jg per assay [equivalent to 2 percent CL in plant tissue]),
nitrite, and ammonium ions occurred with analysis of nitrate
using the NSA method.
Nitrate or nitrite can be expressed in a variety of ways.
The reported form of nitrate or nitrite should be considered
when interpreting or comparing results. The following are
formulas that can be used for conversion of nitrate and ni-
trite fonns.
• Nitrate nitrogen (NO3-N) X 4.43 = Nitrate (NO",)
• Potassium nitrate (KNO3) X 0.613 = Nitrate (NO"3)
• Sodium nitrate (NaN03) X 0.729 = Nitrate (NO-3)
• Nitrite nitrogen (NOj-N) X 3.29 = Nitrite (NO^j)
• Sodium nitrite (NaNOj) X 0.667 = Nitrite (NQ-j)
REGULATION AND METABOLISM
Nitrate and nitrite absorption, distribution, and excretion
data have been reviewed by Walker (1990). In humans and
rats, the majority of ingested nitrate is absorbed from the
upper small intestine. A very small amount of nitrate is ab-
sorbed from the stomach, distal ileum, cecum, or proximal
colon. In ruminants, nitrates can be absorbed from the ru-
men, most likely occurring via the Cl^/HCOj" exchange
mechanism (Bruning-Fann and Kaneene, 1993). The absorp-
tion of nitrates is rapid. Witter and Balish (1979) detected
N-labeled nitrate and nitrite throughout the entire gastro-
intestinal tract of rats as soon as 15-30 minutes following
gavaged dose. They noted a similar pattern in the progres-
sion of N-labeled nitrate and nitrite through the gastro-
intestinal tract, although N-labeled nitrite remained in the
stomach for a longer period of time then nitrate.
Following absorption, nitrate quickly equilibrates with
interstitial fluids (Walker, 1990). Parks et al. (1981) admin-
istered 15 pi of radioactive nitrogen- 13, from nitrate or ni-
trite, intravenously to rabbits. Intravascular and extravascu-
lar '^NOj" and '^NO," equilibrium occurred within 5 minutes
of injection and nitrogen- 13 activity was distributed evenly
throughout most organs. This study was repeated using mice
and intratracheal administration of nitrogen- 13; results were
consistent. In humans and laboratory animals other than rats,
absorbed nitrate is selectively transported from the blood and
secreted into saliva (Walker, 1990). Bartholomew and Hill
(1984) orally dosed humans with 25, 50, 100, or 170 mg of
potassium nitrate in distilled water. For all dosage levels,
maximum salivary nitrate concentration was reached within
1 hour of nitrate ingestion. The proportion of orally ingested
nitrate that will be secreted in the saliva has been estimated
at 25 percent (Walker, 1990).
Literature about measuring the elimination of nitrate and
nitrite from plasma indicates that plasma nitrite elimination
half-lives are less variable between animal species as com-
pared to nitrate elimination half-lives (Lewicki et al., 1994).
Schneider and Yeary (1975) reported that the half-lives of
nitrite for dogs, sheep, and ponies were 0.499, 0.475, and
0.566 hours, while nitrate half-lives were 44.681, 4.233, and
4.821 hours, respectively. Lewicki et al. (1994) reported
similar values for sheep, with plasma nitrite and nitrate elimi-
nation half-lives of 0.49 hours and 4.5 hours, respectively. A
plasma nitrate elimination half-life of 22 hours was reported
for milk-fed calves orally administered nitrate, nitrite, or ni-
trate combined with nitrite (Hiisler and Blum, 2001).
The excretion of nitrates or nitrites has been investigated
using a variety of species. In general, nonruminant animals
excrete more urinary nitrate than ruminant animals and
horses excrete nitrate intermediate to nonruminant and ru-
minant animals (Bruning-Fann and Kaneene, 1993). Early
studies using dogs, rabbits, or goats as summarized by Wang
et al. (1981) found 30-90 percent of the ingested nitrate was
excreted in urine. Dull and Hotchkiss (1984) used ferrets
and reported that 36 percent of the nitrate ingested was ex-
creted in urine. Wang et al. (1981) used '^N-labeled sodium
nitrate or sodium nitrite in a single dose and multiple dose
feeding study with rats. They reported that within 72 hours
of the final dose, 60-70 percent of ingested '^N was excreted
in the urine and 10-20 percent was excreted in the feces. In
addition, at least 50 percent of the '^N excreted in the urine
and feces was not excreted as nitrate or nitrite. Schultz et al.
(1985) reported that 55 percent of ingested '^N was excreted
as nitrate in the urine of rats and 1 1 percent of ingested '^N
was excreted as urea or ammonia. Lewicki et al. (1994) ad-
ministered sodium nitrate or sodium nitrite to sheep intrave-
nously. Within 30 hours of the sodium nitrite dose, nitrate
and nitrite were excreted in the urine at 13.8 percent and
0.29 percent of the administered dose, respectively. Within
30 hours of administered nitrate, nitrite was not observed in
the urine and nitrate was excreted at 16.12 percent of the
administered sodium nitrate dose.
The amount of nitrate an animal will excrete is dependent
on the degree of microbial nitrate reduction that occurs
within the gastrointestinal tract. Nitrate reduction can occur
through the assimilatory nitrate reduction pathway, where
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NITRATES AND NITRITES
455
nitrate is reduced to nitrite and further converted to ammo-
nia, or thie denitrification patliway, wiiere nitrate is reduced
to nitrite, wiiich is furtlier reduced to nitric oxide, nitrous
oxide, and finally nitrogen gas (Russell, 2002). Rapid bacte-
rial reduction of nitrate to nitrite occurs in the rumen of ru-
minants; however, minimal nitrate reduction occurs in
nonruminant animals. The exception is the horse, which has
an enlarged cecum and colon allowing bacterial nitrate re-
duction that is intermediate to other nonruminant and rumi-
nant animals (Bruning-Fann and Kaneene, 1993).
SOURCES AND BIOAVAILABILITY
In humans and animals, exposure to nitrates or nitrites
occurs primarily through the ingestion of food and water.
Crops
Nitrate is the primary nitrogen source available to plants
in the soil (Garrett and Grisham, 1999) and under normal
environmental conditions, minimal nitrate is accumulated in
plants. Instead, nitrate absorbed by the roots is reduced to
ammonia and combined with carbohydrates to form amino
acids (Pfister, 1988). The reduction of nitrates to ammonia
in plants is called nitrogen assimilation and occurs in a two-
step process: (1) nitrate is reduced to nitrite via nitrate reduc-
tase and (2) nitrite is further reduced to ammonia via nitrite
reductase (Garrett and Grisham, 1999). The rate-limiting
enzyme for nitrogen assimilation is nitrate reductase
(Ferrario-Mery et al., 1997).
Many plants have the potential to accumulate nitrate at
toxic levels. Important forage crops that have been reported
to accumulate nitrate under certain conditions include sor-
ghum, Sudan grass, Johnson grass, oats, corn, and wheat.
Weeds that are nitrate accumulators include pigweed, kochia,
thistle, lambsquarter, bindweed, and ragweed (Sonderman,
1993). Cases of nitrate poisoning from forages have been
reported by Nicholls (1980) and Carrigan and Gardner
(1982).
The capacity to accumulate nitrates is dependant on a
variety of environmental and endogenous factors. Drought
conditions are commonly associated with nitrate accumula-
tion in plants. When soil moisture is limiting, nitrate assimi-
lation is depressed due to a reduction in nitrate reductase
activity and photosynthesis (Pfister, 1988). Reduced light
intensity also decreases nitrate reductase activity, thereby
increasing nitrate accumulation (Maynard et al., 1976; Blom-
Zandstra and Lampe, 1985; Pfister, 1988). Under normal
environmental conditions, increasing availability of nitro-
gen through fertilization may also increase nitrate accumu-
lation (George et al., 1973; MacLeod and MacLeod, 1974;
Reid and Strachan, 1974; Vieira et al., 1998). The impact of
plant genetics on nitrate accumulation is variable. Although
the tendency to accumulate nitrate is more commonly noted
for some forage species, nitrate accumulation is highly vari-
able even between cultivars of the same species (Wright and
Davidson, 1964; Maynard et al., 1976; Cardenas -Navvaro et
al., 1999). Herbicide application has been shown to affect
nitrate accumulation in plants; however, the response varies
by herbicide and plant species (Williams and James, 1983).
Phosphorus deficiency reduces nitrate uptake (Jeschke et al.,
1997). Molybdenum and manganese deficiency in plants is
associated with increased nitrate accumulation (Maynard et
al., 1976). Stems normally contain the highest levels of
nitrates, followed by roots, leaves, and flowers (Wright and
Davidson, 1964), and older leaf blades contain a higher con-
centration of nitrate than younger leaf blades (Cardenas-
Navarro et al., 1999).
Ensiling plants has been suggested as a method of reduc-
ing plant nitrate content (Ataku et al., 1982). However, the
extent of nitrate degradation is dependent on factors that af-
fect the rate of silage fermentation and therefore silage qual-
ity (Spoelstra, 1985). Ensiling processes that result in rapid
fermentation, reaching a stable pH within a couple of days,
result in less degradation of nitrate than extended fermenta-
tion, which occurs over several days to weeks. Silage nutri-
ent quality is better retained and "preserved" with rapid fer-
mentations than with a slow extended fermentation. The
following factors contribute to rapid fermentation and de-
creased nitrate degradation: high plant sugar content; wilt-
ing, lacerating, and chopping of plants; the addition of fer-
mentable substrates such as starch or sugar; or the addition
of fermentation inhibition products such as acids (Spoelstra,
1985). Ammonia, urea, or calcium carbonate, when added to
silages, will extend silage fermentation time (Li et al., 1992).
Spoelstra (1985) reported that adding these products to si-
lages reduced nitrate concentration but did not quantify the
extent of reduction. Li et al. (1992) evaluated the effects of
ammonium hydroxide, urea, calcium carbonate, or a micro-
bial inoculant on nitrate reduction over 28 days of fermenta-
tion. In experiment 1, ammonium hydroxide, calcium car-
bonate, microbial inoculant, or no additive along with 0;
2,000; 4,000; and 6,000 mg/kg nitrate N were added to
chopped corn plants. In experiment 2, urea, calcium carbon-
ate, or no additive along with 0; 2,380; 4,770; or 9,530 per-
cent nitrate N were added to chopped corn plants. After 28
days of ensiling, the additives in experiment 1 did not sig-
nificantly reduce nitrate N. In experiment 2, nitrate was re-
duced with the application of urea (15 percent) or calcium
carbonate (13 percent).
Food
Reviews by Wright and Davidson (1964), Walker (1975,
1990), Maynard al. (1976), and Van Diest (1986) reported a
range of nitrate and nitrite levels in food. Vegetables that
commonly have nitrate levels of 1,000 mg/kg or greater in-
clude spinach, lettuce, beets, radish, and turnips. Fruits gen-
erally contain less than 10 mg/kg nitrate, with the highest
nitrate levels ranging from 25 to 150 mg/kg for bananas.
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MINERAL TOLERANCE OF ANIMALS
Strawberries, and tomatoes (Walker, 1975, 1990). Nitrite
concentrations in fruits and vegetables are generally low.
Fresh meats usually have low levels of nitrates and nitrites,
while a wide range of values have been reported for cured
meats. Walker (1990) reported the nitrate and nitrite in cured
meats ranged from 19 mg/kg to 670 mg/kg and from mg/kg
to 96 mg/kg, respectively.
Water
Nitrate has been reported to be a common well water
contaminant in rural areas and in urban areas with a high
concentration of septic tanks (NRC, 1974). Squillace et al.
(2002) analyzed 1,497 wells, which were distributed across
the United States, and reported that 28 percent of them had
a nitrate-N concentration greater than 3 mg/L with 1 1 per-
cent exceeding the current EPA drinking water maximum
contaminant level of 10 mg/L. Nitrate-nitrogen levels
greater than 3 mg/L were associated with higher dissolved
oxygen concentrations, shallow well depth, unconfined
aquifers, agricultural land use, and population density. Ni-
trate was also detected in combination with atrazine in 13
percent of samples. Combinations of nitrate and atrazine or
nitrate, atrazine, and aldicarb have been shown to signifi-
cantly affect endocrine function and alter the aggression lev-
els of mice when added to water at 28 mg/L nitrate-nitrogen
and .01 mg/L atrazine and aldicarb (Porter et al., 1999). Ni-
trate with atrazine also significantly affected mouse immune
function. In 13 groundwater studies summarized by Spalding
and Exner (1993), between 3 and 35 percent of water
samples contained nitrate-N levels greater than 10 mg/L.
TOXICOSIS
Recent literature reviews on the toxicology of nitrates
and nitrites in nonruminant and ruminant animals have been
written by Pfister et al. (1988), Bruning-Fann and Kaneene
(1993), and Gangolli (1999). Selected references on the ef-
fects of nitrate or nitrite exposure on animals are listed in
Table 34-1. Nitrate toxicity is somewhat a misnomer as ni-
trate in itself is not considered to be highly toxic. Nitrate
becomes toxic when reduced to nitrite because nitrite,
through the oxidation of hemoglobin, can form methemo-
globin. Unlike hemoglobin, methemoglobin is unable to
transport oxygen in the blood (Burrows, 1980). In rumi-
nants, bacteria in the rumen rapidly convert nitrate to nitrite
and then to ammonia for assimilation into bacterial protein
(Russell, 2002). Nitrate toxicosis occurs when the conver-
sion of nitrite to ammonia is disrupted or when high levels
of nitrate are fed. Nonruminant animals generally have to
consume nitrite to induce methemoglobinemia and a toxic
effect of acute nitrate levels is generally severe gastritis
(Bruning-Fann and Kaneene, 1993). Clinical signs of meth-
emoglobinemia occur at 30-40 percent methemoglobin and
include rapid breathing and pulse rate, muscle tremors, in-
creased urination, and a chocolate brown appearance of the
blood. Death from methemoglobinemia occurs when meth-
emoglobin levels are greater than 80 percent (Burrows, 1980;
Bruning-Fann and Kaneene, 1993).
Acute— Ruminants
Nitrate poisoning in cattle consuming cornstalks was first
reported by Mayo in 1895. Bruning-Fann and Kaneene
(1993) summarized literature on the effects of nitrates and
nitrites on animal health. Numerous cases of nitrate toxicosis
were reported from 1950 to 1980. Acute poisoning occurred
when forages exceeded 5,000 mg/kg nitrate on a DM basis.
The LDjQ of cattle drenched with nitrate was estimated to be
330 mg of nitrate/kg BW, however, when nitrate was con-
sumed with feed, the LD^g tripled to 990 mg of nitrate/kg
BW. Gangolli (1999) reported that the oral single LD^q in
cows, using sodium nitrate, was estimated to be 328 mg of
nitrate/kg BW, but the same dose spread over a 24-hour
period increased the LDj^to 707-991 mg nitrate/kg BW.
Several factors affect the toxicosis of ingested nitrate
(Bruning-Fann and Kaneene, 1993). Composition of the diet
containing nitrate is an important determinant as to the mi-
crobial use of nitrates. Ruminants fed grain carbohydrates
along with high nitrate forages are more tolerant and less
prone to poisoning than when high nitrate forages are the
only feed in the diet. Pattern of eating also is important. Small
amounts of feed ingested slowly over an expanded period of
time allow animals to adapt to nitrate and result in less toxi-
cosis than the same amount ingested in a single feeding. Ac-
cording to Russell (2002), in vivo and in vitro studies indi-
cate rumen bacteria are highly adaptive to gradual increases
in nitrate. Monensin was reported to precipitate nitrate toxi-
cosis on high forage diets as it possibly shifts the rumen bac-
teria population to more nitrite producers (Bruning-Fann and
Kaneene, 1993).
Acute — Nonruminants
Gangolli (1999) reported the following oral LD^q values:
Mouse 1,808-4,556 mg nitrate/kg BW as sodium nitrate
Rat 3,543-6,561 mg nitrate/kg BW as sodium nitrate
Rat 1,899-3,736 mg nitrate/kg BW as ammonium
nitrate
Rabbit 1,954 mg nitrate/kg BW as sodium nitrate
Rabbit 1,165 mg nitrate/kg BW as potassium nitrate
Acute nitrate toxicosis has been reported in pigs, dogs,
turkeys, rats, and mice (Bruning-Fann and Kaneene, 1993).
In almost all cases, in addition to methemoglobin, gastric
lesions that were suggestive of salt poisoning were found.
Most cases of nitrate poisoning reported by Bruning-Fann
and Kaneene (1993) and Gangolli (1999) in nonruminant
animals occurred through direct ingestion of nitrate com-
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NITRATES AND NITRITES
457
pounds, experimentally or accidentally, or through water.
Most grains are low in nitrate content and therefore,
nonruminant farm animals are at a lower risk of nitrate toxi-
cosis than are ruminants where nitrate can accumulate in for-
ages. Straw was considered to be the source of nitrate poi-
soning in one case in pigs (Bruning-Fann and Kaneene,
1993).
Chronic— Ruminants
Ruminant animals can use nitrate as a nonprotein nitro-
gen source and therefore, effects of chronic nitrate toxicosis,
if they occur, are difficult to observe. Abortions have been
reported in ruminants receiving high doses of nitrate and
exhibiting clinical signs of nitrate toxicosis (Bruning-Fann
and Kaneene, 1993). Chronic nitrate toxicosis effects on pro-
duction parameters, BW gains, or milk production of rumi-
nants are relatively unknown. Beef cattle receiving more than
10,000 mg/kg nitrate in their diet and sheep more than 30,000
mg/kg nitrate in the diet exhibited reduced feed intake
(Bruning-Fann and Kaneene, 1993). Other possible effects
of nitrate cited by Bruning-Fann and Kaneene (1993) were
methemoglobin increases, possible changes in pituitary func-
tion, placental transfer of methemoglobin, transfer of some
nitrate into milk, and questionable but frequently reported
effects on vitamin A metabolism. No differences have been
reported when measuring the occurrence of birth weight of
offspring, number of services per conception, gestation, or
length of estrous cycle (Bruning-Fann and Kaneene, 1993).
Sonderman (1993) reported a higher incidence of abortions
in 13 beef cows exhibiting signs of toxicosis when orally
administered potassium nitrate at 0.270 mg nitrate/kg BW
on one day followed by 540 mg nitrate/kg BW the second
day during the third trimester of pregnancy. In 1 1 beef cows
given one oral dose of potassium nitrate at 400 mg nitrate/kg
BW, during the second trimester of pregnancy, signs of ni-
trate toxicosis were observed, but no abortions occurred.
Pregnant sheep given water containing 3,000-12,000 mg/L
nitrate from 21 to 49 days of pregnancy or heifers fed a diet
containing 445-665 mg of nitrate/kg for 2 months report-
edly increased methemoglobinemia, but no abortions were
observed (Gangolli, 1999).
Significant changes in blood parameters due to nitrate
ingestion have been reported. Sheep dosed intraruminally
with sodium nitrite at 130 mg nitrite/kg BW exhibited in-
creased erythrocyte counts, while at 200 mg nitrate/kg BW,
they exhibited hypochromic anemia. Increased leukocyte
counts, neutrophil and eosinophil percentages, and decreased
lymphocyte percentages were reported at both sodium ni-
trite levels. Additional research in cattle and sheep has sug-
gested that compensatory increases in hemoglobin concen-
tration, packed red cell, and blood volumes occur due to
extended periods of methemoglobinemia (Bruning-Fann and
Kaneene, 1993).
Clironic— Nonruminants
Nitrates and nitrites have reduced the growth rates of
nonruminant animals. Decreased BW gains have been re-
ported for chickens treated with sodium nitrate at 3,100 mg
nitrate/kg feed or sodium nitrite at 1,100 mg nitrite/kg diet
for 4 weeks (Atef et al., 1991); rats treated with sodium ni-
trate at 2,916 mg/kg nitrate or nitrite at levels ranging from
1,334 to 3,335 mg/kg (Till et al., 1988; Grant and Butler,
1989); and chicks or turkey poults treated with 1,067 mg/kg
nitrite in the form of sodium nitrite (Diaz et al., 1995). The
effect of nitrates or nitrites on reproductive performance var-
ies according to species. Increased fetal losses occurred when
guinea pigs were treated with nitrate or nitrite; nitrite had a
greater impact at lower levels (Sleight and Atallah, 1968). In
rats, nitrite caused increased postpartum offspring mortality
and a reduction in pup growth rates (Shuval and Gruener,
1972; Ema and Kanoh, 1983; Vorhees et al., 1984; Roth et
al., 1987). Research with pigs has not found an effect of
nitrate or nitrite on reproductive performance and an incon-
sistent response is reported in chickens (Bruning-Fann and
Kaneene, 1993).
Changes in blood traits due to nitrate or nitrite have been
shown in nonruminant animals. In pigs, nitrite increased he-
moglobin, and packed cell volume caused lymphocytosis and
resulted in anemia in pregnant rats (Bruning-Fann and
Kaneene, 1993). Plasma vitamin E levels decreased when
rats were treated with drinking water containing sodium ni-
trate at 1,458 mg/kg nitrate (Chow et al., 1980), and a dietary
deficiency in vitamin E intensified the effects of nitrite on
blood parameters of rats (Chow et al., 1984). The mutagenic
and carcinogenic potential of nitrates and nitrites has been
researched predominantly with rats and mice. A significant
increase in the occurrence of chromosomal aberrations in
bone marrow metaphase cells has been observed in adult rats
and in the liver of transplacentally exposed rat embryos (El
Nahas et al., 1984; Luca et al., 1985). Aoyagi et al. (1980)
reported that rats fed 534 or 1,067 mg/kg nitrite as sodium
nitrite, for almost 2 years, had an increased occurrence of
liver tumors and at 1,067 mg/kg nitrite, 40 percent of the
tumors were malignant. In another long-term feeding study.
Grant and Butler (1989) fed sodium nitrite to rats at 1,334
and 3,335 mg/kg nitrite; however the control animals had
the highest incidence of lymphoma, leukemia, and testicular
interstitial cell tumors. A small number of studies indicate
that nitrates or nitrites may negatively impact the motor de-
velopment and learning behavior of rats (Vorhees et al.,
1984; Market etal., 1989).
Toxicosis— Aquatic Animals
Nitrite, an intermediate product in the nitrification of
ammonia and the denitirification of nitrogenous com-
pounds, is much more toxic to fish and aquatic organisms
than is nitrate (Colt and Tchobanoglous, 1976; Pierce et
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MINERAL TOLERANCE OF ANIMALS
al., 1993; Basuyaux and Mathieu, 1999). The mechanism
of nitrite toxicity in fish is the same as it is for land ani-
mals in that nitrite causes the oxidation of heme (Fe"^+ to
Fe"'""'""'") and the inability of hemoglobin to transport oxy-
gen by converting it to methemoglobin (Jensen, 1999).
Freshwater fish are more sensitive to nitrite than are salt-
water fish as the chloride ions in salt water inhibit absorp-
tion of nitrite by actively competing with nitrites in the
gills for absorption. There is considerable variation
among and even within fish species in the sensitivity to
nitrite with rainbow trout, perch, and pike more sensitive
than carp, tench, and eel (Jensen, 1999).
Tiger shrimp were found to be much more tolerant of
increasing nitrate concentrations in water as salinity of the
water increased (Tsai and Chen, 2002). The 48-hour lethal
concentrations (LC^q) were 2,876; 3,894; and 4,970 mg ni-
trate-nitrogen/L in water that contained 15 percent, 25 per-
cent, and 35 percent seawater, respectively. Lin and Chen
(2003) exposed white shrimp to water containing from 25 to
250 mg of nitrite-nitrogen/L and salinity concentrations of
15 percent, 25 percent, or 35 percent. Decreasing salinity
from 35 percent to 15 percent increased susceptibility of
shrimp to nitrite-nitrogen by 277 percent, 298 percent, 405
percent, 418 percent, and 421 percent after 24, 48, 72, 96,
and 144 hours of exposure, respectively. Rainbow trout had
a less than 10 percent survival rate within 24 hours of being
in water that contained 32.2 mg/L nitrite and low concentra-
tions of calcium (<4.0 mg/L) and chloride (<0.3 mM/L)
(Bath and Eddy, 1980). However, when calcium was in-
creased to 80.2 mg/L, survival increased to 50 percent, and
increasing the chloride concentration to 21.3 mg/L resulted
in a similar survival rate.
Basuyaux and Mathieu (1999) exposed abalone and sea
urchins to water containing nitrite (0, 0.5, 1.0, 2.0, or 5.0 mg
nitrite-nitrogen/L) or nitrate (0, 25, 50, 100, or 250 mg
nitrate-nitrogen/L) for 2 weeks. No mortalities were
observed. Nitrite or nitrate levels in water where growth of
abalone was not reduced were <5 mg/L nitrite-nitrogen and
<100-250 mg/L of nitrate-nitrogen. Growth rates of abalone
were enhanced by adding up to 2 mg/L nitrite-nitrogen or
50 mg/L of nitrate-nitrogen to the water. Growth rate of sea
urchin declined after water contained 1-2 mg/L of nitrite-
nitrogen or more than 100 mg/L of nitrate nitrogen. Jensen
(1999) indicated that elevated levels of nitrite in the body of
aquatic animals not only lowered growth rates, but sup-
pressed immune function. The survival rate of grass carp
exposed to 1 or 1.6 mg/L of nitrite-nitrogen water for 15 days
was 94 percent (Alcaraz and Espina, 1997). At 2.5 mg/L of
nitrite-nitrogen in the water, the survival rate of the carp
decreased to 75 percent. These sublethal concentrations of
nitrite were found to decrease growth rate and alter energy
metabolism (Alcaraz and Espina, 1997). Survival of silver
perch was not affected by nitrite-nitrogen levels in water up
to 16.2 mg/L, but growth was reduced when levels exceeded
1.43 mg/L (Frances et al., 1998).
TISSUE LEVELS
There is limited reported research on the effects of nitrates
or nitrites in feed or water on tissue or milk nitrate and nitrite
concentrations. However, due to the rapid excretion of nitrate
and nitrites in urine and feces (Walker, 1990; Lewicki, 1994),
accumulation in tissues is not expected. Available research
reports no correlation between nitrate concentrations in diet or
water and tissue nitrate levels in pigs (R = .1 and R = .2,
respectively) (Eleftheriadou et al., 2002) and no correlation
between nitrate concentration in water and the nitrate concen-
tration of milk from cows (R = .2) (Nijhuis et al., 1982). Wright
and Davidson (1964) dosed cows with nitrate up to 150 mg/kg
BW/day for 6-12 months. Cows not dosed with nitrate and
cows dosed at the highest nitrate level had milk nitrate con-
centrations of 1.1 and 4.5 mg/L of milk, respectively. There-
fore, there is a very low risk of nitrate toxicosis, for adults or
infants, from consumption of milk from cows fed moderate to
high levels of nitrates.
MAXIMUM TOLERABLE LEVELS
Based on rat studies, the MTL of sodium nitrate or
potassium nitrate in the diet, where no toxicological effects
would be observed, is 1,823 mg nitrate/kg BW and 305 mg
nitrate/kg BW, respectively (Gangolli, 1999). Establishment
of MTL for other nonruminant species is difficult because of
the wide array of diets and other conditions that affect nitrate
toxicity. In ruminants, diets containing more than 5,000 mg/kg
nitrate, DM basis, have the potential of resulting in nitrate
toxicosis. The rumen bacteria act as an excellent buffer
against nitrate toxicosis, but also complicate the derivation
of a definitive MTL under all dietary conditions. However,
for all species, the MTL is a sum of both diet and water
concentration levels of nitrate. The EPA guideline of 10 mg/L
of nitrate-N in drinking water appears to be a very safe MTL,
as some studies have found no effects when animals were
given water containing 200 times this level while other
studies have reported reduced animal performance at only
20 times the EPA guideline. The National Academy of
Sciences (1974) recommended an upper limit of 100 mg/kg
nitrate-N and 10 mg/kg nitrite-N in the drinking water of
livestock and poultry.
FUTURE RESEARCH NEEDS
Although nitrate accumulation in plants has been studied,
additional research on important forage crops is needed to
determine the capacity of new hybrids or varieties, including
genetically modified plants, to accumulate nitrate. Addi-
tional research is needed to quantify the effects of ensiling
on nitrate reduction and under what conditions maximum
reduction occurs. Currently, research in this area is inconsis-
tent. Further research on the transfer of nitrate or nitrite in
consumed feed or water to tissues or milk is also needed.
Copyright © National Academy of Sciences. All rights reserved.
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NITRATES AND NITRITES
459
SUMMARY
Animals do not require a source of nitrate or nitrite; how-
ever, thiey can consume a significant amount in the process of
eating or drinking. Nitrate is a common water contaminant
and can accumulate in plants at toxic levels when stress is
encountered during growth. Nitrate itself is not very toxic;
however, it becomes toxic when reduced to nitrite resulting in
methemoglobinemia. Rumen bacteria rapidly convert nitrate
to nitrite; therefore, ruminants are more susceptible to nitrate
poisoning than nonruminants. Nitrate levels are generally low
in most grains and therefore, nonruminants also are less ex-
posed to naturally occurring nitrate toxicosis than are rumi-
nants. Nitrate toxicosis is most likely to occur naturally from
drinking of contaminated water and during periods of stressed
plant (forage) growth such as a drought. The summation of
consumed nitrate amounts from both feed and water need to
be considered when encountering nitrate toxicity problems.
REFERENCES
Alcaraz, G., and S. Espina. 1997. Scope for growth of juvenile grass carp
Ctenopharyngodon idella exposed to nitrite. Comp. Biochem. Pliysiol.
116C:85-88.
Aoyagi, M., N. Matsukura, E. Ucliida, T. Kawachi, T. Sugimura, S.
Takayama, and M. Matsui. 1980. Induction of liver tumors in Wistar
rats by sodium nitrite given in a pellet diet. J. Natl. Cancer Inst.
65(2):411^14.
Ataku, K., M. Horiguchi, and T. Matsumoto. 1982. Relationship between
silage quality and "N-nitrate reduction during ensilage. Pp. 663-665 in
Proceedings of the 14th International Grassland Congress, Lexington,
KY. Boulder, CO: Westview Press.
Atef, M., A. M. Abo-Norage, M. S. M. Hanafy, and A. E. Agag. 1991.
Pharmacotoxicological aspects of nitrate and nitrite in domestic fowls.
Br. Poult. Sci. 32:399-^04.
Bartholomew, B., and M. J. Hill. 1984. The pharmacology of dietary nitrate
and the origin or urinary nitrate. Food Chem. Toxicol. 22(10):789— 795.
Basuyaux, O. and M. Mathieu. 1999. Inorganic nitrogen and its effect on
the growth of the abalone Haliotis tuberculata Linneaus and the sea
urchin Paracentrotus lividus Lamark. Aquaculture 174:95-107.
Bath, R. N., and F. B. Eddy. 1980. Transport of nitrite across fish gills. J.
Exp. Zoof 214:119-121.
Bedwell, C. L., D. W. Hamar, M. L. Hoesterey, J .P. Sonderman, and K. G.
Odde. 1995. Comparison of four methods for forage nitrate analysis. J.
Vet. Diag. Invest. 7:527-530.
Blom-Zandstra, M., and J. E. M. Lampe. 1985. The role of nitrate in the
osmoregulation of lettuce {Lactuca sativa L.) grown at different light
intensities. J. Exp. Bot. 36:1043-1052.
Bruning-Fann, C. S., and J. B. Kaneene. 1993. The effects of nitrate, nitrite,
and N-nitroso compounds on animal health. Vet. Hum. Toxicol.
35(3):237-253.
Budavari, S., M. J. O'Neil, A. Smith, P. E. Heckelman, and J. F. Kinneary.
1996. The Merck Index: An Encyclopedia of Chemicals, Drugs, and
Biologicals, 12th ed. NJ: Merck and Co.
Burrows, G. E. 1980. Nitrate intoxication. J. Am. Vet. Med. Assoc.
177(l):82-83.
Campbell, N. A. 1990. Biology, 2nd ed. Riverside, CA: The Benjamin/
Cummings Publishing Company. Pp. 1 126-1 127.
Cardenas-Navarro, R., S. Adamowicz, and P. Robin. 1999. Nitrate accumu-
lation in plants: a role for water. J. Exp. Bot. 50{334):613-624.
Carrigan, M. J., and I. A. Gardner. 1982. Nitrate poisoning in cattle fed
sudex {Sorghum sp. Hybrid) hay. Aust. Vet. J. 59:155-157.
Cataldo, D. A., M. Haroon, L. E. Schrader, and V. L. Youngs. 1975. Rapid
colorimetric determination of nitrate in plant tissue by nitration of sali-
cylic acid. Commun. Soil Sci. Plant Anal. 6(l):71-80.
Chow, C. K., C. J. Chen, and C. Gairola. 1980. Effect of nitrate and nitrite
in drinking water on rats. Toxicol. Lett. 6:199-206.
Chow, C. K., C. B. Hong, M. E. Reese, and C. Gairola. 1984. Effect of
dietary vitamin E on nitrite-treated rats. Toxicol. Lett. 23:109-1 17.
Colt, J., and G. Tchobanoglous. 1976. Evaluation of the short-term toxicity
of nitrogenous compounds to channel catfish, Ictalurus punctatus.
Aquaculture 8:209-224.
Diaz, G. J., R. J. Julian, and E. J. Squires. 1995. Effect of graded levels of
dietary nitrite on pulmonary hypertension in broiler chickens and dila-
tory cardiomyopathy in turkey poults. Avian Pathol. 24:109-120.
Dull, B. J., and J. H. Hotchkiss. 1984. Nitrate balance and biosynthesis in
the fen-et. Toxicol. Lett. 23:79-89.
Eleftheriadou, A., A. Pexara, I. Gavrillidou, I. Ambrosiadis, S. Georgakis,
M. Politis, and I. Karanasios. 2002. Effect of nitrate and nitrite content
in water and feed on their presence in the muscle tissue of fattening
pigs. Arch. Lebensmittelhyg. 53:121-144.
El Nahas, S., M. Globus, and S. Vethamany-Globus. 1984. Chromosomal
aberrations induced by sodium nitrite in bone marrow of adult rats and
liver cells of transplacentally exposed embryos. J. Toxicol. Environ.
Health 13:643-647.
Ema, M., and S. Kanoh. 1983. Fetal toxicity of potassium nitrate in two
generations of rats. Folia Pharmacol. Jpn. 81:480 (Abstr.).
Ferrario-Mery, S., E. Murchie, B. Hirel, N. Galtier, W. P. Quick, and C. H.
Foyer. 1 997. Manipulation of the pathways of sucrose biosynthesis and
nitrogen assimilation in transformed plants to improve photosynthesis
and productivity. Pp. 125-153 in A Molecular Approach to Primary
Metabolism in Higher Plants, C. H. Foyer and W. P. Quick, eds. Lon-
don: Taylor and Francis.
Frances. J., G. L. Allan, and B. F. Nowak. 1998. The effects of nitrite on the
short-term growth of silver persch (Bidyanus bidyanus). Aquaculture
163:63-72.
Gangolli, S. D. 1999. Nitrate, nitrite, and N-nitroso compounds. Pp. 2111-
2143 in General and Applied Toxicology, vol. 3, B. Ballantyne, T. C.
Marrs. and T. Syversen, eds. New York: Grove's Dictionaries.
Garrett, R. H., and C. M. Grisham. 1999. Biochemistry 2nd Edition. Fort
Worth, TX: Saunders College Publishing and Harcourt Brace Pubhshers.
George, J. R., C. L. Rhykerd, C. H. NoUer, J. E. Dillon, and J. C. Burns.
1973. Effect of N fertilization on DM yield, total-N, N recovery, and
Nitrate-N concentrations of three cool-season forage grass species.
Agron. J. 65:211-216.
Grant. D., and W. H. Butler. 1989. Chronic toxicity of sodium nitrite in the
male F344 rat. Food Chem. Toxicol. 27(9):565-571.
Green, L. C, D. A. Wagner, J. Glogowski, P. L. Skipper, J. S. Wishnok, and
S. R. Tannenbaum. 1982. Analysis of nitrate, nitrite, and ['^N] nitrate in
biological fluids. Anal. Biochem. 126:131-138.
Greweling, T., K. L. Davidson, and C. J. Morris. 1964. Determination of
nitrate nitrogen in bovine blood, milk, urine, and rumen liquor. Agr.
Food Chem. 12(2): 139-143.
Hubble, D. S., and D. M. Harper. 2000. A revised method for nitrate analy-
sis at low concentrations. Water Res. 34(9):2598-2600.
Htisler, B.R., and J. W. Blum. 2001. Blood plasma response and urinary
excretion of nitrite and nitrate in milk-fed calves after oral nitrite and
nitrate excretion. J. Nutr. Biochem. 12:304—309.
Jensen, F. B. 1999. Physiological effects of nitrite in teleosts and crusta-
ceans. Pp. 169-186 in Toxicology of Aquatic Pollution Physiological,
Molecular and Cellular Approaches, E. W. Taylor, ed. Cambridge, UK:
Cambridge University Press.
Jeschke, W. D., E. A. Kirby. A. D. Peuke, J. S. Pate, and W. Hartung. 1997.
Effects of P deficiency on assimilation and transport of nitrate and phosphate
in intact plants of castor beans (Ricines communis L.). J. Exp. Bot. 48:75-91.
Kuchnicki, T. C, and G. R. B. Webster. 1986. A comparison of HPLC
analysis of nitrate in soils with the phenoldisulfonic acid and hydrazine
sulfate methods. Can. J. Soil Sci. 66:151—157.
Copyright © National Academy of Sciences. All rights reserved.
&
inemi Tnlemnce nf Animals- Sennnd Revised Edition
ttp7/www nap edi]/ratalng/1 1 rina htmll
460
MINERAL TOLERANCE OF ANIMALS
Lewicki, J., S. Garwacki, and M. Wiechetek. 1994. Nitrate and nitrite kinet-
ics after single intravenous dosage in sheep. Small Ruminant Res.
13:141-146.
Li, X., W. P. Hansen, D. E. Otterby, J. G. Linn, and C. S. Kuehn. 1992.
Effect of additives on fermentation of corn silage containing different
amounts of added nitrate nitrogen. J. Dairy Sci. 75:1555-1561.
Lin,Y., and C. Chen. 2003. Acute toxicity of nitrite on Litopenaeus
vannamei (Boone) juveniles at different salinity levels. Aquaculture
224:193-201.
Luca, D., L. Raileanu, V. Luca, and R. Duda. 1985. Chromosomal aben'a-
tions and micronuclei induced in rat and mouse bone marrow cells by
sodium nitrate. Mutat. Res. 155:121-125.
MacLeod, L. B., and J. A. MacLeod. 1974. Effects of N and K fertilization
on the protein, nitrate, and nonprotein reduced N fractions of timothy
and bromegrass. Can. J. Plant Sci. 54:331-341.
Maekawa, A., T. Ogiu, H. Onodera, K. Furuta, C. Matsuoka, Y. Ohno, and
S. Odashima. 1982. Carcinogenicity studies of sodium nitrite and so-
dium nitrate in F-344 rats. Food Chem. Toxicol. 20:25—33.
Market, E., C. Nyakas, and S. Ormai. 1989. Nitrate induced changes in
sensoro-motor development and learning behavior in rats. Acta Physiol.
Hung. 74(l):69-75.
Maynard, D. N., A. V. Bai'ker, P. L. Minotti, and N. H. Peck. 1976. Nitrate
accumulation in vegetables. Adv. Agron. 28:71—118.
Mondal, D. B., N. N. Pandy, and Kalicharan. 1999. Nitrate toxicity after
feeding sewage water irrigated cauliflower leaves in rabbits. Indian J.
Anim. Sci. 69(3): 192-194.
NRC (National Research Council). 1974. Nutrients and Toxic Substances
in Water for Livestock and Poultry. Washington, D.C.: National Acad-
emy Press.
Nicholls, T. J. 1980. Nitrate/nitrite poisoning of cattle on ryegrass pasture.
Aust. Vet. J. 56:95-96.
Nijhuis, V. H., W. Heeschen, and P. C. Lorenzen. 1982. Determination of
the carryover rate of nitrate in milk after oral intake by the lactating
cow. Milchwissenschaft, 37(l):30-32(Summary).
Parks, N. J., K. Krohn, C. A. Mathis, J. H. Chasko, K. R. Geiger, M. E.
Gregor, and N. F. Peek. 1981. Nitrogen- 13-labeled nitrite and nitrate:
distribution and metabolism after intratracheal administration. Science
212:58-61.
Pfister, J. A. 1988. Nitrate intoxication of ruminant animals. Pp. 233—259 in
The Ecology and Economic Impact of Poisonous Plants on Livestock
Production. L. F. James, M. H. Ralphs, and D. B. Nielsen, eds. Boulder,
CO: Westview Press.
Pierce, R. H., J. M. Weeks, and J. M. Prappas. 1993. Nitrate toxicity to five
species of marine fish. J. World Aquae. Soc. 24:105-107.
Porter, W. P., J. W. Jaeger, and 1. H. Carlson. 1999. Endocrine, immune,
and behavioral effects of aldicarb (carbamate), atrazine (triazine), and
nitrate (fertilizer) mixtures at groundwater concentrations. Toxicol. Ind.
Health 15:133-150.
Reid, D., and N. H. Strachan. 1974. The effects of a wide range of nitrogen
rates on some chemical constituents of the herbage from perennial
ryegrass swards with and without white clover. J. Agr. Sci. Cambridge
83:393-401.
Roth, A. C, G. E. Herkert, J. P. Bercz, and M. K. Smith. 1987. Evaluation
of the developmental toxicity of sodium nitrite in Long-Evans rats.
Fund. Appl. Toxicol. 9:688-677.
Russell, J. B. 2002. Rumen microbiology and its role in ruminant nutrition.
Ithaca, NY: James B. Russell.
Sanderson, J. E., J. R. Consaul, and K. Lee. 1991. Nitrate analysis in meats:
comparison of two methods. J. Food Sci. 56(4): 1123— 1124.
Shechter, H., N. Gruener, and H. I. Shuval. 1972. A micromethod for the
determination of nitrite in blood. Anal. Chim. Acta 60:93-99.
Schneider, N. R., and R. A. Yeary. 1973. Measurement of nitrite and nitrate
in blood. American J. Vet. Res. 34(1):133-135.
Schneider, N. R., and R. A. Yeary. 1975. Nitrite and nitrate pharmacokinet-
ics in the dog, sheep, and pony. Am. J. Vet. Res. 36(7):941-947.
Schultz, D. S., W. M. Deen, S. F. Karel, D. A. Wagner, and S. R.
Tannenbaum. 1985. Pharmacokinetics of nitrate in humans: role of gas-
trointestinal absorption and metabolism. Carcinogenesis 6:847-852.
Shimada, T. 1989. Lack of teratogenic and mutagenic effects of nitrite on
mouse fetuses. Ai'ch. Environ. Health 44(l):59-63.
Shuval, H. 1., and N. Gruener. 1972. Epidemiological and toxicological
aspects of nitrates and nitrites in the environment. Am. J. Public Health
62:1045-1052.
Sleight, S. D., and O. A. Atallah. 1968. Reproduction in the guinea pig as
affected by chronic administration of potassium nitrate and potassium
nitrite. Toxicol. Appl. Pharm. 12:179-185.
Squillace, P. J., J. C. Scott, M. J. Moran, B. T. Nolan, and D. W. Kolpin.
2002. VOCs, pesticides, nitrate, and their mixtures in groundwater used
for drinking water in the United States. Environ. Sci. Technol. 36: 1923—
1930.
Sonderman, J. P. 1993. Nitrate intoxication in ruminants: effects on preg-
nancy and corpus luteum function and analytical methods for nitrates.
Dissertation. Colorado State University. Fort Collins.
Spalding, R. F., and M. E. Exner. 1993. Occurrence of nitrate in groundwa-
ter — a review. J. Environ. Qual. 22:392^02.
Spoelstra, S. F. 1985. Nitrate in silage — review paper. Grass Forage Sci.
40:1-11.
Szekely, E. 1991. A rapid colorimetric method for analysis of nitrate nitro-
gen by reduction to nitrite. Comm. in Soil Sci. Plant Anal. 22(13 and
14):1295-1302.
Till, H. P., H. E. Falke, C. F. Kuper, and M. 1. Willems. 1988. Evaluation of
the oral toxicity of potassium nitrite in a 13-week drinking water study
in rats. Food Chem. Toxicol. 26(10):851-859.
Tsai, S., and J. Chen. 2002. Acute toxicity of nitrate on Penaeus monodon
juveniles at different salinity levels. Aquaculture 213:163-170.
Van Diest, A. 1986. Means of preventing nitrate accumulation in vegetable
and pasture plants. Pp. 455^71 in Fundamental, Ecological, and Agri-
cultural Aspects of Nitrogen Metabolism in Higher Plants. Netherlands:
Martinus Nijhoff Publishers.
Vieira, I. S., E. P. Vasconcelos, and A. A. Monteiro. 1998. Nitrate accumu-
lation, yield, and leaf quality of turnip greens in response to nitrogen
fertilization. Nutrient Cycl. Agroecosys. 51:249—258.
Vorhees, C. V., R. E. Butcher, R. L. Brunner, and V. Wootten. 1984. Devel-
opmental toxicity and psychotoxicity of sodium nitrite in rats. Food and
Chem. Toxicol. 22(l):l-6.
Walker, R. 1975. Naturally occurring nitrate/nitrite in foods. J. Sci. Food
Agric. 26:1735-1742.
Walker, R. 1990. Nitrates, nitrites andN-nitrosocompounds: a review of the
occurrence in food and diet and the toxicological implications. Food
Addit. Contam. 7(6):717-768.
Wang, C. F., R. G. Cassens, and W. G. Hoekstra. 1981. Fate of ingested
'^N-labeled nitrate and nitrite in the rat. J. Food Sci. 46:745-748.
Williams, M. C, and L. F. James. 1983. Effects of herbicides on the con-
centration of poisonous compounds in plants: a review. Am. J. Vet. Res.
44(12):2420-2422.
Witter, J. P., and E. Balish. 1979. Distribution and metabolism of ingested
NO," and NO^" in germ-free and conventional-flora rats. Appl. Environ.
Microb. 38(5)1861-869.
Wright, M. J., and K. L. Davison. 1964. Nitrate accumulation in crops and
nitrate poisoning in animals. Pp. 197—247 in Advanced Agronomy.
Ithaca, NY: Cornell University.
Copyright © National Academy of Sciences. All rights reserved.
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inemi Tnlemnce nf Animals- Sennnd Revised Edition
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35
Water as a Source of Toxic Substances
INTRODUCTION
Water is a simple compound composed of two tiydrogen
atoms bonded to one oxygen atom. And yet, it is ttie nutrient
most essential to sustain life. In most nonaquatic animals,
water accounts for 50 to 70 percent of BW. In neonates and
very young animals, water can account for more than 80
percent of the body mass. Water is found in both intracellu-
lar and extracellular spaces and provides the solvent for the
movement of nutrients, waste products, and metabolic inter-
mediates between body compartments. Water also functions
in the maintenance of body temperature. Loss of 20 percent
or more of the body's water content is generally fatal to most
animals.
Body water is derived from water consumed directly by
drinking and eating, or from the metabolic reactions related
to the oxidation of carbohydrates and fats in the body. Under
most situations, metabolic water is an insignificant source of
water for poultry and livestock compared to water consumed
by drinking or eating. Body water is lost through urine, fe-
ces, expiration of air, and perspiration.
The amount of water an animal requires depends on many
physiological and environmental factors. For most terres-
trial animals, water requirements and thus intakes are af-
fected by body size; physiological state such as gestation,
growth, and lactation; health; and environmental conditions.
Lactating animals have particularly high water requirements
to replace the water loss through milk production. Compared
to animals in cool or cold climates, animals in climatic con-
ditions where temperatures exceed their thennal neutral zone
will consume more water per day to replace losses from
sweating or evaporation from the lungs and to aid in the
thermal regulation of internal body temperature. Sweating
and evaporative water losses will be greater in hot arid con-
ditions than in hot humid conditions and thus, water require-
ments will be greater in hot arid climates. Animals experi-
encing health problems resulting in diarrhea or excess
urination can lose significant amounts of water from the body
very quickly, resulting in possible life-threatening dehydra-
tion if water and electrolyte fluids are not replaced.
Thirst is a conscious desire to drink water. The thirst cen-
ter is located in the anterior hypothalamus and regulates the
release of vasopressin or antidiuretic hormone. Thirst is pri-
marily triggered by an increase in the osmolarity of the blood
but may be triggered by a decrease in blood volume.
Osmoreceptors in the hypothalamus are particularly affected
by changes in sodium chloride. A 1-2 percent increase in
osmolarity will trigger a thirst sensation, which is partly ex-
hibited by dryness of the mouth and throat. Losses in blood
volume must be quite extensive, greater than 10 percent, to
trigger thirst.
Because water is an essential nutrient for animals and an
excellent solvent for minerals and other compounds, it can
be a medium for consumption of excess minerals, undesir-
able minerals, and toxic substances. The purpose of this
chapter is to make readers aware of the complexity of min-
eral forms that can be found in water, review the sources of
minerals and toxic compounds in water, and briefly summa-
rize water-mineral toxicities discussed in the various indi-
vidual chapters throughout the book.
SOURCES OF MINERALS AND TOXIC SUBSTANCES
IN WATER
Water contains many different elements and compounds
beyond its basic hydrogen and oxygen structure. The high
boiling point and heat of vaporization, a high surface ten-
sion, a density that is maximized at 4°C and not the freezing
point, and a physical property of expanding on freezing are
characteristics that make water an excellent solvent and re-
active with the salts and polar molecules through which wa-
ter passes. The exchange of elements between water and its
environment is a very complex system involving atmo-
spheric chemistry, water chemistry, sediment geochemistry,
soil chemistry, kinetics, and residence time of the water in
an aquifer or holding location. Thus, the elements found in
469
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470
MINERAL TOLERANCE OF ANIMALS
water will exist in a variety of oxidation states, protonated
and nonprotonated forms, as free ions, and as complex ion
forms. The mineral or element composition of ground water
is affected by the composition of the rock through which
water passes or in which it is stored, its residence time in the
aquifer, the solubility of the mineral elements in the rock,
the soil types through which the water passes to enter the
aquifer, the original mineral composition of the rain water or
water entering the aquifer, and the pH of the water. Mineral
composition of surface water is affected by many of the same
factors that affect ground water, as well as by airborne pol-
lutants, dry windblown solid depositions, decaying organic
matter, and removal of minerals by vegetation growth.
The sources and concentrations of many elements found
in unpolluted fresh water and in sea water are presented in
Table 35-1 and Table 35-2, respectively. However, as shown
in many of the individual mineral chapters, the reactivity
and toxic level of mineral elements are related to the form in
which the mineral exists. Thus, knowing only the concentra-
tion of a mineral in water is an incomplete description as to
the toxicity and the availability of the mineral.
The form of a mineral or element in water is referred to as
speciation. An element can exist in water as a simple hy-
drated ion, as a molecule, as a complex with another ion or
molecule, and as many other additional complexes (Stumm
and Morgan, 1996). A list of the major mineral species found
in fresh and salt water is given in Table 35-3. In fresh water,
hydroxo and carbonate complexes are the predominant form
of many minerals. While the assumption is that most miner-
als occur in a dissolved state in water, they often can exist as
very minute, or colloidal, suspended particles. Many colloi-
dal precipitates, such as Fe(OH)3, are small enough to pass
through filters and thus are not recognized as particulate
matter, but as a dissolved substance.
Most water analyses only provide information related to
the total amount of a mineral in the water and do not provide
any indication as to the speciation.
For many of the major cation minerals, the concentration
of the anions (S, CI) and pH will provide an indication as to
speciation. For example, magnesium is usually found in
water in the ion state (Mg"'""''), but MgS04 predominates when
sulfate exceeds 1,000 mg/L, and MgOH"*" occurs when the
solution is very basic (pH >10). Iron is usually found in water
as ferrous (Fe"*""*"), but oxidation state and complexing with
carbonate will vary with pH. At a pH <7, iron is commonly
found as Fe+++, FeOH++, and Fe (OH)2+; at a pH of 9.5 iron is
found as FeCOH)"*"; and at a pH >1 1, iron is found as Fe(OH)3"^
and HFeO,~. For both iron and manganese, when sulfate
levels in water increase above 200 mg/L, they increasingly
complex with sulfate, and the major form of these two
minerals in water will be FeS04 and MnS04.
The accuracy of the measurement of major minerals in
water can be estimated by computing an Electro Neutrality
(EN, percent) value. The sum of the positive and negative
charges in water should balance as water must be at electri-
cal neutrality. When concentrations of cations Na"*", K"*",
Mg++, and Ca++, and anions CI", HCO3", SO42-, NO3", are
expressed as mEq/L, the following formula can be used to
check the accuracy of the analysis:
EN, % =
(Sum cations + Sum anions)
(Sum cations - Sum anions)
xlOO
Differences in EN up to 2 percent are uncontrollable error,
but errors above 5 percent indicate sampling or analytical
problems. An exception may be when the water is very high
in iron, ammonia, or acidity, as these factors are not consid-
ered in the formula (Appelo and Postma, 1999).
MINERALS AND TOXIC SUBSTANCES IN WATER
Terrestrial Animals
Table 35-4 lists the Environmental Protection Agency
guidelines for human drinking water. These guidelines are
divided into enforceable standards and secondary standards.
Enforceable standards are levels that cannot be exceeded in
water, and action to achieve lower levels must be taken. Sec-
ondary standards are guidelines and levels at which cosmetic
(tooth or skin discoloration) or aesthetic (taste, odor, color)
effects are apparent.
The human drinking water guidelines generally offer a
very conservative assessment of water quality compared to
the livestock guidelines presented in Table 35-4. Thus, use
of human enforceable and secondary water quality guide-
lines should provide more than a safe guideline for livestock
and poultry.
Based on the information contained in this publication,
relatively few minerals naturally found in water are poten-
tially toxic. Natural contamination levels of the materials
arsenic, barium, iron, manganese, sodium chloride, sulfur,
and nitrate can be high due to the geological environment
through which the water passes or in which the water is con-
tained. These levels could either be toxic or could contribute
significantly to the toxicity of the mineral. Lithium, stron-
tium, and uranium concentrations in water can also be el-
evated in isolated cases, but widespread high levels are not
commonly found. In most situations, the naturally occurring
minerals in water do not result in acute toxicosis, but lead to
chronic conditions of poor animal performance or increased
health problems. Naturally occurring levels of most other
elements (aluminum, bismuth, boron, bromine, cadmium,
chromium, cobalt, copper, lead, mercury, molybdenum,
nickel, silicon, tin, and some rare earth elements) are low,
and toxicosis or a significant contribution to toxicosis from
water levels of these elements occurs from an exogenous
contamination or pollutant. Required macro elements such
as calcium, magnesium, phosphorus, and potassium are un-
likely to be at levels that cause toxicosis, but are more likely
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WATER AS A SOURCE OF TOXIC SUBSTANCES
471
to result in aesthetic secondary standard effects. High levels
of trace minerals in water (such as cobalt, copper, iron, man-
ganese, and selenium along with salty water [sodium chlo-
ride]) have a greater potential of contributing to both a toxic
level and a secondary standard aesthetic effect.
Fish
Metals are important natural components of the aquatic
environment for fish and other organisms. Aquatic environ-
ments encompass both freshwater (lakes, rivers, pond, wet-
lands) and saline (oceans, estuaries, salt lakes, and marshes)
conditions. These aquatic environments display a wide range
of thermal regimes (in temperate latitudes, for example, sea-
sonal thermal changes may be considerable, varying from
freezing to 30°C or more), pH, salinity, and other chemical
and physical characteristics. They are also influenced by the
type and density of organisms that are found or cultured in
these environments. A pond, for example, is a very different
aquatic environment from a river or ocean.
Salinity is a measure of the total amount of salt found in
water and is expressed as grams of salt per kg of water or parts
per thousand (ppt, %c). Freshwater salinity is usually less than
0.5 ppt. Water between 0.5 and 17 ppt is called brackish (e.g.,
estuaries, where river meets ocean). Seawater with salinity
ranging from 30 to 40 and > 40 ppt is classified as euryhaline
and hyperhaline, respectively. The dissolved ions (percentage
of total salt) that make the water saline include sodium, 55 .04
chlorine, 30.61; sulfate, 7.68; magnesium, 3.69; calcium, 1.16
potassium, 1.1; bicarbonate, 0.41; bromine, 0.19; borate, 0.07
strontium, 0.04; and fluorine, 0.003. Many of the ions found
in seawater throughout the world are in nearly constant pro-
portion despite the variation in total salinity. Freshwater dis-
charge from rivers, as well as evaporation and freezing, may
affect the salinity and concentration of various ions in seawa-
ter. Thus, the habitat of fish compared to terrestrial animals
can vary more since the aquatic environment is subject to pe-
riodic changes in dissolved oxygen, pH, temperature, salinity,
and mineral content.
Dissolved minerals in water can form complexes with
inorganic and organic ligands. These complexes show a wide
variation in their absorption by aquatic organisms. Some of
the inorganic anionic ligands in natural waters include F", CI",
SO4 2, OH
, and HCO3-2.
In oxic waters, CO3 ^,
HPO4-2 and
NH^j are important, whereas HS" and S are important in
anoxic water. Free ions are highly soluble and toxic to fish.
A direct correlation between the solubility of metal salts in
seawater and toxicity to marine organisms has been demon-
strated. Several elements such as vanadium, chromium,
nickel, copper, zinc, arsenic, tin, and selenium can be present
as environmental contaminants and at trace levels are toxic
to fish in both freshwater and marine environments.
Metals enter the hydrosphere from either natural pro-
cesses or through anthropogenic activities such as mining
operations, burning of fossil fuels, and agriculture. The solu-
bility of metals in natural waters depends upon the pH, type
and concentration of ligands and chelating agents, oxidation
states of the mineral components, and redox environment of
the system. The soluble forms are usually ions (simple or
complex) or nonionized organometallic chelates or com-
plexes. Aquatic organisms absorb and retain these metals
through the gills and body surfaces, and from ingestion of
water. Exchange of ions occurs across the gills, skin, and
oral epithelia in fish. Most aquatic organisms regulate the
metabolism of minerals in tissues within a relatively narrow
range except when the concentration reaches a nearly lethal
amount. Toxicity mechanisms include the blocking of es-
sential biological functional groups of enzymes, displace-
ment of essential ions in the biomolecule (enzyme or pro-
tein), and modification of the active conformation of the
biomolecule (Simkiss and Taylor, 1989). Sublethal effects
of several minerals on fish have been listed in individual
chapters.
FUTURE RESEARCH NEEDS
Water is the most critical essential nutrient for terrestrial
animals and fish. Water is never pure in nature, but is a mix-
ture of water and many dissolved or suspended minerals and
other particles. Our knowledge of how these dissolved or
suspended minerals affect animal or fish health and perfor-
mance is very limited. Modern analytical methods have pro-
vided information on concentrations of minerals found in
water, but future areas of research need to determine the
availability of these minerals and their contributions to the
metabolism of animals and fish. In addition, research is
needed to determine if animals have the same sensitivity to
the secondary water standards that are based on aesthetic
and cosmetic effects as do humans. Finally, research is
needed to determine if, and then to what degree, food-pro-
ducing animals can concentrate potentially toxic minerals
consumed through water in various tissues, especially tis-
sues commonly consumed by humans.
SUMMARY
The impact of any mineral or compound in water is dis-
cussed in the chapter on that individual mineral or com-
pound. Table 35-5 lists minerals and their common concen-
tration in fresh and salt water. It does not represent toxic
levels or any standards or recommended ranges of minerals,
but is presented as a quick tabulated reference for evaluation
of commonly reported ranges of minerals in water based on
the information presented in this book.
REFERENCES
Appelo, C. A. J., andD. Postma. 1999. Pp. I-12I in Geochemistry, Ground
water and Pollution. Rotterdam: Balkema.
Copyright © National Academy of Sciences. All rights reserved.
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inemi Tnlemnce nf Animals- Sennnd Revised Edition
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472 MINERAL TOLERANCE OF ANIMALS
Bowen, H. J. M. 1979. Pp. 22-23 in Environmental Chemistry of the Ele- NRC (National Research Council). 1974. Nutrients and Toxic Substances in
ments. London: Academic Press. Water for Livestock and Poultry. Washington D.C.: National Academy
Canadian Council of Ministers of the Environment. 1987. Canadian Water Press.
Quality Guidelines. Ottawa: Environment Canada, Water Quality Simkiss, K., and M. G. Taylor. 1989. Metal fluxes across the membranes of
Branch, Inland Waters Directorate. aquatic organisms. Rev. Aquat. Sci. 1:173-188.
EPA (U.S. Environmental Protection Agency). 2004. Drinking Water Con- Stumm, W., and J. J. Morgan. 1996. Pp. 1-10 and 256-305 in Aquatic Chem-
taminate List. Available at http://www.epa.gov/safewater. Accessed istry: Chemical Equilibria and Rates in Natural Waters. New York; John
April 18, 2004. Wiley and Sons.
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WATER AS A SOURCE OF TOXIC SUBSTANCES
473
TABLE 35-1 Sources and Normal Ranges of Minerals in
Unpolluted Fresh Water"
TABLE 35-2
Found in Sea
Range or Mean of Mineral Concentrations
Water"
Mineral
Concentration (mg/L)
Source
Na+
2.30^6.00
Feldspar, rock salt, zeolite,
atmosphere
K+
0.39-7.80
Feldspar, mica
Mg++
1.20^9.00
Dolomite, serpentine, pyroxene,
amfibole, olivine, mica
Ca++
2.00-200.00
Carbonate, gypsum, feldspar,
pyroxene, amfibole
CI
1.80-71.00
Rock salt, atmosphere
HCO,-
0.00-12.00
Carbonates, organic matter
SO42-
0.96^80.00
Atmosphere, gypsum, sulfides
NO3-
0.06-12.00
Atmosphere, organic matter
SiOj
1.20-60.00
Silicates
Fe++
0.00-28.00
Silicates, siderite, hydroxides,
sulfides
PO^-total
0.00-1.90
Organic matter, phosphates
"Appelo and Postma, 1999.
Mineral
mg/L
Aluminum
0.0001-0.0084
Ai'senic
0.0005-0.0037
Barium
0.002-0.063
Bismuth
0.000015-0.00002
Boron ^^^^^H
^H ^^^^^^H
Bromine
67.3
Cadmium
0.00001-0.0094
Calcium
412
Chloride ^^^H
^M ^^^^^^^^H
Chromium
0.0002-0.05
Cobalt ^1
^f ^^^B
Copper
0.00005-0.0121
Fluorine
1.30
Iron
0.00003-0.07
Lead ^^^B
^H ^^^^^H
Magnesium
1,290
Manganese ^^|
^y ^^^^^
Mercury
0.00001-0.00022
Molybdenum ^H
^ft ^^^^^^H
Nickel
0.00013-0.043
Phosphorus ^^M
^H 0.06-0.088
Potassium
399
^^^^^H
^M 0.000052-0.0002 ^^^^^H
Silicon
2.20-2.90
Salt (NaCl) ^M
^H ^^^H
Sulfur
905
Tin ^H
^B 0.000002-0.00081
Vanadium
0.0009-0.0025
^^^^^^^^1
^^1 ^^^^^H
Strontium
7.00-8.50
Uranium
0.00004-0.006
"Bowen, 1979.
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474
MINERAL TOLERANCE OF ANIMALS
TABLE 35-3
Sea Water"
Major Mineral Species Found in Fresh and
Condition
Element
Species
Hydrolyzed,
B3+
H^BO^, B(OH)j- ^^^^
anionic
V5+
H.VO,,- ^^^1
Cr6+
^^^H
As5+
^^^^^B
Se6+
^^^^^1
Mo6+
^^^^^H
Si4+
_^^^^^|
edominantl
y free
Li
Li+
aquo ions
Na
Na+
Mg
Mg2+, MgCO,
K
K+
Ca
Ca-+, CaSO^
Sr
Sr^*
Cs
Cs+
Ba
Ba2+
Complexation with
Be2+
BeOH+, Be(OH),
OH", COj^-,
A13+
Al(OH),, Al(OH),+, Al(OH)4-
HCO", cr
Ti4+
TiOj, Ti(OH)4
Mn4+
MNO,
Fe3+
Fe(OH)3, Fe(OH)2+, FeCOH)^-
Co2+
Co2+, CoCO, ^j
Ni2+
Ni^+, NiCO,, NiCl ^H
Cu2+
CuCO,, Cu{OH), ^H
Zn2+
Zn+^ ZnCO,, ZnCl ^H
Agl+
Ag+, AgCl ^M
Cd2+
Cd-+, CdCO,, CdCl, ^H
Hg2+
Hg(OH),, HgCl/- ^1
Pb2+
PbCO,, PbCl+, PbCO, ^M
Bi2+
Bi(OH), ^1
"Stumm and Morgan, 1996.
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WATER AS A SOURCE OF TOXIC SUBSTANCES
475
TABLE 35-4 Drinking Water Standards for Humans and Livestock
Chemical
(in mg/L)
Chemical
(in mg/L)
EPA - Human MCU'
NRC - Livestock''
Enforceable Standards
EPA - Human MCL°
NRC - Livestock''
Secondary Standards
Canadian - Livestock'"
"Maximum Contaminate Level (MCL), EPA, 2004.
''NRC, 1974.
'^Canadian Council of Ministries of the Environment, 1987.
Arsenic
0.01
0.2
0.5
Barium
2.0
Cadmium ^^^^^H
^H ■
^^P ^H
^P ^^^1
^^^1
Chromium
0.1
1.0
1.0
Cobalt
1.0
1.0
Copper
1.3
0.5
1.0 -cattle
0.5 - sheep
5.0 - swine
Lead
0.015
0.1
0.1
Mercury
0.002
0.001
0.003
Nitrate - nitrogen ^^M
^K 10.0 ^^^^^^1
^^^^^ 440 _^^^|
^^^^^^^^^^1
^^^1
Nitrite - nitrogen
1.0
33
10
Selenium
0.05
0.05
Canadian - Livestock''
Aluminum
0.2
5.0
Chlorine
250
Copper ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^1
Fluoride
2
2.0
2.0
Iron
0.3
Manganese
0.05
^^^^^H
^^B. °-^ ^^^1
^^^^^^^^B
^^^^^^^^^^^^^^B
Sulfate
250
1,000
Total dissolved solids
500 ^^^H
^^^Viii^^H
^^P ^^^^^^H
Vanadium
0.01
0.01
0.01
Zinc
5
25.0
25.0
pH
6.5-8.5
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476
MINERAL TOLERANCE OF ANIMALS
TABLE 35-5 Range or Mean of Mineral Concentrations
Found in Freshi and Salt Water"
Fresh Water
Salt Water
Mineral
mg/L
Aluminum
0.01-2.25
Arsenic
1-10
Barium
40-60 ^H
B
Bismuth
< 0.02 ^^^^
0.001
Boron ^^^|
^ < ^^^H
H ^H
Bromine
Cadmium
< 0.001
Calcium
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^1
Cobalt
Copper
0.001-0.02
0.015
Fluorine
0.02-1.5
1.2-1.5
Iodine
0.002-0.004 ^1
B 0.04-0.06
Iron
Lead
0.004
^
Magnesium
Manganese
^B
^^^^^^1
Mercury
0.001-0.003
0.0005-0.003
Molybdenum
0-0.004
0.008
Nickel __^^
0.01
Phosphorus ^^^^^|^^^^^^^^^^^^^^^^^^^^^^^|
Potassium
Selenium
0.001-0.003
0-0.001
Silicon
0.8-44
Salt (NaCl)
Sulfur
Tin
0.001-0.002
0.00025
Vanadium
< 0.003
< 0.003
Zinc
^^1
■ H
Strontium
<0.5
Uranium
0.028
Nitrate
"Compiled from information reviewed in this publication.
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About the Authors
Kirk C. Klasing, Ph.D., Chair, is professor in the Depart-
ment of Animal Science at tfie University of California,
Davis. His areas of expertise include poultry nutrition;
immunophysiology and disease resistance; immunologic
basis of stress; and nutrition and metabolic adaptation re-
quired by carnivorous, granivorous, and nectivorous animals.
Klasing received his Ph.D. in Nutritional Biochemistry from
Cornell University in 1982. He has previously served on the
NRC Subcommittee on Metabolism Modifiers and Nutrient
Requirements in Food-Producing Animals.
Jesse P. Goff, Ph.D., is veterinary medical officer within
the Mineral Metabolism and Mastitis Unit at the U.S. De-
partment of Agriculture's National Animal Disease Center
in Ames, Iowa. His research interests include the diseases of
mineral metabolism in domestic animals. Goff received his
undergraduate degree in Microbiology from Cornell Univer-
sity. At Iowa State University, he received his M.S. degree
in Veterinary Physiology, his D.V.M. degree, and his Ph.D.
degree in Veterinary and Nutritional Physiology. Goff has
received both the Griffith and the Holco Research Excel-
lence Awards. He was honored with the U.S. Department of
Agriculture's Midwest Area Early Career Scientist Award in
1991 and with the American Feed Industry Award for dairy
production in 1998. Dr. Goff also served as a committee
member on the NRC's revision of the Nutrient Requirements
of Dairy Cattle, Seventh Revised Edition, 2001.
Janet L. Greger, Ph.D., is vice-provost for Research and
Graduate Studies and dean of the Graduate School at the
University of Connecticut. Greger' s expertise is in macro-
mineral metabolism (particularly phosphorus, calcium, iron,
magnesium, copper, and zinc) in laboratory animals and ado-
lescents. She has additional expertise in mineral
bioavailability, trace mineral metabolism, and aluminum
toxicity. Greger received her Ph.D. in Human Nutrition in
1973 from Cornell University. She has previously served on
numerous NRC studies including the Committee on Cost and
Payment of Animal Research and Subcommittee on Labora-
tory Animal Nutrition.
Janet C. King, Ph.D., is a member of the Institute of Medi-
cine (1994) and serves as a senior scientist at the Children's
Hospital Oakland Research Institute. King's expertise is in
mineral metabolism in humans. Her research interests in-
clude zinc function, metabolism, and homeostasis, and cal-
cium and bone metabolism. King received her Ph.D. in Nu-
trition in 1972 from the University of California, Berkeley.
She currently serves on the NRC Board on Agriculture and
Natural Resources and has previously served on numerous
NRC committees including the Committee on Scientific
Evaluation of Dietary Intake References (Vice-Chair), Com-
mittee on Opportunities in the Nutrition and Food Sciences
(Vice-Chair), and Panel on Micronutrients.
Santosh P. Lall, Ph.D., is principal research officer in the
Institute of Marine Sciences at the National Research Coun-
cil of Canada. Lall's expertise is in phosphorus requirements
of freshwater and marine fish. He has additional expertise in
nutrient requirements of fresh- and saltwater salmonids. He
received his Ph.D. in Nutrition from theUniversity of Guelph
in 1973. Lall is currently chair of the International Union of
Nutritional Sciences Fish Nutrition Subcommittee and previ-
ously was a member of the NRC Committee on Fish Nutrition.
Xingen G. Lei, Ph.D., is associate professor in the Depart-
ment of Animal Science at Cornell University. Lei's exper-
tise is in the use of phytase to improve mineral (phosphorus,
calcium, iron, and zinc) nutrition in animals and humans.
Lei has additional expertise in the biochemistry, metabolism,
requirements, and bioavailability of selenium in swine and
mice. He received his Ph.D. in 1993 from Michigan State
University. In 1999, he was awarded the Outstanding Young
Scientist Award from the Northeastern Section American
Society of Animal Science and Northeast Branch American
Dairy Science Association.
477
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478
MINERAL TOLERANCE OF ANIMALS
James G. Linn, Ph.D., is professor and extension animal
scientist in dairy science at the Department of Animal Sci-
ence at the University of Minnesota. Linn's expertise is in
the impacts of the chemical composition of water on the
mineral intake of livestock, particularly dairy cattle. Linn
has additional expertise in copper toxicity in cattle and min-
eral balance in the transition cow. He received his Ph.D. in
Nutrition (Ruminant) from the University of Minnesota in
1978. Linn has previously served on the NRC Committee on
Nutrient Requirements of Dairy Cattle.
Forrest H. Nielsen, Ph.D., is nutritionist and past director
of the U.S. Department of Agriculture Grand Forks Human
Nutrition Research Center. Nielsen's expertise is in labora-
tory animal nutrition and trace element metabolism. Nielsen
received his Ph.D. in Biochemistry from the University of
Wisconsin in 1967. Nielsen served as a reviewer for the NRC
report Nutrient Requirements of Laboratory Animals, Fourth
Revised Edition.
Jerry W. Spears, Ph.D., is professor in the Department of
Animal Science at North Carolina State University. Spears'
expertise includes mineral metabolism in ruminants and
swine; role of minerals and other nutrients on immune re-
sponse and disease resistance; and bioavailability of trace
minerals. Spears received his Ph.D. in Animal Science (Nu-
trition) in 1978 from the University of Illinois, Urbana-
Champaign. He has previously served on the standing NRC
Committee on Animal Nutrition and its Subcommittee on
Beef Cattle Nutrition.
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Index
Absorption, 9. See also Regulation and
metabolism
Acid-base balance
and bicarbonate anions, 450
concentration of nonmetabolizable anions and
cations, 450^51
concentration of proteins in the blood, 45 1
determination of, 449^5 1
dietary minerals and acid-base physiology,
449^50
Acidosis. See Metabolic acidosis or alkalosis
Air, manganese in, 237
Alkalosis. See Metabolic acidosis or alkalosis
Aluminum, 15-30
concentrations in fluids and tissues of
animals, 30
effect of exposure in animals, 27-29
essentiality, 15
introduction, 15
methods of analysis and evaluation, 15-16
MTLs of, 22-23
regulation and metabolism, 16-17
research needed on, 23
sources and bioavailability, 17—19
summary, 23
tissue levels, 22
toxicosis, 19—22
Analysis. See Methods of analysis and evaluation
Animal excreta, environmental damage from
minerals in, 9
Animal health and well-being, new
understandings of appropriate indices
of, 1
Animal owners, 1
Animal wastes. See Disposal of municipal and
animal wastes; Recycled animal by-
products and wastes
Antimony, 428^29
metabolic interactions and mechanisms of
toxicity, 429
sources and metabolism, 428^29
tissue levels, 429
toxicosis and MTLs of, 429
Aquaculture industry, emergence of, 1
Aquatic animals and organisms
lead toxicosis in, 215
nitrates and nitrites toxicosis in, 457^58
research needed on MTLs of minerals in, 5
Aquatic food chain, bioconcentration of mercury
through, 2
Aquatic plants, accumulating iodine from
seawater to toxic levels, 7
Ai'senic, 31—45
becoming excessive in kidneys, 4
becoming excessive in liver, 4
causing oxidative damage to cellular
macromolecules, 3
concentrations in fluids and tissues of
animals, 45
effect of exposure in animals, 42—44
essentiality, 31-32
and human health, 37
introduction, 31
methods of analysis and evaluation, 32
MTLs of, 36-37
regulation and metabolism, 32-34
research needed on, 37
sources and bioavailability, 34—35
summary, 37
tissue levels, 36
toxicosis, 35-36
B
Barium, 46-53
concentrations in fluids and tissues of
animals, 53
effect of exposure in animals, 51-52
essentiality, 46
excessive intake from "protein-rich" foods, 1 1
and human health, 49
introduction, 46
methods of analysis and evaluation, 46
MTLs of, 48^9
regulation and metabolism, 46—47
research needed on, 49
sources and bioavailability, 47
summary, 49
tissue levels, 48
toxicosis, 47^8
Bicarbonate anions, 450
Bioavailability of minerals
of aluminum, 18-19
and calcium and magnesium, 19
and citric acid, 1 8
and iron, 19
and other organic acids and anions, 18
and silicates, 18—19
and speciation and solubility, 18
of arsenic, 34—35
of barium, 47
of bismuth, 55
of boron, 62
of bromine, 73
of cadmium, 81-82
of calcium, 99
of chromium, 117
of cobalt, 125-126
of copper, 136-137
at dietary levels near the MTL, 4
of fluorine, 157-158
of iodine, 185-186
of iron, 201-202
of lead, 212-213
of magnesium, 226
of manganese, 237-238
of mercury, 251-252
of molybdenum, 264
new information on, 1
of nickel, 278
of nitrates and nitrites, 455—456
of phosphorus, 292-293
of potassium, 308
of selenium, 324—326
of silicon, 350
of sodium chloride, 359-360
of sulfur, 374
of tin, 387-388
of vanadium, 399^00
of zinc, 415—416
Bioconcentration, of mercury through the aquatic
food chain, 2
479
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480
INDEX
Bismuth, 54-59
added to feeds, increasing potential for
toxicity, 7
becoming excessive in kidneys, 4
concentrations in fluids and tissues of
animals, 59
effect of exposure in animals, 58
essentiality, 54
introduction, 54
methods of analysis and evaluation, 54
MTLs of, 56
regulation and metabolism, 54—55
research needed on, 56
sources and bioavailability, 55
summary, 56
tissue levels, 56
toxicosis, 55—56
Bone
in aluminum toxicosis, metabolism of, 20
and calcium utilization in tin toxicosis, 389
fluorine becoming excessive in, 12
lead becoming excessive in, 12
in lead toxicosis, 215
Boron, 60-71
concentrations in fluids and tissues of
animals, 71
effect of exposure in animals, 68-70
essentiality, 60
and human health, 64
introduction, 60
methods of analysis and evaluation, 61
MTLs of, 64
regulation and metabolism, 61-62
research needed on, 64
sources and bioavailability, 62
summary, 64—65
tissue levels, 63-64
toxicosis, 62—63
Bromine, 72-78
added to feeds, increasing potential for
toxicity, 7
concentrations in fluids and tissues of
animals, 78
effect of exposure in animals, 77
essentiality, 72
and human health, 75
introduction, 72
methods of analysis and evaluation, 72
MTLs of, 74
regulation and metabolism, 72-73
research needed on, 75
sources and bioavailability, 73
summary, 75
tissue levels, 74
toxicosis, 73—74
Built-in safety factor, MTLs of not
including, 3
Cadmium, 79-96
accumulating, because not easily excreted,
3,9
accumulating to excessive levels in skeletal
muscle, 4
from application of municipal wastes to the
land, 2
becoming excessive in kidneys, 4
becoming excessive in liver, 4
becoming excessive in milk, 4
causing oxidative damage to cellular
macromolecules, 3
concentrations in fluids and tissues of
animals, 94—96
in the diets of humans and companion
animals, 1
effect of exposure in animals, 91-93
essentiality, 79
and human health, 86
introduction, 79
methods of analysis and evaluation, 79—80
MTLs of, 86
potential effects on crop yields in the
environment, 4
regulation and metabolism, 80-81
research needed on, 86
sources and bioavailability, 81-82
summary, 86-87
tissue levels, 85-86
toxicosis, 82-85
Calcium, 97-114
becoming excessive in kidneys, 12
concentrations in fluids and tissues of
animals, 1 14
effect of exposure in animals, 109—1 13
essentiality, 97-98
and human health
introduction, 97
and manganese, 237—238
methods of analysis and evaluation, 98
MTLs of, 104-105
and other minerals, in aluminum tox
icosis, 21
regulation and metabolism, 98-99
research needed on, 105-106
sources and bioavailability, 99
summary, 106
tissue levels, 103-104
toxicosis, 99-103
Carcinogenicity
in fluorine toxicosis, 161
in lead toxicosis, 215
in selenium toxicosis, 329
Cardiogenicity, in lead toxicosis, 214
Cation-anion difference, maximal tolerable
dietary, for animal health and
productivity, 451^52
Cats
effects of calcium exposure in, 109-1 10
effects of chromium exposure in, 121
effects of iodine exposure in, 194
effects of mercury exposure in, 259
effects of sulfur exposure in, 381
Cattle
aluminum concentrations in fluids and
tissues of, 30
arsenic concentrations in fluids and tissues
of, 45
bromine concentrations in fluids and tissues
of, 78
cadmium concentrations in fluids and
tissues of, 95
chromium concentrations in fluids and
tissues of, 123
copper concentrations in fluids and tissues
of, 153
effects of bromine exposure in, 77
effects of calcium exposure in, 109, 112-
113
effects of cobalt exposure in, 131
effects of copper exposure in, 149-150
effects of fluorine exposure in, 175-179
effects of iodine exposure in, 195
effects of magnesium exposure in, 232—233
effects of manganese exposure in, 244—245
effects of molybdenum exposure in, 271-
272
effects of nickel exposure in, 287
effects of potassium exposure in, 318-320
effects of selenium exposure in, 341
effects of sodium chloride exposure in,
367-370
effects of sulfur exposure in, 381, 383-384
effects of zinc exposure in, 425
fluorine concentrations in fluids and tissues
of, 181
lead concentrations in fluids and tissues of,
223
magnesium concentrations in fluids and
tissues of, 234
manganese concentrations in fluids and
tissues of, 247
mercury concentrations in fluids and tissues
of, 261
nickel concentrations in fluids and tissues
of, 289
phosphorus concentrations in fluids and
tissues of, 303-304
selenium concentrations in fluids and
tissues of, 346-347
sodium chloride concentrations in fluids
and tissues of , 37 1
zinc concentrations in fluids and tissues of,
426^27
Chemical form of minerals
microflora modifying, 9
in selenium toxicosis, and nutritional
nature, 330
Chickens
aluminum concentrations in fluids and
tissues of, 30
arsenic concentrations in fluids and tissues
of, 45
boron concentrations in fluids and tissues
of, 71
cadmium concentrations in fluids and
tissues of, 94
calcium concentrations in fluids and tissues
of, 114
cobalt concentrations in fluids and tissues
of, 133
copper concentrations in fluids and tissues
of, 153
effects of aluminum exposure in, 28
effects of arsenic exposure in, 42
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INDEX
481
effects of barium exposure in, 5 1
effects of bismutli exposure in, 58
effects of bromine exposure in, 77
effects of cadmium exposure in, 91—92
effects of calcium exposure in. 111
effects of chromium exposure in, 121—122
effects of cobalt exposure in, 130—131
effects of copper exposure in, 147-148
effects of fluorine exposure in, 170-173
effects of iodine exposure in, 194—195
effects of iron exposure in, 208
effects of lead exposure in, 22 1
effects of magnesium exposure in, 232-233
effects of manganese exposure in, 243—244
effects of mercury exposure in, 259
effects of molybdenum exposure in, 271
effects of nickel exposure in, 286
effects of phosphorus exposure in, 301
effects of potassium exposure in, 317—318
effects of selenium exposure in, 339
effects of sodium chloride exposure in, 367,
369
effects of sulfur exposure in, 381-382
effects of tin exposure in, 396
effects of vanadium exposure in, 407^08
effects of zinc exposure in, 423^24
fluorine concentrations in fluids and tissues
of 181
iodine concentrations in fluids and tissues
of, 198
iron concentrations in fluids and tissues of,
209
lead concentrations in fluids and tissues
of 223
magnesium concentrations in fluids and
tissues of, 234
manganese concentrations in fluids and
tissues of, 247
mercury concentrations in fluids and tissues
of 261
molybdenum concentrations in fluids and
tissues of, 274
nici^el concentrations in fluids and tissues
of, 288
phosphorus concentrations in fluids and
tissues of, 303
selenium concentrations in fluids and
tissues of, 344-345
sodium chloride concentrations in fluids
and tissues of, 371
vanadium concentrations in fluids and
tissues of, 411
zinc concentrations in fluids and tissues
of, 426
Chromium, 115—123
becoming excessive in kidneys, 4
causing oxidative damage to cellular
macromolecules, 3
concentrations in fluids and tissues of
animals, 123
effect of exposure in animals, 121-122
essentiality, 115-116
introduction, 115
methods of analysis and evaluation, 116
MTLsof 118-119
regulation and metabolism, 116-117
research needed on, 119 in mice, 71
sources and bioavailability, 1 17 in rats, 71
summary, 119 of bromine, 78
tissue levels, 118 in cattle, 78
toxicosis, 117-118 in dogs, 78
Cobalt, 124-133 in rats, 78
becoming excessive in kidneys, 4 of cadmium, 94—96
causing oxidative damage to cellular in cattle, 95
macromolecules, 3 in chickens, 94
concentrations in fluids and tissues of in cows, 95
animals, 133 in ducks, 94
effect of exposure in animals, 130—132 in fish, 95—96
essentiality, 124 in goats, 95
introduction, 124 in pigs, 94
methods of analysis and evaluation, 124— in quail, 94
125 in sheep, 95
MTLsof 127 of calcium, 1 14
regulation and metabolism, 125 in chickens, 114
research needed on, 127-128 in cows, 114
sources and bioavailability, 125-126 in fish, 114
summary, 128 in pigs, 114
tissue levels, 127 in sheep, 114
toxicosis, 126-127 of chromium, 123
Committee on Animal Nutrition, 1-2 in cattle, 123
Companion animals in pigs, 123
cadmium in the diets of, 1 in rats, 123
lead in the diets of, 1 in turkeys, 123
mercury in the diets of, 1 of cobalt, 133
research needed on MTLs of minerals in, 5 in chickens, 133
Compensated metabolic acidosis or alkalosis, in pigs, 133
in chronic mineral and acid-base in rats, 133
balance toxicosis, 451 in sheep, 133
Concentrations of copper, 153
of nonmetabolizable anions and cations, in cattle, 153
450^51 in chickens, 153
of proteins in the blood, 451 in fish, 153
Concentrations in fluids and tissues in pigs, 153
of aluminum, 30 in rabbits, 153
in cattle, 30 in sheep, 153
in chickens, 30 of fluorine, 181
in humans, 30 in cattle, 181
in mice, 30 in chickens, 181
in rats, 30 in cows, 181
in sheep, 30 in humans, 1 8 1
of arsenic, 45 in sheep, 181
in cattle, 45 of iodine, 198
in chickens, 45 in chickens, 198
in ducks, 45 in cows, 198
in fish, 45 in goats, 198
in goats, 45 in sheep, 198
in humans, 45 of iron, 209
in pigs, 45 in chickens, 209
in rats, 45 in cows, 209
of barium, 53 in fish, 209
in rats, 53 in sheep, 209
in sheep, 53 of lead, 223
of bismuth, 59 in cattle, 223
in dogs, 59 in chickens, 223
in rabbits, 59 in horses, 223
in rats, 59 in pigs, 223
of boron, 71 in sheep, 223
in chickens, 71 of magnesium, 234
in cows, 71 in cattle, 234
in ducks, 71 in chickens, 234
in fish, 71 in cows, 234
in humans, 71 in fish, 234
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in pigs, 234
in slieep, 234
of manganese, 247
in cattle, 247
in ctiickens, 247
in slieep, 247
of mercury, 261
in cattle, 261
in chickens, 261
in ducks, 26 1
in fish, 261
in goats, 261
in pigs, 261
in sheep, 261
of molybdenum, 274—275
in chickens, 274
in cows, 274
in rats, 274
in sheep, 275
of nickel, 288-289
in cattle, 289
in chickens, 288
in ducks, 288
in fish, 289
in goats, 289
in horses, 288
in humans, 288
in mice, 288
in pigs, 288
in rats, 288
in sheep, 289
of phosphorus, 303-305
in cattle, 303-304
in chickens, 303
in cows, 304
in fish, 305
in goats, 304
in horses, 303
in rats, 303
in sheep, 304
in swine, 303
of selenium, 344-347
in cattle, 346-347
in chickens, 344-345
in cows, 346-347
in hamsters, 344-345
in monkeys, 344—345
in pigs, 344-347
in rats, 344-345
in sheep, 346-347
in turkeys, 344-345
of silicon, 356
in horses, 356
in humans, 356
in monkeys, 356
in rats, 356
in sheep, 356
of sodium chloride, 371
in cattle, 371
in chickens, 371
in fish, 371
in pigs, 371
in sheep, 371
of sulfur, 385
in sheep, 385
of tin, 397
in fish, 397
in humans, 397
in rats, 397
of vanadium, 410^12
in chickens, 411
in mice, 410
in rats, 410, 412
in sheep, 411^12
of zinc, 426^27
in cattle, 426-427
in chickens, 426
in cows, 427
in fish, 427
in pigs, 426
in sheep, 427
Concern for toxicosis, levels of, 4
Contaminating minerals, potentially toxic
levels in mineral supplements, 2, 7
Copper, 134-153
added to feeds, increasing potential for
toxicity, 7
in animal excreta, causing environmental
damage, 9
from application of municipal wastes to the
land, 2
becoming excessive in liver, 4
causing oxidative damage to cellular
macromolecules, 3
concentrations in fluids and tissues of
animals, 153
effect of exposure in animals, 147—152
essentiality, 134
and human health, 143
introduction, 134
methods of analysis and evaluation,
134-135
MTLs of, 142-143
potential effects on crop yields in the
environment, 4
regulation and metabolism, 135-136
research needed on, 143
sources and bioavailability, 136-137
summary, 143
tissue levels, 142
toxicosis, 137-142
utilization of, and hematological status in
tin toxicosis, 388-389
Cows
boron concentrations in fluids and tissues
of, 71
cadmium concentrations in fluids and
tissues of, 95
calcium concentrations in fluids and tissues
of, 1 14
effects of boron exposure in, 69
effects of cadmium exposure in, 92
effects of fluorine exposure in, 175
effects of iodine exposure in, 195-196
effects of iron exposure in, 208
effects of lead exposure in, 221-222
effects of phosphorus exposure in, 302
effects of potassium exposure in, 318-319
effects of silicon exposure in, 355
effects of zinc exposure in, 424-425
fluorine concentrations in fluids and tissues
of, 181
iodine concentrations in fluids and tissues
of, 198
iron concentrations in fluids and tissues
of, 209
magnesium concentrations in fluids and
tissues of, 234
molybdenum concentrations in fluids and
tissues of, 274
phosphorus concentrations in fluids and
tissues of, 304
selenium concentrations in fluids and
tissues of, 346-347
zinc concentrations in fluids and tissues
of, 427
Croplands, increasing disposal of municipal
and animal wastes on, 1
Crops, nitrates and nitrites in, 455
Cysteine toxicity, and sulfur toxicosis, 376
Dibutyltin toxicosis, 391
Dietary conditions, in selenium toxicosis, 330
Dietary exposure, chronic, to inorganic
manganese, 238-239
Dietary minerals, and acid-base physiology,
449-450
Dietary sources
of aluminum, 17
of manganese, 237
of zinc, 415
Diorganotin compounds, additional side
effects in tin toxicosis, 391
Disposal of municipal and animal wastes, on
croplands and pastures, increasing, 1-
2
DM. See Dry matter basis
Dogs
bismuth concentrations in fluids and tissues
of, 59
bromine concentrations in fluids and tissues
of, 78
effects of aluminum exposure in, 27
effects of arsenic exposure in, 42
effects of bismuth exposure in, 58
effects of boron exposure in, 68
effects of bromine exposure in, 77
effects of cadmium exposure in, 9 1
effects of calcium exposure in, 1 10-1 1 1
effects of chromium exposure in, 121
effects of copper exposure in, 147
effects of fluorine exposure in, 169
effects of iodine exposure in, 194
effects of lead exposure in, 221
effects of mercury exposure in, 259
effects of nickel exposure in, 284
effects of phosphorus exposure in. 300
effects of silicon exposure in, 355
effects of sodium chloride exposure in, 367
effects of sulfur exposure in, 381
Drinking water standards, for humans and
livestock, 475
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Dry matter (DM) basis, mineral concentrations
expressed on, 8
Ducks
arsenic concentrations in fluids and tissues
of, 45
boron concentrations in fluids and tissues
of, 71
cadmium concentrations in fluids and
tissues of, 94
effects of arsenic exposure in, 43
effects of bismuth exposure in, 58
effects of boron exposure in, 69
effects of cadmium exposure in, 92
effects of copper exposure in, 148-149
effects of lead exposure in, 22 1
effects of mercury exposure in, 259
effects of nickel exposure in, 286
effects of selenium exposure in, 339
effects of sodium chloride exposure in, 369
mercury concentrations in fluids and tissues
of, 261
nickel concentrations in fluids and tissues
of, 288
Environmental damage, from minerals in
animal excreta, 9
Environmental exposure
to potassium, 308
to vanadium, 399^00
Environmental health, 4
and human health, 9
Environmental quality, impact of minerals
on, 1
Essentiality, 2
of aluminum, 15
of arsenic, 31-32
of barium, 46
of bismuth, 54
of boron, 60
of bromine, 72
of cadmium, 79
of calcium, 97-98
of chromium, 115-116
ofcobah, 124
of copper, 134
of fluorine, 154-155
of iodine, 182-183
of iron, 199-200
of lead, 210
of magnesium, 224—225
of manganese, 235
of mercury, 248
of molybdenum, 262—263
of nickel, 276-277
of nitrates and nitrites, 453
of phosphorus, 290
of potassium, 306—307
of selenium, 322
of silicon, 348-349
of sodium chloride, 357
of sulfur, 372-373
of tin, 386
of vanadium, 398-399
of zinc, 413
Evaluation. See Methods of analysis and
evaluation
Excretion pathways, 9. See also Regulation
and metabolism
Exposure, 2, 7-8
to aluminum, 27—29
effects on chickens, 28
effects on dogs, 27
effects on fish, 29
effects on freshwater bivalves, 29
effects on humans, 27
effects on mice, 27
effects on monkeys, 27
effects on rabbits, 27
effects on rats, 27-28
effects on sheep, 29
effects on turkeys, 29
to arsenic, 42^14
effects on chickens, 42
effects on dogs, 42
effects on ducks, 43
effects on fish, 43^4
effects on mice, 42
effects on pigs, 43
effects on rabbits, 42
effects on rats, 42
effects on sheep, 43
to barium, 51—52
effects on chickens, 5 1
effects on horses, 5 1
effects on mice, 52
effects on rats, 51—52
effects on swine, 5 1
to bismuth, 58
effects on chickens, 58
effects on dogs, 58
effects on ducks, 58
effects on pigs, 58
to boron, 68-70
effects on cows, 69
effects on dogs, 68
effects on ducks, 69
effects on fish, 69-70
effects on mice, 68
effects on rats, 68-69
to bromine, 77
effects on cattle, 77
effects on chickens, 77
effects on dogs, 77
effects on rats, 77
effects on swine, 77
to cadmium, 91-93
effects on chickens, 91-92
effects on cows, 92
effects on dogs, 9 1
effects on ducks, 92
effects on fish, 93
effects on goats, 92
effects on mice, 9 1
effects on monkeys, 91
effects on pigs, 92
effects on quail, 92
effects on rats, 9 1
effects on sheep, 93
to calcium, 109-113
effects on cats, 109-110
effects on cattle, 109, 1 12-113
effects on chickens. 111
effects on dogs, 1 10-1 1 1
effects on fish, 113
effects on horses, 112
effects on pigs, 109, 112
effects on rats. 111
effects on turkeys, 112
to chromium, 121-122
effects on cats, 121
effects on chickens, 121-122
effects on dogs, 121
effects on fish, 122
effects on mice, 121
effects on prawns, 122
effects on rats, 121
effects on swine, 122
effects on turkeys, 122
to cobalt, 130-132
effects on cattle, 131
effects on chickens, 130-131
effects on mice, 130
effects on rabbits, 130
effects on rats, 130
effects on sheep, 132
effects on swine, 131
to copper, 147-152
effects on cattle, 149-150
effects on chickens, 147-148
effects on dogs, 147
effects on ducks, 148-149
effects on fish, 151-152
effects on goats, 1 50
effects on horses, 149
effects on mice, 147
effects on rabbits, 147
effects on rats, 147
effects on sheep, 150-151
effects on swine, 149
effects on turkeys, 148
by feed, and zinc toxicosis, 416^15
to fluorine, 169-180
effects on cattle, 175-179
effects on chickens, 170-173
effects on cows, 175
effects on dogs, 169
effects on fish, 179-180
effects on pigs, 173—174
effects on rats, 169-170
effects on sheep, 179
effects on turkeys, 173
to iodine, 194-197
effects on cats, 194
effects on cattle, 195
effects on chickens, 194—195
effects on cows, 195-196
effects on dogs, 194
effects on fish, 197
effects on guinea pigs, 194
effects on hamsters, 194
effects on horses, 196
effects on mice, 194
effects on pigs, 196
effects on rabbits, 194
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effects on rats, 1 94
effects on sheep, 196-197
effects on turkeys, 195
to iron, 208
effects on chickens, 208
effects on cows, 208
effects on fish, 208
effects on horses, 208
effects on sheep, 208
effects on swine, 208
to lead, 221-222
effects on chickens, 221
effects on cows, 221-222
effects on dogs, 221
effects on ducks, 221
effects on fish, 222
effects on pigs, 221
effects on quail, 22 1
to magnesium, 232-233
effects on cattle, 232-233
effects on chickens, 232-233
effects on horses, 232-233
effects on mice, 232
to manganese, 243—246
effects on cattle, 244-245
effects on chickens, 243-244
effects on fish, 245-246
effects on guinea pigs, 243
effects on rabbits, 243
effects on rats, 243
effects on sheep, 245
effects on swine, 244
effects on turkeys, 244
organic forms of, 239-240
to mercury, 259—260
effects on cats, 259
effects on chickens, 259
effects on dogs, 259
effects on ducks, 259
effects on fish, 260
effects on goats, 260
effects on quail, 259
methods of reporting, 8
to molybdenum, 271—273
effects on cattle, 271-272
effects on chickens, 271
effects on fish, 273
effects on goats, 273
effects on horses, 27 1
effects on rabbits, 27 1
effects on rats, 27 1
effects on sheep, 272
effects on swine, 271
to nickel, 284-287
effects on cattle, 287
effects on chickens, 286
effects on dogs, 284
effects on ducks, 286
effects on fish, 287
effects on mice, 284
effects on pigs, 287
effects on rats, 285-286
to phosphorus, 300—302
effects on chickens, 301
effects on cows, 302
effects on dogs, 300
effects on fish, 302
effects on guinea pigs, 301
effects on horses, 302
effects on mice, 300
effects on rabbits, 300
effects on rats, 300-301
effects on sheep, 302
effects on swine, 301
to potassium, 314—320
effects on cattle, 318-320
effects on chickens, 317-318
effects on cows, 318-319
effects on goats, 320
effects on mice, 314
effects on rats, 314—317
to selenium, 337—343
effects on cattle, 341
effects on chickens, 339
effects on ducks, 339
effects on fish, 343
effects on goats, 342
effects on hamsters, 338
effects on mice, 337—338
effects on rats, 338
effects on sheep, 342-343
effects on swine, 339-340
to silicon, 355
effects on cows, 355
effects on dogs, 355
effects on mice, 355
effects on rats, 355
effects on sheep, 355
effects on turkeys, 355
to sodium chloride, 367-370
effects on cattle, 367-370
effects on chickens, 367, 369
effects on dogs, 367
effects on ducks, 369
effects on horses, 369
effects on rats, 367
effects on sheep, 370
effects on swine, 367-368
effects on turkeys, 368-369
to sulfur, 381-384
effects on cats, 381
effects on cattle, 381, 383-384
effects on chickens, 381-382
effects on dogs, 381
effects on horses, 381
effects on pigs, 382
effects on sheep, 384
to tin, 395-396
effects on chickens, 396
effects on fish, 396
effects on humans, 395
effects on rats, 395-396
to vanadium, 405-409
effects on chickens, 407^08
effects on mice, 405
effects on rats, 405^07
effects on sheep, 409
by water
to inorganic manganese, 239
in zinc toxicosis, 418
to zinc, 423^25
effects on cattle, 425
effects on chickens, 423^24
effects on cows, 424-425
effects on fish, 425
effects on sheep, 425
FDA. See Food and Drug Administration
Feed consumption, rate of, 9
Feedstuffs
a common source of potentially toxic levels
of minerals, 2
safeguarding, 1
Fish
aluminum toxicosis in, 21—22
arsenic concentrations in fluids and tissues
of, 45
boron concentrations in fluids and tissues
of, 71
cadmium concentrations in fluids and
tissues of, 95-96
calcium concentrations in fluids and tissues
of, 1 14
chronic toxicosis from selenium in, 328
copper concentrations in fluids and tissues
of, 153
effects of aluminum exposure in, 29
effects of arsenic exposure in, 43-44
effects of boron exposure in, 69-70
effects of cadmium exposure in, 93
effects of calcium exposure in, 113
effects of chromium exposure in, 122
effects of copper exposure in, 151-152
effects of fluorine exposure in, 179-180
effects of iodine exposure in, 197
effects of iron exposure in, 208
effects of lead exposure in, 222
effects of manganese exposure in, 245-246
effects of mercury exposure in, 260
effects of molybdenum exposure in, 273
effects of nickel exposure in, 287
effects of phosphorus exposure in, 302
effects of selenium exposure in, 343
effects of tin exposure in, 396
effects of zinc exposure in, 425
iron concentrations in fluids and tissues
of, 209
magnesium concentrations in fluids and
tissues of, 234
mercury concentrations in fluids and tissues
of, 12, 261
and minerals and toxic substances in water,
471
nickel concentrations in fluids and tissues
of, 289
phosphorus concentrations in fluids and
tissues of, 305
sodium chloride concentrations in fluids
and tissues of, 371
tin concentrations in fluids and tissues of,
397
zinc concentrations in fluids and tissues
of, 427
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Fish ingestion, children exposed to
methylmercury in utero, from
maternal, 1 1
Fishmeals, high in mercury, 2, 7
Fluorine, 154-181
in aluminum toxicosis, utilization of, 20-21
becoming excessive in bone, 12
becoming excessive in kidneys, 4
concentrations in fluids and tissues of
animals, 181
effect of exposure in animals, 169-180
essentiality, 154—155
excessive intake from "protein-rich"
foods, 11
and human health, 162
introduction, 154
likely to reach toxic levels in natural water
supplies, 2, 7
methods of analysis and evaluation, 155
MTLs of, 162-163
regulation and metabolism, 156-157
research needed on, 163
sources and bioavailability, 157-158
summary, 163—164
tissue levels, 162
toxicosis, 158-159
Food. See also Feedstuffs
nitrates and nitrites in, 455^56
Food and Agriculture OrganizationAVorld
Health Organization (FAOAVHO)
Pesticide committee, 1 1
Food and Drug Administration (FDA), 1
concerns about minerals in animal
products, 12
Food and Nutrition Board, 4, 14
Freshwater bivalves, effects of aluminum
exposure in, 29
Gastrointestinal symptoms
in lead toxicosis, 214
in tin toxicosis, 388
Genotoxicity, in fluorine toxicosis, 161
Germanium, 429^31
metabolic interactions and mechanisms of
toxicity, 430
sources and metabolism, 430
tissue levels, 431
toxicosis and MTLs of, 430^31
Goats
arsenic concentrations in fluids and tissues
of, 45
cadmium concentrations in fluids and
tissues of, 95
effects of cadmium exposure in, 92
effects of copper exposure in, 150
effects of mercury exposure in, 260
effects of molybdenum exposure in, 273
effects of potassium exposure in, 320
effects of selenium exposure in, 342
iodine concentrations in fluids and tissues
of, 198
mercury concentrations in fluids and tissues
of, 261
nickel concentrations in fluids and tissues
of, 289
phosphorus concentrations in fluids and
tissues of, 304
Government regulators, 1
Growth
and longevity in aluminum toxicosis, 19-20
and zinc utilization in tin toxicosis. 388
Guinea pigs
effects of iodine exposure in, 194
effects of manganese exposure in, 243
effects of phosphorus exposure in, 301
H
Hamsters
effects of iodine exposure in, 194
effects of selenium exposure in, 338
selenium concentrations in fluids and
tissues of, 344-345
Heavy metals, in animal excreta, causing
environmental damage, 9
Hematological changes, in lead toxicosis,
213-214
Hematological status, and iron, copper, and
selenium utilization in tin toxicosis,
388-389
Homeostasis
acid/base, minerals disturbing, 3
new information on, 1
Horses
chronic toxicosis from selenium in, 327
effects of barium exposure in, 51
effects of calcium exposure in, 112
effects of copper exposure in, 149
effects of iodine exposure in, 196
effects of iron exposure in, 208
effects of magnesium exposure in,
232-233
effects of molybdenum exposure in, 271
effects of phosphorus exposure in, 302
effects of sodium chloride exposure in. 369
effects of sulfur exposure in, 381
lead concentrations in fluids and tissues
of, 223
nickel concentrations in fluids and tissues
of, 288
phosphorus concentrations in fluids and
tissues of, 303
silicon concentrations in fluids and tissues
of, 356
Human health, 4-5, 11-12
and arsenic, 37
and barium, 49
and boron, 64
and bromine, 75
and cadmium, 86
and copper, 143
and fluorine, 162
and iodine, 189-190
and iron, 205
and lead, 217-218
maximum exposure to minerals from
consumption of animal products,
11-12
and mercury, 255-256
method for identifying minerals of concern
for, 11
Humans
aluminum concentrations in fluids and
tissues of, 30
arsenic concentrations in fluids and tissues
of, 45
boron concentrations in fluids and tissues
of, 71
cadmium in the diets of, 1
effects of aluminum exposure in, 27
effects of tin exposure in, 395
fluorine concentrations in fluids and tissues
of, 181
lead in the diets of, 1
mercury in the diets of, 1
nickel concentrations in fluids and tissues
of, 288
selenium toxicosis in. 329
silicon concentrations in fluids and tissues
of, 356
tin concentrations in fluids and tissues
of, 397
toxicity assessments of nutrients for, 14
toxicological standards for minerals in, 1 1
I
Immunological effects, in lead toxicosis, 214—
215
Industrial wastes, introducing minerals into
water supplies. 7
Inhalation exposure, to inorganic manganese,
239
Inorganic manganese
chronic dietary exposure to, 238-239
inhalation exposure to, 239
intravenous exposure to, 239
in water, exposure to, 239
Inorganic mercury
acute toxicosis from, 252-253
chronic toxicosis from, 253
MTLs of, 255
toxicosis from single doses of, 252
Inorganic tin, in tin toxicosis, 388
Intravenous exposure, to inorganic manganese,
239
Iodine, 182-198
becoming excessive in milk, 4, 12
concentrations in fluids and tissues of
animals, 198
effect of exposure in animals, 194—197
essentiality, 182-183
and human health, 189-190
introduction, 182
methods of analysis and evaluation, 1 83-1 84
MTLs of. 189
regulation and metabolism, 184—185
research needed on, 190
from seawater, aquatic plants accumulating
to toxic levels, 7
sources and bioavailability, 185-186
summary, 190
tissue levels, 189
toxicosis, 186-189
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Iron, 199-209
causing oxidative damage to cellular
macromolecules, 3
concentrations in fluids and tissues of
animals, 209
effect of exposure in animals, 208
essentiality, 199-200
and human health, 205
introduction, 199
likely to reach toxic levels in natural water
supplies, 7
and manganese, 238
methods of analysis and evaluation, 200
MTLs of, 205
possibly becoming excessive in liver, 4
potential effects on crop yields in the
environment, 4
regulation and metabolism, 200-201
research needed on, 205
sources and bioavailability, 201-202
summary, 205—206
tissue levels, 205
toxicosis, 202-205
utilization of, and hematological status in
tin toxicosis, 388-389
Kidneys
calcium becoming excessive in, 12
minerals becoming excessive in, 4, '
Laboratory animals, chi'onic toxicosis from
selenium in, 328
Lead, 210-223
accumulating to excessive levels in skeletal
muscle, 4
affecting development of complex
biological systems of the brain and
immune system, 9
from application of municipal wastes to the
land, 2
becoming excessive in bone, 12
becoming excessive in kidneys, 4
becoming excessive in liver, 4
becoming excessive in milk, 4
causing oxidative damage to cellular
macromolecules, 3
concentrations in fluids and tissues of
animals, 223
in the diets of humans and companion
animals, 1
effect of exposure in animals, 221-222
essentiality, 210
and human health, 217-218
introduction, 210
methods of analysis and evaluation, 210—211
MTLs for adjusted in 1980 report, 3
MTLs of, 217
regulation and metabolism, 211-212
research needed on, 218
sources and bioavailability, 212-213
summary, 218
tissue levels, 217
toxicosis, 213-217
Levels. See Maximum tolerable levels of
toxicity; Tissue levels
Literature
historic, reanalysis of, 2
in peer-reviewed journal publications, 2
Lithium, 431^32
metabolic interactions and mechanisms of
toxicity, 432
sources and metabolism, 431^32
tissue levels, 432
toxicosis and MTLs of, 432
Liver, minerals becoming excessive in, 4, 9
Lowest-observed-adverse-effect levels
(LOAEL), 11
M
Magnesium, 224-234
concentrations in fluids and tissues of
animals, 234
effect of exposure in animals, 232—233
essentiality, 224-225
introduction, 224
likely to reach toxic levels in natural water
supplies, 7
methods of analysis and evaluation, 225
MTLs of, 229-230
regulation and metabolism, 225-226
research needed on, 230
sources and bioavailability, 226
summary, 230
tissue levels, 228-229, 234
toxicosis, 226-228
Manganese, 235—247. See also Inorganic
manganese; Organic manganese
concentrations in fluids and tissues of
animals, 247
effect of exposure in animals, 243—246
essentiality, 235
introduction, 235
likely to reach toxic levels in natural water
supplies, 2
methods of analysis and evaluation, 235
MTLs of, 240
regulation and metabolism, 235-237
research needed on, 240
sources and bioavailability, 237-238
summary, 240
tissue levels, 240
toxicosis, 238-240
Maximum tolerable levels (MTLs) of toxicity,
3^
of aluminum, 22-23
of antimony, 429
of arsenic, 36—37
of barium, 48^9
bioavailability of minerals at dietary levels
near, 5
of bismuth, 56
acute, 56
chronic, 56
via water, 56
of boron, 64
of bromine, 74
of cadmium, 86
of calcium, 104-105
acute, 104
chronic, 104-105
single dose, 104
of chromium, 118-119
of cobalt, 127
of copper, 142-143
in the feed of animals, 13-14
of fluorine, 162-163
of germanium, 430^3 1
in human health, 1 1—12
maximum exposure to minerals from
consumption of animal products, 1 1-
12
toxological standards for minerals in
humans, 11
of iodine, 189
of iron, 205
of lead, 217
of lithium, 432
of magnesium, 229—230
acute, 229
chronic, 229-230
single oral dose, 229
of manganese, 240
of mercury, 255
of minerals, 10-14
of minerals in the feed of animals, 13-14
of molybdenum, 267-268
of nickel, 279-280
of nitrates and nitrites, 458
not including a built-in safety factor, 3
of phosphorus, 295
of potassium, 311
of rare earths, 433^34
of mbidium, 435
of selenium, 331-332
of silicon, 351—352
of silver, 436^37
of sodium chloride, 363—364
of strontium, 438^39
of sulfur, 378-379
of tin, 391-392
of titanium, 439
of tungsten, 440^441
of uranium, 442^143
of vanadium, 402
of zinc, 419
Mechanisms of toxicity, 3
of antimony, 429
of arsenic, 34
of boron, 61—62
of cadmium, 8 1
of chromium, 116-117
of cobalt, 125
of copper, 135-136
of fluorine, 157
of germanium, 430
of iodine, 184-185
of iron, 201
of lead, 212
of lithium, 432
of mercury, 250-251
of molybdenum, 263-264
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new information on, 1
of niciiel, 277-278
of pliospliorus, 292
of rare earths, 433
of rubidium, 434-435
of selenium, 324
of silicon, 349-350
of silver, 436
of strontium, 438
of titanium, 439
of tungsten, 440
of uranium, 442
of zinc, 415
Mercury, 248—261. See also Inorganic
mercury; Methylmercury; Organic
mercury
accumulating, because not easily excreted,
3,9
accumulating to excessive levels in skeletal
muscle, 4
affecting development of complex
biological systems of the brain and
immune system, 9
becoming excessive in kidneys, 4
becoming excessive in liver, 4
becoming excessive in milk, 4
bioconcentration of through the aquatic
food chain, 2, 12
causing oxidative damage to cellular
macromolecules, 3
concentrations in fluids and tissues of
animals, 261
in the diets of humans and companion
animals, 1
effect of exposure in animals, 259-260
essentiality, 248
and human health, 255-256
introduction, 248
methods of analysis and evaluation, 249
MTLs of, 255
adjusted from 1980 report, 3
potential effects on crop yields in the
environment, 4
regulation and metabolism, 249-251
research needed on, 256
sources and bioavailability, 251-252
summary, 256
tissue levels, 255
toxicosis, 252-255
Metabolic interactions. See also Regulation
and metabolism
acidosis or alkalosis
compensated, in chronic mineral and
acid-base balance toxicosis, 451
uncompensated, in acute mineral and
acid-base balance toxicosis, 451
of antimony, 429
of arsenic, 33-34
of boron, 61
of chromium, 116-117
of cobalt, 125
of copper, 135-136
of fluorine, 157
of germanium, 430
of iodine, 184-185
of iron, 200-201
of lithium, 432
of molybdenum, 263-264
of nickel, 277-278
of phosphorus, 292
of potassium, 307-308
of rare earths, 433
of rubidium, 434-435
of selenium, 324
of silicon, 349-350
of silver, 436
of strontium, 438
of titanium, 439
of tungsten, 440
of uranium, 442
of vanadium, 399
of zinc, 415
Methionine toxicity, and sulfur toxicosis, 376-
378
Methods of analysis and evaluation
for aluminum, 15—16
for arsenic, 32
for barium, 46
for bismuth, 54
for boron, 6 1
for bromine, 72
for cadmium, 79-80
for calcium, 98
for chromium, 116
for cobalt, 124-125
for copper, 134—135
for fluorine, 155
for iodine, 183-184
for iron, 200
for lead, 210-211
for magnesium, 225
for manganese, 235
for mercury, 249
for molybdenum, 263
for nickel, 277
for nitrates and nitrites, 453^54
for phosphorus, 290-291
for potassium, 307
for selenium, 322-323
for silicon, 349
for sodium chloride, 357-358
for sulfur, 373
for tin, 386
for vanadium, 399
for zinc, 413^14
Methylmercury, children exposed to in utero,
from maternal fish ingestion, 1 1
Mice
aluminum concentrations in fluids and
tissues of, 30
boron concentrations in fluids and tissues
of, 71
effects of aluminum exposure in, 27
effects of arsenic exposure in, 42
effects of barium exposure in, 52
effects of boron exposure in, 68
effects of cadmium exposure in, 9 1
effects of chromium exposure in, 121
effects of cobalt exposure in, 130
effects of copper exposure in, 147
effects of iodine exposure in, 194
effects of magnesium exposure in, 232
effects of nickel exposure in, 284
effects of phosphorus exposure in, 300
effects of potassium exposure in, 314
effects of selenium exposure in, 337-338
effects of silicon exposure in, 355
effects of vanadium exposure in, 405
nickel concentrations in fluids and tissues
of, 288
vanadium concentrations in fluids and
tissues of, 410
Milk
iodine becoming excessive in, 4, 12
minerals becoming excessive in, 4
Mineral concentrations
expressed on a dry matter basis, 8
found in fresh and salt water, range or mean
of, 473, 476
improvements in analyzing, 1
Mineral supplements, potentially toxic levels
of contaminating minerals in, 2, 7
Mineral Tolerance of Domestic Animals, 1980
ed., 3, 10
developments in nutrition and toxicology
since, 1
updating, 2, 10
Minerals. See also Sources of minerals
and acid-base balance, 449^52
determination of acid-base balance, 449—
451
introduction, 449
maximal tolerable dietary cation-anion
difference for animal health and
productivity, 451^52
toxicosis, 45 1
contaminating, potentially toxic levels of in
mineral supplements, 2, 7
impact on environmental quality, 1
major species found in fresh and sea water,
474
microflora modifying the chemical form
of, 9
reviewed, 6
and toxic substances
in fish, 471
in terrestrial animals, 470^7 1
in water, sources of, 469^71
in unpolluted fresh water, sources and
normal ranges of, 473
MoUusks, aluminum toxicosis in, 21-22
Molybdenum, 262-275
from application of municipal wastes to the
land, 2
concentrations in fluids and tissues of
animals, 274—275
effect of exposure in animals, 271—273
essentiality, 262—263
introduction, 262
methods of analysis and evaluation, 263
MTLs of, 267-268
naturally occurring in certain soils, 2, 7
regulation and metabolism, 263-264
research needed on, 268
sources and bioavailability, 264
summary, 268
tissue levels, 267
toxicosis, 264—267
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Monkeys
effects of aluminum exposure in, 27
effects of cadmium exposure in, 91
selenium concentrations in fluids and
tissues of, 344-345
silicon concentrations in fluids and tissues
of, 356
MTLs. See Maximum tolerable levels of
toxicity
Municipal wastes. See Disposal of municipal
and animal wastes
Mutagenicity, in selenium toxicosis, 329
N
National Academies, Food and Nutrition
Board, 4
National Academy of Sciences, Committee on
Animal Nutrition, 1
National Research Council, 1
Natural water supplies, toxic levels of
minerals in, 2, 7
Neurological and neurodevelopmental effects
in aluminum toxicosis, 21
in lead toxicosis, 214
Nickel, 276-289
causing oxidative damage to cellular
macromolecules, 3
concentrations in fluids and tissues of
animals, 288-289
effect of exposure in animals, 284—287
essentiality, 276-277
introduction, 276
methods of analysis and evaluation, 277
MTLs of, 279-280
regulation and metabolism, 277-278
research needed on, 280
sources and bioavailability, 278
summary, 280
tissue levels, 279
toxicosis, 278-279
Nitrates and nitrites, 453^68
effects of nitrite exposure in animals, 461-
468
essentiality, 453
introduction, 453
methods of analysis and evaluation, 453^54
MTLs of, 458
regulation and metabolism, 454-455
research needed on, 458
sources and bioavailability, 455—456
summary, 459
tissue levels, 458
toxicosis, 456^58
No-observed-adverse-effect levels (NOAEL),
11
Nonruminants
acute toxicosis from nitrates and nitrites in,
456^57
chronic toxicosis from nitrates and nitrites
in, 457
sulfur toxicosis in, 375-376
Nutrition and nutritionists, 1
developments since 1980 ed. of Mineral
Tolerance of Domestic Animals. 1
Organic manganese, exposure to, 239-240
Organic mercury
acute toxicosis from, 253
chronic toxicosis from, 253-254
MTLs of, 255
toxicosis from single doses of, 252
Organic tin, in tin toxicosis, 390
Organotin compounds, in tin toxicosis, relative
effects of oral doses in mammals, 390
Pastures, increasing disposal of municipal and
animal wastes on, 1
Pesticide contamination, introducing minerals
into water supplies, 7
Pharmaceutical and other sources, of
aluminum, 17—18
Phosphoms, 290-305
in animal excreta, causing environmental
damage, 9
concentrations in fluids and tissues of
animals, 303-305
effect of exposure in animals, 300—302
essentiality, 290
introduction, 290
and manganese, 237—238
methods of analysis and evaluation, 290—
291
MTLs of, 295
potential effects on crop yields in the
environment, 4
regulation and metabolism, 291-292
research needed on, 295-296
sources and bioavailability, 292-293
summary, 296
tissue levels, 295
toxicosis, 293-295
Phosphorus metabolism, in aluminum
toxicosis, 20
Pigs
arsenic concentrations in fluids and tissues
of, 45
cadmium concentrations in fluids and
tissues of, 94
calcium concentrations in fluids and tissues
of, 114
chromium concentrations in fluids and
tissues of, 123
cobalt concentrations in fluids and tissues
of, 133
copper concentrations in fluids and tissues
of, 153
effects of arsenic exposure in, 43
effects of bismuth exposure in, 58
effects of cadmium exposure in, 92
effects of calcium exposure in, 109, 1 12
effects of fluorine exposure in, 173-174
effects of iodine exposure in, 196
effects of lead exposure in, 221
effects of nickel exposure in, 287
effects of sulfur exposure in, 382
lead concentrations in fluids and tissues
of, 223
magnesium concentrations in fluids and
tissues of, 234
mercury concentrations in fluids and tissues
of, 261
nickel concentrations in fluids and tissues
of, 288
selenium concentrations in fluids and
tissues of, 344-347
sodium chloride concentrations in fluids
and tissues of, 371
zinc concentrations in fluids and tissues of,
426
Potassium, 306-320
effect of exposure in animals, 314—320
environmental exposure to, 308
essentiality, 306—307
introduction, 306
methods of analysis and evaluation, 307
MTLs of, 311
potential effects on crop yields in the
environment, 4
regulation and metabolism, 307-308
research needed on, 3 1 1
sources and bioavailability, 308
summary, 311-312
tissue levels, 311
toxicosis, 308-311
Poultry, chronic toxicosis from selenium in,
328
Prawns, effects of chromium exposure in, 122
Quail
cadmium concentrations in fluids and
tissues of, 94
effects of cadmium exposure in, 92
effects of lead exposure in, 221
effects of mercury exposure in, 259
Rabbits
bismuth concentrations in fluids and tissues
of, 59
copper concentrations in fluids and tissues
of, 153
effects of aluminum exposure in, 27
effects of arsenic exposure in, 42
effects of cobalt exposure in, 130
effects of copper exposure in, 147
effects of iodine exposure in, 194
effects of manganese exposure in, 243
effects of molybdenum exposure in, 271
effects of phosphorus exposure in, 300
Ranchers, 1
Rare earths, 432^34
added to feeds, increasing potential for
toxicity, 7
metabolic interactions and mechanisms of
toxicity, 433
sources and metabolism, 433
tissue levels, 434
toxicosis and MTLs of, 433^34
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Rats
aluminum concentrations in fluids and
tissues of, 30
arsenic concentrations in fluids and tissues
of, 45
barium concentrations in fluids and tissues
of, 53
bismuth concentrations in fluids and tissues
of, 59
boron concentrations in fluids and tissues
of, 71
bromine concentrations in fluids and tissues
of, 78
chromium concentrations in fluids and
tissues of, 123
cobalt concentrations in fluids and tissues
of, 133
effects of aluminum exposure in, 27-28
effects of arsenic exposure in, 42
effects of barium exposure in, 51-52
effects of boron exposure in, 68-69
effects of bromine exposure in, 77
effects of cadmium exposure in, 91
effects of calcium exposure in. 111
effects of chromium exposure in, 121
effects of cobalt exposure in, 130
effects of copper exposure in, 147
effects of fluorine exposure in, 169-170
effects of iodine exposure in, 194
effects of manganese exposure in, 243
effects of molybdenum exposure in, 271
effects of nickel exposure in, 285—286
effects of phosphorus exposure in, 300-301
effects of potassium exposure in, 314—317
effects of selenium exposure in, 338
effects of silicon exposure in, 355
effects of sodium chloride exposure in, 367
effects of tin exposure in, 395-396
effects of vanadium exposure in, 405^07
molybdenum concentrations in fluids and
tissues of, 274
nickel concentrations in fluids and tissues
of, 288
phosphorus concentrations in fluids and
tissues of, 303
selenium concentrations in fluids and
tissues of, 344-345
silicon concentrations in fluids and tissues
of, 356
tin concentrations in fluids and tissues of, 397
vanadium concentrations in fluids and
tissues of, 410, 412
Recommended Dietary Allowances,
refinements in, 1
Recycled animal by-products and wastes,
increased feeding of, 1
Regulation and metabolism
of aluminum, 16-17
absorption, 16
biliary excretion, 1 7
urinary excretion, 16-17
of antimony, 429
of arsenic, 32-34
absorption and metabolism, 32—33
mechanisms of toxicity, 34
metabolic interactions, 33-34
of barium, 46^7
of bismuth, 54—55
of boron, 61-62
absorption and metabolism, 61
mechanisms of toxicity, 61-62
metabolic interactions, 61
of bromine, 72-73
of cadmium, 80-81
absorption, 80
excretion, 80-81
mechanisms of toxicity, 81
transport and distribution, 80
of calcium, 98-99
of chromium, 116-117
absorption and metabolism, 1 16
metabolic interactions and mechanisms
of toxicity, 116-117
of cobalt, 125
absorption and metabolism, 125
metabolic interactions and mechanisms
of toxicity, 125
of copper, 135-136
absorption and metabolism, 135
metabolic interactions and mechanisms
of toxicity, 135-136
of fluorine, 156-157
metabolic interactions and mechanisms
of toxicity, 157
of germanium, 430
of iodine, 184-185
absorption and metabolism, 184
metabolic interactions and mechanisms
of toxicity, 184-185
of iron, 200-201
absorption, 200
mechanisms of toxicity, 201
metabolic interactions, 200—201
of lead, 211-212
absorption and metabolism, 211-212
mechanisms of toxicity, 212
of lithium, 432
of magnesium, 225—226
of manganese, 235-237
absorption, 235—236
biliary excretion, 236-237
inhalation, 236
transport, 236
urinary excretion, 236
of mercury, 249-251
mechanisms of toxicity, 250-251
of molybdenum, 263-264
absorption and metabolism, 263
metabolic interactions, regulations, and
mechanisms of toxicity, 263-264
of nickel, 277-278
absorption and metabolism, 277
metabolic interactions and mechanisms
of toxicity, 277-278
of nitrates and nitrites, 454-455
of phosphorus, 291-292
absorption and metabolism, 291-292
metabolic interactions, regulations, and
mechanisms of toxicity, 292
of potassium, 307-308
absorption and metabolism, 307
metabolic interactions, 307—308
of rare earths, 433
of rubidium, 434-435
of selenium, 323-324
absoiption and metabolism, 323-324
metabolic interactions, regulations, and
mechanisms of toxicity, 324
of silicon, 349-350
absorption and metabolism, 349
metabolic interactions and mechanisms
of toxicity, 349-350
of silver, 436
of sodium chloride, 358—359
of strontium, 438
of sulfur, 373-374
of tin, 386-387
absorption and metabolism, 386-387
of titanium, 439
of tungsten, 440
of uranium, 442
of vanadium, 399
absorption and metabolism, 399
metabolic interactions, 399
of zinc, 414-415
absoiption, 414
excretion, 414
mechanisms of toxicity, 415
metabolic interactions, 415
regulation, 414
transport, 414
Regulators, government, 1
Renal effects, in lead toxicosis, 214
Reporting exposure, methods of, 8
Reproduction
effect of mercury on, 254
and fluorine toxicosis, 160-161
and lead toxicosis, 215
and selenium toxicosis, 328-329
Research needed
on aluminum, 23
on arsenic, 37
on barium, 49
on bismuth, 56
on boron, 64
on bromine, 75
on cadmium, 86
on calcium, 105-106
on chromium, 119
on cobalt, 127-128
on copper, 143
on fluorine, 163
on iodine, 190
on iron, 205
on lead, 218
on magnesium, 230
on manganese, 240
on mercury, 256
on molybdenum, 268
on nickel, 280
on nitrates and nitrites, 458
on phosphonis, 295-296
on potassium, 311
on selenium, 332
on silicon, 352
on sodium chloride, 364
on sulfur, 379
on tin, 392
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490
INDEX
on vanadium, 402
on water as a source of toxic substances, 471
on zinc, 419
Rubidium, 434-435
metabolic interactions and mechanisms of
toxicity, 434-435
sources and metabolism, 434
tissue levels, 435
toxicosis and MTLs of, 435
Ruminants
acute toxicosis from nitrates and nitrites
in, 456
chronic toxicosis from nitrates and nitrites
in, 457
chi'onic toxicosis from selenium in, 327
and polioencephalomalacia, 376-377
sulfur toxicosis in, 376-377
Safety factor, built-in, MTLs of not including, 3
Selenium, 321-347
accumulating to excessive levels in si^eletal
muscle, 4
becoming excessive in Icidneys, 4
becoming excessive in liver, 4
causing oxidative damage to cellular
macromolecules, 3
concentrations in fluids and tissues of
animals, 344-347
effect of exposure in animals, 337-343
essentiality, 322
introduction, 321-322
likely to reach toxic levels in natural water
supplies, 2, 7
methods of analysis and evaluation, 322-323
MTLs of, 331-332
naturally occumng in certain soils, 2, 7
potential effects on crop yields in the
environment, 4
regulation and metabolism, 323-324
research needed on, 332
sources and bioavailability, 324—326
summary, 332—333
tissue levels, 330—331
toxicosis, 326-330
utilization of, and hematological status in tin
toxicosis, 388-389
Sheep
aluminum concentrations in fluids and tissues
of, 30
barium concentrations in fluids and tissues
of, 53
cadmium concentrations in fluids and tissues
of, 95
calcium concentrations in fluids and tissues
of, 1 14
cobalt concentrations in fluids and tissues
of, 133
copper concentrations in fluids and tissues
of, 153
effects of aluminum exposure in, 29
effects of arsenic exposure in, 43
effects of cadmium exposure in, 93
effects of cobalt exposure in, 132
effects of copper exposure in, 150-151
effects of fluorine exposure in, 179
effects of iodine exposure in, 196-197
effects of iron exposure in, 208
effects of manganese exposure in, 245
effects of molybdenum exposure in, 272
effects of phosphorus exposure in, 302
effects of selenium exposure in, 342-343
effects of silicon exposure in, 355
effects of sodium chloride exposure in, 370
effects of sulfur exposure in, 384
effects of vanadium exposure in, 409
effects of zinc exposure in, 425
fluorine concentrations in fluids and tissues
of, 181
iodine concentrations in fluids and tissues of,
198
iron concentrations in fluids and tissues of, 209
lead concentrations in fluids and tissues of,
223
magnesium concentrations in fluids and
tissues of, 234
manganese concentrations in fluids and tissues
of, 247
mercury concentrations in fluids and tissues
of, 261
molybdenum concentrations in fluids and
tissues of, 275
nickel concentrations in fluids and tissues
of, 289
phosphorus concentrations in fluids and
tissues of, 304
selenium concentrations in fluids and tissues
of, 346-347
silicon concentrations in fluids and tissues
of, 356
sodium chloride concentrations in fluids and
tissues of , 37 1
sulfur concentrations in fluids and tissues
of, 385
vanadium concentrations in fluids and tissues
of, 411^12
zinc concentrations in fluids and tissues
of, 427
Silicon, 348-356
concentrations in fluids and tissues of
animals, 356
effect of exposure in animals, 355
essentiality, 348-349
introduction, 348
methods of analysis and evaluation, 349
MTLs of, 351-352
regulation and metabolism, 349-350
research needed on, 352
sources and bioavailability, 350
summary, 352
tissue levels, 351
toxicosis, 350-351
Silver, 435^37
metabolic interactions and mechanisms of
toxicity, 436
sources and metabolism, 435^36
tissue levels, 437
toxicosis and MTLs of, 436^37
Skeletal muscle, minerals accumulating to
excessive levels in, 4
Sodium
likely to reach toxic levels in natural water
supplies, 2, 7
potential effects on crop yields in the
environment, 4
Sodium chloride, 357-371
concentrations in fluids and tissues of
animals, 371
effect of exposure in animals, 367—370
essentiality, 357
introduction, 357
methods of analysis and evaluation, 357-358
MTLs of, 363-364
regulation and metabolism, 358-359
research needed on, 364
sources and bioavailability, 359-360
tissue levels, 363
toxicosis, 360-363
Sources of minerals
of aluminum, 17-19
of antimony, 428^29
of arsenic, 34—35
of barium, 47
of bismuth, 55
of boron, 62
of bromine, 73
of cadmium, 81-82
of calcium, 99
of chromium, 117
of cobalt, 125-126
of copper, 136-137
of fluorine, 157-158
of germanium, 430
of iodine, 185-186
of iron, 201-202
of lead, 212-213
of lithium, 431^32
of magnesium, 226
of manganese, 237-238
of mercury, 251-252
of minerals and toxic substances in water,
469^70
of molybdenum, 264
of nickel, 278
of nitrates and nitrites, 455^56
of phosphorus, 292—293
of potassium, 308
of rare earths, 433
of rubidium, 434
of selenium, 324-326
of silicon, 350
of silver, 435-436
of sodium chloride, 359-360
of strontium, 437-438
of sulfur, 374
of tin, 387-388
of titanium, 439
of tungsten, 440
of uranium, 441^442
of vanadium, 399-400
of zinc, 415^16
Spleen, minerals becoming excessive in, 9
Strontium, 437^39
metabolic interactions and mechanisms of
toxicity, 438
sources and metabolism, 437^38
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491
tissue levels, 439
toxicosis and MTLs of, 438^39
Sulfur, 372-385
concentrations in fluids and tissues of
animals, 385
effect of exposure in animals, 381-384
essentiality, 372-373
introduction, 372
likely to reach toxic levels in natural water
supplies, 2, 7
methods of analysis and evaluation, 373
MTLs of, 378-379
potential effects on crop yields in the
environment, 4
regulation and metabolism, 373-374
research needed on, 379
sources and bioavailability, 374
summary, 379
tissue levels, 378
toxicosis, 374—378
Supplements, potentially toxic levels of
contaminating minerals in, 2
Swine
chronic toxicosis from selenium in, 327-328
effects of barium exposure in, 5 1
effects of bromine exposure in, 77
effects of chromium exposure in, 122
effects of cobalt exposure in, 131
effects of copper exposure in, 149
effects of iron exposure in, 208
effects of manganese exposure in, 244
effects of molybdenum exposure in, 271
effects of phosphorus exposure in, 301
effects of selenium exposure in, 339-340
effects of sodium chloride exposure in, 367-
368
phosphorus concentrations in fluids and
tissues of, 303
Teratogenicity, and selenium toxicosis, 329
Terrestrial animals, and minerals and toxic
substances in water, 470^71
Tin, 386-397. See also Inorganic tin; Organic tin
concentrations in fluids and tissues of
animals, 397
effect of exposure in animals, 395-396
essentiality, 386
introduction, 386
methods of analysis and evaluation, 386
MTLs of, 391-392
regulation and metabolism, 386-387
research needed on, 392
sources and bioavailability, 387-388
summary, 392
tissue levels, 391
toxicosis, 388-391
Tissue levels
of aluminum, 22, 30
of antimony, 429
of arsenic, 36, 45
of barium, 48, 53
of bismuth, 56, 59
of boron, 63-64,71
of bromine, 74, 78
of cadmium, 85-86, 94-96
of calcium, 103-104, 114
of chromium, 118, 123
of cobalt, 127, 133
of copper, 142, 153
of fluorine, 162, 181
of germanium, 43 1
of iodine, 189, 198
of iron, 205, 209
oflead, 217, 223
of lithium, 432
of magnesium, 228-229, 234
of manganese, 240, 247
of mercury, 255, 261
of molybdenum, 267, 274-275
of nickel, 279, 288-289
of nitrates and nitrites, 458
of phosphorus, 295, 303-305
of potassium, 311
of rare earths, 434
of rubidium, 435
of selenium, 330-331, 344-347
of silicon, 351, 356
of silver, 437
of sodium chloride, 363, 371
of strontium, 439
of sulfur, 378, 385
of tin, 391,397
of titanium, 439^140
of tungsten, 441
of uranium, 443
of vanadium, 402, 410-^12
ofzinc, 418^19, 426^27
Titanium, 439^140
metabolic interactions and mechanisms of
toxicity, 439
sources and metabolism, 439
tissue levels, 439^440
toxicosis and MTLs of, 439
Tolerable Upper Intake Levels (UL) of minerals,
1, 11
Tolerances. See also Maximum tolerable levels
of minerals
increasing with age, 9
Toxicity of minerals, 1^, 8—9. See also
Maximum tolerable levels of toxicity;
Mechanisms of toxicity
and assessments of nutrients for humans, 14
Toxicology and toxicologists, 1
developments since 1980 ed. of Mineral
Tolerance of Domestic Animals, 1
Toxicosis
of aluminum, 19-22
bone metabolism, 20
calcium and other minerals, 21
fish and mollusks, 21-22
fluoride utilization, 20-2 1
growth and longevity, 19-20
neurological symptoms, 21
phosphorus metabolism, 20
of antimony, 429
of arsenic, 35—36
acute, 35
chi'onic, 35-36
factors influencing toxicity, 36
of barium, 47^8
acute, 48
chronic, 48
factors influencing toxicity, 48
single dose, 47^8
of bismuth, 55-56
chronic, 55
factors influencing toxicity, 55-56
single dose, 55
of boron, 62—63
acute, 63
chronic, 63
factors influencing toxicity, 63
single dose, 62—63
of bromine, 73-74
acute, 74
chronic, 74
factors influencing toxicity, 74
single dose, 73—74
of cadmium, 82-85
acute, 83-84
chronic, 84
factors influencing toxicity, 85
single dose, 83
of calcium, 99-103
acute, 100, 109
chronic, 100-103, 109-113
factors influencing toxicity, 103
single dose, 99-100, 109
of chromium, 117-118
chronic, 118
factors influencing toxicity, 118
single dose and acute, 1 17
of cobalt, 126-127
chronic, 126
factors influencing toxicity, 126-127
single dose and acute, 126
of copper, 137-142
chronic, 138-140
factors influencing toxicity, 140-142
single dose and acute, 138
of fluorine, 158-159
acute, 159
chronic, 159-160
factors influencing toxicity, 161-162
genotoxicity and carcinogenicity, 161
reproduction, 160-161
single dose, 159
of germanium, 430^3 1
of iodine, 186-189
acute and chi'onic, 186-188
factors influencing toxicity, 188-189
single dose, 186
of iron
acute, 203-204
chronic, 204
factors influencing toxicity, 204—205
single dose, 202-203
oflead, 213-217
acute, 215-216
bone, 215
cancer, 215
cardiovascular effects, 214
chronic, 216
factors influencing toxicity, 216-217
gastrointestinal effects, 214
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INDEX
hematological changes, 213-214
immunological effects, 214—215
neurological and neurodevelopmental
effects, 214
renal effects, 214
reproduction, 215
single dose, 215
toxicity to aquatic organisms, 215
of lithium, 432
of magnesium, 226-228
acute, 227, 232
chronic, 227-228, 232-233
factors influencing toxicity, 228
single dose, 226-227, 232
of manganese, 238—240
chronic dietary exposure to inorganic
manganese, 238-239
exposure to inorganic manganese in
water, 239
exposure to organic forms of manganese,
239-240
inhalation exposure to inorganic
manganese, 239
intravenous exposure to inorganic
manganese, 239
of mercury, 252-255
acute, 252-253
chronic, 253-254
effect of mercury on reproduction, 254
factors influencing toxicity, 254—255
single dose, 252
of minerals and acid-base balance, 451
acute (uncompensated metabolic acidosis
or alkalosis), 451
chronic (compensated metabolic acidosis
or alkalosis), 451
of molybdenum, 264—267
chronic, 265-266
factors influencing toxicity, 266-267
reproduction, 266
single dose and acute, 265
of nickel, 278-279
acute, 278-279
chronic, 279
factors influencing toxicity, 279
of nitrates and nitrites, 456^58
acute, 456^57
aquatic animals, 457^58
chronic, 457
of phosphorus, 293-295
chronic, 293-294
factors influencing toxicity, 294—295
single dose and acute, 293
of potassium, 308—3 1 1
factors influencing toxicity, 311
high levels, 309-310
low levels, 308-309
of rare earths, 433^34
of rubidium, 435
of selenium, 326—330
carcinogenicity and mutagenicity, 329
chronic, 327-328
factors influencing toxicity, 329—330
humans, 329
reproduction, 328—329
single dose and acute, 326
subacute, 326-327
teratogenicity, 329
of silicon, 350—351
acute, 351
chronic, 351
factors influencing toxicity, 351
of silver, 436^37
of sodium chloride, 360—363
acute, 360-362, 368
chronic, 362-363, 369-370
factors influencing toxicity, 363
single dose, 360, 367
of strontium, 438^39
of sulfur, 374-378
cysteine toxicity, 376
factors influencing toxicity, 378
methionine toxicity, 376-378
miscellaneous considerations, 377
nonruminants, 375-376
ruminants and polioencephalomalacia,
376-377
single dose, 375, 381
toxicity of sulfur, 375
of tin, 388-391
additional side effects of diorganotin
compounds, 39 1
bone and calcium utilization, 389
gastrointestinal symptoms, 388
growth and zinc utilization, 388
hematological status and iron, copper,
and selenium utilization, 388—389
inorganic tin, 388
organic tin compounds, 390
relative effects of oral doses of various
organotin compounds in mammals,
390
tri-n-butyltin and dibutyltin toxicosis,
391
triethyltin toxicosis, 390-391
trimethyltin toxicosis, 390
of titanium, 439
of tungsten, 440^141
of uranium, 442^143
of vanadium, 400-402
factors influencing toxicity, 401^02
high quantities and acute, 400^0 1
low quantities and chronic, 401
of zinc, 416^18
exposure by feed, 416^18
exposure by water, 418
factors influencing toxicity, 418
Tri-n-butyltin, in tin toxicosis, 391
Triethyltin toxicosis, 390—391
Trimethyltin toxicosis, 390
Tungsten, 440-441
metabolic interactions and mechanisms of
toxicity, 440
sources and metabolism, 440
tissue levels, 441
toxicosis and MTLs of, 440^41
Turkeys
chromium concentrations in fluids and
tissues of, 123
effects of aluminum exposure in, 29
effects of calcium exposure in, 112
effects of chromium exposure in, 122
effects of copper exposure in, 148
effects of fluorine exposure in, 173
effects of iodine exposure in, 195
effects of manganese exposure in, 244
effects of silicon exposure in, 355
effects of sodium chloride exposure in,
368-369
selenium concentrations in fluids and
tissues of, 344-345
u
UL. See Tolerable Upper Intake Levels of
minerals
Uncompensated metabolic acidosis or
alkalosis, in acute mineral and acid-
base balance toxicosis, 451
Uranium, 441^443
metabolic interactions and mechanisms of
toxicity, 442
sources and metabolism, 441^42
tissue levels, 443
toxicosis and MTLs of, 442-443
U.S. Department of Agriculture, 1 1
U.S. Department of Health and Human
Services, Food and Drug
Administration, 1
V
Vanadium, 398-412
causing oxidative damage to cellular
macromolecules, 3
concentrations in fluids and tissues of
animals, 410^12
effect of exposure in animals, 405—409
environmental exposure to, 399^00
essentiality, 398-399
introduction, 398
methods of analysis and evaluation, 399
MTLs of, 402
regulation and metabolism, 399
research needed on, 402
sources and bioavailability, 399^00
summary, 402
tissue levels, 402
toxicosis, 400^02
Veterinarians, 1
w
Wastes. See Disposal of municipal and animal
wastes: Industrial wastes; Recycled
animal by-products and wastes
Water
iron in, 201-202
manganese in, 237
nitrates and nitrites in, 456
rate of consumption, 9
as a source of toxic substances, 469^76
drinking water standards for humans and
livestock, 475
introduction, 469
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INDEX
493
major mineral species found in fresli and
sea water, 474
minerals and toxic substances in water,
470^71
range or mean of mineral concentrations
found in fresh and salt water, 476
range or mean of mineral concentrations
found in sea water, 473
research needed on, 47 1
sources and normal ranges of minerals in
unpolluted fresh water, 473
sources of minerals and toxic substances
in water, 469^70
summary, 471
toxic levels of minerals in natural supplies
of, 2
zinc in, 415
Zinc, 413^27
added to feeds, increasing potential for
toxicity, 7
in animal excreta, causing environmental
damage, 9
from application of municipal wastes to the
land, 2
concentrations in fluids and tissues of
animals, 426-4-27
effect of exposure in animals, 423^25
essentiality, 413
and human health
introduction, 413
methods of analysis and evaluation, 413-
414
MTLs of, 419
potential effects on crop yields in the
environment, 4
regulation and metabolism, 414-415
research needed on, 419
sources and bioavailability, 415^16
summary, 420
tissue levels, 418^19
toxicosis, 416^18
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Genetic Engineering of Plants: Agricultural Research Op-
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The U. S. National
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Pesticide Resistance: Strategies and Tactics for Manage-
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Pesticides and Groundwater Quality: Issues and Problems
in Four States (1986)
Pesticides in the Diets of Infants and Children (1993)
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The Role of Chromium in Animal Nutrition (1997)
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Soil and Water Quality: An Agenda for Agriculture (1993)
Soil Conservation: Assessing the National Resources In-
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Sustainable Agriculture Research and Education in the Field:
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The Use of Drugs in Food Animals: Benefits and Risks
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Water Transfers in the West: Efficiency, Equity, and the
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Wood in Our Future: The Role of Life Cycle Analysis
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Nutrient Requirements of Domestic Animais Series and
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Building a North American Feed Information System (1995)
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Metabolic Modifiers: Effects on the Nutrient Requirements
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Nutrient Requirements of Beef Cattle, Seventh Revised Edi-
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Nutrient Requirements of Dogs, Revised Edition (1985)
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Predicting Feed Intake of Food-Producing Animals (1986)
Role of Chromium in Animal Nutrition (1997)
Scientific Advances in Animal Nutrition: Promise for the
New Century (2001)
Vitamin Tolerance of Animals (1987)
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