THE METABOLISM OF THE
FASTING STEER
FRANCIS G. BENEDICT
Director
Nutrition Laboratory , Carnegie Institution of Washington
AND
ERNEST G. RITZMAN
Research Professor in Animal Nutrition
Nezv Hampshire Agricultural Experiment Station
Published by the Carnegie Institution of -Washington
1927
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CARNEGIE INSTITUTION OF WASHINGTON
Publication No. 377
1927
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WASHINGTON, D. C.
THE METABOLISM OF THE FASTING STEER
BY
FRANCIS G. BENEDICT
Director. Nutrition Laboratory, Carnegie Institution of Washington
AND
ERNEST G. RITZMAN
Research Professor in Animal Nutrition
New Hampshire Agricultural Experiment Station
Published by the Carnegie Institution of Washington
1927
T
i
CONTENTS
PAGE
Introduction . 3
The significance of the fasting metabolism of cattle . 4
Determination of the true fasting condition . . 8
The practical value of fasting . 9
Other investigations on the fasting of large animals . 12
Magendie, 1852 . 12
Colin, 1862 and 1888. . 12
Grouven, 1864 . 15
Ignatief , 1883 . 20
Meissl, 1886, and Tangl, 1912 . 20
Capstick and Wood, 1922 . 21
Deighton, 1923 . 22
Armsby and Braman, 1923-24 . 22
Changes in apparatus and technique . 24
Changes in the laboratory building . 24
Provision for collection of individual urinations . 25
Additions to respiration chamber . 26
Changes in the technique for measuring the respiratory exchange . 29
Soda-lime . 29
Determination of proportion of air escaping through openings in wind chest 29
Selection of disk opening to meet specific experimental requirements . 31
Gas-analysis apparatus . 31
Importance of gas analysis . 31
Description of gas-analysis apparatus . 33
The physiological control of gas-analysis apparatus . 34
Installation of the gas-analysis apparatus at Durham and correction in
calculation of carbon-dioxide production necessitated by its use . 34
Procedure for most accurate determination of respiratory quotient . 36
Principles underlying control tests of respiration chamber by admitting
known amounts of carbon dioxide . 36
Animals used in experiments . 38
General plan of research . 39
Fasting on different planes of nutrition . 39
Subsidiary problems . 39
Chronology of the fasting research . 41
Details of the experimental conditions . 41
Observations on mature steers C and D . 42
Details of the 14-day fast in April 1922 . 43
General observations during the 14-day fast . 46
Summarized details of other fasts of steers C and D . 48
Observations on immature steers E and F . 51
Records of last individual feed prior to each fast . 52
Discussion of results . 54
Body-weight . 54
Lengths of fasts and nature of feed-levels preceding them . 55
Daily variations in body-weight during fasting . 56
Influence of long fasts at different levels of nutrition . 56
Influence of short fasts at a maintenance level of nutrition . 60
Losses in body-weight during 4-day fasts under similar conditions . 62
General conclusion with regard to significance of changes in body-weight. . 63
Loss through the lungs and skin . 63
Insensible perspiration during food periods and during 24 hours without
food . 66
Insensible loss during 3 days with food, followed by 2 and 3 days without
food, at a maintenance level of nutrition . 70
v
Vi METABOLISM OF THE FASTING STEER
Discussion of results — Continued page
Loss through the lungs and skin — Continued
Insensible loss during 5 to 14 days without food . 71
Drinking-water . 75
Feces . 81
Amount and frequency of defecations . 82
Physical characteristics of feces . 89
Chemical composition of feces . 91
Dry matter in feces . 91
Nitrogen in feces . 95
Urine . 97
Influence of fasting on amounts of urine excreted . 99
Amounts per 24 hours and per hour . 99
The frequency and amount of individual urinations during fasting. . . 101
Relation between volume and dry matter of urine . 103
Physical properties of the urine . 103
Chemistry of the urine . 104
Urine analyses by other investigators . 104
Chemical methods . . 107
Statistics of results . 107
Discussion of results . 114
Chlorides in urine . 114
Nitrogen excreted in urine per hour . 115
Partition of urinary nitrogen . 116
Other urinary constituents . 121
Total nitrogen excreted per kilogram of body-weight per 24 hours 121
Creatinine coefficient . 122
The nitrogen economy of steers . 122
General conclusions with regard to the composition of steer’s urine
during fasting . 123
Nitrogen loss . 127
Total nitrogen excreted in urine per day and during the entire fast . 127
Total nitrogen loss during fasts of 5 to 14 days . 129
Body measurements, general body conditions, and physiological functions . 130
Body measurements . 130
General body conditions . 133
General behaviour of fasting steers . 133
General appearance . 136
Heart-rate . 137
Respiration-rate . 141
Rectal temperature . 142
Skin temperature . . . 143
Gaseous metabolism and energy relationships . 144
Metabolism measurements actually made or computed . 144
Conditions prerequisite for comparable measurements of metabolism ..... 150
The physiological comparison of animals . 152
Comparison on the basis of live body-weight . 152
Comparison on the basis of body-surface . 153
Method of estimating the surface area of fasting steers . 153
Method of presenting the gaseous metabolism data . 156
Metabolism during fasting . 158
Respiratory quotient . 158
Carbon-dioxide production . 161
Tabular presentation of data for long and short fasts . 165
Course of the heat-production during fasts of 5 to 14 days, at different
levels of nutrition . 171
Total heat-production per 24 hours . 171
Heat-production per 500 kg. of body-weight per 24 hours . 174
Heat-production per square meter of body-surface per 24 hours . . . 179
CONTENTS
Vll
Discussion of results — Continued page
Gaseous metabolism and energy relationships — Continued
Metabolism during fasting — Continued
Heat-production in 2-day fasts at a maintenance level of nutrition . 180
Measurement of fasting metabolism in 3 consecutive 24-hour periods . . . 185
Comparison, of the metabolism during 2 days on food, followed by 2 days
without food, at maintenance and submaintenance levels and at high
and low environmental temperatures . 192
Influence of quantity and character of ration upon metabolism during
feeding . 196
Influence of quantity and character of ration upon metabolism during
fasting . 198
Influence of environmental temperature . 200
Influence of lying and standing . 202
The basal metabolism of steers . 203
Incidence of plateau in metabolism of steers after cessation of active
digestion . 204
The metabolic plateau of the same animal, when fasting under different
conditions . 206
Conclusions regarding the incidence and the level of the plateau in
metabolism of steers . 208
Computation of the fasting katabolism of steers from experiments on
two different feed-levels . 209
Correction of basal katabolism to a standard day as to standing
and lying . 211
Inherent error in method of computing the fasting katabolism from
experiments on two different feed- levels . 213
The minimum heat-production of steers per square meter of body-
surface per 24 hours . 218
The physiological significance of surface area and its relationship
to heat-production . 221
Influence of the ingestion of food . 222
The immediate reaction to the ingestion of food after a prolonged fast 222
The metabolic stimulus of feeding-stuffs . 223
The standard metabolism of steers under different conditions . 228
Factors other than the nutritive level which affect the standard
metabolism . 228
Level of the standard metabolism at the beginning of the different
fasts . 230
Influence of environmental temperature upon standard metabolism .... 230
Influence of level of nutrition upon the standard metabolism . 231
Summary . 235
Subject index . 241
Author index . 246
,
ILLUSTRATIONS
Fig. page
1. Arrangement of laboratory rooms . 24
2. Diagram of feed-chute, feed-box, feces-chute, and provision for collection of urine
in respiration chamber . 26
3. Diagram of the Carpenter apparatus for the exact analysis of atmospheric and
chamber air . 33
4. Individual defecations of steers C and D during fasts in April and November
1922 and March 1924 . 87
5. Feces voided by steer C on the sixth day of fasting, November 10, 1923 . 88
6. Feces voided by steer D on the fifth day of fasting, March 8, 1924 . 88
7. Individual urinations of steers C and D during fasts in April and November, 1922,
and March 1924 . 102
8. Body-surface in square meters referred to live weight in kilograms . 155
vm
THE METABOLISM OF THE FASTING STEER
By F. G. Benedict and E. G. Ritzman
From the Nutrition Laboratory of the Carnegie Institution of Washington,
at Boston, Massachusetts, and the New Hampshire Agricultural
Experiment Station, Durham, New Hampshire
With eight text figures
1
INTRODUCTION
Much of the research in the field of human nutrition has been based upon
experiments made during complete fasting. In this condition the minimum
metabolism or the degree to which the body is drawn upon for maintenance
of the life processes can be determined, and the capacity of any food or
ration to protect the body from such drafts can then immediately be
referred to the fasting metabolism. The seemingly inherent difficulties in
subjecting a ruminant with large paunch to fasting has deterred most
workers in animal nutrition from such tests, although as early as 1862
Hubert Grouven made his classic experiments with oxen, one of which fasted
for 8 days.®
In the management of domestic livestock, farmers in the United States
have been educated to believe that regular and liberal feeding forms the
basis of good economic practice. This belief has not uncommonly led to
the inference that animals deprived entirely of food, even for a relatively
short time, would endure physical hardship, suffering, and injury. The
error of such a conclusion is best illustrated by a consideration of the life
habits of wild animals, such as the deer, which is also a ruminant. Deer
pass through long periods of deprivation, when food is scant or sometimes
entirely lacking, and on the whole survive in excellent shape, with remark¬
able vigor, unimpaired by such experiences. As pure a priori reasoning, it
would seem logical to assume that the length of time during which an animal
can comfortably go without food would be, at least in part, determined by
its storage capacity, for until the food in the digestive tract is used up,
complete fasting does not begin. The camel, due to his capacity for storage
of water, has long been used for desert journeys. In a like, though limited,
manner the ox has a storage capacity for forage and can exist without
having his food replenished for several days before this storage is entirely
depleted. The ox, however, is seldom forced by man to make use of this
provision of nature, because it is usually more profitable not to do so.
The history of experimental fasting also shows that nature has provided
animal life with a wide measure of protection against the contingency of
food shortage. The almost incredible length of time that the dog has been
able to withstand fasting, notably in the experiments of Howe and Hawk* * 6
whose dog fasted for over 100 days, and the long intervals known to elapse
between the taking of food by cold-blooded animals, such as the large
python in the New York Zoological Park0 and the snake studied by Valen¬
ciennes, d lead to the inference that fasting per se is not ordinarily injurious,
provided it is not carried to too great an extreme. All animal life does not,
of course, possess the same degree of resistance to fasting, but it is safe to
say that the resistance is far greater than is generally supposed. In the last
° Grouven, Physiologisch-chemische Fiitterungsversuche. Zweiter Bericht iiber die Arbeiten
der agrikulturchemischen Versuchsstation zu Salzmiinde, Berlin, 1864.
6 Howe and Hawk, Am. Journ. Physiol., 1912, 30, p. 174; Howe, Mattill, and Hawk, Journ.
Biol. Chem., 1912,11, p. 103.
e Unpublished experiments of Mr. Raymond L. Ditmars at the New York Zoological Park.
d Valenciennes, Compt. rend., 1841, 13, p. 126.
3
4
METABOLISM OF THE FASTING STEER
three or four decades much experience has been secured, both in the labora
tory and also (as an incidental result of the recent World War) in large
communities, regarding the effect upon humans of entire lack of food or of
a greatly reduced food intake. This experience has indicated that, although
in many instances serious disturbances may arise from such food shortage,
unless the lack of food occurs at a very early stage of life, complete recupera¬
tion generally takes place fairly rapidly when sufficient food is again
available. Indeed, we have seen that laboratory experience with animals
shows innumerable instances of partial and of complete fasting for several
months without ill results, and numerous observations on humans show
that with some individuals complete controlled fasting may progress without
injurious results for from one week to one month.0
The Nutrition Laboratory has for many years experimented with fasting.
It has studied men who fasted for from 8 to 31 days, geese which were
deprived of food for 30 days, and snakes which voluntarily refused food for
a period of months. The general conclusion drawn from these experiments
is that such fasting was not accompanied by pain, distress, or any untoward
after-effects. This conclusion has been further confirmed by the extended
experience of the Nutrition Laboratory in studying the effects of under¬
nutrition upon a large group of young men. These men showed many
striking, if not profound, physiological alterations due clearly to under-
nutrition, without a corresponding change in intellectual and physical
powers.6
Having thus demonstrated the safety with which fasting and under-
nutrition may be practiced in humans, perhaps the most sensitive animal,
the Nutrition Laboratory, in cooperation with the New Hampshire Agri¬
cultural Experiment Station, undertook a study of undemutrition in large
steers, a report of which was recently issued.0 This study likewise indicated
clearly that undernutrition causes no distress or pain in cattle. An attempt
to subject large ruminants to complete fasting seemed, therefore, in no sense
open to serious objection.
THE SIGNIFICANCE OF THE FASTING METABOLISM
OF CATTLE
As the result of feeding there occurs in the animal body a series of energy
transformations which, from the economic point of view, represent at least
four distinct phases of vital activity.
(1) The maintenance of life or body equilibrium.
(2) Productive use above the maintenance requirements, such as that for
growth, milk production, and body deposits.
(3) Muscular activity, such as the productive muscular work of draft
horses or oxen.
(4) The energy incident to the conversion of food or digestion.
The first bears directly on the extent to which food may serve to protect
body-tissue from being drawn upon to maintain life and to replace body-
tissue so used. The second relates to the extent to which food may be
° Benedict, Carnegie Inst. Wash. Pub. No. 203, 1915.
1 Benedict, Miles, Roth, and Smith, Carnegie Inst. Wash. Pub. No. 280, 1919.
* Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923.
I
INTRODUCTION 5
converted into surplus body-tissue or into other usefully productive pur¬
poses above the needs of maintenance. Muscular work, when external, is
a true production which, may be of value, as in the draft animal, or may
be waste, as in the restlessness or activity of the animal, even when in the
stall. The internal muscular work of respiration, circulation, and digestive
processes is an integral part of the necessary life processes of the animal,
and hence a factor of maintenance. Productive muscular work must always
be considered as a separate item, since it is performed at the expense of the
production of body-tissue. It is equally clear that if the cost of food con¬
version, that is, the increase in heat-production following the ingestion of
food, represents energy which does not serve to protect body-tissue or to
form body-tissue, it must be regarded as an overhead cost physiologically.
The significance of studying the fasting metabolism under comfortable
stall conditions, therefore, is that under these conditions the third and fourth
uses of the total energy production are eliminated, and it is possible to
determine the capacity of the energy in food to meet the first two needs.
Maintenance or fasting metabolism — The first function of food is to
maintain life. Since the food, as eaten, requires considerable elaboration,
cleavage, and resynthesis, an additional amount must be allowed to meet
the energy expended in the conversion of the food ; otherwise the ration will
be deficient by that amount and body-tissue will be drawn upon to make up
for the deficit. If no food at all is given, the entire amount of energy neces¬
sary to maintain life will be supplied by body -tissue. In this case the total
energy production represents solely that quota of energy use which is neces¬
sary to maintain life, no overhead cost being included because no food is
present. This fasting katabolism is the basic constant which must first be
determined, before the energy uses for productive efforts and for overhead
service can be reckoned separately. Furthermore, it is only on this fasting
basis, when the metabolism indicates the daily heat requirements necessary
to maintain life, that a comparison between different species or between
animals differing in size or body-build is of any significance.
Productive use of food is represented by that measure of efficiency with
which the animal is able to convert food, given in excess of its own
need for maintaining body equilibrium, into some useful product such as
growth, meat, milk, wool, or work. It is for this surplus production that
domestic animals are kept, and it is on the basis of this surplus production
that the efficiency of animals and of feeds is economically of variable
significance. From a quantitative point of view the value of any given
ration is in large part determined by the proportion of potential energy
which it yields for conversion into body structure or milk.0 A sufficient
amount of protein is no less essential to carry on these functions success¬
fully than is a sufficient amount of energy. Yet quantitatively the protein
requirement never exceeds one-fourth of the energy requirement, even for
growth or milk production, and for fattening purposes the quantitative rela¬
tionship between energy and protein may even exceed a ratio of 10 to 1.
The more recent knowledge regarding food-accessory factors is increasingly
challenging attention also, but as far as now known their quantitative
• Armsby, Journ. Agric. Sci., 1919, 9, p. 182.
6
METABOLISM OF THE FASTING STEER
importance is too small to be measurable. Hence it is not surprising that in
general studies on nutrition the energy problems must continue to play the
dominant role. I
Muscular activity is a factor which makes an exceedingly marked demand I
on the use of energy. So far as tissue katabolism is concerned, there are 1
several classes of muscular activity. Thus, the muscular activity which is 1
involved in the mastication and general manipulation of food in the
animal body is of a more or less involuntary character, and is to some
extent proportional to food conversion, in behalf of which it is entirely
exerted. It is an overhead expense, because it uses body-tissue which must
be replaced by food, and as it can not be modified or controlled while
animals are being fed, the determination of its quantitative demands on
energy becomes complicated. Other types of muscular activity of a more |
voluntary nature are exhibited and measurable by the extent of visible .
manifestations, such as general restlessness and moving around. Such j
movements are in no sense contributory to food conversion. This type of y
muscular exertion may result in a greatly variable energy expenditure under |
ordinary conditions, not only when animals are grazing and thus obliged to
move about according to the quality of pasturage, but also during the
season of stall feeding, if they are allowed daily exercise. Unless the pri¬
mary object in feeding animals for a usefully productive purpose is to enable
them to perform physical exertion or work, as in the case of horses, mules,
and work oxen, this type of muscular activity, if permitted, also becomes
an overhead charge. In the study of nutrition problems, where muscular
exertion is not the objective, this factor can easily be controlled within
reasonable limits by placing the animals in stalls, so that voluntary mus¬
cular exertion is represented only by the tension due to standing and the
effort of changing from the lying to the standing position.
The energy involved in food conversion, which is an overhead item,
includes the energy expended in the actual physiological processes of masti¬
cation, digestion, and manipulation of food in the alimentary tract. It also
includes a large daily energy production which occurs immediately when
food is ingested or is present in the alimentary tract, inducing a stimulating
effect on the body cells. Since, in this conversion of food, energy is con¬
sumed which would otherwise contribute to tissue equilibrium or towards
other usefully productive service, this energy must be regarded as waste,
just as undigested feed residues or the gases produced by fermentation are
regarded as waste.
When food enters the alimentary tract there begins immediately a process
which involves muscular motion, and, as is known, all muscular motion is
accompanied by heat-production. Even the act of mastication results in a
certain definite consumption of energy. The difficulties of measuring this
latter exactly have led to wide divergence in the conception of the energy
cost of mastication. With man a distinct rise in metabolism has been
noticed as a result of chewing an inert, insoluble substance such as rubber
or gum.® The subsequent processes of deglutition, peristalsis, expulsion of
“Benedict and Carpenter, Carnegie Inst. Wash. Pub. No. 261, 1918, p. 139.
INTRODUCTION
7
feces, and, in the case of ruminants, rumination, all involve muscular actions
and, theoretically at least, heat-production.
The earliest studies with ruminants showed that there were great increases
in energy production following the ingestion of food, increases which were
at first attributed, naturally enough, to the slow passage of food through
the alimentary tract and the vast amount of material to be worked over
by peristaltic action. Indeed, Zuntz and his school believed that the increase
was due in large part to the muscular activity involved in the propulsion
of food from the mouth to the anus, although they freely recognized that
there were subsidiary energy transformations necessitated by glandular and
other processes. In the experiments with ruminants, the feed residues to be
moved through the intestinal tract were very large, the indigestible matter
amounting with rough fodders to 50 per cent of the intake. On the other
hand, in experiments with humans and dogs, the diet contained a relatively
small amount of indigestible material, and hence the increment due to the
process of digestion could not logically be attributed to the muscular activity
of moving a large food ballast. Furthermore, a careful study of the effect
of individual nutrients, protein, fat, and carbohydrate, showed that protein
caused a much greater rise in the heat-production of the dog or of man
than either carbohydrate or fat. This difference was ascribed by Rubner
to the “specific dynamic action” of the foodstuffs, and the two schools of
Zuntz and Rubner have had long controversial discussions as to the causes
for the increase in metabolism following the ingestion of food. It is not at
all surprising that Zuntz, with his intimate knowledge of the physiology of
the ruminant, should have attributed the large increase noted with these
animals to muscular activity in connection with their enormous fecal masses
and ballast. The amount of protein involved in the ration of many of these
ruminants, and particularly in some of the special experiments of Zuntz,
was so small as almost to rule out any material influence of protein per se.
On the contrary, in Rubner’s experiments on dogs, which were given large
masses of nearly pure protein, the large increases noted in metabolism could
not have been caused by the muscular action due to the process of digestion.
Since the promulgation of these earlier theories much experimental work
has accumulated, chiefly with humans and laboratory animals, but at the
present date information with regard to large ruminants is still sadly
lacking. It is a fact, however, that the ingestion of food usually produces a
marked increase in the heat-production of ruminants. Hence, in estimating
the energy value of a given ration, one must immediately recognize that the
increase in metabolism incidental to the digestion of the ration does not
contribute to the production of either tissue or milk and must logically be
charged as an expense in the preparation of the raw food material for
deposition of tissue or for production of milk.
Although the processes of digestion, absorption, and peristalsis theo¬
retically call for a consumption of energy, the demand for this purpose is
probably very small. On the other hand, it seems clearly established that
acid bodies are absorbed from the food which circulate in the blood and
increase cell activity markedly, so that when food is supplied the cells are
stimulated to a metabolic level considerably above that of the fasting animal.
8
METABOLISM OF THE FASTING STEER
This increase in cell activity resulting from the ingestion of food is likewise ‘
of no use to the body in preventing the oxidation of body material or in
supplying energy for storage. Hence the energy represented by this increase
in cell activity must also be deducted from the energy value of the food
absorbed. It is not possible at the present date to explain clearly all the
processes of digestion and the path taken by each individual component of
the absorbed food. The investigations of Graham Lusk at the Cornell Uni¬
versity Medical School are fundamental in this line. Thus far, unfortu¬
nately, they have been confined chiefly to the processes of digestion in the
dog, with certain observations on man. A full understanding of the influ¬
ence of such products upon cell metabolism in ruminants, however, can not
be obtained by work upon carnivorous animals alone. The study of the
after-effects of digestion in ruminants during the first few days without
food, i. e., the beginning stage of fasting, is therefore of great importance,
because it represents an entirely different type of digestive process.
DETERMINATION OF THE TRUE FASTING CONDITION
If food is withheld, the processes of metabolism to be measured will
eventually become reduced to the process of katabolism. With animals
having rapid digestion and absorption from the alimentary tract this stage
is reached fairly soon, but with ruminants there may be a period of several
days when the large ballast in the intestinal tract continues to add some¬
what to the energy metabolism. Ruminants especially, therefore, should
be studied, if possible, in the fasting condition in order to secure infor¬
mation on many problems. The determination of the true fasting con¬
dition, even with humans, is difficult. In the last analysis such a deter¬
mination resolves itself into an attempt to find out for how many hours
after the last meal the processes of digestion and absorption are active. The
criteria for designating the exact time when true fasting begins are by no
means sharply defined. In the case of adult humans cessation of digestion
has commonly been considered to occur 12 hours after eating, provided that
the last meal has not contained too large a proportion of protein. With
infants, the period when absorption and resynthesis of absorbed material
stop and the body begins to live solely upon previously formed body mate¬
rials is determined only with difficulty.
One of the best indices of the true fasting stage with humans is the
appearance of certain metabolic products, chiefly in the breath and urine,
in the form of acid bodies. It is commonly believed that the appearance of
acid bodies implies that free carbohydrate is no longer available for com¬
bustion, although blood-sugar is always present in normal amounts. In all
probability the formation of these acid bodies is dependent not only upon
the exhaustion of the supply of food carbohydrate, but upon the depletion
or a heavy drain on the ever-existing store of glycogen. Because of this
intermediary stage of depletion of 'carbohydrate storage, therefore, even
these acid bodies are by no means sharp indices of the moment when fasting
begins and the metabolism due to food particles ceases.
With infants, the onset of the true fasting condition, when food is not
given, is rapid. Thus, after a relatively short time of fasting, acid bodies
INTRODUCTION
9
may appear. This fact has complicated greatly the determination of the
true fasting metabolism of infants. The difficulty is by no means so great
in the case of adult humans. A lengthy series of experiments has shown
that the amount of glycogen drawn upon during the first day after the com¬
plete withdrawal of food may be as much as 100 or 200 grams, and that
thereafter a continually decreasing amount is withdrawn until about the
fifth day, when but about 20 grams enter into the metabolism.® Fasting
metabolism, therefore, may not be described solely as a protein-fat katabo-
lism, but more particularly as a metabolism in which body material fur¬
nishes the sole supply of energy. This material may or may not be organ¬
ized body material, but at least it represents material which has passed out
of the alimentary tract and has been absorbed, ready for further elaboration
or combustion, as the case may be.
Because of the prolonged digestion of large food residues by ruminants,
the attempt to establish a point as sharply defined as that just mentioned
for humans has a greater element of uncertainty. The index of the forma¬
tion of acid bodies may not be used in this case, for it is commonly believed
that a large proportion of the fermentations taking place in the alimentary
tract of the ruminant are accompanied by the formation of fatty acids
which are subsequently absorbed and burned. However, knowledge of the
influence upon metabolism of the absorption of fatty acids, and particularly
knowledge regarding the appearance of fatty acids in the urine, is not
without value in studying the metabolism of ruminants, as is shown in the
consideration of the chemistry of the urine of steers (see p. 124).
Since a clear understanding of practically all the physiological processes
of the animal organism, such as the digestion of food, the maintenance level
of metabolism, and the productive level of metabolism, can be obtained only
by reference to some level of metabolism of the animal which may be con¬
sidered as reasonably fixed and well known, the determination of the exact
time when the true fasting katabolism of large ruminants begins is therefore
an important physiological study. In an earlier report such a reasonably
fixed metabolism was defined as the “standard metabolism,”* 6 and the begin¬
ning of the second 24 hours after the last meal was arbitrarily selected as
the period of time when the greater part of the disturbing influence caused
by the presence of food would have disappeared. With humans, 12 hours
is considered a sufficient lapse of time, but it was obvious that with
ruminants the slower passage of food through the intestinal tract would
make it inevitably necessary to lengthen this time, although it was fully
appreciated that the true fasting stage of metabolism could hardly have
been reached in 24 hours.
THE PRACTICAL VALUE OF FASTING
The fact that a number of divergent feeding standards are now in use is,
in itself, sufficient testimony that no. standard has as yet been established
which will meet conditions differing essentially from those under which it
was determined. No doubt the main contributing causes for this failure to
° Benedict, Carnegie Inst. Wash. Pub. No. 77, 1907, p. 463.
6 Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 197.
10
METABOLISM OF THE FASTING STEER
supply the producers of livestock with a standard of values of different
feeds to meet the varying requirements in livestock production are found
basically in the fact that the varying ways in which the animal organism
expends energy have been either entirely ignored or have been computed on
the basis of false assumptions, so that the true net use of food for conversionj
into body-tissue was not actually obtained. In other words, the physio¬
logical accounting has been faulty or incomplete in both cases. When the
total available energy is accepted as the measure of productive use, the error
lies in a disregard of the fact that different feeds have different conversion
values. Thus, wrong net values, which alone are the measure of the effect
of feed on animal tissue, were obtained. Consequently, since the overhead
expenditure varies with different feeding-stuffs, all the factors which tend
to obscure the net tissue-building value of a food must be determined
separately. The factor of digestibility is easily measured, provided the
experimental periods are long enough and the daily food-supply is constant
enough to secure uniformity in the processes of digestion throughout the
extensive, complicated digestive canal. The influence upon metabolism of
the products of digestion is not so easily studied, and yet, as already seen,
this must be most carefully taken into consideration. A large proportion
of the energy of food absorbed is expended simply in a more active cell
metabolism of the animal, and it is only that part of the food not expended
in this increment which is of true use for the deposition of fat, flesh, or milk
production, the main purposes of the beef-producing and dairy industries.
The true measure of this “overhead” in heat-production which must be
charged against the processes of digestion and absorption has been sought
in various ways. The experimental method of attack in studying the energy
value of a food recognized that the fasting metabolism must be known, but
assumed it could be computed. Thus, anticipating probable injury to the
ruminant as the result of fasting, investigators have resorted to every other
expedient to secure evidence with regard to the so-called true net available
energy of foodstuffs. One method has been to estimate the fasting katabo-
lism from a comparison of the metabolism on two different feed-levels, the
observed difference in heat output being accredited to the difference in
feed. The error of this method lies in the assumption that the metabolism
proceeds as a straight-line function of the ration® but there is no evidence
on true fasting ruminants thus far published to support this assumption.
In view of the enormous investment involved in beef and milk production,
and in view of the fact that heretofore the economic valuation of foodstuffs
has been determined by the method just outlined, a careful experimental
investigation of the best method for determining the true value of food to
the animal, i. e., by actual fasting, is imperative. Obviously the first step
in such an experimental attack is to attempt to measure directly the true
fasting katabolism of ruminants, and subsequently to use this fasting
° Armsby (The principles of animal nutrition, New York, 1906, 2d ed., p. 430) cites the fact that
his experiments on timothy hay are the only experiments of which he knew at that time which
bear out this point. Nevertheless, he is inclined to think that this assumption is true, although
he states that “the evidence of so few experiments must naturally be accepted with some re¬
serve."
INTRODUCTION
11
katabolism as the standard for studying the true effects of varying quantities
of individual feeds.
The most logical method would seem to be to measure the fasting metabo¬
lism directly and then, by giving the animal various quantities of food, to
study accurately the increase in metabolism due to each of these various
amounts. Since the various avenues of energy-expenditure play relatively
such an important role, an estimate of the value of any given food must be
based on definite knowledge of the extent to which this food affects the
standard or fasting metabolism. Does the ingestion of food increase the
metabolism above this fasting base-line in direct proportion to the amount
of food ingested? Is the fasting metabolism the same, irrespective of the
state of nutrition previous to fasting? Is it affected by environmental tem¬
perature or by water consumption? These problems suggest that if the
element of uncertainty introduced by attempts to establish the fasting
metabolism through indirect methods could be avoided by actual measure¬
ment of the fasting katabolism, the whole complex problem of determining
the specific value of various rations would be placed upon a sounder basis.
The main object of the research reported in this monograph, therefore, was
to throw positive light upon the pure fasting katabolism of large ruminants,
and the first problem was a determination of the course of the metabolism
in steers from the time when the last food is ingested until the fasting state
is reached.
OTHER INVESTIGATIONS ON THE FASTING OF
LARGE ANIMALS
Several fasting experiments have been carried out with large animals in
the past, but, singularly enough, these are only rarely referred to in modem
literature. This may be due to the fact that some of the investigators who
have worked with large animals have published their results in remote and
almost inaccessible publications. The fasting of a large animal (weighing
400 kg. or more) for several days affords the opportunity for such an
important study, however, that the literature on the subject should be
reviewed.
MAGENDIE, 1852
The earliest instance of the fasting of a large animal is that reported by
Magendie.® A 9-year old mare, suffering from glanders, was deprived of all
food, but was allowed 6 liters of water every 24 hours, which she drank each
day until she died. Most of the observations had to deal with the blood,
samples of which were taken frequently. Magendie does not comment on
the general appearance of the animal during the first week of fasting. He
states that on the eighth day the mare did not appear to have been affected
appreciably by the fast, for she walked and ran about as usual. On the
fifteenth day her physical condition was altered but slightly, and the
decrease in flesh was hardly noticeable. Indeed, she was inclined to run
about when allowed out of the stable. On the twentieth day the appearance
of the animal had altered greatly. Her hair had changed color, grown
longer, and bristled like that of a bear. She had the appearance of being
blind, as the eyes had become glassy and seemed artificial. This change
took place rapidly, but otherwise the animal was unusually vigorous. She
was allowed to run around the stable yard, and upon hearing the crack of
a whip began to run more rapidly. It was evident that she could stand a
longer fast, although the heart-rate seemed feeble. The animal died, after
24 days of complete abstinence, except for 6 liters of water daily. Magendie
considered that this experiment was only a preliminary trial, but that it
seemed to open a new way to study. He suggested that it should be
repeated, with frequent weighings of the animal, and especially with records
of the body-temperature. The desirability of working on an animal with¬
out glanders is also pointed out. It is unfortunate that Magendie devoted
so much attention to physical characteristics and the chemistry of the
blood, for there must have been many other important observations that
apparently escaped record.
COLIN, 1862 AND 1888
Although he did not study large ruminants, such as the steer, and made
no measurements of the respiratory exchange, Colin* * 6 of Alfort (almost
° Magendie, Lemons faites au College de France, 1851-52; collected and analyzed by Faugon-
neau-Dufresne, Paris, 1852, pp. 29 et seq.
6 Colin, Bulletin Soci6t6 impfiriale et centrale de M6decine v6t6rinaire, 1862, 7, 2d series, pp.
194 and 262; also Traits de Physiologic Compar£e des Animaux, 3d ed., Paris, 1888, 2, pp. 682
et seq.
OTHER INVESTIGATIONS ON FASTING OF LARGE ANIMALS
13
'contemporaneously with Grouven; see pp. 15 to 20) reported the results
t>f several fasting experiments with horses. A healthy, vigorous, moderately
fat adult horse, weighing 405 kg., and with well-developed muscles, went
without food completely for 30 days during the month of July, but drank
water ad libitum. In 30 days he drank but 42 liters, or an average of 1.4
liters per day. Daily records were kept of the respiration-rate, the heart-
rate, and the body-temperature. The total loss in body-weight was 80 kg.
or 6.5 grams per kilogram of body-weight per 24 hours. The body-tempera¬
ture remained essentially unchanged throughout the fast. Colin states that
he will publish the details of his temperature measurements later, but
unfortunately it has been impossible to find any such later publication.
On the thirtieth fasting day, although there was nothing to indicate that
the horse would die, the animal was killed. The carcass gave the following
data:
kg.
Body . 325.0
Blood . 27.0
Skin and hoofs . 16.0
Bone and cartilages . 45.0
Muscles and tendons . 159.0
Free fat . 19.7
Viscera . 25.6
Gastro-intestinal matter . 20.2
Loss . 6.5
Total . 325.0
From this analysis Colin points out that the emaciation could have pro¬
ceeded as much farther again. There was fat under the skin near the neck
and shoulders, in the inguinal region, and on the buttocks. The fat in the
abdominal cavity formed a layer 4 to 5 cm. thick and weighed, together
with some fat in the breast, 14 kg. Fat was also found in the muscular
interstices and large-sized globules of fat were found in the cells of the liver.
A small pony of 163 kg. (which had a case of glanders) fasted for 19
days in November. He lost 39 kg. during this time, or one-fourth of his
initial weight instead of one-fifth, as in the case of the first horse. His daily
loss in weight was double that of the first animal, i. e., 12.5 grams per
kilogram of live weight.
Another horse, weighing 351 kg., which was slightly ill, lost in 18 days of
fasting 89 kg. Colin believes he lost more than the pony, because he was
very thin, and he lost twice as much per day as the horse which fasted for
one month.
Another horse, weighing 504 kg., lost 65.5 kg. in 4 days of fasting, that
is, 20.2 kg. during the first day, 13.8 kg. the second day, 16 kg. the third
day, and 15.5 kg. the fourth day. He died on the fifth day, much more
exhausted than the horse which lived for 30 days without food. But this
horse had glanders, developed a fever, and instead of using up 6 grams per
kilogram of body-weight daily he consumed 32.5 grams daily, or five times
as much as the healthy horse. This is the largest loss Colin found with any
of his horses and a loss which he thinks rarely takes place. This enormous
“consumption” is explained by the febrile condition. Colin points out that,
14
METABOLISM OF THE FASTING STEER
according to the analyses of Lassaigne,0 a horse at rest burned 2,241 grams;
of carbon and as a result of exercise burned 4,887 grams or more than
double, and he concludes that fever increases the expenditure of combustible
body material just as muscular exercise increases the expenditure of com¬
bustible material obtained from foods. The chemical result is the same in
both cases.
Still another horse, weighing 193 kg., which had undergone a slight
surgical operation, lost 8.4 kg. per 24 hours during the first 2 days of fasting,
or 43 grams per kilogram of body-weight per day instead of 6.5 grams, as
in the case of the 30-day fast. But this loss for the first 2 days was much
greater than that of the following days and should not be compared with
the average value obtained during fasts of longer duration.
Colin remarks that large ruminants may lose in the same proportion and
points out that a 1-year old heifer, weighing 146 kg., lost in the first days
of fasting 4.3 kg. in 24 hours or 29 grams per kilogram of body-weight. It
is unfortunate that the details are not given for the daily loss in weight,
the water drunk, and the urine and feces passed, so that the insensible loss
could be computed.
With the horse which fasted 30 days a study was made of the urine. At
the beginning of the experiment the urine was thick, muddy with sediment,
and alkaline. Hydrochloric acid brought about a quick effervescence and
later the formation of crystals of hippuric acid. But at the end of a few
days the urine had changed in appearance and character, becoming clear,
transparent, and acid. In fact, the urine had the essential characteristics
of the urine of a carnivorous animal.
Colin points out that it is a well-known fact that carnivora can with¬
stand fasting better than herbivora. They are accustomed to frequent fasts
and uncertainty in the securing of food and are therefore prepared naturally
in some way for irregularity in eating, an irregularity much less frequently
experienced by herbivora. The digestive tract of carnivora, which is not so
large as that of herbivora, does not suffer from the lack of ballast. One meal
supplies the carnivorous animal with food for a long time. When food from
outside sources is lacking, food of a similar nature is available within the
carnivorous animal itself. The origin of the food alone changes, but the
kind of food remains the same. When herbivora are subjected to fasting,
however, the character of alimentation is changed, for their own body-flesh
must be consumed in place of vegetable material. The herbivorous animal
therefore becomes carnivorous, for, not being able to derive any sugar or
starch from food materials, he has to borrow from his own flesh to make up
for this lack.
A remarkable fasting experiment with a rabbit is also reported by Colin.
This rabbit fasted for 37 days without either food or water. His initial
weight was 4,220 grams. On the thirty-seventh day he weighed 1,807 grams,
or considerably less than one-half of his initial body-weight. This experi¬
ment is striking, since it is the common belief of investigators in animal
physiology that rabbits withstand fasting poorly. Thus, experience with
rabbits has shown that after a relatively few days of fasting there is an
° Lassaigne, Journ. de Chimie medicale, 1846, 2, pp. 477 and 751 ; ibid., 1849, 5, pp. 13 and 253.
OTHER INVESTIGATIONS ON FASTING OF LARGE ANIMALS
15
enormous increase in the breakdown of protein tissue, the so-called “pre¬
mortal rise” in nitrogen excretion appears, and death follows rapidly
thereafter.
Colin established the fact that young animals withstand fasting less suc¬
cessfully than do adult animals, in large part because their deposit of fat
is much smaller. The influence of a fatty deposit was well shown in the
case of a goose, which, with an initial weight of 4,800 grams, lived for 44
days without food, although receiving water ad libitum. At the end of this
time it weighed 2,325 grams, or less than one-half of its initial body -weight.
After death, 446 grams of free fat were found in the body.
Although the third edition of Colin’s treatise was issued as far back as
in 1888, his discussion of fasting animals may well be recommended to all
workers in physiology. Unfortunately, data with regard to large ruminants
are missing in his reports, but the fundamental principles underlying the
influence of fasting (i. e., the effect of age and the effect of a fatty deposit)
were strikingly brought out in his observations and his discussion of results.
GROUVEN, 1864
Among the earlier researches in nutrition the work of Hubert Grouven on
the fasting metabolism of cattle demands especial attention, as it precedes
any other similar investigation by nearly 60 years. Since his fundamental
concepts of the study of nutrition problems are recognized as sound and
essential to-day, it is unfortunate that his work has been unknown or disre¬
garded during all these years by writers on animal nutrition.41 Grouven’s
work may be summarized under the three separate phases in which he made
notable contributions, namely, his general method of procedure and his
physiological and chemical studies of the problems involved. His work is
quoted here in some detail because of his sound grasp of the essentials
involved in such studies and also to remove the possible impression that
the idea of subjecting cattle to fasting as a requisite of nutrition studies is
of recent origin.
Prior to Bischoff and Voit,* * * * * 6 of whose work Grouven made extensive use,
the nutritive value of a feed was based simply on the gains in live weight
that the feed produced in the animal and no particular attention was given
to the character of the gains or losses, the assumption being that they repre¬
sented body-tissue. The fundamental incentive to Grouven’s work lay in
his recognition of the fact that great changes occur in the gross live weight
of an animal wThich have no bearing whatsoever on changes in body-tissue.
Convinced that the nutritive value of food must therefore be expressed
directly in terms of the gain or loss of muscle-tissue and fat, he studied the
problem from this point of view, thus making a radical departure from
previous methods of investigation.
° Grouven, Physiologisch-chemische Fiitterungsversuche. Zweiter Bericht uber die Arbeiten
der agrikulturchemischen Versuchsstation zu Salzmunde, Berlin, 1864. Unfortunately, these
experiments were reported in a publication rarely found in American libraries, and it is because
of the inaccessibility of these data that we review his report here in somewhat greater detail than
seems necessary in the case of those writers whose works are more generally available and known.
6 Bischoff, Der Harnstoff als Maass des StofTwechsels, Giessen, 1853; Bischoff and Voit, Die
Gesetze der Ernahrung des Fleischfressers durch neue Untersuchungen, Leipzig and Heidel¬
berg, 1860.
16 METABOLISM OF THE FASTING STEER
Method of ‘procedure — Grouven’s method of attack involved a complete
physical and chemical study of the contents of the digestive tract of the
ruminant. This study served as a physiological basis, by means of which
the relative effects of different feeds on body-tissue and on the feed residues
in the alimentary tract could be determined separately, since both are mani¬
fested in terms of live weight. He planned to study the nutritive value of
numerous individual materials in a pure form, such as sugar, starch, and
dextrine. He realized, however, that these could not be fed to a ruminant
Table 1. — Live weight, water intake, and excreta of fasting oxen, and contents of digestive
tract before and after fasting ( Grouven )
Measurement
(a)
Average
for
2 cows
Brown ox
Black ox
(f)
Average
for
2 oxen
(5 +d) +2
( b )
After
fasting
5 days
(c)
Loss
(a~b)
id)
After
fasting
8 days
(e)
Loss
(o-d)
Live weight:
kg.
kg.
kg.
kg.
kg.
kg.
Start of fast .
398
420
522
471
End of fast .
381
480
431
Loss .
38 7
42
40.4
Water intake .
14.3
35.4
24.9
Urine .
29 2
26 7
27.9
Feces .
15 9
17.2
16.6
Contents digestive tract (fill):
Water .
52.76
38.61
14.15
66 06
Dry matter —
C .
4.217
0 976
3 241
1 097
3.120
H .
0 549
0 128
0 421
0.139
0.410
O .
3 527
0 818
2 709
0 921
2.606
N .
0 131
0 036
0.095
0 053
0.078
Ash .
0.969
0.439
0.530
0.584
0.385
Total dry matter .
9 393
2 397
6 996
2 794
6 599
Total fill .
62.15
41 01
21 . 14
68 85
54.93
Fat .
0.287
0 045
0.242
0.048
0.239
Cellulose .
3 007
0 717
2.290
0 694
2.313
Water (per cent) .
85
94
96
without roughage or bulk, as such a feed alone would upset digestion.
Accordingly he decided that the nutritive effects of a standard roughage,
such as rye straw, must first be determined. Then straw, plus a definite
amount of the special purified food material, was to be fed. To establish
the influence of a basal ration of roughage, such as rye straw, he reasoned
that the fundamental starting-point or base-line would be represented by
the fasting state only, i. e., when no food is present to stimulate the
metabolism. Thus, he made his greatest contributions in the execution of an
experimental plan based on this conception, i. e., the necessity of establishing
a base-line as a preliminary to subsequent investigations. Grouven began
his first experiment in 1862, with 2 oxen and 2 cows, feeding each of them
with a basal ration of 3.5 kg. of rye straw for a period of 2 weeks. He
assumed that by the end of that time any undigested residues from previous
feed would have been eliminated and that the fill or residues in the
OTHER INVESTIGATIONS ON FASTING OF LARGE ANIMALS
17
alimentary tract would have a constancy characteristic of the daily ration,
1 e., that it would be the same in all four animals. The water intake was
likewise controlled, but only during the last four days, when each animal
was allowed 7.5 kg. daily. The oxen then fasted, one for 5 days and the
other for 8 days. The cows, on the other hand, were slaughtered and a
careful analysis was made of the quantity and character of the contents of
the alimentary tract. The oxen were slaughtered at the end of their
respective fasts and similar analyses were made.
Physiological considerations — By this experiment Grouven contributed
the first physiological data showing the effect which quantitative changes
in feed produce on the character and the amount of fill. Assuming that the
contents of the digestive tract of the two oxen would be the same at the
beginning of the fast as that of the two cows which were slaughtered at that
time (all four animals having received identical amounts of rye straw and
water) , he calculated the amount of material disappearing from the digestive
tract during the fast by deducting the amount found at the end of fasting
from the amount present at the start, and from this he determined the
amount assimilated from the straw during the fast, as shown in Table 1.
Grouven’s data bring out some significant physiological facts regarding fill,
or the feed residues in the alimentary tract. Practically nothing definite
was on record at that time regarding the total amount of fill in cattle, and
information regarding the effect of changes in feed on fill was equally
lacking. The values for total fill, which he records for his cows (not fasting) ,
correspond closely to the figures obtained by Moulton about 50 years later.
His analysis of the quantitative changes in fill that occur in different parts
of the digestive tract throws new light on the course of absorption, as indi¬
cated by the data in Table 2. The fact that the quantitative change during
Table 2. — Influence of fasting upon the contents of the digestive tract of oxen ( Grouven )
Contents of —
Average for
2 cows
(not fasting)
Ox
(5-day fast)
Ox
(8-day fast)
Average for
2 oxen
Kg.
P. ct. of
live
weight
Kg.
P. ct. of
live
weight
Kg.
P. ct. of
live
weight
Kg.
P. ct. of
live
weight
Stomach and paunch ....
48.3
12.1
34.9
9.1
59.4
12.4
47.1
10.8
Small intestine .
5.5
1.4
3.3
0.9
5.0
1.0
4.1
0.9
Large intestine .
8.5
2.1
2.9
0.8
4.5
0.9
3.7
0.8
fasting is least in the stomach and paunch and greatest in the large intestine
suggests that the excess moisture in the fill was largely absorbed before the
fill was voided. This finding offers an explanation for the occurrence of
exceedingly dry feces in our own fasting and submaintenance experiments.
One of the outstanding features shown by Grouven’s data is the great
increase in the moisture content of fill in the fasting animal, which tends to
offset the loss in dry matter. A further point of significance is the fact that
although identical amounts of rye straw and water were consumed by the
18
METABOLISM OF THE FASTING STEER
two oxen previous to fasting, the difference in their fill at the end of fasting!*
amounted to about 70 per cent, due in a large measure to the difference in
water consumed during the fast. In other words, the assumed constancy of
the conditions affecting live weight, on which he based many of his subse¬
quent calculations, was not materialized.
Fasting metabolism — From the decrease in the fecal excretion during the
fasts and the analysis of the fill at slaughter, Grouven concluded that com¬
plete fasting began on the fifth day. The results of his experiments with
5 oxen are given in Table 3. Since the loss of muscle-tissue was computed
from the urinary nitrogen in the usual manner, the nitrogen requirement of
about 50 to 60 grams daily (equal to from 1.5 to 1.8 kg. of body-flesh) noted
on the fifth day without food, apparently represented the true basal nitrogen
requirement during fasting in his experiments. Grouven reasoned that
during fasting the flesh and fat metabolism of the animal would be depressed
to a minimum level, which would not be difficult to recognize because of its
constancy. Moreover, he believed that the heat-production calculated from
the loss of flesh and fat under this condition of minimum use would also
be the same in all those experimental conditions in which the animals would
be given rations somewhat below maintenance, and that they would there¬
fore have to supplement the ration with fat and flesh from their own bodies.
His determination of the fat metabolism during fasting appears somewhat
vitiated, because of his computation of the probable loss of body-fat from
changes in live weight by using Voit’s equations, the weakness of which he
recognized. His attempt, however, to correct the defect due to dependence
on live weight by a careful analysis of the different factors that collectively
must represent the changes in gross live weight, that is, the insensible per¬
spiration, represents a real contribution to the study of nutrition problems.
Table 3. — Data for insensible loss, respiratory exchange, and heat-production, as derived from
metabolism equations ( Grouven )
Total loss in —
Per 24 hours
Heat produced
per 24 hours
Ox
Days
fast¬
ing
Average
body-
weight1
Flesh
Fatty
tissue
Insen¬
sible
loss
Car¬
bon
diox¬
ide
pro¬
duc¬
tion
Oxy¬
gen
con¬
sump¬
tion
Res¬
pira¬
tory
quo¬
tient
Total
Net*
Black .
8
kg.
501
kg.
9.74
kg.
11.84
kg.
4.19
kg.
4.66
kg.
4.50
0.75
cal.
314,850
cal.
3 13,325
Brown .
5
403
5.21
4.99
1.56
3.79
3.52
.78
11,620
13,540
Ox I (1861). .
3
431
2.32
3.33
7.16
4.70
4.31
.79
14,225
12,995
Ox I (1862). .
4
521
3.16
5.48
3.17
4.79
4.62
.75
15,245
13,230
Ox III (1861)
3
523
4.43
3.38
4.45
4.99
4.57
.79
15,065
13,550
1 Average of initial and end weights.
s Reduced to uniform conditions of 450 kg. body-weight, 15° C., and 3.5 kg. vaporized water.
3 Our computation of Grouven’s data gives values slightly different from these.
OTHER INVESTIGATIONS ON FASTING OF LARGE ANIMALS
19
Insensible perspiration — Grouven’s critical determination of the water
blalance by means of Voit’s so-called “control calculations,” based, however,
on his own analysis of the fill of slaughtered animals, represents up to the
present the only attempt on record (except our own data) to measure in
ruminants the daily insensible losses (in large part water-vapor) through
the lungs and skin. This attempt recognized the great role which water
plays in the variations in live weight, and also points out the possibilities
of the insensible perspiration serving directly as a measure of metabolism.
In other words, having determined the water intake, the water voided in
feces and urine, and the resident water in the digestive tract before and
after fasting, Grouven determined the amount and the constancy of the
water lost in vaporized form as perspiration. He pointed out that this
so-called “insensible perspiration,” or invisible daily deficit, is always con¬
sistent on a given feed-level and represents an invisible loss which pre¬
sumably can find no other means of escape except through the lungs and
skin. The source of this particular loss, as Grouven points out, is derived
from the loss of muscle or fatty tissue and of Water preexisting in the body.
The direct form in which it is lost is largely water-vapor and gaseous
products. He assumes, therefore, that the insensible perspiration represents
purely the by-products of tissue katabolism and not carbon dioxide from
the process of tissue replacement. Hence he considers differences in the
amount of water perspired by different animals as the result rather than as
the cause of differences in heat-production.
Chemical problems — Based on his exhaustive chemical studies of the fill,
Grouven concluded that none of the carbohydrates are absorbed unchanged
into the blood and directly contribute to the nutritive processes, but that
they are entirely assimilated in the form of fatty acids and glycerides,
which are formed only in the presence of alkaline solutions, i. e., primarily
in the small intestine. This revolutionary theory regarding the path of the
absorption of carbohydrates is, as a matter of fact, wholly unrecognized
even to-day, save for a reference to it by Zuntz.0 There is considerable evi¬
dence in more recent investigations supporting this theory. Although the
isodynamic law of replacement had not been established at that time,
Grouven found that the consumption of protein was smaller when rye straw
was fed than during complete fasting, thus forecasting the possibility that
fat and carbohydrates (for amount absorbed see Table 1) may protect body
protein.
Conclusion — In view of the comprehensive basis upon wrhich Grouven’s
work was planned and the extreme care with which it was carried out, and
in view, furthermore, of the fact that his whole work was finally computed
by means of Voit’s metabolism equations based on live weight, probably his
most noteworthy permanent contribution is made in his own summary state¬
ment, which follows a discussion of the uselessness of accepting live-weight
records at the beginning and end of a test as a measure of the effect of any
given food.
“The indisputable fact remains that it would never become possible to
explain the results of experimental feeding on the basis of scientific facts
Zuntz, Internat. Agrartechnische Rundschau, 1914, S, Heft 4.
20
METABOLISM OF THE FASTING STEER
or to apply the results of experimental feeding successfully to general prac¬
tice without a knowledge of the effect of food on the metabolic exchanges
which take place in muscle-tissue, fat, water, and mineral salts, a knowledge
which can be obtained only by means of a respiration apparatus and
metabolic balances.”
The potency of this statement, which amounts practically to an acknowl¬
edgment of weakness of his own metabolism measurements, lies in the
extraordinary thoroughness in detail with which his experiment was planned
and carried out.
IGNATIEF, 1883
Ignatief, in 1883, studied the influence of fasting upon the body-weights
of steers.0 Thus, 85 steers, which were being transported from Karlovka to
Moscow and thence to St. Petersburg, were divided into three groups. One
group received food and water, the second water only, and the third neither
food nor water. The animals were weighed just prior to transportation,
were weighed again at Moscow, when they had been in the cattle cars for
6 days, and again at St. Petersburg, 3 days later. A comparison of the
average loss in body-weight of the different groups, on the percentage basis,
is given in Table 4. The actual body-weights are not recorded by Ignatief.
Table 4. — Percentage loss in body-weight of steers during 9 days of partial or complete
fasting ( Ignatief )
Food condition
Percentage loss in body-weight
First 6 days
Last 3 days
Total for 9 days
Food and water .
3.11
5.6
8.71
Water only .
3.67
6.2
9.87
No food or water .
9.16
3.8
12.98
Ignatief points out that the fasting steers which received water lost less
weight than those that received neither water nor food, and probably would
have lived longer if the fasting had been continued until death. He states,
however, that water is favorable during fasting only for steers and, to a
certain extent, rabbits, but for other animals water during fasting is some¬
times harmful. Evidently no records other than body-weights were obtained
by Ignatief.
MEISSL, 1886, AND TANGL, 1912
Although our report deals primarily with the effect of fasting on rumi¬
nants, brief mention is justifiable here of the fasting studies with large swine
carried out by Meissl and Tangl. In 1886, Meissl,6 working at the agri¬
cultural experiment station at Vienna, published the results of one 3-day
“ Reported by Pashutin, General and Experimental Pathology (Pathological Physiology), St.
Petersburg, 1902, 2, Part 1, p. 156. English translation of Pashutin’s book is on file in the
Nutrition Laboratory.
b Meissl, Zeitschr. f. Biol., 1886, 22, p. 104.
OTHER INVESTIGATIONS ON FASTING OF LARGE ANIMALS
21
)
f&st with a male hog weighing 144 kg. and one 5-day fast with a male hog
weighing 122 kg. A respiration chamber employing the Pettenkofer prin¬
ciple was used, and measurements of the carbon-dioxide production were
made. Later, in 1912, Tangl0 subjected 4 male swine, two 7 months old
(40 to 50 kg.) and two l1/^ years old (110 to 120 kg.), to fasts lasting from
5 to 9 days. During this time the carbon-dioxide production, the production
of water- vapor, and the nitrogen, carbon, and energy in urine were deter¬
mined at definite intervals. The respiration chamber for average-sized
animals at the experiment station for animal physiology at Budapest was
employed, an apparatus which combines the principles of the Pettenkofer-
Voit, Atwater-Benedict, and Tigerstedt respiration chambers. The influ¬
ence of environmental temperature upon the carbon-dioxide production was
one of the factors studied.
CAPSTICK AND WOOD, 1922
The heat-production of a male hog was measured in the calorimeter
described by Capstick* * 6 during six fasts, each of from 4 to 6 days in duration,
at environmental temperatures ranging from 10° to 20° C.c The obser¬
vations extended over a period of 114 days. The hog was 10 months old at
the beginning and weighed 100 kg. ; at the end he weighed 155 kg. During
the feeding-periods (usually about 2 weeks long) between the fasts the food
was of the same general character, but was increased gradually so as to be
roughly proportional to the two-thirds power of the animal’s weight. The
hog received 7.5 liters of water daily while fasting. Readings of the various
instruments were taken at hourly or at half-hourly intervals, when the
galvanometer curve showed that the hog was asleep. At the conclusion of
the experiment the curve and the readings were carefully studied, to find
the times at which the metabolism was at a steady minimum. Considering
the variation in the age and weight of the animal during the period of
observation and the range of temperature in the different experiments, the
authors conclude that the rate of change 6f the resting metabolism at any
moment depends only on the time elapsed since the last meal and is inde¬
pendent of the age and weight of the hog and the temperature of his sur¬
roundings. The data show that the basal metabolism of the hog was not
reached until the fourth day of fasting. The results of these same experi¬
ments were used by Capstick and Wood later'* as the basis for a study of the
effect of change in temperature on basal metabolism. The critical tem¬
perature of the hog was found to be 21° C. At this temperature the basal
metabolism was minimum and amounted to 2,160 calories in 24 hours, when
he was 420 days old and weighed 136 kg. This corresponds to 904 calories
per square meter of body-surface per 24 hours. As the environmental tem¬
perature decreased below the critical temperature, the basal metabolism
increased at the rate of about 4 per cent per degree Centigrade, which corre¬
sponds to an increase of approximately 40 per cent for a temperature differ¬
ence of 10° C. (commonly found between summer and winter conditions).
_
° Tangl, Biochem. Zeitschr., 1912, 44, pp. 235 and 252.
6 Capstick, Journ. Agric. Sci., 1921, 11, p. 408.
‘Capstick and Wood, Proc. Roy. Soc. London, Ser. B, 1922, 94, p. 35.
d Capstick and Wood, Journ. Agric. Sci., 1922, 12, p. 257.
22
METABOLISM OF THE FASTING STEER
If the same law holds in the case of a steer, whose basal metabolism at 1^°
C., or summer temperature, is 6,000 calories, his basal metabolism at 8°
in an open yard in winter would be 9,000 calories. It is suggested that the
increase of 3,000 calories is met by the utilization of the thermic energy of
the coarse fodder included in the ration.
DEIGHTON, 1923
Employing the calorimeter for large animals (devised by A. V. and A. M.
Hill and improved by J. W. Capstick) at the Cambridge School of Agri¬
culture, England, Deighton0 studied the metabolism of a pig while fasting,
at various ages from 75 days to about l1/^ years. The fasting was in some
instances prolonged to 104, 109, and even 116 hours. The pig weighed
12.7 kg. at the start of the experimental season, when 75 days old, and
137.4 kg. at the end of the season, when 483 days old, and fasted on 12 differ¬
ent occasions. The author in this really excellent research concludes that
in the pig, as in human beings, the metabolism per unit of surface area is
greater in mid-youth than at any other time of life, a fact which is directly
ascribable to growth. The metabolism following the ingestion of food
reached its maximum after 5 hours and then declined.
ARMSBY AND BRAMAN, 1923-24
An abstract of results on fasting experiments with 2 cows, carried out
under the direction of Professor H. P. Armsby, of the Institute of Animal
Nutrition at State College, Pennsylvania, was reported by us in our first
monograph.* * * 6 The details of these experiments had not been published by
Table 5. — Carbon-dixoide, heat, and methane production of fasting cows ( Braman )
Cow
Time without feed
Produced per 24 hours
Carbon
dioxide
Heat
Methane
am.
cal.
am.
886 IV
24 to 48 hours .
2,223
6,743
27.4
886 IV
48 to 72 hours .
1,987
6,328
11.8
885 IV
24 to 48 hours .
2,247
6,750
33.5
885 IV
48 to 72 hours .
2,148
6,557
17.4
885 III
5 days1 .
2,034
6,577
5.8
887 III
9 days1 .
1,885
6,061
2.8
874 III
9 days1 .
2,091
6,302
4.1
1 The values given for cow 885 III represent an average for the fourth and fifth days of fasting ; !
those for cows 887 III and 874 III represent averages for the eighth and ninth fasting days.
Professor Armsby at that time, but permission was given us by him to cite j
his findings. In 1924, following Professor Armsby ’s death, Braman0 reported
the results of fasting experiments with 5 cows, including revised figures for |
° Deighton, Proc. Royal Soc., London, 1923, Series B, 95, p. 340; apparatus described by A. V.
and A. M. Hill, Journ. Physiol., 1914, 48, p. xiii, and later by Capstick, Journ. Agric. Sci., 1921,
11, p. 408.
6 Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, Table 66, p. 256.
e Braman, Journ. Biol. Chem., 1924, 60, p. 79.
OTHER INVESTIGATIONS ON FASTING OF LARGE ANIMALS 23
the two earlier experiments which Professor Armsby had privileged us to
cate. Braman’s data are summarized in Table 5.
These experiments were carried out to furnish additional data on the
ratio of carbon-dioxide to heat-production in cattle, concerning which an
earlier report® had been published in 1920, dealing, however, only with
cattle on feed. As a result of these fasting experiments and other experi¬
ments with very low feed intake new equations were derived, which, Braman
states, confirm the previous conclusion:
“The amounts of carbon dioxide and heat produced are approximately
linear functions of the feed. ... As the feed increases the amount of heat
produced does not increase as rapidly as the amount of carbon dioxide
produced. In other words, the ratio of carbon dioxide to heat has its maxi¬
mum in fasting, and decreases quite regularly, but slowly, with increase in
feed. This gradual change in the relation of the amount of carbon dioxide
and heat produced is caused by variation in the proportion of the kinds of
nutriment, from the ration and from the body, which are metabolized.”6
° Armsby, Fries, and Braman, Proc. Nat. Acad. Sci., 1920, 6, p. 263.
b Braman, Journ. Biol. Chem., 1924, 60, p. 88.
I
\
\
I
l
CHANGES IN APPARATUS AND TECHNIQUE j
Our research was carried out with the equipment as described in our
earlier monograph.® Certain significant modifications and additions made
since that time need special consideration and recording here.
CHANGES IN THE LABORATORY BUILDING
Arrangement of laboratory rooms — The general floor plan of the labora¬
tory fgr animal nutrition is shown in Fig. 1. The main floor is divided into
four rooms. The room on the right contains the respiration chamber A, the
Bullock scales M, and the water tub N. Adjoining this, but separated by a
double wall, is a small room containing the aliquoting table B and the
Respiration chamber A, with feed-box a, feed-chute b, water-trough c, and feces grid d; B, ali¬
quoting table; C, blower delivering outdoor air into chamber; D, table holding balance for
weighing absorber bottles; E, bench containing several gas-analysis apparatus; F, pipe
delivering samples of air from aliquoting table to gas-analysis apparatus ; G, G, tubes through
which samples of outdoor air are drawn for control tests of the gas-analysis apparatus; H, H,
metabolism stalls with urine tubes in center; K, K, feed-boxes; L, L, feces traps; M, scales
for weighing steers; N, water-tub; O, stairway to basement; R, R, R, R, radiators; S, sink;
T, switchboard; U, shelves and closets for supplies; W, W, tables.
balance D, for weighing the soda-lime and Williams bottles. The long,
narrow room to the left of this, on the front of the building, contains the
gas-analysis apparatus on the bench E, the switch board T, and shelves and
storage facilities U. The large room back of this contains the two metabo¬
lism stalls, showing feed boxes K, K, the traps for feces L, L, and the holes
H, H, through the floor for insertion of urine tubes.
• Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923.
24
CHANGES IN APPARATUS AND TECHNIQUE
25
, Control of environmental temperature — The importance of studying the
influence of environmental temperature made necessary facilities for a
reasonably exact control of the temperature in the metabolism stalls and in
the respiration chamber. These facilities are supplied by an adequate
steam radiation, whereby a temperature of not less than 30° C. can be
maintained even during the coldest weather, and by five windows and three
doors, the opening of which will bring about a reduction of the temperature
to a point closely approximating the outdoor temperature. When the cham¬
ber was installed in this building, space was provided on all four sides for
free circulation of air. The room containing the respiration chamber can
be shut off from the room containing the metabolism stalls by double doors,
and it is thus possible to maintain entirely unlike temperature conditions
in the two rooms, if desired. In lieu of a much preferred automatic control,
this type of temperature control served reasonably well. Owing to the wide
range of climatic conditions in America, this temperature control is a very
important factor in the study of the effect of variations in environmental
temperature upon the metabolism of beef animals. Unfortunately, with the
forms of respiration calorimeter thus far devised, the environmental tem¬
perature can be altered within only a few degrees, and it would seem as if
this problem must be attacked by means of respiration chambers in which
the temperature of the air can be greatly altered, or else a new type of
calorimeter must be devised to meet this important condition.
Motor-generator set — Although an alternating current can for the most
part be used as well as a direct current, if a number of magnets are employed
a direct current is necessary, particularly in the regulation of the electrical
by-pass. The entire equipment at Durham has therefore been arranged
with motors requiring a direct current. The regular commercial 110-volt
alternating current drives a motor connected to a direct-current generator
(110-volt) by a single shaft. The motor-generator set is installed in the
basement of the laboratory. Although it is believed that a direct current
is most advantageous for the working of the apparatus as a whole, it is
always possible to arrange for the actuation of the several magnets by
storage batteries and to use an alternating current for the motors.
Provision for Collection of Individual Urinations
The method of collecting the urine by attaching an ordinary urine funnel
to the animal and passing the outlet tube through the floor of the metabolism
stall to receptacles below has been described in an earlier report.0 The
receptacles commonly used are 5-gallon carboys, each of which rests per¬
manently on the balance of a scale. Since in many experiments, particularly
in fasting, it is essential to know the time when the urine is voided, as well
as the quantity, a simple electrical contact was installed by which a bell is
rung when a fresh flow of urine passes and raises the balance-arm of the
scale. This bell continues to ring until the carboy is again exactly counter¬
poised and the contact on the balance-arm broken. By this means it is
possible to record not only the exact moment of each urination, but likewise
the exact weight of the urine voided. The scales, which are also used for
° Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, pp. 28 and 32.
26
METABOLISM OF THE FASTING STEER
weighing feces, are the so-called “silk scales,” weighing to 125 kg. The
beam has 10-gram graduations for a beam range of 2 kg.
ADDITIONS TO RESPIRATION CHAMBER
The respiration chamber, as originally designed and used, had no pro¬
visions for feeding and watering or for the collection of urine and feces,
since it was planned primarily for short 2-hour experiments. Even during
the long fasts of 5 to 14 days the respiration experiments were only of 2
hours’ duration. It was considered desirable, however, to have a complete
record of all excreta voided during these fasts, and the first change in the
chamber was therefore made to provide for the collection of excreta while
the animal was inside the chamber. On the basis of the gratifying results
obtained during the continuous 3-day experiments in April and May 1924,
it was decided to lengthen the experiments from 2 to 24 hours or to several
continuous 24-hour periods. Furthermore, it was found highly desirable to
Fig. 2. — Feed-chute, feed-box, feces-chute, and provision for collection
of urine in respiration chamber
be able to run experiments in which the animal could be fed and watered as
usual for a day or more, and then be subjected to fasting, in order to observe
on succeeding days the influence of food on the one hand and the withhold¬
ing of food on the other hand, on the expenditure of energy. Because of this
change in the length of the experiment it was necessary to provide the
chamber with facilities for feeding, watering, and the collection of excreta.
These additions to the respiration chamber are shown in Fig. 2.
Provision for feeding — Feed is introduced through a metal chute or feed-
box of galvanized iron, firmly riveted and soldered to the front wall of the
CHANGES IN APPARATUS AND TECPINIQUE
27
chamber. It is provided with a cover, which fits into an oil-seal, and with
a trap-door, hinged on the front wall of the chamber. By means of this
trap-door the upper half of the feed-chute may be entirely closed off from
the lower half, the object being to prevent a rapid exchange of air from the
respiration chamber when the cover on top of the chute is momentarily
removed and feed is inserted. When the trap-door is open it hangs sus¬
pended by the hinges. Two flexible wires (picture-cord) connected with the
trap-door pass through the side walls of the chamber, and the trap may be
closed from the outside, without removing the cover of the feed-box, by
pulling on the wires until the door forms a firm contact with the projecting
flanges, shown in Fig. 2. The holes through which the wires are passed are
waxed, to prevent leakage of air. The bottom of the feed-chute slopes
toward the feed-box at an angle of about 45°, so that the feed slides down
into the feed-box within easy reach of the animal. The bottom of the feed-
box is reenforced on the outside with matched wooden sheathing, supported
by four legs. This gives somewhat more stability and also eliminates the
possible pull which would otherwise be exerted by this additional weight
on the front of the chamber wall. The feed-box itself is built of matched
sheathing, snugly fitted against the inside wall of the chamber, so that the
front bevel or slope of the box is continuous with the sloping floor of the
feed-chute.
Provision for water — The device for watering consists of a heavy, sheet-
metal tank, 9 inches wide, 20 inches long, and 8 inches deep, with a rounded
bottom. (See c, Fig. 1.) The water is introduced through a short pipe
attached to the bottom at the rear of the tank. This pipe is connected with
an opening in the side-wall of the chamber by means of rubber tubing, a
glass water-gage (through which the water is siphoned into the tank) being
attached to the outside of the chamber and connected with this opening.
The water-tank itself is attached at a convenient height on the outside of
the feed-box toward the room containing the absorber table, so that the
water can be supplied from the outside at any time without breaking the
air-seal of the chamber. The water-gage is connected with the opening in
the side of the chamber by a piece of rubber tubing, which forms a U -curve
below the level of the water-tank, so that the tank can be completely drained
and there will still be sufficient water in the tube to act as a seal against
passage of air.
Swivel stanchion — The original, rigid stanchion was replaced by a modem
steel swivel stanchion such as is used in dairy barns. This gives the animal
somewhat more liberty of movement and makes it easier for it to reach the
water-tank, which is placed at one side of the feed-box.
Provision for collection of urine — Although the respiration experiments
during the long fasts of 5 to 14 days were only of 2 hours’ duration, it was
desirable to collect all the urine without loss during the entire progress of
the fast, and provision was therefore made for the collection of the urine
voided while the animal was inside the chamber. The collection of urine is
relatively simple when the animals are in the metabolism stalls, but is more
complicated when they are in the respiration chamber, because of the neces¬
sity for preventing any leak in the air-seal of the chamber. At the begin¬
ning of the experimental series the urine voided in the chamber was collected
28 METABOLISM OF THE FASTING STEER
through a brass pipe attached to the side of the chamber. The end inside
the chamber was connected with the urine-funnel by a piece of garden-hosse.
To the end outside a piece of rubber tubing was attached, the other end of
the rubber tubing being inserted into a bottle containing a water-seal. !tn
the experiments beginning early in the fall of 1922, the following method
has been used in collecting the urine: A heavy brass tube, 4 inches in
diameter and 4 feet long, provided at one end with a flange about l1/^ or 2
inches in width, is projected down through a hole in the floor of the chamber,
with the flange resting on the inside of the metal floor of the respiration
chamber. This tube is held firmly in place in part by the flooring (7.6 cm.
thick) , through which it passes, and in part by 3 lag screws or bolts 2 inches
in length, by which the flange of the tube is screwed to the floor. The edges
of the flange are soldered, as are also the heads of the screws, to insure
against leakage of air. This tube is just long enough to allow for the raising
and lowering of the hose inside of it connecting with the urine-funnel. Only
a short piece of hose is used, which is weighted with lead at the bottom to
take up the slack when the animal lies down. The tube leading out of the
chamber consists of two parts. The upper section, extending downward
from the floor of the chamber, is of ordinary 4-inch tubing, fitted at the
bottom with a small valve through which water can be passed to the inside
of the water-seal. The lower section consists of a piece of %-inch brass
pipe, curved to give a water-seal, and provided at the upper end with a
brass cone which gradually widens out to 4 inches so as to fit against the
upper part of the urine-tube. The two sections are firmly held together by
a piece of automobile inner tubing of stout rubber, fastened on with clamps.
The size of rubber tubing most suitable for this purpose is that which will
require some stretch when put around the metal tubes, so that the closure
will be air-tight. The urine, as collected, flows out of the brass tube into an
appropriate container below. With this arrangement it is possible to collect
the urine throughout the entire day. Prior to its installation, the complete
24-hour collection of urine could only be made if the animal was kept stand¬
ing all the time. This apparatus for the collection of urine while the steer
is in the chamber has functioned satisfactorily.
Provision for collection of feces — The arrangement for collecting feces
consists of a chute, as shown in Fig. 2. This chute is made of galvanized
sheet metal. Its width dimensions are 3 feet by 1 foot, and it extends 3 feet
below the bottom of the floor of the chamber. The top is soldered to the
inside of the metal floor of the chamber. The bottom is provided with a
flange projecting horizontally 4 inches from the four walls of the chute.
The outside edges of this flange have a 2-inch perpendicular drop, which fits
into the oil-seal of the large metal container for collecting the feces. The
top of the chute is covered with a heavy iron grid, to prevent the animal
from stepping down into the opening. This grid is flush with the floor of
the chamber (see d, Fig. 1), but is 4 inches lower than the platform upon
which the animal rests. During an experiment the feces container is pushed
up tightly against the feces-chute, so that the inside wall of the oil-groove
fits closely against the horizontal flare of the chute, thus preventing the
feces from dropping into the oil-seal. As shown in Fig. 2, the oil-seal has
been broken and the container has been lowered several inches to secure
clearance for removal.
CHANGES IN APPARATUS AND TECHNIQUE
29
CHANGES IN THE TECHNIQUE FOR MEASURING THE
RESPIRATORY EXCHANGE
Soda-lime
As a result of the development of the many forms of respiration apparatus
used for clinical purposes, chiefly for humans, there have been placed upon
the market several kinds of soda-lime which are claimed to be much superior
to that regularly used in the Durham apparatus. Their relative merits need
not be discussed here, but it should be pointed out that practically all of
these newer types of soda-lime contain relatively large amounts of water
and therefore should not be used with this respiration chamber. The soda-
lime used in the Durham apparatus contains a minimum amount of water.0
The technique for preparing it has been described in earlier publications.6
Determination of Proportion of Air Escaping Through Openings in
Wind-chest.
The wind-chest on the absorber table has three air outlets, two each
10 mm. in diameter and the third 97 mm. The air discharged through one
or both of the 10-mm. openings may be directed through the absorption
system and its carbon-dioxide content determined, but the air passing
through the 97-mm. opening is discharged into the laboratory room. With
this arrangement, which was modeled directly after the original aliquoting
device described in a previous publication,0 simultaneous measurements of
the carbon-dioxide production may be made by directing the air from both
10-mm. openings through duplicate sets of absorbers. But in the experi¬
ments with fasting steers duplicate collections of carbon-dioxide were not
made, and hence the air from only one of the 10-mm. openings was passed
through the absorption system, the air from the other 10-mm. opening being
discharged into the room. By reducing the size of the 97-mm. opening with
different disks having openings of different sizes, the amount of the aliquot
passing through the 10-mm. opening into the absorption system may be
varied, as explained in detail in our earlier publication.^
The disk factor, or the relative proportion of air discharged into the
absorption system, remains constant even with relatively large fluctuations
in the rate of ventilation. Recent experimental work indicates, however,
that during the respiration experiment itself it is better to maintain always
the same rate of ventilation as that under which the disk factor was estab¬
lished, i. e., the discharge into the wind-chest should be reasonably constant.
The escape of air from the wind-chest is obviously dependent on the
pressure inside the wind-chest. This is equivalent to but a few millimeters
of water pressure, and yet changes in pressure inside the wind-chest do
produce disturbances in the relative discharges through the various orifices.
When variations occur in the disk factor with the same disk, it is because
° This soda-lime can be seemed through Mr. W. E. Collins, 555 Huntington Avenue, Boston,
Massachusetts, or through Stanley Jordan & Co., 93 Water Street, New York City.
k Atwater and Benedict, Carnegie Inst. Wash. Pub. No. 42, 1905, p. 29; also, Benedict, Abder-
halden’s Handb. d. biolog. Arbeitsmethoden, 1924, Abt. IV, Teil 10, p. 449.
c Benedict, Miles, Roth, and Smith, Carnegie Inst. Wash. Pub. No. 280, 1919, p. 103.
d Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 61.
30
METABOLISM OF THE FASTING STEER
of changes of air pressure in the wind-chest. Furthermore, in order to secure
uniformity and invariability in the size of the aliquot from period to period
or from experiment to experiment, the air discharged into the sampling can
with rubber-diaphragm top must always be discharged against atmospheric
pressure. This pressure, which must remain neutral, is indicated by an oil
manometer.
The best method of establishing the disk factor is, first, to set the appa¬
ratus in motion as for an experiment. The respiration chamber must then
be ventilated until it contains only pure, outdoor air. A known quantity of
carbon dioxide is then discharged into the system through a small rubber
tube, inserted directly into the pipe at some point between the wind-chest
and the blower inside the respiration chamber which forces air into the
wind-chest. Formerly it was recommended that the carbon dioxide be dis¬
charged into the intake side of this blower. The prime requisite in this
procedure is that all the carbon dioxide should be discharged into the wind-
chest without first permeating the atmosphere of the chamber. In a standard
carbon-dioxide test the gas is diffused directly into the respiration chamber
and the carbon dioxide in the residual air in the chamber is determined by
analysis. In the disk-factor test, however, any carbon dioxide escaping
back into the chamber would involve an error. Consequently, the carbon
dioxide should be introduced at a point between the blower and the wind-
chest, as the chance of leakage into the chamber is thus practically elimi¬
nated. Indeed, it may be introduced into the same pipe outside of the
respiration chamber, if desired. Subsequent weighing of the absorption
vessels, with due allowance for the carbon dioxide in the normal outdoor
air, indicates what proportion of the total amount of carbon dioxide intro¬
duced has been delivered into the sampling-can and from there passed
through the absorption system.
Table 6. — Proportion of air ( disk factor ) discharged through ab¬
sorption system according to the size of openings in wind-chest
Diameter in mm. of openings in wind-chest
Disk factor
10, 10, and 29 .
p. ct.
10.20
10’ 10, and 16 .
22.84
10‘ and 16 .
27.00
10, 10, and 60 .
3.84
‘The other 10-mm. opening was plugged with a rubber stopper.
With the introduction and measurement of carbon dioxide in the absorp¬
tion system under the above conditions, disk factors have been established
according to the different disks used in the 97-mm. opening, and for differ¬
ent rates of ventilation. These disk factors are tabulated in Table 6. The
disk factor can of course be approximately established by determining the
relative area of the three openings in the wind-chest, but this is not so
accurate a measure as the method just described.
CHANGES IN APPARATUS AND TECHNIQUE
31
Selection of Disk Opening to Meet Specific Experimental
Requirements
In any experimental period the minimum amount of carbon dioxide
absorbed should be not less than 4 grams, as the unavoidable error in
weighing the large absorbers approaches closely to 1 per cent when the
absorbers have increased in weight only 4 grams. On the other hand, when
the air-flow through the absorbers is high, so that a very large amount of
carbon dioxide is absorbed in any given period, the amount of water-vapor
carried over from the soda-lime into the sulphuric-acid bottle is also corre¬
spondingly large. As it has been found that the particular type of sulphuric-
acid bottle which may be conveniently used has an efficient maximum
absorbing capacity of 10 grams of water-vapor, this imposes indirectly a
maximum limit to the amount of carbon dioxide that can be absorbed.
Between these two extremes, therefore, one must carefully choose the size
of the disk opening to meet the conditions of the experiment.
The object in varying the size of the aliquot is mainly to direct a sufficient
proportion of the total air through the absorbers, so that the amount of
carbon dioxide absorbed, regardless of the length of period, will be within
the limits of error that might be introduced in weighing it. Thus, for small
animals, and also for animals which are fasting or on submaintenance
rations and which give off small amounts of carbon dioxide, a small disk
opening which gives a higher disk factor, i. e., a larger aliquot, should be
used. When the experimental periods are short, the aliquot should be a
larger proportion of the total amount of air than when they are long. In
the 24-hour experiments, in which the individual periods were 8 hours long,
use was made of a 50-mm. disk, which resulted in an aliquot representing
only 3.84 per cent of the total discharge of air. Thus it was possible not to
exceed the maximum absorbing capacity of the soda-lime and sulphuric-acid
bottles, even in a period as long as 8 hours.
Gas-analysis Apparatus
Importance of Gas Analysis
The aliquoting device used in connection with the respiration chamber
for steers provides for the exact determination of the carbon dioxide removed
by the ventilating air-current, but it does not indicate the change in the
carbon-dioxide residual in the chamber during the experimental period. In
computing from the carbon dioxide in the aliquot the total carbon-dioxide
production, correction must be made, however, for any change in the residual
carbon dioxide. In short half-hour periods this correction is particularly
essential, if the total carbon-dioxide production is to be determined accu¬
rately. In periods as long as 24 hours any changes in the residual carbon
dioxide might be disregarded without introducing too great an error in the
final calculations, but this procedure is not recommended. For the deter¬
mination of the change in residual carbon dioxide a small Haldane appa¬
ratus for carbon dioxide only was originally used.
In addition to the measurement of the residual carbon dioxide, gas
analysis has another use. In fasting experiments, in which the nutritive
32
METABOLISM OF THE FASTING STEER
)
state is so profoundly affected, it becomes necessary to know more accurately
the character of the food or of the body material burned. To obtain this
end the respiratory quotient must be determined, since it serves as an
admirable index of the nature of the material being katabolized. Thus, the
higher the quotient the larger the proportion of carbohydrates being burned,
and conversely, the lower the quotient the nearer the approximation to a
pure-fat combustion. The respiratory quotient is therefore of value in inter¬
preting the rate of change in the character of the metabolism during the
course of the fasting period and likewise in the subsequent feeding period.
Perhaps the most important use of the respiratory quotient, however, in
these experiments was to provide a truer indication of the calorific value of
carbon dioxide, which should be employed in computing heat by indirect
calorimetry from the carbon-dioxide measurements. The calorific value of
carbon dioxide ranges from 6.694 to 5.047 calories per liter, depending upon
whether the combustion is pure fat or pure carbohydrate. If the respiratory
quotient is actually determined, then it becomes unnecessary to assume an
average respiratory quotient or to employ the otherwise indispensable
carbon dioxide to heat ratios determined by Armsby, Fries, and Braman.0
With the original set-up of the respiration chamber for steers it was pos¬
sible to measure only the carbon-dioxide production. When the carbon-
dioxide production and the respiratory quotient are both known, however,
the computation of the oxygen consumption of the animal is relatively
simple, and from this latter value the calculation of the heat-production is
most exact. This is the main purpose of gas analysis in connection with
this respiration chamber. The direct determination of the oxygen con¬
sumption of large animals, such as steers, is difficult, because the ventilating
air-current in the respiration chamber must be large. Obviously, the closed-
circuit principle, which has been so successfully employed with humans,
would be impracticable, both on account of the complexity of the apparatus
and because of the large amount of oxygen which must be directly supplied
in a closed-circuit apparatus. Only with the Zuntz apparatus6 has an
attempt thus far been made to determine directly the oxygen consumed by
the animal. An application of the principle simultaneously set forth by
Jaquetc in Basel and Hasselbalchd in Copenhagen seemed advisable. To
secure a gas-analysis apparatus, however, that would function perfectly and
indicate with great exactness the relatively small percentage differences in
the carbon-dioxide increment and in the oxygen deficit was a problem of
no small magnitude. Experience in the Nutrition Laboratory with the
Sonden gas-analysis apparatus6 left nothing to be desired, save that the
apparatus is not portable and can not be shipped safely.
° Armsby, Fries, and Braman, Proc. Nat. Acad. Sci., 1920, 6, p. 263. These factors give the
ratio of carbon dioxide to heat for cattle, as determined in their respiration calorimeter under
definite feeding conditions, and we found them invaluable in the interpretation of our results on
undernutrition.
b Zuntz, Landw. Jahrb., 1909, 38, Ergb.-Bd. 5, p. 473; also Zuntz, VIII. Internat. Physiol.
Kongress, Wien, Sept. 1910. For further details see also Zuntz, Jahrb. d. deutsch. Landw. -Gesell-
schaft, 1912, 27, p. 180, and Umschau, No. 5, Jan. 1911; also Zuntz, Von der Heide, and Klein,
Landw. Versuchs-Stationen, 1913, 79-80, p. 806; ibid., Landw. Jahrb., 1913, 44, pp. 776 et seq.
e Jaquet, Verhandl. Naturf. Gesellsch., Basel, 1904, 15, p. 252.
d Hasselbalch, Respirationsforspg paa nyfddte B0rn, Bibliotek for Laeger, Copenhagen, 1904,
8, p. 219.
e Benedict, Carnegie Inst. Wash. Pub. No. 166, 1912.
CHANGES IN APPARATUS AND TECHNIQUE
33
Description of Gas-Analysis Apparatus
A practical gas-analysis apparatus of portable type having the desired
accuracy was, therefore, developed by Dr. T. M. Carpenter, of the Nutrition
Laboratory. This apparatus represents the principle of the Haldane appa¬
ratus applied to the determination both of the percentage of oxygen and
of carbon dioxide in the air sample, and it combines the highly desirable
Fiq. 3. — Diagram of Carpenter apparatus for exact analysis of atmospheric and chamber air
The burette A, with its smaller bulb d, and the compensator B, are immersed in water in the
container C. Intercommunication between the burette and the carbon-dioxide absorption
pipette D and the oxygen absorption pipette E is secured by taps H and J, and between the
compensating bulb B and the pipette D by the capillary tee L. The tap P provides for
preliminary adjustment to the open air. F is a mercury leveling-bulb for the burette A,
and G is a leveling-bulb for the pipette D. SS is a water reservoir, with outlet K, to protect
solution in E from air and serve as a pressure medium. Pinch-cocks a, b, and c provide for
introduction or withdrawal of liquids.
(
34 METABOLISM OF THE FASTING STEER
features of great accuracy and of transportability. One of its outstanding
characteristics is its facility of manipulation. This apparatus has already
been described in detail by Dr. Carpenter.0 Its importance in respiration
experiments of the type reported in this monograph and its general adoption
in several laboratories justify the presentation here, however, of the dia¬
grammatic sketch of the apparatus. (See Fig. 3.) The details of the
method of calibration and manipulation will be found in the two earlier
publications describing the apparatus.0 The accuracy of the apparatus is
controlled frequently by determinations of the carbon dioxide and oxygen
in samples of outdoor air, since the composition of outdoor air has been
established as constant.* * 6
The Physiological Control of Gas-Analysis Apparatus
The gas-analysis apparatus of Dr. Carpenter has been extensively con¬
trolled by analyses under conditions where ethyl alcohol is being burned in
a closed chamber and the theoretical respiratory quotient for alcohol is
found. But in respiration experiments of the character reported in this
monograph the metabolism of the animal itself serves as an automatic check
of the apparatus, since after the first few days of fasting one would expect
an approximation to a pure-fat combustion, with a respiratory quotient but
a little over 0.70. To use the actual respiratory quotient determined for an
animal as a proof of the accuracy of the gas-analysis apparatus would not,
of course, be legitimate under any conditions save during fasting. But the
fasting animal itself furnishes an excellent control of the determinations of
the respiratory exchange in a respiration apparatus. Thus, the Nutrition
Laboratory has for many years used respiratory quotients determined on
fasting geese as a test of the accuracy of various forms of respiration
apparatus. Fortunately, the first extensive application of the Carpenter
gas-analysis apparatus occurred in a series of fasting experiments, in which
it could be assumed that the katabolism closely approximated a pure-fat
combustion. It will be observed in a later section of this monograph (see
pp. 157 to 161) that the trend of the respiratory quotient in all the fasting
experiments corresponded exactly to that which one would theoretically
expect with a fasting animal.
Installation of the Gas-Analysis Apparatus at Durham and Correction in Cal¬
culation of Carbon-Dioxide Production Necessitated by Its Use
In the earlier experiments with this respiration chamber only the carbon-
dioxide content of the air inside the chamber was determined, a small
Haldane apparatus being used for the purpose. After the development of
the exceedingly accurate Carpenter apparatus, the air leaving the chamber
was analyzed to determine both the carbon-dioxide increment and the
oxygen deficit created by the animal. Indeed, such analyses were made in
most of the experiments reported in this monograph. An air sample may be
taken at the exact beginning or end of a period, either by means of the well-
° Carpenter, Journ. Metabolic Research, 1923, 4, p. 1; see, also, Benedict, Abderhaiden’e
Handb. d. biolog. Arbeitsmethoden, 1924, Abt. IV, Teii 10, p. 628.
6 Benedict, Carnegie Inst. Wash. Pub. No. 166, 1912.
CHANGES IN APPARATUS AND TECHNIQUE
35
known Haldane gas-sampler or by means of the sampler designed by
Bailey.0 When gas samples are to be stored and subsequently analyzed,
the Bailey sampler is the better. It is important at this point to emphasize
that the gas-samplers, as well as the mercury itself, must be dry, and the
air, if it is to be stored, should be sampled after passing through sulphuric
acid and therefore dry, for when moist samples are stored for 12 or more
hours there is invariably a loss of carbon dioxide.* 6 In our case, however,
analyses were made continuously and samples were rarely stored.
The gas-analysis apparatus was set up in a room adjoining that in which
the absorber table was placed, an air sample being conducted from the
absorber table to the gas-analysis apparatus by means of a ^4-inch metal
pipe. Sufficient pressure to insure a steady flow of air was easily secured
by tapping the pipe conducting the air from the positive blower to the
absorbers at a point near the blower, this being the point of highest pressure.
The samples used for analysis contained the normal amount of moisture® in
the chamber atmosphere, as they were taken before the air passed through
the first sulphuric-acid container. Two pet-cocks in series were employed
to regulate the air-current going to the gas-analysis apparatus. One was
set open permanently, just wide enough to allow the proper amount of air
to flow through the sampling-tube to the gas-analysis apparatus ; the other
was used as a shut-off. Hence the amount of air thus passing through the
tube was dependent solely upon the length of time the pet-cock was open.
In using the apparatus, the shut-off was opened exactly 2 minutes before
the end of the period, allowing the air to flow to the gas-analysis apparatus.
At the exact end of the experimental period this pet-cock was shut off and
the time the valve had been opened was noted with a stop-watch. Obviously
the amount of air thus diverted from the aliquot to the gas-analysis
apparatus carried with it carbon dioxide, which was diverted from absorp¬
tion in the soda-lime bottles. Since the air was analyzed, however, by
volumetric analysis, it was only necessary to determine the volume diverted
during the time the valve had been open, from which one could easily
compute the amount of carbon dioxide lost from the aliquot. This volume
was accurately measured for different rates of ventilation with a small gas-
meter placed at the outlet of the sampling-tube. A table of factors was then
drawn up, showing the volume of air flowing through the sampling-pipe for
the varying lengths of time that the pet-cocks had been open. Since the
rate of flow through the sampling-pipe changed very little, whether the
ventilation-rate of the sampling current was 24 or 36 cubic feet per half
hour, the average of the different rates of ventilation between these limits
was taken as a constant in preparing the table of factors. The amount
of carbon dioxide computed from the volume of air passing through the
sampling pipe and the determined percentage of carbon dioxide was added
to the weight of carbon dioxide collected in the absorbing vessels, prior to
the calculation of the total amount of carbon dioxide produced during the
experimental period.
° Bailey, Journ. Lab. and Clin. Med., 1921, 6, p. 657; ibid., Journ. Biol. Chem., 1921, 47, p. 281.
6 Benedict, Carnegie Inst. Wash. Pub. No. 166, 1912, pp. 106 et seq.
e When samples are to be stored, they must be taken dry, preferably in a Bailey Bampler, and
taken at a point between the sulphuric-acid bottles and the soda-lime bottle, i. e., usually from a
pet-cock in the pipe rising through the table and conducting air to the soda-lime bottles.
36
METABOLISM OF THE FASTING STEER
Procedure for Most Accurate Determination of Respiratory Quotient
When it is desired to determine the respiratory quotient with great
accuracy, the carbon-dioxide increment and the oxygen deficit should be
large, as the possible error involved in the gas-analysis is thereby, theo¬
retically at least, reduced. Hence, in these experiments, as a matter of
safeguard, it was aimed to establish a high content of carbon dioxide (circa
1 per cent) in the air of the chamber just before the beginning and just
after the end of the experiment and to determine the respiratory quotient
from these highly saturated samples. This condition was obtained by
leaving the animal in the chamber approximately one hour without venti¬
lation. Respiratory quotients were also determined throughout the experi¬
ment, but not with such a high carbon-dioxide content of the chamber air.
With small animals or animals on submaintenance rations or fasting, the
carbon-dioxide production per half hour is very low, and in such cases this
procedure for determining the respiratory quotient accurately becomes a
necessity.
Principles Underlying Control Tests of Respiration Chamber by
Admitting Known Amounts of Carbon Dioxide
The importance of making frequent tests of the operating efficiency of
the apparatus can not be over-emphasized. The general principle of con¬
ducting gas checks has already been described.0 At least two procedures
are possible. In the first place, the respiration chamber may be thoroughly
ventilated with outdoor air and carbon dioxide may then be introduced
into the chamber more rapidly than it is withdrawn. At the end of a half
hour (the length of an ordinary period) one can weigh the carbon dioxide
accumulated in the soda-lime bottles, correct for the normal carbon-dioxide
content of the air entering the soda-lime bottles, correct for any carbon
dioxide diverted in the air sample going to the gas-analysis apparatus, and
finally, compute from the disk factor the total amount of carbon dioxide
that has left the respiration chamber. The final value thus obtained must,
in this particular case, be increased by a large corrective factor due to the
accumulation of carbon dioxide inside the chamber. Indeed, when the air
of the chamber is of outdoor composition at the start, this correction factor
may represent three-fourths or more of the total amount of carbon dioxide
introduced. Obviously, therefore, this particular type of gas-check would
test the accuracy of the gas-analysis apparatus (i. e., the determinations of
the residual carbon dioxide) and the measurement of the volume of the
chamber to a much greater extent than it would the accuracy of the mechan¬
ical aliquoting device and of the absorption system. Indeed, a test of the
chamber might be made with a very low ventilation-rate, so that the carbon
dioxide would accumulate inside. In such a test the rotary blower dis¬
charging air from the chamber would be maintained at a speed only suffi¬
ciently high to preclude any back diffusion of air out of the loosely sealed
door. Under these conditions it would be possible to carry out a test in
which 90 per cent of the carbon dioxide introduced would accumulate in
the chamber. Such tests have, as a matter of fact, actually been carried
out, and are usually successful.
“Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, pp. 70 et seq.
CHANGES IN APPARATUS AND TECHNIQUE
37
The second ideal method is to have the rate of ventilation and the intro¬
duction of carbon dioxide so nearly balance that the residual carbon dioxide
would be the same at the end as at the beginning of the period. Under these
conditions there would be no correction for the residual carbon dioxide, and
the test becomes purely a test of the mechanical aliquoting device and the
absorption of carbon dioxide. This second method is believed to be the best.
It necessitates, however, an accumulation of the carbon dioxide in the air
of the chamber prior to the true test to a point at which the relationship
between addition and removal can be held constant during the subsequent
test. The point will obviously vary with the amount of carbon dioxide
introduced per half hour. The amount per half hour should, theoretically
at least, closely approximate the amount which will probably be produced
by the animal under study. Indeed, gas-checks are usually made with this
chamber under conditions which closely represent those produced by the
animal under investigation.
Table 7. — Typical calculation of a 4-hour carbon-dioxide check test
(12h04m p. m. to 4h05m p. m., March 26, 1924)
Weight of absorbing vessels at end.
Weight of absorbing vessels at start
grams .
do. .
5,777.85
5,761.10
CO2 absorbed from aliquot of outgoing air
do.
16.75
Volume of aliquot of outgoing air . cubio feet. .
CO2 in aliquot from outdoor air1 (1.23 X 1.6) . grams.
CO2 in aliquot from chamber (16.75 — 1.97) . do.
CO2 in air escaping through valve . do.
Total CO2 in aliquot from cylinder (14.78+0.09) . do.
'14.87 X 100>
. , . . . . . / 14.87 X 100\
CO2 in total outgoing air8 1 - — — - - 1 .
V 3.84 /
do.
Residual CO2 in chamber at end . . . p. ct. .
Residual CO2 in chamber at start . do. .
123.0
1.97
14.78
0.09
14.87
387.24
0.331
0.030
Change in residual CO2
do.
0.301
Change in residual CO2 corrected5 (0.18X0.301X1,000) . grams.
CO2 corrected by residual (387.24+54.18) . do. .
54.18
441.42
Weight of steel cylinder at start
Weight of steel cylinder at end .
do.
do.
1,402.55
961.40
CO2 admitted to chamber .
Per cent CO2 withdrawn from chamber
/ 441.42 X100\
\ 441 . 15 )
do. .
p. ct..
441.15
100.06
1 Estimated that each 100 cubio feet of outdoor air contains 1.6 grams carbon dioxide.
! 3.84 equals percentage of total outgoing air actually passing through absorption system, i. e.,
when the 10, 10, and 50 mm. openings are used. (See Table 6, p. 30.)
5 Estimated that each 0.001 per cent carbon dioxide corresponds to 0.18 gram carbon dioxide,
as the volume of air in the chamber is about 9,000 liters.
In connection with the 24-hour experiments having periods of 8 hours’
duration, a gas-check extending over 4 hours was made. For this test the
disk with the 50-mm. opening was used in the larger aperture in the wind-
chest, the disk factor for which had been established to be 3.84 per cent.
The results of such a test are tabulated in Table 7.
ANIMALS USED IN EXPERIMENTS
Our first extensive research with ruminants was made with 14 steers in
groups of from 2 to 5 animals.0 The uniformity of results shown between
the individuals in each group, both on maintenance and on submaintenance
feed-levels, indicated that two well-selected animals would be sufficient for
a study of fasting, provided they do not vary materially in age, breeding,
and conformation. If in any experiment, however, two similar animals do
not give approximately the same result, then the particular factor under
investigation should be studied with a larger group. Accordingly, most of
the work on fasting was carried out with two adult steers (C and D), each
weighing about 600 kg. These animals were reasonably close duplicates of
two of the large, full-grown steers (A and B) studied in the research on
undernutrition. In order to study the influence of size and age on fasting
metabolism, a pair of steers about 12 months of age (E and F) were likewise
secured. The animals in each pair were essentially physiological duplicates.
Thus, to a certain extent each experiment was carried out in duplicate, each
pair of animals receiving absolutely the same treatment with regard to
environmental temperature, feed, and general handling.
a Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923.
38
GENERAL PLAN OF RESEARCH
FASTING ON DIFFERENT PLANES OF NUTRITION
Since the fundamental problem under investigation was to determine the
influence of fasting upon the physiological behavior of beef steers, par¬
ticular attention was centered on a study of the respiratory exchange, the
heat-production, and the composition of the urine. The nutritive plane upon
which the animals were living before the fast was purposely altered, to
determine the influence that such differences in the nutritive level would
exert on the well-known drafts upon the body organism for maintenance
of life during subsequent fasting. Thus, several fasts were carried out with
steers C and D in a well-nourished condition, that is, after they had been
gaining flesh for some time. In four instances the feed-level previous to
fasting was approximately maintenance. In two instances steers C and D
were subjected to fasting after having been on pasture for several months,
when they were in a condition approximating that of animals in wild life,
having a water-rich fill of green grass, the flesh being soft, and the body
more or less water-logged. They also fasted after a fairly prolonged period
upon submaintenance rations, consisting of approximately one-half of the
usual caloric intake necessary for maintenance. Since the changes occurring
in the animal organism during the first two or three days of fasting are
most profound, the effect of repeated 48-hour periods of fasting with weekly
intervals of refeeding was studied, to secure added information on this point.
Steers E and F were likewise studied during fasting after submaintenance
feeding, and with them a special study was made comparing the metabolism
during 2 days on feed with that during 2 subsequent days of fasting. In this
series maintenance and submaintenance feed-levels were contrasted, and the
relative effects of timothy and alfalfa hay were also studied. The experi¬
mental series did not include fasting experiments at the height of fattening.
SUBSIDIARY PROBLEMS
Undernutrition — Since these fasting experiments followed different nutri¬
tive planes, each pair of steers was fed on submaintenance rations previous
to one fast, and further data were thus secured on the influence of under¬
nutrition upon the metabolism of steers, which supplement the findings in
the earlier report on undernutrition.®
Reaction to ingested food after fasting — The effect of the ingestion of
food on metabolism was determined from various standpoints. In the first
place, observations were made of the effect of the first feed after fasting,
when the stomach was practically devoid of any food. With steers C and D
the metabolism was also measured under the regular conditions of feeding,
over periods lasting from 2 to 8 hours. In these cases the animal was put
into the respiration chamber immediately after having consumed a regular
feed. Of greater importance was a series of continuous four-day respiration
experiments with steers E and F, in which the influence of the ingestion of
° Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923.
39
40
METABOLISM OF THE FASTING STEER
food was studied during a period of 2 days of regular feeding immediately
followed by 2 days of fasting.
Environmental temperature — Our earlier research0 suggested that the
metabolism of ruminants occasionally decreases with a falling temperature,
a phenomenon at variance with all popular conceptions and previous inves¬
tigation on this subject. In the experimental series beginning in January
1923, therefore, it was planned to include a study of the effect of environ¬
mental temperature on metabolism. Wide ranges in temperature were pur¬
posely selected, and the metabolism of the animals was measured at these
different temperatures, both while they were fasting and while they were on
different feed-levels, including maintenance and submaintenance.
Body position — The importance attached to the influence of standing and
lying upon the metabolism of ruminants has brought forth considerable dis¬
cussion on the subject, resulting in the recomputation of much previously
published work.* 6 It seemed desirable, therefore, to supplement our earlier,
rather fragmentary findings.0 As it is a habit of cattle not to lie down for a
very long period at a time, it is unfortunately impossible to measure the
metabolism during a long period of lying only. The problem is not so
difficult when the steers are standing, as they can readily be forced to stand.
A few observations of the metabolism with the steer in the lying and stand¬
ing positions were made during the period of this research. These were
supplemented by others made during the winter of 1925-26. From these
later results it becomes apparent that the subject demands a far more
critical investigation than was at first anticipated. Therefore we do not
feel justified at the time of sending this manuscript to the printer (summer
of 1926) in discussing this important problem, since our data are as yet by
no means complete.
Insensible loss — Throughout this research records were kept in 24-hour
periods of the body-weight, the amounts of feed and water consumed, and
the weights of feces and urine excreted. The data are therefore available
for computing the daily insensible loss of each of these four steers during
the entire experimental season, both when they were fasting and when on
feed. These data furnish new material in the study of the physiology of
ruminants which was not obtained in our earlier research on undemutrition.d
In view of the close correlation between the insensible loss and the metabo¬
lism already noted with humans, e it was considered advisable to determine
whether this correlation also exists with ruminants and how it is affected
by fasting as compared with different feed-levels.
° Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, pp. 219 and 301.
6 Fries and Kriss, Am. Journ. Physiol., 1924, 71, p. 60.
* Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 215.
d Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 85.
‘Benedict, Bull. Soc. Sci. d’Hygiene Alimen., 1923, 11, p. 357; ibid., Schweiz, med. Wochen-
echr., 1923, 53, p. 1101; ibid., The correlation between perspiratio insensibilis and total metabo¬
lism, Collection of articles dedicated to the 75th birthday of Prof. I. P. Pawlow, published from
the Institution of Experimental Medicine in Leningrad, 1924, p. 193; also, Benedict and Root,
Arch. Intern. Med., 1926, 38, p. 1.
CHRONOLOGY OF THE FASTING RESEARCH
The first fasting experiment was designed as a general exploratory meas¬
ure, to discover how steers would react when completely deprived of food,
since the opinions with regard to the probable outcome were greatly diversi¬
fied. The general plan of the research as a whole rapidly shaped itself at
the conclusion of the first fast, and a series of fasts of 5 to 14 days, as well
as a series of 2- and 3-day fasts, were successfully carried to completion
with steers C and D. Later the factor of age was introduced with two
younger steers (E and F) , and the plan of research was enlarged to include
continuous 4-day respiration experiments. A chronological list of the fasting
experiments is given in Table 8, in which the length of the fast represents
the time between the last feed given before the fast and the first feed given
after the fast. The fasting experiments with steers E and F between Decem¬
ber 1924 and May 1925 represent in each case a continuous 2-day sojourn
in the respiration chamber without food, immediately preceded by a con¬
tinuous 2-day respiration experiment during which the steer received feed
(maintenance or submaintenance rations) at the usual hours.
Table 8. — Chronological list of fasting experiments
Steer and date
of last feed
Length of
fast1
Steer and date
of last feed
Length of
fast1
Steer and date
of last feed
Length of
fast1
Steer C:
days
hrs.
Steer D:
days
hrs.
Steer E:
days
hrs.
Dec. 6, 1921
7
9
Dec. 6, 1921
7
9
Feb. 12, 1924
5
3
Jan. 4, 1922
10
10
Jan. 4, 1922
10
10
Apr. 8, 1924
4
2J
Apr. 17, 1922
14
71
Apr. 17, 1922
14
71
Dec. 14, 1924
2
9
June 1, 1922
6
ll
June 1, 1922
5
4
Jan. 14, 1925
3
1
Nov. 6, 1922
10
1
Nov. 6, 1922
8
3
Feb. 3, 1925
3
1
Jan. 3, 1923
3
3l
Jan. 9, 1923
3
4
Mar. 1, 1925
2
9
Jan. 15, 1923
2
, .
Jan. 17, 1923
2
3
Mar. 18, 1925
2
9
Jan. 21, 1923
2
4
Jan. 25, 1923
2
3§
Apr. 15, 1925
2
9
Jan. 28, 1923
2
4
Feb. 1, 1923
2
1*
May 5, 1925
2
23
Feb. 5, 1923
2
31
Feb. 8, 1923
2
4
Feb. 11, 1923
2
4
Feb. 14, 1923
2
si
Steer F:
Feb. 18, 1923
2
3l
Feb. 22, 1923
2
31
Feb. 12, 1924
6
21
Mar. 1, 1923
2
31
Mar. 5, 1923
2
41
Mar. 31, 1924
4
21
Mar. 8, 1923
2
31
Mar. 13, 1923
2
31
Dec. 19, 1924
2
9
Mar. 15, 1923
2
3|
Mar. 20, 1923
2
3*
Jan. 20, 1925
3
1
Mar. 22, 1923
2
31
Nov. 4, 1923
4
22
Feb. 13, 1925
3
1
Nov. 4, 1923
5
19
Mar. 3, 1924
9
3
Mar. 25, 1925
2
9
Mar. 3, 1924
10
3i
May 13, 1924
4
2
Apr. 22, 1925
3
1
Apr. 22, 1924
4
2
Nov. 11, 1924
2
. .
May 12, 1925
3
1
Nov. 11, 1924
2
1 Length of fast signifies time between withholding of feed and resumption of feeding.
DETAILS OF THE EXPERIMENTAL CONDITIONS
Continuous daily records were kept throughout the entire experimental
season each year of the body-weight, weights of drinking-water and feed,
and weights of urine and feces. From these data it has been possible to
compute the daily insensible perspiration. In addition, daily records were
also made of the temperature of the drinking-water, the temperature of the
41
42
METABOLISM OF THE FASTING STEER
4
metabolism stalls in which the animals were kept, the rectal temperature,
and the heart-rate. Various body measurements were made periodically,
but only the chest circumference was recorded daily, since it was believed
that this is the best single measurement indicative of any change in flesh
or organized body-tissue.
The routine observed in securing the body-weights was as follows: At
exactly 2 p. m. each day the same steer was led onto the scales and weighed.
He was then given water to drink from a tub, and again weighed and put
into the stall, and the next steer was weighed in like manner. The tub of
water was weighed before and after each animal drank, the decrease in
weight representing the weight of water consumed and also serving as a
check on the measurement of the body-weight, since the increase in body-
weight should agree with the decrease in weight of the tub. Beginning with
November 11, 1924, the body-weights were taken at 4h 30m p. m. instead of
at 2 p. m. These weights, in fact all records except chest circumference,
heart-rate, and body temperatures, were checked by a second observer.
Native hay, comprising at least 75 per cent of timothy hay, was given to
all four steers from November 1921 until March 1925, when alfalfa hay
was fed. The meal mixture given to the adult steers, C and D, consisted of
a mixture of equal parts by weight of corn meal, linseed meal, and wheat
bran. The young steers, E and F, however, were given a mixture of equal
parts by weight of linseed meal and wheat bran, without the corn meal, the
object being to promote growth.
During the periods of maintenance feeding all four steers received hay
twice each day, i. e., at 4h 30m p. m. and at 8 a. m. The meal mixture during
the feeding-period from November 26, 1921, to December 6, 1921, was given
only once each day, at 7 a. m., but thereafter during maintenance feeding
it was given twice daily, at 7 a. m. and about 3h 30m p. m. in the case of all
four steers. During the submaintenance period in the spring of 1923, steers
C and D were fed hay twice each day, that is, one bag containing 4.5 kg.
of hay was fed during the 24 hours, approximately one-half of the bag being
given in the late afternoon and the rest on the following morning. No meal
was given to steers C and D at this time. In the case of steers E and F, in
the submaintenance period in 1923-24, hay was fed only once daily, i. e., in
the morning, and meal in the late afternoon. In the submaintenance period
in 1924-25, however, these steers received hay in the afternoon only and
no meal at all. No meal was fed to steers C and D after June 23, 1923, or
to steers E and F after April 18, 1924.
The 24-hour periods for the collection of data for all 4 steers began and
ended at 2 p. m. during the experimental season from November 1921,
through May 1924, except for the fast in March 1924, with steers C and D,
when the day began and ended at 7 a. m. In November 1924, and there¬
after through the winter and spring of 1925, the daily periods were begun
and ended at 4h 30m p. m.
OBSERVATIONS ON MATURE STEERS C AND D
Steers C and D were purchased and brought to the agricultural experi¬
ment station at Durham, New Hampshire, on October 26, 1921. According
to the statement of the farmer from whom they were purchased, these steers
CHRONOLOGY OF THE FASTING RESEARCH
43
were at that time about 3% years of age. They were both predominantly
of Shorthorn breeding, but steer C showed a trace of some other blood by
his black muzzle. After their arrival they were kept in temporary quarters
until November 26, 1921, when the metabolism stalls were completed in the
laboratory for animal nutrition. Their first feed in the metabolism stalls
was given at 4h 30m p. m., November 26, 1921, and thereafter the regular
routine of procedure, as already outlined, was carried out. A supply of
hay rations was weighed out for a month in advance, and samples were
taken for analysis, but the meal ration was weighed out daily. The feed
refused was removed and weighed before the next 24-hour feeding-period
began, and a record was kept of the exact amount uneaten.
Fasting experiments were made with both steers on December 6 to 13,
1921, and January 4 to 14, 1922. During the period between February 2
and March 21, 1922, steers 0 and D had to be kept in temporary quarters
again, owing to a fire in the laboratory and the time required for repairs,
so that the daily records could not be secured.
Details of the 14-Day Fast in April 1922
A complete picture of a fast can be obtained only from records which
indicate the physiological condition of the animal before the fast, during
the fast, and during recuperation. It seems inadvisable to incur the expense
which would be involved in publishing the huge amount of data representing
in detail all these various physiological levels. Accordingly, although in the
discussion of results the detailed data secured during the progress of each
fast will be given in the various tables, the complete daily data for the
periods prior to and following the fast are given only for the 14-day fast.
(See Tables 9 and 10.) The various recuperation periods following the
fasts which did not exceed 5 to 7 days were rapid and similar, and present
nothing unusual which would warrant the expense involved in publishing in
detail the extensive data secured during these periods. During the longer
10- and 14-day fasts, however, the recuperation was much slower and the
data for the refeeding period following the 14-day fast are therefore given
in detail.
In Tables 9 and 10 the dates when respiration experiments were made are
indicated by asterisks. The experiments in the respiration chamber were
usually made in the morning and in all cases where the “standard metabo¬
lism” (see p. 228) was to be measured the afternoon feed of the day prior to
the experiment and the morning feed on the day of the experiment were
withheld, so that the animal might be studied at least 24 hours after eating.
The body-weights and weights of water recorded in these two tables were
secured at 2 p. m. The measurements of the chest-girth were taken just
before the steer was weighed. The data for water, feed, excreta, and
insensible loss represent total amounts for 24-hour periods, beginning at
2 p. m. on the given date. The containers for the excreta, both feces and
urine, were removed at 2 p. m., i. e., immediately after weighing the animal,
so that the weights of excreta are those amounts actually voided between
2 p. m. of one day and 2 p. m. of the next day.
The fast in April 1922 was begun after the steers had been on a constant
ration of hay and meal for 17 days, i. e., since March 31, 1922. An exami-
44
METABOLISM OF THE FASTING STEER
Table 9. — Statistics of experiment of April 17 to May 1, 1922 , steer C
Date
Body-weight
Chest-
girth
Water
Feed1
Excreta
Insen¬
sible
loss
Stall
temp.
Total
Change
Total
Temp.
Hay
Meal
Feces
Urine
1922
kg.
kg.
cm.
kg.
°C.
kg.
kg.
kg.
kg.
kg.
°C.
Apr. 10. . .
602.8
+ 4.2
201
35.6
12
8.98
3.00
26.57
4.35
17.8
22
Apr. 11. . .
601.6
- 1.2
201
32.2
12
8.90
3.00
25.60
4.39
13.0
13
Apr. 12. . .
602.8
+ 1-2
201
32.0
12
8.92
3.00
23.30
4.22
13.0
13
Apr. 13. . .
606.2
+ 3.4
201
33.8
11
8.96
3.00
26.31
4.58
14.2
18
Apr. 14. . .
606.8
+ 0.6
202
32.8
13
8.94
3.00
23.08
4.03
17.2
21
Apr. 15. . .
607.2
+ 0.4
201
34.4
13
8.94
3.00
23.20
4.65
15.4
17
Apr. 16. . .
610.2
+ 3.0
198
33.6
15
8.77
3.00
26.38
4.54
16.6
20
Apr. 17*..
608.2
198
32.0
14
0.00
0.00
20.43
5.25
12.6
20
Apr. 18*..
602.0
- 6.2
199
12.4
14
0.00
0.00
7.08
7.72
6.0
20
Apr. 19*..
593.6
- 8.4
198
4.6
14
0.00
0.00
4.82
5.26
7.2
20
Apr. 20*..
581.0
-12.6
196
0.0
13
0.00
0.00
3.95
3.16
2.4
15
Apr. 21*..
571.4
- 9.6
197
3.8
13
0.00
0.00
2.91
2.03
3.2
20
Apr. 22*..
567.0
- 4.4
196
9.6
17
0.00
0.00
3.35
3.84
4.2
22
Apr. 23*..
565.2
- 1.8
196
0.2
14
0.00
0.00
2.25
2.18
3.8
22
Apr. 24*. .
557.2
- 8.0
196
4.4
20
0.00
0.00
3.22
1.92
3.6
22
Apr. 25*..
552.8
- 4.4
196
3.2
17
0.00
0.00
1.28
2.09
4.0
23
Apr. 26*..
548.6
- 4.2
194
4.6
18
0.00
0.00
0.69
2.12
4.8
20
Apr. 27*..
545.6
- 3.0
194
5.2
18
0.00
0.00
2.60
4.63
2.0
22
Apr, 28*..
541.6
- 4.0
193
0.0
19
0.00
0.00
1.21
2.01
3.0
21
Apr. 29*..
535.4
- 6.2
193
2.2
19
0.00
0.00
1.14
1.61
3.6
21
Apr. 30*..
531.2
- 4.2
193
4.8
17
0.00
0.00
0.92
2.35
3.4
21
May 1*. .
529.4
- 1.8
193
1.8
16
3.79
0.00
0.85
0.97
4.0
19
May 2...
529.2
- 0.2
193
15.4
16
4.46
0.00
2.38
1.71
6.6
22
May 3 . . .
538.4
+ 9.2
193
24.4
17
7.31
0.00
7.08
2.47
7.0
19
May 4 . . .
553.6
+ 15.2
193
20.2
15
7.33
0.00
13.73
2.49
6.2
14
May 5...
558.8
+ 5.2
193
21.4
16
7.18
0.00
15.48
2.26
7.4
19
May 6 . . .
562.2
+ 3.4
196
20.6
13
8.36
0.00
18.56
2.90
8.0
19
May 7...
561.8
- 0.4
194
32.8
18
8.13
0.00
20.13
2.72
8.0
18
May 8 . . .
571.8
+ 10.0
196
20.6
13
0.00
0.00
18.86
3.78
5.2
18
May 9*..
564.6
- 7.2
193
0.6
16
8.98
4.00
13.11
3.09
10.4
21
May 10. . .
551.6
-13.0
193
31.0
15
8.31
4.00
16.70
4.03
12.6
21
May 11 . . .
561.6
+10.0
193
32.2
15
6.96
4.00
20.02
3.04
13.2
19
May 12...
568.6
+ 7.0
193
36.0
12
8.42
4.00
22.60
2.87
14.6
20
May 13. . .
577.0
+ 8.4
196
35.8
12
8.24
4.00
24.41
3.17
15.0
19
May 14. . .
582.4
+ 5.4
196
35.8
12
8.58
4.00
26.06
3.23
17.0
20
May 15. . .
584.4
+ 2.0
196
38.6
13
8.93
4.00
25.98
3.82
17.4
20
May 16. . .
588.8
+ 4.4
196
39.2
14
8.84
4.00
26.54
4.62
15.2
17
May 17. . .
594.4
+ 5.6
197
37.8
14
8.83
4.00
29.87
4.48
14.6
17
May 18. . .
596.0
+ 1.6
198
39.2
15
8.65
4.00
32.43
7.94
15.4
17
May 19. . .
592.0
- 4.0
197
38.2
13
8.95
4.00
27.50
7.13
17.8
20
May 20. . .
590.8
- 1.2
196
39.2
13
8.70
4.00
32.58
3.26
18.8
22
May 21...
588.0
- 2.8
196
38.6
13
8.96
4.00
30.08
3.54
20.4
24
May 22. . .
585.6
- 2.4
196
38.8
13
8.92
4.00
27.92
4.08
16.4
22
May 23. . .
589.0
+ 3.4
196
39.4
15
8.95
4.00
26.98
4.62
16.8
20
May 24. . .
593.0
+ 4.0
196
40.8
14
8.99
4.00
28.18
4.40
16.4
21
May 25. . .
597.8
+ 4.8
197
37.4
13
8.98
4.00
25.10
4.47
17.6
22
May 26. . .
601.0
+ 3.2
198
39.2
12
8.87
4.00
28.81
4.56
16.6
21
May 27...
603.2
+ 2.2
199
39.6
14
8.92
4.00
27.59
5.18
14.0
16
May 28. . .
609.0
+ 5.8
199
35.0
14
8.99
4.00
29.34
6.57
17.2
22
May 29. . .
603.8
- 5.2
199
38.6
13
8.92
4.00
29.31
5.61
18.4
24
May 30. . .
602.0
- 1.8
201
38.8
12
7.62
3.97
31.96
4.97
16.6
22
May 31*..
598.8
- 3.2
199
40.2
15
8.91
4.00
26.61
4.71
16.8
23
June 1*. .
603.8
+ 5.0
1 50 gm. salt also eaten on April 12 and 16, and May 2, 6, 10, 19, 23. and 29
CHRONOLOGY OF THE FASTING RESEARCH
45
Table 10. — Statistics of experiment of April 17 to May 1, 1922, steer D
Date
Body-weight
Chest-
girth
Water
Feed1
Excreta
Insen¬
sible
loss
Stall
temp.
Total
Change
Total
Temp.
Hay
Meal
Feces
Urine
1922
kg.
kg.
cm.
kg.
eC.
kg .
kg.
kg.
kg.
kg.
°C.
Apr. 10. . .
614.6
+ 0.8
208
31.4
12
8.96
3.00
21.62
4.49
15.4
22
Apr. 11.-. .
616.4
+ 1.8
208
29.6
12
8.82
3.00
22.29
4.54
11.6
13
Apr. 12. . .
619.4
+ 3.0
208
29.4
12
8.84
3.00
24.26
4.92
12.8
13
Apr. 13...
618.8
- 0.6
208
31.8
12
8.86
3.00
22.65
4.68
14.2
18
Apr. 14 . . .
621.0
+ 2.2
208
31.8
15
8.92
3.00
22.23
4.88
15.0
21
Apr. 15. . .
622.6
+ 1.6
208
31.8
15
8.94
3.00
22.34
4.75
13.2
17
Apr. 16. . .
626.0
+ 3.4
208
29.6
13
8.90
3.00
22.26
5.50
15.8
20
Apr. 17*..
624.0
210
32.4
15
0.00
0.00
19.06
5.71
12.4
20
Apr. 18*..
619.2
- 4.8
206
7.8
13
0.00
0.00
7.42
6.73
4.2
20
Apr. 19*. .
608.6
-10.6
206
8.4
14
0.00
0.00
5.47
6.98
5.2
20
Apr. 20*..
599.4
- 9.2
203
5.2
13
0.00
0.00
3.81
3.20
4.2
15
Apr. 21*. .
593.4
- 6.0
203
0.0
0.00
0.00
1.42
2.43
3.0
20
Apr. 22*. .
586.6
- 6.8
203
7.8
17
0.00
0.00
2.54
2.29
3.8
22
Apr. 23*..
585.8
- 0.8
203
0.0
0.00
0.00
1.81
1.57
3.6
22
Apr. 24*..
578.8
- 7.0
203
6.8
19
0.00
0.00
1.39
1.87
3.8
22
Apr. 25*. .
578.6
- 0.2
202
4.8
17
0.00
0.00
1.32
1.92
4.6
23
Apr. 26*..
575.6
- 3.0
202
8.4
18
0.00
0.00
1.25
7.65
3.4
20
Apr. 27*. .
571.8
- 3.8
203
0.0
0.00
0.00
1.33
2.32
3.2
22
Apr. 28*..
565.0
- 6.8
203
6.8
19
0.00
0.00
1.39
3.81
2.8
21
Apr. 29*..
563.8
- 1.2
201
4.4
19
0.00
0.00
1.08
5.68
4.2
21
Apr. 30*..
557.2
- 6.6
201
0.0
0.00
0.00
0.63
1.90
2.8
21
May 1*..
551.8
- 5.4
201
0.0
3.75
0.00
0.70
1.10
4.8
19
May 2 . . .
548.8
- 3.0
201
11.2
17
3.51
0.00
0.93
1.92
5.0
22
May 3 . . .
555.6
+ 6.8
201
20.6
17
5.52
0.00
3.18
3.98
5.4
19
May 4...
569.2
+13.6
203
12.2
14
5.51
0.00
7.33
4.22
4.4
14
May 5...
571.0
+ 1.8
201
10.6
17
6.34
0.00
10.45
2.34
5.8
19
May 6...
569.4
- 1.6
203
14.0
16
7.02
0.00
12.96
3.25
7.2
19
May 7...
567.0
- 2.4
202
24.8
17
8.92
0.00
14.19
3.00
6.6
18
May 8...
577.0
+ 10.0
203
19.0
15
0.00
0.00
16.86
2.53
5.6
18
May 9*..
571.0
- 6.0
202
6.4
16
8.85
4.00
13.33
3.07
9.8
21
May 10...
564.0
- 7.0
201
32.0
15
7.86
4.00
17.32
4.00
12.2
21
May 11.. .
574.4
+10.4
203
34.8
14
7.69
4.00
19.98
3.28
11.8
19
May 12. . .
585.8
+11.4
203
27.0
14
7.84
4.00
24.05
3.13
13.0
20
May 13. . .
584.4
— 1.4
203
35.0
21
7.78
4.00
23.09
3.51
13.6
19
May 14. . .
591.0
+ 6.6
203
31.8
15
8.10
4.00
24.58
4.43
15.2
20
May 15. . .
590.6
- 0.4
203
32.8
14
8.86
4.00
23.36
5.62
14.4
20
May 16. . .
592.8
+ 2.2
203
37.6
15
8.69
4.00
25.57
4.76
13.0
17
May 17. . .
599.8
+ 7.0
203
32.4
15
8.06
4.00
26.37
4.31
11.8
17
May 18. . .
601.8
+ 2.0
203
31.0
14
8.97
4.00
24.35
4.48
13.8
17
May 19 . . .
603.2
+ 1-4
203
35.8
15
8.48
4.00
25.23
5.83
14.2
20
May 20. . .
606.2
+ 3.0
200
33.2
14
8.71
4.00
26.16
5.31
14.0
22
May 21. . .
606.6
+ 0.4
206
33.8
15
8.64
4.00
26.35
4.92
18.8
24
May 22. . .
603.0
- 3.6
203
37.2
16
7.81
4.00
31.10
4.09
14.8
22
May 23. . .
602.0
- 1.0
206
35.0
15
8.89
4.00
29.23
4.70
14.0
20
May 24...
001.4
- 0.6
206
37.0
15
8.25
4.00
28.09
3.75
14.6
21
May 25. . .
604.2
+ 2.8
206
39.4
15
7.82
4.00
30.35
3.47
15.6
22
May 26. , .
606.0
+ 1.8
206
37.0
15
8.76
4.00
28.32
3.81
14.2
21
May 27...
609.4
+ 3.4
208
37.2
13
8.93
4.00
28.18
3.91
12.6
10
May 28.. .
614.8
+ 5.4
206
36.2
14
8.72
4.00
29.68
4.81
15.4
22
May 29. . .
613.8
- 1.0
206
36.0
15
7.68
4.00
28.31
5.78
16.6
24
May 30. . .
610.8
- 3.0
206
38.6
15
8.40
4.00
28.01
4.73
14.2
22
May 31*. .
614.8
+ 4.0
206
35.6
13
7.22
4.00
28.96
5.52
15.8
23
June 1*
611 4
Q A
1 50 gm. salt also eaten on May 2, 6, 10, 19, 23, and 29.
46
METABOLISM OF THE FASTING STEER
nation of the detailed records in Tables 9 and 10 shows that from the begin¬
ning of the fast on April 17 there was a steady, pronounced loss in weight
with both animals, which persisted throughout the entire fast. The water
intake also fell off noticeably, the animals occasionally refusing to drink at
all. The decrease in the daily weight of feces was fairly uniform. The
volume of urine fluctuated considerably, although the general average shows
a similar decrease. The insensible loss dropped noticeably after withholding
of feed, but with the resumption of feeding it gradually regained a high
level. The stall temperature remained reasonably constant throughout the
entire period from April 10 to June 1. The chest circumferences showed
characteristic decreases during the fasting period and a slow increase subse¬
quently, although on the first of June, at the end of the refeeding period,
the chest circumference of neither animal had returned to its original
magnitude.
Steer D recuperated much more slowly on the ration of hay only than
did steer C after this 14-day fast. During the first 7 days, when hay alone
was fed, he ate nearly 1 kg. less per day than did steer C and showed much
less inclination to eat. During the 23 days following, when both hay and
meal were fed, he ate less hay daily than did steer C, and although he
cleaned up the meal every day, he left the general impression that he was
much slower in regaining his normal vigor than steer C. Certainly he did
not gain as much during the month of recuperation after the 14-day fast
as did steer C, which made remarkable progress in so short a time. It is
evident, therefore, that the recuperative capacity of steer D was somewhat
below that of steer C.
Both steers had regained their original prefasting weight and vigor by
June 1, and both were in excellent condition for the fourth fast. Judged on
the basis of general appearance and so-called “handling,” they were both
in a higher state of flesh than they had been at any previous time since they
were purchased. Steer C had made an especially rapid improvement during
the month of refeeding. He took on flesh rapidly and carried a good cover¬
ing of flesh. In live weight he had almost overtaken steer D, which had
weighed 16 kg. more at the beginning of the fast. Steer D also had taken
on considerable flesh and looked in excellent condition, but his total increase
in weight was not so large as that of steer C.
During the lasti 6 days of this fast, records were kept of the time spent
standing and lying during each 24-hour period.
General Observations During the 14-Day Fast
The first feed withheld was the afternoon feed on April 17. Both animals
were placed in the respiration chamber on this date, steer C in the morning
and steer D in the afternoon, but since both had been fed about 6h 30m a. m.,
the measurements do not represent standard metabolism. At feeding-time
(about 4 p. m.) on April 17, steer D was very noisy and restless, but steer C
was somewhat less active.
On the morning of April 18, at approximately 5h 30m a. m., about 50 grams
of the urine of steer C were lost. Both animals were much quieter on the
morning of April 18, steer D lying down much of the time. On April 18
steer C was in the respiration chamber from shortly after 9 a. m. until
CHRONOLOGY OF THE FASTING RESEARCH
47
12b 25m p. m. He was weighed and watered as usual at 2 p. m. Steer D was
studied in the respiration chamber on the afternoon of April 18.
During the afternoon of April 18, steer C was very restless in the stall,
continually lying down and rising. When lying, he kicked and lowed
spasmodically. These symptoms (supposedly of colic) started shortly after
he was watered at 2 p. m. and continued until 5h 45m p. m., when he lay
down and became quiet for the rest of the evening. The continuous effort
of rising and lying down, together with the apparent colic, seemed to weaken
him somewhat, as he was very relaxed during the rest of the night.
About 4 a. m. on April 19, steer C urinated while lying down. This was
the first time in our experience that an animal had urinated while lying, and
it suggested that the steer felt too weak to rise. Some urine was unavoid¬
ably lost, as a consequence. The rectal temperature during this period of
colic was normal, but the volume of urine passed was almost double the
normal amount. On April 19, both animals behaved normally, although
steer C still showed signs of fatigue, especially after coming out of the
respiration chamber, when he lay down immediately and remained in this
position practically all the afternoon.
Both steers were remarkably quiet and inactive up to the third day of
fasting, April 20, except for the first afternoon, April 17, and to a less extent
during the second day, April 18. They had not shown any particularly
pronounced anxiety for feed, as indicated by restlessness or lowing, and
certainly showed no distress. On the sixth day of fasting, April 23, they
were still doing well, with no signs of distress or other disturbance.
The feces of both animals were still fairly firm on the fourth day, April 21,
but the amounts were becoming markedly smaller. On the seventh day,
April 24, the feces of steer C were somewhat softer. During the evening,
between 6 p. m. and 8h 30m p. m., he passed from 15 to 20 grams of material
rather solid in form, reddish in appearance, and resembling tissue, slightly
bloody, and mixed with mucus. The assistant on watch reported that he
strained considerably in passing this. The material was extremely offensive
in odor. Steer D behaved as usual.
On the eighth day, April 25, the feces of steer C were very loose, but
there was no change in rectal temperature and, so far as could be seen from
general observation, he was very bright and acted as usual. No change was
noted with steer D.
On the ninth day, April 26, steer C behaved as usual, being quiet and
alert. The feces of steer D were becoming loose or soft at this time, while
those of steer C wrere becoming firm and pilular again, although they were
not exceedingly dry. Both animals still rose from the lying position with
apparent ease, showing no signs of weakness or of having to exert particular
effort in rising. In lying down, however, they relaxed more suddenly after
they wrere nearly down than they did when on feed. This was noticed with
steer C, especially after his attack of colic on the second day, from which
he seemed otherwise to have entirely recovered. This relaxation on the
part of the steers after they were nearly down was probably in part due to
the narrowness of the stalls, which gave them less opportunity to spread
their legs.
48
METABOLISM OF THE FASTING STEER
During the morning of the tenth day, April 27, steer D urinated for the
first time while lying down, and approximately 100 grams of urine were
spilled.
Both animals acted somewhat stiff on April 28, and hunched their backs
somewhat when led from the stalls to the respiration chamber. Their gait
was slightly unsteady, perhaps due to weakness. The consistency of the
feces varied with different defecations, being sometimes very soft. Those
of steer C were soft when voided in the chamber, a fact which suggests a
possible influence of the exertion of prolonged standing.
There was no unusual behavior of the steers on April 29. On the evening
of April 29, i. e., after 12 days of fasting, tests of the acidity of the urine
were begun, on the supposition that the steers had reached a carnivorous
condition and were living on their own body-tissue, and that their urine
should consequently give an acid reaction to litmus paper rather than the
characteristic alkaline reaction of the urine of herbivora.
Both steers were in the respiration chamber on the morning of May 1,
the fourteenth day of the fast, and at 2 p. m. the fast ended. Steer C was
weighed, fed 1,810 grams of hay, and put into the chamber again immedi¬
ately after eating. The respiration experiment was continued from 4 p. m.
until approximately 10 p. m., the purpose being to note the change in the
respiratory quotient and to measure the rise in the carbon-dioxide production
which follows the ingestion of food.
Summarized Details of Other Fasts of Steers C and D
Steers C and D were subjected to their fourth fast on June 1-7, 1922, and
at 10 a. m. on June 10, 1922, they were turned out to pasture. Here they
remained until November 6, 1922, when a fasting experiment after pasture
feeding was made. They were brought to the laboratory at 8 a. m., Novem¬
ber 6, 1922, after having had their last feed on pasture that morning, and
the fasting period began at once. Both steers were in better condition of
flesh at the beginning of this fast than they had been at any time since they
were purchased. Steer C was especially well fleshed; in fact, he weighed
approximately 100 kg. more than at the start of any previous fast. Steer D
weighed about 75 kg. more than he had prior to the previous fasts. This
excess in weight, however, probably did not entirely represent organized
body-tissue, but in part liquid mass of fill, due to the green feed.
Between January 3 and June 5, 1923, steers C and D were subjected to a
series of intermittent fasts of from 48 to 72 hours in length. During the
intervals between these short fasts until March 28 a constant daily ration
of 9 kg. of hay and 2 kg. of meal was given. During this time steer C was
subjected to 11 and steer D to 10 fasts. Between March 28 and April 25
the daily ration for both steers consisted of 9 kg. of hay only. After
April 25 the ration was reduced to 4.5 kg. of hay until June 5 for steer C
and June 7 for steer D, when the ration was again increased to 9 kg. of hay,
which level was maintained until June 22. A special feature of these short
fasts was a study of variations in environmental temperature, with a view
to determining if extremes in temperature would alter the metabolism
materially.
CHRONOLOGY OF THE FASTING RESEARCH
49
Both steers were turned out to pasture at 12h 20m p. m., June 23, 1923. On
June 22, before going to pasture, steer C weighed 666.4 kg. and steer D
weighed 637.4 kg. The animals were brought back to the barn again on
October 31, 1923, and placed in a small pasture adjoining it for 4 days.
Between 3 and 4 p. m., November 4, 1923, they were placed in stalls in this
barn, without feed, preparatory to respiration experiments beginning on the
morning of November 5. At 8 a. m., November 5, they were brought to the
metabolism laboratory and weighed, steer C weighing at this time 735.6 kg.
and steer D 717.2 kg. They were weighed again at 2 p. m., November 5,
and the collections of feces and urine for the 5-day fasting period were
begun at this time.
After their fast in November 1923, steers C and D were again removed
from the metabolism stalls to the barn, where each was fed regularly 9 kg.
of hay per day until December 21. On this date the daily ration for each
animal was reduced to 4.5 kg. (i. e., a 50 per cent maintenance ration) and
continued at this level through the morning feed of March 3, 1924, when
the steers were subjected to a 10-day fast. This reduction in feed was made
for the specific purpose of placing these animals upon the same submain¬
tenance ration as was given to steers A and B in the earlier research, with
the idea of studying the effect of a fast following a reasonably prolonged
period of undernutrition. On February 25, 1924, steers C and D were
moved from the bam to the metabolism stalls, where the collection and
aliquoting of feces could again be made. This allowed one complete week
before the fasting began in which they could become adjusted to the differ¬
ence in temperature and the greater restriction of the metabolism stalls. The
urine and feces were, as usual, collected in 24-hour periods. The daily
periods were from 2 p. m. to 2 p. m. until March 3. March 3^ was only
a 17-hour day, when the feces and urine were collected from 2 p. m., March
3, to 7 a. m., March 4. On March 4 and thereafter throughout this fast the
animals were weighed and watered at 7 a. m. daily, so that two separate
collections of feces and urine, representing separate day and night periods,
could be made.
The study of the respiratory exchange and the energy transformations in
the fasts between November 1921 and March 1924 was based upon a series
of relatively short respiration experiments. Many of the experiments on
ruminants by earlier investigators have been made in respiration chambers
or calorimeters in which the experimental periods were 24 hours in length.
Consequently, with steers C and D an experiment was made in April and
May 1924, respectively, in which each animal remained inside the respira¬
tion chamber for 3 days continuously. Unweighed amounts of drinking-
water were allowed, as desired, a tub being placed in the chamber for this
purpose and water being introduced through a short piece of rubber tubing
connecting the tub with the outside of the chamber. No attempt was made
to determine the amount of urine and feces passed. The time was too short
to bring these animals back to first-class condition for these fasts. They
had come in from pasture the preceding November, full of green grass and
in excellent condition. They were then given a one-half maintenance ration
for the better part of the winter, after which they fasted for 10 days. At
50
METABOLISM OF THE FASTING STEER
the end of this fast, when each animal had lost on the average not far from
40 kg., they were each fed 9 kg. of hay daily, steer C until April 22, when
he fasted for 4 days, and steer D until May 13, when he also fasted for
4 days. At the beginning of the 10-day fast in March, which followed the
long period of submaintenance feeding, steer C weighed on the average
about 635 kg. and steer D 622 kg. At the beginning of his 3-day respiration
experiment on April 23, 1924, steer C weighed 669.6 kg., and at the begin¬
ning of his 3-day respiration experiment on May 14 steer D weighed 664.6
kg., i. e., each weighed from 35 to 40 kg. more than at the end of the sub¬
maintenance period on March 3. It is highly improbable that with but
9 kg. of hay per day in a period of 5 or 8 weeks the entire loss during 10
days of fasting could have been made up by each animal. It is more likely
that this increase in weight represented largely increase in fill or in the
contents of the alimentary tract, due to doubling the quantity of the ration
and thus automatically the water intake.
The chest circumference of steer C at the beginning of the March fast
was 208 cm., and it was the same on April 22, prior to the 4-day fast. The
chest circumference of steer D measured 212 cm. before the March fast and
210 cm. before the May fast. This measure of the condition of flesh of
steer C would indicate complete recuperation back to the point of beginning
the 10-day fast in March. This would not be entirely true of steer D, whose
chest circumference was actually 2 cm. less (indicating less flesh), although
his weight had increased 40 kg. Under these circumstances it seems prob¬
able that steers C and D were in a condition more nearly approximating
undernutrition than a normal condition.
No records of insensible loss were kept during the feeding period follow¬
ing the fast in March 1924, or during the fasts in April and May 1924.
Steer C was in the respiration chamber continuously from 7h45ma. m.,
April 23, 1924, to 7h 45m a. m., April 26, 1924, and steer D was in the
chamber continuously from 7h 36m a. m., May 14, 1924, to 7h 36m a. m., May
17, 1924, each animal having been without food for 24 hours before entering
the chamber. While in the chamber the animals were allowed to lie or stand
at will. Careful records were obtained with regard to the amount of time
spent standing and lying. These records have an important bearing upon
the interpretation of the measurements of the metabolism during the indi¬
vidual experimental periods, which were of 8 hours’ duration at this time
instead of the usual 30 minutes. As a general index of the total 24-hour
metabolism of animals under conditions of stall confinement, these 8-hour
periods present, theoretically at least, a much more perfect picture than do
short half-hour periods.
No records of feed consumed after these 4-day fasts were kept, and on
May 19, 1924, the steers were turned out to pasture.
In connection with an experiment to determine the insensible loss under
extremely varying conditions of feeding, both steers again fasted for 2 days
each, on November 11 and 12, 1924. This was the last fast conducted with
these steers. The steers had been on pasture since May 19, 1924, and had
been brought off pasture on the morning of November 11, 1924.
CHRONOLOGY OF THE FASTING RESEARCH
51
OBSERVATIONS ON IMMATURE STEERS E AND F
In addition to the study of the effect of fasting upon adult steers on vari¬
ous nutritive planes, it seemed advisable to study the influence of fasting
upon young, growing animals, which presumably would react to the lack
of food more acutely than adult animals. To make the experiment still
more critical, it was proposed to place these younger animals upon a dis¬
tinctly submaintenance ration, so that they would begin their fast in a con¬
dition of undernutrition. This preliminary preparation, therefore, became
part of a subsidiary study of the effect of undernutrition upon young steers.
Two young, purebred, Shorthorn steer calves, E and F, were purchased in
the fall of 1923. Both were born on November 28, 1922. They had been
kept in an ordinary lot, where they ran loose with a dozen other calves. On
October 13, 1923, the day they were delivered at the laboratory in Durham,
steer E weighed 288.0 kg. and steer F weighed 310.8 kg. Previous to their
arrival they had been fed a ration of hay and silage, with a small amount
of grain, which provided for ordinary growth. They were consequently in
a good, vigorous, and thrifty condition and in a fair state of flesh, but
carried no great amount of fat.
The 24-hour periods for collection of data began and ended at 2 p. m. in
the case of these steers, for all dates from the beginning of the experimental
season in November 1923, through April 1924. The 24-hour periods in the
fall and winter of 1924-25, however, began and ended at 4h 30m p. m.
When steers E and F arrived at Durham, they were placed at first in
temporary quarters, but on November 14, 1923, they were taken to the
metabolism stalls. From this date until December 17, 1923, they received
an approximately maintenance ration, consisting of 5 kg. of hay and 0.68
kg. of meal daily. From December 17, 1923, to February 12, 1924, they
were fed a submaintenance ration of 2.5 kg. of hay and 0.30 kg. of meal, the
amount of meal being reduced to 0.10 kg. on January 28. On February 12,
1924, they began a 5-day and 6-day fasting experiment, respectively, under
the usual conditions prevailing in the previous fasts, except that steers E and
F started their fast on a submaintenance plane of nutrition. Prior to this
fast the “standard metabolism” (see p. 228) of both animals was studied at
intervals of approximately one week, both upon the maintenance and sub-
maintenance levels of nutrition. 'Special consideration will be given to
these data subsequently. (See pp. 228 to 234.)
In addition to the 3-day respiration experiments during the April and
May fasts of steers C and D, steers E and F were also subjected to a con¬
tinuous 3-day respiration experiment while fasting. On February 29, 1924,
following a short period of readjustment after the February fast, both
animals were placed on a daily ration of 5 kg. of hay and 0.91 kg. of meal.
This feed-level was continued until March 31 with steer F and until April 8
with steer E, when each animal was subjected to a 4-day fast. Daily
records of live weights, weights of urine and feces, and records of the
insensible loss were not obtained previous to and during these fasts, as the
main object was a study of the respiratory exchange.
At the beginning of these particular fasts the body-weights of steers E
and F were not far from those when they were first received at the labora¬
tory, although they were nearly 5 months older and would normally have
52
METABOLISM OF THE FASTING STEER
gained in weight. Thus, the body-weight of steer E was 280 kg. on April 9,
1924, as compared with an initial weight on November 19, 1923, of 266.2 kg.,
and that of steer F was 295.2 kg. on April 1, 1924, as compared with an
initial weight of 291 kg. The body-weights in April, therefore, represent a
thinner state, more nearly approaching the condition of undemutrition.
The steers had been fed more hay and meal after the fast in February 1924,
however, than they had received during November and December 1923,
that is, 5 kg. of hay and 0.91 kg. of meal per day as compared with the
earlier so-called “maintenance” ration of 5 kg. of hay and 0.68 kg. of meal.
That they had fully made up all their losses during the period of under-
nutrition, and particularly during the 5-day fast in February, and at the
same time had made up for growth is highly improbable. These animals
were therefore undoubtedly in a distinctly undernourished state in April.
Their chest circumferences in April 1924 were essentially the same as those
at the time of their purchase, but notably greater than during the period of
undemutrition. The estimate of the nutritive plane of these animals is
complicated by the fact that they were growing, but the general conclusion
is that although not in a good state of flesh, they were not so thin in April
as in February, at the beginning of their longer fasts.
At the end of his fast, on April 12, 1924, steer E weighed 260.8 kg., having
lost 19.2 kg. in the 4 days of fasting. Steer F weighed 271.8 kg. at the end
of his fast on April 4, 1924, having lost 23.4 kg. The chest circumference
of steer E was 145 cm. prior to fasting and 142 cm. for several days follow¬
ing the fast, but by April 18 it was again 145 cm. The chest circumference
of steer F was 150 cm. before the fast and 147 cm. after the fast, but was
again 150 cm. on April 18.
Between December 1924 and May 1925 a series of continuous 4-day res¬
piration experiments were made with steers E and F, with the object of
studying the method of estimating the fasting metabolism from the effect of
quantitative variation of the same feed. These respiration experiments con¬
sisted of 2 days when the animal received feed, followed by 2 days of fasting.
For at least 2 weeks prior to each experiment and during the first 2 days in
the respiration chamber the feed-level was held constant, either at main¬
tenance or submaintenance. The effect of high and low environmental tem¬
peratures and the relative difference in. the effect of timothy and alfalfa
hay were also studied. During the two weeks preceding each 4-day respira¬
tion experiment careful records were kept daily of the measurements neces¬
sary for the computation of the insensible loss. Chemical analyses of the
urine and feces were not made, however. While the steer was in the chamber
the feces were collected only at the end of the 4 days, as it seemed more
important not to break the air-seal of the respiration chamber than to have
a daily record of the weights of feces. It was possible in most instances,
however, to secure the daily weights of urine voided, and samples were taken
for nitrogen determinations.
RECORDS OF LAST INDIVIDUAL FEED PRIOR TO EACH FAST
The amount of the last individual feed and the hour at which it was given
prior to each fast are recorded in Table 11. The first feed given to the
steers following the fasts was not the same in every case. Since the interest
CHRONOLOGY OF THE FASTING RESEARCH
53
lies, however, only in those cases where a respiration experiment was made
immediately after the first refeed, the details regarding the first feed after
each fast are not tabulated here, but will be discussed subsequently in con¬
nection with the respiration experiments. (See pp. 222 and 223.)
Table 11. — Amounts and times of last feeds prior to fasts
Steer
Date
Hay1
Meal
Time
C and D . . .
Dec. 6, 1921 .
kg.
ca. 4.5
kg.
1.36
6 a. m.
C and D . . .
Jan. 4, 1922 .
ca. 4.0
3.00
6 a. m.
C .
Apr. 17, 1922 .
2.5
1.50
6h30m a. m.
D .
Apr. 17j 1922 .
4.4
1.50
6 30 a. m.
C .
June 1, 1922 .
4.5
2.00
10 30 a. m.
D .
June 1, 1922 .
2.7
2.00
7 45 a. m.
C and D . . .
Nov. 6, 1922 .
Off p
asture
8 a. m.
C and D . . .
Jan. 3 to Mar. 20, 1923 .
4.5
1.00
8 a. m.
C .
Mar. 22, 1923 .
3.5
1.00
8 a. m.
C and D . . .
Nov. 4, 1923 .
Off p
asture
3 to 4 p. m.
C, D, E, F .
Feb. 12 to Apr. 8, 1924 .
ca. 2.5
0.00
7 to 8 a. m.
C .
Apr. 22, 1924 .
4.5
0.00
8 a. m.
D .
May 13, 1924 .
4.5
0.00
8 a. m.
C and D . . .
Nov. 11, 1924 .
Off p
asture
4h30m p. m.
E and F . . .
Dec. 14 and 19, 1924 .
3.5
0.00
8 40 a. m.
E and F . . .
Jan. 14 to Feb. 13, 1925 .
3.5
0.00
5 p. m.
E and F . . .
Mar. 1 to Apr. 22, 1925 .
3.5
0.00
ca. 8b45m a. m.
E and F . . .
May 5 and 12, 1925 .
3.5
0.00
5 p. m.
1 Timothy hay was fed to steers C and D on all dates and to steers E and F until March 1925.
On Mar. 6, 1925, at 4h30m p. m. and thereafter steer E was fed alfalfa hay; on Mar. 9, 1925, at
4h30m p. m. and thereafter steer F was also fed alfalfa hay.
DISCUSSION OF RESULTS
BODY-WEIGHT
No one factor is of greater concern in practical and experimental nutrition
than is a true measure of the loss or gain of organized body -tissue resulting
from any particular level of feeding. Since there is seemingly no better
measure of these changes than live body-weight, it has been almost uni¬
versally adopted for this purpose. On a priori grounds, one can reasonably
assume that in fasting, with no food intake, there must be a continuous
draft upon the body-tissue. The magnitude of this draft, however, is not
strictly indicated by any changes which take place in live body-weight, for
even while this draft may be going on, the live weight may actually increase.
In most fasting experiments, drinking-water is permitted, which of course
helps to increase the live weight temporarily. On the other hand, there are
factors, such as the excretion of urine and feces, which decrease the live
body-weight, but which do not quantitatively represent loss of tissue. It is
therefore extremely complicated to determine the true loss of body-tissue
which takes place as a result of the fasting per se. Without a careful
analysis of the relative influence of these various factors, any changes in
body-weight can present only a most inadequate picture of true losses of
body-tissue. The daily fluctuations in live weight due to these extraneous
factors may be exceedingly large; in fact, they may be many times greater
than any possible daily changes (particularly increases) which could take
place in the form of body-tissue.
The gross fluctuations in the live weights of cattle from day to day, even
with constant intake of food and water, have already been discussed in
great detail.® These changes in live weight, which are at times very large,
can be definitely traced in the majority of instances to variations in the
fill or ballast of ruminants and particularly to variations in the water-
content of the alimentary tract and of the bladder. From the experimental
standpoint, it would be preferable if the caecum and the bladder could be
emptied just prior to weighing at the end of any given experimental period,
but obviously this is impossible in the case of ruminants. Yet if both of
these organs are emptied just after the weighing at the end of the 24-hour
period, these voidings may by chance be credited to either one or the other
of two different days and the live weight will vary accordingly. The
irregularity in the quantity and in the time of expulsion of both feces and
urine is therefore an important factor in these fluctuations in live weight.
The results obtained during the undernutrition periods in this present
research bear out the earlier results with ruminants published from the
Nutrition Laboratory, which showed that during undernutrition there are
pronounced variations in the amount of the intestinal ballast, and particu¬
larly that when there is a transition from a low to a higher nutritive plane,
or vice versa, the change is relatively enormous. The variations which take
place in the elimination of feces under conditions of fasting were therefore
studied with special care in these fasts, the amount of each defecation and
“Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, pp. 80 et seq.
54
BODY-WEIGHT
55
of each urination being recorded, as well as the hour when they were voided.
Such records give no direct measure of the actual mass of undigested mate¬
rial in the intestinal tract at any time, but are essential to an intelligent
study of those changes in body-weight which represent organized body -tissue
apart from those due to changes in fill.
The body-weights of our steers were determined on scales sensitive to
approximately 0.2 kg. Since the primary essential in weighing a nervous
animal is quiet control, particular care was taken to have the animal
standing still while the sliding weight on the scale-beam was being adjusted
to a balance. The desirability of always having the animals weighed by
the same person at the same hour of the day and as nearly as possible under
the same conditions can hardly be over estimated. In fact, the person who
held the animal also stood on the scale and was weighed with the steer, the
scale having been previously balanced with the attendant’s weight recorded
on the upper arm of the scale beam. Thus any pull on the halter would not
disturb a correct balance. The body-weights were therefore recorded with
extreme care, every precaution being taken to secure the highest degree of
accuracy in the measurements and in the time records, in order to make the
weights of special value in the computations of the gains or losses per 24
hours and particularly in the calculation of the insensible loss.
Lengths of Fasts and Nature of Feed-levels Preceding Them
Of the 4 animals used in this investigation, steers C and D were each sub¬
jected to 7 fasts of from 5 to 14 days, one fast of 4 days, one of 3 days, and
11 and 10 fasts, respectively, of 2 days each. Steers E and F were each
subjected to one fast of 5 and 6 days, respectively, to one fast of 4 days,
and to 7 and 6 fasts, respectively, which were between 2 and 3 days in
length. These fasts followed different levels of nutrition. All the fasts of
steers C and D from December 1921 to June 1922 came after a preliminary
feeding on hay and meal, the feed-level ranging from approximate main¬
tenance to moderate supermaintenance. The fasts of November 1922 and
November 1923 with the same steers took place after they had been on
pasture for 4 or more months, and the fasts in March 1924 followed 2
months of submaintenance feeding. The short fasts of steers C and D,
ranging from 2 to 4 days, followed feed-levels representing approximate
maintenance. The long fasts of steers E and F in February 1924, like those
of steers C and D in March 1924, followed submaintenance feeding, and
their 4-day fasts in April 1924 followed maintenance feeding. The short
2-day and 3-day fasts of steers E and F in 1925, however, were not planned
for a study of body-weight changes.
The steers were kept in metabolism stalls during all fasts and, with few
exceptions, also during the preliminary feeding-periods before the fasts, so
that it was possible to secure daily records of the live weight, the weights
of water consumed, and the weights of urine and feces voided. The result¬
ing mass of data has been given in detail for the fasts of steers C and D in
April 1922 (see Tables 9 and 10, pp. 44 and 45), but the data for the other
fasts will be found in the tables in this chapter and in the subsequent
chapters of this monograph.
56
METABOLISM OF THE FASTING STEER
Daily Variations in Body-weight During Fasting
The daily variations in body-weight have been tabulated for each fast
and for the 3 food days directly preceding. For the fasts of 5 or more days,
which followed different feed-levels, the data are given in Table 12, and for
the fasts of 2 and 3 days, following maintenance feeding, the data are given
in Table 13. Reference should also be made to Tables 17 to 20 and Table
27, pages 72, 76, 78, 83, and 100, in connection with the following discussion.
Influence of Long Fasts at Different Levels of Nutrition
Considering, first, the fasts of 5 to 14 days, we see from Table 12 that on
the three food days preceding each fast fluctuations in live weight from day
to day appear in all instances, as would be expected, but since they include
both gains and losses which are practically compensating, the tendency to
variation around a uniform live weight is apparent. During fasting, the
general picture of daily variations in live weight shows a clear-cut contrast
to the conditions previous to fasting. The changes in live weight are
equally large for the first three or four days, but with few exceptions they
represent only losses. After the fourth day the losses continue, but they
tend to become materially less, although they still remain somewhat
irregular.
A close examination of the losses during different fasts shows the impor¬
tant influence which the prefasting feed-level exerts on losses in weight for
the first few days. The first four long fasts of steers C and D (see Table 12)
followed relatively similar feed-levels, consisting of hay and meal and
ranging in quantity from maintenance to slightly supermaintenance. Dur¬
ing all four of these fasts the losses in live weight on the first day are
similar, but relatively small. The apparently wide discrepancy between
the first fast and the three following is directly accounted for by differences
in water intake at the beginning of the first 24-hour period. In other wrords,
in the first fast both steers drank approximately 18 kg. of water at the
beginning of the first 24-hour period without food, and before each of the
other three fasts they took approximately double that amount, although
there was no material difference in the total weight of urine and feces
voided on these days. Excretion of this water in the urine and feces during
the same 24-hour period, therefore, furnishes the remaining necessary evi¬
dence for the cause of these fluctuations in live weight.
In the fifth and sixth fasts, which followed pasture feeding (an entirely
different feed-level), the relative losses during the first 24-hour period are
at least five times as large as those during the first day of fasting after dry
feed. In the sixth fast (i. e., in November 1923) the losses were obtained
only for the last 5% hours of the first 24-hour period, but even for this
length of time the decrease in weight is approximately 11 kg., suggesting
that the loss for the total 24 hours must have been immense, as was the case
in the fifth fast in November 1922.
In the seventh fast with steers C and D, which followed a submaintenance
feed-level of 2 months, there was practically no loss in weight during the
first 17 hours. This fact suggests that when the fast began the intestinal
fill must have been considerably below the amount normally present during
12.— Daily changes in body-weight before and during fasts of 5 to 1 4 days
BODY-WEIGHT
57
at the end of the first fasting day.
58
METABOLISM OF THE FASTING STEER
maintenance feeding. The losses noted during the submaintenance fasts of
steers E and F, although not quantitatively comparable with the losses of
steers C and D, because of inequality in the size and age of the animals,
are surprisingly high on the first day, but the losses on the following days
are small, characteristic of submaintenance feeding.
The influence of water intake on the irregularity of the loss in live weight
becomes strikingly manifest between the first and the second day of fasting.
In the fasts of 5 to 14 days, almost without exception the animals would
refuse water at the beginning of the second day, after having fasted for 24
hours. Hence, in most instances, there was no intake whatsoever to offset
the outgo, and the losses are relatively large. As further proof of this point,
those instances when the animal actually did drink any material quantity
of water show the exception to a large decrease in weight. Striking exam¬
ples are the third fast of steer C and the fifth fast of steer D. On the other
hand, in the short 2-day fasts, which will be discussed in detail later (see
Table 13, p. 60), when these steers refused to drink at the beginning of the
first day, but drank at the beginning of the second day, the magnitude of
live-weight losses was reversed. In other words, it is purely a differential
balance produced by water intake on the first and second days, which indi¬
cates a larger loss in weight on the second day than on the first, or vice
versa. The relationships between loss in weight and water intake are of
course not absolutely proportional, as they are modified somewhat by varia¬
tions in the amount of urine and feces voided. The variations in urine and
feces, however, are not by themselves of sufficient magnitude to account for
a material difference in loss of weight.
The conditions pertaining to the fasts off pasture are not strictly com¬
parable with the conditions of the fasts following dry feed just mentioned,
for the reason that animals apparently lose the semi-liquid fill of grass at
a much more rapid rate than they do a fill from hay and meal. The tre¬
mendous losses during the first day of these fasts off pasture have already
been pointed out. During the second day of fasting off grass the loss still
tends to continue at nearly the same rate when the animal does not drink
water, and in the only case where the loss is very low (4.4 kg.) the cause
can immediately be laid to the fact that this is the only instance where the
animal drank water at the beginning of that day. In the case of the fast
off pasture where the loss is exceptionally large even on the second day
(37.4 kg. with steer D), the cause is immediately traceable to an excep¬
tionally large amount of urine and feces coincident with no water intake
at the beginning of the 24-hour period.
On the third day the effect of the previous feed-level becomes less mani¬
fest, and the weight loss of both steers appears to approach a relatively more
stable condition. Even the maximum loss of 18.2 kg. with steer C on the
third day of the fast in November 1923 is only slightly over half as large
as the probable loss on the second day of the same fast. The loss shows a
still further decline on the fourth day, and it is at this point that steers C
and D show the greatest individual difference. For the first four days the
live-weight losses of steer C were in general greater than those of steer D,
and on the fourth day his average loss for the 7 fasts was more than twice
BODY-WEIGHT
59
that of steer D. On the other hand, steer D had consistently taken much
larger amounts of water and a particularly large amount on the fourth day.
After the fourth day the rate of the daily loss of both animals appears to
become similar, regardless of the prefasting feed-level or of the individual
animal.
The average daily loss of steers C and D from the fifth day on to the
fourteenth is, respectively, 3.9 and 3.7 kg. The close agreement between
these average losses after the fifth day and the insensible perspiration dur¬
ing the same period (see Table 17, p. 72) suggests that after the fifth day
the loss in weight is more closely representative of the loss in body-tissue,
i. e., muscle and fat. If the outgo of visible excreta were always propor¬
tional to the intake of food and water during the same 24-hour period, then
any loss or gain in weight during this time could be accepted as a reasonably
close measure of loss or gain in body-tissue. Under conditions, however,
where the intake (water only) from one day to another may vary between
0 and 50 kg. and the visible outgo may remain fairly uniform, the differ¬
ential between these two extraneous factors entirely conceals any change in
the body-tissue. In other words, the live weights on any given day are not
specifically indicative of a change in body-tissue unless due allowance is
made for the balance between the intake and outgo of visible matter.
In the earlier literature there are no data with which our results may be
compared, except the experiments of Grouven.a One of his oxen, which
weighed 522 kg., fasted for 8 days. The loss in weight from day to day was,
as with our animals, rather large. Considerable irregularity was noted in
the loss in weight at the end of the fast, an irregularity which was, how¬
ever, in most instances easily accounted for by differences in water intake
or in the excretion of urine and feces. With another ox, weighing at the
start 420 kg., the losses in weight were more regular than with the larger
animal. Considerable differences were noted in the amount of water con¬
sumed by the smaller ox, and yet he drank water every day, whereas the
larger ox refused water on three days. The volume of urine with the
smaller ox remained singularly constant throughout the entire fast. The
amount of feces was large on the first day, but there was a rapid drop on
the second day. Since, as pointed out by Grouven in his discussion of the
nature of the intestinal ballast, the previous rationing plays such a role in
the changes in live weight during fasting, it is difficult to draw any strict
comparison between the data secured with our animals and with those of
Grouven.
Recently, Forbes, Fries and Kriss6 have published the body-weights of
some fasting cows, which indicate that there was in general a loss in body-
weight as the fast progressed, with occasional gains, due in large part to
the amount of water consumed. The maximum loss was 28.9 kg. with cow
887 III, which fasted for 9 days. Cow 874 III, which weighed 100 kg. more,
lost 25.5 kg. in 9 days.
° Grouven, Physiologisch-chemische Fiitteningsversuche. Zweiter Bericht ilber die Arbeiten
der agrikulturchemischen Versuchsstation zu Salzmunde, Berlin, 1864, pp. 147 et seq. (See, also,
p. 15 of this monograph.)
*Forbes, Fries, and Kriss, Journ. Dairy Science, 1926, 9, p. 18.
60
METABOLISM OF THE FASTING STEER
Influence of Short Fasts at a Maintenance Level of Nutrition
In view of the diversity found in the losses in weight of these animals
under different conditions of fasting, i. e., after pasture, after maintenance
feeding, and after submaintenance feeding, it is of importance to note what
would be the actual body-loss in a series of fasts where the feeding con¬
ditions prior to fasting would be practically identical throughout the entire
series. In connection with a series of short fasting experiments made pri-
Table 13. — Daily changes in body-weight on feed and during short fasts at a maintenance level
of nutrition
Steer and dates of
fasts (1923)
Initial
body-
weight
Final
body-
weight
Changes in weight on days
before fast
Changes in weight
on fasting days
Total
loss in
body-
weight
3
2
1
1
2
Steer C
kg.
kg.
kg.
kg.
kg.
kg.
kg.
kg.
Jan.
3 to
6. . .
689.8
658.8
—
4.0
+
4
0
—
5
4
-24
0
>- 2
8
31.0
Jan.
15
17. . .
686.4
654.2
—
6.6
+
4
6
—
8
2
-29
6
- 2
6
32.2
Jan.
21
23...
692.8
661.4
+ 12.6
+
2
2
—
4
6
-29
0
- 2
4
31.4
Jan.
28
30. . .
701.2
670.6
+ 16.6
—
6
8
4*
1
2
-26
6
- 4
0
30.6
Feb.
5
7. . .
700.2
670.4
—
5.6
—
0
2
+
3
0
-25
2
- 4
6
29.8
Feb.
11
13. . .
695.4
667.0
+ 10.2
+
5
4
—
5
8
-25
0
- 3
4
28.4
Feb.
18
20. . .
696.8
667.2
—
0.4
—
2
2
+
3
2
-25
4
- 4
2
29.6
Mar.
1
3. . .
700.0
670.2
—
4.0
+
4
8
—
2
0
-26
8
- 3
0
29.8
Mar.
8
10. . .
702.0
673.8
+
1.4
—
1
8
+
1
2
-27
0
- 1
2
28.2
Mar.
15
17. . .
703.8
674.0
+
1.4
—
6
0
+
0
8
-27
0
- 2
8
29.8
Mar.
22
24. . .
679.0
644.2
—
1.4
—
5
4
—
6
0
-30
8
- 4
0
34.8
Steer D
*
Jan.
9 to
12. . .
695.0
662.6
+
2.8
2 — 22
8
+ 19
2
-26
0
»- 2
2
32.4
Jan.
17
19. . .
695.0
659.4
—
0.4
—
9
4
+
2
2
-29
2
- 6
4
35.6
Jan.
25
27. ..
694.4
661.2
+
7.8
—
9
8
+
5
4
-27
0
- 6
2
33.2
Feb.
1
3. . .
686.4
649.6
—
5.4
—
5
0
+
2
8
-35
0
- 1
8
36.8
Feb.
8
10. . .
685.2
658.4
±
0.0
—
7
8
—
5
6
-24
8
— 2
0
26.8
Feb.
14
16. . .
701.8
664.6
+ 15.0
+
0
8
—
3
4
-26
0
-ii
2
37.2
Feb.
22
24. . .
701.0
663.6
—
2.4
—
5
6
+
9
4
-27
4
-10
0
37.4
Mar.
5
7. . .
696.0
661.0
+
1.4
+
1
8
+
1
6
-25
2
- 9
8
35.0
Mar.
13
15. . .
695.4
669.6
—
8.4
+
0
8
—
5
0
-24
8
- 1
0
25.8
Mar.
20
22. ..
693.8
656.4
+
0.4
9
4
3
0
-30
6
- 6
8
37.4
1 In this experiment the steer fasted 3 days. During the third day, steers C and D each
lost 4.2 kg. in body-weight.
1 The afternoon feed was withheld on this day, as it was planned to measure the standard
metabolism the next morning, but the experiment was not made.
marily to study the influence of environmental temperature upon metabo¬
lism, the two animals, C and D, were fed practically a constant ration for
several months, receiving 9 kg. of hay and 2 kg. of meal daily from Novem¬
ber 20, 1922, until March 27, 1923. During this time they were subjected
at different times to short 2-day fasts, and on one occasion to a 3-day fast.
The data for the initial and the final body-weight, the total loss in weight,
and the changes in body-weight on the three days with food before the fast
and on the several days of fasting, are incorporated in Table 13.°
° In Table 13 the change in weight during the last 24-hour period of fasting and the live weight
at the end of the fast have been corrected for the first feed after the fast, consumed usually
during the last 3 hours of the 24 hours, but in two cases consumed during the la6t 6 hours.
BODY-WEIGHT
61
The changes in body-weight before fasting show the usual fluctuations
noted in Table 12, and are due probably to changes in water-content and to
irregularity in the expulsion of feces. The losses in weight on the first day
of fasting are remarkably uniform with both animals, explainable undoubt¬
edly by the fact that the feed-level prior to the fasts was uniform in all
instances, and also by the fact that in every instance no water was drunk
at the beginning of the first fasting day. Thus, with steer C the loss in
weight on the first day ranges only from 24 to 30.8 kg. In the case of steer
D the loss on the first day ranges from 24.8 to 35.0 kg. In general, the uni¬
formity of ration has resulted in a strikingly uniform body-loss on the first
day, amounting on the average to 27 kg. with both steers. There are obvi¬
ously no instances of plus values, and the wide discrepancies noted in
Table 12 here disappear. On the second day there is a pronounced drop in
the loss to a level of not far from 3 to 4 kg. in the case of steer C, but in the
case of steer D the change, although pronounced, is not so regular, since
the loss ranges from 1.0 kg. to as high as 11.2 kg., being on the average
about 6 kg. This decrease in the loss and the difference between steers C
and D on the second day may be partly explained by the fact that steer C
drank water in every instance at the beginning of the second day, but steer
D drank only in the case of the first five fasts and the last two fasts.
In the long fasts at different feed-levels, reported in Table 12, the losses
on the second day were very irregular and much higher than in these 1923
fasts, particularly with steer C. There are three explanations for this. In
the first place, the ration preceding each of the short fasts in 1923 was the
same, whereas the feed-levels preceding the longer fasts varied greatly. In
the second place, the second day of fasting in the short fasts began exactly
30 hours after the last feed in every case, and the amount of the last feed
was always essentially the same. In the long fasts, on the contrary, the
second day did not begin the same number of hours after the last feed in
every case, the time varying from 22 to 32 hours after the last feed. More¬
over, the last individual feed preceding these long fasts varied greatly in
amount and character. Furthermore, there was greater irregularity in water
intake on the second day of the longer fasts.
There was one 3-day fast with each animal in the 1923 series, in which by
chance the weight-loss of both steers was actually the same on the third
day, namely, 4.2 kg. This loss is lower, as a matter of fact, than any of the
other values found on the third day with these animals in the longer fasts,
save in the case of the November 1922 fast of steer C and the January 1922
fast of steer D.
Aside from the first fast in 1923, which was 3 days long, the animals as
a rule fasted about 51% hours, so that the total losses are comparable. In
51% hours the total loss in weight of steer C during these short fasts aver¬
aged 30 kg, and the total loss of steer D averaged 34 kg. Again a much
greater regularity was exhibited by steer C than by steer D.
62
METABOLISM OF THE FASTING STEER
Losses in Body-weight During 4-Day Fasts under Similar Conditions
The losses noted during a series of 4-day fasts in April and May 1924,
when the animals remained inside the respiration chamber for three out of
the four days, are recorded in Table 14. Prior to these fasts all four animals
had been upon a reasonably uniform nutritive plane for from 4 to 8 weeks.
They were placed in the respiration chamber after having been 24 hours
without food, and were left there for 3 consecutive days. The body- weights
were determined only at the beginning and end of the respiration experi¬
ments, and hence the data are available only for the total loss in weight in
3 days instead of the losses during four individual 24-hour periods, i. e., the
first day’s loss was not obtained.
Table 14. — Losses in body-weight during S days 1 of fasting under similar conditions
Steer
Dates of fasts
Body-
weight in
November
1923
Body-
weight at
beginning
of fast1
Body-
weight at
end of
fast
Total
loss in
body-
weight
1924
kg.
kg.
kg.
kg.
F
Mar. 31 to Apr. 4 .
291.0
295.2
271.8
-23.4
E
Apr. 8 12 .
266.2
280.0
260.8
-19.2
C
Apr. 22 26 .
723.8
669.6
620.0
-49.6
D
May 13 17 .
707.0
664.6
621.4
-43.2
1 Beginning 24 hours after food.
The two young animals, E and F, were first studied. In consideration of
the fact that steer F weighed essentially the same at the beginning of his
fast in April 1924 as at the beginning of the experimental season, namely,
November 19, 1923, and that previous to this April fast he had been on a
submaintenance ration for several months and had then fasted 6 days in
February, it can be seen that, judging from body-weight alone, he had
reached his original condition. But meanwhile he had grown, and was
nearly 5 months older. In all probability, therefore, he was still in a dis¬
tinctly undernourished condition. Steer E had also passed through a period
of undernutrition and a 5-day fast prior to his fast in April 1924, but since
his weight at the start of the April fast was somewhat greater than that
noted at the beginning of the season, one would infer that he was in a some¬
what better nutritive state than steer F. The two large animals, C and D,
weighed noticeably less than at the beginning of the season on November
5, 1923, when they came off pasture, having been through a prolonged period
of undernutrition and a 10-day fast previous to their fasts in April and May
1924. Hence they were distinctly below par at the time of these particular
experiments.
In these 4-day fasts the younger steers, E and F, lost 19.2 and 23.4 kg.,
respectively, and the older and larger steers, C and D, lost 49.6 and 43.2
kg., respectively. Little is to be gained by attempting to apportion these
losses over the four days and compare them with the losses during the two
days in the short fasting experiments, or, indeed, with the individual days in
the prolonged fasting experiments. The chief point illustrated by these
4-day fasts is that under essentially uniform treatment the two animals in
LOSS THROUGH THE LUNGS AND SKIN
63
each pair are fairly close physiological duplicates. It is impracticable to
attempt to compare the weight-losses of various animals during fasting
unless experiments follow the same rationing and unless the withholding of
food is made at exactly the same time, the last feed having been of the
same amount. If duplicate experiments are made under these conditions,
the body-weight tables indicate that a reasonably close physiological dupli¬
cation may be expected with two animals of the same size and age, receiving
the same character and amount of feed.
General Conclusion with Regard to Significance of Changes in
Body-weight
From the analysis of the changes in body-weight, not only during the
long fasts but likewise during the 2-day fasts and during the consecutive
3-day experiments inside the respiration chamber, it is clear that the changes
in body-weight vary greatly with respect to the animals, the different days
of fasting, and the different fasts. It has already been seen that some of
the major differences are explained by differences in water intake and, to a
much less degree, by differences in the output of feces or urine. In each of
the first four long fasts the total loss in weight of steer D was much les3
than that of steer C. If one considers that the water drunk during each of
these fasts offsets a theoretical further loss which would have been recorded
on the scales, and if one adds the total amount of water consumed to the
total loss in weight in each case, one finds that the differences between the
two animals practically disappear. A careful study of the amounts of
water consumed on the different fasting days, the weights of urine and
feces, and particularly the insensible perspiration, makes it evident that the
differences in live weights themselves are wholly without significance unless
the changes in these other factors are taken into consideration. The use
of live weight as an index of gain or loss in body-tissue is, therefore, clearly
ruled out.
LOSS THROUGH THE LUNGS AND SKIN
As early as in the observations of Sanctorius0 and thereafter in the obser¬
vations of Bischoff6 and of Bischoff and Voit,c and of Grouven,d varying
degrees of importance were attached to the loss through the lungs and skin
of an animal used for experimental research. Sanctorius especially laid
great stress upon this loss, which he determined in his own case by sitting
upon a chair suspended from a steelyard and noting his loss in weight from
hour to hour under various conditions of bodily, mental, and digestive
activity. These determinations were the basis of a large number of
aphorisms published by him. When quantitative methods in studying food
ingestion and the excretion of urine and feces, and particularly when Henne-
berg’s schematic conception of the animal body began to be applied, appar¬
ently the significance of the loss through the lungs and skin was disregarded.
“ Sanctorius, Medicina Statica, 1614; translated by John Quincy, London, 2d ed., 1720.
b Bischoff, Der Harnstoff als Maass des Stoffwechsels, Giessen, 1853.
e Bischoff and Voit, Die Gesetze der Ernahrung des Fleischfressers durch neue Untersuchungen,
Leipzig and Heidelberg, 1860.
d Grouven, Physiologisch-chemische Fiitterungsversuche. Zweiter Bericht liber die Arbeiten
der agrikulturchemischen Versuchsstation zu Salzmiinde, Berlin, 1864.
64
METABOLISM OF THE FASTING STEER
Since recent researches at the Nutrition Laboratory0 on humans have indi¬
cated that there is a reasonably close correlation between insensible loss and
general metabolism, a special effort was made in studying these steers to
secure the data for the accurate computation of the insensible loss.
The daily changes in gross live weight of a steer, especially during fasting,
have little direct quantitative significance, because, as has just been empha¬
sized, they are profoundly affected by the amount of water consumed and
the feces and urine passed. If 1 kg. of water is taken into the mouth and is
subsequently excreted in the urine, it plays practically no role in the
metabolism of the animal. Similarly, if there are 100 kg. of ballast or fill
in the intestinal tract of a ruminant at the beginning of a fast and 40 or 50
kg. of this fill are excreted as feces, this again has no particular bearing upon
the metabolism of the animal. The insensible loss through the lungs and
skin does play a role in the metabolism, however, for through the lungs and
skin, chiefly through the lungs, passes the carbon dioxide formed in the
process of oxidation. The total weight of carbon dioxide is not wholly
derived from body-tissue, for the oxygen comes from the oxygen in the air,
but the carbon of the carbon dioxide does represent true body-loss. The
amount of carbon excreted can be computed, provided that the total carbon-
dioxide output is measured either during 24 hours inside of a respiration
chamber or in several periods throughout the day representative of the
entire day. The water given off from the skin doubtless existed in large
part as preformed water, but in the process of oxidation, particularly of
fat, water is formed in which each gram of hydrogen requires 8 grams of
oxygen, which it gets from the air. Furthermore, in the oxidation of carbo¬
hydrates there is a certain amount of water of chemical constitution, namely,
the hydrogen and oxygen of the molecule, which exists in the proper propor¬
tion to form water. In the insensible loss from the lungs and skin, there¬
fore, the most important factor bearing upon the metabolism is the carbon
of carbon dioxide. The water given off is not, however, without significance
in connection with metabolism, for it represents a method of heat-loss, each
gram of water thus vaporized from the lungs and skin requiring 0.586
calorie for its vaporization.
The insensible loss, therefore, is made up of the carbon of the fat, protein,
and carbohydrate burned in the body and the organic hydrogen and oxygen
preexisting in these molecules, and, in addition, it is made up of the very
large and variable factor of water vaporized through the lungs and skin. An
analysis of the nature of the insensible perspiration is of great physiological
importance. Prior to such an analysis, however, it is advisable to know the
actually measured insensible loss of these steers and to note whether it has
any relationship to feed or to lack of feed, activity, and other factors which
are known to affect heat-production, i. e., the vaporization of water and the
production of carbon dioxide.
° Benedict, Carnegie Inst. Wash. Pub. No. 203, 1915, p. 84; Benedict and Hendry, Boston Med.
and Surg. Journ., 1921, 184, pp. 217, 257, 282, 297, and 329; Benedict, Boston Med. and Surg.
Journ., 1923, 188, p. 127; Benedict, Bull. Soc. Sci. d’Hygiene Alimen., 1923, 11, p. 343; Benedict,
Schweiz, med. Wochenschr., 1923, 53, p. 1101; Benedict, The correlation between perspiratio
insensibilis and total metabolism, Collection of articles dedicated to the seventy-fifth birthday of
Professor I. P. Pawlow, published from the Institution of Experimental Medicine in Leningrad,
1924, p. 193; Benedict and Root, Arch. Intern. Med., 1926, 38, p. 1.
LOSS THROUGH THE LUNGS AND SKIN
05
The data for computing the insensible loss must include accurate weigh¬
ings of food and water intake, feces, urine, and live body-weight. The
quantity of water drunk by the animal should be recorded with particular
care, since the variations in the amount of water consumed at different times
are much greater than the variations in the food consumed or in the excre¬
tion of urine and feces from day to day. All of these measurements must
be made in definite periods, so that the computation of the insensible loss
may represent the loss during a known length of time. For this purpose the
steers were kept in metabolism stalls. The routine was to weigh the animal
each day at exactly the same time (i. e., representing a 24-hour period), at
which time the urine bottles and feces containers were removed, and clean,
previously weighed receptacles substituted. The animal was then at once
allowed to drink and the amount consumed was doubly checked by noting
both the loss in weight of the water container and the gain in weight of the
animal. The food was always given in carefully weighed portions, usually
twice during the 24-hour period, about 4 p. m. and 7 or 8 a. m. Under
these conditions all the data are at hand for computing exactly the insensible
loss during a 24-hour period. Thus, to the initial weight of an animal on
a given date at 2 p. m. is added the weight of food and water consumed
during the ensuing 24 hours. To the weight of the animal at the end of the
24 hours is added the weight of feces and urine passed during the 24 hours.
This sum is subtracted from the sum of the initial body-weight, water, and
food, and the difference represents the insensible loss.
In computing this loss the exact times when food and water are consumed
and feces and urine are excreted must be known. Only too frequently
experimental data are recorded in such a manner that it is impossible to
subdivide the weights of urine, feces, and food, and credit them to the
proper 24-hour periods, and although all the weights may represent 24-hour
periods, they do not invariably represent the same 24 hours. In our earlier
report on undernutrition in steers0 we found to our chagrin that in many
instances our own data did not fulfill the above specifications, and, profiting
by this experience, we attempted to have the data in this report uncon¬
taminated by such errors. Even with all the precautions just mentioned,
however, gross errors are occasionally found that are extremely annoying.
It is hoped in the future to have every weighing doubly checked, and thus
rule out, if possible, any errors of this type. An inherent difficulty in study¬
ing the insensible loss of these large animals is the weighing of the animal
itself. To determine the live weight of an animal weighing 700 kg. to within
0.1 per cent is very difficult. The scales (see p. 55 for description) were
reasonably accurate, but it required all the skill of the technician to secure
accurate weights. It is seriously to be questioned whether it is right to
report the live weights any more closely than to within the nearest half
kilogram. Obviously, the weights of water, feed, feces, and urine can be
obtained to within 10 grams.
° Benedict and Ritzman, Carnegie Inst. Waah. Pub. No. 324, 1923, p. 85.
66
METABOLISM OF THE FASTING STEER
Insensible Perspiration During Food Periods and During 24 Hours
Without Food
Inasmuch as a study of the insensible loss of large ruminants has not been
presented, so far as we are aware, since the days of Grouven, it seems justi¬
fiable to discuss, first, some of the data regarding the insensible loss of our
steers when on feed before considering the losses during fasting. Frequently
during the 4 years’ study of these animals the so-called “standard metabo¬
lism,” 24 hours after the last feed, was determined with the respiration
chamber. In Table 15 are recorded the insensible losses of steers C, D, E,
and F for those days when the standard metabolism was measured. In
addition, the losses are given for the three days prior to these standard
metabolism experiments, when the steers were receiving food daily at a
nutritive level which had prevailed for some time. The loss on the day of
the standard metabolism measurement in every case represents the loss
during the first 24 hours without food, although in most instances the animal
was fed just before the end of the 24 hours.
The variability in the insensible loss at the times of the different experi¬
ments is very pronounced. In the case of steer C, the values for the
insensible loss noted 3 days before the standard metabolism experiments
range from 3.8 to 15.6 kg. Similar ranges in the losses occur 2 days and one
day prior to the experiments. On the days of the standard metabolism
experiments, when the animal had usually been without food for the entire
24 hours, the range is somewhat smaller, i. e., from 2.2 to 12.8 kg., and the
deviation from an average value is obviously somewhat lessened, due prob¬
ably in large part to the entire lack of food. With steer D wider differences
are noted, the loss ranging from 4.4 to 14.4 kg., 3 days before the metabo¬
lism experiment, from 4.2 to 18.4 kg., 2 days before, from 4.6 to 18.4 kg. on
the day before, and from 3.6 to 17.6 kg. on the day of the experiment itself.
With the smaller steers, E and F, the variability is naturally much less, the
widest range during the food days in the case of steer E being only from
2.6 to 9.4 kg., while on the day of the standard metabolism experiment the
range is only from 2.4 to 7.0 kg. With steer F the picture is essentially the
same.
The general picture of the range in daily losses is that there are gross
differences in the insensible loss at different times of the year. A closer
examination of the data in Table 15, however, shows that on any three suc¬
cessive days under the same feeding conditions the loss remains reasonably
uniform, and that on the days of standard metabolism experiments, when
food is withheld, the loss usually decreases noticeably.
The large differences in the insensible perspiration noted in Table 15 are
in large part explained by the differences in the feed-level. When steers C
and D were on a realimentation or a maintenance feed-level, the insensible
perspiration was almost invariably considerably higher than when they
were on a submaintenance feed-level. For example, in the case of steer C
the return to maintenance feeding on June 18, 1923, immediately resulted
in a marked increase in the insensible perspiration. This same picture is
likewise noted with steer D. It is not clear, however, that the insensible
perspiration is absolutely uniform from day to day even upon the same
LOSS THROUGH THE LUNGS AND SKIN
67
Table 15. — Daily insensible loss during
S days with food, followed by 1 day without food1
Steer and date of standard metab¬
olism experiment
Food-
level1
Days (on food) before standard
metabolism experiment
Day of
experi¬
ment*
3
2
1
Steer C:
kg.
°C.
kg.
°C.
kg.
°C.
kg
° C.
Dec.
17,
1921 .
R
3.8
18
3.2
5
3.8
15
4.8
21
Dec.
22,
1921 .
R
4.6
12
5.0
20
8.0
13
2.2
7
Jan.
23,
1922 .
R
9.4
14
10.4
19
12.4
18
6.4
12
Mar.
31,
1922 .
M
9.6
18
9.0
17
11.0
19
7.4
20
May
9,
1922 .
R
7.4
19
8.0
19
8.0
18
5.2
18
Dec.
13,
1922 .
M
11.5
24
13.8
20
14.4
23
9.0
18
Dec.
18,
1922 .
M
15.6
27
14.6
24
16.0
26
12.8
26
Dec.
21,
1922 .
M
12.8
26
14.2
23
13.4
24
9.4
22
Dec.
26,
1922 .
M
13.8
21
16.6
27
12.8
20
11.2
26
Dec.
29,
1922 .
M
11.2
26
15.2
28
11.4
22
6.6
15
Apr.
3,
1923 .
M
9.0
12
9.4
10
8.4
13
9.6
21
Apr.
11,
1923 .
M
11.2
17
7.8
12
10.8
16
6.4
14
Apr.
18,
1923 .
M
9.4
13
10.2
15
10.4
15
8.2
18
Apr.
24,
1923 .
M
15.2
24
14.8
24
9.6
14
6.0
12
May
5,
1923 .
S
6.8
18
5.6
18
7.6
21
7.2
22
May
11,
1923 .
s
6.6
20
7.2
20
6.4
16
4.4
16
May
18,
1923 .
s
5.8
19
5.8
19
8.8
24
5.2
18
May
24,
1923 .
s
5.4
21
5.2
18
5.8
17
4.4
17
June
18,
1923 .
M
11.4
20
9.6
18
12.8
20
7.4
20
Steer D:
Dec.
17,
1921 .
R
4.4
18
4.2
5
4.6
17
6.8
21
Dec.
22,
1921 .
R
6.4
12
6.0
20
7.8
13
3.6
7
Jan.
23,
1922 .
R
8.2
14
10.8
19
11.0
18
6.2
12
Mar.
31,
1922 .
M
9.2
18
8.6
17
9.8
19
6.8
20
May
9,
1922 .
R
5.8
19
7.2
19
6.6
18
5.6
18
Dec.
15,
1922 .
M
14.4
23
12.0
18
16.0
24
13.0
27
Dec.
19,
1922 .
M
12.6
24
15.6
26
16.6
26
11.8
23
Dec.
22,
1922 .
M
11.8
23
11.4
24
12.8
22
9.6
22
Dec.
30,
1922 .
M
12.6
28
10.8
22
8.8
15
17.6
13
Jan.
3.
1923 .
M
7.2
11
12.8
15
9.8
12
6.2
11
Apr.
4,
1923 .
M
8.8
10
9.4
13
14.6
21
6.6
18
Apr.
12,
1923 .
M
7.6
12
13.8
16
7.6
14
7.8
14
Apr.
19,
1923 .
M
9.2
15
8.4
15
9.2
18
6.4
14
Apr.
25,
1923 .
M
13.2
24
9.8
14
6.8
12
9.0
20
May
4,
1923 .
s
6.6
6.0
18
5.8
18
5.8
21
May
12,
1923 .
S
7.6
20
5.6
16
5.4
16
8.2
24
May
19,
1923 .
s
4.8
19
8.2
24
4.8
18
5.6
21
May
25,
1923 .
s
5.4
18
7.4
17
5.4
17
6.2
22
June
1,
1923 .
s
6.2
20
6 2
18
5.6
19
7.2
19
June
8,
1923 .
s
11.8
28
11.0
27
7.0
22
4.2
18
June
16,
1923 .
M
8.0
16
7.6
18
9.0
20
9.4
18
June
22,
1923 .
M
14.0
27
18.4
30
18.4
30
12.2
26
Steer E:
Nov.
26,
1923 .
M
7.2
13
6.8
21
8.6
23
6.4
16
Dec.
3,
1923 .
M
7.8
15
8.0
14
7.4
12
5.8
15
Dec.
10,
1923 .
M
8.0
16
6.4
13
9.4
18
6.6
20
Dec.
17,
1923 .
M
8.8
15
6.8
13
6.0
14
7.0
14
Dec.
28,
1923 .
S
3.0
10
2.6
13
3.8
15
4.6
15
Dec.
31.
1923 .
s
4.6
15
4.2
16
3.0
13
3.2
14
Jan.
8,
1924 .
s
2 4
11
3 8
15
2.4
15
Jan.
14,
1924 .
s
3 2
12
3.2
14
2.6
Jan.
21,
1924 .
s
3.4
14
3.0
18
3.6
11
Jan.
28,
1924 .
s
3.0
16
3.4
10
2.6
10
3.0
11
Feb.
4,
1924 .
s
3.2
13
4.0
15
2.8
13
2.4
15
68
METABOLISM OF THE FASTING STEER
Table 15. — Daily insensible loss during 3 days with food, followed by 1 day without food1 — Con.
Steer and date of standard metab¬
olism experiment
Food-
level1
Days (on food) before standard
metabolism experiment
Day of
experi¬
ment*
3
2
1
Steer F:
kg.
°C.
kg.
°C.
kg.
°C.
kg.
°C.
Nov.
27, 1923 .
M
8.0
21
7.8
23
7.6
16
5.4
18
Dec.
4, 1923 .
M
7.0
14
5.8
12
7.0
15
5.4
16
Dec.
11, 1923 .
M
3 6
13
8.6
18
8.0
18
Dec.
18, 1923 .
M
6.6
13
7.0
14
7.2
14
4.0
10
Dec.
29, 1923 .
S
2.4
13
3.4
15
4.2
15
3.4
16
Jan.
2, 1924 .
S
3.2
13
3.2
14
4.0
15
3.2
12
Jan.
9, 1924 .
S
3.4
15
3.0
15
3.2
15
2.8
18
Jan.
17, 1924 .
S
2.6
. .
3.0
15
2.8
16
3.4
18
Jan.
22, 1924 .
s
2.6
14
3.6
18
2.4
11
2.6
13
Jan.
29, 1924 .
s
1 8
10
2.4
10
3.2
18
Feb.
5^ 1924 .
s
2.4
15
2.8
13
3.2
15
3.0
17
1 The temperature figure at the right of each insensible perspiration figure represents the
stall temperature during the same 24 hours in which the insensible perspiration was measured.
* R, realimentation after fast (steers C and D, 4 to 8 kg. hay); M, maintenance level (steers
C and D, 9 kg. hay and 2 kg. meal, Dec. 13, 1922, to Jan. 3, 1923, and 9 kg. hay, Mar. 31, 1922,
Apr. 3-25, 1923, and June, 1923; steers E and F, 5 kg. hay and 0.68 kg. meal); S, submainte¬
nance level (steers C and D, 4.5 kg. hay; steers E and F, 2.5 kg. hay and 0.30 kg. meal).
* During the 24 hours represented by the insensible perspiration recorded for the day of the
experiment either no food at all was eaten or no food was eaten until near the end of the 24
hours.
ration, for relatively wide differences do still exist. But in general, with the
submaintenance ration the insensible loss is low and with the maintenance
ration it is high. The situation is exactly duplicated in the case of steers E
and F, but since their body-weights are much smaller, the insensible per¬
spiration is naturally smaller than that of steers C and D. Even with these
two smaller animals, however, it can be seen that on submaintenance rations
the insensible perspiration is perceptibly lower than on maintenance rations.
Thus, the data show clearly a relationship between the feed-level and the
insensible perspiration. Since it is known that with the higher feed-level
there is a higher metabolism, this relationship between the feed-level and
the insensible loss is the first clue that there is a relationship between the
insensible perspiration and the metabolic level. This latter relationship ha3
been most carefully studied with humans and has been shown to exist with
remarkable accuracy, indeed, so much so that it has been proposed to pre¬
dict the metabolism of humans from the insensible perspiration carefully
determined under standard conditions.0
In Table 15 the individual figures for the separate days have been given
and no attempt has been made to smooth out the irregularities, but it is
clear that with ruminants the feed-level is not the sole factor in determining
the intensity of the insensible perspiration. Indeed, we noted early in the
research that the environmental temperature played a not insignificant role.
Thus, the variations in the insensible loss occasionally noted even on con¬
secutive days, i. e., with a constant feed-level, can be fairly closely corre-
Benedict and Root, Arch. Intern. Med., 1926, 38, p. 1.
LOSS THROUGH THE LUNGS AND SKIN
69
lated, in most instances, with large differences in the environmental tem¬
perature. Since the insensible loss is made up in large part of vaporized
water, it is not surprising that changes in environmental temperature affect
the insensible loss, because of their effect upon the vaporization of water
both from the lungs and skin. A full understanding of the data in Table 15
can therefore only be had by taking into consideration the stall tempera¬
tures under which the determinations of the insensible perspiration were
made. The stall temperatures, expressed in degrees centigrade, have
accordingly been incorporated in the table.
A comparison of the insensible losses and environmental temperatures on
consecutive days, i. e., with constant feed-level, indicates that generally the
high temperature is accompanied by a relatively high insensible loss. There
are, however, exceptions to this with sufficient frequency to make it difficult
to draw more than a general conclusion. Thus, in the experiment of Decem¬
ber 22, 1921, steer C had an insensible perspiration of 4.6 kg. 3 days before
the metabolism test, 5.0 kg. 2 days before, and 8 kg. on the day before, with
stall temperatures of 12°, 20°, and 13° C., respectively. On the day of the
standard metabolism experiment the loss was but 2.2 kg., with a tem¬
perature of 7° C. The differences in temperature and the fairly even insen¬
sible perspiration in these first experiments with steer C can be discussed
only with considerable caution. Since the first two experiments with steer
C were made during the realimentation period following a 7-day fast, it
is not inconceivable that the insensible perspiration may have reached a
minimum level due to the previous fasting, below which it could not drop
appreciably even with a marked fall in temperature. Hence the low values
of 3.2 kg. on the second day before the experiment on December 17, with
a temperature of 5° C., and of 3.8 kg. on the next day, with a rise in tem¬
perature of 10° C., may be explained by the fact that the animal had
already reached a very low level as a result of the 7-day fast.
The general picture, however, is that with high environmental tempera¬
tures and a constant feed-level there appears frequently a large insensible
loss, which might be caused by an increased vaporization of water from
the lungs and skin as a result of the high temperature. Obviously, wind
velocity and humidity should also be taken into consideration. When in
the metabolism stalls, the animals were not exposed to drafts and pre¬
sumably on each day the movement of air was essentially the same, for the
laboratory was well constructed, so that there was a minimum amount of
draft. Inside the respiration chamber the air was invariably moved, but
not violently, by an electric fan, to insure equalization in its chemical com¬
position. The steers were therefore not subjected to excessive movement of
air during the metabolism experiments.
From this analysis of the data in Table 15, the conclusion can be drawn
that the insensible loss from day to day, under the same conditions of feed¬
ing, and particularly if the environmental temperature is constant, is rea¬
sonably uniform. Indeed, this conclusion is substantiated by Grouven’s
study of the insensible loss, which he computed to be astonishingly constant
from day to day with animals under uniform conditions of feed and tem¬
perature. The withholding of food, on the day of the standard metabolism
70
METABOLISM OF THE FASTING STEER
experiment, results usually in a pronounced fall in the daily insensible loss,
provided that the temperature conditions remain uniform. Since the metabo¬
lism is known to be lowered as the result of the absence of digestive activity,
it would appear as if, in this respect at least, the insensible loss were corre¬
lated with the total heat-production.
Insensible Loss During Three Days with Food, Followed by Two and
Three Days Without Food, at a Maintenance Level of Nutrition
In connection with another series of respiration experiments carried out
on steers C and D during short periods of fasting at a maintenance feed-
level, records of the insensible loss are available for the three days with
food prior to the fast and for each of the two or three days of fasting. These
records are given in Table 16, in which the first day of fasting corresponds
exactly with the day of the standard metabolism experiment recorded in
Table 15, except that the steers were given no feed at all during this first
day, while on the day of the standard metabolism experiment they were in
most cases fed just before the end of the day. But obviously in this latter
Table 16. — Daily insensible loss during 3 days with food, followed by 2 days without food
Steer and
dates of
fasts
(1923)
Days before fast
(with food)
Days fasting1
3
2
1
1
2
Steer C:
kg.
°C.
kg.
°C.
kg.
°C.
kg.
°C.
kg.
°C.
Jan 3 to
6!
12.6
15
9.8
12
9.0
11
6.2
6
3.0
9
Jan. 15
17
15.2
25
13.4
20
15.6
26
11.8
29
3.0
12
Jan. 21
23
13.6
28
18.6
27
18.0
29
10.8
28
4.4
7
Jan. 28
30
8.8
11
16.8
26
9.4
11
4.8
8
5.0
25
Feb. 5
7
9.8
12
8.2
4
7.8
7
5.2
6
2.8
5
Feb. 11
13
8.2
8
10.2
10
9.2
11
4.6
8
2.8
8
Feb. 18
20
7.4
-3
7.2
3
8.0
7
3.4
4
3.6
0
Mar. 1
3
9.2
12
10.8
13
9.4
11
6.2
12
3.6
14
Mar. 8
10
6.6
4
8.0
3
7.0
4
4.6
4
3.0
6
Mar. 15
17
11.2
9
10.4
7
9.8
5
5.2
8
3.8
8
Mar. 22
24
15.2
19
18.8
24
3 20.2
27
14.8
26
8.8
22
Steer D:
Jan. 9 to
122 * 4
8.2
8
4 5.6
11
8.2
12
6.4
13
3.4
9
Jan. 17
19
16.4
26
17.8
29
11.2
12
6.0
12
8.2
28
Jan. 25
27
9.2
7
10.6
13
8.6
11
5.8
11
6.8
26
Feb. 1
3
16.0
25
18.2
28
16.8
23
12.6
23
3.4
12
Feb. 8
10
7.6
6
5.6
5
8.0
7
5.0
8
3.2
10
Feb. 14
16
6.8
8
8.2
8
6.8
6
4.6
-3
2.4
-3
Feb. 22
24
7.6
0
6.4
6
7.6
6
4.4
2
3.2
-2
Mar. 5
7
10.0
14
9.0
11
7.4
5
3.8
4
3.8
3
Mar. 13
15
8.2
5
8.8
7
10.2
9
6.0
7
3.8
5
Mar. 20
22
10.0
7
19.4
24
15.6
19
14.2
24
10.4
27
1 The first day begins at 2 p. m., the last feed being given between 7 and 8 a. m. The loss
during the last day of fasting may be influenced by the first feed following the fast, given usually
during the last 3 hours of the day (in two cases given during the last 6 hours).
2 On Jan. 6 and 12 steers C and D fasted a third day, and the insensible perspiration was 2.8 and
3.0 kg., respectively.
5 High value possibly due to rise in temperature and limitation of water consumption. After
Mar. 15 the steers were limited to 27 kg. of water daily.
4 Food withheld for respiration experiment, but experiment not made.
LOSS THROUGH THE LUNGS AND SKIN
71
instance the weight of feed was taken into consideration in computing the
insensible perspiration.
From the data for the three days with food prior to the fast, essentially
the same conclusion may be drawn as was drawn from the data in Table 15,
namely, that under uniform conditions of feeding and environmental tem¬
perature the insensible loss on three successive days is reasonably constant.
When there is a marked rise in temperature, the insensible loss is usually
somewhat increased. On the first day of fasting, in contradistinction to the
results on the days of standard metabolism experiments, there is invariably
a decrease, at times very pronounced. On the second day there is usually a
still greater decrease. The loss on the first day of fasting ranges in the
case of steer C from 3.4 to 14.8 kg. and in the case of steer D from 3.8 to
14.2 kg. This variability in large part disappears on the second day, the
range being only from 2.8 to 8.8 kg. with steer C and from 2.4 to 10.4 kg.
with steer D. The influence of environmental temperature is well marked.
Thus, on the second day of fasting the two greatest losses with steer C
(5 and 8.8 kg.) are coincidental with the two highest temperatures (25° and
22° C.), and with steer D the highest temperatures (28° and 27° C.) occur
simultaneously with the two highest losses (8.2 and 10.4 kg.). In the one
experiment when the steers fasted for 3 days the loss on the third day is
essentially that on the second day, namely, about 3 kg. with each animal.
In Table 16, due in large part to the fact that the feed-level was in all
cases constant, the evidence is much more striking than in Table 15 — that
there is a regular loss from day to day with uniform conditions of feed and
environmental temperature. During fasting there is invariably a pro¬
nounced decrease in the insensible perspiration on the first day and a much
greater decrease on the second day. The loss of both animals is remarkably
uniform throughout the entire series on the second day, except in the last
experiment with each steer, when a high insensible loss, probably due to the
high environmental temperature, was noted.
Insensible Loss During Five to Fourteen Days without Food
Having noted the reasonable regularity in the insensible loss on succeed¬
ing days of uniform feed and environmental temperature, the pronounced
decrease in loss on the first day of fasting, and the still further pronounced
decrease on the second day to a reasonably uniform loss in the case of both
animals of about 3 or 4 kg. per day, we may pass to an examination of the
insensible loss during longer periods of fasting, as recorded in Table 17.
In these longer fasting experiments unusual precautions were taken to
secure the greatest accuracy in all records of weights, additional student
labor being employed to check the weights. Even with these precautions,
the record for steer C on the day before the fast in December 1921 has had
to be discarded because of an obvious error in recording one of the weights.
On the three successive days prior to each fast there is a reasonable
degree of uniformity in the loss, although the level of the loss varies greatly
in the different experiments. Thus, the average loss of steer C for 3 days
prior to the March 1924 fast was 6.9 kg., but the average amount prior to
the other fasts was approximately twice this amount. The same picture is
shown in the losses of steer D during the three days before the fasts. The
72
METABOLISM OF THE FASTING STEER
Table 17. — Daily insensible perspiration during 8 days unth food, followed by 5 to 14 days
without food
Steer and dates of fasts
Days before fast
(with food)
Days fasting
3
2
1
1
2
3
Steer C:
kg.
° C.
kg.
°C.
kg.
°C.
kg.
°C.
kg.
°C.
kg.
°C.
rw fi tn IS 1 Q21 .
10 0
9
10 0
7
4 0
5
3 4
5
1 6
15
Jan. 4
14, 1922 .
16.0
16
13.8
16
12.0
14
11.6
20
7.0
20
4.8
20
Apr. 17
May 1, 1922 .
17.2
21
15.4
17
16.6
20
12.6
20
6.0
20
7.2
20
June 1
7, 1922 .
18.4
24
16.6
22
16.8
23
10.8
23
5.2
22
5.6
23
Nov. 6
16, 1922 .
12 6
7.8
8 0
Nov. 4
10’ 19231 .
6.2
3.8
Mar. 3
13, 1924 .
7.4
13
6.6
16
6.8
17
*2.S
14
1.4
16
2.6
16
Steer D:
Dec. 6
to 13, 1921 .
10.0
9
9.0
7
9.2
7
4.4
5
3.2
5
3.2
15
Jan. 4
14, 1922 .
17.0
16
15.0
16
16.2
14
11.4
20
7.0
20
5.0
20
Apr. 17
May 1, 1922 .
15.0
21
13.2
17
15.8
20
12.4
20
4.2
20
5.2
20
June 1
6, 1922 .
16.6
24
14.2
22
15.8
23
9.2
23
6.2
22
6.2
23
Nov. 6
14, 1922 .
14 0
9 4
8 8
Nov. 4
9, 19231 .
11 6
5 0
Mar. 3
12, 1924 .
5.6
13
7.4
16
6.2
17
s3.0
14
3.4
16
2.8
16
Steer E;
Feb. 12 to 17, 1924 .
3.2
12
2.4
12
3.4
13
3.2
16
1.8
15
2.2
16
Steer F:
Feb. 12 to 18, 1924 .
2.8
12
3.0
12
2.0
13
3.6
16
1.2
15
2.2
16
Days fasting
fcteer and dates oi lasts
4
5
6
7
8
9
Steer C:
kg.
° C.
kg.
°C.
kg.
°C.
kg.
°C.
kg.
°C.
kg.
°C.
Dec. 6 to 13. 1921 .
3.2
20
2.8
18
2.2
17
2.2
20
Jan. 4
14, 1922 .
5.4
21
3.6
24
4.2
20
4.0
20
3.6
21
3.6
23
Apr. 17
May 1, 1922 .
2.4
15
3.2
20
4.2
22
3.8
22
3.6
22
4.0
23
June 1
7, 1922 .
4.6
25
5.0
27
Nov. 6
16, 1922 .
7.2
3.0
1.6
2.4
2.0
4.0
Nov. 4
10, 19231 .
3.0
2.8
Mar. 3
13, 1924 .
1.8
16
1.4
14
3.8
16
1.6
18
1.0
14
2.4
16
Steer D:
Dec. 6
to 13, 1921 .
3.8
20
3.6
18
2.4
17
3 2
20
Jan. 4
14, 1922 .
6.8
21
5.2
24
4.0
20
3.0
20
4.0
21
4.4
23
Apr. 17
May 1, 1922 .
4.2
15
3.0
20
3.8
22
3.6
22
3.8
22
4.6
23
June 1
6, 1922 .
5.2
25
Nov. 6
14, 1922 .
8.6
3.6
3.0
2 6
N ov. 4
9, 19231 .
4.8
4.0
Mar. 3
12, 1924 .
2.8
16
2.2
14
2.8
16
4.0
IS
2.2
14
1.4
16
Steer E:
Feb. 12
to 17, 1924 .
2.6
15
Steer F:
Feb. 12 to 18. 1924 .
1.8
15
2.2
14
1 Stall temperature, Nov. 5, 1923, ca. 20° C. ; Nov. 6, 19° C. in daytime, 15° C. at night; Nov.
8, from ca. 20° C. to 12° or 13° C.; daily records not kept of stall temperature until Nov. 23,
1923.
7 This value represents a period of only 17 hours, from 2 p. m. to 7 a. m.
LOSS THROUGH THE LUNGS AND SKIN
73
Table 17. — Daily insensible ■perspiration during 8 days with food, followed by 5 to 14 days
without food — Continued
Steer and dates of fasts
Days fasting
10
11
12
13
14
Steer C:
Jan. 4 to 14, 1922 .
kg.
4.2
4.8
2.0
4.0
3.4
°C.
23
20
16
23
20
kg.
°c.
kg.
°C.
kg.
°C.
kg.
° C.
Apr. 17 May 1, 1922 .
Mar. 3 13, 1924 .
2.0
22
3.0
21
3.6
21
3.4
21
Steer D:
Jan. 4 14, 1922 .
Apr. 17 May 1, 1922 .
3.2
22
2.8
21
4.2
21
2.8
21
striking difference between the loss prior to the fast in March 1924 and the
losses prior to the earlier fasts is explained by the fact that in March 1924
both animals were upon a submaintenance ration and were very much
undernourished. They had lost in live weight, to be sure, but not in pro¬
portion to the decrease in insensible loss. The losses on the days with high
temperatures are, in general, as noted earlier, somewhat higher than on the
days with low temperatures. Thus, with steer C, the minimum losses, aside
from those in March 1924, occur with temperatures of 7° and 9° C., and the
maximum losses are coincidental with temperatures of 22° to 24° C. The
minimum losses of steer D are also coincidental with the low temperatures
of 7° and 9° C., but the correlation between the high temperatures and the
maximum losses is not so pronounced as with steer C. The low values
found in March 1924 with both animals may not be ascribed to a low
environmental temperature, for the temperatures are not far from those in
January and April 1922, when twice as great an insensible loss was noted
with both animals. Thus the clear effect of submaintenance feeding is seen.
The smaller animals, E and F, were placed upon a submaintenance ration
prior to their long fasts. In their case there is considerable uniformity in
the loss from day to day prior to the fast, the values for the two steers
showing close agreement. The influence of temperature plays no role here,
for essentially the same temperature was noted each day.
In the fasting experiments proper there is in all instances a striking drop
in the loss of the two large steers on the first day of the fast, but practically
no change in the loss of the two small animals. The large decrease noted
in the fasts of steers C and D following the submaintenance feeding, how¬
ever, is partly explained by the fact that the first day of this fast was only
17 hours long, instead of the usual 24 hours. The losses of steers C and D
on the first day of fasting again show a reasonably close correlation with
the environmental temperature, since the lowest losses (with the exception
of the losses in the March 1924 fasts) occur at the lowest temperature
(5° C.). On the second day of fasting there is a still further drop in the
74
METABOLISM OF THE FASTING STEER
case of all animals, a drop which amounts on the average to somewhat less
than 50 per cent of the loss on the first day. On the third day a further
drop is noticed in 7 instances, but on the average the loss is not materially
different on the third day. After the third day, and more especially after
the fourth day, there is a general tendency for the losses to be not far from
3 to 4 kg., although occasionally values as low as 2 kg. and under are noted.
The uniformly low insensible loss from the second day of fasting to the
end of the fast in the case of both steers C and D in the fast following sub¬
maintenance feeding in March 1924 is striking. An average figure of 2.5
kg. per day could be assumed to represent their daily insensible loss during
this fast.
A striking correlation between environmental temperature and insensible
loss, after the first few days of fasting, is not apparent, although there are
instances when low values appear with low temperatures and higher values
with the higher temperatures.
The variability in environmental temperature complicates the interpre¬
tation of the effect of different nutritive levels, but nevertheless the evidence
is sufficient to conclude that the most potent factor in determining the mag¬
nitude of the insensible perspiration is the general nutritive plane or
metabolic level. In other words, the insensible loss probably is closely cor¬
related with the total 24-hour metabolism of the animal at the time the
insensible loss is measured. To prove this conclusion, however, 24-hour
metabolism experiments should be made simultaneously with the measure¬
ments of insensible perspiration. Such simultaneous measurements were
unfortunately not made. In the 3-day metabolism experiments which were
made, it was possible to determine the insensible perspiration only on the
3-day basis, and the difficulties of collecting urine and feces in a chamber
at that time not specially provided with feces ducts were such as to preclude
accurate measurements of weights of feces for such computation. It is
believed, however, that the evidence is sufficiently striking to make it incum¬
bent upon all workers who are studying large animals in respiration cham¬
bers permitting 24-hour experimental periods to lay special emphasis upon
collecting the data for computing the insensible loss. Changes in body-
weight from day to day during fasting are only a very crude index of the
change in body substance. The insensible loss, on the other hand, is more
closely correlated with the nutritive plane and, in all probability, when care¬
fully measured, bears a close relationship to the actual loss of tissue through
metabolism.
It is not mere coincidence that the daily insensible loss of these steers was
largest when they were on heavy rations. Thus, our detailed data show
that when steer C was receiving an average daily ration of 8 kg. of hay
and 1.36 kg. of meal, his insensible perspiration was on the average 9 kg.
During fasting this fell to an average of about 2.5 kg. Subsequently, when
he was given 7 kg. of hay and 6 kg. of meal, his insensible perspiration
increased to 16 kg. on the average. Even in the case of the small animals,
E and F, when they were receiving an average ration of 5 kg. of hay and
0.7 kg. of meal, the daily insensible loss ranged not far from 7 to 8 kg.
When the ration was reduced to one-half, the loss immediately fell to not
DRINKING-WATER
75
far from 3.5 kg. During the actual fasting experiments this loss fell still
further, and with the resumption of feeding increased.
The evidence, therefore, although admittedly complicated by the factor
of environmental temperature, strongly suggests a close correlation between
the insensible loss of these large ruminants and their nutritive plane or
24-hour metabolism. It is believed that this correlation is sufficiently close
to justify making records of the insensible loss as a part of the regular
routine in all careful metabolism studies. Indeed, it is believed that the
prediction of the total daily metabolism of steers may actually be made
with close approximation if the insensible loss, under controlled conditions
of temperature, is accurately known. The same correlation between the
insensible loss and the metabolic activity of humans has been frequently
noticed at the Nutrition Laboratory, and its experiments on this point have
recently been reported.0
A series of measurements of the insensible loss, made on animals at vary¬
ing nutritive planes, but at a uniform temperature to rule out the disturbing
factor of environmental temperature, is most essential. Apparently with
ruminants the effect of environmental temperature upon the insensible loss
may be much greater than with humans. With humans the insensible loss
may be considered as coming from two sources, from the lungs and from
the skin. The loss from the skin is seemingly unaffected by ordinary
changes of temperature (up to 25° C.), wind velocity, and air movement.
The loss from the lungs is in large part determined by the carbon-dioxide
production in the body, i. e., the metabolism. Indeed, so closely has this
relationship been established with humans that the measurement of the
insensible perspiration has been used as an index of the total metabolism.
Undoubtedly any factor affecting total metabolism, such as activity and
particularly the nutritive plane, and possibly the environmental tempera¬
ture, will alter the insensible loss.
DRINKING-WATER
When animals are completely deprived of food and water, the processes
of metabolism in which katabolism predominates can be studied in their
simplest terms. With the current belief that water plays an insignificant
role in metabolism, it seems at first sight immaterial whether water is with¬
held or not. Some species of animals, namely, the carnivora, and particu¬
larly the dog, can live for an incredibly long time without water and food.
Thus, Awrorow’s dogs withstood fasting, without water, for 44 or more
days.6 But the fasting metabolism of the dog involves the disintegration
of protein and muscle to such a large extent that sufficient water is released
for physiological purposes. Experience with other animals, however, has
shown that the withdrawal of water hastens the approach of severe distress
and finally death. For experimental purposes in the laboratory, therefore,
usually food alone is withheld. Indeed, in all the fasting experiments made
by the Nutrition Laboratory or by its cooperative investigators, this pro¬
cedure has been followed. Thus, the man who fasted for 31 days received
0 Benedict and Root, Arch. Intern. Med., 1926, 38, p. 1.
b Awrorow, Metabolism and energy production of the organism during complete fasting. Dis¬
sertation, St. Petersburg, 1900. (In Russian.)
76
METABOLISM OF THE FASTING STEER
from 750 to 900 c. c. of distilled water per day,3 and geese which fasted for
30 days or more were invariably allowed to drink water as desired.
The consumption of large amounts of water by ruminants, especially when
they are fed in the barn, is a natural consequence of their eating large
amounts of highly desiccated feed, such as hay and grain. When animals
are on pasture, the succulent grass furnishes of itself a large amount of
water, but even this source of supply is usually supplemented by drafts of
water from time to time. The consumption of water has commonly been
considered as being determined to great extent by the amount of food eaten.
Kellner* 6 assumes that for each kilogram of dry matter in feed about 4 kg.
Table 18. — Daily water consumption prior to and during 2-day fasts, steers C and Dl
Steer and dates of fasts (1923)
Days before fast
Days fasting
3
2
1
1
2
3
Steer C:
kg.
kg.
kg.
kg.
kg.
kg.
Jan. 3 to 6 .
25.4
28.6
18.2
0.0
9.8
6.2
Jan. 15 17 .
24.4
36.0
22.6
0.0
9.4
Jan. 21 23 .
37 4
33.4
29.8
0.0
10 4
Jan. 28 30 .
37.0
26.6
28.2
0.0
9.4
Feb. 5 7 .
21 6
27.0
25.8
0.0
9.0
Feb. 11 13 .
30 4
26.8
18.6
0 0
10.6
Feb. 18 20 .
18.4
21.6
27.6
0.0
9.6
Mar. 1 3 .
20.6
30.0
23.8
0.0
10.4
Mar. 8 10 .
21 4
23.2
23.8
0 0
10 0
Mar. 15 17 .
28.0
22.2
26.6
0.0
9.8
Mar. 22 24 .
25.8
25.0
26.4
0.0
12.4
Steer D:
Jan. 9 to 12 .
24.4
*0.0
35.4
0.0
11.4
7.2
Jan. 17 19 .
28.0
22.6
30.0
0 0
11 4
Jan. 25 27 .
33.2
16.6
29.4
0.0
9.4
Feb. 1 3 .
25.4
28.6
34.2
0.0
10.2
Feb. 8 10 .
24.0
16.8
19.6
0.0
8.4
Feb. 14 16 .
32.0
22.6
21.6
0.0
0.0
Feb. 22 24 .
21.4
17.2
32.8
0.0
0 0
Mar. 5 7 .
24.0
26.4
25.4
0 0
0 0
Mar. 13 15 .
18.6
28.4
20.8
0.0
11.6
Mar. 20 22 .
25.0
25.8
27.0
0.0
11.2
‘The first day of fasting began at 2 p. m., the last feed having been given between 7 and 8
a. m. of that day. The water was drunk at 2 p. m.t at the beginning of each day.
J Steer fasted for standard metabolism experiment, but experiment was not made.
of water will be needed when animals are on full ration. In the study of
undernutrition in steers it was found that more nearly 2.5 or 3 kg. of water
were consumed per kilogram of dry matter in feed, when the animals were
on a submaintenance ration consisting exclusively of hay.c When no food
is given to these large ruminants, it is not impossible to conceive that no
water would be necessary and that, since the disintegration of flesh would
give enough water to carry off the waste products, the animals wrould act
much like dogs, which withstand the complete withdrawal of food and water
° Benedict, Carnegie Inst. Wash. Pub. No. 203, 1915, p. 84.
6 Kellner, Die Ernahrung der landwirtschaftlichen Nutztiere, 9th ed., Berlin, 1920, p. 185.
e Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 114.
DRINKING-WATER
77
for long periods. In view of the uncertainty as to the water needs of fasting
steers, however, it seemed best not to attempt to control the amount of
water consumed, or, indeed, to withhold water entirely, but to permit the
animals to drink voluntarily each day.
The irregularity in the water consumption of animals, particularly during
fasting, made it desirable to secure weights of the water actually consumed.
For this reason the animal was weighed immediately before and after drink¬
ing and the tub of water was likewise weighed. The time of drinking and
the temperature of the water were both recorded, as it is now being recog¬
nized more clearly that the introduction of very cold water, particularly in
large quantities, into an animal’s alimentary tract makes heavy demands
upon its store of heat and undoubtedly profoundly inhibits the activity of
the alimentary tract. In most of these fasts precautions were taken to have
the temperature of the water not far from 15° to 20° C., for in much of
our previous work on submaintenance feeding the water was extremely
cold, at times being but 1 or 2 degrees above 0° C.°
In studying fasting conditions it would be advantageous to know exactly
the salt-content of the drinking-water. This was not determined. The
water used was obtained from the university water system, supplied by a
deep well. It was frequently analyzed and found to be of a high degree of
purity. Theoretically, of course, it would have been better to have given
the animals only distilled water, as was done in the long study of the fasting
man made by the Nutrition Laboratory.* 6
Records of the water consumed by the steers prior to and during the
series of 2-day fasts in 1923 are given in Table 18 and similar records for
the longer fasts are given in Table 19.
The picture of the water consumption on the three days with feed prior
to the short fasts in 1923 gives a reasonably close indication of the normal
water consumption of these animals when living at an essentially uniform
nutritive plane, upon a constant ration. Thus, during the feeding-periods
from January to April 1923 the animals received daily 9 kg. of hay and 2
kg. of a meal mixture made up of equal parts, by weight, of corn meal,
linseed meal, and wheat bran. On this feed the consumption of water was
usually reasonably constant, amounting to not far from 20 to 25 kg. per
day. There is a marked exception in the case of steer D on the second day
before the fast of January 9 to 12, 1923. On this day the afternoon ration
of hay and meal had been withheld, as it was planned to carry out an
experiment in the respiration chamber the next morning. No experiment
was made, however. At 2 p. m. on this day steer D consumed no water. A
possible explanation for this will be given later (see p. 79).
Prior to the longer fasts of 5 to 14 days, the animals were on varying
nutritive planes and hence drank varying amounts of water and consumed
varying amounts of feed before the fasts. This fact must be taken into
consideration in interpreting the records for water consumption in the longer
fasts reported in Table 19. During the three days with feed prior to the
first four fasts the daily water consumption was usually not far from 30 to
° Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 112.
6 Benedict, Carnegie Inst. Wash. Pub. No. 203, 1915, p. 85.
78
METABOLISM OF THE FASTING STEER
1 The values given in this table represent the water drunk at the beginning of the day.
DRINKING-WATER
79
35 kg., varying somewhat with the animal, the records for both steer C and
steer D prior to the first experiment in December 1921 being somewhat
lower than any of the others. The ration prior to these fasts was an essen¬
tially maintenance ration of hay and meal. Particular attention should
be paid to the records of water consumption preceding the two fasting
experiments in March 1924, with steers C and D, and the two experiments
in February 1924, with steers E and F. In these instances all four animals
were on a distinctly submaintenance plane of nutrition and had been con¬
suming regularly less water than they had under normal conditions.
During the first day of fasting the intestinal tract of the steer, which has
been receiving maintenance rations, may still contain a large amount of
feed, which has not been entirely digested or absorbed, and which needs
water for its further hydration. The amount of water consumed on the
first day of fasting is therefore of unusual interest.
From Table 18 it will be seen that in every instance the animals drank
no water at the beginning of the first fasting day, although they were offered
water and had actually been without feed only for 6 hours. At the begin¬
ning of the second day of the fast, or the end of the first day, when no feed
had been eaten for about 30 hours, steer C drank water on every occasion
and steer D on all but three occasions. Indeed, the amount of water taken
was reasonably uniform at about 9 or 10 kg. In the one experiment with
both animals which lasted for 3 days the amount of water consumed
decreased on the third day to 6 and 7 kg., respectively.
In the longer fasts, in contradistinction to the short fasts, the animals
drank water in all but three instances at the beginning of the first day of
fasting, but there are numerous instances when no water was consumed at
the beginning of the second day of fasting. The data for water consump¬
tion during the 4-day experiments with steers E and F in 1924 and 1925
also show that the animal drank water at the beginning of the first day of
fasting, but sometimes did not drink at the beginning of the second day.
This difference in the picture presented by the short fasts and that presented
by the longer fasts and the fasts in 1924 and 1925 is probably due to several
factors. Thus, the difference in environmental temperature may have been
one cause of the difference in water consumption. The longer fasts were
made at relatively high environmental temperatures, and no attempt was
made to alter the temperature during the fast. In the short fasts, on the
contrary, the effect of both high and low environmental temperatures was
studied, the animal being occasionally subjected to a low temperature on
one day and to a much higher temperature on the very next day, or vice
versa. During the period of 2-day fasts, moreover, there were such short
intervals of feeding between the fasts that the animals probably did not
have time to recuperate entirely from one fast before another was started.
Thus, the animals were fasted approximately once a week, and there was
almost a continuous rhythm of temporary digestive disturbance, due to the
fasting, with irregularity of water intake following the fast. On the first
day or so after the fast the water consumption was low, but there was a
tendency to make up for this in the subsequent days and a high water con¬
sumption was reached after 4 or 5 days. The animal was then apt to refuse
80
METABOLISM OF THE FASTING STEER
water for a day. By pure coincidence, so far as is known, this seeming
rhythm in water consumption due to the intermittent fasting happened to
correspond with the fasting schedule.
The records for the water consumption in the experiments made in 1924
and 1925 were for steers E and F, whereas the records for the earlier fasts
were chiefly with steers C and D. In these later experiments steers E and
F were kept for 4 days continuously inside the respiration chamber. The
experimental conditions were therefore distinctly different from the stall
conditions obtaining in the series of long and short fasts, in that the animal
when inside the respiration chamber is in an atmosphere of much higher
humidity, necessitated by the lower ventilation, than he is when outside the
chamber in his stall. Consequently the data for drinking-water obtained
in the later experiments are not strictly comparable with those obtained in
the long and short fasts. It should be pointed out, however, that one would
expect that the days when the animal would not drink would be the days
when he was inside the chamber, when the humidity was high, and the
experiments in 1924 and 1925 show that this was not the case, thus sug¬
gesting that the humidity had but little effect on the loss of moisture from
the lungs and skin.
The data for the water consumption during the progress of the fast indi¬
cate that at the beginning of the second day no water was consumed in ten
instances, although as much as 10 to 13 kg. were taken in three instances.
On the third day there was a disposition to a return to water consumption.
On the fourth day steer C drank no water except in the fast in December
1921, when he took 0.4 kg. With steer D, however, the water consumption
on the fourth day of fasting varied from 0.0 to as high as 16.8 kg. On
the fifth day irregularity in the different experiments is again shown, large
amounts being sometimes taken by steer D. On the sixth day and the
following days the water intake is irregular.
No long periods of complete refusal of water are noted, save in the experi¬
ment with steer C after pasture in November 1923, when for 4 days he
drank no water, and in the experiment in March 1924, after submaintenance
feeding, when steer C drank practically no water for 10 days, if one excepts
the 0.2 kg. taken on the seventh day and the 1.4 kg. taken on the ninth day.
Steer D drank no water in the March experiment following submaintenance
feeding, except on the fourth and seventh days, when 11 kg. were taken.
Steer E, which fasted after submaintenance feeding, drank small amounts
of water during the entire fast, and steer F, also fasting on a low nutritive
plane, drank no water at all for three days.
In general, distinctly less water was consumed by both steer C and steer
D when fasting after submaintenance feeding or after pasture than when
fasting on a higher nutritive plane. Probably the large amount of water in
the succulent grass, or perhaps the possibility that the steers had been drink¬
ing just prior to leaving pasture, may have contributed a plentiful amount
of water to the animal’s organism at the time of the fasts off pasture. One
may conclude, therefore, that when steers are liberally supplied with water,
as on pasture feeding, the extra water demands of the body are relatively
small and for several days little or no water may be taken. Similarly, when
FECES
81
the animals are on a low nutritive plane and receiving a small ration of
hay, there may be a long period of time when no water or very little water
is taken. The inference is that drinking-water might be withheld from
steers during a fast, especially under conditions of submaintenance feeding
and probably after pasturage, without detriment to the animal. The long
periods of complete abstinence from water while fasting, noted especially
with steer C, are strikingly similar to experiences in fasting experiments
made with dogs. In such cases the fasting steer is practically a carnivorous
animal, subsisting upon its own flesh and not requiring any appreciable
amount of water to maintain its water-balance, for little or no water was
taken during the later stages of fasting, although water was offered every
day.
In connection with the feeding of these steers, certain definite observa¬
tions regarding the consumption of water can be recorded. When the steers
were fed both morning and evening and were offered water at 2 p. m., that
is, between the two meal times, they usually drank. If the afternoon feed
and the following morning’s feed were withheld, they usually did not drink
at 2 p. m. the next day. In those few instances when they did drink after
both feeds had been withheld, a large volume of urine was excreted during
the next 24 hours. This observation belongs, more strictly speaking, in the
section discussing the volume of urine, but is introduced here simply to
show the immediate effect of water consumption upon the output of urine
when the daily ration is withheld and there is not a corresponding supply of
dry matter of feed to absorb the water.
In none of these fasting experiments was salt given. The animals had
to rely solely upon the salt normally present in the drinking-water, an
analysis of which shows that they received a very small amount of mineral
matter from this source.
A general inspection of the detailed records secured during this research
shows that when the steers are fed hay and meal, the amount of water con¬
sumed bears a fairly close relationship to the total intake of dry matter in
the ration.
FECES
The differences in the amounts of feces excreted by the dog, by man, and
by the ruminant are in large part explained by the nature of their intestinal
tracts and particularly by the nature of their food. The residue or fill in
the intestinal tract of the ruminant is very large, amounting at times to
over 20 per cent0 of the animal’s weight, whereas the intestinal residue in
the case of man or the dog is small. Fasting dogs frequently pass no feces
for a long period. Indeed, the man who fasted at the Nutrition Laboratory
for 31 days passed no feces during the entire time.6 The large intestinal
content or ballast of the steer, however, although for some little time sub¬
ject to digestive processes and to fermentations, must be expelled, because
a large part of it is not digested by the animal organism. A study of the
feces of these fasting steers was therefore made for the purpose of securing
° Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, pp. 107 and 108.
k Benedict, Carnegie Inst. Wash. Pub. No. 203, 1915, p. 230.
82
METABOLISM OF THE FASTING STEER
information on several points: first, regarding the actual mass of feces
passed, particularly with reference to the length of the fast; second, regard¬
ing the effect of the previous ration upon this mass; and third, regarding
the chemical composition of the feces as influenced both by fasting and by
the previous ration.
Amount and Frequency of Defecations
Earlier experience with steers during undemutrition showed that exten¬
sive changes in the physical appearance of feces were not accompanied by
great alterations in the moisture-content. It is deemed permissible, there¬
fore, to discuss the fecal excretion of these fasting steers on the basis of the
fresh weight and to defer for the moment a consideration of the amount of
dry matter, which involves a knowledge of the water-content.
Due to the irregularity in the expulsion of feces by all cattle, the indi¬
vidual defecations should be weighed separately. To have an attendant
constantly at hand to collect the feces, as dropped, is perhaps the simplest
method, but it is expensive. Many experimenters have had recourse to
various types of ducts, either of rubber or oiled silk, to conduct the feces,
as passed, into reasonably air-tight containers. The small number on our
experimental staff would not permit the first of these methods of collection,
and the second method would not have much advantage over the simple
form of trap shown in a previous report,0 through which the feces drop
directly into convenient receptacles below. When the animals are fairly
well fed this latter method is ideally simple and is probably subject to no
great error, for the losses from vaporization are relatively small in propor¬
tion to the total weight of feces. On the other hand, in the weighing of the
very small amounts of feces occurring during undernutrition, and particu¬
larly during fasting, the error may be relatively larger. Any losses in weight
would, however, undoubtedly be in large part due simply to vaporization
of water, although a loss of ammonia may take place even if the feces stand
in a can for only a few hours.
The weight of fresh feces voided each day during the fasts of 5 to 14 days
and the average daily weight of feces for a week with feed preceding each
of these fasts have been tabulated in Table 20. These daily weights, how¬
ever, do not represent exact 24-hour separations. The steers did not volun¬
tarily defecate exactly at a given moment. The feces cans were removed
each day at 2 p. m., but feces might have been passed either immediately
before 2 p. m. or several hours before, and the actual time between the first
and last defecation on any given date may be longer or shorter than 24
hours. It was possible, therefore, only to approximate the true daily excre¬
tion by making the collections in 24-hour periods, and it seems inadvisable
to attempt to compute the hourly rate.
As pointed out in an earlier report,6 the fecal excretion is notably affected
by the character and the amount of the ration. The most pronounced factor
affecting the character and the amount of feces is clearly the bulk of fibrous
material, hay, rather than the amount of meal, although it is common
“Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 31.
b Ibid., pp. 121 et seq.
Table 20. — Daily excretion of fresh feces before and during fasts of 5 to H days
FECES
1 This value represents a period of collection of only 17 hours, from 2 p. m., Mar. 3, to 7 a. m.t Mar.
84
METABOLISM OF THE FASTING STEER
experience that the feeding of meal in large amounts, particularly oil meal,
has a tendency to scour animals and results in more watery and voluminous
feces.
An examination of the data obtained during the feeding-periods shows
that in general the weight of fresh feces is twice that of the ration. Thus,
during the periods of feeding in 1921 and 1922, when about 9 kg. of hay
and from 2 to 6 kg. of meal were consumed daily, 24 kg. of feces were passed
daily on the average both by steer C and by steer D. From January to
April 1923 these steers also received a maintenance ration of hay and meal,
but the food intake was disturbed by the numerous short periods of fasting
and the average weight of feces passed daily during the feeding periods was
therefore somewhat smaller than in the earlier maintenance periods. The
marked reduction in ration prior to the fast in March 1924 was instantly
reflected in a pronouncedly lower fecal expulsion. Thus, steers C and D
had been receiving daily only 4.5 kg. of hay and no meal, and as a result
the average daily amount of feces was only about 7 kg., i. e., still nearly
twice as great as the ration. A similar picture is noted with steers E and
F on a submaintenance ration of 2.5 kg. of hay and 100 gm. of meal in
February 1924, when their daily fecal excretion averaged about 4.5 kg. It
is especially worthy of note that both the younger and the older animals,
considered as duplicates or pairs, showed much the same reaction to the
ration, as exemplified by the amount of feces excreted.
There is a tendency for the daily fecal excretion of steer D to be slightly
smaller than that of steer C. Indeed, detailed records for almost every
day from November 26, 1921, through January 5, 1923, show that on the
average steer D excreted 14.81 kg. of feces per day and steer C 15.42 kg.,
although both animals received the same treatment, side by side in the
same stalls, were subjected to the same number of respiration experiments,
consumed the same amount of food, and drank the same amount of water
(21.7 kg., steer C; 21.5 kg., steer D).
In the case of all four steers, the collection of feces for the first day of
fasting began at 2 p. m., at which time the feces containers were replaced
with empty containers. The last feed prior to the fast was given in the
morning between 6 and 8 o’clock. Hence the weights of feces reported for
the first day of fasting represent a 24-hour period beginning about 6 or 8
hours after the last feed. The weights of feces reported for the first day
of the March 1924 fast, however, represent only a 17-hour period from
2 p. m. to 7 a. m., as it was decided on the second day to have the 24-hour
periods begin at 7 a. m. instead of at 2 p. m. In the two November fasts
following pasture it was not easy to determine exactly when the animals
had last eaten. The weights of feces reported for the first day of the
November 1922 fast represent a period beginning 6 hours after the steers
were brought in from pasture. In the November 1923 fast the collection of
feces did not begin until 22 hours after the steers had been brought in from
pasture, and the first 24-hour collection of feces during this fast is therefore
attributed to the second day.
On the first day of fasting there was a decrease in the amount of feces
passed, although in most instances this decrease was not pronounced. In
FECES
85
the special series of 2-day fasts during January, February, and March 1923,
the data secured regarding the excretion of feces support this view. In this
series, in which all the fasts followed maintenance feeding, approximately
19 kg. of feces were passed daily on the average during the week prior to
the fast. On the first day of fasting there was a general average decrease
to 16 kg., or a fall of 16 per cent. On the second day of fasting the average
expulsion amounted to 6 kg. The total average amount for the first two
days of fasting is therefore about 22 kg. or essentially that passed daily
during the feeding-period. This finding, that the total amount of feces
passed during the first two days of fasting is approximately equal to the
amount passed daily during the feeding-period preceding it, is also true in
the case of the longer fasts reported in Table 20, both those following main¬
tenance feeding and those following submaintenance feeding. In the case
of the fasts following pasture, obviously no records for the feeding-period
were available.
The first four long fasts of steers C and D are comparable, because they
followed an essentially maintenance ration. The fecal excretion on the first
and second days of these fasts is larger than the excretion noted in the short
fasts in 1923. Thus, both steers excreted approximately 24 kg. during the
week on feed before the fasts and on the average not far from 20 kg. of
feces on the first day of these four fasts. The average percentage decrease
on the first day, however, is practically the same as was noted in the 1923
series, i. e., 17 per cent. This relatively small average decrease of 4 kg. is
perhaps surprising, but one should recall that feed was actually eaten 8
hours prior to the collection of feces for the first fasting day. This fact,
coupled with the large ballast in the intestinal tract, minimizes any immedi¬
ate effect of fasting upon the fecal discharge.
In general, the larger amounts of feces prior to these four fasts are fol¬
lowed by larger amounts of feces on the first fasting day. In the April fast
of steer C and the June fast of steers C and D, decreases in fecal excretion
of from 4 to 8 kg. were noted on the first day, but in the other fasts the
decrease is more nearly 2 or 3 kg. With the large bulk of fecal matter in
the intestinal tract and the irregularity of defecation, it is perhaps not sur¬
prising that the fecal output on the first day is not more uniform. The
length of time intervening between the last ingestion of feed and the begin¬
ning of the first day of fasting and the amount of the last ration received
prior to the fast should also be considered in this connection. Thus, some¬
what larger amounts of meal were eaten prior to the fasts in January,
April, and June 1922 than were eaten prior to the fast in December 1921,
and in all but one instance the fecal excretion in these experiments is larger
than that noted in the December experiment. The large amount of meal
eaten prior to the fast in January 1922 did not have a pronounced effect
upon the fecal excretion either before the fast or on the first day of fasting
in the case of steer D, but in the case of steer C the amounts of feces
are somewhat larger than in the 1921 experiment, when less meal was
eaten. Before the fast in June 1922, when both steers had been receiving
about 8.5 kg. of hay and 4 kg. of meal daily, there was a distinct increase
in the average fecal output on feed and the largest amounts of feces on the
first day were noted in this fast.
86
METABOLISM OF THE FASTING STEER
After pasture the feces are much smaller in amount. In the fast in
November 1922 both steers voided only 13.5 kg. on the first day. In the
fast in November 1923 the feces were not collected until the second day,
but the average amount on the second day, 16.7 kg., is actually greater than
that observed on the first day and about three times as great as that
recorded on the second day of the 1922 fast following pasture. Irregularity
in pasture feeding makes sharp conclusions impracticable.
In the fasts following undernutrition in 1924 the decrease in feces on the
first day is small with all four animals, but likewise the initial amounts on
feed are small. The fecal discharge on the first day of fasting is, however,
very small when compared with the amounts voided in the other fasts
following maintenance rations or pasture feeding.
Inspection of the data for feces on feed and on the first two days of
fasting shows in general, therefore, that the decrease in feces on the first
day of fasting is small following maintenance feeding. After submain¬
tenance feeding the decrease is small and the total amount involved is like¬
wise small. In the case of steers E and F the total amount on the first day
is small, both because the fasting followed submaintenance feeding and
because the animals were small.
Because of the continually decreasing ballast and the extensive changes
in the amount of water intake during fasting, great differences in the fre¬
quency of defecation, the amount of each defecation, and the total amount
per day are to be expected. Only the total amount per day is considered
in Table 20. Records were kept, however, of the amount and time of each
defecation during all of the fasts reported in Table 20, except that in
December 1921. These records show that in the fasts following maintenance
feeding the number of defecations on the first day was fairly large, varying
from 9 to 12 defecations during the day. In the two November fasts after
pasture the defecations on the first day decreased to 5 or 6 in number. In
the fasts following submaintenance rations steers C and D voided feces at
five or six different times during the first day and steer E at four different
times. On the other hand, with steer F there were nine defecations, all
reasonably uniform in size. Aside from this one instance, however, the
number of defecations on the first day of fasting was less following pasture
or submaintenance feeding than following maintenance feeding with hay or
with hay and meal.
The frequency of defecation and the actual amount of each defecation is
best shown graphically. Accordingly, the data for the individual defeca¬
tions have been plotted for three typical fasts of steers C and D, namely,
the 14-day fast in April 1922, the 9-day fast after pasture in November
1922, and the 10-day fast after submaintenance feeding in March 1924.
(See Fig. 4.) The total daily excretions are recorded upon the chart in the
top row of figures above each curve, thus duplicating the data in Table 20
for these three fasts.
In the 14-day fast in April, which followed maintenance feeding of 9 kg.
of hay and 3 kg. of meal daily, the number of defecations and the amount
of each defecation were large with both animals on the first day. On the
second day there are fewer defecations and the total mass is much smaller.
FECES
87
The charted data for this fast show a distinctly downward trend both in the
number of defecations and the amount of each defecation until about the
seventh day. After the seventh day there are a large number of small
defecations daily. This is particularly true of steer D, whose total daily
fecal discharge on the average is actually not quite so large as is that of
steer C. On the last day of the fast, for example, steer D had 11 defecations,
practically all under 100 grams each.
6m
Fig. 4. — Individual defecations of steers C and D during fasts in April and November 1922, and
March 1924
The two curves at the bottom of the chart represent the fast3 in April 1922, which followed a
maintenance ration of 9 kg. of hay and 3 kg. of meal. The two curves in the middle are for
the November fasts, which followed pasture feeding. The two curves at the top are for the
March fasts, which followed a submaintenance ration of 4.5 kg. of hay. The figures in the
top row against each curve represent the total daily weights of fresh feces in kilograms, those
in the middle row the kilograms of dry matter in feces per day, and those in the bottom
row the grams of fecal nitrogen per day.
A relationship between the amount of water consumed per day and the
consistency and the amount of feces passed has been observed frequently,
both in our series of undemutrition and of fasting experiments. It is not
unlikely that some of the irregularities shown in Fig. 4 are due to differences
in water intake. In no instance, however, is a striking effect of the water
consumption upon the mass of feces indicated on any given day. Reference
to the data for water consumption (see Table 19, p. 78) shows, for example,
that on the eleventh day of this April fast steer C passed a relatively large
amount of feces, 2.6 kg., and drank 5.2 kg. of water. Steer D, on the other
hand, drank 8.4 kg. of water on the tenth day of this fast, but there was
practically no change in the weight of fresh feces.
88
METABOLISM OF THE FASTING STEER
The daily excretion is usually somewhat less than half as much on the
second day as on the first, save in the March fast after submaintenance
feeding. The total daily amount falls off fairly regularly thereafter, but
from the fifth day on the average excretion of all animals is not far from
1.5 kg. per day. Feces were passed upon every day of the fasting experi¬
ments, with the single exception of the tenth day in the March 1924 fast of
steer C, after submaintenance feeding. It is clear that the previous plane
of nutrition, particularly the submaintenance plane, affects the fecal excre¬
tion. The influence of pasture feeding is noticeable only for about 3 days,
although the amounts of feces excreted by both steers during the fast in
November 1923 were large even after the third day, indeed larger than in
most of the other fasts.
A quantitative study of either the total daily amounts of feces or, indeed,
the dry matter of feces, must take into account the fact that the defecations
of these animals are involuntary, the ballast is very large, and considerable
differences in water intake occur. Only the most general conclusions regard¬
ing the amount and rate of defecations are, therefore, justifiable, for
undoubtedly complications are introduced by the water intake, the character
of the feed (relative proportion of coarse fiber and concentrates), and the
time elapsing between the last feeding and the beginning of the collection
of feces.
It is perhaps to be regretted that no provision could be made for the sepa¬
ration of feces, particularly by the chromic oxide method of Edin.a This
seemed impracticable, and doubtless the marker would have been retained
throughout the entire fasting period. The use of a foreign substance to
mark the feces in ruminants has always been considered unsatisfactory. The
elaborate study of Ewing and Smith,* 6 who used rubber disks to indicate the
rate of passage of food residues through the steer, showed that some of the
rubbers remained in the animals for 60 days, indeed until they were
slaughtered. Hence Ewing and Smith conclude that such a method of
marking is unreliable. The gross contents' of the alimentary tract of steers
is well illustrated in their report. Thus, they find that with 6 steers, weigh¬
ing on the average 380 kg., the gross contents of the intestinal tract
varied from 36.6 to 70.8 kg.; 5 of the 6 steers had a residue of 60 kg. or
more. The percentage of dry matter in these contents varied from 6.07 to
12.92, averaging not far from 9 per cent. The authors conclude that the
time required for the ordinary ration to pass through the intestinal tract
probably varies between 72 and 84 hours, the rate of passage being largely
influenced by the nature and the quantity of the ration, the importance of
the two influencing factors being in the order named.
The picture shown by steers E and F is in accord with that of the two
large animals, if one takes into account the fact that they are smaller and
that they had been upon a submaintenance ration. It is singular, however,
that the daily weights of feces of each of these smaller steers during their
fast following submaintenance feeding should be essentially the same as
were noted with the larger animals when fasting after a submaintenance
a Edin, Nordiske Jordbrugsforskeres Forenings, Kongres i K0benhavn, July, 1921, p. 388.
6 Ewing and Smith, Journ. Agric. Research, 1917, 10, p. 55.
Fig. 5. — Feces voided by steer C on the sixth day of fasting, November 10, 1923
The rule is 15 inches (38 cm.) long
Fig. 6. — Feces voided by steer D on the fifth day of fasting, March 8, 1924
The squares are in inches, or about 2.5 cm.
FECES
89
ration. Thus, although prior to these fasts steers C and D excreted approxi¬
mately 7 kg. of feces per day and steers E and F only about 4.5 kg., during
fasting the total 24-hour excretions after the first day are much more
nearly uniform.
The data in Table 20 and in Fig. 4 indicate clearly that fasting greatly
reduces the fecal excretion, which, however, continues throughout the entire
fast, irrespective of its length. The previous plane of nutrition affects the
total daily amounts, and even after pasture the fill and fecal excretion dur¬
ing the fast remain at a relatively high level. With at least one steer the
frequency of defecation greatly increased toward the end of the fast.
Physical Characteristics of Feces
In an earlier report® attention was called to the striking differences in the
characteristics of the feces when the animals were upon submaintenance
rations and when upon full feed. In the latter instance the feces were semi¬
fluid, would not hold form, and were very bulky. When the steers were
upon submaintenance rations, their feces became much harder and more
pilular in form, resembling in many instances the feces of a horse. The
determinations of water in these feces did not show so great a difference
in the percentage of moisture as would be expected from the striking differ¬
ence in physical appearance. Indeed, a difference of only 2 or 3 per cent
in the water-content was noted. It seemed incredible that this small per¬
centage difference in water-content could be accompanied by such a great
difference in the physical configuration of the feces. In connection with the
study of fasting steers opportunity was had to confirm this observation, for
steers C, D, E, and F were at varying times upon submaintenance rations.
During their submaintenance feeding, similar changes in the physical char¬
acteristics of the feces were noted, and the chemical analyses, especially the
water determinations, show that these great changes can take place without
appreciable alterations in the water- content.
Comments of the observers regarding the physical characteristics of the
feces during the 14-day fast in April 1922 are typical of the physical char¬
acteristics of the feces in practically all of the fasts. The feces at the begin¬
ning of the fast in April 1922 were soft and very plastic, as would normally
be expected from a ration containing 3 kg. of a meal mixture having a rela¬
tively large proportion of linseed meal and bran. As the amount of feces
decreased during the progress of the fast, the feces became visibly firmer,
taking on a dry, pilular form by the fifth day. By the eighth day the con¬
sistency of the feces became more variable, some passages being firm and
fibrous in appearance, and others, especially those passed in the respiration
chamber, being soft. This latter condition was more marked with steer C.
Variability in the physical consistency of the feces, especially in the latter
periods of fasting, is noted likewise in the water-content of the feces, strik¬
ingly high percentages of water being found. (See Table 21, p. 90.) The
extremely dry, pilular form which fasting feces may assume is excellently
illustrated in Figs. 5 and 6, which show the feces of steer C on November
10, 1923, the sixth day of the fast, and of steer D on March 8, 1924, the fifth
day of the fast following submaintenance feeding.
“Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 125.
Table 21. — Percentage of dry matter in feces during fasts of 5 to 14 days
90
METABOLISM OF THE FASTING STEER
1 There were no defecations between 7 a. m., Mar. 12, and 7 a. m., Mar. 13, but 0.62 kg. of feces were passed in the respiration chamber between
7h 10m and 10h 25m a. m., Mar. 13, before the steer was fed. The dry matter in these feces was 20.6 p. ct.
FECES
91
Another pronounced characteristic of the feces during the fasting experi¬
ments was an exceedingly offensive odor, which frequently was noticed
toward the end of the fast.
Chemical Composition of Feces
The difficulty of avoiding loss of moisture and frequently of nitrogen
(ammonia) in the drying of feces made it necessary to determine the
nitrogen-content directly in fresh feces. The water-content was determined
by subjecting a sample of approximately 10 gm. of fresh feces to the usual
process of drying. With but few exceptions these two determinations were
made on each day’s collection of feces during the long fasts and on a com¬
posite sample of the feces passed during the entire fasting-period, as well
as on a composite sample of feces passed during the feeding-periods just
preceding and following the fasts. No correction was made for loss of
material. Further analyses of the feces were impracticable, and the study
of the chemical composition of fasting feces is confined solely to the
analyses of the water-content and the nitrogen-content.
Dry Matter in Feces
The marked changes in the physical appearance of the feces made the
determinations of water-content especially interesting, in view of the lack
of correlation between major changes in physical appearance and changes
in water-content previously noted in the undernutrition study with steers.
The percentages of dry matter in the feces, not only for each 24-hour col¬
lection of feces during the fasting-periods, but likewise for the composite
sample during the entire fast, are given in Table 21. Unfortunately, no
daily analyses were made for the fasts in December 1921, November 1923,
and February 1924. The data for the composite samples of feces during
the feeding periods preceding and following the fasts are given in Table 22.
From these tables it can be seen that in general during the periods of
maintenance feeding about 17 to 20 per cent of dry matter was present in
the feces. During the periods of submaintenance feeding in February and
March 1924 the percentage was not profoundly altered. The composite
sample for the first fast in December 1921 likewise contained approximately
19.5 per cent of dry matter in the case of both steers. During the fasting
experiments in January, April, and June 1922, there were considerable
variations in the content of dry matter, with a distinct tendency, particu¬
larly in the 14-day fast, for the percentage of dry matter to decrease after
the fourth to the sixth day. Up to this time, however, the percentage of
dry matter is somewhat higher than during the prefasting feed period. In
the fasts in November 1922 and March 1924, on the contrary, the per¬
centage of dry matter increases considerably during the fast. It is difficult
to account for these differences in the composition of the feces. The varia¬
tions in the consumption of drinking-water seemingly explain the changes
occasionally, but by no means give a satisfactory explanation for this
anomalous situation. The matter is further complicated by reference to the
notes made by the observers of the physical consistency of the feces at the
time of passage. (See p. 89.)
92
METABOLISM OF THE FASTING STEER
In the two November fasts after pasture daily analyses were made only
for the fast in 1922, but a composite sample was analyzed for the fast in
1923. For the fast following reduced rations in March 1924, daily samples
were usually analyzed. In this fast and in that in November 1922 there is
a distinct tendency for the percentage of dry matter in the feces of both
steers to increase with the increasing length of the fast. The picture of the
daily trend in the fast in November 1923 is not available, but the one
analysis of the composite sample showed a percentage of dry matter of
from 19.5 to 20 with both animals. Since, however, the feces on the first
day of the fast in November 19221 had a very low content of dry matter,
Table 22. — Percentage of dry matter in composite
samples of feces before and after fasts of 6 to 14 days
Feed periods
Steer C
Steer D
Before fast:
Nov. 26 to Dec. 6, 1921. . . .
18.4
27.7
Dec. 22 Jan. 4,1922....
19.2
19.4
Mar. 31 Apr. 17, 1922.. . .
19.4
20.7
May 9 June 1,1922....
17.6
17.4
Feb. 26 Mar. 3,1924....
23.0
21.9
After fast:
Dec. 13 to Dec. 22, 1921 ....
19.6
19.8
Jan. 14 Feb. 2,1922....
18.7
18.4
Mar. 21 Mar. 31, 1922. . . .
18.6
19.3
May 1 May 9, 1922 ....
15.8
18.8
Mar. 12 Mar. 13, 1924....
Mar. 13 Mar. 14, 1924. . . .
23.7
18.5
Steer E
Steer F
Before fast:
Jan. 28 to Feb. 12,1924....
21.9
21.1
After fast:
Feb. 18 to Feb. 19, 1924. . . .
21.5
18.3
Feb. 19 Feb. 20, 1924... .
20.1
17.6
16.5 and 16.7 per cent, respectively, and since the first day’s defecation rep¬
resents a large part of the total amount excreted during fasting, the low
values found for the fast in November 1923 are what would be expected.
The percentage of dry matter on the first day of the November 1922 fast,
after the animals came in from pasture, is, however, very low as compared
with that of the first day of the March 1924 fast, prior to which the animals
had been subsisting upon a submaintenance ration of hay.
The difficulties of sampling feces and securing representative portions for
analysis, the well-known loss during drying, and the general difficulty of
securing anhydrous conditions in organic products make determinations of
water in a substance such as the feces of ruminants at best somewhat
uncertain. The extraordinarily high percentages of water noted in Table 21
in some of the feces, especially toward the end of the long fasts, has puzzled
us greatly. Careful scrutiny of the raw data, checking of the computations,
and a comparison with the ocular observations of the attending assistants
confirm in large measure these low percentages of water-free matter. To
explain them is not easy. It is evident that the finding of Grouven that the
Table 23. — Daily weight of dry matter in feces before and during fasts of 5 to 1 4 days
FECES
93
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94
METABOLISM OF THE FASTING STEER
fill became more watery as the fast progressed may in part explain these
feces with large percentages of water. Undoubtedly the feeding conditions
prior to the fasts affected somewhat the composition of the feces, especially
at the beginning of the fasts. In the latter part of the fasts, at the point
when about 70 per cent of the dry matter of fill has been washed out through
the feces, the moisture-content of the feces seems to be more rapidly affected
by water intake in quantity above the physiological daily needs. It is con¬
ceivable that in the 14-day fasts the fill was rather liquid and contained a
relatively small amount of dry matter of fibrous character. Hence there
could not be much absorption of nutritive material, and consequently there
was less absorption of water. Under these conditions the addition of water
by drinking leaves the body partly in the feces, as there is less absorption.
From the data it is clear that after the first 3 to 5 days the amount of dry
matter defecated daily is more uniform than the total amount of feces, the
greater variations corresponding in almost every instance to variations in
the water intake. Further studies of the nature of the fill and feces voided
during fasting, and particularly analyses of the fill in different parts of the
alimentary tract at the end of long fasts, are imperative for a thorough
understanding of the relationship between fill, water-content of fill, and
excreted feces, as associated with the various stages of prolonged fasting.
It is perhaps more important to consider the actual amount of dry matter
in feces as a measure of the loss of material to the animal during the fasting
period. The weight of the dry matter in feces per day has, therefore, been
recorded in Table 23 and in Fig. 4. Except for the fasts after submain¬
tenance feeding, not far from 3.5 kg. of dry matter were excreted on the
first day by the two large steers. This amount rapidly decreases to about
1 kg. on the third day, and to 0.5 kg. on the fifth day. Even on the last
4 days of the 14-day fast approximately 200 grams of dry matter were
excreted on the average per day. In the fasts after submaintenance feeding
the amount of dry matter on the first day was much smaller, being nearer
1.2 kg., but by the fifth day the excretion has become 0.5 kg., as in the other
fasts. With the two small steers studied after submaintenance feeding, the
dry matter was not determined for each day of the fast.
The analyses for steers C and D show that there is a continued loss of
dry matter of ballast throughout the entire fast. In this respect the fecal
excretion of the ruminant is strikingly different from that of the omnivorous
man or dog, due without doubt to the large intestinal ballast.
Inasmuch as these animals were receiving no food, the total loss of dry
matter during the various lengths of the fasts is important *as giving an
indication of at least the minimum amount of fill existing at the beginning
of the experiment. For this purpose the total dry matter excreted in the
feces by these animals has been recorded in Table 24, together with data
regarding the daily amount of feed consumed during the week prior to the
fast. In the longest fast of 14 days, about 10 kg. of dry matter were lost by
both animals on a feed-level of 9 kg. of hay and 3 kg. of meal. If it is
assumed that the dry matter in the feces of the steer represents on the
average 20 per cent of the total fill, it can be seen that at the start of this
14-day fast the fill must have amounted to at least 50 kg. The evidence,
FECES
95
however, is strikingly to the effect that the fill contains more than 80 per
cent of water. The estimate of 50 kg., therefore, undoubtedly represents a
minimum amount. Furthermore, it is clear that this estimate does not
include all the fecal material, for some must have been retained.®
Table 24. — Total weight of dry matter excreted in feces during fasts of 5 to 14 days
Dates of fasts
Daily ration
prior to fast
Steer C
Steer D
Days
fast¬
ing
Total
dry
matter
Days
fast¬
ing
Total
dry
matter
Hay
Meal
kg.
kg.
kg.
kg.
Dec.
6 to 13, 1921 .
8.5
1.4
7
8.02
7
6.99
Jan.
4
14, 1922 .
7.0
6.0
10
8.08
10
8.18
Apr.
17
May 1, 1922 .
9.0
3.0
14
10.25
14
9.95
June
1
7, 1922 .
8.5
4.0
6
8.36
5
6.98
Nov.
6
16, 1922 .
Pasture
9
6.52
8
6.18
Nov.
4
10, 1923 .
Pasture
5
7.01
5
6.23
Mar.
3
13, 1924 .
4.5
10
4.56
9
5.05
In the 6-day fast in June 1922, steer C excreted 8.36 kg. of dry matter,
or within 2 kg. of that excreted in 14 days. The ration prior to this fast
contained 0.5 kg. less of hay and 1 kg. more of meal. After pasture, smaller
amounts of dry matter were excreted and, as is to be expected, even in the
10-day fast following submaintenance feeding a total of but 4.5 and 5 kg.
of dry matter were excreted by steers C and D, respectively. In this case
the feed-level was 4.5 kg. of hay.
It is perhaps to be regretted that the animals were not slaughtered at the
end of the fasting-periods, particularly at the end of the long fasts, in order
to note the contents of the intestinal tract. Indeed, a study of the contents
of the intestinal tract after various rations is imperatively needed, not only
to give information regarding the physiological processes of digestion, but
likewise regarding the proportion of fill to body-weight on varying rations.
Nitrogen in Feces
The nitrogen excretion in the feces is of greatest significance in consider¬
ing the nitrogen loss during fasting and in establishing a nitrogen balance,
in which the nitrogen in the urine enters particularly into the calculation.
It is important, however, to note also the rate of nitrogen loss in the fasting
feces (presumably in large part in the form of undigested material) and the
effect of the previous ration of hay and meal or of green grass. In Table 25,
therefore, are recorded the average daily weights of nitrogen excreted in
feces for the feed periods prior to the fast, and the total fecal nitrogen for
° Colin (Traite de Physiologie Comparee des Animaux, 3d ed., Paris, 1888, 2, p. 693) found
that a horse, which was slaughtered after having fasted for 30 days, had 26.2 kg. of fill in the
intestinal tract. This finding emphasizes the necessity for bearing in mind in the study of these
large ruminants that one has to deal continually with a possible ever-present source of energy.
Although no analysis of the intestinal contents was reported by Colin, it is probable that the
dry matter consisted for the most part not only of indigestible material, but of material not easily
attacked by the normal intestinal flora of the horse.
Table 25. — Daily nitrogen excretion in feces before and during fasts of 5 to 14 days
METABOLISM OF THE FASTING STEER
1 Average daily fecal nitrogen for from 1 to 2 weeks on feed before fast. For exact dates represented see Table 22, p. 92.
2 No nitrogen analysis was made for the sixth day of this fast. The analysis of the composite sample for June 1 to 7 gave 0.292 p. ct. nitrogen in the
fresh feces. On the basis of this analysis the total fecal nitrogen for 6 days would be 145.8 gm., and the fecal nitrogen on the sixth day would be 8.8 gm.
URINE
97
each day of the fasts. The daily weights of fecal nitrogen are also given
in Fig. 4 for the fasts in April and November 1922 and March 1924. Special
use of these data is made in considering the total nitrogen loss. (See p. 127.)
The only data available for comparison regarding the fecal excretion of
large ruminants during fasting are those reported by Grouven in 1864.° The
daily weights of feces and the contents of dry matter and nitrogen were
determined by him in the case of a black ox which fasted for 8 days, a
brown ox which fasted for 5 days, and ox I, which fasted for 4 days. The
findings with steers C, D, E, and F completely confirm those of Grouven.
Thus, Grouven noted that the daily weights of feces decreased as the fast
prpgressed, the largest amounts occurring on the first day and some feces
being excreted every day throughout the fast. Increasing percentages of
dry matter and nitrogen were also noted by him in the case of the black
and the brown oxen, but in the case of ox I there was practically no change
in the percentage of nitrogen. The black and the brown oxen were slaugh¬
tered after their fasts, and it was found that the contents of the intestinal
tract represented 10.7 per cent and 14.2 per cent, respectively, of the total
live weight of the animal.
URINE
The urine is the path for the loss of considerable volumes of water and
the chief outlet for metabolized nitrogen. Indeed, in nutrition experiments
with steers, the nitrogen output in the urine has, for many years, been
accepted as the best measure of protein metabolism. In connection with
these fasting experiments, therefore, the amount, frequency, and regularity
of urination was studied and an extensive chemical analysis was made of
the constituents of the urine during fasting.
The collection of the urine for such studies requires special technique.
With steers the technique is relatively simple, the essential requirements
being the confinement of the animal in a stall and the use of a harness and
a urine funnel, which is connected with previously weighed bottles in the
basement beneath the stall. With cows the technique is more complicated.
Not infrequently urine and feces are collected together, and since the urine
contains metabolized nitrogen and the feces contain undigested nitrogen, the
combined collection of urine and feces introduces an element of uncertainty
into the determination of the nitrogen actually derived from body-tissue.
During this research on fasting the steers wore urine funnels for months at
a time, and doubtless some of the experiments represent the longest con¬
tinuous periods in which stall feeding, metabolism experiments, and con¬
tinuous collection of urine have been carried out.
In the collection of the urine during the fasting periods attention was
given to the volume and the time of each individual urination, as well as
to the total volume passed daily. Ordinarily the data regarding the amount
of urine excreted are reported on the 24-hour basis. For a general study of
the volume of urine, 24-hour collections of urine are perhaps sufficiently
satisfactory. Since the steer will not voluntarily empty the bladder exactly
at the end of each 24 hours, however, the apportionment of the urinations
° Grouven, loc. cit., pp. 127 et seq.
98
METABOLISM OF THE FASTING STEER
during the 24-hour periods presents difficulty at times. Thus, if urine is
passed a few minutes after 2 p. m., the beginning of the 24-hour period in
most of our fasting experiments, it is a question whether this amount should
be credited to the previous 24-hour period. Special discussion of this point
will be given subsequently (see p. 110) . In most instances the exact time of
each voiding was recorded, so that it is possible to ascribe a certain urinary
volume to a definite period of time since the last urination. These time
records make possible a closer approximation to the true amounts of urine
voided in any given time and are of special value in the more accurate
chemical analysis of the urine and particularly in studying the influence of
prolonged fasting and the differences between animals. Indeed, many of
the data regarding the chemical constituents of the urine have been reported
on the hourly basis (see Tables 28 and 29, pp. 108 to 111).
The physical properties of the urine, its color, odor, and density, were
frequently determined. A study was also made during some of the later
fasting periods of the reaction of each urination to litmus paper, in order
to determine at what time in the course of the fast the normal alkaline urine
of the steer becomes the acid urine of the carnivorous animal. The pro¬
cedure was as follows: Twice daily the urine funnel and the urine hose were
washed out with distilled water. At each urination several pieces of litmus
Table 26. — Daily excretion of urine during 2-day fasts and three days with feed prior to fasts,
steers C and D
Steer and dates
of fasts
(1923)
Days before fast
Days fasting
3
2
1
1
2
Steer C:
kg.
° C.
kg.
°C.
kg.
° C.
kg.
0 C.
kg.
0 C.
Jan. 3 to 6 . . .
4.92
15
5.34
12
5.47
11
2.67
6
>3.30
9
Jan. 15 17...
5.16
25
4.88
20
5.86
26
4.27
29
3.06
12
Jan. 21 23 . . .
2.83
28
3.92
27
6.54
29
3.74
28
2.88
7
Jan. 28 30. . .
3.32
11
4.87
26
6.19
11
5.28
8
2.20
25
Feb. 5 7 ...
5.56
12
5.16
4
4.71
7
4.81
6
2.80
5
Feb. 11 13. . .
3.18
8
4.08
10
5.42
11
5.16
8
3.20
8
Feb. 18 20. . .
4.16
- 3
5.20
3
4.90
7
4^86
4
3.50
0
Mar. 1 3 . . .
5.18
12
6.06
13
5.38
11
5.06
12
3.42
14
Mar. 8 10. . .
3.18
4
4.68
3
4.84
4
4.04
4
2.17
6
Mar. 15 17. . .
4.18
10
4.08
7
3.90
5
4.58
8
2.77
8
Mar. 22 24...
3.68
19
4.36
24
4.40
27
4.18
26
2.70
22
Steer D:
Jan. 9 to 12 . . .
4.84
8
2 5.96
11
3.68
12
3.97
13
12.88
9
Jan. 17 19. . .
3.82
26
4.77
29
5.18
12
5.21
12
2.27
28
Jan. 25 27. . .
5.12
7
5.55
13
4.75
11
4.09
11
3.08
26
Feb. 1 3. . .
3.47
25
4.26
28
4.09
23
4.17
23
2.25
12
Feb. 8 10...
4.17
6
4.57
5
3.74
7
3.97
8
2.18
10
Feb. 14 16...
3.60
8
4.41
8
6.12
6
5.04
- 3
2.58
- 3
Feb. 22 24 . . .
4.72
0
5.43
6
5.42
6
5.50
2
2.08
- 2
Mar. 5 7 . . .
4.56
14
5.62
11
4.84
5
4.58
4
2.17
3
Mar. 13 15...
5.29
5
4.02
7
3.40
10
4.00
7
2.28
5
Mar. 20 22 . . .
6.12
7
4.93
24
4.76
19
2.91
24
2.04
27
1 Steers C and D fasted a third day on Jan. 5-6 and Jan. 11-12, respectively; steer C voided
2.66 kg. of urine and steer D 5.16 kg.
1 Steer went 24 hours without food preparatory to a proposed respiration experiment, but
the experiment was not made.
URINE
99
paper were held under the end of the hose, enough urine always being left
in the elbow of the hose after urination to wet the papers thoroughly. The
hose was well drained after each litmus test. As a precaution against change
in urine, the test should be made as soon as possible after the urine is passed.
Influence of Fasting on Amounts of Urine Excreted
Amounts per 24 Hours and per Hour
The amounts of urine excreted daily during the series of 2-day and 3-day
fasts in 1923 and during 3 days just previous to each of these fasts are
recorded in Table 26, together with the average stall temperature during
the same 24 hours. It will be recalled that in the feeding-periods between
these intermittent fasts the animals received a maintenance ration of 9 kg.
of hay and 2 kg. of meal daily. The nutritive level was therefore held fairly
constant. The most striking feature of this table is the distinctly lower
amounts of urine excreted on the second day of fasting. On the first day
occasional decreases in the 24-hour weights of urine are observed, but for
the most part the amounts are essentially the same as those noted prior to
the fasting periods.® The amount of urination, furthermore, is seemingly
wholly independent of environmental temperature.
The interest centers chiefly, however, in the data for the fasts of 5 to 14
days’ duration. The daily weights of urine during these fasts and for 3 days
with feed before each of the fasts are given in Table 27. Since these fasts
followed maintenance, submaintenance, or pasture feeding, and since steers
E and F were much smaller and younger than steers C and D, variations in
the urinary excretion are naturally to be expected. Finally, it must not be
forgotten in the analysis of these data that the 24-hour weight of urine may
actually represent a period much shorter or longer than 24 hours. Obvi¬
ously, however, the more frequent the urination the greater the likelihood
of the 24-hour collection representing the true 24-hour excretion.
In the three days prior to fasting, steer C excreted a maximum daily
amount of 10.92 kg. of urine just preceding the fast in January 1922, and a
minimum amount of 2.22 kg. prior to the fast following submaintenance
feeding in March 1924. These extremes are not noted with steer D, the
highest 24-hour amount excreted by him being 6.71 kg. prior to the fast in
January 1922, and the lowest being 3.70 kg. prior to the March fast. In
general, as is to be expected, the weights of urine during the 3 days on the
submaintenance ration, that is, in March 1924, are considerably lower than
those during the three days preceding the other fasts. Steers E and F prior
to their fasts excreted small amounts, explainable on the two grounds that
they were smaller animals and were on submaintenance rations.
During the actual fasting periods the maximum 24-hour excretion on the
first day of the fasts following maintenance or pasture feeding was 13.03
kg., noted with steer D. The daily weights of urine have a tendency to
decrease as the fast progresses. With steer C, minimum values are usually
recorded on the fourth day, and the amounts stay reasonably constant from
° The first day of fasting begins at 2 p. m., the last feed having been given between 7 and 8 a. m.
of that day. The first feed following the fast was given during the last 3 hours of the last day
of fasting (in two cases during the last 6 hours). This refeed usually induced a relatively liberal
intake of water, which might have had an influence upon the volume of urine excreted.
100
METABOLISM OF THE FASTING STEER
there on, even when the fast extends to 14 days. With steer D the regularity
is by no means so pronounced. In the first place, as large an amount as 13
kg. was found on the first day of the January fast. Secondly, a very high
excretion of 7.65 kg. is noted on the tenth day of the fast in April 1922, and
Table 27. — Daily excretion of urine before and during fasts of 5 to 1 4 days
Steer and dates of fasts
Days before fast
Days fasting
3
2
1
1
2
3
Steer C:
kg.
O
C.
kg.
O
C.
kg.
}C.
kg.
°C.
kg.
°C.
kg.
°C.
Dec. 6 to 13, 1921 .
4.
32
9
4.22
7
5
.14
7
6.65
5
3.50
5
3.19
15
Jan. 4
14, 1922 .
6.
51
16
6.
73
16
10.92
14
9.41
20
4.46
20
3.35
20
Apr. 17
May 1, 1922. . .
4.
03
21
4.
65
17
4
.54
20
5.25
20
7.72
20
5.26
20
June 1
7, 1922 .
5.
61
24
4.
97
22
4
.71
23
7.11
23
9.98
22
4.12
23
Nov. 6
16, 1922 .
6.02
3.57
1.83
Nov. 4
10, 1923 .
6.74
4.31
Mar. 3
13, 1924 .
2.
74
13
2.
22
16
3
.74
17
1
1.91
14
2.18
16
1.23
16
Steer D:
Dec. 6
13, 1921 .
4.
42
9
4.
12
7
5
.08
7
8.59
5
2.96
5
1.49
15
Jan. 4
14, 1922 .
6.
71
16
6.
30
16
6.38
14
13.03
20
3.60
20
4.03
20
Apr. 17
May 1, 1922...
4.
88
21
4.
75
17
5
.50
20
5.71
20
6.73
20
6.98
20
June 1
6, 1922 .
5.
78
24
4.
73
22
5
.52
23
6.91
23
4.05
22
8.91
23
Nov. 6
14, 1922 .
6.30
2.93
2.82
Nov. 4
9, 1923 .
9.17
3.56
Mar. 3
12, 1924 .
3.
70
13
3.
90
16
4
.03
17
1
3.20
14
4.82
16
1.40
16
Steer E:
Feb. 12
17, 1924 .
1.
76
12
2.
04
12
1.93
13
1.34
16
5.00
15
1.14
16
Steer F:
Feb. 12
18, 1924 .
1.
37
12
1.
72
12
1
.70
13
1.40
16
1.21
15
0.91
16
Days fasting
oteer ana dates ol lasts
4
5
6
7
8
9
Steer C:
kg.
°(
n
kg.
°(
nr
kg.
°C
kg.
°C.
kg.
0 C.
kg.
°C.
Dec. 6 to 13. 1921 .
1.
97
20
2
98
18
2.67
17
1.67
20
Jan. 4
14, 1922 .
1.
68
21
2.
36
24
4.64
20
2.13
20
1.67
21
1.60
23
Apr. 17
May 1, 1922. . .
3.
16
15
2
03
20
3 84
22
2 18
22
1.92
22
2.09
23
June 1
7, 1922 .
2.
55
2.f>
3
09
27
2.40
26
Nov. 6
16, 1922 .
2.
99
2.
88
1.93
2.68
2.66
2.67
....
Nov. 4
10, 1923 .
2
70
2
91
3.32
Mar. 3
13, 1924 .
2.
54
16
0.
65
14
0.94
16
2.23
18
1.73
14
1.64
16
Steer D:
Dec. 6
to 13, 1921 .
5.
55
20
1
83
18
1 47
17
5.02
20
Jan. 4
14, 1922 .
3.
19
21
3.
19
24
3.07
20
4.33
20
1.89
21
1.36
23
Apr. 17 to May 1, 1922. . .
3.
20
15
2.
43
20
2.29
22
1.57
22
1.87
22
1.92
23
June 1
6, 1922 .
3.
01
25
7.
40
27
Nov. 6
14, 1922 .
3.
31
5.
72
3.94
.
2.11
2.02
. . . .
Nov. 4
9, 1923 .
3
23
2.
66
Mar. 3
12, 1924 .
3.
25
16
3.
15
14
1.74
16
3.35
18
2.50
14
1.25
16
Steer E:
Feb. 12 to 17. 1924 .
5 27
15
Steer F:
Feb. 12 to 18. 1924 .
1.
09
15
1.
23
14
1 This value represents a period of only 17 hours, from 2 p. m. to 7 a. m.
URINE
101
Table 27. — Daily excretion of urine before and during fasts of 5 to 1 4 days — Continued
Steer and dates of fasts
Days fasting
10
11
12
13
14
Steer C:
Jan. 4 to 14, 1922 .
kg.
1.86
2.12
2.23
2.47
7.65
° C.
23
20
16
23
20
kg.
° C.
kg.
0 C.
kg.
° C.
kg.
° C.
Apr. 17 May 1, 1922 .
Mar. 3 13, 1924 .
4.63
22
2.01
21
1.61
21
2.35
21
Steer D:
Jan. 4 14, 1922 .
Apr. 17 May 1, 1922 .
2.32
22
3.81
21
5.68
21
1.90
21
an extremely low amount of 1.49 kg. on the third day of the fast in Decem¬
ber 1921. This animal is characterized, therefore, by a much greater irregu¬
larity in the excretion of urine. In the fasts following pasture, when the
body was full of a succulent feed, the results are not strikingly different
from those noted in the fasts following maintenance feeding. But in the
fasts following submaintenance feeding in March 1924 a much lower level
of excretion was noted throughout practically the entire fasting period with
both animals. This finding is in full conformity with the decreased volumes
observed prior to this fast.
The hourly excretion of urine has likewise been computed for these fasts
of 5 to 14 days, and the data have been recorded in Tables 28 and 29
(pp. 108 to 111), from which it can be seen that the volume of urine excreted
per hour during fasting undergoes enormous changes. The largest hourly
excretion was noted with both steers on the same date, January 4-5, 1922,
being 384 c. c. in the case of steer C and 535 c. c. in the case of steer D.
The lowest values occur, as perhaps is to be expected, during the fasts in
March 1924, following submaintenance feeding, when the hourly excretion
of steer C was as low as 52 c. c. on March 12-13, and that of steer D was
as low as 46 c. c. on March 5-6. With steers E and F in their fasts follow¬
ing submaintenance rations the hourly values likewise vary considerably.
A careful analysis of this decrease is possible only when the amounts of
drinking-water consumed are taken into consideration. In general, when
the steer is on submaintenance rations, the water intake is smaller and the
volume of urine is naturally considerably smaller.
The Frequency and Amount of Individual Urinations During Fasting
A study of the influence of fasting and the amount of drinking-water
upon the frequency of urination and the volume of each individual urination
was possible in all of the fasts of 5 to 14 days. The 14-day fast in April
1922, after maintenance feeding, the fast after pasture feeding in Novem¬
ber 1922, and the fast following submaintenance feeding in March 1924,
have been selected as illustrations for this study. These three represent
typical fasts under the varying feed conditions, the fast in April following
maintenance rations being typical of the larger number of the fasts. The
pertinent data have been charted in Fig. 7. The curves show graphically
102
METABOLISM OF THE FASTING STEER
the times of urination and the actual amounts involved. The figures in the
upper row above each curve represent the total weights of drinking-water
during the 24-hour periods and the figures in the lower row the total weights
of urine.
Gfn*.
O
Fig. 7. — Individual urinations of steers C and D during fasts in April and November 1922 and
March 1924
The two curves at the bottom of the chart represent the fasts in April 1922, which followed
maintenance feeding. Those in the center are for the fasts in November 1922, following
pasture feeding, and the two at the top are for the fasts in March 1924, following submain¬
tenance feeding. The figures in the upper row above each curve represent the amounts of
drinking-water (in kilograms) taken in every case at the beginning of the 24-hour period. The
figures in the lower row represent the total kilograms of urine voided during the 24-hour
periods.
The frequency of urination varied considerably with steers C and D. In
general, steer D urinated more frequently throughout the day than did
steer C, and the total volumes were somewhat different. Thus, the total
amount of urine excreted by steer C in the 14-day fast was 46.17 kg. and
by steer D was 54.06 kg. On those days when peaks in the curve occur,
showing large volumes of urine, one finds a correlation with water intake
only rarely. Thus, in the March fast, at the beginning of the seventh day,
URINE
103
when steer D drank 11.2 kg. of water, there was but a small increase in the
24-hour amount of urine excreted. On the two following days, when he
drank no water, the total amount of urine decreased, to be sure, but not at
all in proportion to the decrease in the water intake. On the other hand,
with steer D, on the fifth day of the fast in November 1922, after pasture,
an intake of water of 24.4 kg. is followed by a very large urination. On
the whole, however, there is no distinct evidence of a pronounced relationship
between water intake and volume of urine.
The maximum individual urinations occurred with steer D. In the fast
following pasture 3,048 grams were voided on the fifth day and on the second
and third days of the April fast 3,122 and 3,151 grams, respectively, were
voided. Very small amounts were also frequently passed by steer D. Thus,
as early as on the seventh day of the April fast, an amount less than 100
grams was passed, and on three subsequent days in this same fast amounts
under 100 grams were also passed. With steer C on the first day of the
April fast a small voiding of 99 grams occurred. Large changes in the con¬
tent of the bladder needed to stimulate voiding thus seem possible, even
under these restricted conditions. A possible explanation of the variability
in the individual urinations might be the temperature to which the animals
were exposed. (See the records of stall temperatures in Table 27, p. 100.) A
careful examination of the records, however, shows no correlation between
the two factors. Usually both animals were essentially at the same tem¬
perature, not far from 15° to 20° C., the entire time. A study of the influ¬
ence of environmental temperature upon the urinary volume would be more
significant, if made on days when the steer was receiving a constant ration,
prior to any fasting. Our evidence is not complete for this purpose, but, so
far as it goes, there is nothing to indicate any relationship between the
environmental temperature and the weight of urine.
Relation Between Volume and Dry Matter op Urine
The necessity for the addition of a preservative to the urines of these
steers and the length of time that the urines had to be stored made late deter¬
minations of the specific gravity or total solids unsatisfactory, and hence our
evidence on the relation between the volume and the dry matter of urine is
somewhat uncertain. From our observations in the research on undernutri¬
tion in steers it was clear that the volumes of urine, as was the case with
the urines of these fasting steers, were not profoundly affected by variations
in the amount of nitrogen in the urine, and surprisingly little affected by
relatively large changes in the amount of drinking-water consumed.
Physical Properties of the Urine
In general, during normal feeding, such as usually preceded a fast, the
urine was of a dilute yellowish-brown color, tending towards opaqueness in
proportion to the relative daily amount voided. Thus, when the amount
was extraordinarily large, the urine, because diluted, was lighter colored
than when the amount was unusually small and concentrated. As the fast
progressed and less water was consumed by the animal, the volume of urine
usually decreased and the color became darker, very small volumes often
being almost black in appearance. The darker the color of the urine the
104
METABOLISM OF THE FASTING STEER
more intense and offensive became the odor, probably because the urine was
voided at longer intervals and the decomposition in the bladder was further
advanced before the urine was voided. (See p. 121.)
Chemistry of the Urine
The chemical analysis of the urine, particularly with reference to the
various nitrogenous ingredients and the apportionment of the total nitrogen
among the various compounds, has proved of great physiological interest
and of inestimable chemical value in the case of humans. The possibility
of studying the urinary output of a large ruminant during fasting and com¬
paring the results with analyses of the characteristically different urines
prior to fasting made such a study an important part of our program. Dr.
Thorne M. Carpenter, of the Nutrition Laboratory, has undertaken the
analysis of such samples of urine as could be secured from our fasting
steers, and the following discussion is for the most part based upon a detailed
report which he is soon to publish. Preliminary communications on this
subject have already been made by Dr. Carpenter.®
Urine Analyses by Other Investigators
The many characteristics of the urine of herbivora obviously different
from the characteristics of human urine, such as the high alkaline reaction,
the presence of carbonates, and differences in color and odor, would naturally
suggest that the urine of herbivora is a physiological fluid of vastly different
chemical nature from that excreted by humans. That this problem has
already interested research workers is evidenced by the fact that as far
back as 1864 Grouven6 devoted not a little attention to the subject, but
unfortunately with very defective methods. Indeed, Grouven was the first
to collect and analyze the urines of fasting steers. The weight, specific
gravity, total nitrogen, dry matter, and ash were determined. In a few
instances the hippuric acid was estimated. Five animals were studied in
9 fasts which varied from 431/2 hours to 8 days in length. All of the fasts
were preceded by feeding periods of from 3 to 14 days, the ration usually
being circa. 3.5 kg. of rye straw. In an 8-day fast of an ox weighing 522
kg. the nitrogen elimination on the first two days was 32 gm. per day, on
the third and fourth days 54 gm., on the fifth and sixth days 40 gm., and
on the seventh and eighth days 68 gm. In a 5-day fast with an ox weighing
420 kg. the nitrogen elimination was 42 gm. per day on the first two days,
54 gm. on the next two days, and 51 gm. on the last day. With an animal
weighing 535 kg. the nitrogen excretion varied from 20 gm. on the first day
of fasting to 50 gm. on the fourth day. The other fasts were of 3 days’
duration or less. In several of them the nitrogen excretion was extremely
low, the lowest amount being 17 gm. on the first day.
The subject then remained almost entirely unstudied until 1906, when
Baer reported the effect of the withdrawal of carbohydrate upon various
animals, with reference to the onset of acidosis. Among the animals used
° Carpenter, Journ. Biol. Chem., 1923, 55, p. iii; ibid., Proc. Nat. Acad. Sci., 1925, 11, p. 155.
b Grouven, Physiologisch-chemische Futterungsversuche. Zweiter Bericht uber die Arbeiten
der agrikulturchemischen Versuchsstation zu Salmiinde, Berlin, 1864, pp. 127 to 195.
URINE
105
were 3 goats which fasted for a period of 3 days and then were given
phlorizin. The details of this study must be secured from the original
report.0 Of special interest is the 24-hour urinary nitrogen per kilogram of
body-weight, which calculation shows to be 0.28 and 0.29 gm. on the first
fasting day, i. e., a nitrogen-level considerably higher than that found with
our fasting steers. The ammonia constituted a small proportion of the total
nitrogen-content, with but little evidence of an acidosis. The excretion of
acetone was small and remained essentially constant during the fast.
Prayon,6 in 1910, studied the creatinine excretion in the urines of an ox,
a bull, and a mare during periods of normal feeding and during a 3-day
fasting period. He determined only the percentage content of creatinine,
however, and computed the weight of the creatinine from an assumed volume
of urine per day.
In 1920, Blatherwick,® studying the regulation of neutrality in the blood
of cattle, made determinations on the plasma and urine of a cow which
fasted and practically went without water for 7 days. The results of the
urine analyses are reported per 100 c. c. of urine. The ammonia increased
from 7 to 13 mg. in 4 days and the phosphorus from 20.6 to 156.3 mg. in
7 days. The author concludes that the only evidence of acidosis is the fact
that the phosphorus in the blood plasma showed an increase in the early
part of the fast.
In this same year Peters'* * published the results of his study of the urines
of normal goats upon different diets, fasting, and after feeding with acid and
alkali, with special reference to the acidity reaction, the titratable alkalinity,
the hydrogen-ion concentration, and the excretion of ammonia and chlorides.
Two goats fasted for 24 hours and one goat fasted for 48 hours. The urines
became more acid as the result of fasting, and in each instance reached the
greatest acidity on the day following the fasting period. The ammonia
excretion on the first day of fasting was 0.032 gm. per 24 hours with a goat
weighing 26 kg. and 0.072 gm. with a goat weighing 24 kg. The lighter
weight goat also fasted a second day, when the ammonia excretion was
0.105 gm.
Two communications were made by Palladine in 1924, who studied par¬
ticularly the creatine and the creatinine in the urine of adult sheep fasting
for various lengths of time. A sheep weighing 88 kg. had lost 12 kg. after
a 9-day fast. At the beginning of the fast the total nitrogen in the urine
amounted to 11.26 gm. for 24 hours, and at the end of the fast to 5.4 gm.
Creatinine was excreted during the entire fast, as was creatine after the
first day. The urinary nitrogen per kilogram of body-weight per 24 hours
was 0.128 gm. on the first day of the fast and 0.071 gm. on the last day.
The creatinine coefficient was 19.0 mg. on the first day and 18.1 mg. on the
° Baer, Arch. f. exp. Path. u. Pharm., 1906, 54, p. 153.
6 Prayon, Methoden zur Bestimmung des Kreatinins im Harne und Untersuchungen iiber
Kreatininausscheidungen im Harne der Herbivoren. Inaug.-Diss., Bern, 1910.
c Blatherwick, Journ. Biol. Chem., 1920, 42, p. 517.
d Peters, Biochem. Journ., 1920, 14, p. 697.
* Palladin, Arch. f. d. ges. Physiol., 1924, 203, p. 93; ibid., 204, p. 150.
106
METABOLISM OF THE FASTING STEER
last day. A second sheep, weighing 58.4 kg., fasted 16 days and lost 13.6
kg. The total urinary nitrogen on the first day was 19.05 gm. and on the
last day 6.17 gm. Creatinine was excreted during the entire fast. Creatine
began to be excreted on the third day and the excretion continued through¬
out the fast. The nitrogen excreted per kilogram of body-weight per 24
hours was 0.326 gm. at the beginning and 0.138 gm. at the end. The
creatinine coefficient fell from 20.0 to 15.5 mg. In a second communication
the results are given for an adult sheep, which weighed 64 kg. and fasted
8 days. The nitrogen in the urine on the first day was 9.43 gm., on the
second day 10.42 gm., and on the eighth day 5.40 gm. per 24 hours. The
author believes that during fasting there is an increase in the formation of
acids and that in the neutralization of these acids the excretion of ammonia
is increased. A comparison of the effect of an acid feed, such as oats, with
an alkaline feed following the fast showed a greater ammonia excretion
with the acid feed.
In connection with a study of the metabolism in acetonemia, Sjollema and
van der Zandea determined the total acetone bodies, ammonia nitrogen,
phosphoric acid, glucose, and calcium in the urine of milch cows. On three
different occasions they attempted to provoke acetonemia experimentally by
producing glycosuria with injections of phlorizin followed by fasting. They
found that during the days of the injections the urine contained 2.2 to 2.4
per cent of glucose, but no acetone bodies. Ketonuria occurred only when,
after some days of phlorizin glycosuria, no food was given to the cows for
2 days. The quantity of acetone, however, was much lower than in typical
acetonemia, about 0.4 gm. in 1,000 c. c. They conclude, therefore, that the
cow does not easily produce much acetone, except in certain diseased
conditions.
The most recent contribution to this study of the urine of fasting rumi¬
nants is that of Forbes, Fries, and Kriss,* 6 who, following a plan of Professor
Armsby, studied cows which fasted for 3, 6, and 9 days. Since the urine and
feces were not separated as a rule, it was possible to study the urine on only
a few days. During a 10-hour period at the end of the fourth fasting day
one cow voided 1.518 kg. of urine containing 28 gm. of nitrogen. During the
succeeding 24 hours she passed 1.804 kg. of urine containing 26.5 gm. of
nitrogen. Another cow on the sixth fasting day voided in 24 hours 1.978 kg.
of urine with a nitrogen content of 28.2 gm. At the end of 71/2 days she
excreted 42.8 gm. of nitrogen in a 24-hour period. In the case of another cow
on the sixth day 21.1 gm. of nitrogen were excreted in 24 hours. The daily
nitrogen excretion of this same cow during the sixth to the ninth day of
fasting was 28.7 gm. and during the seventh to the ninth day was 31.2 gm.
The difficulty of separating the urine and feces of cows has for years retarded
the study of the urine per se with cows. A satisfactorily functioning
mechanical device (eliminating the use of a harness or other encumbrances)
for the separation of the urine and feces of cows has been developed at the
New Hampshire Agricultural Experiment Station by one of us (E. G. R.)
and at the moment of writing is being most successfully employed.
“Sjollema and van der Zande, Journ. Metabolic Research, 1923, 4, p. 525.
6 Forbes, Fries, and Kriss, Journ. Dairy Sci., 1926, 9, p. 15.
URINE
107
Chemical Methods
Preservation of urine — The necessity of transporting the urines from Dur¬
ham to Boston, the unavoidable delay in the analyses at the Nutrition
Laboratory, and the lack of refrigeration made it imperative to develop a
method for the preservation of the urines. Willinger0 reports that the urine
of 12 large ruminants had an average pa of 8.70. Since this would predis¬
pose towards spoiling, we took immediate steps to have the urine made
acid. Varying amounts of concentrated hydrochloric acid were placed in
the collection bottles, and if, in spite of this, it was found at the time of
weighing the bottles and contents that the urine was still alkaline, further
acid was added until the urine reacted acid. We have evidence that decom¬
position of some nitrogenous substances takes place rapidly in the original
urine, even in the presence of thymol or chloroform. Undoubtedly creatinine
rapidly disappears.
Methods of analysis — To the collected volume of urine there was auto¬
matically added a certain amount of water whenever the collection was
made inside the respiration chamber, this water being necessary to seal the
trap in the urine hose. The analyses were made on the volumes of urines,
and consequently it was necessary to calculate the volume of the urine plus
the water and hydrochloric acid added. The analyses of the nitrogenous
constituents were for the most part made by the commonly accepted supe¬
rior methods of Folin and his associates,6 but in the case of the phenols, for
example, Tisdall’s modification of Folin’s method was used.0
Statistics of Results
It is impossible to report in detail in this monograph the results of all
the innumerable analyses carried out by Dr. Carpenter and his associates,
and reference must be made for such details to the extensive discussion of
the urines of these fasting steers to be published later. In the fasts of steers
C and D up to and including those in November 1922, the chief urinary
constituents determined were the total nitrogen and the total chlorides.
The data for these determinations, together with the records of the volumes
of urine excreted, have been summarized in Table 28. In the fasts of steers
C and D in November 1923 and March 1924, and in the fasts of the two
younger steers, E and F, in February 1924, much more extensive urine
analyses were carried out. The study of the total nitrogen has long been
considered an important one, but this study has now been surpassed, thanks
to the researches of Folin, by an interest in the partition of the nitrogen.
The analyses of the urines during these later fasts therefore included the
partition of the nitrogen according to modern methods, and the results have
been recorded in Table 29. Since it was necessary to preserve the urines in
these later fasts with hydrochloric acid, no determinations of the chlorides
were made, but determinations were made of the total nitrogen, urea-
nitrogen, ammonia-nitrogen, amino-acid nitrogen, hippuric-acid nitrogen,
and preformed and total creatinine, the data for all of which are given in
0 Willinger, Arch. f. d. ges. Physiol., 1924, 202, p. 468.
b Folin, Laboratory manual of biological chemistry, New York, 1922.
* Tisdall, Journ. Biol. Chem., 1920, 44, p. 409.
108
METABOLISM OF THE FASTING STEER
Table 28. — Volume of urine and total nitrogen and chlorides in urines of steers C and D from
December 1921 through November 1922
Date and steer
1921
Steer C:
Nov. 26 to Dec. 6.
Dec.
Dec.
Dec.
Dec.
Dec.
Dec.
6- 7.
7- 8.
8- 9.
9- 10.
10-11.
11-12.
Dec. 12-13.
Dec. 13 to Dec. 22. . . .
Steer D:
Nov. 26 to Dec. 6 .
Dec.
Dec.
Dec.
Dec.
6- 7.
7- 8.
8- 9.
9- 10.
Dec. 10-11.
Dec. 11-12.
Dec. 12-13.
Dec. 13 to Dec. 22. . . .
Steer C:
Dec. 22, 1921, to Jan. 4,
1922 .
1922
Jan. 4- 5 .
Jan. 5- 6 .
Jan. 6- 7 .
Jan. 7- 8 .
Jan. 8- 9 .
Jan. 9-10 .
Jan. 10-11 .
Jan. 11-12 .
Jan. 12-13 .
Jan. 13-14 .
Jan. 14 to Feb. 2 .
Steer D:
Dec. 22, 1921, to Jan.
4, 1922
Jan. 4- 5 .
Jan. 5— 6 .
Jan. 6— 7 .
Jan. 7- 8 .
Jan. 8— 9 .
Jan. 9-10 .
Jan. 10-11 .
Jan. 11-12 .
Jan. 12—13 .
Jan. 13-14 .
Jan. 14 to Feb. 2 .
Dura¬
tion
of
period
hrs.
10 days
24
22
26
18
24
28
18
9 days
10 days
24
24
24
25
3 16
25
25
9 days
13 days
24
24
24
16
29
28
21
27
18
27
18 days
13 days
24
23
26
24
23
22
28
23
22
26
19 days
Volume of urine
Total
liters
145.74
6.46
3.40
3.10
1.91
2.91
2.60
1.62
132.28
‘44.17
8.43
2.87
1.42
5.46
3 1.79
1.40
4.94
‘33.99
‘67.46
9.21
4.30
3.21
1.62
2.25
4.54
2.07
1.60
1.55
1.80
66.61
67.75
12.84
3.46
4.42
3.10
3.11
3.00
4.25
1.83
1.32
2.43
‘75.12
Per
hour
c. c.
5 191
269
157
117
103
122
93
91
*149
3 184
351
121
60
223
112
57
200
157
! 216
384
179
134
103
78
165
98
59
86
67
! 154
2 217
535
150
173
129
138
139
152
80
61
93
3 165
Total nitrogen
For
period
gm.
594
64.7
60.0
81.5
42.3
50.8
55.5
42.7
280
575
49.3
50.7
48.3
61.2
3 32. 7
53.1
50.7
210
1242
123
118
89.8
44.2
66.9
62.3
37.1
43.6
30.4
44.7
802
1320
122
89.9
85.4
66.8
57.0
49.9
55.7
37.8
32.2
35.6
905
Per
hour
gm.
2.48
2.70
2.77
3.08
2.29
2.13
1.98
2.41
1.30
2.40
2.05
2.13
2.03
2.50
2.05
2.14
2.06
.97
3.98
5.15
4.91
3.74
2,81
2.31
2.27
1.77
1.61
1.68
1.66
1.86
4.23
5.07
3.91
3.35
2.78
2.53
2.32
1.99
1.64
1.50
1.37
1.99
Chlorides (NaCl)
For
period
gm.
29.0
5.56
1.82
1.06
1.42
1.46
.823
34.0
8.77
.290
.305
.820
42.9
10.5
2.58
.727
1.67
4.60
3.39
.900
1.75
2.28
48.7
16.7
4.26
1.17
Per
hour
gm.
1.21
.257
.069
.057
.060
.052
.046
1.42
.369
.012
.012
.033
1.79
.438
.108
.046
.058
.167
.162
.033
.097
.084
2.03
.728
.167
.045
1 Kilograms.
2 Grams.
3 Urine for the period 2 p. m. to 7h31m p. m. Dec. 10 was lost.
URINE
109
Table 28. — Volume of urine and total nitrogen and chlorides in urines of steers C and D from
December 1921 through November 1922 — Continued
Date and steer
Dura¬
tion
of
period
Volume of urine
Total nitrogen
Chlorides (NaCl)
Total
Per
hour
For
period
Per
hour
For
period
Per
hour
1922
hrs.
liters
c. c.
gm.
gm.
gm.
gm.
Steer C:
Mar. 31 to Apr. 17. . . .
17 days
‘68.11
3 167
1229
3.01
Apr. 17-18 .
24
5.18
216
78.2
3.26
55.4
2.31
Apr. 18-19 .
21
7.63
363
75.2
3.58
13.7
.655
Apr. 19-20 .
24
5.21
217
67.8
2.83
Apr. 20-21 .
24
3.10
129
78.6
3.28
Apr. 21-22 .
24
1.97
82
57.9
2.41
1.72
.072
Apr. 22-23 .
27
3.78
140
63.9
2.37
1.19
.044
Apr. 23-24 .
21
2.13
101
42.9
2.03
.926
.044
Apr. 24—25 .
24
1.87
77
48.8
2.00
.972
.040
Apr. 25-26 .
24
2.03
86
52.3
2.23
.563
.024
Apr. 26-27 .
21
2.07
101
34.3
1.67
1.06
.052
Apr. 27-28 .
30
4.57
151
51.9
1.71
5.42
.179
Apr. 28-29 .
22
1.97
90
36.3
1.65
2.01
.092
Apr. 29-30. . . .
20
1.57
78
39.7
1.99
1.45
.073
Apr. 30-May 1 .
30
2.31
77
47.2
1.57
2.61
.087
May 1 to May 9 .
8 days
‘19.30
3 101
222
1.16
Steer D:
Mar. 31 to Apr. 17. . . .
17 days
‘74.95
3 184
1304
3.20
Apr. 17—18 .
24
5.54
231
91.1
3.80
53.6
2.23
Apr. 18-19 .
24
6.64
273
88.9
3.65
19.0
.779
Apr. 19-20 .
22
6.94
322
78.7
3.65
7.52
.349
Apr. 20-21 .
25
3.14
124
71.1
2.80
.927
.037
Apr. 21-22 .
25
2.38
97
62.3
2.53
1.47
.060
Apr. 22-23 .
24
2.23
92
56.5
2.33
1.48
.061
Apr. 23-24 .
24
1.54
65
38.9
1.66
.621
.026
Apr. 24-25 .
25
1.82
74
44.0
1.80
Apr. 2*>—2fi . . , .
24
1 89
80
38.3
1.63
Apr. 26-27 .
25
7.63
305
45.1
1.80
6.90
.276
Apr. 27-28 .
24
2.28
96
35.0
1.48
4.65
.196
Apr. 28-29 .
24
3.76
155
37.3
1.54
6.67
.275
Apr. 29-30 .
23
5.63
242
35.8
1.54
7.11
.305
Apr. 30-May 1 .
22
1.87
85
33.9
1.54
2.12
.096
May 1 to May 9 .
8 days
‘22.40
3 117
208
1.08
Steer C :
May 9 to June 1 .
23 days
‘103.39
3 187
1839
3.33
572
1.04
June 1- 2 .
24
6.91
288
100
4.19
39.3
1.64
June 2- 3 .
24
9.76
407
103
4.30
50.3
2.10
June 3- 4 .
23
4.00
176
80.5
3.57
11.1
.492
June 4- 5 .
23
2.45
105
62.0
2.67
3.09
.133
June 5— 6 .
24
2.98
125
60.8
2.54
4.00
.167
1 Kilograms.
3 Grams.
110
METABOLISM OF THE FASTING STEER
Table 28. — Volume of urine and total nitrogen and chlorides in urines of steers C and D from
December 1921 through November 1922 — Continued
Date and steer
Dura¬
tion
of
period
Volume of urine
Total nitrogen
Chlorides (NaCl)
Total
Per
hour
For
period
Per
hour
For
period
Per
hour
1922
hrs.
liters
c. c.
gm.
gm.
gm.
gm.
Steer D:
May 9 to June 1 .
23 days
*101.22
2 183
1902
3.45
599
1.09
June 1- 2 .
23
6.70
291
93.8
4.08
73.1
3.18
June 2— 3 .
24
3.90
159
96.2
3.93
June 3— 4 .
24
8.78
363
88.1
3.64
June 4- 5 .
24
2.90
122
66.1
2.77
1.87
.078
June 5— 6 .
23
7.28
317
62.9
2.73
Steer C:
Nov. 6— 7 .
22
8 5.79
8 263
8 99.0
8 4. 50
Nov. 7- 8 .
26
3.42
133
100.6
3.92
Nov. 8- 9 .
18
1.76
99
59.4
3.35
Nov. 9—10 .
30
2.88
97
94.5
3.19
Nov. 10—11 . .
25
2.79
112
80.0
3.21
Nov. 11—12 .
16
1.86
119
49.3
3.16
Nov. 12-13 .
25
2.57
104
73.4
2.97
Nov. 13-14 .
24
2.55
105
66.5
2.74
Nov. 14—15 .
29
2.58
89
72.0
2.4S
Steer D:
Nov. 6— 7 .
22
6.06
276
99.4
4.52
Nov. 7- 8 .
20
2.82
139
91.6
4.51
Nov. 8- 9 .
28
2.72
97
93.3
3.34
Nov. 9—10 .
25
3.21
127
80 0
3.18
Nov. 10—11 .
24
5 58
237
86 0
3.65
Nov. 11-12 .
25
3.84
155
71.3
2.88
Nov. 12-13 .
17
<1.84
4 109
4 47.8
4 2.84
Nov. 13-14 .
24
1.94
81
54.5
2.28
1 Kilogram. 2 Grams. 8 Some urine was spilled.
4 Approximately 200 grams of urine were lost.
Table 29. In practically all of the fasts other urinary constituents were
also determined, such as inorganic sulphate, ethereal sulphate, neutral sul¬
phur, and total sulphur, the free and conjugated phenols, acetone and dia-
cetic acid (determined together), /?-oxybutyric acid, total fixed bases, and
the organic acids, but reference must be made to Carpenter’s report for
these details.
The ever-present complexity of irregularity in the voiding of urine and
the high probability of the incomplete emptying of the bladder, particularly
at the end of the period of collection, make the study of the urinary output
and its constituents on any time basis always somewhat approximate.
Because of the inability to secure sharply divided 24-hour periods, the
record of the exact time of each urination became important, and this was
usually noted carefully in the later fasts. In the earlier fasts the lack of
enough assistants made such records somewhat uncertain, although they
were kept. In general, however, each period of collection represents not
far from a 24-hour day. In the fasts recorded in Table 28 the periods of
collection have been recorded to the nearest hour, as they were all approxi-
URINE
111
Table 29. — Amounts per hour of nitrogen constituents determined in urines of fasting steers — Continued
METABOLISM OF THE FASTING STEER
Total
creatinine
si • •
«OO^NNhnhO)CO«COcOONOO
OiNNCDcDcOCDiOOiOiOCONCDCOiOcDcD
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Preformed
creatinine
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nitrogen
gm.
0.318
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nitrogen
gm.
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Ammonia-
nitrogen
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Urea-
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Total
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gm.
0.93
1.18
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Volume
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Duration
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.8
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Date and steer
1924
Steer D:
Feb. 27-Mar. 2 .
Mar. 2- 3 .
Mar. 3 .
Mar. 3- 4 .
Mar. 4 .
Mar. 4- 5 .
Mar. 5 .
Mar. 5- 6 .
Mar. 6 .
Mar. 6- 7 .
Mar. 7 .
Mar. 7- 8 .
Mar. 8 .
Mar. 8- 9 .
Mar. 9 .
Mar. 9-10 .
Mar. 10 .
Mar. 10-11 .
Mar. 11 .
Mar. 11-12 . .
Mar. 12 .
Mar. 12-13 .
Mar. 13 .
Mar. 13-14 .
Mar. 14 .
Mar. 14-15 .
URINE
113
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114
METABOLISM OF THE FASTING STEER
mately 24 hours long. Hence the total daily amounts are reasonably com¬
parable from day to day. The large differences in the time intervals occa¬
sionally found must, however, always be held in mind in making any final
deductions. In the fasts in November 1923, recorded in Table 29, the
24-hour period of collection was likewise adhered to reasonably closely. In
the 1924 fasts the collections were made more frequently, and in Table 29,
therefore, the length of each period is given in hours and minutes.
Since it was impossible in these fasts to secure sharply divided 24-hour
or 12-hour periods, it has seemed best to discuss the chemistry of the urine
in all of the different fasts on the basis of the amounts per hour. Aside from
the total excretion of nitrogen, which is of chief interest in connection with
the protein loss, the chemical analysis of the urine is of the greatest value
in indicating the proportions of the various ingredients excreted and the
changes in these relationships as the fasts progressed. Hence in practically
all cases the expression of the results on the per hour basis is reasonably
satisfactory. Logically there is no reason for adhering to the 24-hour
period, since fasting brings about a change in the metabolic level which
takes place from hour to hour as well as from 24 hours to 24 hours. Hence
the hourly values reported in Table 29 for the later fasts present a much
more intelligent picture of the course of the excretion of the different urinary
constituents.
In addition to the study of the urine during the fasting periods proper,
analyses were also made during the feed periods preceding and following the
fasts. The data for these feed periods are likewise recorded in Tables 28
and 29, being separated from the fasting data by horizontal lines. In
Table 28 the total volume of urine during these feed periods is given in
kilograms instead of in liters, and the volume of urine per hour is given in
grams instead of in cubic centimeters, as indicated at the head of the
columns in the table.
One must realize, in analyzing these data, that the fasts in November
followed pasture feeding and that prior to all the other fasts, with the
exception of those in February and March 1924, the steers had been receiv¬
ing an approximately maintenance ration of hay and meal. In the 1924
fasts all four steers had been for a considerable period of time on a low
nutritive plane.
Discussion of Results
CHLORIDES IN URINE
In the first few fasts of steers C and D, information was secured regarding
the chlorides in urine, as shown in Table 28. Since the chloride excretion
is dependent in large part upon the intake, the rapid fall noted in this
excretion during the fasting periods is not surprising. The excretion drops
off enormously, until the hourly values become as low, in one instance, as
13 mg. Owing to the necessity for using hydrochloric acid to preserve the
urines, it was, unfortunately, impossible to study the chloride excretion
during the fasts at the submaintenance level.
URINE
115
NITROGEN EXCRETED IN URINE PER HOUR
Nitrogen is the most characteristic chemical element in urine and for
decades has been considered to be an essential index of protein metabolism.
The nitrogen excretion per hour is recorded in both Table 28 and Table 29.
The probable 24-hour excretion will be considered subsequently (see pp.
127 to 129) in connection with the discussion of the daily loss of nitrogen
both in the urine and in the feces, but the hourly rate of excretion is of
immediate importance.
Prior to the fasts the hourly excretion of nitrogen by steers C and D is
not far from 2.5 to 4.5 grams, except prior to the fasts in March 1924, at
the submaintenance level, when the hourly output is much lower. Similarly,
with steers E and F the influence not only of submaintenance feeding but
of smaller body-weights results in a low hourly output, even prior to the
fast. The important influence of the preceding ration upon the hourly
nitrogen excretion is shown in the fasts in March 1924 with steers C and D,
when the body- weights at the beginning of the fasts were about 600 kg. As
a matter of fact, the body-weights were the third highest in the long series
of fasts with these two animals, and yet the nitrogen per hour is lower in
this fast than in any of the preceding fasts. Following submaintenance
feeding, there is a gradual increase in the nitrogen excretion in the first four
days of fasting, but in the fasts following maintenance feeding the nitrogen
has a tendency to fall off as the fast progresses. The minimum values with
both animals are found, as is to be expected, in the fasts at the submain¬
tenance level, when the excretions of both steers settle down to approxi¬
mately 1.6 and 1.8 grams per hour. This corresponds to not far from 40
grams per 24 hours. If the urinary nitrogen excretion of a man weighing
approximately 60 kg., or one-tenth of what these steers weighed, is assumed
to be one-tenth of the minimum nitrogen excretion noted with these steers,
it would be about 4.0 grams. This is about as low a value as has ever been
found with man, except for the values obtained by Petren“ with his diabetic
patients on a diet high in fat and low in protein. The taking of food fol¬
lowing these fasting experiments almost invariably lowered the nitrogen
output even below that of the last day of the fast, due in all probability to
the storage of nitrogen to replenish the loss and to the protective action of
the carbohydrate.
That the excretion of nitrogen was essentially independent of the volume
of urine is brought out by the comparison of the volume of urine excreted
per hour and the actual nitrogen output. A typical instance is the com¬
parison for steer C in the fast in January 1922. On the fifth day, January
8-9, the volume was 78 c. c. per hour and on the next day it was more than
double, i. e., 165 c. c., but the nitrogen output, on the contrary, decreased
from 2.31 to 2.27 gm. per hour. In most of the fasts the nitrogen excretion
either remains at a fairly constant level or gradually decreases, irrespective
of the volume of urine, and thus there is not a “washing-out” effect of previ¬
ously metabolized nitrogenous products. Even on the low metabolic plane
in the March fasts great variations in the volume of urine are found with a
° Petr6n, Proc. XI Internat. Physiol. Congress, Edinburgh, 1923; ibid., Diabetes-Studier,
Copenhagen, 1923, p. 545.
116
METABOLISM OF THE FASTING STEER
fairly constant level of nitrogen excretion, a greater irregularity being noted
with steer D than with steer C. With steers E and F, an- indication of a
relationship between the volume of urine and the nitrogen excretion is fre¬
quently found. For example, on February 14 the volume of urine excreted
by steer E per hour is 642 c. c. and the nitrogen per hour is 1.80 gm. The
period is, to be sure, short. During the next period of 14 hours and 4 minutes
the volume per hour is only 46 c. c. and the nitrogen output is 0.84 gm., or
one-half that of the preceding period. There is, in this instance, a decrease
in both factors, but in no sense a strict relationship between the two.
From this experience and from that of Forbes, Fries, and Kriss,° one
might suggest that when it is desirable to study the periodic variations in
the nitrogen output after the ingestion of food or the hourly variations in
the urine even during fasting, preliminary experiments with animals should
be made and an animal selected which shows regularity in nitrogen excretion.
It is evident in our series of fasts, for example, that steer C is extraordinarily
regular in the voiding of the nitrogen constituents, irrespective of the quan¬
tity of the urine. One might infer that at each voiding the bladder was
reasonably well emptied and that physiologically the animal functioned
regularly. Steer F was likewise regular, but steers D and E show con¬
siderable variability in the excretion of the urinary constituents. Further
consideration of the nitrogen output may best be made when the apportion¬
ment of the nitrogen among its various constituents is studied.
PARTITION OF TJRINARY NITROGEN
In the fasts of steers C and D in November 1923, the combined urea-
nitrogen and ammonia-nitrogen decreases as the fast progresses. (See
Table 29.) A striking fall in the amino-acid nitrogen and the hippuric-acid
nitrogen was observed, particularly after the first day. The results for the
preformed and total creatinine are hardly interpretable without reference
to the total nitrogen excretion on the same day, but they both remain high,
with little indication of a falling off. In the fasts in March 1924, at the
submaintenance level, the urea-nitrogen and the ammonia-nitrogen are
separated for the first time, and it is clear from these results that there is a
distinct tendency for the urea-nitrogen to increase and for the ammonia-
nitrogen to remain essentially constant after the first two or three days.
The amino-acid nitrogen in the case of steer C drops off markedly during
fasting, as does the hippuric-acid nitrogen, but the preformed and total
creatinine remain fairly constant. After the fast, when food is given, little
change takes place except that the urea-nitrogen decreases somewhat and
the ammonia-nitrogen increases. With steer D the picture is not unlike
that with steer C, namely, a rise in the urea-nitrogen, a tendency for a
slight increase in the ammonia-nitrogen, a rapid decrease in the amino-acid
and the hippuric-acid nitrogen, and essential constancy in the creatinine.
With refeeding there is a striking fall in the urea-nitrogen of steer D. The
ammonia-nitrogen tends to remain about constant and the amounts of
amino-acid and hippuric-acid nitrogen tend to increase. There is no strik¬
ing change in the creatinine.
° Forbes, Fries, and Kriss, Journ. Dairy Sci., 1926, 9, p. 15.
URINE
117
Table 30. — Partition of nitrogen excreted in unnes of fasting steers
Proportion of total nitrogen in —
Date and steer
Urea
Am¬
monia
Amino
acids
Hip-
puric
acid
Pre¬
formed
creati¬
nine
Total
creati¬
nine
Steer C: 1923
p. ct.
p. ct.
p. ct.
p. ct.
p. ct.
p. ct.
Nov. 5- 6 .
75
.9
1.0
3.7
5.4
8.1
Nov. 6- 7 .
77
.9
.5
2.2
5.2
9.2
Nov. 7- 8 .
82
.7
.4
1.4
6.5
11.2
Nov. 8- 9 .
81
.0
.4
1.3
8.3
10.5
Nov. 9-10 .
74
.1
.6
1.5
9.3
10.8
Steer D:
Nov. 5- 6 .
78.9
2.0
3.4
5.9
8.4
Nov. 6- 7 .
82
.2
.3
2.0
7.1
10.3
Nov. 7— 8 .
65
.7
.4
1.6
7.4
10.9
Nov. 8- 9 .
74
.1
.3
1.3
8.7
10.3
Nov. 9-10 .
74
.7
.3
1.8
7.9
9.7
Steer C: 1924
Mar. 2— 3 .
38
.3
17.8
27.5
18.0
20.0
Mar. 3 .
26.4
6.7
6.0
22.9
23.8
Mar. 3- 4 .
40.1
2.1
3.0
8.9
25.3
27.7
Mar. 4 .
29.1
2.2
2.5
9.5
20.0
20.2
Mar. 4-5 .
58.4
1.1
1.1
6.3
14.7
16.8
Mar. 5 .
1 51 . 6
>4.6
1 1.5
1 12.9
1 17 . 6
Mar. 5 .
63.6
3.2
1.2
3.6
13.8
17.6
Mar. 5-6 .
58.7
1.6
.7
2.3
13.4
18.3
Mar. 6-7 .
64.7
2.0
.8
1.9
12.6
18.0
Mar. 7 .
62.4
3.7
.5
1.8
13.0
14.8
Mar. 7-8 .
67.0
2.8
.6
1.8
12.9
13.7
Mar. 8-9 .
68.6
2.6
.5
1.6
12.6
13.1
Mar. 9 .
66.2
3.5
.5
1.7
13.5
13.8
Mar. 9-10 .
71.1
2.9
.7
1.7
13.6
13.3
Mar. 10 .
69.3
3.7
.7
1.6
13.5
13.1
Mar. 10-11 .
66.9
3.4
.7
1.7
13.5
13.3
Mar. 11 .
70.0
3.9
.7
14.5
14.3
Mar. 11-12 .
75.5
2.0
.7
1.7
15.0
15.1
Mar. 12-13 .
70.1
3.7
.6
1.7
14.6
15.5
Mar. 13-14 .
66.0
5.0
.9
2.5
15.1
16.1
Mar. 14 .
59.2
6.5
1.2
16.0
16.2
Mar. 14-15 .
61.1
5.8
1.1
6.2
13.6
14.7
Steer D: 1924
Mar. 2-3 .
34
.7
18.9
26.8
Mar. 3 .
33.2
7.3
3.5
26.9
27.7
Mar. 3-4 .
34.3
3.1
2.9
16.1
23.8
24.0
Mar. 4 .
68.4
3.5
1.4
10.3
18.3
19.5
Mar. 4-5 .
54.7
1.5
1.0
5.6
20.1
18.5
Mar. 5 .
59.9
2.5
.9
4.3
17.2
16.3
Mar. 5-6 .
57.0
3.0
.7
2.9
17.8
17.0
Mar. 6 .
57.0
7.7
.7
2.6
12.2
13.2
Mar. 6-7 .
61.9
4.3
.6
2.2
15.3
14.7
Mar. 7 .
58.8
4.4
.6
1.9
13.8
13.6
Mar. 7-8 .
67.6
5.9
.5
1.8
13.7
12.1
Mar. 8 .
59.5
7.0
.8
1.8
13.0
11.3
Mar. 8-9 .
61.2
4.6
.6
1.6
13.5
13.7
Mar. 9 .
59.8
5.3
.6
1.5
14.0
14.5
Mar. 9-10 .
65.6
5.7
.7
1.4
13.4
13.4
Mar. 10 .
1
66.4
5.7
.9
1.5
13.1
13.5
1 The urine collected for steer C during this period was all that could be caught. It is esti¬
mated to be about one-third of the total urination.
118
METABOLISM OF THE FASTING STEER
Table 30. — Partition of nitrogen excreted in urines of fasting steers — Continued
Proportion of total nitrogen in —
Date and steer
Urea
Am¬
monia
Amino
acids
Hip-
puric
acid
Pre¬
formed
creati¬
nine
Total
creati¬
nine
Steer D — Cont. 1924.
p. ct.
p. ct.
p. ct.
p. ct.
p. ct.
p. ct.
Mar. 10-11 .
74.4
4.2
0.6
1.5
13.4
13.6
Mar. 11 .
71.2
6.1
1.3
. . . .
13.1
12.7
Mar. 11-12 .
71.5
5.0
.8
1.5
15.9
15.4
Mar. 12 .
62.8
7.5
.8
2.1
15.5
16.2
Mar. 12-13 .
53.9
5.2
.8
2.8
17.3
18.4
Mar. 13 .
50.1
8.0
1.0
4.7
17.6
18.3
Mar. 13-14 .
47.1
8.9
1.8
8.2
21.1
22.0
Mar. 14 .
34.7
7.2
1.4
9.8
19.3
20.5
Mar. 14-15 .
38.7
5.2
3.2
15.9
23.2
23.9
Steer E:
Feb. 11-12 .
18.2
38.1
15.0
5.6
4.2
8.0
Feb. 12 .
16.3
6.1
6.2
11.9
Feb. 12 .
15.6
22.7
6.2
13.8
9.2
13.5
Feb. 12-13 .
28.2
16.2
7.9
15.2
11.8
15.5
Feb. 13-14 .
53.3
7.6
3.8
7.1
11.3
13.5
Feb. 14 .
66.0
7.2
1.4
4.4
9.3
13.8
Feb. 14 .
68.1
6.3
1.4
3.7
8.6
14.5
Feb. 14-15 .
62.1
3.2
.7
3.0
11.3
18.3
Feb. 15 .
61.1
3.9
.7
....
9.6
15.1
Feb. 15 .
60.5
5.2
.9
....
9.6
15.1
Feb. 15-16 .
62.9
8.5
1.4
....
7.3
13.2
Feb. 16 .
....
....
1.0
1.8
6.4
12.6
Feb. 16 .
....
2.6
.9
6.7
13.0
Feb. 16-17 .
50.4
10.9
1.0
1.9
7.6
13.2
Feb. 17 .
53.9
12.9
1.7
1.8
8.1
13.4
Feb. 17 .
50.0
7.6
.8
....
11.9
18.0
Feb. 17-18 .
1 54.8
117.0
16.3
14.5
1 8.4
*13. 6
Feb. 18-19 .
21.6
16.9
8.0
17.1
9.2
12.1
Feb. 19 .
25.7
8.1
9.3
18.0
12.7
16.6
Feb. 19-20 .
19.6
11.2
8.4
25.6
14.9
16.3
Feb. 20 .
11.2
9.0
8.1
23.2
16.2
17.8
Steer F:
Feb. 11-12 .
38.5
13.9
15.9
21.7
9.7
12.4
Feb. 12 .
39.9
10.7
8.1
....
9.5
12.3
Feb. 12-13 .
19.2
10.6
6.1
18.2
12.2
15.1
Feb. 13 .
2 25.5
2 11.4
2 4.8
....
2 14.2
2 17.6
Feb. 13 .
42.8
12.9
7.0
....
13.1
16.2
Feb. 13 .
20.2
3.8
2.5
....
18.2
20.8
Feb. 13-14 .
62.6
3.5
2.6
5.9
13.0
15.4
Feb. 14 .
....
....
....
....
12.4
14.9
Feb. 14-15 .
57.0
2.4
.8
2.6
11.2
17.9
Feb. 15 .
36.2
2.1
.4
....
9.7
16.8
Feb. 15-16 .
64.9
3.9
.8
1.6
9.7
15.4
Feb. 16 .
63.4
4.9
.4
....
8.7
13.8
Feb. 16-17 .
70.1
5.2
.5
1.3
10.0
14.6
Feb. 17 .
69.2
6.4
.4
....
8.7
12.5
Feb. 17-18 .
71.5
6.8
.7
1.3
8.7
12.4
Feb. 18 .
28.2
6.9
.8
....
10.2
15.4
Feb. 18-19 .
50.3
6.6
.9
3.2
9.3
14.7
Feb. 19-20 .
52.7
8.5
2.1
10.8
10.6
11.7
Feb. 20 .
35.8
8.9
3.0
16.1
11.1
12.7
1 This urine was contaminated by a small amount of feces.
2 This mine is only a portion of the mine for the period. About 300 grams of urine were lost.
URINE
119
The younger animals in their fast at the submaintenance level presented
a different picture in some ways. The findings are essentially the same for
both steers. In the first place, the total amount of nitrogen varies con¬
siderably. There is a tendency for the urea-nitrogen to increase. There is
great variability in the ammonia-nitrogen, a decrease in the amino-acid and
hippuric-acid nitrogen, and a striking increase in the creatinine, both pre¬
formed and total. The considerable difference between the preformed and
total creatinine indicates that these animals excreted creatine. When feed
is given after the fast, there is a great fall in the total nitrogen per hour, a
decrease in the urea-nitrogen and the ammonia-nitrogen, an increase in the
amino-acid and hippuric-acid nitrogen, essential constancy in the preformed
creatinine, and a great decrease in the total creatinine, particularly after
the first period of refeeding.
Since the total nitrogen excretion changed during fasting, a more careful
interpretation of these changes in the nitrogenous ingredients can be secured
only by a study of the proportion of nitrogen excreted in the various forms
and the changes in these proportions as time goes on. The data for this
study are shown in Table 30.
Urea and ammonia-nitrogen — From an examination of the distribution of
the nitrogen it is seen that during fasting the urea-nitrogen becomes a greater
proportion of the total urinary nitrogen than it is during feeding, and that
with the resumption of food the urea becomes a smaller proportion of the
total nitrogen eliminated. Unfortunately, the only experiments in which
the urea-nitrogen was determined by itself are in the fasts with the four
animals in 1924, at the submaintenance level. In the November fasts in
1923 the proportion of total nitrogen in the combined urea and ammonia-
nitrogen remains essentially constant as the fast progresses. In the 1924
fasts, on the contrary, the nitrogen from urea rises rapidly from 26 per
cent on March 3 with steer C to 70 per cent or over at the end of the fast.
Low proportions are noted in the fasts with the other animals likewise, from
as low as 33 per cent with steer D to 15 per cent with steer E and 19 per cent
with steer F. In the case of all four animals the percentage of urea-nitrogen
rises as the fast progresses, approaching finally a proportion that is com¬
monly found with humans or carnivorous animals subsisting upon a nitro¬
gen-free diet. The subsequent taking of food in these experiments has a
most profound effect upon this proportion in that after the first two days
the percentage of urea-nitrogen tends to be low, corresponding to the initial
values. The ammonia-nitrogen was likewise determined in the four experi¬
ments at the submaintenance level. The values during the fasts are low in
general, and suggest that there was no particular call for extra ammonia to
neutralize any acid formation. For the most part the figures are regular in
all four fasts. It is a noticeable fact that with all the steers the taking
of food in practically every case raises the proportion of ammonia-nitrogen
excreted in urine. In certain instances, notably in the experiment with
steer E prior to the fast and even on the first day of the fast, the very high
ammonia values suggest the possibility that the urine may have decomposed.
Hippuric-acid nitrogen — In this determination one obtains the amount of
benzoic acid present, and one must assume that the nitrogen was combined
120
METABOLISM OF THE FASTING STEER
with benzoic acid to form hippuric acid. We have already seen that there
is a tendency for the amount of hippuric-acid nitrogen to decrease as the
fast goes on. This is also shown by the percentage values, which fall
appreciably. With the resumption of feeding the values increase again.
The absolute values for hippuric-acid nitrogen excreted by all four of these
animals, as shown in Table 29, are closely alike during the fasting-periods.
It seems singular that animals with such large differences in body-weight
should have such uniformity in this excretion. Indeed, this finding suggests
that there is a constancy in the hippuric acid eliminated, indicating that it
is of endogenous origin.
Preformed creatinine — Folina attracted the attention of physiologists to
the significance of creatinine in protein metabolism. The existence of
creatinine in the body in the form of creatine and creatinine and the fact
that creatine has been found in the urines of fasting humans led to our
determining both in these samples. As has been already pointed out, the
total amount of preformed creatinine remains relatively constant with the
adult animals. This holds true to a certain extent with the total creatinine
also, but the younger animals show very different reactions and indicate a
considerable excretion of creatine as such. The creatinine elimination of
steers E and F is smaller than that of the larger steers, C and D. The per¬
centage of the total nitrogen in the form of preformed creatinine was fairly
constant in the fast in November 1923, with a tendency to increase. On the
contrary, in the fasts at the submaintenance level, particularly with the two
older animals, there was a distinct decrease in the percentage of nitrogen
excreted in this form as the fast progressed.
Total creatinine — The total creatinine expresses the preformed creatinine
plus any creatine which has been converted by hydrolysis into creatinine.
In the November fasts of 1923 there is a distinctly greater amount of total
creatinine than preformed creatinine, showing excretion of creatine as such.
In the fasts of the larger animals in 1924, at the submaintenance level, a
difference between the preformed and the total creatinine is to be found only
during the first part of the fast. With steers E and F the differences between
preformed and total creatinine are more marked than with steers C and D
in the fasts after submaintenance feeding. Indeed, a considerable propor¬
tion of the creatinine is in the form of creatine. The difference between the
two creatinines actually persists for some little time, even after food is
taken. It thus seems that the smaller animals were much more affected by
fasting, as evidenced by the increasing elimination of creatine, but with the
larger animals the data would suggest that during feeding there was a
constant elimination of creatine.
Creatine — From the findings with steers C and D in the fasts in Novem¬
ber 1923, that is, after full pasturage, when a rather striking excretion of
creatine is shown, one could argue that on feed there is a regular excretion
ol creatine, which disappears when the animal fasts at a lower nutritive
plane. This is contrary to the experience with humans, with whom as the
fast progresses there is an increased excretion of creatine. The appearance
of creatine in the urine during feeding, particularly in the case of the two
a Folin, Am. Journ. Physiol., 1905, 13, p. 83.
URINE
121
smaller steers, prior to the fast and shortly after refeeding, was again
rather unusual. Dr. Carpenter suggests that this may be due not to the
fact that creatine is a metabolic product but to the fact that the urine
actually decomposes in the bladder of the animal before it is voided. When
one recalls that the urines of herbivora are highly alkaline, it does not seem
impossible that the retention of such a fluid at body-temperature might
result in the change from creatinine to creatine. As a matter of fact, one
of Carpenter’s experiments has shown that when creatinine was added to
one of these urines it disappeared quickly. After the urine is voided, there¬
fore, it is practically impossible to keep the creatinine for any considerable
length of time. This suggestion is of interest and of importance because it
points to the possibility of the composition of freshly voided urine being due
not solely to the constituents secreted but to a chemical change towards an
equilibrium which takes place before the urine is voided. Thus, it is more
than likely that when one is dealing with the composition of urine from
such animals, one must consider that the reaction of the urine before it is
voided and the length of time it remains in the bladder will affect the actual
chemical nature of the excreted liquid. A striking point in connection with
the creatine is that throughout the fasts with steers E and F there was a
continual excretion, which was contrary to the finding with steers C and D.
One explanation may be that the reserve stores of these two animals, E and
F, were not sufficient to supply an adequate portion of the energy due to
carbohydrate and fat, so that these two younger animals gradually had to
call upon their store of protein and this disintegration of tissue resulted in
the liberation of creatine.
OTHER URINARY CONSTITUENTS
For a detailed discussion of the various forms of sulphur, phenols, acid
bodies, fixed bases, and organic acids reference must be made to Dr. Car¬
penter’s more complete treatment of these data. Extraordinarily small
amounts of phosphorus were found, so that excretion of phosphorus in the
urine can hardly be considered of any significance in the fasting steer. The
phenols, which serve as indications of a putrefactive change along with the
ethereal sulphates, decrease rather rapidly as the fast progresses, although
it is to be borne in mind that there are a number of putrefactive changes in
the intestinal tract for a considerable time after the last feed has been given.
The acid bodies, acetone and diacetic acid, and /?-oxybutyric acid, were
present under practically all conditions, but frequently only in traces. The
important thing is that these acid bodies were likewise noted on food days,
and hence the conclusion is reached that fasting, contrary to the conditions
with humans, does not alter the excretion of these bodies with steers.
TOTAL NITROGEN EXCRETION PER KILOGRAM OF BODY-WEIGHT PER 24 HOURS
In the consideration of these fasts thus far particular stress has been laid
upon the influence of the fast upon the nitrogen excretion from hour to hour
as the fast progresses. These animals had varying body-weights, steers C
and D being larger than the younger steers, E and F. The nitrogen excreted
122
METABOLISM OF THE FASTING STEER
per kilogram of body-weight is therefore of interest. With the two large
animals, C and D, the nitrogen-level is much the same. In the case of steer
C, for example, the values vary from as high as 0.237 to as low as 0.074 gm.
at the end of the tenth day in the fast in January 1922, and in the April
fast of 1922 a value as low as 0.073 gm. was found on the tenth day. The
values noted in the fasts at the submaintenance level are much lower than
those in the fasts at the maintenance level. Indeed, with steer C a very low
value of 0.032 gm. is noted in the March fast, the highest value being 0.067
gm. Similarly, with steer D, very low values are observed during the March
fast following submaintenance feeding, the lowest value being 0.042 gm.
With the younger animals, E and F, the nitrogen per kilogram of body-
weight per 24 hours during the fasting period is perceptibly high and has a
distinct tendency to increase as the fast progresses. Contrary to the obser¬
vations on the larger steers, this suggests that the reserves in the smaller
animals were not so great, and consequently the demand for energy supply
was met by an increasing utilization of body protein. This belief is con¬
firmed by the fact that the taking of food greatly decreases the excretion
of nitrogen per kilogram of body-weight per 24 hours. Thus, in the case of
steers C and D there was a slight decrease after the ingestion of food, and
with steers E and F there was a noticeable decrease.
CREATININE COEFFICIENT
The relationship between the total amount of preformed creatinine and
the body-weight of the animal has attained considerable importance, that
is, the actual number of milligrams of preformed creatinine per kilogram of
body-weight per 24 hours. This relationship has been computed for the
four fasts in 1924 at the submaintenance level, and has been found to remain
relatively constant throughout the fast. In the case of steer C, 27.2 mg. of
preformed creatinine were excreted per kilogram of body-weight per 24 hours
on the day before the fast, March 2-3. On the first day of the fast this
ratio fell to 21 mg. and was relatively constant throughout the fast. Dur¬
ing the two days following the fast there was likewise no appreciable
alteration. Indeed, with both animals the creatinine coefficient was reason¬
ably constant when computed on the basis either of preformed creatinine or
total creatinine. With the younger steers, E and F, however, although the
preformed creatinine per kilogram of body-weight remains essentially con¬
stant, the coefficient for the total creatinine becomes appreciably higher as
creatine is excreted. The two younger animals agree between themselves,
but show distinctly higher coefficients than do the two adult animals.
THE NITROGEN ECONOMY OF STEERS
Unfortunately, the method for determining hippuric acid is really a
method for determining benzoic acid. Consequently, we do not know
whether there may not have been a hydrolysis of the hippuric acid in the
bladder, so that free amino-acid was formed and subsequently determined
in the amino-acid determination. If this amino-acid was not free, but was
combined with the benzoic acid, then besides free amino-acid considerable
amounts of nitrogen were eliminated in the form of combined amino-acid
with the benzoic acid. Because of the low digestibility of many of the feed-
URINE
123
stuffs, particularly the roughage and grasses used by herbivora, and because
of the relatively large amounts of nitrogen liberated in the form of amino-
acid, whether free or combined with benzoic acid, the efficiency of the
utilization of nitrogen by the steer is extremely low. Consequently, as a
source of obtaining protein economically from the nitrogen cycle, these
animals are seemingly very inefficient. When the formation of protein or
the addition of muscle, or protein storage, is the main object of feeding, it
seems from the results of these urine analyses that it is of the highest
importance to know what proportion of the nitrogen escaped into the urine
in a form which was not available for metabolic processes, namely, in the
amino-acid form and as hippuric or benzoic acid combined with amino-acid.
It therefore should be important to determine which type of ration results
in the more economical use of the protein ingested, a ration composed only
of roughages, such as hays and grasses, or a ration composed of a roughage
combined with a grain or meal mixture.
Studies are needed in which the hippuric acid as such is determined, as
well as the benzoic acid, in order to determine whether it is eliminated in
the combined or free form, together with the determination of amino-acid as
such by the regular amino-acid method. These animals were on an
extremely low nitrogen-level. Possibly with a higher nitrogen-level a larger
proportion of nitrogen might be eliminated as urea and relatively less as
amino-acid and hippuric acid. It can be seen from the course of the per¬
centage distribution, however, that as the animal tends to live more and
more on its own body-substance, the composition of the urine and the dis¬
tribution of the urinary nitrogen become more like that in the human being.
It would seem that the nearer the ruminant was to its natural condition of
food intake, proportionately greater was the loss in nitrogen in forms which
had not undergone metabolic changes or had not become an integral part
of the body.
GENERAL CONCLUSIONS WITH REGARD TO THE COMPOSITION OF STEER’S URINE DURING FASTING
Prior to fasting, herbivorous animals are subsisting upon a ration strik¬
ingly different from the body substances. During fasting the large ballast
in the alimentary tract supplies certain materials for some time, but as the
ballast becomes exhausted, the animal gradually begins to subsist solely
upon its own tissue deposits and hence, in a certain sense, becomes a carniv¬
orous animal. During the considerable period of time, possibly 7 days, when
the ballast is passing through the alimentary tract, the animal is gradually
changing from a condition in which it existed entirely on vegetable food to
one of fasting, i. e., subsisting solely on its own body-tissue. At the begin¬
ning the urine is alkaline. Gradually, however, its high alkalinity disap¬
pears, and in general after 4 or 5 days the urine reacts acid to litmus paper.
During this period the most marked change in the character of the urine is
in the distribution of the nitrogen. At first, owing to the preponderance of
food residue in the intestines, the materials in the urine are derived in part
directly from the food. With ruminants one of the most characteristic of
these materials is hippuric acid, but as the effect of the previous food disap¬
pears, the hippuric acid greatly diminishes. On the contrary, urea, which
is found in the urine of humans and carnivora in a much higher percentage,
124
METABOLISM OF THE FASTING STEER
is very low in steer’s urine when he subsists on food, and one of the first
striking changes in steer’s urine during fasting is a reversal of the propor¬
tions between these two constituents, that is, a lowering of the nitrogen due
to hippuric acid and a gradual increase in the nitrogen due to urea. In the
fasts at the submaintenance level the percentage values for urea finally
approach those found for the urines of man. These figures, together with
the estimate of a comparable nitrogen figure per 24 hours for man, indicate
that the animals were on a very low nitrogen plane, due to the submain¬
tenance feeding. A further indication of the low nitrogen-level is suggested
by the relatively high percentage of nitrogen due to creatinine. The quan¬
titative elimination of preformed creatinine, as Folin has shown,0 is inde¬
pendent of the nitrogen-level; therefore, the lower the nitrogen-level the
higher is the percentage of preformed creatinine nitrogen. Thus, in the fasts
of steers C and D after pasture in November 1923, the preformed creatinine
nitrogen was from 5 to 9 per cent of the total nitrogen excretion. In the
March fasts at the submaintenance level it was from 12 to 27 per cent, but
the amounts per hour were nearly the same in these two fasts with each
steer. Likewise the amino-acid was relatively high at the start, and then
fell to a low figure.
Another feature of the urines of these herbivora during fasting is the very
low ammonia- content. Man develops acidosis during fasting, but herbivora
do not, for they excrete extraordinarily small amounts of acetone bodies and
/?-oxybutyric acid. Even the younger animals, E and F, show a similar
resistance to the effect of fasting, so far as the development of acidosis and
ketonuria is concerned. The respiratory quotients of these animals, as will
be seen later (see pp. 157 to 161), approached the quotient indicating a com¬
bustion of pure fat, hence seemingly an ideal condition for the development
of ketonuria. Obviously, it is not a universal biological phenomenon that
ketone bodies are developed when the proportion of carbohydrate to fat is
low. This has great significance in the study of the keto and anti-ketogenic
ratio, such as is being applied clinically with man. Dr. Carpenter suggests
that it may be questioned whether the cause of and development of ketosis
on the part of man is due to the low proportion of carbohydrate or is due to
the character of the material which is drawn upon when the carbohydrate
in the diet is diminished. It is difficult to understand why man should differ
in this respect from other animals, which in their metabolism show other
characteristics which are similar to those noted with man. The problem
really demands attention from a standpoint other than that of the pure
relationship of carbohydrate to fat.
In comparing these experiments on steers with those on obese humans it
seems that the ability to use fat and not develop acidosis is present when
there is a low nitrogen excretion. This is in full conformity with Petren’s
experience with diabetics on diets high in fat and low in protein.* 6 The
question arises as to whether the utilization of fat, in protein and carbo¬
hydrate withdrawal, is not actually favored by a low nitrogen-level.
The proportion of total nitrogen excreted as creatinine may be used as an
indication of the nitrogen-level, that is, the lower the proportion of nitrogen
“ Folia, Am. Journ. Physiol., 1905, 13, p. 84.
6 Petr6n, Proc. XI Internat. Physiol. Congress. 1923; ibid., Diabetes-Studier, Copenhagen,
1923.
UEINE
125
Table 31. — Total nitrogen loss during fasts of 5 to 14 days1
Date
Steer C
Steer D
Nitrogen
in
urine
Nitrogen
in
feces
Total
nitrogen
loss
Nitrogen
in
urine
Nitrogen
in
feces
Total
nitrogen
loss
1921
gm.
gm.
gm.
gm.
gm.
gm.
Nov.
26 to Dec. 6 .
(59.4)
(57.5)
Dec.
6- 7 .
64.7
(62.6)
127.3
49.3
(71.8)
121.1
Dec.
7-8 .
60.0
(26.3)
86.3
50.7
(18.2)
68.9
Dec.
8-9 .
81.5
(21.2)
102.7
48.3
(7.3)
55.6
Dec.
9-10 .
42.3
(6.0)
48.3
61.2
(14.8)
76.0
Dec.
10-11 .
50.8
(6.4)
57.2
*32.7
(6.0)
38.7
Dec.
11-12 .
55.5
(5.8)
61.3
53.1
(8.8)
61.9
Dec.
12-13 .
42.7
(4.6)
. 47.3
50.7
(6.9)
57.6
Total .
397.5
(132.9)
530.3
346.0
(133.8)
479.8
1922
Dec.
22 to Jan. 4 .
(95.5)
(101.5)
Jan.
4-5 .
123.0
65.1
188.1
122.0
61.0
183.0
Jan.
5-6 .
118.0
26.2
144.2
89.9
28.4
118.3
Jan.
6-7 .
89.8
14.5
104.3
85.4
11.1
96.5
Jan.
7-8 .
44.2
6.6
50.8
66.8
8.4
75.2
Jan.
8-9 .
66.9
8.1
75.0
57.0
7.4
64.4
Jan.
9-10 .
62.3
6.2
68.5
49.9
5.2
55.1
Jan.
10-11 .
37.1
6.5
43.6
55.7
6.9
62.6
Jan.
11-12 .
43.6
3.5
47.1
37.8
4.9
42.7
Jan.
12-13 .
30.4
2.9
33.3
32.2
4.0
36.2
Jan.
13-14 .
44.7
3.1
47.8
35.6
3.0
38.6
Total .
660.0
142.7
802.7
632.3
140.3
772.6
Mar.
31 to Apr. 17 .
(72.3)
(76.7)
Apr.
17-18 .
78.2
60.7
138.9
91.1
63.6
154.7
Apr.
18-19 .
75.2
23.8
99.0
88.9
22.4
111.3
Apr.
19-20 .
67.8
16.0
83.8
78.7
16.4
95.1
Apr.
20-21 .
78.6
12.3
90.9
71.1
12.7
83.8
Apr.
21-22 .
57.9
8.2
66.1
62.3
4.8
67.1
Apr.
22-23 .
63.9
8.3
72.2
56.5
9.3
65.8
Apr.
23-24 .
42.9
5.3
48.2
38.9
6.1
45.0
Apr.
24-25 .
48.8
8.1
56.9
44.0
5.1
49.1
Apr.
25-26 .
52.3
3.7
56.0
38.3
4.6
42.9
Apr.
26-27 .
34.3
2.6
36.9
45.1
3.9
49.0
Apr.
27-28 .
51.9
7.1
59.0
35.0
4.3
39.3
Apr.
28-29 .
36.3
4.0
40.3
37.3
3.7
41.0
Apr.
29-30 .
39.7
3.9
43.6
35.8
3.0
38.8
Apr.
30-May 1 .
47.2
3.5
50.7
33.9
2.2
36.1
Total . . .
775.0
167.5
942.5
756.9
162.1
919.0
May
9 to June 1 .
(80.0)
(82.7)
June
1-2 .
100.0
68.6
168.6
93.8
61.7
155.5
June
2-3 .
103.0
32.9
135.9
96.2
27.5
123.7
June
3- 4 .
80.5
19.0
99.5
88.1
20.8
108.9
June
4- 5 .
62.0
7.2
69.2
66.1
7.1
73.2
June
5-6 .
60.8
9.3
70.1
62.9
10.2
73.1
Total .
406.3
137.0
543.3
407.1
127.3
534.4
1 Values in parentheses are based upon analyses of composite samples; all others are based
upon daily samples.
1 Some urine lost; amount not known.
126
METABOLISM OF THE FASTING STEER
Table 31. — Total nitrogen loss during fasts of 5 to 14 days 1 — Continued
Date
Steer C
Steer D
Nitrogen
in
urine
Nitrogen
in
feces
Total
nitrogen
loss
Nitrogen
in
urine
Nitrogen
in
feces
Total
nitrogen
loss
1922
gm.
gm.
gm.
gm.
gm.
gm.
Nov. 6- 7 .
2 99.0
47.2
146.2
99.4
47.0
146.4
Nov. 7-8 .
100.6
27.9
128.5
91.6
23.1
114.7
Nov. 8- 9 .
59.4
15.6
75.0
93.3
21.6
114.9
Nov. 9—10 .
94.5
13.6
108.1
80.0
6.5
86.5
Nov. 10-11 .
80.0
7.7
87.7
86.0
14.3
100.3
Nov. 11-12 .
49.3
6.4
55.7
71.3
4.7
76.0
Nov. 12-13 .
73.4
6.1
79.5
*47.8
14.3
62.1
Nov. 13—14 .
66.5
11.2
77.7
54.5
1.6
56.1
Nov. 14—15 .
72 0
7 1
79 1
Total .
694.7
142.8
837.5
623.9
133.1
757.0
1923
Nov. 5- 6 .
87.0
(63.4)
150.4
81.0
(63.2)
144.2
Nov. 6— 7 .
95 4
(38 3)
133 7
91 7
(28 6)
120 3
Nov. 7- 8 .
78.1
(18.4)
96.5
80.5
(13.9)
94.4
Nov. 8- 9 .
63.6
(11.3)
74.9
73.3
(15.7)
89.0
Total .
324.1
(131.4)
455.5
326.5
(121.4)
447.9
1924
Mar. 3- 4 4 .
15.6
20.3
35.9
18.8
* (19.7)
38.5
. Mar. 4— 5 .
1
f 31.2
8 (16.5)
47.7
Mar. 5- 6 .
i6 102.9
*34.0
8 136.9
j 34.1
14.4
48.5
Mar. 6— 7 .
j
[ 35.8
5.5
41.3
Mar. 7— 8 .
40.2
6.5
46.7
51.2
7 (8 . 9 )
60.1
Mar. 8- 9 .
37.3
1.1
38.4
42.5
7 (3 . 5 )
46.0
Mar. 9-10 .
40.4
4.8
45.2
45.4
4.9
50.3
Mar. 10-11 .
38.7
3.9
42.6
37.1
6.0
43.1
Mar. 11-12 .
39.0
2.3
41.3
41.1
3.6
44.7
Mar. 12—13 .
29.7
8 0 0
29.7
Total .
343.8
72.9
416.7
337.2
83.0
420.2
1 Values in parentheses are based upon analyses of composite samples; all others are based
upon daily samples.
s Some urine lost; amount not known.
3 About 200 gm. urine lost.
4 Mar. 3-4 represents a 17-hour period from 2;p. m., Mar. 3, to 7 a. m., Mar. 4; all other days
in this fast begin and end at 7 a. m.
1 Based on composite sample for Mar. 3 to 5.
* Data for Mar. 4 to 7 combined, because analyses of urine and feces were not made in exact
24-hour periods during this time.
7 Based on a composite sample for Mar. 7 to 9.
8 There were no defecations between 7 a. m., Mar. 12, and 7 a. m., Mar. 13, but 0.62 kg.
feces were passed between 7h 10m and 10h 25m a. m., Mar. 13, before the steer was fed ; nitrogen
content 2.38 gm.
as creatinine the higher is the nitrogen-level. Steers E and F were on an
appreciably higher plane in this regard than were steers C and D. On the
other hand, the creatinine coefficient may be taken as an indication of the
reserve material, that is, as an indication of whether the animal is fat or
lean, because the fatter the animal the lower will be this coefficient.
Although it is in the realm of speculation, one may surmise that the appear¬
ance of creatine may be taken as an indication of the inability to utilize the
store of fat on hand or the lack of fat of an adequate chemical composition.
NITROGEN LOSS
127
NITROGEN LOSS
Total Nitrogen Excreted in Urine per Day and During the Entire
Fast
From the physiological standpoint, the interest in the chemical compo¬
sition of the urine at the present day far exceeds that in the urinary nitrogen
loss, which for years served as the only chemical index of protein disintegra¬
tion. The chemistry of the urine, however, deals for the most part with the
nature of the substances analyzed and their relative proportions in the
urine, and the total urinary nitrogen still remains the best index of the total
protein disintegration. Hence special consideration was given to the total
nitrogen excreted in the urine in relation to the previous state of nutrition,
the length of the fast, and the age of the animal. The total nitrogen was
determined in the weights of urine shown in Table 27 (p. 100) , secured in
the conventional 24-hour periods. As pointed out in the discussion of this
table, however, these weights do not represent exactly the urine excreted for
24 hours, but simply the actual voidings occurring between the beginning
of the experimental day and approximately 24 hours from that time. In
the discussion of the chemistry of the urine this inequality in time is in large
part compensated by referring all the urinary excretions to the per hour
basis, but for the purpose of studying the protein disintegration it seems
best to consider the total urinary nitrogen excretion in 24 hours, notwith¬
standing the defect in the 24-hour separation and collection.
The 24-hour amounts of nitrogen excreted in the urine have therefore been
given in Tables 31 and 32 for each day of the long fasts as well as the
average 24-hour values for the preceding feed-periods. (See also Tables 28,
and 29, pp. 108 and 111, for details of exact duration of the period of collec¬
tion.) The data for the feeding-periods are separated from those for the
fasting-periods by horizontal rules.
Table 32. — Total nitrogen losses of steers E and F during fast in February 1924
Date
Steer E
Steer F
Nitrogen
in
urine
Nitrogen
in
feces1
Total
nitrogen
loss
Nitrogen
in
urine
Nitrogen
in
feces1
Total
nitrogen
loss
1924
gm.
gm.
gm.
gm.
gm.
gm.
Feb. 11-12 .
19.8
20.6
Feb. 12-13 .
13.8
(11.4)
25.2
2 10.8
(15.4)
26.2
Feb. 13-14 .
24.6
(13.1)
37.7
20.2
(8.5)
28.7
Feb. 14-15 .
22.2
(7.4)
29.6
22.2
(8.9)
31.1
Feb. 15-16 .
36.4
(3.9)
40.3
32.0
(4.9)
36.9
Feb. 16-17 .
26.6
(1.6)
28.2
35.5
(2.7)
38.2
Feb. 17-18 .
.
.
32.0
(1.9)
33.9
Total .
123.6
(37.4)
161.0
152.7
(42.3)
195.0
1 Based on analysis of composite sample for Feb. 12 to 18. In the case of steer E this sample
included the feces passed on the first day on feed after the fast.
s About 10 ounces of urine lost during the day. ■
128
METABOLISM OF THE FASTING STEER
Prior to the fasts, the average daily excretion of urinary nitrogen by steers
C and D in the feed periods other than at the submaintenance level varied
from 57.5 to 101.5 gm. Inasmuch as both animals received exactly the same
treatment, the variations are much the same with both. The lowest value
during the feed periods occurred prior to the fast in December 1921, and the
highest prior to the fast in January 1922. In the pasture periods nitrogen
determinations were not feasible. On March 2-3, at the submaintenance
level prior to the fast in March 1924, a low amount of 30 gm. was observed
on the average with each animal.
The total loss of nitrogen from the body during a fast will in all prob¬
ability be determined in large measure by the level of the nitrogen metabo¬
lism at the start of the experiment. In those experiments following pro¬
longed undemutrition it has been noted with man that an appreciable part
of the body nitrogen may be lost as a result of undernutrition; in other
words, there is a continuous negative balance. When a fast is started at a
low nitrogen-level, obviously the drafts due specifically to the fast are less
than when the fast is started at a higher level. Emphasis in the following
discussion is therefore laid upon the fasts which followed maintenance
feeding.
On the first day of fasting following maintenance feeding there was in all
cases but one an increase in the urinary nitrogen of steers C and D as com¬
pared with the average value before the fast. In the fast in December 1921,
steer D, however, actually excreted 8 gm. less. The increase was very large
with steer C in the January 1922 fast, amounting to nearly 30 grams. Until
the third day the 24-hour nitrogen excretion remained fairly constant, but
usually decreased rapidly after the third day. In the discussion of the
chemistry of the urine it was pointed out (see p. 115) that the minimum
nitrogen excretion of steers C and D was not far from 40 grams per 24 hours.
This excretion corresponds essentially to that of man on a nitrogen-free
diet. The constancy in the daily amounts in the last part of each fast is
striking.
The total amount of nitrogen lost from the body in the urine during each
of these different fasts is likewise recorded in Tables 31 and 32. Naturally
the larger amounts were lost during the longer fasts, and it can be seen
that the 14-day fast made a considerable draft upon the protein store of
steers C and D. On the assumption that each gram of urinary nitrogen lost
from the body represents 6.25 gm. of dry protein (the conventional factor),
the maximum draft upon dry protein was 4.84 kg. in the case of steer C
and 4.73 kg. in the case of steer D. In both instances, as is to be expected,
this maximum draft occurred in the 14-day fast. Multiplication of the
amount of dry protein by the factor commonly used for the conversion of
protein to flesh, i. e., 4.0, shows that steer C lost 19.4 kg. of flesh and steer
D lost 18.9 kg. This method of computation follows the older usage of
ascribing the entire urinary nitrogen loss to muscle-tissue, and although this
method is obviously incorrect, it gives a hint as to the actual weight of
nitrogen lost in the breakdown of protein. Since chemical analyses of the
bodies of these animals were not made, a computation of the percentage loss
of total protein is hardly significant, owing to the variations in the propor-
NITROGEN LOSS
129
tion of protein in the body and particularly to the fact that these animals
were subjected to numerous intermittent fasts and were on various feed
levels. It can be seen, however, that there was a substantial draft upon the
body-tissue during the 14-day fast.
Total Nitrogen Loss During Fasts of 5 to 14 Days
Although the nitrogen in the urine particularly represents protein metabo¬
lism and the nitrogen in the feces supposedly unabsorbed nitrogen of food,
we have already seen (p. 123) that in the urine at least hippuric-acid nitro¬
gen and amino-acid nitrogen may not represent protein disintegration, but
simply a path for the excretion of food nitrogen, which has actually not
been metabolized. Similarly, it is not inconceivable that certain nitrogenous
products in the feces, formerly grouped under the general head of “metabolic
fecal nitrogen,” may in the case of humans represent actual metabolic trans¬
formations. With these reservations it may be maintained that the nitro¬
gen of urine represents the disintegration of protein, and the nitrogen of
feces unabsorbed feed nitrogen. Considering the animal at the beginning
of the fast as a unit consisting of its organized body-tissue plus the contents
of its intestinal tract, one may note the total loss of nitrogen from this unit
during the period of fasting by summing the nitrogen lost in the urine and
that lost in the feces, without attempting to differentiate between the
urinary and fecal nitrogen on the basis of metabolized or non-metabolized
nitrogen. Such computations have likewise been recorded in Tables 31
and 32.
During the fasts in December 1921, November 1923, and February 1924,
the fecal nitrogen was determined only for the entire period of the fast and
the amount of nitrogen has been apportioned between the different days
upon the basis of the fresh weight of feces passed daily, on the assumption
that the percentage of nitrogen in each day’s feces was the same throughout
the entire fasting-period. This assumption is probably not justified, although
in lieu of daily nitrogen determinations it may be used here tentatively.
The same treatment has been given to the data for fecal and urinary nitro¬
gen in the feed-periods preceding the fasts, and to certain data in the fasts in
March 1924. The values thus computed have been inclosed in parentheses.
The nitrogen loss due to epidermal tissue and hair, which is a measurable
amount, has not been estimated, although Armsby and, indeed, before him
Grouven, took such loss into consideration.
In the fast in April 1922, steers C and D each lost over 900 grams of
nitrogen. As is to be expected, the total loss varies again with the length
of the fast and particularly with the character of the ration prior to the
fast. Thus, since steers C and D had undergone a loss of nitrogen when
receiving submaintenance rations prior to the fasts in March 1924, their
total daily loss of nitrogen during these fasts averaged not far from 40
grams. Essentially the same loss was noted after the eighth day of fasting
following maintenance feeding. During the fasts of steers E and F in
February 1924, the total loss of nitrogen was approximately 30 grams per
day with each steer, indicative not only of similar body-weights but likewise
of the submaintenance level of nutrition.
130
METABOLISM OF THE FASTING STEER
Our data are wholly inadequate for the study of the recovery after fast¬
ing and the rapidity of nitrogen retention, as our main problem was the
course of the metabolism during complete fasting. Substantial losses of
nitrogen are experienced by steers when fasting, even when the normal
nitrogen storage has been considerably depleted by the prolonged use of a
submaintenance ration.
BODY MEASUREMENTS, GENERAL BODY CONDITIONS, AND
PHYSIOLOGICAL FUNCTIONS
Body Measurements
General body measurements were taken before and after the fasts of five
or more days’ duration. In addition, three different body circumferences,
namely, around the paunch, the flank, and the chest, were measured daily
during the entire experimental season. The measurements obtained at the
beginning and end of the fasts are of special interest, as they indicate
whether any marked changes have occurred that might possibly have a
significant correlation with loss of body-tissue and conceivably also with
changes in body-surface area. As a typical illustration, the general body
measurements secured at the beginning and end of the 14-day fast in April
1922 are recorded in Table 33. Since this was the longest fast, these data
will obviously indicate the maximum variations noted in the size of the
measurements due to fasting.
The only body measurements which show a significantly large decrease
during fasting are the circumferences of the middle part of the body, some¬
times termed the “barrel.” In the order of magnitude the shrinkage is
greatest at the paunch, slightly less at the flank, and materially less at the
chest. In other words, the shrinkage at paunch and flank reflects largely
the loss in fill, the chest circumference being but slightly affected by this
loss. These measurements are therefore of value chiefly because they might
conceivably be used as a crude basis for estimating the change in surface
area. The body-length changes but little. Since it is evidently one of
the dimensions which furnish fairly distinct landmarks for repeated meas¬
urements, it may prove a useful measurement in connection with some of
the more recent formulas for determining surface area. The other dimen¬
sional measurements have no particular value as indicators of shrinkage
during fasts not exceeding 14 days in length, because for the most part it
is difficult to obtain duplicate readings successively, the error introduced
thereby often exceeding the most probable actual change. They are valua¬
ble only in giving a general idea of the size and proportions of conformation
of the animal.
Special emphasis was laid upon the measurement of the chest-girth, for
it had been noted in an earlier study of undernutrition in steers that the
chest-girth was influenced the least by changes in fill and that a change in
this girth more truly represented an actual alteration in the state of flesh.
Hence changes in chest circumference are of far more significance quanti¬
tatively than changes in body-weight. Obviously, in making this measure¬
ment, care must be taken to have the traction on the measuring tape or
chain uniform, and it is preferable to have the same observer make the
BODY MEASUREMENTS AND PHYSIOLOGICAL FUNCTIONS 131
measurements from day to day, to insure both the uniform traction and
the exact location of the tape.
Table 33. — General body measurements at the beginning and end of the 14-day fast
Measurement
Steer C
Steer D
Start
End
Difference
Start
End
Difference
Body circumferences:
cm .
cm.
cm.
cm.
cm.
cm.
Chest .
198.0
193.0
5.0
208.5
200.5
8.0
Paunch .
228.5
200.5
28.0
228.5
208.5
20.0
Flank (rear) ....
198.0
172.0
26.0
200.5
183.0
17.5
Chest width .
52.5
47.0
5.5
53.0
50.0
3.0
Chest depth .
75.0
72.0
3.0
79.0
79.0
0.0
Width at hips .
57.0
54.5
2.5
62.5
58.0
4.5
Body length1 .
160.0
157.5
2.5
165.0
162.5
2.5
Fore leg length. .....
82.0
77.5
4.5
84.5
83.0
1.5
Hind leg length .
96.0
95.0
1.0
99.0
99.0
0.0
1 Measurement from second dorsal vertebra to pin-bone.
The measurements of the chest circumference secured during the fasting
experiments of 5 to 14 days are recorded in Table 34, and, for purposes of
comparison, the measurements secured on the three food days just prior
to the fasts are also given. It can be seen that the normal variation in
this measurement to be expected from day to day during feeding usually
is not far from 2 to 3 cm., although before the April fast of steer C and
the December fast of steer D a variation of 4 cm. was noted. Shortly after
the beginning of the fast there is a decrease in the chest-girth, and this
decrease continues as the fast progresses, although it is by no means
uniform. Thus, in the 14-day fast, the chest circumference of steer C
decreased from 198 cm. at the start to 193 cm. at the end, that is, there
was a total shrinkage of 5 cm. Steer D, in the corresponding fast, lost
9 cm. On the other hand, in the fast after pasture in November 1922, the
chest circumference of steer C decreased from 211 to 203 cm., a change of
8 cm. With the young animals which fasted not over four to five days
after submaintenance feeding, the changes in chest circumference were
hardly outside the range of the normal error of observation. Therefore,
although, theoretically at least, the chest circumference should be a fairly
good index of the state of nutrition and the loss of flesh, practically it
serves only as a general index and can not be considered as a quantitative
index, even in a fast of from 10 to 14 days.
Each of the entries in this table represents the chest circumference at
the beginning of the day. Records were also made at the end of the last
fasting day. These, with one exception, show either no change or a decrease
of only 1 cm. as compared with the circumference at the beginning of the
last day. At the end of the January fast of steer D there was a decrease
of 3 cm., from 206 to 203 cm. Thus there was no measurable loss during
the last day of fasting.
The experience in using the chest circumferences in the earlier study of
undemutrition in steers had led to the belief that this was an important
Table 34. — Chest circumferences prior to and during fasts of 5 to 14 days1
132
METABOLISM OF THE FASTING STEER
1 The chest circumferences of steers C and D were measured at 2 p. m., those of steers E and F at 7b30m a. m. As recorded in this table, they
represent measurements secured at the beginning of each day.
BODY MEASUREMENTS AND PHYSIOLOGICAL FUNCTIONS 133
physical measurement, which would give an index of the state of nutrition
of the animals. It is much to be regretted that a good index of the state
of nutrition comparable to the numerous indices of state of nutrition now
available for humans is not yet available for animals. The personal equa¬
tion of the experienced judge will still have to be allowed to enter into
every estimate made, until a series of girths or lengths or ratios to weight
can be agreed upon by the majority of livestock judges, which will possibly
put this important estimate upon a mathematical basis. Such experience
as is outlined in Table 34, however, is disconcerting, and it is clear that
one measurement alone may not be considered as appropriate for such an
index. No attempt has been made to combine this measurement with
lengths or with weights or with any functions of body-weight, since the
quantitative expression of the state of nutrition of animals is still unsettled.
General Body Conditions
During each of the fasts a daily record was kept of all incidents relating
to the general appearance and behavior of the fasting animal, and particular
note was made of such reactions as could not be measured or expressed in
terms of concrete data. These observations are summarized under two
heads, the effect of fasting on general behavior and the effect of fasting
on physical appearance.
General Behavior of Fasting Steers
With humans, particularly in the lay mind, the idea of fasting is always
inseparably interwoven with food shortage under enforced conditions, and
it therefore implies hardships and suffering. In animals the actual sensa¬
tions, if any, resulting from lack of food are not obscured by the capacity
to reason, and their general behavior is therefore more truly an expression
of the physical sense of uneasiness resulting from lack of food. In a study
of steers during prolonged undernutrition0 it was found that when the
ration was reduced from a maintenance ration to one about half sufficient
for maintenance, the steers showed some nervous irritation for a few days,
after which those on submaintenance showed no more eagerness for food
than did the steers which were still on full rations. The general deduction
is that the so-called “hunger feeling” is merely the temporary sensation
caused by the physical contraction of the alimentary tract to meet the
requirements of a diminished bulk, but in no sense represents distress due
to a lack of nourishment to the tissues.
Disposition and behavior — During the fasting experiments there was
always some protest from the animals when the first feed was withheld.
This was made manifest by a continuation of the usual signs which cattle
exhibit at feeding-time. In other words, they were apprehensive and
uneasy for several hours beyond the time when feed would normally have
been given, at times lowing and showing general nervous irritation at being
thus apparently neglected. As a rule, they behaved very quietly by the
second day, showing no particular sign of uneasiness, irritation, or craving
for food except after drinking, when at times they repeated their exertions
•Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 176,
134
METABOLISM OF THE FASTING STEER
up to the fifth or sixth day, although less and less persistently than on the
first day. Their placid and indifferent attitude after the first day of fasting
was, in fact, a surprise. On the whole, these fasting steers seemed to adjust
themselves temperamentally to an entire lack of food even more readily
than was the case with steers which were fed only half a maintenance
ration. Previous to the beginning of the 14-day fast, when steers C and D
were on a ration containing 9 kg. of hay and 3 kg. of meal (equal parts
by weight of com meal, linseed meal, and bran), they were very restless
and acted anxious for food at meal time. On the afternoon of the first
day, when their first meal was withheld, they exhibited this symptom to
a marked extent. On the second day, although they still showed a tendency
to nervousness from lack of food, they were somewhat more quiet and
seemed to spend less time standing than when on feed. By the end of the
second day they were very quiet and inactive and remained so during the
rest of the fast, showing no particular irritation or craving for food.
Vigor — Loss in vigor due to prolonged undernutrition or to malnutrition
in livestock is usually accompanied by a dull, listless expression. Bright¬
ness of eye and of general expression, on the other hand, is ordinarily
considered a characteristic mark of vigor and particularly of good health.
If these commonly accepted expressions have any basis of fact, then a
dull, listless expression may be considered as a danger signal, suggesting
that health is being impaired or undermined. In no case of fasting did
any of these steers show any signs of a lack of vigor, judged on this basis.
At the end of the 10-day fast in January 1922, steers C and D were appar¬
ently as vigorous as on the third day, and even at the end of the 14-day
fast they were still as active and alert as ever, when taken outdoors to be
photographed. Both animals stood up for much shorter intervals as the
fasts progressed, but they seemed to rise with apparent ease, showing no
particular weakness in this respect, even at the end of the 14-day fast.
During this fast they did, however, relax more on going down, performing
the last part of the operation with more or less of a drop, due no doubt
in part to the fact that they had been confined in stalls for about 5 months
and were somewhat stiff from lack of exercise. In general, they both
appeared as strong and vigorous, even on the last day of the 14-day fast,
as in the early stages of fasting, their eyes being bright, indicating that
health or vigor had been in no wise impaired.
Muscular activity — The close correlation between muscular activity and
metabolism, observed so frequently with humans and likewise pointed out
with animals, made direct comparative records of muscular activity an
essential part of our technique. With stall-fed steers, practically the only
pronounced activity is that of getting up and lying down. These changes
of position were indicated in the laboratory room by means of a small
weight attached to one end of a cord running over pulleys, the other end
being attached to the urine harness, so that, when the animal stood up,
it would be instantly indicated and the time could be recorded. Time
records of these changes of position were kept throughout the day, and in
fasting experiments throughout the night also. These records give informa¬
tion not only of the number of changes from standing to lying and vice
BODY MEASUREMENTS AND PHYSIOLOGICAL FUNCTIONS 135
versa, but likewise of the total amount of time in the 24 hours that the ani¬
mals were, respectively, standing or lying. The records- are not complete,
however, with regard to this latter phase of the observations, for such records
involve continuous observations for 24 hours throughout the entire fast,
and the pressure of other work occasionally introduced lapses in these
records. The general picture, however, indicates that the animals had a
tendency to lie down for a longer time as the fast progressed. Indeed, in
all cases the fasting steers exhibited the same tendency to conservation of
energy as was noted with the steers on undernutrition. They became more
quiet and inert in their muscular exertion and spent a larger proportion
of the time lying down and for much longer periods at a time than when
on feed. Armsby and his associates have been wont to compute the 24-hour
metabolism of their animals on the basis that the animal spent 12 hours
standing and 12 hours lying. These times represent the average times
presumably with animals on feed. These fasting steers, however, more
commonly spent 14 to 15 hours instead of 12 hours in the lying position.
Minor muscular activities also affect the metabolism considerably. In
the respiration chamber such minor muscular activity was graphically
recorded by means of the kymograph.® The kymograph records show con¬
clusively that the degree of activity decreased as the fast progressed. The
activity for the most part consisted in a shifting in the weight of the
animal’s position, usually with a remarkable degree of regularity. The
time elapsing between these shifts in weight gradually lengthened as the
fast progressed. In the long fast of 14 days steer D invariably showed a
somewhat greater activity than steer C. There was not much difference
in the number of times that the animals stood up and lay down, i. e., the
actual number of times that they shifted their position was not greatly
altered, but they remained down for a longer time.
Salivation — After the second day of fasting, steer D almost invariably
began salivation, sometimes rather profusely, and continued to salivate
up to the fifth day, but the salivation had gradually ceased by the seventh
day. The fact that none of the other three fasting steers ever exhibited
this trait showed that this was an individual characteristic. Obviously
the salivation of steer D was somehow associated with lack of food, but
the absence of other manifestations suggesting a craving for food implied
that the salivation was probably induced in part by the condition of his
teeth, as is so commonly the case in horses.
Rumination — After the second day rumination practically ceased,
although there were occasional evidences of it. For example, no rumination
was recorded after the fourth day, except in the 10-day fast in January,
when steer D apparently showed evidences of rumination. On the whole,
rumination persisted somewhat longer during fasts following feeding with
dry rations, having hay for a basis, than it did during fasts after grass
feeding. This would naturally be expected, as it would probably take a
longer time to saturate and prepare hay thoroughly for rumination.
Behavior during refeeding after fast— Close observation of the behavior
during the refeeding period after the fast thoroughly corroborates the
“ Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 54.
136
METABOLISM OF THE FASTING STEER
deductions drawn from their behavior during fasting. Frequently only
hay was given for the first feed, on the assumption that it would be better
at the start to supply bulk rather than highly concentrated matter. When
the first hay feed was given after a fast of 5 or more days, the steers
consumed the feed in an indifferent manner, eating intermittently and
slowly, showing no signs of avidity or eagerness, as one might suppose.
After these longer fasts their capacity or desire for any material amount
of bulk in the form of hay was apparently limited, as they usually con¬
sumed less than 2 kg. in their first feed and, when only hay was fed, from
4 to 7 days would elapse before they would again clean up a ration of hay
approximating normal maintenance. In those cases where 1,000 grams of
a concentrated meal mixture (equal parts by weight of linseed meal, corn
meal, and wheat bran) were given, the meal was cleaned up in 15 minutes,
which was still a much longer time than the steers required for this amount
under ordinary conditions of feeding. When the animals were refed on
both hay and meal, their appearance would improve within 2 or 3 days,
as the paunch again became distended and the hair smoothed down. Like¬
wise they would become more energetic, and in a week or less they would
behave and appear much the same as before the fast.
General Appearance
In all fasts the first visible effect of the lack of food is the shrinking
of the body at the paunch. In the fasts of from 2 to 5 days this shrinking
in size was confined largely to the region of the paunch, but toward the
end of the two 10-day and the two 14-day fasts a pronounced shrinking or
sinking in at the flanks also became apparent. The shrinkage at the paunch
was most marked during the first 2 or 3 days, corresponding closely to
the quantitative rate in loss of solid excreta and water of fill. After the
fasts which did not exceed 5 to 7 days in length, this shrinking in the size
of the body apparently was repaired wuthin a week, when the animals had
again acquired the capacity to consume a full ration of hay and a normal
complement of water.
Condition of flesh — Nothing is so important to the experienced stockman
in estimating the state of flesh of an animal as is visual appraisal. Weight,
length, or girth does not so perfectly express to him the true condition of
flesh of the animal. Such personal appraisal was, however, in the case
of these steers, supplemented by standard measurements of lengths and
girths. As a result of the fasts of these four animals there was no visible
indication of any loss in flesh, even after the 10-day and the 14-day fasts,
the thighs and hind quarters generally appearing as plump as before the
fast. This impression was also obtained from “handling”® or feeling the
flesh over the ribs, a butcher’s procedure. Although both steers C and D
were extremely gaunt at the end of the 10-day and the 14-day fasts, Pro¬
fessor McNutt, of the Department of Animal Husbandry of New Hampshire
College, commented on their appearance as follows:
° “Handling” is a general expression used by butchers and livestock men generally to indicate
thickness and quality of flesh.
BODY MEASUREMENTS AND PHYSIOLOGICAL FUNCTIONS
137
“The steers are in good condition, considering the length of the fast.
They have apparently lost very little flesh and still handle well, but they
have undergone considerable shrinkage due to loss of fill. I have seen cattle
undergo greater shrinkage in a 3-day shipment on cars than these two
steers show.”
Skin and hair — When animals in good flesh are well nourished, as was
the case previous to all but those fasts following submaintenance feeding,
the hair is soft, fairly glossy, and lies flat on the body, giving the impression
of sleekness. The skin is soft, pliant, and elastic to the touch or manipula¬
tion. Close daily observation and handling or feeling of skin and hair
throughout each fast indicated that the hair was particularly sensitive to
radical changes in food-supply, reacting much more quickly to lack of
nourishment than was true of the skin. Usually by the second or third
day of fasting the hair began to lose its sleekness and bristled out more
from the body, having a dusty appearance, and after 10 or more days of
fasting it became somewhat harsh or dry to the touch.® During the 10-day
and the 14-day fasts considerable shedding also took place, but since both
of these fasts occurred during the spring of the year, the cause must have
been at least partially seasonal. No particular effect on the skin was
observable, even after 5 days of fasting, but at the end of the 10-day and
14-day fasts, probably because of a lack of replacement of fat in and
more particularly under it, the skin seemed to become drier and harder
and consequently to shrink, so that it adhered more tightly.
Heart-Rate
The heart-rate is a reasonably good index of the general metabolic level.
Extraordinarily low rates have been previously reported for steers on
submaintenance rations,6 20 beats per minute being noted in the case of
one steer. Since simultaneously with the low heart-rate there was a greatly
lowered “standard metabolism” (see p. 228), it can be seen that with these
animals, as with humans, variations in heart-rate reflect approximately, at
least, the metabolic level. The importance of recording heart-rates in
studies with steers is here strongly emphasized, as this relationship between
heart-rate and metabolic activity is so prominent. The technique, how¬
ever, is by no means simple. Accurate determinations of representative
heart-rates, as well as live weights, can be secured only with the greatest
patience and care. They should be obtained by a regular attendant and
under conditions when the animal is placid or quiet and has not been
unduly excited. The animal should also not be ruminating throughout the
entire time of counting the heart-rate, since rumination increases heart
activity. The best results so far have been obtained by use of a stethoscope
placed over the heart of the animal. It is not at all unlikely that electro¬
cardiograms might be secured by attaching simple, wet electrodes to the
legs, making the electrodes a part of the regular harness. Such an arrange¬
ment would be ideal and probably would give much more normal, uncom-
° The appearance of these changes depends of course on the physical conditions in which the
animals start fasting.
b Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 193.
138
METABOLISM OF THE FASTING STEER
Table 35. — Heart-rates per minute of steers C and D, on feed and fasting
Date
Days
fasting
Steer C
Steer D
2 p. m.
4 p. m.
6 to
7h30m
a. m.
2 p. m.
4 p. m.
6 to
7h30m
a. m.
1921
Dec. 3 to 5, incl .
49
52
42
52
55
51
Dec. 6— 7 .
1
144
140
44
144
48
48
7— 8 .
2
» 32
36
136
36
Dec. 8— 9 .
3
32
36
34
36
32
40
4
32
132
36
42
Dec 10-11 .
5
38
36
38
42
1922
Jan. 1 to 3, incl .
68
61
60
70
63
64
Jan. 4— 5 .
1
*64
2 72
*48
172
2 68
152
Jan. 5— 6 .
2
48
60
i38
48
148
140
Jan. 6— 7 .
3
136
136
138
140
40
i36
Jan. 7— 8 .
4
36
136
136
40
40
‘38
Jan. 8— 9 .
5
40
136
138
138
136
‘36
Jan. 9—10 .
6
34
132
38
136
‘38
36
Jan. 10-11 .
7
* 30
32
36
132
*36
38
Jan. 11-12 .
8
132
‘28
130
36
32
38
Jan. 12-13 .
9
36
128
34
36
30
i36
Jan. 13-14 .
10
128
28
38
128
134
i27
Apr. 14 to 16, incl .
57
56
51
60
61
60
Apr. 17-18.. .
1
60
42
»62
54
50
Apr. 18-19 .
2
42
52
38
140
36
Apr. 19—20 .
3
36
132
38
136
40
Apr. 20—21 .
4
132
1 30
38
1 34
40
Apr. 21-22 .
5
38
36
34
42
30
Apr. 22—23 .
6
37
1 32
30
42
38
Apr. 23-24 .
7
36
34
30
40
36
30
Apr. 24-25 .
8
3 40
36
32
36
40
134
Apr. 25-26 .
9
30
130
34
38
132
138
Apr. 26-27 .
10
3 44
136
132
40
48
» 36
Apr. 27—28 .
11
32
36
130
40
32
132
Apr. 28—29 .
12
30
32
32
3 36
38
132
13
3 38
128
32
32
34
Apr. 30-May 1 .
14
30
134
30
32
134
132
May 29 to 31, incl .
63
61
55
71
68
65
Juno 1— 2 .
1
156
40
164
60
54
June 2— 3 .
2
44
48
140
54
140
June 3— 4 .
3
144
2 44
3 44
52
3 48
June 4— 5 .
4
34
38
32
44
42
44
June 5— 6 .
5
38
136
34
48
46
Jiitia 6— 7 .
6
48
2 33
32
Nov. 6 to 7 .
1
148
*48
Nov. 7- 8 .
2
44
40
1 38
48
1 40
Nov. 8— 9 .
3
40
3 48
44
48
3 52
Nov. 9—10 .
4
40
48
40
48
52
Nov. 10-11 .
5
40
38
40
i48
46
Nov. 11-12 .
6
138
136
136
144
142
Nov. 12-13 .
7
36
38
36
46
42
40
Nov. 13-14 .
8
38
36
36
42
138
40
Nov. 14—15 .
9
136
134
38
Nov. 15—16 .
10
36
40
36
1 Lying.
2 Lying and ruminating.
3 Just up.
BODY MEASUREMENTS AND PHYSIOLOGICAL FUNCTIONS 139
Table 35. — Heart-rates per minute of steers C and D, on feed and fasting — Continued
Date
Days
fasting
Steer C
Steer D
2 p. m.
4 p. m.
6 to
7h30m
a. m.
2 p. m.
4 p. m.
6 to
7h30m
a. m.
1923
Nov. 1 to 3, incl .
61
69
Nov. 4- 5 .
1
4 52
Nov. 5— 6 .
2
48
60
Nov. 6- 7 .
3
46
48
44
72
52
Nov. 7-8 .
4
136
42
8 48
1 56
8 56
Nov. 8— 9 .
5
136
42
8 40
52
8 56
Nov. 9—10 .
6
36
36
1 34
1924
Feb. 29 to Mar. 2, incl. . .
35
37
35
46
49
46
Mar. 3- 4 .
1
34
34
36
48
48
48
Mar. 4— 5 .
2
32
30
30
44
36
Mar. 5— 6 .
3
126
28
8 40
132
36
36
Mar. 6- 7 .
4
28
26
*28
32
34
36
Mar. 7- 8 .
5
26
124
28
36
48
8 48
Mar. 8— 9 .
6
‘26
1 30
124
‘40
1 36
Mar. 9—10 .
7
30
30
25
8 50
132
‘38
Mar. 10-11 .
8
126
26
1 28
34
136
Mar. 11-12 .
9
28
*24
30
34
Mar. 12-13 .
10
1 26
126
34
1 Lying. * Just up. 4 Taken at 8h30m a. m.
plicated results, but this method has not as yet been tested. Owing to the
much disputed quantitative differences between the metabolism of an
animal in the lying and standing positions, heart-rates recorded under
these conditions should be studied more thoroughly. Certain technical
difficulties in securing the heart-rate with the animal in the lying position
are not easily overcome, but probably electrocardiograms under these
conditions will be of much assistance in throwing light on this problem.
Colin0 states that the average heart-rate of the steer is from 45 to 50
beats per minute, as shown by a large number of observations by veteri¬
narians. Knoll,* 6 in Ellenberger’s laboratory at Dresden, found that the
heart-rate of these animals varied between 36 and 102 beats per minute,
being on the average 70 beats.
In connection with the fasts of 5 to 14 days the heart-rates per minute
of all four of our steers were determined on most of the fasting days and
in the feeding-periods preceding the fasts. Usually they were determined
at 2 p. m., 4 p. m., and some time between^ 6 and 7h 30m a. m. The data
secured on each of the fasting days, together with the average values for
3 days on food preceding each fast, are recorded in Tables 35 and 36. In
these tables special note is made of the instances when the animal was
lying, ruminating, or had just stood up at the time the heart-rate was
° Colin, Trait6 de Physiologie Comparee des Animaux, 3d ed., Paris, 1888, 2, p. 476.
6 Knoll, Untersuchungen iiber die normale Pulsfrequenz der Rinder und Schweine nebst ver-
gleichenden physiologischen kritischen Studien iiber die normale Pulsfrequenz des Menschen und
der Haussaugetiere. Inaug. Diss., Zurich, 1911, p. 40.
140
METABOLISM OF THE FASTING STEER
Table 36. — Heart-rates per minute of steers E and F, on feed and fasting
Date
(1924)
Days
fasting
Steer E
Steer F
2 p. m.
4 p. m.
7h30m
a. m.
2 p. m.
4 p. m.
7h30m
a. m.
Feb. 9 to 11, incl .
45
44
36
46
43
36
Feb. 12-13 . .
1
38
36
42
40
48
44
48
Feb. 13-14 .
2
48
36
1 40
44
36
Feb. 14-15 .
3
2 34
36
34
36
36
36
Feb. 15-16 .
4
2 34
1 48
36
38
36
32
Feb. 16-17 .
5
34
2 36
36
40
34
2 34
Feb. 17-18 .
6
36
36
36
1 Just up. 2 Lying.
observed, for such factors might have considerable influence on the
heart-rate.
Attention is first called to the average heart-rates in the food-periods
prior to the fasting experiments. In the case of steer C, in December 1921,
heart-rates of 49, 52, and 42 were noted. In January 1922, about a month
later, considerably higher rates of 68, 61, and 60 were found. In April
1922, the values are 57, 56, and 51, about intermediate between the Decem¬
ber and January values. In May the rate has again risen to 63, 61, and 55,
but the most striking change is during the submaintenance period in
February, when the values were 35, 37, and 35. Essentially the same
picture is shown with steer D, although his heart-rate tends in general to
be slightly higher than that of steer C. Indeed, even on submaintenance
rations his heart-rate is pronouncedly higher.
Fasting results in an almost continuous fall in the heart-rate, noticeable
at practically all three times of observation. The minimum rate noted
with steer C is 24 beats per minute, which was found on three different
occasions in the fast following submaintenance feeding in March 1924.
The minimum rate noted with steer D was, singularly enough, not during
the fast following submaintenance feeding, but during the fast in January
1922, when it was 28 and 27 beats per minute on the last day. The mini¬
mum rates were usually noted when the animal was lying. In the longest
fast, from April 14 to May 1, the heart-rates fall off so that they are almost
half of what they were on the prefasting feed-level. In the fast at the
submaintenance level the fall is pronounced with steer C, but by no means
so sharply marked as with steer D.
In the fasting experiments with steers E and F, of 5 and 6 days respec¬
tively, the heart-rates of steer E prior to fasting were 45 beats per minute
at 2 p. m., 44 beats at 4 p. m., and 36 beats at 7h 30m a. m. Almost exactly
the same values were found with steer F. These animals began fasting
after a long period on submaintenance rations. The minimum heart-rate
of steer E wTas 34 beats, a rate which was noted at least four times toward
the end of the fast. With steer F a low rate of 34 beats was also noted on
two occasions, but the minimum rate was 32 beats at 7h 30ra a. m. on the
fourth day. The picture is essentially the same with both animals and
BODY MEASUREMENTS AND PHYSIOLOGICAL FUNCTIONS 141
is in conformity with the picture shown by steers C and D, that is, a
distinct falling off in the heart-rate as the fasting progresses.
The relationship between the heart-rate and the metabolism, a relation¬
ship which has frequently been pointed out in earlier publications from
the Nutrition Laboratory, is strikingly shown in the series of 4-day experi¬
ments with steers E and F in 1924-25. The heart-rate was not determined
while the animal was inside the respiration chamber, but it was determined
twice a day for at least a week prior to each respiration experiment. Thus,
the heart-rate of steer E, when on a maintenance ration of 7 kg. of hay,
either timothy or alfalfa, was not far from 46 to 54 beats per minute, the
higher values being observed at the low environmental temperature and
with the alfalfa hay. Preceding the submaintenance experiments with
timothy hay, as low a value as 33 beats was found prior to January 13,
1925. The effect of the cold environmental temperature and submainte¬
nance feeding on timothy hay prior to February 2, 1925, is reflected in a
higher heart-rate of 41 beats, as compared to 33 beats in the earlier sub¬
maintenance experiment. When alfalfa hay was fed, the heart-rate fell,
from approximately 50 beats on the maintenance level to 32 beats on the
submaintenance level.
With steer F the picture is almost identically the same. With the mainte¬
nance ration of timothy hay the heart-rate ranged from 45 to 50 beats per
minute. On the submaintenance ration of timothy hay it was 34 to 35
beats. In both instances the environmental temperature was about 22° C.
With a lower temperature and a submaintenance ration of timothy hay
the heart-rate was a little higher, 42 beats. On the maintenance ration
of alfalfa hay the rate was 46 to 52 beats and on the submaintenance ration
of alfalfa hay it fell to 36 beats, although the environmental temperature
remained the same, i. e., about 22° C. The state of nutrition evidently has
a pronounced effect on the heart-rate, and there is a strong suggestion of
a more rapid heart-rate with a lower environmental temperature.
Respiration-Rate
The extremely high respiration-rates commonly noted in very fat animals
suggested that records of the respiration-rate should be made a part of
the daily observations, and accordingly during the winter of 1924 and
1925 an attempt was made to secure regular records of this important
physiological factor. It was found even more difficult to secure reliable
records of the rate of respiration than of the heart-beat. The extraneous
gross movements of these ruminants are so frequent that a kymograph
curve can not properly record the respirations for more than a few seconds
at a time. It is practically impossible for any one other than the regular
attendant to secure such data without extraordinary precautions, and care
should be taken that the animal is not apprehensive, has undergone no
physical exertion, and is not eating or ruminating at the time. The appli¬
cation of a pneumograph about the thorax as a part of the regular harness,
a method so successfully used by Pott,° has not thus far been attempted
in our research. We have attempted to count the respirations by watching
° Pott, Ohio Journ. SoL, 1918, 18, p. 129.
142
METABOLISM OF THE FASTING STEER
the movements of the chest, and, in some instances, by placing the hand
over the nostrils. The animals seemed to be extraordinarily susceptible to
slight changes in environment, so that the respiration-rates can not be
discussed except with greatest reserve. Exercising every care, but not
employing the pneumograph, we secured a few observations during fasting
days, and these are recorded in Table 37. The data are so few that discus¬
sion of them is hardly justified. It would appear, however, as if during
fasting the respiration-rate of these animals was not far from 9 or 10
respirations per minute. It is obvious that much remains to be done in
studying the respiration-rate of steers, and undoubtedly the pneumograph
must replace any manual or visual counting.
Table 37. — Respiration-rates of fasting steers
Steer and date
(1924)
Days
fasting
Number
of
records
Respiration-
rate
per minute
(average)
Steer C:
Mar. 4 .
2
4
10
Mar. 5 .
3
5
11
Mar. 12 .
10
5
9
Steer D:
Mar. 4 .
2
3
9
Mar. 11 .
9
2
9
Steer F:
Feb. 17 .
6
2
9
Rectal Temperature
The profound changes noted during fasting in the body-weight, the
circulatory activity (as indicated by the heart-rate), and the general
condition of the animal (as exhibited by the external appearance, and
the decrease in metabolism and in muscular activity), all suggested that
fasting might have an influence upon the rectal temperature. Hence,
throughout the entire research, rectal temperatures were recorded at specific
hours of the day (usually at 2 p. m., 4 p. m., and 6 or T^O^a. m.). A
veterinarian’s thermometer was used, and almost invariably the same
observer made the readings, due precautions being taken as to the length
of time that the thermometer was inserted and that the depth of insertion
be 10 cm. With stall-fed animals the diurnal variation in temperature
should be studied, preferably with a resistance thermometer or a thermo¬
electric element, and frequent observations should be made. Thus far,
however, no attempt has been made to use such a technique.
Space will not permit of publishing the long series of observations which
were secured on the rectal temperature of these steers. A careful exami¬
nation of the data shows that the two animals, C and D, had almost inva¬
riably the same rectal temperature, which averaged not far from 38.2° C.
In general, the highest temperatures were noted at 2 p. m. and the lowest
at 6 a. m., suggesting a diurnal rhythm. During the fasts the rectal tem¬
perature on the average was but two or three tenths of a degree higher
BODY MEASUREMENTS AND PHYSIOLOGICAL FUNCTIONS 143
on the first day than on succeeding days, but after the second day remained
reasonably uniform throughout the entire fast, irrespective of its length.
The highest rectal temperature observed during the fasting days was
39.2° C. on January 4, 1922, at 2 p. m., with both steers C and D. The
lowest temperature observed was 37.2° C. This temperature was noted in
a number of instances, namely, at 4 p. m., November 8, 1923, with steer C;
at 7 a. m., November 9, 1923, with both steers C and D; and at 4 p. m.,
March 4, 1924, with steer C. The rectal temperature was essentially the
same throughout all the fasts, irrespective of the previous state of nutrition
or the character of the ration. Thus, in the fast following submaintenance
feeding in March 1924, the rectal temperature was on the average only
one-tenth of a degree lower than in the other fasts.
Steers E and F, during their fast in February 1924, following submainte¬
nance feeding, had in general a slightly lower rectal temperature than steers
C and D, the average temperatures ranging from 38.1° C. on the second
day to 37.7° C. on the fifth day.
Examination of the data obtained on feeding days, to determine whether
the different feed-levels and digestive activity possibly have an influence
upon rectal temperature, indicates that the temperature was usually highest
at 2 p. m., but in practically all cases the range in temperature was within
1° or 1.5° C. The barn temperature had a slight effect, for on the warmer
days the rectal temperature was on the average one or two tenths of a
degree higher than on the colder days. It would thus appear as if prolonged
fasting resulted in no material disturbance of the normal rectal temperature,
which was singularly unaffected either by changes in feed-level or by
changes in environmental temperature.
Skin Temperature
The pronounced change in heat-production exhibited by these animals
when fasting, and particularly following submaintenance rations, made a
study of skin temperature of possible interest. During the March 1924
fast of steers C and D, which followed a submaintenance ration, the skin
temperature was measured at six different positions on the body on the
successive days of the fast. In these measurements the thermo-electric
method was employed, which has been so extensively used with humans
at the Nutrition Laboratory and which was used to a slight extent in the
earlier research on undernutrition in steers.0 The difficulty of securing
the skin temperature of an animal whose skin is covered with hair has been
pointed out frequently, but simply for purposes of comparison these meas¬
urements were made over the hair, that is, there was no attempt to place
the thermo- junction at the base of the hair next to the skin. In an earlier
research® the skin temperatures of 12 steers were noted on one day only.
Unfortunately, the environmental temperature was not recorded, but the
evidence was that it was high. With this high environmental temperature
the average skin temperature of two groups of steers on submaintenance
rations was not far from 32.4° C. In the fasting experiment of March
1924, the environmental temperature ranged from 14° to 18.5° C. The
0 Benedict, Miles, and Johnson, Proc. Nat. Acad. Sci., 1919, 5, p. 218; Benedict and Ritzman,
Carnegie Inst. Wash. Pub. No. 324, 1923, pp. 75, 181, and 183.
144
METABOLISM OF THE FASTING STEER
average skin temperature of steer C was 27.5° C. and of steer D, 28.0° C.
There was a slight tendency for the skin temperature to decrease as the
fast progressed.
It is clear that the environmental temperature plays a large role in such
studies, and that little can be stated until fasting experiments are made
under uniform conditions of environmental temperature. No evidence is
available as to what would have been the skin temperature of an animal
on full feed at this environmental temperature. The fact that the average
skin temperatures noted during this fast were nearly 4 or 5 degrees below
those found in the earlier study on undemutrition is probably in large part
accounted for by the difference in the environmental temperature, and it
is reasonable to assume that the fasting per se or, indeed, the fasting and
the previous submaintenance ration, were without* material effect upon the
skin temperature. This finding parallels in a general way the conclusion
drawn with regard to the rectal temperature.
GASEOUS METABOLISM AND ENERGY RELATIONSHIPS
Metabolism Measurements Actually Made or Computed
As the best index of the total metabolic activity of a living organism
physiologists have long accepted the heat-production and its accompanying
gaseous metabolism, primarily the production of carbon dioxide and the
absorption of oxygen. The apparatus at Durham, New Hampshire, was
originally designed to measure only the carbon dioxide given off by the
animal while inside the chamber. Subsequently the installation of the
delicate gas-analysis apparatus designed by Carpenter (see p. 33) made
possible the determination of the respiratory quotient, and from these two
factors the actual oxygen consumption and the heat-production could be
computed.
Methane — In the ruminant another gas enters into the gaseous metab¬
olism, for as a consequence of the prolonged retention of food residues in the
intestinal tract there are extensive fermentations which result in the produc¬
tion not only of material amounts of free carbon dioxide but of methane. In
the case of humans and most carnivorous and omnivorous animals, methane
is rarely present in measurable amounts and it is ordinarily disregarded
in metabolism measurements. Since the study of the intestinal fermenta¬
tion has given rise to the firm conviction that the methane production is an
index of the digestive activity, the determination of methane has acquired
new significance in metabolism measurements. In most of our earlier
work methane determinations were impracticable. The extensive train
of combustion furnaces and purifying devices formerly considered essential
for such determinations were too complex for use with the apparatus
installed at Durham, New Hampshire, as this apparatus was primarily
designed for the simplest total metabolism measurement with ruminants,
the idea being not to have it too complicated or elaborate for use by other
experiment stations. On a visit of one of us to Copenhagen a device
designed by Professor Mpllgaard for the analysis and determination of
methane seemed so promising that Dr. T. M. Carpenter, of the Nutrition
GASEOUS METABOLISM AND ENERGY RELATIONSHIPS 145
Laboratory staff, made a special visit to Professor Mpllgaard’s institute in
the spring of 1925, and on his return to America he so modified his delicate
gas-analysis apparatus (see p. 33) that we are now able to measure the
methane production accurately. Up to the time of completing the collection
of fasting data for this monograph, however, no determinations of methane
had been made. Thanks to the kindly cooperative spirit of Professor
Armsby in checking our first fasting experiment (which he helped to plan)
by subsequently making two fasting experiments with cows, it seemed
justifiable to proceed without these intricate determinations in our fasting
experiments, because the methane investigations in Professor Armsby’s
laboratory indicated that during the first few days of fasting the formation
of methane falls off rapidly.0 It is of importance to note that in subsequent
fasting experiments during the fall and winter of 1925-26 our methane data
confirm fully the findings of Armsby and Braman, indicating that there is
a rapid cessation of fermentative activity after the withdrawal of food.
Our own determinations of methane will not be discussed in this monograph,
however, as they do not apply to these particular fasting experiments.
The value of methane measurements in the calculation of the energy
transformations of ruminants has been pointed out by Andersen* * * 6 and such
measurements play an important role in his system of computing the heat-
production from the measured oxygen consumption and carbon-dioxide pro¬
duction. This method of computing the heat-production has not been
employed by us (see p. 148).
The close relationship between the carbon-dioxide production and the
directly determined heat-production, early reported by Armsby and his
associates, convinced us that the direct determination of the carbon-dioxide
production alone would be of value in many problems of animal research,
particularly when orientation is first desired. Stress was therefore laid
upon the measurement of the carbon-dioxide production, and provisions
were made for the accurate measurement of this factor in each experi¬
mental period of our research. This was the only factor determined quan¬
titatively. The oxygen consumption was measured relatively by noting
the carbon-dioxide increment and the oxygen decrement in the ventilating
air-current, computing therefrom the respiratory quotient, and finally cal¬
culating the oxygen consumption from the respiratory quotient and the
total carbon-dioxide production. It is thus seen that the most important
measurement enabled by the apparatus at Durham, New Hampshire, is
that of the carbon-dioxide production. During fasting experiments, par¬
ticularly after the first day or two, the carbon-dioxide production is an
accurate index of the actual heat-production. The reserve of carbohydrates
in the food and body glycogen is heavily drawn upon during the first few
days of fasting, and thereafter fat combustion predominates. The calorific
value of carbon dioxide during fat combustion is essentially constant, and
hence under fasting conditions this gaseous measurement of itself is an
excellent index of energy transformations.
“ Details of these investigations Professor Armsby kindly submitted to us in correspondence,
just prior to his untimely death. The data have subsequently been published by Braman,
Journ. Biol. Chem., 1924, 60, p. 85.
6 Andersen, K. Vet. og. Landbohojsk. (Copenhagen), Aarsskr., 1920, p. 157; ibid., Biochem.
Zeitschr., 1922, 130, p. 143.
146
METABOLISM OF THE FASTING STEER
The relationship between the volume of carbon dioxide produced and
the volume of oxygen consumed indicates the nature of the combustion in
the body. When fats exclusively are burned, the respiratory quotient is
approximately 0.70. Rarely is it found to be below this, and such quotients
have been interpreted as indicating the possible conversion of fat into
carbohydrate. When pure carbohydrates are burned, the ratio is 1.00,
and it is usually assumed that a respiratory quotient above 1.00 indicates
the transformation of carbohydrate into fat. With a combustion exclu¬
sively of carbohydrate the quotient of 1.00 is to be expected. If any carbo¬
hydrate is converted into fat, this results in an increased liberation of
carbon dioxide and raises the quotient. It is highly improbable that there
is a sharply defined line which separates a combustion exclusively of
carbohydrate and the transformation of some carbohydrate into fat, even
if the quotient does rise above 1.00. Thus, our colleague, Dr. T. M.
Carpenter, is convinced, by his own experiences in gas analysis, that there
may be a conversion of considerable carbohydrate into fat when the respi¬
ratory quotient is less than 1.00. Respiratory quotients over 1.00, however,
have been commonly accepted as indicating fat formation and respiratory
quotients of 1.00 or below as indicating carbohydrate combustion, the
intensity of which depends upon the proportion of carbohydrate in the
combustion, which becomes greater the nearer the respiratory quotient is
to 1.00.
In lieu of direct calorimetric measurements (the apparatus at Durham
not being designed to measure heat directly), it is necessary to calculate
the heat-production from the gaseous exchange. The carbon-dioxide deter¬
mination alone is of value, particularly when the heat factors of Armsby
and his associates are used. The relationships between heat-production on
the one hand, and carbon-dioxide production and oxygen consumption on
the other hand, are well known. Thus, in the oxidation of the several
organic substances which enter into the metabolism of the body, notably
carbohydrates, proteins, and fats, the amount of heat liberated per liter
of oxygen absorbed is relatively constant. The greatest variations in the
calorific value of oxygen exist between the combustion of pure fat and
the combustion of pure carbohydrates. With humans it has been found
that 12 hours after the last meal, provided this has not been excessively
rich in either carbohydrate or protein, the respiratory quotient on the
average is 0.82. Under these conditions the oxygen absorbed has an energy
equivalent of 4.825 calories per liter, and is an accurate measure of the
energy transformations. With ruminants the case is not so simple. A
respiratory quotient of 0.82 is rarely noted, except during the transition
from regular feeding to a fasting condition. Usually ruminants are con¬
tinually feeding and the quotient is generally 1.00 or slightly above. When
feed is withheld for several days, the quotient rapidly falls to not far
from 0.74 to 0.72. Under the feeding conditions the calorific value of
oxygen represents a pure carbohydrate combustion, and under the fasting
conditions almost a pure fat combustion. Between the two extremes there
is a difference of about 6 per cent in the calorific value of a liter of oxygen.
The corresponding difference in the calorific value of carbon dioxide is
GASEOUS METABOLISM AND ENERGY RELATIONSHIPS
147
approximately 30 per cent. Hence the determination of the oxygen con¬
sumption per se places energy calculations upon a much more accurate
footing.
Since our respiratory technique enabled the direct determination of the
carbon-dioxide production and the respiratory quotient, it was possible to
compute the heat-production either from the carbon-dioxide production or
the computed oxygen consumption. From the actually determined heats
of combustion of the various nutrients, such as proteins, fats, and carbo¬
hydrates, in the bomb calorimeter, and from a comparison of the measured
energy and the carbon-dioxide production, it has been found that for
each gram of carbon dioxide produced in the combustion of carbohydrate
there is a production of 2.58 calories. On the contrary, when fat is burned,
approximately 3.4 calories are produced for each gram of carbon dioxide.
The difference between the two values makes it seemingly impossible to
use carbon dioxide as an accurate measure of the heat-production of
animals, except under conditions where the character of the combustion
is fairly definitely known, as, for example, during prolonged fasting.
Due to the foresight of Professor H. P. Armsby,0 however, a large number
of measurements of the carbon-dioxide production and the heat-production
of large ruminants in his calorimeter have been recorded, and the actual
ratio between the carbon-dioxide production and the heat-production has
been determined for different animals on various kinds and amounts of
feed. Thus, it was at first thought that this relationship could be computed
with a good degree of accuracy by the equation Y3 — —0.0226a: -f- 2.802, in
which x is the air-dry weight of feed in grams per kilogram of live weight,
and F3 is the measured heat-production per kilogram of live weight divided
by the grams of carbon dioxide produced per kilogram of live weight.
These earlier experiments all dealt with animals which had been given
varying amounts of feed. A subsequent series planned by Armsby included
fasting experiments, and a revision of his earlier tabulations has been
published by one of Armsby’s associates, Braman,* 6 who has suggested the
modified equation Ya = — 0.02886x -f- 2.883. By using this equation,
Braman has computed the heat-production from the carbon-dioxide pro¬
duction with a series of cows which had been fasting from 1 to 8 days.
Obviously, in such instances the value of x is zero. The calculated heat-
production is, however, invariably lower than that actually measured, and
division of the observed heat-production by the observed carbon-dioxide
production of these fasting cows shows that the calorific value of carbon
dioxide, instead of being 2.883, is on the average nearer 3.105. In the first
days of fasting, however, this value is somewhat different than in the later
days.
For purposes of comparison of the heat-production as computed from
the carbon-dioxide production and the actually determined respiratory
quotient with the heat-production as computed from the carbon dioxide
to heat ratio, we arbitrarily used the factor 3.02 as representing the calories
per gram of carbon dioxide during the first 24 hours after food, the factor
° Armsby, FrieB, and Braman, Proc. Nat. Acad. Sci., 1920, 6, p. 263.
6 Braman, Journ. Biol. Chem., 1924, 60, p. 79.
148
METABOLISM OF THE FASTING STEER
3.13 for experiments made between the twenty-fifth and the forty-eighth
hours after food, and the factor 3.20 for experiments made more than 48
hours after food. Since the heat-production could not be directly deter¬
mined in our apparatus, we were confronted with the alternative of com¬
puting the heat-production from the carbon-dioxide production either by
means of the revised Armsby factor or by means of the calorific value of
carbon dioxide at a known respiratory quotient. The heat-production of
our fasting steers was accordingly computed for every experiment made
by multiplying the measured carbon-dioxide production (a) by the above
ratios and (6) by the calorific value of carbon dioxide at the respiratory
quotient actually determined. A comparison of the heat values as com¬
puted on these two bases shows that in general when the respiratory quo¬
tient is not far from 0.82 the agreement in the two methods of calculation
is close, but when, as is frequently the case in fasting experiments, the
respiratory quotient is much nearer 0.70, the heat-production as computed
by the factor obtained from Braman's data is almost invariably about
4 or 5 per cent lower than that computed from the calorific value of carbon
dioxide at the known respiratory quotient. When the respiratory quotient
is above 0.82, the reverse is true, the Braman factor giving higher results
than the calculations from the respiratory quotient and the measured
carbon-dioxide production. Since the Nutrition Laboratory has numerous
calorimetric data available on other animals, which support the calcula¬
tions of the heat-production from the carbon-dioxide production and the
respiratory quotient, we feel more confidence in this latter method of
computation. Hence this method has been employed in computing the
heat-production in all instances where the respiratory quotient is 1.00 or
below.
The calorific value of carbon dioxide has been well established for
respiratory quotients between 0.70 and 1.00,° and varies from 3.408 calories
per gram with a respiratory quotient of 0.70 to 2.569 calories per gram
with a respiratory quotient of 1.00. There is still much discussion as to
the calorific value of carbon dioxide and oxygen when the respiratory
quotient is above 1.00, a situation which does not occur in fasting experi¬
ments, but not infrequently occurs in feeding experiments. A considerable
amount of published experimental evidence* * 6 and, indeed, unpublished
experiments of the Nutrition Laboratory with geese and with a pig which
are also available, indicate that the calorific value of oxygen at a respira¬
tory quotient above 1.00 is not essentially different from that at 1.00.
Pending further and more elaborate direct determinations of the calorific
value of oxygen at different respiratory quotients, therefore, the computa¬
tion of the heat values reported in this monograph was carried out as
follows in all cases where the respiratory quotient was over 1.00. The
amount of oxygen actually involved in the metabolism is computed from
the measured carbon-dioxide production (converted from grams to liters)
a See Benedict and Talbot, Carnegie Inst. Wash. Pub. No. 201, 1914, p. 29, where values origi¬
nally established by Zuntz have been retabulated.
6Rapport, Weiss, and Csonka, Journ. Biol. Chem., 1924, 60, p. 683; Wierzuchowski and Ling,
Journ. Biol. Chem., 1925, 64, p. 697.
GASEOUS METABOLISM AND ENERGY RELATIONSHIPS 149
and the determined respiratory quotient, and the liters of oxygen thus
found are multiplied by the factor 5.047, the calorific value of a liter of
oxygen at a quotient of 1.00.
Under conditions where carbohydrate is converted into fat there is a
splitting off of carbon dioxide unaccompanied by the absorption of oxygen,
the so-called “atypical” carbon dioxide. In addition, there is the carbon
dioxide produced by fermentations in the intestinal tract, and this produc¬
tion is not accompanied by any appreciable absorption of oxygen. Hence
the whole situation, particularly with ruminants, is complicated by these
two factors.
Table 38 —Comparison of heat-production calculated by Andersen formula and from measured
oxygen consumption
M0llgaard
experiment
number
Heat produced per 24 hours
*
Difference
(a)
Calculated by
Andersen
formula
(b)
Calculated from
oxygen
consumption1
(c)
Total
(&> <o)
(d)
Per cent
(-« x I0°)
cal.
cal.
cal.
10
8,431
8,496
+ 65
+0.77
11
10,505
10,419
- 86
-0.82
12
12,854
12,594
-260
-2.02
14
7,809
7,853
+ 44
+0.56
15
8,261
8,288
+ 27
+0.33
16
9,874
9,761
-113
— 1.14
17
11,701
11,405
-296
-2.53
20
8,471
8,410
- 61
-0.72
21
10,098
10,201
+ 103
+ 1.02
22
10,210
10,069
-141
-1.38
23
11,690
11,704
+ 14
+0.12
24
12,413
12,179
-234
-1.89
25
12,691
12,569
-122
-0.96
26
13,143
12,777
-366
-2.78
27
13,350
13,227
-123
-0.92
30
9,197
9,260
+ 63
+0.69
31
9,946
10,044
+ 98
+0.99
32
10,802
10,753
- 49
-0.45
33
11,813
11,714
- 99
-0.84
34
12,235
12,114
-121
-0.99
35
13,922
13,702
-220
-1.58
1 Assumed that each liter of oxygen is equivalent to 5.06 calories.
In this connection, a study of M0llgaard’sa data obtained upon feeding
ruminants is of interest. In computing the heat-production of his animals,
M0llgaard makes use of the clever formula devised by his former associate,
A. C. Andersen.* * * 6 This formula, however, involves the determination of
methane and the nitrogen in urine, as well as the gaseous determination of
the carbon-dioxide production and the oxygen consumption. From unpub¬
lished experiments at the Nutrition Laboratory with surfeit feeding of
0 M0llgaard, Om Naeringsvaerdien af Roer og Byg til Fedning og om Naeringsstofforholdets
Betydning for Fodermidlernes Naeringsvaerdi. Beretning 111, Fors0gslaboratoriet, Copen¬
hagen, 1923.
6 Andersen, Biochem. Zeitschr., 1922, 130, p. 143.
150
METABOLISM OF THE FASTING STEER
geese and pigs, however, we are convinced that the calorific value of oxygen
remains remarkably constant, and when the total amount of oxygen actually
absorbed by animals is known, and particularly when the respiratory
quotient is at or near 1.00 (a condition always prevailing when ruminants
are on maintenance rations), if the total oxygen consumption in liters is
multiplied by the calorific value of oxygen for carbohydrates, namely, 5.06,
the computed heat-production will be essentially that obtained by the
Andersen formula. The advantage of this procedure is that it does not
introduce into the heat computation the inherent errors of either the nitrogen
determination or more particularly the complicated methane determination.
In order to compare the heat values as computed by these two different
methods we have summarized Mpllgaard’s experiments in Table 38. In the
second column of this table are recorded his computations of the heat-pro¬
duction by the Andersen formula, the protein katabolized and the methane
produced being taken into consideration.* In the third column are recorded
the heat values obtained by multiplying the oxygen determinations, as
found with Mpllgaard’s respiration apparatus, by the calorific value of
oxygen per liter, 5.06, when pure carbohydrates are being burned. It is
seen from the last column in the table that in general the agreement between
the two methods is within 1 per cent. Thus the simpler method of calcu¬
lation lends itself to those experiments where nitrogen determinations are
not available and methane can be determined only with difficulty, if at all.
Indeed, this comparison raises the question as to whether for many experi¬
ments the actual determination of methane is of any significance in the
computation of the energy output of the ruminant.
Conditions Prerequisite for Comparable Measurements of
Metabolism
With humans, certain conditions have been stipulated by common consent
as being prerequisite for the measurement of the basal metabolism, if the
results are to be on a comparable basis. Those factors known to influence
basal metabolism most pronouncedly are thereby either entirely eliminated
or in large part minimized by the prescribed conditions. Thus, the after¬
effect of food is minimized by insisting that the measurements be made at
least 12 hours after the last meal, which should not be too large in amount
or contain too large a proportion of protein. Some writers believe that
a constant ration should be given for two or three days before the experi¬
ment, but this procedure is generally not carried out. The well-known
influence of muscular activity is eliminated by insisting that the subject
should be in complete muscular repose, and the after-effect of previous
activity is ruled out by requiring that the subject should be lying down
for at least a half hour before the measurements are made. Psychic
disturbance must also be avoided, and the subject should be in a comfort¬
able environmental temperature and with a normal body temperature.
In studying ruminants it is highly desirable to have some such equally
satisfactory basis for securing comparable metabolism measurements. But
practically all the conditions prescribed for the basal metabolism measure-
GASEOUS METABOLISM AND ENERGY RELATIONSHIPS
151
ments of humans are impracticable with ruminants. The prolonged reten¬
tion of food materials in the paunch of the ruminant makes the question
of withholding of food a difficult one, and the point at which the true
fasting-level is reached is not sharply defined. Some of our experiments
throw light upon this subject (see p. 204). Enforced quiet is impracticable,
since animals can not cooperate as can intelligent human beings. It is
usually feasible to have the human subject rest quietly in bed, well covered,
but animals will not lie down at command, nor will they remain motionless.
In our earlier research on undemutrition in steers it became necessary to
require certain easily insured conditions for the measurement of the “stand¬
ard metabolism.” It is a matter of regret that we chose this terminology,
for Krogh,a with his critical insight, has objected to the term “basal metab¬
olism” as determined with humans and wishes to propose the expression
“standard metabolism.” Our use of the expression was simply to designate
that the metabolism was measured on a standardized basis for purposes
of comparison. Admittedly, the metabolism, as so measured, could not
have been the basal or lowest metabolism. The conditions prescribed for
the measurement of the “standard metabolism” were that the animals
should have been 24 hours without food, i. e., twice as long as in the case
of humans, and that they should be standing.
A greater energy expenditure is seemingly required to support the animal
body in the standing position than in the lying position. This difference
due to the position of the body has long been a matter of experimental
study, with widely differing results. Certain experiments which contributed
information in a minor way on this subject were reported in our earlier
monograph.6 Under the special conditions of these tests it was found that
the increment in metabolism due to standing was about 17 per cent. This
difference between the metabolism in the standing and in the lying positions
has of course no application to experiments made under standard condi¬
tions (which stipulate that the animal should be standing only), but it is
of great significance in a long experiment of 24 hours, for example, when
the animal at will alternates between standing and lying. In the latter
case the attempt is made to compute the total metabolism for 24 hours
on some basis of definite proportion between the time spent lying and
standing. For all workers who employ the 24-hour period, some method
of calculating the total 24-hour metabolism on a comparable basis is essen¬
tial, since the animal will not either lie down or stand up for 24 hours.
This matter will be discussed more at length in a later chapter (see pp
211 to 213).
The most recent contribution on this point is the article published by
Fries and Kriss,c who report some work carried out in Professor Armsby’s
laboratory. Although their final calculations are based exclusively on the
data secured upon one cow, No. 874, weighing 400 kg., the experimental
conditions were, they state, seemingly ideal. On the assumption that
animals of varying weights would have a greater energy consumption when
° Krogh, The respiratory exchange of animals and man, London and New York, 1916, pp. 56
et seq.
6 Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, pp. 215 et seq.
e Fries and Kriss, Am. Journ. Physiol., 1924, 71, p. 60.
152
METABOLISM OF THE FASTING STEER
standing than when lying in proportion to the two-thirds power of their
body-weight, these authors propose a series of factors for correcting the
total heat-production, as measured, to a standard day of 12 hours standing
and 12 hours lying, for animals ranging in weight from 275 to 575 kg.
Thus, they express the belief that with an animal of 275 kg. the “net
energy per hour” is 20.5 calories greater when the animal is standing than
when lying; with an animal of 400 kg. it is 26.3 calories greater, and with
an animal of 575 kg. it is 33.5 calories greater. These factors are now
regularly employed for application to all of the experimental work at the
Pennsylvania Institute of Animal Nutrition.®
In view of the desirability of securing comparable metabolism measure¬
ments, all of the “standard metabolism” measurements reported in this
present monograph were made 24 hours after food and with the steer in
the standing position. During those fasting experiments and those experi¬
ments made immediately after the ingestion of feed, which involved short
half-hour periods of measurement, the animals were likewise studied in
most instances in the standing position, but the time intervals following
food ingestion were of course greater or less than 24 hours. In the 3-day
and 4-day experiments involving 8-hour periods of measurement, the steer
was allowed to lie or stand at will. Since the 4-day experiments were made
expressly to study the influence of the character and amount of food, the
influence of fasting, and the influence of environmental temperature upon
metabolism, it would seem as if a better comparison of the values obtained
might be secured if the metabolism data were computed to a standard
basis on the supposition that the animal would be standing 12 hours and
lying 12 hours. The Pennsylvania investigators used this basis for their
work because they found that usually their animals stood not far from 12
hours or half of the day. During the fasting experiments, however, our
steers showed a disposition to lie down for a greater proportion of the time,
and it is probable that a better basis for the comparison of the fasting data
would be to compute the metabolism for perhaps 15 hours lying and 9
hours standing. Since the best method of handling such data is still prob¬
lematical, however, the fasting metabolism of our steers has not been
corrected to any uniform basis of lying and standing. (For further discus¬
sion of this point see p. 202.)
The Physiological Comparison of Animals
Comparison on the Basis of Live Body-weight
In comparing the metabolism of one animal with that of another, one
of the simplest attempts to equalize differences in size has been to refer
the metabolism to a uniform basis of body-weight. A large adult steer
commonly weighs around 500 kg., and it has therefore been the custom to
compute the heat-production of these large ruminants per 500 kg. of body-
weight. Some writers have referred the heat-production to the two-thirds
power of the body- weight. If physiologists are to accept the two-thirds
power of the body-weight as an expression of the law of growth and the
probable increase in active protoplasmic tissue, without reference to surface
“ Forbes, Science, 1926, 63, p. 311.
PHYSIOLOGICAL COMPARISON OF ANIMALS
153
area, we are heartily in sympathy with this method of comparing the
metabolism of animals of the same species but of different sizes. In all
of our comparisons of the metabolism of our four fasting steers on the basis
of live body-weight, however, we have computed the heat-production per
500 kg. of body-weight, which is practically the equivalent of the heat-
production per kilogram of body-weight so commonly reported for man
and small animals. We have not referred the metabolism to the two-thirds
power of the body-weight, since this computation brings in the surface-area
factor and we have felt that it is better to compute the surface area in a
different way.
Comparison on the Basis of Body-surface
The persistent popularity of the conception that the surface area is an
important factor controlling metabolism and the persistent efforts of physi¬
ologists to compare the metabolism of individuals of different ages and
sizes and under different conditions of nutrition on the basis of the heat-
production per unit of surface area make it necessary to compare the
metabolism of animals on this same basis, irrespective of any personal
credence in the significance of this comparison. For many years the
general conception has prevailed that the metabolism of warm-blooded
animals is proportional to the surface area of the animal and that the
basal heat-production per square meter of body-surface per 24 hours is
essentially the same (i. e., not far from 1,000 calories) with all warm¬
blooded animals, regardless of species, size, or age. It was recognized by
Rubner, however, that the heat-production of different individuals per
square meter of body-surface is the same only under the same general
conditions of nutrition. Yet the extensive use of the surface area as a
basis for the comparison of metabolism in pathological cases necessarily
includes a large proportion of humans in a poor state of nutrition. Since
such comparisons have been made without the slightest reservations on
the part of medical men, it therefore seems proper to compute the heat-
production per square meter of body-surface of our steers, although we
fully recognize that they were not in the same nutritive condition at all
times and hence should not, strictly speaking, be compared on this basis.
Indeed, the Nutrition Laboratory is distinctly out of sympathy with the
general belief that the metabolism of all warm-blooded animals is the
same per unit of surface area. The method of comparison is, however,
justified on the basis of usage, provided a false significance is not attached
to it and that a causal relationship between body-surface and heat-produc¬
tion is not insisted upon.
METHOD OF ESTIMATING THE SURFACE AREA OF FASTING STEERS
It is unnecessary at this point to discuss the basis and derivation of the
so-called “surface-area law,” for this subject has been considered exten¬
sively in an earlier publication of the Nutrition Laboratory.® If com¬
parisons of the metabolism are to be made, however, with reference to the
surface area, the measurement of this factor must be accurate. In the
° Harris and Benedict, Carnegie Inst. Wash. Pub. No. 279, 1919, pp. 129 et seq.
154
METABOLISM OF THE FASTING STEER
literature, new formulas for estimating body-surface, employing constants of
various sizes, are continually appearing. The experimental bases for these
constants will not, we believe, withstand the closest criticism. Thus,
Du Bois® has shown clearly the great error possible in the constant in
Meeh’s* 6 formula, so generally used for computing the body-surface of
humans. Actual measurements of the surface area of other animals are
scarce, and the computation of the surface area of animals of various
sizes still remains debatable. Du Bois® has placed the body-surface meas¬
urements of humans upon an accurate footing, and for this reason probably
more is known about the surface area of humans than of any other living
organism at the present time, but knowledge with regard to the surface
area of ruminants is by no means so definite or complete.
In the attempt to approximate as closely as possible the probable surface
area of our first groups of steers which were subjected to undemutrition,
the earlier literature regarding body-surface measurements, and particu¬
larly the more recent extensive measurements of Moulton, d were considered.
In Moulton’s formula the warm, empty weight of the animal after slaughter
enters into the calculation. It was impossible in our work with steers to
determine the warm, empty weight and it therefore had to be computed.
In the estimation of the surface areas of our animals studied in the research
on undemutrition their relative nutritive states, as appraised by an expert
judge of livestock, were used as bases for assumptions of the probable
warm, empty weights and Moulton’s formula (S = W% X 0.1186) involving
the use of the warm, empty weight was employed. This method of compu¬
tation was given extensive treatment in our earlier monographs Since this
monograph was published, an article by Hogan and Skoubyf (who suc¬
ceeded Moulton) has appeared, in which changes are suggested in Moulton’s
body-surface formula, the chief of which is the elimination of the difficult
determination of the warm, empty weight by the use of a different constant.
Thus, the five-eighths power of the live weight of the animal is multiplied
by the constant 0.1081 instead of 0.1186, and Hogan finds that the surface
areas as thus computed are confirmed by areas computed by a second
formula in which the length of the animal is taken into consideration.
Although the use of the warm, empty weight undoubtedly is of value
in many connections and is proposed urgently by Moulton for live animals,
the uncertainty regarding the amount of the fill makes it difficult to approx¬
imate such a weight. Particularly is this true during the pronounced
transitory stage of the contents of the intestinal tract incidental to pro¬
longed fasting. The actual number of cases where an animal has been
slaughtered after fasting and the fill determined are so few that almost
nothing is known with regard to the amount of fill in cattle under such
conditions. The early observations of Grouven indicate that the mass of
° Du Bois and Du Bois, Arch. Intern. Med., 1915, 15, p. 868.
6 Meeh, Zeitschr. f. Biol., 1879, 15, p. 425.
c Du Bois and Du Bois, Arch. Intern. Med., 1916, 17, p. 863.
d Moulton, Journ. Biol. Chem., 1916, 24, pp. 303 et seq.; Armsby, Fries, and Braman, Journ.
Agric. Res., 1918, 13, p. 47; Trowbridge, Moulton, and Haigh, Univ. Missouri, Agric. Expt. Sta.
Bull. 18, 1915, pp. 11 and 41.
e Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, pp. 220 et seq.
1 Hogan and Skouby, Journ. Agric. Research, 1923, 25, p. 419.
PHYSIOLOGICAL COMPARISON OF ANIMALS
155
fill was not materially decreased in his fasting oxen, although the amount
of dry matter decreased enormously.
In attempting to approximate the surface areas of our fasting steers, we
at first employed the same formula as with the steers on undemutrition,
i. e., Moulton's formula involving the use of the warm, empty weight.
Estimates of the various nutritive states and the probable fill had to be
made in order to use this formula, and aberrant results were invariably
found which could not be explained. In a few cases the lengths of our
animals were known, although these lengths were not exactly the same as
that used by Hogan in his body-surface formula. Nevertheless, it was
believed that these lengths, although subject to a slight correction, could
properly be used, and accordingly for one of our animals the body-surface
was calculated during and preceding a fasting period, upon the basis of
Hogan's formula, i. e., S— IP-4 X L0-6 X 217.02. In this formula W repre¬
sents the live weight of the animal in kilograms, L the length of the body
in centimeters from the point of withers to the end of the ischium, and
217.02 is the constant for cattle. With this formula, Hogan maintains that
the body-surface can be computed with a maximum error of less than
Sq.m.
Fig. 8. — Body-surface in square meters referred to live weight
in kilograms.
The body-surface is computed from the formula S = W'0,i X
0.1081, in which W represents the live weight.
± 5.5 per cent. A comparison of the body-surface of one of our fasting
steers as computed from Moulton’s formula involving empty weight, from
Hogan's length formula, and from Hogan’s modification of the Moulton
formula (S = W% X 0.1081) , indicates that fairly closely agreeing results
can be obtained by the two latter methods and that less aberrant values
are thus obtained for the body-surface of steers during periods of fasting
and realimentation. Hence, since the lengths of our fasting animals were
determined only once throughout the entire experimental series, we have
felt justified in using in all of the body-surface computations reported in
this monograph the formula S = W% X 0.1081, in which W is the live
156
METABOLISM OF THE FASTING STEER
weight. Indeed, so satisfactory have we found this formula and so con¬
vinced are we that this is the best available approximation of the true
surface area, that we have plotted a curve giving the surface areas of
animals with live weights ranging from 200 to 750 kg. (See Fig. 8.) This
curve, as the nature of the formula will show, is not a straight line, but
from it the surface area can be read directly, if the live weight of the
animal is known. In considering the heat-production per square meter
of body-surface in this monograph, all of the areas employed in our
calculations were taken from this curve.
In thus emphasizing the desirability of securing the greatest accuracy
in computations of the surface area of these animals, we wish to affirm
that whatever the value of the actually known surface area of these animals
may be, we can not subscribe to the prevailing notion that the surface area
is indissolubly associated with the heat-production, and in this report the
heat-production has been calculated per unit of surface area solely as a
concession to the large number of physiologists who are still wont to think
of the heat-production from this singular point of view.
Method of Presenting the Gaseous Metabolism Data
The large mass of data accumulated in this research may best be con¬
sidered, not in the chronological order of the experiments, but by grouping
the data according to the various problems studied. Separate treatment
will therefore be given to the metabolism measurements under three main
heads, i. e., the fasting experiments, the standard metabolism experiments,
and the experiments in which the effect of the ingestion of food was studied.
The fasting experiments themselves will be discussed in three general
groups. The fasts of 5 to 14 days and the short 2-day and 3-day fasts
represent one group made with the same general technique, although at
different nutritive levels. Thus, in these experiments the metabolism was
usually measured during 4 half-hour periods with the animal in the standing
position. This type of experiment comprises the bulk of the metabolism
measurements. In these experiments the metabolism was measured only
for a period of about l1/^ or 2 hours, and although the results have been
computed to the 24-hour basis, the values must of necessity be somewhat
higher than they would have been had the metabolism been measured
during the total 24 hours, for the conditions of the experiment required
that the animal should always be standing. A second group of fasting
experiments was therefore made, to secure a complete picture of the 24-hour
metabolism. In these experiments the metabolism was measured in con¬
secutive 8-hour periods during 3 continuous days, beginning 24 hours after
withdrawal of food, and the animal was allowed to lie or stand at will.
Finally, to throw light upon the transitional period between feeding and
fasting, with particular reference to the character and amount of the
previous feed-level, and also to throw light upon the influence of environ¬
mental temperature, a third group of experiments was made. In this series
the metabolism was measured in consecutive 8-hour periods and each
experiment lasted for 4 days, comprising 2 days on feed followed by 2 days
of fasting.
Table 39. — Respiratory quotients of steers during fasts of 5 to days
METABOLISM DURING FASTING
157
1 Assumed, since quotients actually determined seemed aberrant. 2 Based on quotients slightly below 0.70.
* No determinations of the respiratory quotient were made on the eleventh day.
158
METABOLISM OF THE FASTING STEER
In presenting these data it is deemed best to record in the various tables
not only the actual measurements of the carbon-dioxide production and
the respiratory quotient, but the derived computations of the heat-produc¬
tion and other related measurements obtained during the same 24 hours as
the gaseous metabolism measurement, i. e., the records of the heart-rate,
the insensible loss, and the environmental temperature.
Metabolism During Fasting
Respiratory Quotient
The determination of the respiratory quotient is of value in two respects.
In the first place, the respiratory quotient indicates the character of the
metabolic processes during the period of experiment. When the steer is
receiving full feed, the respiratory quotient will be above 1.00, indicating
carbohydrate combustion. When feed is withdrawn, the quotient will fall
as the fast progresses and ultimately will reach a value not far from 0.70,
characteristic of fat combustion. Inasmuch as practically all of our experi¬
ments dealt with the early and late stages of fasting, the determinations
of the respiratory quotient therefore serve to indicate the rapidity at which
the metabolism reaches the fasting-level. The second, and perhaps the
most important, use of the respiratory quotient is that it indicates the
calorific value of carbon dioxide to be used in the calculation of the heat-
production. Since the carbon-dioxide production of the steers was actually
determined, as well as the relationship between the carbon-dioxide produc¬
tion and the oxygen consumption, i. e., the respiratory quotient, it is possible
to compute, on the one hand, the oxygen consumption, and, on the other
hand, to secure a more accurate factor for the calorific value of carbon
dioxide in the computation of the probable heat produced.
The respiratory quotient plays its greatest role in our researches as an
index of the probable calorific value of carbon dioxide. Consequently,
before the discussion of the quantitative amount of carbon dioxide pro¬
duced, and particularly of the heat relationships, a consideration of the
actually determined respiratory quotients is desirable. The determina¬
tions made during the series of fasts of 5 to 14 days will first be examined,
and the data are accordingly given in Table 39. The results have been
computed only to two significant figures.
The first fast for which respiratory quotients could be determined was
the longest one of 14 days, because the Carpenter gas-analysis apparatus
was not installed in time to make analyses for the first two fasts. It is
perhaps not surprising, therefore, that seemingly aberrant quotients were
occasionally found. It has been assumed that quotients less than 0.70 in
all probability represent technical errors. Accordingly, in those instances
where the gas analyses gave quotients slightly below 0.70, a quotient of
0.70 has been assumed, since this value is not far from the quotient actually
found. Irrespective of this fact, the general picture of the trend of the
respiratory quotient as the fast progresses is clear. Prior to the different
fasts the quotient was about 1.00 or above, depending somewhat upon the
character of the food and probably the time since the last food was taken.
On the first day of fasting, i. e., 22 to 32 hours after food, when there was
METABOLISM DURING FASTING
159
still considerable material in the intestinal tract, the quotient is consider¬
ably below 1.00 in most instances, ranging from 0.73 to 0.97, and being on
the average 0.83. On the second day of fasting there is a further drop
with all four steers. On the third day the quotients of steer D are slightly
lower. The values for steer C tend to be a little higher than those for
steer D on the third day, although one must speak of a variability of 0.02
in the respiratory quotient with considerable reserve. After the third day
the quotients are essentially constant. The small amounts of food given
to the steers following the fasts almost invariably resulted in an increase
in the quotient, this increase depending upon the time when digestion began
and the amount of carbohydrate actually burned.
In the fasts of December 1921 and January 1922, with steers C and D,
the respiratory quotient was not determined, and it was necessary in the
computation of the heat values for these fasts to assume quotients, which,
as a matter of fact, are based upon average values derived from Table 39.
Additional information regarding the respiratory quotients during the first
few days of fasting was secured in the series of short 2-day and 3-day fasts,
and this evidence was also used in making the assumptions of the most
probable quotients to be used for the first two long fasts. These data are
given in Table 40, from which it is seen that 25 to 26 hours after food
ingestion the respiratory quotient is 0.83 on the average, and that 47 to
50 hours after food it is 0.76. In January 1923, a 3-day fast was carried
out with each animal, and a quotient of 0.72 was noted with steer C and
0.70 with steer D, 72 hours after food.
Table 40. — Respiratory quotients of steers 2J+ and 48 hours after food ( maintenance level of
nutrition)
Steer and dates
of fasts
(1923)
Hours without food
Steer and dates
of fasts
Hours without food
25 to 26
47 to 50
(1923)
25 to 26
47 to 50
Steer C:
Jan. 4 and 5. . . .
0.83
>0.73
Steer D:
Jan. 10 and 11.. . .
0.83
>0.73
Jan. 22 and 23 ... .
.83
.76
Jan. 18 and 19 . . .
.81
.74
Jan. 29 and 30. _
.82
.73
Jan. 26 and 27. . . .
.82
.78
Feb. 6 and 7 ... .
.83
.73
Feb. 2 and 3....
.86
.75
Feb. 12 and 13 ... .
.84
.74
Feb. 9 and 10. . . .
.78
.77
Feb. 19 and 20. . . .
.82
.70
Feb. 15 and 16. . . .
.82
.75
Mar. 2 and 3 . . . .
.83
.79
Feb. 23 and 24.. . .
.83
.73
Mar. 9 and 10. . . .
.84
.77
Mar. 6 and 7. . . .
.83
s (.75)
Mar. 16 and 17. . . .
.80
.77
Mar. 14 and 15. . . .
.84
.79
Mar. 23 and 24 ... .
.86
.79
Mar. 21 and 22.. . .
.86
.76
Average .
.83
.75
Average ....
.83
.76
1 Determinations made 72 hours after food in the January experiments showed a quotient of
0.72 for steer C and 0.70 for steer D.
1 Assumed ; not included in average.
In view of the picture shown by the respiratory quotients in Tables 39
and 40, and in consideration of the fact that the true fasting state is repre¬
sented by a katabolism essentially of fat, it can be seen that the steer is
burning essentially fat on the third day of fasting. The effect of the previous
160
METABOLISM OF THE FASTING STEER
state of nutrition is not so pronounced as was at first thought would be
the case. Thus, as seen from Table 39, the respiratory quotient noted with
steer C in the fast in March 1924, following submaintenance feeding, was
0.82 on the first day and 0.74 on the second day. An even lower quotient
of 0.74 on the first day was found in the fast following pasture in November
1922. On the other hand, the lowest respiratory quotient on the first day of
fasting, namely, 0.73, was noted with steer D in the fast following sub¬
maintenance feeding in March 1924. The general picture, however, is that
a fat combustion occurs not far from the third day of fasting.
Further data regarding the influence of different feed-levels upon the
respiratory quotient during the first day of fasting were secured in the
series of “standard metabolism” experiments, in which the animals were
studied 24 hours after their last feed, both at a maintenance and a sub¬
maintenance level of nutrition. In 28 experiments during maintenance
feeding the average respiratory quotient of steer C was found to be 0.84,
and in 27 experiments with steer D it was found to be 0.83. Following
submaintenance feeding, steer C had an average respiratory quotient for
12 experiments of 0.80, and steer D had an average quotient for 14 experi¬
ments of 0.77. (See Tables 55 and 56, pp. 226 and 227, for details.)
Table 41. — Respiratory quotients as affected by ingestion - of food , steers C and D
Steer and date
Last feed
before
experiment
Hours
without
food
Respir¬
atory
quotient
(average)
Daily feed-level for at
least 2 weeks prior
to experiment
Hay
Meal
Steer C:
kg.
kg.
May 31, 1922 .
3.2
2.0
0 to 4
1.12
9 kg. hay; 4 kg. meal.
June 1, 1922 .
4.5
2.0
4 6
0.96
Do.
Nov. 6, 1922 .
Grass
2 4
1.00
Pasture.
Mar. 28, 1923 .
3.6
1.0
2 4
1.06
9 kg. hay; 2 kg. meal.1
Apr. 9, 1923 .
3.8
2 4
0.96
Do.
Apr. 16, 1923 .
4.5
2 3
1.07
Do.
Nov. 5, 1923 .
Gr
ass
18 20
0.93
Pasture.
Steer D:
Apr. 5, 1922 .
4.5
1.5
8 10
1.10
9 kg. hay; 3 kg. meal.
Apr. 17, 1922 .
4.5
1.5
8 9
0.99
Do.
May 31, 1922 .
3.9
2.0
7 9
0.88
9 kg. hay; 4 kg. meal.
June 1, 1922 .
2.7
2.0
% 3
1.17
Do.
Nov. 6, 1922 .
Grass
7 8
0.86
Pasture.
Mar. 27, 1923 .
3.6
1.0
3 4
1.08
9 kg. hay; 2 kg. meal.1
Apr. 10, 1923 .
4.5
2 3
1.16
Do.
Apr. 17, 1923 .
4.5
2 4
1.03
Do.
1 Intermittent 2-day fasts between Jan. 4 and Mar. 24.
In this consideration of respiratory quotients no special attention has
been paid to the presence of methane and no attempt has been made to
differentiate between the carbon dioxide of fermentation and cleavage and
the carbon dioxide of true metabolism. The respiratory quotients reported
represent the actual determinations with the Carpenter gas-analysis appa¬
ratus. In general, the data show that the ruminant is somewhat sluggish
METABOLISM DURING FASTING
161
in adjusting himself to a fat combustion during fasting (which is to be
expected, owing to the large amount of feed residues in the intestinal tract) ,
but almost immediately responds to the ingestion of carbohydrate following
a fast of several days.
The influence of the ingestion of food upon the respiratory quotient under
normal conditions of feeding and normal body reserves is well brought
out in Table 41. Several short experiments, comprising usually 4 half-hour
periods, were made during the first few hours after food ingestion. The
feed varied from pasturage to a maximum of 4.5 kg. of timothy hay and
2 kg. of meal. In these experiments the respiratory quotient as a rule was
found to be about 1.00 or, in some cases, a little higher. The average
respiratory quotient of both animals in the 15 experiments reported in
Table 41 is 1.02.
Carbon-dioxide Production
Carbon dioxide, as the main gaseous product studied in connection with
these researches (the respiration chamber being designed in the first place
for the determination of this compound) , assumes the greatest significance
in the study of the metabolism of these steers. It was recognized at the
start that the various sources of carbon dioxide are complex with the
ruminant. There is, first, the carbon dioxide resulting from the true oxida¬
tion of body material, be it glycogen, body protein, or body fat. There
is, in addition, a transformation of soluble carbohydrate to fat, with the
cleavage of carbon dioxide, the so-called “atypical” carbon dioxide, and,
finally, there is an appreciable production of carbon dioxide as a result
of the process of fermentation. Because of the reduction in digestive
processes and in energy transformations which occur during fasting, how¬
ever, the measurement of carbon dioxide alone is of great value. In our
research on the undernutrition of steers it was found that when the animals
were on a maintenance feed-level, i. e., not burning fat, and when they
were on a submaintenance feed-level, i. e., scantily fed and drawing upon
body material, the carbon-dioxide production was extremely suggestive
of the energy transformations. With the elimination of feeding and the
rapid drafts upon body stores and available material in the intestinal
contents, the carbon-dioxide production becomes an even clearer index of
the true metabolic process than is the case during any condition of feeding.
This state is reached rapidly after the first day of fasting, when the metab¬
olism may be complicated by the combustion of material amounts of
carbohydrate substances.
Accurate measurements of the carbon-dioxide production were therefore
obtained throughout the entire series of respiration experiments. Except
during the last year, the periods of measurement, as already stated, were
usually 30 minutes in length, and the values reported for the carbon-
dioxide production are based in general upon four consecutive, well-agreeing
periods, the animal being with few exceptions always in the standing
position. During the last year of the experimental series the periods were
8 hours in length. The discussion in this chapter, however, will be confined
to the average values based on the half-hour periods with the animal,
standing.
162
METABOLISM OF THE FASTING STEER
Theoretically, the respiratory quotient should not be affected by the
size or weight of the animal, but the amount of carbon dioxide produced
is directly proportional, in general, to the size of the animal. In the presen¬
tation of the data, however, it seems best to consider, first, the actual
measurements of carbon dioxide expressed in grams per half hour, on the
assumption that, although in any particular fast the animal starts at a
definite weight and loses weight as the fast goes on, the changes in body-
weight are not great, and the measurements of the carbon-dioxide produc¬
tion are, therefore, more or less comparable. On this basis, steers C and D
may be compared with each other and steers E and F with each other,
but since the two latter steers are smaller and younger animals, they may
not be directly compared with the older animals, C and D, without further
consideration of their body-weights.
The carbon-dioxide measurements made in connection with the fasts of
5 to 14 days are recorded in Table 42. An examination of the data for
steers C and D shows that prior to the fast the carbon-dioxide production
varies from 120.5 to 172.2 grams per half hour, depending largely upon
the nature and amount of the feed received. On the first day of fasting,
the decrease in the carbon-dioxide excretion is enormous, amounting to
almost 50 per cent in two of the cases where it is possible to make the
comparison with measurements secured prior to fasting. Average values
for steers C and D for the carbon-dioxide production on the first day of
fasting can hardly be derived from the data in this table, since the March
fast followed submaintenance feeding and the two November fasts followed
pasture feeding. On the second day of fasting there is a still further
decrease in the carbon dioxide produced, amounting to not far from 20
grams in the first four fasts of steers C and D which followed maintenance
feeding, and amounting to 12 and 8 gm., respectively, with steers C and D
in the fast at a submaintenance level. On the third day there is in general
a still further decrease, save in the March fast of steer C following sub¬
maintenance rations. On the fourth day the decrease is somewhat less,
amounting usually to but 3 or 4 gm. On the fifth day nearly a constant
value is reached, and for several days thereafter no great change in the
elimination takes place. In the 14-day fasts, however, there is a still
further fall. Thus, in the case of steer C, a minimum value of 43.6 gm.
is reached on the fourteenth day, and in the case of steer D a minimum
value of 47.4 gm. is found on both the tenth and the fourteenth days.
Throughout the fast following submaintenance rations in March 1924,
the carbon-dioxide elimination is on a distinctly lower plane, a minimum
of 40.7 gm. being found with steer C on the last day and a minimum of
44.3 gm. with steer D on the eighth day. With the two younger animals,
steers E and F, which fasted following submaintenance feeding, there is
essentially a continuous decrease as long as the fasts lasted, i. e., for 4
or 5 days.
In certain experiments food was given immediately after the fast, and
in all of these instances the carbon-dioxide excretion increased appreciably,
although the time after feeding was relatively short and the amount of
food actually eaten was small, as these animals were very deliberate in
their first feeding after a prolonged fast.
Table 42.— Carbon-dioxide elimination before and during fasts of 6 to U days
(Average values in grams per half hour)
METABOLISM DURING FASTING
163
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Measurement made during period of lying and standing
164
METABOLISM OF THE FASTING STEER
In general, during these long fasts, the carbon-dioxide production falls
off rapidly during the first three or four days. The decrease usually con¬
tinues until the end of the fast and is followed by a rapid rebound after
the ingestion of even small amounts of relatively indigestible hay or meal
mixtures. In the fasts at a submaintenance level, particularly with steers
C and D, the total amounts of carbon dioxide involved, even on the first
day of fasting, are lower than in any of the other fasts. Indeed, on the
second day in the March fast of steer C a value of 42.8 gm. per half
hour was noted, which is lower than any other value found with this animal,
even at the end of the 14-day fast. On the other hand, the submaintenance
ration did not affect so profoundly the carbon-dioxide elimination of steer
D, for it is not until the eighth day of his fast following submaintenance
rations that a minimum value of 44.3 gm. is found, which is lower than
that found in any of the fasts following maintenance feeding. This differ¬
ence in the metabolism of two otherwise presumably comparable animals
will be noted frequently throughout the rest of this discussion of the gaseous
metabolism (see, especially, p. 180).
In a series of 2-day and 3-day fasts with steers C and D at a mainte¬
nance level of nutrition, carbon-dioxide measurements were also secured.
These are recorded in Table 43. In the case of steer C, it is seen that when
he had been 25 to 26 hours without food his carbon-dioxide production
per half hour was, on the average for the 10 measurements made, 71.0 gm.
This value is somewhat lower than the values shown in Table 42 for steer C
on the first day of the fasts at a maintenance level, and it is more nearly
in line with the average value to be found for this animal in Table 42 on
the second day of fasting. With steer D, the average value for the 10
experiments reported in Table 43 is 79.5 gm., materially less than the values
recorded in his case for the first day of fasting in Table 42.
Table 43. — Carbon-dioxide -production of steers per half hour, 2J+ and 4-8 hours after food
(Maintenance level of nutrition)
Steer and dates
of fasts
(1923)
Hours without food
Steer and dates
of fasts
(1923)
Hours without food
25 to 26
47 to 50
25 to 26
47 to 50
Steer C:
gm.
gm.
Steer D:
gm.
grn.
Jan. 4 and 5. . . .
66.6
1 59.2
Jan. 10 and 11.. . .
79.6
1 64.8
Jan. 22 and 23 ... .
56.8
62.8
Jan. 18 and 19.. . .
76.5
53.1
Jan. 29 and 30. . . .
77.8
43.1
Jan. 26 and 27.. . .
82.6
50.8
Feb. 6 and 7 ... .
67.2
65.9
Feb. 2 and 3. . . .
74.0
59.6
Feb. 12 and 13 ... .
69.8
61.7
Feb. 9 and 10. . . .
75.6
67.3
Feb. 19 and 20. . . .
74.6
73.0
Feb. 15 and 16. . . .
83.6
85.6
Mar. 2 and 3 . . . .
73.2
59.3
Feb. 23 and 24. . . .
79.8
73.7
Mar. 9 and 10 ... .
71.8
69.0
Mar. 6 and 7. . . .
80.2
75.1
Mar. 16 and 17 ... .
71.9
58.7
Mar. 14 and 15. . . .
79.7
72.3
Mar. 23 and 24 ... .
80.5
65.2
Mar. 21 and 22.. . .
83.7
68.0
Average .
71.0
61.8
Average ....
79.5
67.0
1 Determinations made 72 hours after food in the January experiments showed a carbon-
dioxide production of 55.3 gm. with steer C and 54.5 gm. with steer D.
METABOLISM DURING FASTING
165
On the second day of the short fasts, when the steers had been 47 to 50
hours without food, the average carbon-dioxide production was 61.8 and
67.0 gm. per half hour with steers C and D, respectively, values more
nearly like those noted on the second day of the longer fasts.
The differences noted between the series of short fasts and the series of
longer fasts in the carbon-dioxide production on the first day of fasting,
and the general differences between the two series of fasts, are excellent
demonstrations of the fact that the carbon-dioxide production on the first
day of fasting is so irregular as to make its use as an index of heat-produc¬
tion of doubtful value without careful consideration of the respiratory
quotient. The respiratory quotient also varies on the first day, as can be
seen from Table .39, page 157. The differences noted in the two series may
in part be explained by differences in prior feed conditions, the effect of
repeated short fasts, and indeed, differences in environmental temperature.
Tabular Presentation of Data for Long and Short Fasts
The data accumulated in this fasting research were so extensive that
space will not permit of publishing all the details, and it is possible to
present only condensed abstracts. During the experimental season from
December 1921 through March 1924, steers C and D fasted at intermittent
intervals for periods of. from 2 to 14 days, or a total of 80 and 76 days,
respectively. The pertinent data for these fasts have been summarized
in Tables 44 and 45. Similar data for the fasts of steers E and F in Feb¬
ruary 1924 have been summarized in Table 46. The gaseous-metabolism
measurements reported for all these fasting days were obtained 22 hours
or more after the last food was given, and in every case represent average
values for three or four, well-agreeing periods, each of 30 minutes’ duration.
In all instances the animal was in the standing position, unless otherwise
indicated in the tables. The accuracy of the respiration chamber was
frequently controlled throughout this time by introducing and recovering
known amounts of carbon dioxide. (See p. 36.)
The live weight reported for the first day of fasting, i. e., when the
animal had been for 24 hours without food, represents an average weight
based upon the weight on the given date and the weights for 6 days pre¬
ceding or for as many days preceding up to six for which live weights were
available. For each fasting day after the first the weights represent indi¬
vidual weights obtained at 2 p. m. of the given date, in all cases except the
fasts in March 1924, with steers C and D, when the weights were recorded
at 7 a. m. because the 24-hour periods began and ended at that time. The
heart-rates recorded in these tables represent those records secured nearest
to the time of the respiration experiment, either shortly before or shortly
after the experiment. The values for the insensible perspiration and for
the stall temperature are for the 24-hour periods from 2 p. m. of the
preceding date to 2 p. m. of the given date in all fasts except those of steers
C and D in March 1924, when the 24-hour periods began at 7 a. m. The
respiration experiments were usually made during the morning of the given
date, so that the values for insensible perspiration and similarly for the
stall temperature represent essentially the 24-hour period preceding the
166
METABOLISM OF THE FASTING STEER
Table 44. — Metabolism of steer C when fasting at different levels of nutrition
Insen-
Stall
temper¬
ature
Hours
Average
chamber
temper¬
ature
Carbon
Respir¬
atory
quo¬
tient
Heat produced per 24 hours
Date
Live
weight
rate
per
minute
sible
loss
per 24
hours
food to
beginning
of experi¬
ment
pro¬
duced
per half
hour
Total
Per
500 kg.
Per
sq. m.
1921
Dec. 7....
kg.
584.8
44
kg.
4.0
°C.
5
28
°C.
gm.
76.1
(0.82)
cal.
10,900
cal.
9,300
cal.
1,880
Dec.
8. . . .
561.4
34
3.4
5
52
17.0
62.1
( .76)
9,500
8,500
1,680
Dec.
9. . . .
550.0
32
1.6
15
76
20.6
55.1
( .73)
8,700
7,900
1,560
Dec.
10. . . .
543.4
36
3.2
20
97
19.3
52.8
( -72)
8,400
7,700
1,520
Dec.
11. . . .
543.4
2.8
18
121
19.3
51.4
( .71)
8,300
7,600
1,500
Dec.
12. . . .
538.2
2.2
17
146
18.8
50.3
( .70)
8,200
7,600
1,490
Dec.
13....
533.2
2.2
20
169
23.0
49.6
( .70)
8,100
7,600
1,480
1922
Jan. 5. . . .
588.2
48
11.6
20
27
24.3
79.4
( -82)
11,400
9,700
1,960
Jan.
6. . . .
570.6
38
7.0
20
51
21.9
70.8
( .76)
10,800
9,500
1,890
Jan.
7. . . .
564.4
38
4.8
20
75
20.0
60.9
( -73)
9,600
8,500
1,690
Jan.
8. . . .
555.6
36
5.4
21
97
21.5
52.6
( .72)
8,400
7,600
1,500
Jan.
9. . . .
549.0
38
3.6
24
123
24.8
55.0
( -71)
8,900
8,100
1,600
Jan.
10. . . .
548.2
38
4.2
20
147
21.3
51.6
( .70)
8,400
7,700
1,510
Jan.
11....
539.6
36
4.0
20
171
IS. 7
51.4
( .70)
8,400
7,800
1,520
Jan.
12....
536.2
30
3.6
21
196
20.8
47.3
( .70)
7,700
7,200
1,400
Jan.
13....
538.4
34
3.6
23
219
22.9
51.0
( .70)
8,300
7,700
1,510
Jan.
14....
531.8
38
4.2
23
243
23.7
52.9
( .70)
8,700
8,200
1,590
Apr.
18....
605.6
42
12.6
20
28
25.4
79.6
.89
10,700
8,800
1,800
Apr.
19. . . .
593.6
38
6.0
20
51
23.9
59.5
.82
8,600
7,200
1,470
Apr.
20....
581.0
38
7.2
20
75
21.4
56.0
( .73)
8,800
7,600
1,530
Apr.
21....
571.4
38
2.4
15
99
19.3
52.4
.73
8,300
7,300
1,450
Apr.
22....
567.0
34
3.2
20
123
19.7
51.6
.73
8,100
7,100
1,420
Apr.
23....
565.2
30
4.2
22
144
23.3
51.8
f .70]
8,500
7,500
1,500
Apr.
24 ... .
557.2
30
3.8
22
171
22.9
48.0
( .70)
7,900
7,100
1,410
Apr.
25....
552.8
32
3.6
22
195
23.4
51.1
( .70)
8,400
7,600
1,500
Apr.
26....
548.6
34
4.0
23
219
24.3
51.1
( .70)
8,400
7,700
1,510
Apr.
27....
545.6
32
4.8
20
243
19.9
47.6
( .70)
7,800
7,100
1,410
Apr.
28....
541.6
30
2.0
22
267
20.8
45.9
( .70)
7,500
6,900
1,360
Apr.
29....
535.4
32
3.0
21
291
22.1
46.9
.70
7,700
7,200
1,400
Apr.
30. . . .
531.2
32
3.6
21
312
22.3
44.9
( .70)
7,300
6,900
1,340
May
1....
529.4
30
3.4
21
336
22.4
43.6
( -70)
7,100
6,700
1,300
June
2
602.0
40
10.8
23
22
26.0
80.6
.85
11,300
9,400
1,920
June
3....
584.2
40
5.2
22
46
23.4
63.8
.75
9,800
8,400
1,690
June
4. . . .
567.6
44
5.6
23
67
25.7
52.6
.73
8,300
7,300
1,460
June
5....
558.2
32
4.6
25
94
26.6
52.4
.70
8,600
7,700
1,530
June
7....
548.2
32
7.8
26
143
29.0
53.9
[ .70]
8,800
8,000
1,580
Nov.
7....
672.4
>
48
12.6
26
25.4
*84.3
.74
i 13,200
i 9,800
» 2,090
Nov.
8. .
654.4
38
7.8
50
24.3
1 72. 6
.76
111,100
18,500
1 1,780
Nov.
9. . . .
651.6
44
8.0
73
26.7
i 66.4
.73
1 10,500
18,100
1 1,690
Nov.
10....
638.6
40
7.2
98
26.4
158.1
( .72)
i 9,300
17,300
i 1,520
Nov.
11....
631.2
40
3.0
122
16.8
1 59.8
.72
19,400
17,400
1 1,550
Nov.
14. . . .
625.0
36
2.0
192
13.4
58.5
[ .70]
9,600
7,700
1,590
Nov.
15....
617.2
38
4.0
218
27.8
61.9
l .70]
10,100
8,200
1,680
1923
Jan. 4 _
686.2
38
6.4
6
25
6.3
66.6
.83
9,500
6,900
1,480
Jan.
5....
683.0
36
3.0
9
49
7.7
59.2
.73
9,300
6,800
1,460
Jan.
6....
680.4
36
2.8
12
73
9.6
55.3
.72
8,800
6,500
1,380
Jan.
22....
686.4
40
10.8
28
25
26.7
56.9
.83
8,100
5,900
1,260
Jan.
22. . . .
686.4
36
10.8
28
30
27.9
56.8
.83
8,100
5,900
1,260
Jan.
23....
683.0
34
4.4
7
49
-1.9
62.8
.76
9,600
7,000
1,500
Jan.
29. . . .
694.2
40
4.8
8
25
2.9
77.8
.82
11,200
8,100
1,740
Jan.
30....
691.4
36
5.0
25
49
24.9
43.1
.73
6,800
4,900
1,060
%
Feb.
6....
693.2
42
5.2
6
25
2.6
67.2
.83
9,600
6,900
1,490
Feb.
7....
691.0
34
2.8
5
49
2.0
65.9
.73
10,400
7,500
1,610
1 Steer standing and lying.
METABOLISM DURING FASTING
167
Table 44.
Date
1923
'eb. 12.
'eb. 13.
eb. 19.
eb. 20.
far. 2.
far. 3.
[ar. 9 .
far. 10.
!ar. 16. .
'ar. 17..
ar. 23. .
ar. 24. .
■Metabolism of steer C when fasting at different levels of nutrition- Continued
DV.
5V.
)V.
)V.
6.
7.
8.
9
>v. 10.
1924
ir. 4.
»r.
ir.
ir.
ir.
ir.
5. ,
6. .
7..
8..
9. .
ir. 10. .
ir. 11..
>r. 12..
r. 13..
v. 13s .
Live
weight
Heart-
rate
per
minute
Insen¬
sible
Stall
Hours
without
Average
Carbon
dioxide
Respir-
Heat produced per 24 hours
loss
per 24
hours
temper¬
ature
food to
beginning
of experi¬
ment
chambe
temper¬
ature
r pro¬
duced
per half
hour
atory
quo¬
tient
Total
Per
500 kg.
Per
sq. m.
kg.
.. 689.6
. . 686.6
35
40
kg.
4.6
2.8
°C.
8
8
25
49
°C.
3.9
1.7
gm.
69.8
61.7
0.84
.74
cal.
9,800
9,600
cal.
7,100
7,000
cal.
1,520
1,500
. . 689.8
. 687.2
40
42
3.4
3.6
4
0
25
49
2.5
-1.0
74.6
73.0
.82
.70
10,700
11,900
7,800
8,700
1,660
1,860
. 694.8
. 692.4
40
48
6.2
3.8
12
14
25
49
7.3
10.9
73.2
59.3
.83
.79
10,400
8,800
7,500
6,400
1,610
1,370
. 694.0
. 691.8
34
36
4.6
3.0
4
6
25
49
4.3
2.0
71.8
69.0
.84
.77
10,100
10,400
7,300
7,500
1,570
1,610
. 698.6
. 695.6
42
34
5.2
3.2
8
8
26
50
11.9
24.4
71.9
58.7
.80
.77
10,500
8,900
7,500
6,400
1,620
1,380
. 681.4
. 676.8
40
40
14.8
8.8
26
22
25
49
29.2
13.5
80.5
65.2
.86
.79
11,200
9,700
8,200
7,200
1,760
1,530
. 694.0
46
6.2
42
65
89
113
1 37
21.5
81.7
67.7
59.3
.79
.74
.73
.72
.70
12,100
8,700
. 675.8
44
3.8
1,880
. 665.2
48
3.0
18.5
22.6
10, 600
7,800
1,670
656.4
40
2.8
9,400
7,100
1,500
(656.4)
34
63.5
10,000
7,600
1,610
10,400
7,900
1,670
636.6
36
14
16
16
16
14
16
18
14
16
16
12.0
11.1
15.2
13.1
12.3
21.3
17.7
10.7
14.0
17.5
55.1
42.8
43.8
44.4
44.5
44.2
45.8
44.9
44.7
40.7
.82
.74
.71
.70
.70
.71
.70
.70
.71
.70
7,900
6,700
7,100
7,300
7,300
7,100
7,500
7,300
7,200
6,700
627.2
619.6
613.4
609.8
604.8
600.4
597.0
593.8
589.6
30
40
28
28
24
25
28
24
34
1.4
2.6
1.8
1.4
3.8
2.0
2.2
2.2
2.0
49
73
98
122
146
170
195
219
241
6,200
5,300
5,700
6,000
6,000
5,900
6,200
6,100
6,100
5,700
1,290
1,110
1,180
1,220
1,230
1,200
1,270
1,240
1,230
1,150
764.2
54
9.2
45
24.4
>77.9
.76 >
11,900
>7,800
>1,740
* Steer not m normal condition; vomited while in respiration chamber.
measurement of the gaseous metabolism. The average chamber tempera¬
ture indicates the temperature existing during the 3 or 4 half-hour periods
when the animal was inside the respiration chamber. The actual number
of hours elapsing between the last ingestion of food and the beginning of
eXperim1e^t *s Sivenr for each date, rather than the number
oi days that the animal had been fasting.
The respiratory quotients in the fasts in April 1922 and in the subsequent
fasts were usually actually determined with the Carpenter gas-analysis
apparatus, but no determinations were made for the fasts in December 1921
““ Jan"f S' W22, and respiratory quotients had to be assumed in these
bT' / resPlratory quotients not actually determined but assumed are
inclosed in parentheses. Those inclosed in square brackets are based upon
quotients^ which were actually determined but which were somewhat below
f°r purposfs of imputing the heat-production a quotient of
u.70 has been assumed in these cases. Since the fasts of steers C and D in
December 1921 and January 1922 were made at a maintenance level of
168
METABOLISM OF THE FASTING STEER
Table 45. — Metabolism of steer D when fasting at different levels of nutrition
Date
Live
weight
Heart-
rate
per
minute
Insen¬
sible
loss
per 24
hours
1921
kg.
kg.
Dec. 7 ... ■
601.4
36
4.4
Dec. 8 -
582.6
36
3.2
Dec. 9 . . . .
576.4
36
3.2
Dec. 10 ... .
576.8
36
3.8
Dec. 11 -
Dec. 12 _
569.8
3.6
563.6
2.4
Dec. 13 -
566.6
3.4
1922
Jan. 5 . . . .
607.0
48
11.4
Jan. 6 . . . .
593.6
40
7.0
Jan. 7 ... .
591.2
40
5.0
Jan. 8 . . . .
578.8
38
6.8
Jan. 9 . . . .
586.2
36
5.2
Jan. 10 ... .
578.0
32
4.0
Jan. 11 ... .
578.4
36
3.0
Jan. 12 ... .
571.0
36
4.0
Jan. 13 ... .
568.0
28
4.4
Jan. 14 ... .
570.4
27
4.0
Apr. 18 ... .
621.0
40
12.4
Apr. 19 ... .
608.6
36
4.2
Apr. 20 ... .
599.4
34
5.2
Apr. 21 _
593.4
42
4.2
Apr. 22 ... .
586.6
42
3.0
Apr. 23 ... .
585.8
38
3.8
Apr. 24 ... .
578.8
32
3.6
Apr. 25 ... .
578.6
38
3.8
Apr. 26 ... .
575.6
30
4.6
Apr. 27 ... .
571.8
36
3.4
Apr. 28 ... .
565.0
36
3.2
Apr. 29 ... .
563.8
32
2.8
Apr. 30 ... .
557.2
34
4.2
May 1 . . . .
551.8
32
2.8
June 2 . . . .
610.8
54
9.2
June 3 . . . .
593.0
52
6.2
June 4 . . . .
585.8
48
6.2
June 5 . . . .
575.4
48
5.2
June 6 . . . .
577.8
46
8.0
Nov. 8 . . . .
661.2
48
9.4
Nov. 9 . . . .
649.8
48
8.8
Nov. 10 _
640.4
48
8.6
Nov. 12 ... .
645.0
42
3.0
Nov. 13 ... .
638.6
40
2.6
1923
Jan. 10 ... .
688.6
48
6.4
Jan. 11 ... .
685. S
42
3.4
Jan. 12 ... .
683.8
38
3.0
Jan. 18 ... .
690.0
42
6.0
Jan. 19 ... .
686.2
48
8.2
Jan. 26 ... .
688.6
44
5.8
Jan. 27 ... .
685.8
38
6.8
Feb. 2 _
681.4
44
6.0
Feb. 3 . . . .
677.4
40
3.4
Feb. 9 _
686.4
40
5.0
Feb. 10 _
683.0
42
3.2
Feb. 15...
695.4
40
4.6
Feb. 16 . . .
691.0
76
2.2
Stall
temper¬
ature
Hours
without
food to
beginning
of experi¬
ment
Average
chamber
temper¬
ature
Carbon
dioxide
pro¬
duced
per half
hour
°C.
5
30
°C.
22.0
gm.
85.6
5
54
19.9
63.8
15
78
22.3
61.3
20
99
23.7
58. 1
18
123
23.4
56.1
17
148
23.1
54.1
20
172
25.6
53.0
20
29
22.7
84.9
20
53
21.2
67.3
20
77
21.9
60.3
21
99
24.5
56.3
24
125
23.6
56.3
20
149
21.7
52.4
20
173
23.0
53.9
21
197
23.7
49.6
23
221
22.4
50.6
23
245
23.4
51.3
20
32
25.8
83.4
20
56
24.5
67.8
20
80
22.0
59.5
20
104
20.1
54.4
15
128
21.6
53.0
20
146
24.0
51.9
22
173
24.1
50.8
22
200
24.3
51.0
22
221
26.5
49.8
23
245
21.0
47.4
20
272
20.3
51.0
22
296
24.1
48.0
21
315
23.0
47.5
21
339
24.1
47.4
23
31
27.3
83.7
22
55
25.8
67.7
23
74
28.8
64.1
25
103
31.5
57.5
27
121
29.0
61.2
54
26.4
80.7
78
26.7
71.3
102
26.5
69.8
144
16.2
63.1
16S
9.3
60.0
13
26
7.0
79.6
9
49
7.0
64.8
10
74
2.7
54.5
12
25
3.4
76.5
28
49
28.2
53.1
11
26
8.8
82.6
26
49
28.3
50.8
23
25
27.9
74.0
12
47
7.3
59.6
8
25
8.6
75.6
10
49
5.7
67.3
- 3
25
-1.6
83.6
- 3
49
-7.5
85.6
Respir-
atory
quo¬
tient
Heat produced per 24 hours
Total
Per
500 kg.
Per
sq. m.
cal.
cal.
cal.
(0
.82)
12,300
10,200
2,080
(
.76)
9,700
8,300
1,680
(
.73)
9,700
8,400
1,690
(
.72)
9,300
8,100
1,620
(
.71)
9,100
8,000
1,600
(
.70)
8,800
7,900
1,550
(
.70)
8,700
7,700
1,530
(
.82)
12,200
10,000
2,060
(
.76)
10,300
8,700
1,760
(
.73)
9,500
8,000
1,630
(
.72)
9,000
7,800
1,560
(
.71)
9,100
7,800
1,570
(
.70)
8,600
7,400
1,500
(
.70)
8,800
7,600
1,530
(
.70)
8,100
7,100
1,420
(
.70)
8,300
7,300
1,460
(
.70)
8,400
7,400
1,470
.97
10,500
8,500
1,740
.83
9,700
8,000
1,630
.75
9,200
7,700
1,560
.75
8,400
7,100
1,440
.74
8,300
7,100
1,430
.73
8,200
7,000
1,410
(
.72)
8,100
7,000
1,410
(
.71)
8,200
7,100
1,420
(
.70)
8,100
7,000
1,410
(
.70)
7,800
6.S00
1,360
(
.70)
8,300
7,300
1,460
(
.70)
7,900
7,000
1,390
(
.70)
7,800
7,000
1,390
(
.70)
7,800
7,100
1,400
.77
12,700
10,400
2,130
.73
10,700
9,000
1,830
.70
10,500
9,000
1,810
.71
9,300
8,100
1,620
[
.70]
10,000
8,700
1,740
.72
12,900
9,800
2,060
.71
11,500
8,800
1,860
(
.71)
11,300
8,800
1,840
(
.70)
10,300
8,000
1,670
(
.70)
9,800
7,700
1,600
.83
11,300
8,200
1,760
.73
10,200
7,400
1,590
.70
8,900
6,500
1,390
.81
11,100
8,000
1,730
.74
8,300
6,000
1,290
.82
11,900
8,600
1,850
.78
7,600
5,500
1,190
.86
10,300
7,600
1,610
.75
9,200
6,800
1,450
.78
11,300
8,200
1,760
.77
10,200
7,500
1,600
.82
12,000
8,600
1,860
.75
13,200
9,600
2,050
METABOLISM DURING FASTING
169
Table 45. Metabolism, of steer D when fasting at different levels of nutrition — Continued
Date
Live
weight
Heart-
rate
per
minute
Insen¬
sible
loss
per 24
hours
Stall
temper¬
ature
Hours
without
food to
beginning
of experi¬
ment
Average
chamber
temper¬
ature
Carbon
dioxide
pro¬
duced
per half
hour
Respir¬
atory
quo¬
tient
Heat produced per 24 hours .
Total
Per
500 kg.
Per
aq. m.
1923
kg.
kg.
°C.
°C.
gm.
cal.
Feb. 23 ... .
691.4
54
4.4
+ 2
25
3.6
79.8
.83
11,400
8,200
1,770
Feb. 24 ... .
688.4
48
3.2
- 2
49
0.2
73.7
.73
11,600
8,400
U810
Mar. 6 . . . .
690.6
64
3.8
4
25
2.1
80.2
.83
11,400
8,300
1,770
Mar. 7 ... .
687.6
44
3.8
3
50
0.3
75.1
( .75)
11,600
8,400
1,810
Mar. 14 . . .
695.4
48
6.0
7
25
10.5
79.7
.84
11,200
8,100
1,730
Mar. 15 . . .
692.6
38
3.8
5
50
22.8
72.3
.79
10,700
7,700
U660
Mar. 21 _
693.2
52
14.2
24
26
12.6
83.7
.86
11,600
8,400
1,800
Mar. 22 _
688.4
38
10.4
27
49
29.0
68.0
.76
10,400
7,600
1 i 620
'iov. 5 _
707.0
60
22
22.1
117.4
.86
16,300
12,000
2,490
'Jov. 6 . . . .
669.6
72
11.6
46
21.2
86.2
.76
13,200
9,900
2,090
\7ov. 7 . . .
653.6
52
5.0
70
19.9
71.4
.72
11,400
8,700
1,830
'lov. 8 . . . .
658.8
52
4.8
94
15.2
70.4
.72
11,200
8,500
1,790
'lov. 9 . . . .
1924
651.4
64
4.0
116
23.2
62.9
.71
10,200
7,800
1,650
Mar. 4 . . . .
624.0
44
14
32
13.6
67.9
.73
10,700
8,600
1,770
Mar. 5 . . . .
610.0
32
3.4
16
52
14.9
59.3
.73
9,400
7,700
1,580
Mar, 6 . . . .
602.2
32
2.8
16
77
15.9
53.8
.70
8,800
7,300
1,490
Mar. 7 ... .
606.4
36
2.8
16
102
11.9
53.0
.70
8,700
7,200
1,470
Mar. 8 . . . .
598.8
48
2.2
14
126
11.7
49.5
( .70)
8,100
6,800
1,380
*lar. 9 . . . .
593.4
50
2.8
16
149
19.3
55.7
( .70)
9,100
7,700
1,560
Mar. 10 ... .
596.4
34
4.0
18
174
15.6
51.4
.70
8,400
7,000
1 ,430
Mar. 11....
590.6
36
2.2
14
198
13.8
44.3
.70
7,200
6,100
1,230
Mar. 12 ... .
587.2
34
1.4
16
228
16.2
45.0
.71
7,300
6,200
1,260
Table 46.— Metabolism of steers E and F when fasting after submaintenance feeding
Steer
and
date
(1924)
Live
weight
Heart-
Insen¬
sible
Stall
Hours
without
Average
Carbon
dioxide
Respir-
Heat produced per 24 hours
rate
per
minute
loss
per 24
hours
temper¬
ature
food to
beginning
of experi¬
ment
chamber
temper¬
ature
pro¬
duced
per half
hour
atory
quo¬
tient
Total
Per
500 kg.
Per
sq. m.
teer E:
Feb. 13...
Feb. 14...
Feb. 15...
Feb. 16...
teer F:
Feb. 13...
Feb. 14. . .
Feb. 15...
Feb. 17...
kg.
247.4
238.6
235.0
234.0
273.0
263.0
257.4
254.2
40
36
34
36
40
36
38
34
kg.
3.0
1.8
2.0
2.6
3.8
1.2
2.2
2.2
°C.
16
15
16
15
16
15
16
14
27
51
75
98
32
55
79
122
°C.
15.5
14.7
17.6
14.6
17.4
17.0
19.0
21.1
gm.
38.0
35.0
30.9
31.7
37.5
36.4
36.1
33.9
0.84
.72
I .70]
[ -70]
.78
.73
[ -70]
.72
cal.
5,400
5,600
5,100
5,200
5,600
5,700
5,900
5,400
cal.
10,900
11,700
10,900
11,100
10,300
10,800
11,500
10,600
cal.
1,600
1,690
1,550
1,590
1,560
1,620
1,700
1,570
nutrition, the assumptions for the respiratory quotients used in computing
the heat-production for these fasts were based upon respiratory quotients
obtained during the fasts in April and June 1922 and the series of short fasts
in 1923, all of which also followed maintenance feeding.
The computations of the heat-production were carried out as described
on page 148, the values for the body-surface being derived from the curve
given in Fig. 8, page 155.
170
METABOLISM OF THE FASTING STEER
The feed-level prior to each of the fasts reported in Tables 44, 45, and 46
has been indicated in Table 47. The last individual feed before each fast
is given in Table 11, page 53.
Table 47. — Feed-level prior to long and short fasts
Steer and dates
Per day
Hay
Meal
Steers C and D:
kg.
kg.
Nov. 26, 1921 to Dec. 6, 192U .
9.0
1.36
Dec. 27, 1921 Jan. 4, 1922 .
7.5
6.00
Mar. 31, 1922 Apr. 17, 1922 .
9.0
3.00
May 9, 1922 June 1, 1922 .
9.0
4.00
June 10, 1922 Nov. 6, 1922 .
Pasture
Nov. 20, 1922 Mar. 27, 1923 .
9.0
2.00
June 23, 1923 Nov. 4, 1923 .
Pasture
Dec. 21, 1923 Mar. 3, 1924 .
4.5
Steer C:
May 19, 1924 Nov. 11, 1924 .
Pasture
Steers E and F:
Dec. 18, 1923 Feb. 12, 1924 .
2.5
*0.30
1 Steers C and D were purchased Oct. 26, 1921; fed hay ad libitum
and 3 kg. meal until Nov. 26, 1921.
2 Meal ration reduced to 100 gm. on Jan. 28, 1924.
This tabular presentation of the data secured in the series of long and
short fasts is specifically for the purpose of accurate recording of results.
The large number of experiments and the length of the tables make dis¬
cussion of each individual experiment based upon these tables somewhat
difficult. For this reason only the most general features will be brought
out at this point, and the more critical discussion will be based upon the
values for heat-production, which will be summarized in tabular form to
show the course of the metabolism during each fast and which will enable
the comparison of one fast with another and of one animal with another
(see Tables 48 to 51, pp. 173 to 181).
A general inspection of Tables 44, 45, and 46 shows that as the fast
progresses there is a decrease in all the factors measured, the live weight,
the heart-rate, the insensible perspiration, the carbon-dioxide production,
the respiratory quotient, and also the computed heat-production.
The fasts varied in one striking particular, that is, in the previous state
of nutrition of the animal. Thus, the two November fasts of steers C and
D followed pasture feeding, the fasts in March 1924, with steers C and D,
and in February 1924, with steers E and F, followed submaintenance feed¬
ing, and all of the other fasts followed essentially maintenance feeding. In
most of the fasts of 5 to 14 days’ duration the chamber temperature did not
undergo extreme changes during any one fast. The range in temperatures
was from about 15° to 30° C., but a large proportion of the experiments
were made at about 20° C. Occasionally low temperatures are recorded,
however, as, for instance, on November 13, 1922, with steer D. In the
series of short fasts in 1923 pronounced differences in the temperature of
METABOLISM DURING FASTING
171
the chamber were designedly made. In any consideration of the figures,
therefore, one must continually bear in mind the environmental tempera¬
ture at which the experiments were made and particularly the previous
state of nutrition of the animals.
The two large, mature animals, C and D, were subjected to exactly the
same conditions as to previous state of nutrition and environmental tem¬
perature, in order that they might be as nearly as possible physiological
duplicates, as were steers A and B in our earlier study of undernutrition.
To introduce the factor of immaturity and growth, the two younger and
smaller steers, E and F, were studied. Obviously, a direct comparison can
not be made between the values obtained with these two steers and those
obtained with steers C and D without taking into consideration not only
the previous state of nutrition and the environmental temperature, but
likewise the age and weight of the animals.
Course of the Heat-production During Fasts of 5 to 14 Days, at Different Levels
of Nutrition
The chief index of vital activity and the one factor above all others
which one would expect to be affected by the lack of food is the general
metabolism, particularly the heat-production. The excretion of carbon
dioxide and certain physiological factors, such as heart-rate and respiration-
rate, have already been considered in a general way. The clearest cut
evidence as to the degree of vital activity, however, is to be found in the
computed heat-production. The data for the fasting experiments permit
treatment in a variety of ways. If only one fasting experiment had been
made, this would be considered from every angle. But the treatment of
so many fasting experiments seems to be best made by a critical study of
the computed heat values alone. The data for all of the longer fasts will
accordingly be considered at the same time. The heat values have been
computed upon three bases: (1) the total heat-production per 24 hours,
computed from the average of 3 or 4 half-hour carbon-dioxide measure¬
ments each morning; (2) the heat-production per 500 kg. of body-weight
per 24 hours; and (3) the heat-production per square meter of body-surface
per 24 hours.
TOTAL HEAT-PRODUCTION PER 24 HOURS
The total daily heat-production for each day of the fasts of 5 to 14 days
is presented in Table 48 for all four animals. Owing to the fact that the
two animals in each pair fasted during the same periods, it was impossible
to make the respiration experiments with both animals at the same time of
day. Thus, steer C was usually studied first in the respiration chamber
and steer D immediately afterwards, and the same treatment was accorded
to steers E and F. In Table 48, therefore, in addition to the record of the
number of days that the animal had been fasting, the number of hours after
food when the respiration experiment was made is also indicated for each
day. Thus, the respiration experiments on the first day of fasting began
with all animals between the twenty-second and thirty-second hour after
food was withdrawn. This time interval is such that these experiments on
the first day represent the so-called “standard metabolism” experiments
172
METABOLISM OF THE FASTING STEER
with steers, since in all but one instance the animals were standing during
the period of measurement. Standard metabolism measurements were also
secured with these animals from time to time throughout the entire period
of their study, and further reference will be made later to the data reported
for the first day of fasting in Table 48, when the standard metabolism
experiments as a whole are considered. (See pp. 228 to 230.)
The consideration of the total heat-production per 24 hours, irrespective
of the size of the animal, its previous state of nutrition, and the environ¬
mental temperature to which it has been exposed, precludes immediately
any exact comparison of the different fasts with each other, and greatest
stress must therefore be laid upon the metabolism during the successive
days of any given fast. It is first to be observed that there is immediately
a rapid decrease in the metabolism, which continues as the fast progresses,
being roughly proportional to the length of the fast. Thus, in the 14-day
fast in April 1922, with steer D the heat-production dropped from 10,500
calories on the first day to 7,800 calories on the fourteenth day, a fall of
2,700 calories per 24 hours. An even greater fall was noticed in 4 days in
the June 1922 fast with this same animal, however, from 12,700 to 9,300
calories on the fourth day, or a drop of 3,400 calories.
The largest decrease in the heat-production is usually found between the
first and the second day, and this is undoubtedly immediately incidental to
the withholding of food. This is strikingly shown in the November 1923 fast
with steer D, when the heat-production fell from 16,300 calories on the first
day to 13,200 calories on the second day, a fall of 3,100 calories. After the
second day, however, the decrease is for the most part regular in each
individual fast, and the total decrease is greater the longer the fast.
Although there are differences in the average level of metabolism in the
different fasts, it is only in the fast in March 1924 that such a pronounced
difference in metabolic level is found as to challenge attention. Indeed, the
metabolism, particularly toward the end of this fast with both steer C and
steer D, is altogether different from that at the end of any of the other fasts
of essentially the same length. Thus, the lowest value found with steer C
prior to March 1924 was 7,100 calories on the fourteenth day of the April
fast, and yet this value is actually higher than that measured on the second
day of the fast in March 1924. With steer D the lowest value found prior
to the March fast, namely, 7,800 calories, occurred on the tenth, thirteenth,
and fourteenth days of the April fast, and yet this is larger than the values
found on the eighth and ninth days of the fast in March 1924. Further
discussion of the fast in March 1924 will be entered into later, and it need
only be pointed out here that this fast followed pronouncedly submain¬
tenance rations. Incidentally it should also be added that the November
fasts, both in 1922 and 1923, with both animals, followed pasture feeding.
As has been frequently stated in the text, steers E and F were younger and
smaller than the mature animals, and hence their seemingly very low heat-
production of between 5,100 and 5,900 calories is explained by this fact as
well as by the fact that their fasts likewise followed submaintenance
feeding.
Table 48. — Heat-production per 24 hours during fasts of 5 to 14 days
METABOLISM DURING FASTING
173
174
METABOLISM OF THE FASTING STEER
The pronounced influence of the previous state of nutrition upon the
fasting metabolism is thus clearly indicated, not only by the falling off in
the metabolism during each day of the fast (because the previous store of
food is depleted more and more as time goes on) but by the general level
of the fasting metabolism, which is strikingly lower in the fasts following
submaintenance feeding. In the case of the two smaller animals, however,
this effect is not to be observed from Table 48 alone, but can only be noted
when a comparison is made between their fasting metabolism at the sub¬
maintenance level and their standard metabolism following maintenance
feeding. (See p. 232.)
Average figures can not be drawn from the values given in Table 48 for
the total 24-hour heat-production, since all the animals were changing in
weight, the previous states of nutrition were markedly different in the
different fasts, and the environmental temperature was in some cases
changed unintentionally and in other cases it was purposely altered to study
the influence of this factor upon metabolism. The general conclusions to
be drawn, however, are that there is a rapid and persistent decrease in the
heat-production of these large ruminants during fasting, and that the previ¬
ous state of nutrition, particularly when a submaintenance ration has been
given, has a pronounced influence upon the fasting metabolism in that the
metabolism begins at a much lower level than in the other cases and falls
to a still lower level as the fast progresses. Finally, the same mature
animal within a period of two years may have markedly different fasting
levels, even if the fast following submaintenance feeding is excepted.
HEAT-PRODUCTION PER 500 KG. OF BODY-WEIGHT PER 24 HOURS
The heat-production of these steers during the fasts of 5 to 14 days has
also been computed on the basis of 500 kg. of body-weight,® and the values
are given in Table 49, in which the days of fasting correspond exactly to
those reported in Table 48. By this method of computation the differences
in the size of the animal as any one fast progresses and the differences in
the size of the same animal from year to year are taken into account, and
it is permissible not only to consider the data from the standpoint of the
consecutive days of fasting, but likewise to compare the results obtained in
the various fasts and with the different animals. The results confirm the
findings noted in the analysis of the data for the 24-hour heat-production,
namely, that in spite of the changes in body-weight, the metabolism dis¬
tinctly decreases during the fast, and that usually the lowest values appear
at the end of the longer fasts.
The lowest value found with steer C outside of the fast in March 1924,
namely, 6,700 calories, occurred (as in the case of the total heat-produc¬
tion) on the fourteenth day of fasting. Although there is some variability
° It is particularly to be emphasized that in this report the calculations of the heat-production
per 500 kg. of body-weight are derived by referring the weight of the animal by direct proportion
to a standard weight of 500 kg. and not to the two-thirds power of the weight, which is frequently
done by other writers. Obviously, the heat-production computed per 500 kg. of body-weight
has the same significance as the heat-production per kilogram of body-weight, so commonly
computed for man and other animals. But it seems best to refer the heat-production of these
large animals to the approximate average weight of a mature steer, i. e., 500 kg.
METABOLISM DURING FASTING
175
in the values, there is with this animal a clear-cut picture of a continually
falling metabolism, especially during the 14-day fast. In the fast in March
1924, much lower values are noted than in any of the other fasts. The
body-weight was lower at this time, but the computation of the heat-pro¬
duction per 500 kg. of body-weight eliminates to a certain extent any differ¬
ences due to differences in body-weight, and it is thus evident that the low
metabolic level noted in this March fast reflects the influence of the preced¬
ing submaintenance regime.
In the fasts following maintenance feeding, that is, in the first six fasts
with each of the larger animals, the fasting metabolism reaches a reasonably
constant level on or about the fourth or the fifth day, but it can not be
definitely asserted that on any certain day the metabolism had reached a
minimum point with either animal in all experiments. This may be in part
due to the fact that although the animals were measured in the standing
position, the activity while the animal was inside the respiration chamber
differed somewhat from day to day. It is believed, however, that the
irregularities in metabolism can by no means be wholly explained by differ¬
ences in activity during the respiration experiment. The graphic records
show, it is true, variations in the activity when the animal was inside the
chamber and indicate that there was a general tendency, although by no
means uniform, for the animals to be less active as the fast progressed. A
part of the fall in metabolism shown in Table 49 may therefore be due to
a greater degree of repose. Variability in activity is one of the great
stumbling blocks in the study of the metabolism of these animals, whose
activity can not be controlled. It is a distinct argument in favor of the
24-hour experiment, in which the uniformity in stall activity would be
greater in general than in any chance three or four consecutive half-hour
periods. Indeed, at this stage of our experimentation we were inclined to
believe that the 24-hour period would enormously help in the explanation
of these figures. But even in 24-hour experiments irregularity in activity
occurs persistently, although in general the animals lie down a little longer
as the fast progresses. Since the experiments reported in Table 49 com¬
prised three or four consecutive half-hour periods inside the respiration
chamber, and the steer was always forced to stand during these short experi¬
ments, the chamber activity was for the most part of sufficient relative
uniformity so that the differences could not wholly explain the differences
in the metabolism noted in this table.
A second factor which is known to influence the metabolism of animals
is that of environmental temperature. The uniformity in the environmental
temperature in these experiments was by no means so great as it should
have been. This is particularly true in the two experiments in December
1921, as can be' seen by reference to Tables 44 and 45 (pp. 166 and 168).
Thus, on the two days preceding the metabolism measurements, the stall
temperature for 24 hours was low, 5° C., but the chamber temperatures
during the experiment were higher, i. e., from 17° to 22° C. In the other long
fasts, however, there was not such a marked difference between the stall
temperature preceding and the chamber temperature during the experiment.
Table 49— Heat-production per 500 kg. of body-weight per hours during fasts of 5 to H days
176
METABOLISM OF THE FASTING STEER
■>}«
rH
336 to
339
cal.
6,700
7,100
CO
T*H
312 to
315
cal.
6,900
7,000
03
rH
291 to
300
cal.
7,200
7,000
rH
rH
267 to
272
cal.
6,900
7,300
o
rH
241 to
245
cal.
8,200
7,100
5,700
7,400
6,800
05
216 to
228
cal.
7,700
7,700
8,200
6,100
7,300
7,000
6,200
tc
00
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192 to
200
cal.
7,200
7,600
7,700
6,100
7,100
7,100
6,100
*>3
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168 to
174
cal.
7,600
7,800
7,100
6,200
7,700
7,600
7,000
7,700
7,000
o
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rH
cal.
7,600
7,700
7,500
8,000
7.900
5.900
7,900
7,400
7,000
O * O
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113 to
128
cal.
7,600
8,100
7,100
1 7,400
7,600
6,000
8,000
7,800
7,100
8,700
7.800
6.800
10,600
89 to
104
o o o o o o o
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65 to
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11,500
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22 to
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10,200
10,000
8,500
10,400
12,000
8,600
10,900
o
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rH
- — -
Steer and
dates of fasts
Steer C:
Dec. 6 to 13, 1921 _
Jan. 4 14,1922...
Apr. 17 May 1,1922
June 1 7,1922...
Nov. 6 16,1922...
Nov. 4 10,1923...
Mar. 3 13, 1924 . . .
Steer D:
Dec. 6 to 13, 1921 . . .
Jan. 4 14, 1922 . . .
Apr. 17 May 1, 1922
June 1 6,1922...
Nov. 6 14,1922...
Nov. 4 9,1923...
Mar. 3 12, 1924 . . .
Steer E:
Feb. 12 to 17, 1924. . .
Steer F:
Feb. 12 to 18, 1924. . . .
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METABOLISM DURING FASTING
177
Indeed, the changes in temperature from day to day during these fasting
experiments were, for the most part, very small, so that any great change
in the metabolism can not, save possibly in the first experiment, be attributed
to the environmental temperature. The average environmental temperature
during most of the fasts was about 20° C. In the March fasts perceptibly
lower temperatures prevailed and in the June fasts perceptibly higher
temperatures. It is obvious that the temperature of the chamber during an
experiment made in June would be higher than that during an experiment
made in January of the same year. Thus, the chamber temperatures during
the fasts in June 1922 were from 26° to 28° C. The values for the heat-
production per 500 kg. of body-weight, however, are not appreciably lower
in the June fast of steer C than in the other fasts with this animal. They
are somewhat lower, for the most part, than the values in the January fast,
but they are higher than those in the April fast. In the case of steer D the
reverse is true, that is, the June values are actually higher than those in
January. In fact, the highest values in the series up to that date were
found in June 1922.
In the earlier research on undernutrition in steers it was noted that the
effect of environmental temperature seemed to be small and was contrary
to the commonly accepted belief that the lower temperature is accompanied
by a higher metabolism in warm-blooded animals. Indeed, certain of the
results obtained suggested strongly that the metabolism may be lower the
lower the temperature. The necessity for constancy in environmental tem¬
perature was therefore not stressed perhaps as much as it should have been
in these fasting experiments of 5 to 14 days. Subsequently, however, a
special study of the influence of environmental temperature was made in a
series of short fasts in 1923 (see pp. 180 to 185) and in a series of 4-day
experiments with steers E and F (see pp. 200 to 202). As no irritating
agencies pestering the animals could be accounted for, the difference in the
heat-production in this series of fasts must be ascribable to true cell differ¬
ences in the metabolism of these animals at different stages and is not due
to differences either in abnormal stall activity or in environmental tem¬
perature. The preceding nutritive state, however, particularly the submain¬
tenance level of nutrition, did have an influence.
Although it was noted in Table 48 that steers E and F had a much lower
total heat-production on the different days of their fasts than did steers C
and D, the calculations on the basis of equal body-weight, reported in
Table 49, show that these animals actually had a higher metabolism per
500 kg. of body-weight than did the adult animals, especially after the first
day. The metabolism of steers E and F was higher even when their fasting
values after submaintenance feeding are compared with those for steers C
and D in the fasts after maintenance feeding. Indeed, on no day was the
heat-production of steer F per 500 kg. of body-weight lower than 10,300
calories. This evidence is, in all probability, to be taken as an index of the
greater activity of the younger protoplasm, and it is fully in line with the
finding on humans that the heat-production per kilogram of body-weight
of the child is always notably higher than that of the adult.
Table 50. — Heat-production per square meter of body-surface per 24 hours during fasts of 5 to 1 4 days
178
METABOLISM OF THE FASTING STEER
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METABOLISM = DURING FASTING
179
HEAT-PRODUCTION PER SQUARE METER OF BODY-SURFACE PER 24 HOURS
On pages 153 to 156 the calculation of the surface area of steers, based
upon various formulas suggested by recent writers, has been discussed. It
was there pointed out that Hogan’s formula, in which the five-eighths power
of the live weight in kilograms is multiplied by the constant 0.1081, probably
gives a reasonably close measure of the true surface area in square meters.
It is perhaps unfortunate that for the comparison of the same animal under
different conditions of flesh during fasting, when striking differences take
place within a relatively few days, a better means of determining the exact
surface area is not available. In lieu of better surface-area measurements
all of the calculations of the 24-hour heat-production per square meter of
body-surface have been made employing this formula.0 These calculations
are summarized in Table 50 for the same fasts and animals as reported in
Tables 48 and 49.
Exactly as with the total metabolism and the metabolism per 500 kg. of
body-weight, there is a pronounced drop in the heat-production between the
first and the second days of fasting per unit of body-surface and there is,
in general, a still further drop as the fasts progress. The minimum value
in the first six fasts again appears, in the case of steer C, on the fourteenth
day of fasting, i. e., 1,300 calories. This value, however, is greater than
that found on the first day of the fast in March 1924, following prolonged
submaintenance feeding. The absolute minimum found with this animal is
1,110 calories on the second day of the March fast. With steer D the
lowest value found prior to the fast in March 1924 was 1,360 calories on
the tenth day of the April fast. On the eighth and ninth days of the fast
following submaintenance feeding in March 1924, values of 1,230 and 1,260
calories, respectively, were noted, the first value being actually the lowest
in the entire series with this animal.
In the case of steer C, in the fasts other than the last one, uniformity in
the heat-production per square meter of body-surface appears at about the
fourth day of the fasts, but the values for steer D do not approach uni¬
formity until much later, i. e., on the seventh or eighth day. On the fifth
day in the first six fasts of steer D there is an actual range in the values of
from 1,430 to 1,740 calories, that is, 22 per cent. In view of the influence of
undemutrition upon the fasting metabolism of both animals in March 1924,
it is not surprising perhaps that these differences in metabolism are noted in
the earlier fasts of these animals, which at times fasted after pasture feed¬
ing and at times after stall feeding with supposedly maintenance rations.
° We wish to call attention here to the articles published recently by Brody and Elting regard¬
ing a new method proposed by them for measuring the surface area of cattle (Elting, Journ.
Agric. Research, 1926, 33, p. 269; Brody and Elting, Univ. Missouri, Agric. Expt. Sta., Bull. 89,
1926). These articles appeared after the manuscript of this monograph had been sent to the
printer, and hence too late for us to make use of their body-surface formula in our calculations.
Brody and Elting propose the equation S — 0.15 TV0-54 as expressing the relation between body-
weight and surface area, in which S equals the surface area in square meters and W the live weight
in kilograms. At the moment of writing we are unconvinced that this is a real betterment of the
Hogan formula, but if the new formula had been used for our steers, the body-surface values for
steers C and D would be approximately 10 per cent lower than they are by Hogan’s formula and
those for steers E and F would be about 4 per cent lower. Hence, on this basis the values for the
heat-production per square meter of body-surface would be 10 per cent and 4 per cent higher,
respectively, than we have reported in this monograph.
180
METABOLISM OF THE FASTING STEER
A comparison of the values for the first day of the different fasts, except¬
ing the fasts at the submaintenance level, shows no sign of uniformity
between the two animals C and D. Steer D has a distinctly higher meta¬
bolic level than has steer C, the single exception being on the first day of
the April fast, when his heat-production was a little lower than that of
steer C. On the second day of fasting the values for the most part are
higher with steer D than with steer C. This is also true in the case of the
third day of fasting and, indeed, throughout essentially all of the succeeding
fasting days, except that in the 10-day and 14-day fasts the metabolism of
both animals is reasonably similar after the second day. In the fast fol¬
lowing submaintenance feeding steer D is upon a definitely higher metabolic
level than steer C until the eighth day is reached.
The values for the two smaller animals, E and F, on the basis of equal
body-surface, are for the most part of the same order as those noted on the
average with steers C and D, but they are notably higher than the values
for steer C found in his fast after submaintenance feeding. The effect of
submaintenance rations on steer D was much less pronounced for the first
7 days of fasting than it was with steer C. In this respect again, therefore,
the evidence is that with steers E and F, which fasted at a submaintenance
level, higher values for the metabolism per square meter of body-surface
per 24 hours prevail than with one of the two adult animals, steer C, at a
submaintenance level. Indeed, the values for steers E and F are a little
higher than those for steer D at the submaintenance level, a fact which
points again to the higher metabolism of the younger protoplasm.
Examination of all three bases for comparing the heat-production of these
animals shows clearly that steer D is a distinctly different type from steer
C, having a higher metabolism in all the fasts. This may be partly explained
by the definitely greater stall activity of steer D, although our experience
would lead us to believe that this difference in activity can not possibly
account entirely for the difference in the metabolism of the two animals.
Steers E and F, younger and lighter in weight, have a metabolism of an
altogether different order from that of steers C and D. Their heat-produc¬
tion per square meter of body-surface more nearly corresponds to that of
steer D than that of steer C, although it is somewhat higher than even that
of the former. These comparisons bring out the influence of individuality
in these animals. Indeed, the word “temperament” might be ascribed to
the known restlessness of steer D. Experiments in which the nutritive plane
is the same or essentially the same and in which the animals are lying
quietly will be necessary to establish these differences quantitatively and
sharply. That they exist is highly probable.
Heat-production in 2-day Fasts at a Maintenance Level of Nutrition
As is clearly brought out in Tables 48, 49, and 50 (pp. 173, 176 and 178),
in which the data for the longer fasts are summarized, the most pronounced
changes in metabolism due to fasting are to be observed in the first, second,
and third days. Hence it seemed desirable to supplement the longer fasts
by a series of short fasting experiments with steers C and D, in which
emphasis would be laid upon the earlier stages of the fast. Furthermore,
since it was evident that differences in nutritive level have a pronounced
METABOLISM DURING FASTING
181
effect upon the fasting metabolism, these experiments were planned to rule
out changes in nutritive level by having the animals fast in every case after
an essentially maintenance ration. Opportunity was also taken to accentu¬
ate the influence of environmental temperature, in that many of the experi¬
ments were made under widely different temperature conditions. It is
therefore impossible to compare directly the values obtained in these short
fasting experiments with those obtained in the longer experiments, without
taking into consideration the differences in environmental temperature and
the fact that in the series of short fasts the animals were always studied at
a maintenance level of nutrition, but that in the longer fasts they were
studied after maintenance and submaintenance feeding and after coming
from pasture. Furthermore, in comparing the first and second days of
fasting in this series of 2-day fasts, it must be borne in mind that not infre¬
quently the animals were arbitrarily subjected to marked changes in
environmental temperature from one day to the next.
Table 51. Heat-production of steers C and D in 2-day fasts at a maintenance level of
nutrition
Steer and dates of
fasts (1923)
Heat-production per 24 hours
Total
Per 500 kg.
Per sq. m.
Hours without food
25 to 26
47 to 50
25 to 26
47 to 50
25 to 26
47 to 50
Steer C:
cal.
°c.
cal.
°C.
cal.
cal.
cal.
cal.
Jan. 4 and 5 1 . . .
9,500
6.3
9,300
7.7
6,900
6,800
1,480
1,460
Jan. 22 and 23 ... .
8,100
27.9
9,600
-1.9
5,900
7,000
1,260
1,500
Jan. 29 and 30 ... .
11,200
2.9
6,800
24.9
8,100
4,900
1,740
1,060
Feb. 6 and 7. . . .
9,600
2.6
10,400
2.0
6,900
7,500
1,490
1,610
Feb. 12 and 13 ... .
9,800
3.9
9,600
1.7
7,100
7,000
1,520
1,500
Feb. 19 and 20. . . .
10,700
2.5
11,900
-1.0
7,800
8,700
1,660
1,860
Mar. 2 and 3 . . . .
10,400
7.3
8,800
10.9
7,500
6,400
1,610
1,370
Mar. 9 and 10. . . .
10,100
4.3
10,400
2.0
7,300
7,500
1,570
1,610
Mar. 16 and 17. . . .
10,500
11.9
8,900
24.4
7,500
6,400
1,620
1,380
Mar. 23 and 24. . . .
11,200
29.2
9,700
13.5
8,200
7,200
1,760
1,530
Average .
10,100
9,500
7,300
fi 900
1 £70
1 4QH
Nov. 13, 1924 .
11,900
24 4
7,800
1 7df)
Steer D:
Jan. 10 and 11 1. . .
11,300
7.0
10,200
7.0
8,200
7,400
1,760
1,590
Jan. 18 and 19 ... .
11,100
3.4
8,300
28.2
8,000
6,000
1,730
1,290
Jan. 26 and 27 ... .
11,900
8.8
7,600
28.3
8,600
5,500
1,850
1,190
Feb. 2 and 3. . . .
10,300
27.9
9,200
7.3
7,600
6,800
1,610
1,450
Feb. 9 and 10. . . .
11,300
8.6
10,200
5.7
8,200
7,500
1,760
1,600
Feb. 15 and 16. . . .
12,000
-1.6
13,200
-7.5
8,600
9,600
1,860
2,050
Feb. 23 and 24. . . .
11,400
3.6
11,600
0.2
8,200
8,400
1,770
1,810
Mar. 6 and 7. . . .
11,400
2.1
11,600
0.3
8,300
8,400
1,770
1,810
Mar. 14 and 15. . . .
11,200
10.5
10,700
22.8
8,100
7,700
.1,730
1,660
Mar. 21 and 22. . . .
11,600
12.6
10,400
29.0
8,400
7,600
1,800
1,620
Average .
11,400
10,300
8,200
7,500
1,760
1,610
1 On Jan. 6 and 12, with steers C and D, respectively, the 24-hour heat-production 72 hours
after food was as follows: Steer C, 8,800 cal. per 24 hrs.; 6,500 cal. per 500 kg.; 1,380 cal. per
sq. m.; steer D, 8,900 cal. per 24 hrs.; 6,500 cal. per 500 kg.; 1,390 cal. per sq. m.
182
METABOLISM OF THE FASTING STEER
The values for the computed heat-production during this series of 2-day
fasts are summarized in Table 51, being reported on the three different bases
of the total 24-hour heat-production, the heat-production per 500 kg. of
body-weight per 24 hours, and the heat-production per square meter of
body-surface per 24 hours. In addition, the average chamber temperature
prevailing on each day when the metabolism was measured is given at the
right of the values for the total 24-hour heat-production.
A comparison of the values for the total 24-hour heat-production is
justifiable, since in the short period of 3 months during which the animals
were studied, their body-weights did not alter materially, because they
were always upon a maintenance level of nutrition. On the first day of
fasting, i. e., 25 to 26 hours after food, the total heat-production of steer C
ranged from 8,100 calories on January 22 to 11,200 calories on January 29
and March 23. With steer D the metabolic level was higher, the lowest
value being 10,300 calories on February 2 and the highest being 12,000
calories on February 15. Contrary to our usual custom with these animals
in the longer fasts, the 2-day fasts were not made under the same tempera¬
ture conditions and on the same dates with each animal. Disregarding for
the moment the differences in environmental temperature, we find that the
average 24-hour heat-production of steer C on the first day is 10,100
calories and of steer D 11,400 calories. Since these animals were of almost
the same weight, the metabolism of steer D on this basis is about 13 per
cent higher than that of steer C. The average chamber temperature during
the experiments with steer C was 9.9° C. and with steer D 8.3° C., i. e.,
somewhat lower. Hence it might be argued that the higher metabolism
noted with steer D might be accounted for by the fact that the average
environmental temperature was lower in his case. A close examination of
the figures on individual days shows that the minimum metabolism of steer
C, 8,100 calories, occurred on January 22, when the environmental tem¬
perature was 27.9° C. On the other hand, the maximum metabolism, 11,200
calories, occurred on January 29 with an environmental temperature of 2.9°
C., and also on March 23 with an environmental temperature of 29.2° C.
Hence with steer C the effect of the temperature is not clear-cut. With
steer D the lowest value, 10,300 calories, is found on the day with the
highest temperature, 27.9° C., and the highest value, 12,000 calories, is found
on the day with the lowest temperature, -1.6° C. The difference between
these two heat values represents an increase in metabolism of 16.5 per cent
with a fall in temperature of approximately 30°. Although extremely high
temperatures did not prevail on any of the other experimental days, an
examination of the data for the individual days other than these two days
shows that it is difficult to find a distinct trend of low metabolism on days
with the higher temperatures and high metabolism on days with the lower
temperatures. Indeed, the general picture for the two animals together does
not indicate a definite effect of temperature.
On the second day of fasting, 47 to 50 hours after the last food, lower
values as a rule obtain with both animals, as is to be expected from the
analysis of the data for the long fasts. With steer C the lowest value on
the second day is 6,800 calories with a temperature of 24.9° C., and the
highest value is 11,900 calories with a temperature of -1.0° C. Here there
METABOLISM DURING EASTING
183
is seemingly clear evidence of an effect of environmental temperature, and
yet an examination of the values on other dates shows that although in
general the metabolism is higher the lower the temperature, this is by no
means invariably the case. With steer D the lowest metabolism on the
second day is 7,600 calories on January 27 with a temperature of 28.3° C.,
and the highest is 13,200 calories on February 16 with a temperature of
—7.5° C. Here again a higher metabolism is noted with a low temperature,
and yet with the high temperature on March 22 the metabolism is 10,400
calories as compared with 7,600 calories on January 27, when the tempera¬
ture was also high.
The influence of temperature may furthermore be specially studied by
comparing the instances where great differences in temperature were arti¬
ficially produced on two consecutive days. Thus, with steer C on January
22 the temperature was held at 27.9° C., and the next day at -1.9° C. In
spite of the fact that in the experiment made at —1.9° C. steer C had been
fasting for 2 days, the 24-hour heat-production was 9,600 calories as com¬
pared with 8,100 calories on the first day at 27.9° C. In the next fast, on
January 29 and 30, the increase in temperature on the second day has
accentuated the normal fall in metabolism on the second day of fasting,
since on the first day the metabolism was 11,200 calories at 2.9° C. and on
the second day at 24.9° C. it was but a little over one-half as great, i. e.,
6,800 calories. On February 19 and 20 the metabolism was a little higher
on the second day than on the first, but apparently with the low tempera¬
tures, such as prevailed on March 9 and 10, the influence of fasting is less
pronounced, for with essentially the same temperature on both days the
metabolism is the same. On January 18 and 19, with steer D the increase
in temperature on the second day accentuated the normal loss in heat-
production as a result of fasting. This is also true on January 26 and 27.
On February 15 and 16 a drop in temperature of 6° has seemingly raised
the metabolism on the second day actually above that on the first, and yet
on March 15 a rise of 12° in the temperature hardly influenced the heat-
production. On November 13, 1924, at a temperature of 24.4° C., steer C
produced 11,900 calories on the second day, a value which is identical with
the highest value on the second day noted on February 20, 1923, and yet
on November 13, 1924, the environmental temperature was 24.4° C. while
on February 20, 1923, it was —1.0° C.
An examination of the records of stall temperature during the 24 hours
immediately preceding the metabolism measurements during these short
fasts indicates that in nearly every instance the stall temperature was
essentially the same as the chamber temperature during the respiration
experiment. There were a few cases, however, when the stall temperature
was markedly different from the chamber temperature. Thus, on March 17,
1923, steer C was placed in the respiration chamber at a temperature of
24.4° C., after having been for 24 hours previous in his stall at a tempera¬
ture of 8° C. On March 24, 1923, the chamber temperature was 13.5° C.
as compared with a stall temperature of 22° C. during the preceding 24
hours. Similarly, in the case of steer D on March 15, 1923, the stall tem¬
perature had been 5° C. and the chamber temperature was 22.8° C., and on
March 21, 1923, the stall temperature had been 24° C. and the chamber
184
METABOLISM OF THE FASTING STEER
temperature was 12.6° C. It is possible that a sudden marked change in
temperature may cause a temporary disturbance in the animal’s heat-loss
and heat-production. Experiments made under such conditions do not,
therefore, lend themselves to the study of the effect of a high or low environ¬
mental temperature upon metabolism so well as do experiments made under
conditions when the animal has been living for one or two weeks at least at
the same environmental temperature in the stall as is to prevail during the
respiration experiment. It was therefore planned to include in our research
a series of experiments made under such conditions, to study the effect of
wide differences in temperature. These experiments will be considered later
(see pp. 200 to 202).
On January 6 and 12, respectively, the metabolism of steers C and D was
studied 72 hours after food and was found to have fallen perceptibly in both
cases, with no very pronounced changes in the environmental temperature.
This finding is in line with the picture shown in the longer fasts.
It is hardly feasible to compare the metabolism on the first and second
days of the short fasts (see Table 51, p. 181), with the metabolism on the
same days in the longer fasts (see Table 48, p. 173), for there were differ¬
ences in body-weights in the longer experiments, and no averaging of the
data in Table 48 is justifiable on account of the different metabolic levels
at which the longer fasts began.
A further factor which prevents a comparison of the short fasts with the
longer fasts is the influence upon metabolism of the marked temperature
differences designedly employed in the series of short fasts. It is only when
the metabolism is computed upon the basis of equal size, that is, per 500
kg. of body-weight or per square meter of body-surface, that any compari¬
sons are justifiable. But even on this basis one must carefully avoid com¬
parison with the experiment in March 1924, which was made at a submain¬
tenance level, and one must also bear in mind the influence of sudden
changes in environmental temperature.
The picture of the 24-hour heat-production per 500 kg. of body-weight
during the 2-day fasts in 1923 is essentially the same as that of the total
heat-production, for the body-weights of the two animals were essentially
alike and changed but little throughout the series of fasts. Much the same
picture is also shown by the heat-production per square meter of body-
surface. An extraordinarily low value of 1,060 calories per square meter
of body-surface was noted with steer C on January 30 with an environ¬
mental temperature of 24.9° C. and a low value of 1,190 calories was noted
with steer D on January 27 with an environmental temperature of 28.3° C.
These two figures more nearly approximate the conventional 1,000 calories
per square meter of body-surface, which many physiologists believe repre¬
sents the general heat-production of warm-blooded animals. Too little is
as yet known, however, with regard to the influence of environmental tem¬
perature upon animals to make any generalizations. It is hardly conceiv¬
able that the normal environmental temperature of a ruminant should be
25° to 28° C. or higher, and yet this temperature more nearly approximates
the “private climate”0 of the clothed human than does the ordinary stall
° Dorno, C., Medical climatology and high-altitude climate, Vieweg and Son, Brunswick, 1924,
p. 58.
METABOLISM DURING FASTING
185
temperature or, indeed, the conventional 20° C. maintained in the ordinary
experiments in the respiration chamber or respiration calorimeter. If these
low values had been repeatedly found, much more credence could be given
to their significance. They do not appear in the long fasts, where one
would expect, if anywhere, to find a very low heat-production per square
meter of body-surface. Indeed, the lowest values noted in the long fasts,
other than m the fasts following submaintenance feeding, were 1,300 calories
per square meter of body-surface with steer C and 1,360 calories with
steer D. All of these measurements, however, were made with the animal
standing, and it may be argued that the difference above the conventional
1,000 calories per square meter of body-surface may be in large part
explained by the extra effort of standing. Further discussion of this point
will be deferred until later (see p. 218). It is sufficient to state at this
point that it is not believed that the difference in metabolism in the two
positions can possibly explain the values noted for the heat-production per
square meter of body-surface.
Measurement op Fasting Metabolism in Three Consecutive 24-hour Periods
The basic principle of studying the metabolism of ruminants in short
periods has frequently been challenged. The history of the change from
long to short periods in the study of the metabolism of ruminants is not
unlike that with other animals and humans. Practically all of the work on
humans by Atwater and his associates with the respiration calorimeter at
Wesleyan University, Middletown, Connecticut, was based upon 24-hour
periods. Armsby, building a calorimeter on the model of the Wesleyan Uni¬
versity apparatus, likewise used the 24-hour period. With humans it was
soon seen that much valuable information could be obtained at far less
expense by making metabolism measurements in shorter periods, from
which the probable 24-hour metabolism could be computed. The 24-hour
period, which includes the profound influence upon metabolism of variations
m muscular activity, body position, and digestion of food, is a near com¬
posite of the daily life, but a period of this length gives no true knowledge
with regard to the basal metabolism, the increment due to change in
position, or the increment due to food. All of these features must be
determined in short periods.
It was recognized at the outset that it would be impossible to attempt to
prescribe any definite, predetermined degree of muscular activity or repose
m the case of these non-cooperating ruminants. The peak effect of the
digestion of food was avoided in the short periods of measurement by
studying the animal 24 hours after the ingestion of food, and variation in
body position was avoided by making it impossible for the animal to lie
down, although the activity during standing was not controllable and there¬
fore variable. The animals were prevented from lying down primarily
because it was assumed that there is a difference of from about 10 to 30 per
cent in the metabolism of an animal in the standing as compared to the
lying position. It was impossible to make the animal lie down and remain
lying the entire time, but he could be kept standing up. Under these con¬
ditions the so-called “standard metabolism” measurements were made. Are
measurements of the metabolism under such conditions suitable for pre-
186 METABOLISM OF THE FASTING STEER
Table 52. — Metabolism of fasting steers, measured in three consecutive 24-hour periods
Steer,
date,
live weight, and
average chamber
temperature
(1924)
Hours
standing
Hours
lying
Hours
without
food to
begin¬
ning of
experi¬
ment
Carbon
dioxide
pro¬
duced
in 8
hours
Respira¬
tory
quo¬
tient
Heat pro
Total
duced per
Per
500 kg.
24 hours
Per
sq. m.
Steer F:
gm.
cal.
cal.
cal.
Apr. 1 .
4 ^
3^
24
881.6
0.84
7,800
13,200
2,060
295.2 kg...
3 X
32
844.8
(.80)
7,700
13,000
2,040
11.6° C.. .
iy2
ey
40
744.0
(-78)
7,000
11,900
1,850
Average ....
9y
14H
823.5
7,500
12,700
1,980
Apr. 2 .
4
4
48
750.4
(.76)
7,200
12,700
1,960
(283 . 0 kg.)
6
2
56
737.6
(.74)
7,200
12,700
1,960
16.3° C.. .
2
6
64
700.8
(.73)
6,900
12,200
1,880
Average. . .
12
12
729.6
7,100
12,500
1,930
Apr. 3 .
5
3
72
705.6
(.71)
7,100
13,100
1,970
*271.8 kg...
5
3
80
699.2
(.71)
7,100
13,100
1,970
18.0° C.. .
2
6
88
689.6
.71
7,000
12,900
1,940
Average .
12
12
698.1
7,100
13,000
1,960
Steer E .
Apr. 9 . . . .
6
2
24
886.3
.82
8,000
14,300
2,190
280.0 kg...
6
2
32
786.9
(.80)
7,200
12,900
1,970
17.7° C.. .
6
2
40
810.2
(.78)
7,600
13,600
2,080
Average .
18
6
827.8
7,600
13,600
2,080
Apr. 10 .
7
1
48
728.8
(.76)
7,000
13,000
1,960
(270.0 kg.)
3
5
56
728.1
(.74)
7,100
13,100
1,980
17 4° C
3
5
64
736.5
(.73)
7,300
13,500
2,040
Average .
13
11
731.1
7,100
13,200
1,990
Apr. 11 .
5
3
72
763.7
(.71)
7,700
14,800
2,200
260.8 kg...
8
0
85
1 713.6
.71
1 7,200
113,800
1 2 , 060
18.0° C... .
3
5
88
659.7
.71
6,700
12,800
1,890
Average. . .
16
8
712.3
7,200
13,800
2,050
Steer C:
Apr. 23 .
5
3
24
1,317.2
.89
11,100
8,300
1,760
669.6 kg...
3
5
32
1,171.0
(.80)
10,700
8,000
1,700
19.6° C... .
3
5
40
1,167.1
(.78)
10,900
8,100
1,730
Average .
11
13
1,218.4
10,900
8,100
1,730
Apr. 24 .
5
3
48
1,145.5
(.76)
10,900
8,500
1,770
(644.8 kg.)
4
4
56
1,035.9
(.74)
10,100
7,800
1,640
20.7° C... .
4
4
64
991.6
(.73)
9,800
7,600
1,590
Average .
13
11
1,057.7
10,300
8,000
1,670
Apr. 25 .
6
2
72
997.9
(.71)
10,100
8,100
1,680
620.0 kg...
4
4
80
963.5
(.71)
9,700
7,800
1,610
17.4° C....
4
4
88
944.6
.71
9,500
7,700
1,580
Average .
14
10
968.7
9,800
7,900
1,620
1 Based on a period of 2 hours and 58 minutes, because electric power went off at start of 8-hour
period.
METABOLISM DURING FASTING 187
Table 52. Metabolism of fasting steers, measured in three consecutive 24-hour periods — Cont.
Steer,
date,
live weight, and
average chamber
temperature
(1924)
Hours
standing
Hours
lying
Hours
without
food to
begin¬
ning of
experi¬
ment
Carbon
dioxide
pro¬
duced
in 8
hours
Respira¬
tory
quo¬
tient
Heat produced per 24 hours
Total
Per
500 kg.
Per
sq. m.
Steer D:
am.
cal.
cal.
cal.
May 14 .
8
0
24
1,499.7
0.92
12,300
9,300
1,960
664.6 kg.. .
6
2
32
1,437.0
(.80)
13,200
9,900
2,100
24.4° C... .
5
3
40
1,246.1
(.78)
11,700
8,800
1,860
Average .
19
5
1,394.3
12,400
9,300
1,970
May 15 .
5
3
48
1,264.9
(.76)
12,100
9,400
1,970
(643.0 kg.)
4
4
56
1,256.0
(.74)
12,300
9,600
2,000
24.4° C... .
3K
4M
64
1,133.6
(.73)
11,200
8,700
1,820
Average .
12 y2
HH
1,218.2
11,900
9,200
1,930
May 16
5
3
72
1,170.8
(.72)
11,700
9,400
1,940
621.4 kg.. .
4
4
80
1,129.8
(.72)
11,300
9,100
1,880
22.4° C... .
4
4
88
1,128.6
.72
11,300
9,100
1,880
Average .
13
11
1,143.1
11,400
9,200
1,900
dieting the 24-hour metabolism of a stall-confined animal? Are they suit¬
able for computing the basal or the lowest metabolism of an animal, or do
they have the same error involved in the 24-hour experiments with men,
in that the variable activity makes computations of any fundamental
values highly unsatisfactory?
In the discussion of the 2-day fasts (see p. 184) it was pointed out that
the 24-hour heat-production per square meter of body-surface was invari¬
ably higher and generally much higher than the conventional 1,000 calories
commonly ascribed to all warm-blooded animals. It was suggested that
this might be due to the environmental temperature and to the fact that
our animals were standing instead of lying. To rule out the error in the
computation of the 24-hour metabolism from a 2-hour period of measure¬
ment, it was decided to make some experiments with the animal fasting
inside the respiration chamber, to begin the experiment 24 hours after the
last food was eaten, and to continue it for three consecutive 24-hour periods.
The animal was to be allowed to lie or stand at will. No food was given,
but drinking-water was supplied. The length of time that the animal stood
and lay down was carefully recorded. The usual kymograph records of
the activity of the animal in the chamber stall were kept, although the
records were at times vitiated by defects in the tambour, so that they do
not serve the purpose of exactly quantitating the degree of activity in all
cases. The temperature element was ruled out, in that essentially the same
temperature was maintained on each day in any given experiment with an
animal. In the different experiments with the different animals there were,
however, small differences in temperature (see p. 189). Four such experi¬
ments were made in April and May 1924, one with each of the four steers.
The results are tabulated in Table 52.
188
METABOLISM OF THE FASTING STEER
Prior to these experiments, a 24-hour respiration experiment had been
made with steer C, primarily to test the feasibility of making 24-hour
experiments with this apparatus and with our undermanned staff. A
technique was finally devised whereby 24-hour experiments could be carried
out and the carbon-dioxide production collected in 8-hour periods. It was
impossible to secure duplicate aliquots of the chamber air during these
8-hour periods, and each carbon-dioxide measurement therefore depends
upon the increment in weight of one set of absorbing bottles, which were *
connected with and disconnected from the ventilating system at the begin¬
ning and end of each period. Utmost precautions were taken to check not
only the actual weights on the pan, but to check the oscillation of the
balance and to check the absence of gaskets used to connect the bottles
with each other. Every precaution was therefore taken to avoid errors in
weight. But the determinations were not made in duplicate, and hence are
remotely liable to possible error. From a subsequent examination of the
data, however, we feel confident that rarely can the presence of an error be
suspected. As pointed out in an earlier discussion of the technique used
with this apparatus,0 after several months’ experience with a double system
of absorbers in which duplicate quantities of air were collected, the agree¬
ment between duplicate samples was almost without exception of the highest
order, particularly after the first few months of experimentation. This
agreement in duplication was so exact that we felt justified in reducing the
number of absorbing trains to one for each period, thereby making it pos¬
sible for our small staff to carry out these long experiments. Originally it
was planned to use the apparatus only for a series of perhaps four half-hour
periods, in which to a certain extent each half-hour period would be a check
upon the other periods. Although duplicate measurements were not pos¬
sible in the 8-hour periods, each subsequent 8-hour period may be looked
upon as a check upon the one prior to or following it, particularly when the
animal is fasting. In the transitional period from feeding to fasting such
can not, of course, be the case. On the whole, however, the possibility of
error is remote, but we feel it our duty to call attention to it.
The carbon-dioxide measurements reported in Table 52 were all made in
8-hour periods, save in the second period on April 11 with steer E, when,
owing to an unavoidable interruption in electric power, it was possible to
secure a measurement only for 2 hours and 58 minutes. In this case, how¬
ever, an analysis of the carbon-dioxide residual in the chamber was made
at the beginning and end of the period so as to make it possible to compute
the 8-hour carbon-dioxide production from the measurement for 2 hours
and 58 minutes. Although the discussion of these experiments will be based
for the greater part upon the computations on the 24-hour basis, the carbon-
dioxide measurements are reported on the 8-hour basis because they were
actually determined in this length of time and will serve to show the trend
of the fasting metabolism, particularly on the first day.
The respiratory quotient was determined at the beginning of the first
8-hour period of the three days and again at the end of the fast. For the
computation of the heat values in the intervening periods when the respira-
* Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 67.
METABOLISM DURING FASTING
189
tory quotient was not actually determined, assumptions have been made,
based upon an extensive series of actual determinations with animals under
conditions closely approximating those obtaining in these experiments. The
rate of fall in the respiratory quotient is obviously most rapid on the first
day, but on the third day the quotient was found to be almost uniformly a
fasting quotient of 0.71 or 0.72. It would have been preferable to have
determined the respiratory quotient in each period, but this was impossible
with the small staff at our disposal. It is hardly probable, however, that
any serious error has been introduced by the interpolated quotients given in
The heat-production during each 8-hour period is recorded on the usual
three bases of the total 24-hour heat-production, and the 24-hour heat-
production per 500 kg. of body-weight and per square meter of body-
surface. Although it would seem as if this calculation should be made upon
the 8-hour basis, for purposes of comparison with the computed metabolism
in other experiments it seems best to make the calculations on the 24-hour
basis. The average heat-production for the day, however, has the greatest
value.
It is unfortunate that the chamber temperature could not have been the
same in the case of all four animals. On the first day of the first experi¬
ment, unexpectedly cold weather and a fall of snow made such heavy
demands upon our heating system that the temperature could not be main¬
tained above an average value of 11.6° C. On the other hand, in the
middle of May, the warm environmental temperature made it impossible
to carry out the experiment with steer D at a temperature below about
24° C., which prevailed for the 3 days.
For several weeks prior to these 3-day experiments the steers had been
receiving supposedly maintenance rations, but they had probably in no case
sufficiently recovered from the preceding period of submaintenance feeding,
followed by fasting, and the nutritive state was undoubtedly somewhat
below par. Steers C and D had fasted for 10 and 9 days, respectively, fol¬
lowing 10 weeks on a submaintenance ration, and then each was given 9
kg. of hay daily, a supposedly maintenance ration. Steer C was subjected
to a 4-day fast beginning on April 22, after having been only 39 days on
the ration of 9 kg. of hay to recover from the stringent ration reduction and
the 10-day fast. Steer D did not commence his 4-day fast until three weeks
later, so that he had a better opportunity for complete recuperation. Steers
E and F had likewise been subjected to a long period of submaintenance
feeding lasting 8 weeks, followed by a 5-day and a 6-day fast, respectively,
and then they were given a maintenance ration of 5 kg. of hay and 0.91 kg.
of meal daily for 4 or 5 weeks prior to the continuous 3-day metabolism
measurements. At this time they were distinctly underweight, for although
they weighed the same as they had 6 months before, when they were first
received at the laboratory, they should normally have weighed much more,
since they were young, growing animals. All four steers were therefore
under-nourished rather than over-nourished at the time of these experi¬
ments, and from the well-known influence of undernutrition upon metabo¬
lism, one could expect that these animals would have a low rather than a
190
METABOLISM OF THE FASTING STEER
high metabolism, and hence that the values found with them would be
minimum rather than maximum. It will be seen later (see p. 191) that
the metabolism per square meter of body-surface was as high in these
experiments as in the earlier fasts at the maintenance level of nutrition, and
we have reason to believe that if the level of nutrition at the time of these
experiments in 1924 had been a full maintenance one, the measured metabo¬
lism would have been even higher than it was found to be.
All four experiments began and ended between 7h 30m a. m and 8 a. m.
Each animal was inside the respiration chamber for 72 consecutive hours,
the first period beginning 24 hours after the last ingestion of food. (See
Table 11, p. 53, for record of last feed prior to the experiment.) The
body-weights were determined at the beginning and end of each experiment,
but the weight for the second day had to be assumed, based upon the aver¬
age of the initial and final weights. Steer C drank no water during his
experiment. Steer D drank 14 kg. The amount taken by steers E and F
is unknown.
An examination of the data in Table 52 for the hours spent in standing
and lying indicates that in the first experiment steer F spent in general
about half the day standing and half the day lying, although the lying
period on the first day was a little longer than the standing period. Some¬
times the lying period in any 8-hour period might be extended to 6 hours
or reduced to 1 or 2 hours, or the animal might stand the entire 8 hours. In
the fasts of 5 to 14 days the animals were inclined to spend from 14 to 15
hours each day lying down. In these continuous 3-day experiments, on the
contrary, the animals generally stood each day at least 50 per cent of the
time, for only on the first day of the fasts with steer F and with steer C
was the time spent in lying greater than the time spent in standing. The
kymograph records of activity are complicated by the fact that occasionally
the apparatus was defective. From an inspection of these records for the
3-day experiments in 1924, it would appear that steer D was somewhat
more restless than steer C, and steer E was more restless than steer F. A
general inspection of the kymograph records for all the experiments through¬
out the whole period of research also indicates that steer D was more rest¬
less than steer C, but that there was little difference between the activities
of steers C, E, and F. It is believed that steer D was, on the whole, a little
more restive than any of the other three animals, although in general all
of the animals were remarkably quiet inside the chamber. Our experience
with our first group of 12 steers in the research on undernutrition showed
the degree of restlessness which can be expected inside the respiration cham¬
ber from an untrained animal. Judged on the basis of this experience, steers
C, D, E, and F were highly trained and remained extraordinarily quiet even
for stall-confined animals.
The carbon-dioxide production usually falls off markedly in the succes¬
sive periods on the first day, and the decrease continues on the next two
days. The minimum value in every case occurs in the last period of the
experiment, indicating that the lowest carbon-dioxide production had not
been obtained at that time, a finding fully in conformity with the persistent
decrease in metabolism noted in the fasts of 5 to 14 days.
METABOLISM DURING FASTING
191
There is likewise usually a distinct decrease in the computed 24-hour
heat-production on the three successive days of each fast. Steers E and F
have a much lower heat-production than steers C and D. Thus, on the first
day of the fast the older steers had an average 24-hour heat-production of
about 11,600 calories, and the younger steers of about 7,550 calories. This
is instantly explainable by the large differences in body-weight, for the
young steers actually weighed less than half of what the older steers weighed.
Hence we are quite prepared to find that the heat-production of steers E
and F per 500 kg. of body-weight reflects strikingly the influence of the
younger protoplasm.
On the basis of uniformity in weight a decrease in the heat-production
still appears, although it so happens that with both steers E and F the
maximum heat-production per 500 kg. of body-weight is on the third day.
On the whole, however, the differences are not striking, and one is not justi¬
fied in saying that the heat-production per 500 kg. of body-weight under¬
goes any special alteration in the course of a 3-day fast beginning 24 hours
after the withholding of food. This being the case, it is not surprising that
the heat-production per square meter of body-surface usually remains uni¬
form during the fast. Steer D has a larger heat-production than steer C
on this basis, as on the other two bases, perhaps accounted for by his dis¬
tinctly greater activity. Steer C has a measurably lower heat-production
per square meter of body-surface than the younger animals, E and F, but
steer D has essentially the same heat-production per square meter of body-
surface as does steer F, a fact which might be cited as excellent evidence in
favor of the idea of uniformity in heat-production per square meter of
body-surface. Since the metabolism of steer D was influenced by greater
muscular activity than was the case with steers E, F, and C, the metabolism
of steer C should more properly be compared, perhaps, with that of steers
E and F. Such comparison shows that steer C has a much lower heat-
production per square meter of body-surface than either steer E or steer F.
The average heat-production of the two younger animals, on this basis, is
not far from 2,000 calories, as compared with an average value of 1,670
calories in the case of steer C. In other words, the younger animals have
a metabolism essentially 20 per cent higher than that of steer C.
These fasting values may be compared with those noted in Table 50 for
the heat-production per square meter of body-surface per 24 hours in the
period from 42 to 56 hours after the last food, naturally disregarding the
values for the fast in March 1924. The average heat-production of steer
C at this period of fasting in the longer fasts was 1,730 calories per square
meter of body-surface, i. e., essentially the same as the average value of
1,670 calories found in the 3-day experiment in April 1924. Similarly the
somewhat higher values noted with steer D in Table 52 are confirmed by
the data in Table 50 for the long fasts. The measurements on the first day
of the long fasts were made 22 to 32 hours after food, and those on the first
day of the fast in May 1924 were made 24 to 40 hours after food, so that
the time interval after food ingestion is essentially the same in both cases.
The average value noted for steer D in the long fasts, omitting that in
March 1924, is 2,100 calories as compared with 1,970 calories on May
192
METABOLISM OF THE FASTING STEER
14, 1924. For the second day the average value in the long fasts is slightly
below 1,800 calories as compared with 1,930 calories on the second day of
the 1924 experiment. On the third day three values in the long fasts are
around 1,800 calories, the remainder being all perceptibly below 1,800
calories, as compared with 1,900 calories on the third day of the fast in
May 1924.
These comparisons justify the conclusion that the short experiment of
four half-hour periods, even with the animal standing the entire time, gives
a computed heat-production which is not far from that found in 24-hour
periods when the animal is allowed to stand or lie at will. From the criti¬
cisms raised against the short period, one would infer that the values com¬
puted from short periods would in general be higher than those found in
long periods. This is not the case in the comparisons just made. It is true
that on the first two days of the fast of steer C in April 1924 values slightly
lower than the average values on the first two days of the long fasts are
recorded, but in the fast in April 1924 steer C was an undernourished
animal, having had but 5 weeks to recover from a 10-day fast which fol¬
lowed a long period of submaintenance. The heat-production of steers E
and F on the several bases of computation was higher in the continuous
3-day experiments than in the fasting experiments of February 1924, fol¬
lowing submaintenance feeding. Unfortunately, no fasting experiments
were made with steers E and F following maintenance feeding, on the basis
of four half-hour periods of measurement.
So far as the evidence goes, it points toward the legality of computing the
fasting metabolism from four half-hour periods of measurement. Indeed,
the justification for the use of the half-hour period is far greater in the case
of fasting experiments than it would be in the case of experiments when the
animals receive food regularly, for in the transitional stage following the
digestion of food the peak of digestive activity occurs at different periods,
depending upon the nature and the amount of food ingested. We have not
studied food problems in experiments of four half-hour periods, but we have
used the short half-hour periods in studying the influence of the ingestion
of food, that is, the rapidity of digestive activity and the increment in
metabolism due to such activity. These experiments will be considered
subsequently (see p. 222).
Comparison of the Metabolism During 2 Days on Food, Followed by 2
Days Without Food, at Maintenance and Submaintenance Levels
and at High and Low Environmental Temperatures
The state of nutrition has not been seriously considered, at least in the
case of humans, as affecting the fasting metabolism, but our experience
with steers in the series of long and short fasts indicated that the nutritive
level at which the fast begins has a great influence upon the fasting
metabolism. To study specifically the influence of different feed-levels,
therefore, a series of 4-day respiration experiments were made with steers
E and F in 1925. The animals were confined in the respiration chamber as
they would be in a stall in the barn, and were allowed to stand and lie at
will. During the first two days they received feed and drinking-water as
METABOLISM DURING TWO FEED DAYS AND TWO FASTING DAYS 193
usual. During the last two days no feed was given, but water was offered
as usual. In some experiments a maintenance ration of hay was given on
the 2 feed days and in others a submaintenance ration, the animals having
been upon the particular feed-level under consideration for at least 2 weeks
prior to the respiration experiment. The ration was, furthermore, altered
not only with regard to the quantity of metabolizable energy, but also quali¬
tatively with regard to the character of the feed, timothy hay being fed in
some experiments and alfalfa hay in others. The selection of the timothy
and alfalfa hay, however, was not made for the purpose of considering the
relative merits of these two feedstufifs for maintenance or for preparing the
animal to resist a fast, but because these two substances are by common
consent considered typically different in character, and it was desired, if
possible, to alter considerably the character as well as the quantity of the
ration.
The effect of extreme variations in environmental temperature was also
introduced in this series of 4-day experiments. In the earlier series of short
fasts the influence of environmental temperature had been studied, but it
was believed that in that series the picture of the effect of the environmental
temperature reflected only the first reaction of the animal to a sudden
change in temperature. Hence, in the 1925 series the animal was purposely
kept for approximately two weeks in a stall temperature essentially the
same as that which was to be maintained in the respiration chamber during
the 4-day experiment. Environmental temperatures varying from 23.3° C.
to as low as 3.6° C. were accordingly studied. So far as the comparison of
timothy and alfalfa hay is concerned, the data are reasonably complete for
both steers. Uncontrollable conditions with regard to the temperature,
however, made it impossible at times to secure as low a temperature and as
satisfactory uniformity in temperature control as was wished. The data in
this respect, therefore, are not complete for steer F, but are fortunately
more complete for steer E both at the maintenance and submaintenance
levels of nutrition.
The influence of a maintenance and submaintenance level of nutrition and
of two different feedstuffs upon the metabolism both during feeding and
fasting was thus determined. Furthermore, the plan of the experiments
made it possible to secure evidence as to the accuracy of the method of
computing the fasting katabolism from the measured metabolism of the
animal when upon two different feed-levels. Indeed, one of the main
objects of the experiments was to obtain information on this point. Other
evidence was furnished by this series of experiments regarding the influence
of the nutritive level, the character of the feed, and the environmental tem¬
perature upon the metabolism during the transitional stage on the first day
of fasting. It was believed that the profound effect of the submaintenance
ration upon the level of the fasting metabolism would be reflected somewhat
in the metabolism when the animal was receiving submaintenance rations,
and particularly in the transitional stage on the first day of fasting. Indeed,
the measurement of the metabolism during this transitional period would
serve to indicate the value of the different types of feed and of the two
different nutritive levels in enabling the animal to withstand the fast,
194
METABOLISM OF THE FASTING STEER
inasmuch as it would give an idea as to the rapidity and intensity of the
drafts upon the body compounds. In addition, the determination of the
actual level to which the metabolism falls during two days of fasting should
furnish an excellent control upon the earlier measurements made in short
half-hour periods and, indeed, should compare reasonably well with the
level noted in the continuous 3-day fasting experiments made in the spring
of 1924.
The data secured with steers E and F during this series of 4-day experi¬
ments are summarized in Table 53. Each day began at 4h 30m p. m. The
carbon-dioxide production was determined quantitatively in two 8-hour
periods and two 4-hour periods each day. The residual air inside the res¬
piration chamber was analyzed at the end of each period, and the respiratory
quotient was determined for nearly every period. The data are therefore
available for computing the heat-production during each of the 8-hour
periods as well as during the entire 24-hour periods. Space does not permit
the printing of all the 8-hour values, unfortunately, and in Table 53 only
the 24-hour values have been recorded. It is believed, however, that the
picture of the metabolism under the special conditions studied will be best
illustrated by these 24-hour values, since the difficulty of working with a
non-cooperating ruminant makes the use of the 8-hour period, particularly
during feed days and in the transitional stage from feeding to fasting, of
questionable value. If it were possible to rule out muscular activity while
studying the metabolism during the first 48 hours after the withholding
of food, then a 4-hour or 8-hour period of measurement would be of great
importance.
In accordance with the method of calculation employed in presenting the
energy values in the earlier fasts, the heat-production during these 4-day
experiments has been computed from the carbon-dioxide production and the
respiratory quotient in all cases where the respiratory quotient was 1.00 or
below, and from the computed oxygen consumption and the calorific value
of oxygen at a quotient of 1.00 in those cases where the respiratory quotient
was above 1.00. (See pp. 147 to 150.) The heat values are reported on the
three bases of the total heat-production per 24 hours and the 24-hour heat-
production per 500 kg. of body-weight and per square meter of body-surface.
It was impossible to weigh the animal except at the beginning and end
of these experiments. Hence the body-weights on the intermediate days
are interpolated, on the assumption that during the first two days with feed
the body-weight would remain unchanged and that on the first fasting day
there would be a decrease equivalent to the amount of the daily ration
withheld. The body-weight reported in Table 53 for the first day of each
experiment is not, however, the weight on that particular day, but is an
average weight based upon the weight on that day and on 6 days preceding.
The urine voided was collected each day with but few exceptions. The
feces could not be collected daily and were allowed to accumulate in a large,
air-tight container underneath the respiration chamber (see Fig. 2, p. 26).
In the belief that there would be a distinct difference in the general
physical activity of the animal on days with feed and days without feed,
kymograph records of the degree of activity were kept and an approximate
METABOLISM DURING TWO FEED DAYS AND TWO FASTING DAYS 195
Table 53. — Summary of 4-day respiration experiments with steers E and F
Steer and date1
(1924-25)
Live
weight
Hours
standing
Hours
lying
Hay
eaten
in 24
hours2
Hours
without
food
to
begin¬
ning of
day
Average
stall
temper¬
ature
week
before
experi¬
ment
Average
chamber
temper¬
ature
Heat produced per 24 hours
Total
Per
500 kg.
Per
sq. m.
Steer E :
kg.
kg.
°C.
°C.
cal.
cal.
cal.
Dec. 12-13 .
368.8
14
10
7.0
0
24
22.5
11,800
16,000
2,720
Dec 13-14.
(368.8)
11
13
7.0
0
22.5
11,500
15,600
2,650
Dec 14-15 .
(361.8)
9)4
14)4
0.0
8
22.2
8,900
12,300
2,070
349.4
7 )4
16}4
0.0
32
22.1
7,700
11,000
1,830
Jan. 13-14 .
351.4
13
11
3.5
0
25
22.3
8,200
11,700
1,940
Jan. 14-15 .
(351.4)
10 Yi
13J4
3.5
0
22.7
7,900
11,200
1,870
(348.0)
10)4
13)4
0.0
24
22.6
6,800
9,800
1,620
Jan 16-17 .
333.4
12 y2
11)4
0.0
48
22.6
6,000
9,000
1,470
Feb. 2- 3 .
337.6
17 'A
6)4
3.5
0
4
4.7
9,000
13,300
2,190
Feb 3- 4
(337.6)
11
13
3.5
0
5.1
9,200
13,600
2,240
Feb 4- 5 .
(333.8)
17
7
0.0
24
5.7
7,200
10,800
1,760
Feb. 5-6 _
322.8
11)4
12J4
0.0
48
8.8
6,500
10,100
1,630
Feb. 27-28 .
359.0
10)4
13)4
7.0
0
11
3.6
11,000
15,300
2,580
Feb. 28-Mar. 1... .
(359.0)
9
15
7.0
0
6.1
11,200
15,600
2,620
(352.0)
8)4
15)^
0.0
8
9.6
8,800
12,500
2,090
338.2
12
12
0.0
32
4.6
7,800
11,500
1,900
Mar. 16-17 .
352.8
11
13
7.0
0
23
21.7
11,600
16,400
2,740
Mar 17-18 .
(352.8)
10)4
1314
7.0
0
22.0
11,400
16,200
2,700
Mar 18-19 .
(345.8)
7 )4
16)4
0.0
8
21.6
8,300
12,000
1,990
Mar. 19-20..
339.0
8
16
0.0
32
22.3
7,000
10,300
1,700
Apr. 14-15 .
362.8
13H
10)4
7.0
0
22
22.9
11,500
15,800
2,670
(355.8)
4
20
0.0
8
21.8
7,600
10,700
1,790
Apr. 16-17
350.4
6)4
17)4
0.0
32
21.7
6,700
9,600
1,590
May 4- 5 .
346.6
9M
14)4
3.5
0
23
22.6
7,800
11,300
1,860
(346.6)
9)4
14)4
3.5
0
22.1
7,700
11,100
1,840
(343.2)
7)4
16)4
0.0
24
22.2
5,400
7,900
1,300
May 7- 8
339.0
9 )4
14)4
0.0
48
22.0
5,500
8,100
1,330
Steer F:
Dec. 17-18 .
435.2
9
15
7.0
0
23
22.5
11,900
13,700
2,470
Dec 18-IP .
(435.2)
11
13
7.0
0
22.3
11,900
13,700
2,470
Dec 19-20
(428.2)
9 14
14)4
0.0
8
22.4
9,300
10,900
1,950
Dec 20-21
415.8
7)4
16)4
0.0
32
21.3
8,100
9,700
1,730
Jan. 19-20 .
408.6
14
10
3.5
0
24
21.9
9,200
11,300
1,990
(408.6)
10
14
3.5
0
22.2
8,800
10,800
1,900
(405.2)
10
14
0.0
24
22.3
7,100
8,800
1,540
399.6
10 )4
13)4
0.0
48
21.7
6,500
8,100
1,420
Feb. 13-14 .
394.6
13
11
3.5
0
13
9.2
9,400
11,900
2,070
Feb 14-15
(391.2)
11
13
0.0
24
10.2
7,500
9,600
1,660
Feb. 15-16.
383.2
12
12
0.0
48
10.6
7,000
9,100
1,570
Mar. 23-24 .
423.2
13 )4
10)4
7.0
0
25
22.1
12,500
14,800
2,640
Mar 24-25
(423.2)
10)4
13)4
7.0
0
22.5
12,600
14,900
2,660
(416.2)
9)4
14^
0.0
8
22.7
9,100
10,900
1,940
Mar 26-27
399.8
10J4
13H
0.0
32
22.2
7,700
9,600
1,680
Apr. 20-21 .
424.0
11
13
7.0
0
21
22.5
12,300
14,500
2,590
Apr. 21-22 .
(424.0)
li)4
12)4
7.0
0
22.3
12,300
14,500
2,590
(417.0)
9J4
14)4
0.0
8
23.3
8,700
10,400
1,860
Apr. 23-24
(410.0)
(8)
(8)'
0.0
32
21.7
7,500
9,100
1,620
Apr 24-25
4 404 . 2
4 8
4 8
0.0
56
22.4
7,600
9,400
1,650
May 11-12 .
407.0
12)4
11)4
3.5
0
21
22.0
9,100
11,200
1,970
May 12-13
(407 0)
13
11
3.5
0
23.2
9,000
11,100
1,950
May 13-14
(403.5)
8)4
15)4
0.0
24
22.7
6,300
7,800
1,370
May 14-15 .
392.6
11 ”
13
0.0
48
21.7
6,200
7,900
1,370
1 Beginning and ending at 4h 30m p. m.
* Timothy hay fed to both steers, until Mar. 6, 1925, in the case of steer E, and Mar. 9, 1925, in the case
of steer F; alfalfa hay fed thereafter.
* Records incomplete for 24 hours.
4 Experiment only 16 hours long. Data computed to 24-hour basis.
196
METABOLISM OF THE FASTING STEER
assessment of the quantitative degree of activity has been made for each
of the different experimental periods. In discussing the result we shall
therefore be able to state with considerable confidence whether the activity
was materially different on the different days of the experiments. Complete
records with regard to the number of hours spent in lying and standing were
also secured and are given in Table 53.
The two animals used for this work were essentially of the same age and
size, although steer E was actually somewhat smaller than steer F, weighing
369 kg. at the beginning of the series of experiments as compared with steer
F’s weight of 435 kg. Both animals, in the period from December 1924 to
May 1925 lost about 30 kg. as a result of the winter’s experimental regime,
which included 13 or 14 intermittent fasting days. A general effort was
made between the fasts to make up in part for the lost feed, but it is clear
that there was not complete compensation, as is shown by the loss in body-
weight.
Influence of Quantity and Character of Ration Upon Metabolism During Feeding
These 4-day experiments were made primarily to study the effect of
fasting upon the metabolism, but, in the attempt to establish standard
feeding conditions prior to the fasting, information was also secured regard¬
ing the metabolism during maintenance and submaintenance feeding with
two different kinds of hay, timothy and alfalfa. Their influence upon the
metabolism is of special interest, owing to the great economic problems
involved in the rationing of domestic animals. It is not our purpose, how¬
ever, to enter into an extensive treatment of the economic value of these
two feedstuffs, for the feeding experiments were not made primarily with this
in view. The observations are of significance, however, in indicating the
nutritive plane of the animal prior to the complete withdrawal of food and
furnish a base-line for the study of the effect of fasting.
Ib Table 53 the values for the total heat-production per 24 hours have
been recorded, but since steers E and F differed somewhat in weight, this
discussion will be confined to a consideration of the heat-production per
500 kg. of body-weight per 24 hours. The picture will be essentially the
same with the heat-production per square meter of body-surface per 24
hours, but the consideration of these values will be deferred for later, more
critical analysis from another point of view (see pp. 218 to 222).
The effect upon the heat-production of a maintenance ration of 7 kg. of
hay was studied with steer E on four occasions. In two cases the ration
consisted of timothy hay and in two cases of alfalfa hay. With steer F
one experiment was made with a maintenance ration of timothy hay and
two experiments were made with a maintenance ration of alfalfa hay. In
all but one instance, i. e., on February 27 to March 1 with steer E, the
environmental temperature was essentially 22° C., and for the moment,
therefore, the effect of environmental temperature may be disregarded.
When steer E was on a maintenance ration, the heat-production per 500 kg.
of body-weight per 24 hours ranged from 15,300 to 16,400 calories, the
higher values being noted with the alfalfa hay. With steer F the values
range from 13,700 to 14,900 calories, the alfalfa hay again resulting in a
METABOLISM DURING TWO FEED DAYS AND TWO FASTING DAYS 197
higher heat-production. Both animals, therefore, have essentially a some¬
what higher heat-production with the maintenance ration of alfalfa hay.
The smallness of our staff made it impossible to carry out complete
digestion experiments and nitrogen metabolism experiments, and the metabo¬
lizable energy in these two different rations could not be determined. There
is little, if any, reason to believe, however, that such determinations would
materially alter the conclusions as presented, for we are dealing here with
the heat-production, under the same conditions, of animals which are seem¬
ingly strictly comparable. It should be pointed out, however, that alfalfa
hay is nitrogen-rich and timothy hay is nitrogen-poor, and that undoubtedly
on timothy hay, and possibly on alfalfa hay, the animals were actually
losing nitrogen.0
Since these experiments were planned primarily to note the effect of main¬
tenance and submaintenance feed-levels and variations in environmental
temperature upon the metabolism during feeding and fasting, the compari¬
son of the influence of timothy and alfalfa hay was only an incidental study.
The discussion of the influence of these hays upon the metabolism at the
submaintenance level is therefore somewhat complicated by the fact that
in these submaintenance experiments marked differences in temperature
designedly prevailed. We will consider for the moment, therefore, only
those submaintenance experiments in which the chamber temperature was
not far from 20° C.
When a submaintenance ration of 3.5 kg. of either timothy or alfalfa hay
was given, the metabolic level of both steers during feeding was lowered
decidedly. Thus, we find that with steer E the 24-hour heat-production
per 500 kg. of body-weight during feeding with timothy hay has changed
from an average maintenance level of 15,800 calories on December 12-13
and December 13-14 to an average submaintenance level of 11,500 calories
on January 13-14 and January 14-15. With alfalfa hay, the metabolism
has fallen from a maintenance level of 15,800 calories on April 14-15 to a
submaintenance level of 11,200 calories on May 4-5 and May 5-6. With
steer F the 24-hour heat-production per 500 kg. of body-weight during
maintenance feeding on timothy hay was 13,700 calories on December 17-18
and December 18-19, but fell with submaintenance feeding to an average
of 11,000 calories on January 19-20 and January 20-21. With alfalfa hay
the maintenance level in April was 14,500 calories and the submaintenance
level in May was 11,200 calories.
From these data it can be seen that the submaintenance level of metabo¬
lism was much lower than the maintenance level in the case of both steers.
Moreover, the submaintenance level of metabolism was essentially the same
with both steers, regardless of the character of the hay, but since the main¬
tenance level of metabolism of steer E was greater than that of steer F, the
fall in his metabolism to the submaintenance level is somewhat more pro¬
nounced. The fall in metabolism with both steers is slightly greater with
alfalfa than with timothy hay. In view of the well-known difficulties of
* Armsby and Fries, (U. S. Dept. Agric., Bureau Animal Industry Bull. 51, 1903, p. 9) found
that timothy hay was too poor in protein to be used as a maintenance ration and added linseed
meal to the ration.
198
METABOLISM OF THE FASTING STEER
making direct comparisons of the heat-production of animals with which
digestion experiments are not simultaneously carried out, conservative treat¬
ment of these findings is necessary. In the submaintenance experiments,
undoubtedly both animals were losing nitrogen heavily. From our earlier
research on undernutrition in steers, in which we found that submaintenance
feeding did not materially alter the digestibility of the ration,0 it is assumed,
however, that the digestibility of the feed remained essentially the same as
it was when the steers were on maintenance rations.
Influence of Quantity and Character of Ration Upon Metabolism During Fasting
For the study of fasting per se, the metabolism measurements on the two
days of fasting in the several experiments claim our greatest attention.
Considering again the heat-production per 500 kg. of body-weight, we note
that as usual in all of the experiments the heat-production on this basis
decreased markedly on the fasting days and was in general lower on the
second of the two days. From our analysis of the data for the longer fasts,
however, it is obvious that a still further reduction in the heat-production
would occur if the fast were prolonged beyond two days, and that undoubt¬
edly at the end of two days the period of true fasting (i. e., when the con¬
tributions from the feed residues in the intestinal tract would have prac¬
tically ceased) has not yet been reached.
The metabolism on the first day of fasting following submaintenance
feeding was lower than that following maintenance feeding. According to
the experimental plan in these 4-day experiments, however, the first day
of fasting following maintenance rations represents a period beginning 8
hours after the last feed and continuing until 32 hours after the last feed.
Following submaintenance rations, it represents a period beginning 24 hours
and continuing until 48 hours after feed. These differences in the time
represented by the first day of fasting are due to the differences in feed-level.
Thus, in the submaintenance experiments, feed was given only once a day
and at such a time during the day as to bring the beginning of the third
experimental day (or the first day of fasting) 24 hours after the last feed.
In the maintenance experiments the feed was given twice a day, and the
first day of fasting therefore began only 8 hours after feed. It is important
to bear this in mind in the interpretation of the results, for in the submain¬
tenance experiments the fasting-period is distinctly longer than in the main¬
tenance experiments. Hence the markedly lower metabolism found on the
first day of fasting in the submaintenance experiments may be in part
accounted for by the fact that this day represents a later period in the fast
than does the first day of fasting in the maintenance experiments.
The influence of the character of the hay upon the actual fasting metabo¬
lism at the different nutritive levels may best be compared by considering
only those experiments in which the environmental temperature is similar.
On the first day of fasting after maintenance feeding with timothy hay the
heat-production of steer E per 500 kg. of body-weight is 12,300 calories.
This drops on the second day to 11,000 calories. Under similar conditions
with alfalfa hay, the metabolism is 12,000 calories on the first day of fasting
° Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 131.
METABOLISM DURING TWO FEED DAYS AND TWO FASTING DAYS 199
and drops to 10,300 calories on the second day. The decrease is thus 1,300
calories in the first case and 1,700 calories in the second case. In a second
experiment with steer E with alfalfa hay (April 14 to 17) the decrease is
I, 100 calories from the first to the second day of fasting.
With steer F there was a drop of 1,200 calories from the first to the second
day of fasting in the December fast, following a maintenance ration of
timothy hay. In the March fast following the maintenance ration of alfalfa
hay there was a decrease of 1,300 calories, and in the April fast under the
same conditions a fall of 1,300 calories. In this latter fast the metabolism
was also measured for the first 16 hours of the third day of fasting, and has
been computed to the 24-hour basis. No appreciable difference in metabo¬
lism, however, is to be observed between the second and third days of fasting
in this April fast with steer F.
In general, distinctly lower values are found on the two fasting days fol¬
lowing maintenance feeding with alfalfa hay than following maintenance
feeding with timothy hay.
In the submaintenance experiments at or about 20° C., essentially the
same metabolism per 500 kg. of body-weight was noted during the two feed
days, with both hays and, indeed, with both animals, i. e., not far from
II, 000 calories per 24 hours. On the first day of fasting, that is, 24 to 48
hours after food, steer E had a metabolism of 9,800 calories following the
submaintenance ration of timothy hay and 7,900 calories following the
ration of alfalfa hay. With steer F the corresponding figures are 8,800
calories and 7,800 calories, respectively. Thus, both animals have a strik¬
ingly lower level of metabolism following a submaintenance ration of alfalfa
hay. On the second day of fasting, in the same series of experiments, steer
E had a heat-production of 9,000 calories following the submaintenance
ration of timothy hay in January and 8,100 calories following the alfalfa
hay. Steer F produced 8,100 calories on the second day of fasting following
a submaintenance ration of timothy hay in January and 7,900 calories fol¬
lowing a submaintenance ration of alfalfa hay in May. There is therefore
also a distinctly lower metabolism with both of these animals on the second
day of fasting at the submaintenance level with alfalfa hay. It is to be
observed, however, that in the May experiments with both animals, essen¬
tially the same values were noted on the two days of fasting, there being a
slight rise on the second day.
The general picture of the influence of the two different feeds upon the
fasting level of metabolism, in experiments at environmental temperatures
ranging close to 20° C., is that the fasting metabolism of both animals was
decidedly lower after alfalfa hay than after timothy hay and that this
relationship persisted into the second day of fasting. Thus we have clear
evidence that following a ration of alfalfa hay, the nutritive level of the
animal calls for a fasting metabolism actually less than that following a
ration of timothy hay, whether the ration is a maintenance or a submain¬
tenance one. It is obvious that for the complete control of this finding,
experiments are highly desirable in which it is clearly established that the
animals are in nitrogen equilibrium on the full maintenance ration. On
submaintenance rations nitrogen loss is inevitable.
200
METABOLISM OF THE FASTING STEER
Influence of Environmental Temperature
Our earlier results on the influence of environmental temperature were,
on the whole, of such nature as to warrant the conclusion that the tempera¬
ture of the environment has no material influence on heat-production under
ordinary conditions, although some of the data did suggest that with the
lower temperature there was actually less heat produced. In the series of
4-day experiments reported in Table 53, there is clear-cut evidence of a
pronounced influence of temperature upon the metabolism when the other
factors which might influence the metabolism remain essentially constant.
This is particularly true in the case of the submaintenance experiments in
January and February with steer E, when timothy hay was fed. The second
of these two experiments was made at a much lower temperature (on the
average nearly 17 degrees lower) than the first, and the heat-production per
500 kg. of body-weight was actually considerably higher at the lower tem¬
perature. Thus, on the first two days with feed at the higher temperature of
22° C. the heat-production was 11,700 and 11,200 calories per 500 kg. of
body-weight. When the temperature was 4.7° and 5.1° C., respectively,
the heat-production on the two feed days rose to 13,300 and 13,600 calories,
an increase of approximately 17 per cent. On the first day of fasting fol¬
lowing the submaintenance ration the heat-production per 500 kg. of body-
weight was 9,800 calories at the higher temperature and 10,800 calories, or
11 per cent higher, at the low temperature of 5.7° C. On the second fasting
day the metabolism was 9,000 calories at 22.6° C. and 10,100 calories at
8.8° C., or 12 per cent higher. These experiments show definitely, therefore,
that the influence of environmental temperature at the submaintenance level
is noticeable, and that a difference of 17 degrees in the temperature has
made a difference of not far from 17 per cent in the metabolism, i. e., a
difference of 1 per cent in the metabolism for a change of 1° C. in tem¬
perature. The picture is not materially altered when the heat-production
is computed per square meter of body-surface, the cold temperatures result¬
ing in distinctly higher values.
With steer F, a comparison of high and low environmental temperatures
was likewise made in connection with his two submaintenance experiments
in January and February, with timothy hay. In the January experiment
the average chamber temperature was about 22° C. and in the February
experiment it was about 10° C. The difference in temperature was there¬
fore not so great as in the case of steer E, and the experiment at the lower
temperature included only one day, February 13-14, with feed. On this
day the heat-production per 500 kg. of body-weight was actually 7 per cent
higher than the average heat-production on the two feed days in the January
experiment. On the first day of fasting the metabolism at the lower tem¬
perature was 9 per cent higher and on the second day of fasting 12 per cent
higher.
With the two animals the picture of the influence of environmental tem¬
perature under submaintenance conditions is essentially the same. The
effect is, however, apparently not proportional to the difference in tem¬
perature, at least so far as can be judged from experiments with two differ¬
ent animals, for in the case of steer F the influence of a change in tempera-
METABOLISM DURING TWO FEED DAYS AND TWO FASTING DAYS 201
ture of approximately 12 degrees (the lowest temperature reached being only
about 10° C.) was essentially the same as that noted with steer E, which
was subjected to a difference in temperature of 17 degrees (the lowest tem¬
perature being about 5° or 6° C.). Such meager data do not permit of
drawing many conclusions, and it is probable that no definite mathematical
relationship can be established, such as has been suggested frequently in
the literature, i. e., that each degree fall in temperature results in a certain
definite (percentage) rise® in metabolism.
Pronounced temperature differences did not exist when the animals were
on alfalfa rations, either at the maintenance or submaintenance level of
nutrition, as the season was too far advanced for low temperatures. During
maintenance feeding with timothy hay, however, two experiments with steer
E are available, one in December and one in February, for a study of the
effect of low and high temperatures. In these two experiments, the influence
of the environmental temperature is entirely different from that when the
steer is on submaintenance rations. In the December experiment the aver¬
age chamber temperature was 22.3° C. and in the February experiment it
varied from 3.6° to 9.6° C., being on the average about 6° C. The differ¬
ence in temperature was thus essentially 16°. On the two feed days, when
7 kg. of timothy hay were eaten daily, the heat-production per 500 kg. of
body -weight was 16,000 and 15,600 calories at the high temperature and
15,300 and 15,600 calories at the low temperature. In other words, there
was essentially no difference in the metabolism, except for a slightly lower
value on the first of the low temperature days. On the first day of fasting
the metabolism at the high temperature was 12,300 calories as compared
with 12,500 calories at the low temperature, there being an inappreciable
increase on the cold day. On the second day of fasting the metabolism was
11,000 calories as compared with 11,500 calories, the increase being 5 per
cent at the low temperature. On the basis of the heat-production per square
meter of body-surface, the increase was 70 calories or 4 per cent on the
second fasting day. Thus, although with the low environmental temperature
there is seemingly an increase in the heat-production on the second fasting
day, the heat-production on the two food days is practically constant regard¬
less of the temperature, or in one instance is slightly lower at the low
temperature. One may therefore conclude that the difference in temperature
has practically no effect upon the metabolism when the steer is on a main¬
tenance ration of timothy hay. It is somewhat surprising that the difference
is not greater on the second day of fasting than was actually found. From
the evidence in the submaintenance experiments, where the lower nutritive
plane renders the animal seemingly more susceptible to the environmental
temperature, so that there is a demand for a greater heat-production at the
lower temperature, one would have expected in the fasts following main¬
tenance feeding a greater heat-production than is actually recorded on the
second day of fasting at the low environmental temperature.
The conclusion drawn from these data that a low environmental tempera¬
ture frequently has no influence upon the metabolism is fully in line with
“ Recently, Capstick and Wood (Journ. Agric. Sci., 1922, 12, p. 257) found with swine that as
the environmental temperature decreased below the critical temperature (21° C.), the heat loss
increased at the rate of about 4 per cent per degree.
202
METABOLISM OF THE FASTING STEER
the findings in the excellent research of Magee, who studied the influence
of variations in the external temperature upon the energy exchange of the
goat.0 Magee found that between 13° and 21° C. the metabolism is essen¬
tially constant. Below 13° C. it rises only slightly, but as the temperature
passes above 21° C. a pronounced gradual increase in the metabolism is
observed.
Influence of Lying and Standing
The computation of the heat-production per 500 kg. of body-weight and
per square meter of body-surface in these 4-day experiments represents an
attempt to equalize the differences in the body-size of the animals so that
the values for the different days of each experiment, and particularly the
values for the different animals, may be compared with each other. A still
further attempt to reduce the values to a more comparable basis would be
to compute the heat-production on the basis of uniformity in standing and
lying.* 6 Several methods of making this computation have been proposed,
all of them based upon too few experimental data. Our own observations
on the difference in metabolism in the lying as compared with the standing
position, although extensive, are not sufficiently extensive to be fully con¬
vincing. The information secured in our earlier experiments was contami¬
nated by irregularity in the movements of the animal, the uncertainty as
to when the animal would lie down or stand up, and the inclusion in the
lying period or in the standing period of the effort of getting down or of
rising. Since the conclusion of the fasting experiments with our four steers,
however, we have been able to obtain some clear-cut comparisons of the
metabolism during standing and lying, in experiments in which the effort of
changing from one position to the other has been ruled out. In many of
these experiments we observed that the difference in position resulted in a
difference of from 20 to 30 per cent in the metabolism on days with feed,
but that there was a tendency for this difference to diminish during fasting
and practically to disappear after the second or third day of fasting. In
other experiments, a difference in the metabolism of as much as 20 per cent
due to difference in body position persisted even to the fourth or fifth day
of fasting, although there were occasionally 8-hour periods when the differ¬
ence almost disappeared. It seems highly probable that the correction for
the difference in position is somewhat greater than that reported by Forbes,
Fries, and Kriss0 (see p. 211). Pending further information on this point,
however, the values in Table 53 for the 24-hour heat-production during the
series of continuous 4-day experiments have not been corrected to a standard
day of 12 hours standing and 12 hours lying.
It is obvious that these experiments, by their very nature, represent that
period of an animal's existence when the greatest influence of the activity
of standing and lying is to be found, comprising as they do two days on
feed and two days of fasting. Undoubtedly, the heat values would be some¬
what lower had they been determined exclusively when the animal was
° Magee, Journ. Agric. Sci., 1924, 14, p. 506.
6 Fries and Kriss, Am. Journ. Physiol., 1924, 71, p. 60.
e Ibid.; Forbes and Kriss, Journ. Agric. Research, 1925, 31, p. 1085.
THE BASAL METABOLISM OF STEERS
203
lying. Differences in muscular activity necessarily occur, however, during
a 24-hour day, especially when the animals are searching for and expecting
food. Such activity has been noted in the records of the number of hours
spent in standing and lying during the day, and, in addition, a relative
estimate of the degree of activity from day to day has been obtained from
the kymograph records. These records show that in general the activity
was not very great. Assessing the degree of activity as indicated on the
kymograph records on the crude basis of minimum (activity I), moderate
(activity II), and excessive (activity III) activity, we would say that in
many instances activity II occurred on the two feed days. This activity is
to be expected, since the animals were eating, digesting their feed, and
ruminating. The activity on the two fasting days, however, was usually
somewhat lower than on the two feed days- Undoubtedly, therefore, the
metabolism on the first two days with feed was influenced by a greater
degree of stall activity than the metabolism on the two fasting days. Only
when the animal is lying is the muscular activity reduced to a minimum.
Indeed, one might argue that if the animal remained absolutely quiet when
standing, the metabolism would not be much greater than when lying. This
argument is in part borne out by the fact that as the fast progresses and the
animal becomes less restive while standing, the difference in metabolism due
to the difference in body position tends to disappear. (See pp. 211 to 213.)
The Basal Metabolism of Steers
With humans it is argued that the metabolism measured 12 hours after
the last food and during complete muscular repose is the so-called “basal
metabolism" and that for comparative purposes it is permissible to com¬
pare the metabolism of one individual measured under these conditions with
that of another individual measured under the same conditions. Usually
these determinations are made in short periods and are supposed to repre¬
sent the minimum metabolism. The metabolism as thus determined is not,
however, the irreducible minimum, for undemutrition, fasting, and sleep
may result in an even lower metabolism. From the standpoint of physi¬
ology, it is important to measure the metabolism of various living organisms
under as nearly as possible constant conditions, in order to have a suit¬
able basis for the comparison of different individuals of the same and
different species.
It is impossible to secure complete muscular repose with ruminants, for
they are not cooperative. They can be forced to stand by hitching a chain
under the neck, but this procedure is ineffective after several hours, as they
become very restless and irritable under prolonged restriction. They will
not remain in the lying position for any definite length of time, and even
when they are lying there may be more or less movement of the body and
particularly the head. It would be ideal to measure the basal metabolism
of ruminants only when they are in the lying position and quiet. This is
usually impracticable, however, and the metabolism must be measured
under the conditions of stall activity, in which the animal has freedom to
rise or lie down at will and to perform those minor muscular movements
permitted by the rather narrow confines of the stall, though restrained by
204
METABOLISM OF THE FASTING STEER
the usual stanchion. The sum total of such activities is reasonably uniform
from day to day, however, as is strikingly shown in the continuous 4-day
respiration experiments with steers E and F, in which it was noted that
during the two days on feed the total 24-hour metabolism was almost always
the same on any two succeeding days.
With humans and carnivorous animals the food in the intestinal tract is
fairly rapidly absorbed. Immediately after the ingestion of food there is a
rise in the metabolism, but if no more food is taken, the metabolism gradu¬
ally decreases and after 12 hours a plateau is reached which persists prob¬
ably for 12 or more hours, during which time there is only an insignificant
alteration in the metabolism. Further abstinence from food results in a
lowered metabolism, and with prolonged fasting the metabolism falls off
appreciably. In the case of large ruminants there are large masses of feed
residues in the alimentary tract, which are absorbed only slowly, and even
after food is withheld, this intestinal content may contribute to the metabo¬
lism of the animal for some time by furnishing energy from material either
directly absorbed or elaborated by fermentative processes.
Prior to our study of undernutrition in steers, few respiration experiments
had been made with large ruminants in which feed was withheld for any
length of time. In our research on undernutrition, the metabolism of all of
the steers was measured for comparative purposes 24 hours after the last
food. In a few instances in 1919, measurements were made 50 or more
hours after food.® It was early recognized that although the digestion of
ruminants has by no means completely ceased 24 hours after the last feed,
the active peak of digestion has passed. Recent determinations of the
methane production of cattle in Armsby’s laboratory6 indicate that even
during the second 24 hours of fasting the methane production is relatively
high and, though it falls off rapidly during the first three days after feed,
it is not until the sixth or seventh day of fasting that the production is as
low as 2 or 3 gm. per day. Without doubt the methane production is a fair
index of the total digestive fermentation, but it is questionable whether
digestive activity as such has not essentially ceased even before the great
decrease in methane production takes place.
Although the stall confinement of cattle during respiration experiments
makes the degree of muscular activity during any comparative series of
metabolism measurements, especially during 24-hour periods of measure¬
ment, more or less uniform, it is almost impossible to secure a sharply
defined post-absorptive state in the ruminant. Experimental study is there¬
fore necessary to determine whether a fairly definite plateau of metabolism
is reached after the peak of digestive activity has passed, corresponding to
that noted with humans 12 hours after the ingestion of food.
Incidence of Plateau in Metabolism of Steers after Cessation of Active Digestion
In our series of long fasts (see Tables 48 to 50, pp. 173 to 178) it wad
pointed out that the heat-production, expressed on any of the usual three
bases of computation, decreases rapidly on the second day of fasting, that
is, the period beginning 42 to 56 hours after the last food. There is fre-
“ Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, Table 55, p. 210.
b Braman, Journ. Biol. Chem., 1924, 60, p. 85.
THE BASAL METABOLISM ‘ OF STEERS
205
quently a further decrease on the third day. An examination of the figures
in Table 49 (p. 176), leaving out of consideration the submaintenance
experiments in March 1924, with steers C and D, and the submaintenance
experiments with steers E and F, shows that in 12 experiments with steers
C and D approximately a plateau in metabolism was reached on the second
day in 4 cases, on the third day in 6 cases, and on the fourth day in only
2 cases. Hence it would seem as if in general on the third day, that is,
during the 24-hour period beginning between 65 and 80 hours after food, a
fairly uniform metabolism would be found, which would not be rapidly
altered during the following 24 or 48 hours, although the tendency for a
continuous decrease in metabolism with prolonged fasting is obvious. It
should be borne in mind, however, that the data given in Table 49 were
secured from only three or four half-hour periods of measurement, usually
in the forenoon, and in at least two cases the animals had just come in
from pasture. In the other cases, they were presumably at a maintenance
level of nutrition, but since their body-weights were somewhat different in
the different experiments, they were not necessarily in the same state of
nutrition in all experiments. Furthermore, the metabolism of steer D, on
the whole, was higher than that of steer C, in large part accounted for by
the fact that steer D was almost invariably somewhat more restless.
In the continuous 3-day experiments with steers C and D (see Table 52,
p. 186) the average heat-production of steer C per 500 kg. of body-weight
per 24 hours was practically uniform on the three successive fasting days,
being 8,100, 8,000, and 7,900 calories, respectively. The first value repre¬
sents a period between 24 and 48 hours after food, or the period beginning
24 hours after the last food. This period is essentially the same as that
represented by the first day of fasting in the fasts of 5 to 14 days (see
Table 49), but the value of 8,100 calories is measurably lower than the
average value found with steer C in the longer fasts. The same may be
said with regard to steer D. His heat-production on the three successive
days was 9,300, 9,200, and 9,200 calories, i. e., perceptibly lower than all
except one value found on the first day in the long fasts, namely, 8,500
calories in the fast in April 1922. The subsequent values in the April fast,
however, are also lower than the values found in the other long fasts. A
possible explanation of this low value of 8,500 calories may be the pos¬
sibility of error in the respiratory quotient, which was found to be 0.97
on this day, 32 hours after the last food. This was one of the first deter¬
minations of the respiratory quotient made with the new gas-analysis
apparatus and, judged from other measurements made at approximately
the same time after food, this value is distinctly high. If the quotient were
lower, the value for the heat-production would be increased somewhat, pos¬
sibly even to exceed the 9,300 calories noted in the fast in May 1924.
Another, and perhaps more logical, explanation of this low value in the fast
of April 1922, inasmuch as it would at the same time account for the low
values on the three subsequent days, is that at the time of the fast in
April 1922 steer D was distinctly in an undernourished condition. He had
been through two fasts during the winter, a 10-day fast three months
before, and actually weighed 621 kg. at the beginning of the fast in April
1922, as compared with 664 kg. on May 14, 1924.
206
METABOLISM OF THE FASTING STEER
Judging from the four continuous 3-day fasting experiments in 1924, if
one begins the experiment 24 hours after the last food, and the previous
ration has been a maintenance ration, the metabolism per 500 kg. of body-
weight on 3 successive days is essentially the same. Thus, one would be
justified in saying that a post-absorptive condition, or essentially a post-
absorptive condition, was obtained with the steer on a maintenance ration
of hay alone in a period beginning 24 hours after food was withheld, in
other words, a period twice as long as that ordinarily assumed for man.
Judging from the longer fasts, however, the plateau in metabolism occurs
on the second or even the third day, rather than on the first day, i. e., 24
hours after the last food. A strict comparison of the data in these two
series of fasts is complicated, however, by the fact that in one series the
animals were measured while standing and for only three or four half-hour
periods, and in the other series they were allowed to lie or stand at will and
the periods of measurement were 8 hours long. Therefore, direct compari¬
sons, without correcting for these differences of conditions, can not be made.
The conclusion as to the incidence of a plateau in metabolism following
the cessation of active digestion would seem to be better founded upon
24-hour experiments than upon short experiments of about 2 hours. Further
evidence on this point is available in the experiments made on steers E and
F from December 1924 to May 1925. In these experiments the metabolism
was measured in 8-hour periods during two days of fasting following two
days on feed, or during four days inside the respiration chamber. From an
inspection of the 8-hour values we find that with steer E, in December
1924, a plateau in metabolism is reached in approximately 16 hours after
the last feed. The time when the plateau in metabolism occurred in these
4-day experiments is recorded in Table 54, which shows that in general the
plateau begins 24 hours or later after the last food has been consumed. In
the submaintenance experiments it occurs in most cases somewhat later.
This is strikingly at variance with what one would expect, for one would
think that with the smaller intestinal content the effect of the previously
ingested feed would pass off more rapidly and the plateau, instead of being
delayed, would be more quickly reached. It was thought that striking
changes in temperature might possibly have an influence upon the time when
the plateau appeared. An inspection of the average chamber temperatures
recorded in Table 54, however, shows that environmental temperature is
practically without significance in this respect. From the series of con¬
tinuous 3-day fasting experiments inside the chamber, in which the animals
had previously been upon a maintenance level, it was inferred that 24 hours
after the last food was given a plateau in the metabolism of the steers was
reached which might be considered as comparable to the post-absorptive
metabolism of man. This is in general confirmed by the 4-day experiments
at the maintenance level, as seen from Table 54, but on the submaintenance
level this period is evidently somewhat delayed.
The Metabolic Plateau of the Same Animal when Fasting Under Different
Conditions
In the fasts of 5 to 14 days it was pointed out that a level in the fasting
metabolism might not occur until the second or even the third or fourth day
THE BASAL METABOLISM OF STEERS
207
of fasting. Another point to be considered is that the metabolism was
rarely the same with the same animal for the first day or even for subsequent
days of these different fasts, since the prefasting conditions were different.
Thus, excluding the experiment at the submaintenance level, the average
24-hour heat-production of steer C per 500 kg. of body-weight during four
half-hour periods in the standing position ranged from 8,800 to 9,800 calories
on the first day of fasting, i. e., 22 to 32 hours after food. With steer D the
differences were even greater, the metabolism ranging from 8,500 to 12,000
calories. Similar variations are found on the subsequent days. During the
first few hours following the time when the first feed is withheld, i. e., about
12 hours after the last feed, one expects considerable variability in metabo¬
lism, depending upon the nature and amount of the previous feed-level.
Whether the plateau indicating approximately basal metabolism will be at
the same level in all experiments when the animal is subsisting upon a
maintenance ration becomes a vital point at issue. In the different fasts
of 5 to 14 days with steers C and D, excepting those in March 1924, the
level of the plateau did vary, although this may have been due to the fact
that the rations preceding the fasts, which were supposedly maintenance,
consisted of hay in some cases and grass in others.
Table 54.- — Incidence of 'plateau in metabolism after cessation of active digestion,
in 4-day respiration experiments with steers E and F
Steer and
date of
experiment
Feed-level
Time after food
when plateau in
metabolism seems
to appear
Average
chamber
temperature
1924 to 1925
Steer E:
hrs.
°C.
Maintenance .
16
22
Do .
24
6
Do .
24
22
April .
Do .
24
22
January .
Submaintenance ....
40
22
Do .
32
6
May .
Do .
32
22
Steer F:
Dprpmhpr .
M aintenance .
16
22
Do .
32
22
April .
Do .
24
22
January .
Submaintenance .
32
22
Do . .
32
10
May .
Do .
24
22
The 4-day experiments with steers E and F in 1925 furnish additional
evidence on this point. Thus, the data for the 4-day experiments with
maintenance rations indicate that in the 8-hour periods of measurement
the level of the plateau may range from approximately 8,700 calories per
24 hours to 6,750 calories in the case of steer E, and from 8,700 to 7,650
calories in the case of steer F.“ In other words, the so-called “basal metabo-
• These values are calculated from the 8-hour periods of measurement and do not appear in
Table 53.
208
METABOLISM OF THE FASTING STEER
lism, when once attained after withholding of food, is seemingly not con¬
stant with the same animal, even if he has previously been upon a main¬
tenance feed-level. If these experiments at the maintenance level are
subdivided, however, according to whether the animal had been receiving
timothy or alfalfa hay, it is seen that the higher values occur following the
ration of timothy hay and the lower values following the ration of alfalfa
hay.
A submaintenance ration has been shown to lower the level of the fasting
metabolism markedly. The most important evidence on this point is
brought out by the fasts with steers C and D in March 1924, at the sub¬
maintenance level, when extraordinarily low values for both animals were
found. Similarly with the younger steers, E and F, at a submaintenance
level the heat-production per 500 kg. of body-weight per 24 hours on the
first day of fasting in February 1924 was, respectively, 10,900 and 10,300
calories. These same animals, when fasting at a maintenance level in April
1924, that is, about six weeks after the submaintenance experiments in
February 1924, had a fairly constant metabolism during three days, steer
E of 13,600 calories and steer F of 12,700 calories. In other words, as was
the case with steers C and D, the metabolism was materially lower on sub¬
maintenance rations and the two conditions represented plateaus at differ¬
ent levels. The 4-day experiments with steers E and F on submaintenance
rations furthermore show that although the fasting metabolism is on a
lower level than it was following maintenance feeding, the metabolic level
is higher following the submaintenance ration of timothy hay than it is
following the submaintenance ration of alfalfa hay.
Conclusions Regarding the Incidence and the Level of the Plateau in Metabolism
of Steers
On the basis of all the data available, one can conclude that vnth the
steer on essentially a maintenance ration a plateau of fairly constant
metabolism begins in many instances 24 hours after the last food, depending
somewhat upon the amount and nature of the food, and that this level will
remain essentially constant for three successive days. In some instances,
32 hours are required, singularly enough especially in those cases where the
steers were upon submaintenance rations. In all probability at the end of
48 hours the animal is in a condition which is comparable, at least, with the
so-called post-absorptive state in humans. It is difficult to give an exact
percentage valuation to the difference between the probable level of metabo¬
lism 24 hours after food as compared with that 48 hours after food, but
undoubtedly the peak of digestion has been passed 24 hours after the last
food and the measurements of metabolism at this time may certainly be
used for comparative purposes. Whether it is justifiable to assume that
with the average ruminant the metabolism determined 24 hours after the
last food represents the basal metabolism is highly doubtful. In general,
from our evidence one would say that the metabolism beginning 48 hours
after food is withheld would be less liable to fluctuation during the fol¬
lowing 48 hours than perhaps at any other point in the course of the
metabolism.
THE BASAL METABOLISM OF STEERS
209
According to the evidence secured in the long fasts with steers C and D
and in the 4-day experiments with steers E and F, the level in the plateau
of metabolism will vary with different seasons of the year and as a result
of changes in the quantity and character of the rations.
Since with steers it is impossible to insure complete muscular repose, since
it is difficult to secure complete cessation of digestive activity, and further¬
more, since the digestive activity of ruminants is relatively very great com¬
pared with that of humans, it is debatable whether any attempt to secure
the equivalent of basal conditions in man is necessarily advisable.
In all the foregoing discussion the conclusions have been based chiefly
upon the heat-production per 500 kg. of body-weight per 24 hours. But
since the surface area is a function of the body-weight, the conclusions
may also be based, without the slightest change in phraseology other than
that of numbers, upon the heat as computed per square meter of body-
surface per 24 hours.
Computation of the Fasting Katabolism of Steers from Experiments on Two
Different Feed-levels
The exact determination of the period of time following food intake when
the metabolism should be measured for purposes either of comparing the
basal metabolism of a ruminant with his metabolism immediately following
the ingestion of food or of comparing the basal metabolism of one ruminant
with that of other ruminants, other animals, or, indeed, man, is a matter of
considerable importance. With man the metabolism 12 hours after the last
meal is commonly used as the basis for the study of the influence of subse¬
quently superimposed factors, such as food, muscular activity, and a warm
or cold environmental temperature. To study the energy value of various
cattle feeds it is also highly desirable to be able to superimpose the effect
of the feed upon a metabolism determined under basal conditions.
Formerly it was considered that the basal or fasting katabolism could
be computed by the simple process of measuring the metabolism of an
animal when consuming daily a given amount of food, and subsequently
determining the metabolism of the same animal when consuming approxi¬
mately one-half of this amount of food. The difference in metabolism at
the two feed-levels was ascribed to the difference in the amount of the
ration, and the fasting katabolism was computed as a linear function of
this difference. This method was first proposed and applied by Professor
Armsby many years ago,® and was in large part based on his own conviction
that the actual fasting katabolism of ruminants could not be determined
definitely. In the spring of 1919, Professor Armsby visited the laboratory
at Durham, New Hampshire, and having seen the excellent manner in
which our large steers had withstood undemutrition for long periods of
time and having learned that we had made all of our respiration experi¬
ments at least 24 hours after the last food, stated that he believed more
prolonged fasting would be feasible and suggested that we continue our
fasting period to the fiftieth hour. It is significant that a fasting experiment
prolonged to 50 hours was made on May 5-6, 1919, i. e., at the time of his
° Armsby, Principles of Animal Nutrition, New York, 1906, 2d ed., p. 378.
210
METABOLISM OF THE FASTING STEER
visit. At the same conference Professor Armsby expressed himself as being
uncertain whether the method of computing the fasting katabolism from
two different feed-levels was as sound as he had originally believed. This
matter was touched upon in our report on undernutrition.®
Our experiments in which the fast was prolonged for 52 hours or more
show, as is to be expected, that there is a decrease in the carbon-dioxide
production, due to the fact that the respiratory quotient and the total
metabolism gradually decrease. Even in cattle the after-effect of food
apparently disappears rapidly, and the condition approximating the pre¬
requisite for basal metabolism measurements with man, so far as the
question of food ingestion is concerned, is attained with ruminants not far
from 32 to 48 hours after food is withheld. Prolonged fasting will lower
the metabolism still further, as was clearly shown with the man who fasted
for 31 days6 and as is shown in the fasts of 5 to 14 days with our steers.
But for the specific purpose of finding an approximate base-line for cattle,
to which the influence of the ingestion of food may be referred, and to
establish, if possible, a basal katabolism of steers for comparison with
other animals and humans, we obviously may not deal either with prolonged
fasting or prolonged submaintenance feeding, for this latter factor is like¬
wise shown to lower the metabolism pronouncedly. Indeed, the most ardent
advocates of the surface-area law insist that normal conditions of nutrition
should be maintained. A critical study of our fasting results suggests that
with animals under approximately normal conditions of nutrition the with¬
holding of food for 32 hours should give, so far as the influence of food is
concerned, favorable conditions for approximating the basal level. Even
then, as is seen from the metabolism measurements during the fasts of 5
to 14 days, large differences may occur in different experiments with the
same animal, although the nutritive condition, ruling out of such compari¬
son the experiments on a submaintenance level, may not be pronouncedly
different. This finding is in common with that not infrequently noted
with man, and speaks for an absence of strict uniformity in metabolism
even with the same individual, when changes in age are ruled out.
The object of this report is not primarily to study the effect of the inges¬
tion of food upon metabolism so as to make use of this base-line obtained
32 to 48 hours after food, but it is pointed out here that the results suggest
that this seems to be a logical procedure. From the standpoint of com¬
parative physiology it is important to compare the basal metabolism of the
steer determined under these conditions with that noted with other animals,
particularly man. Two decades ago there was an attempt, commonly attrib¬
uted to Erwin Voit,c to suggest complete uniformity in the heat-production
of all warm-blooded animals per unit of surface area. At that time almost
no attention was given to the degree of muscular activity, a factor now
known to be of great importance. The question of the presence or lack
° Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 257. We wish to explain
here that although our statement in our earlier publication refers solely to a letter received from
Professor Armsby, as a matter of fact several days’ intimate conference with him in Boston and at
Durham was the basis for our general statement of Professor Armsby’s beliefs.
1 Benedict, Carnegie Inst. Wash. Pub. No. 203, 1915.
* E. Voit, Zeitschr. f. Biol., 1901, 41, p. 113.
THE BASAL METABOLISM OF STEERS
211
of food in the stomach was also not seriously considered. The effect of
environmental temperature was only incidentally noted, and the method
for computing the surface area of the various species of animals was only
in its earliest stages of development. Under these conditions, however, it
was stated that throughout the entire animal kingdom the heat-production
was seemingly uniform, amounting to approximately 1,000 calories per
square meter of body-surface per 24 hours, when the animal was in a
normal state of nutrition.
In 1918, Armsby, Fries, and Braman® published a comparison of the
basal katabolism of cattle and other species, in which they pointed out
the difficulties of measuring or computing the basal katabolism of cattle.
By comparing the total metabolism on two different amounts of the same
feed and noting the increment in the heat-production per kilogram of dry
matter of the feed, they computed indirectly the 24-hour basal katabolism
of a number of cattle. Since they found a great difference in the heat-
production according to whether the animal was lying or standing, they
compute their basal katabolism data upon three different bases, namely,
that the animal was lying for 24 hours, standing for 12 hours and lying
for 12 hours, and standing the entire 24 hours. On the basis of 24 hours
lying, the average computed basal katabolism of their cattle was 964
calories per square meter of body-surface per 24 hours. In determining
the surface area of their cattle these investigators had the distinct advan¬
tage of using the more modern formula for surface-area measurements as
suggested by Moulton,* 6 but they had to determine the basal katabolism by
the method of computation. This value of 964 calories they compare with
the value of 935 calories found with men, 886 calories found with women
in complete muscular repose, 1,078 calories with hogs, lying, and 948
calories with a horse, standing quietly. In their opinion this comparison
confirms the conclusions of E. Voit.°
CORRECTION OF BASAL KATABOLISM TO A STANDARD DAY AS TO STANDING AND LYING
The Pennsylvania investigators computed that the basal katabolism of
their cattle per square meter of body-surface, when the cattle were standing
for the entire 24 hours, was 1,365 calories or 401 calories greater than when
the animal was lying 24 hours. The increment due to the standing position
is thus 41 per cent. It is perhaps unfortunate at this time to discuss the
results of the Pennsylvania Institute of Animal Nutrition since Dr.
Armsby’s death, for evidently an extensive revision of calculations and
factors is now being made. If the discussion is confined, however, entirely
to their own published data, one is justified in pointing out several signifi¬
cant facts. In the first place, the difference of approximately 41 per cent
between the metabolism in the lying and standing positions is, in accord¬
ance with the latest published and corrected computations from the Penn¬
sylvania institute, very large, for the more recent figures of Fries and
Kriss'1 would imply a difference of approximately 9 per cent. The standards
° Armsby, Fries, and Braman, Journ. Agric. Research, 1918, 13, p. 43.
6 Moulton, Journ. Biol. Chem., 1916, 24, p. 299.
* E. Voit, Zeitschr. f. Biol., 1901, 41, p. 113.
Fries and Kriss, Am. Journ. Physiol., 1924, 71, p. 60.
212
METABOLISM OF THE FASTING STEER
of Fries and Kriss are derived from a series of experiments with one espe¬
cially satisfactory animal, cow 874, which gave off 4.9162 calories per
minute while standing and 4.4771 calories per minute while lying. The
difference is 0.4391 calorie, which represents a decrease in the heat-produc¬
tion with a change in body position from standing to lying of about 9 per
cent. Our own data regarding the difference in metabolism in the two
positions are, as already stated (see p. 202), not extensive enough to permit
of drawing definite conclusions, but on the basis of our results it seems
highly probable that the correction factor might in general be nearer 20
than 9 per cent, with a probable influence of the length of time since feed
was withheld.
Since this percentage correction plays an important role in the computa¬
tion of the basal katabolism of cattle, when the computation is made on
the basis of 24 hours lying, 12 hours standing and 12 hours lying, or 24
hours standing, it can be seen that the earlier reported values for the basal
metabolism are immediately open to criticism. Since animals for the most
part stand approximately 12 out of the 24 hours, the correction to 24 hours
lying upon the old basis (41 per cent) is obviously too large, possibly 30
per cent too large on the basis of the 9 per cent difference indicated by the
recent data of Fries and Kriss.
M0llgaarda has based a recent report on the metabolism of cattle in
large part upon the method of calculation devised by Professor Armsby,
but he does not make the correction for difference in body position. At
the time of closing our report on undernutrition it was stated that we had
only just received the report of M0llgaard with regard to the respiration
experiments in his laboratory in Copenhagen. This report is, unfortunately,
printed in Danish, although some of the table headings are in English and
there is a short summary in English. We have therefore been considerably
handicapped in analyzing his data, and it is more than likely that points
raised in the following discussion may have been adequately cared for by
Professor Mpllgaard, whose keenness not only in scientific research but
in the presentation of his results is well known by all who have come in
contact with him. The experiments were made with the respiration cham¬
ber at Copenhagen. In this report we find no statement as to the environ¬
mental temperature, but in an English summary of his work* * * 6 is the state¬
ment that all of his respiration experiments were made at an environmental
temperature of 18° C. and as nearly as possible the same temperature was
maintained in the stable (17.5° to 18.5° C.). M0llgaard’s results do not
confirm Armsby’s conclusion that the metabolizable energy of a single
feedstuff has a reasonably constant value. M0llgaard's treatment of the
question of the influence of lying and standing is, however, of especial
interest, although we have to differ strongly with one of his points of view
in this respect. He concludes, from an examination of his metabolism
“ M0llgaard, Om Naeringsvaerdien af Roer og Byg til Fedning og om Naeringsatofforholdets
Betydnmg for Fodermidlernea Naeringavaerdi. Beretning 111, Fors0gslaboratoriet. Copen¬
hagen, 1923, 159 pp.
6 M0llgaard, New viewa regarding the acientific feeding of dairy-cattle. Compt. Rend. d. Tra-
vaux d. Congrfea Internat. pour l’filevage d. l’Eap&ce Bovine (The Hague) : Internat. Cong.
Rundveeteelt, 1923, p. 272.
THE BASAL METABOLISM OF STEERS
213
measurements and the relative times that the animals are standing and
that the metabolism in the standing position is not independent
quantitatively of that in the lying position, the increase in metabolism
when the animal is standing being compensated by a corresponding decrease
when it is lying down. “When the time of standing and the metabolism
is computed for 24 hours, there is absolutely no correlation of long-time
standing to high values of heat-production in respiration experiments on
constant feed.” As a result of these experiments, M0llgaard decides not to
correct the metabolism to a uniform day of standing and lying.
Since the average stall experiments indicate that animals spend not far
from 12 hours standing and 12 hours lying (although rather large differ¬
ences are occasionally observed), the importance of this correction is not
so great when the value of different feeds are being compared as it is
perhaps in the theoretical discussion concerning the true fasting katabolism
of animals, especially when this corrected value is to be compared with
the measured basal metabolism of other warm-blooded animals, particu¬
larly man. The value of 26.34 calories per hour suggested by Fries and
Kriss as the increase due to standing in the case of a 400-kg. cow, or the
computed difference of 9 per cent, has the disadvantage of being deter¬
mined upon only one animal. Another difficulty in attempting to correct
for the difference in body position is the fact that the influence of the effort
of getting up or lying down is frequently included in the comparative
measurements. Obviously in determining the rate of metabolism in most
of the practical problems, such effort is a legitimate part of the day’s
activity, although it should not be included in computing the basal
katabolism.
INHERENT ERROR IN METHOD OF COMPUTING THE FASTING KATABOLISM FROM EXPERIMENTS
ON TWO DIFFERENT FEED-LEVELS
In our study of undernutrition in steers, we found at no time values for
the heat-production per square meter of body-surface as low as the 964
calories reported by Armsby, although the metabolic level was greatly
lowered as a result of the submaintenance regime. Our measurements were,
to be sure, always made with the steer in the standing position, and if the
correction of 9 per cent were applied, our values for the measured heat-
production per square meter of body-surface would be lowered by 9 per
cent, to bring them presumably to the lying basis. With our submainte¬
nance groups of steers, with which the lowest values were found between
February 11 and May 2, the average heat-production per square meter of
body-surface was not far from 1,460 calories in the submaintenance period.®
If this value were reduced by 9 per cent to approximate the lying condition,
the metabolism would be about 1,330 calories per square meter, even during
this prolonged period of undernutrition. Indeed, if a 20 per cent correction
is applied, the value remains about 1,200 calories. In the fasting experi¬
ments here reported it was found that the heat-production per square meter
of body-surface, measured always in the standing position, ranged, for the
° Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, fig. 40, p. 292.
214
METABOLISM OF THE FASTING STEER
most part, around 1,700 calories on the day beginning from 42 to 56 hours
after the last food, except in the case of undemutrition. But even with
undernutrition a value of 1,600 or 1,700 calories was found with steers E
and F. If these values were to be lowered by approximately 9 per cent,
to bring them to the lying basis, they would still be around 1,450 to 1,550
calories, agreeing more closely with the value of 1,330 calories computed
for the submaintenance experiments.
Additional evidence regarding the probable basal metabolism of steers
is available in the experiments made between 50 and 53 hours after feeding
with several of -the steers used in our earlier submaintenance study.0 The
heat-production per square meter of body-surface per 24 hours has been
computed in these instances from the carbon-dioxide production, an
assumed respiratory quotient of 0.76, and a body-surface calculated from
the formula S — W% X 0.1081 (see Fig. 8, p. 155). Application of the 9 per
cent correction, to reduce the values to the basis of 24 hours lying, results
in values ranging from 1,170 to 1,970, averaging about 1,550 calories.
It seems improbable that the metabolism of the steer 42 to 56 hours after
food should not be approximating the basal condition. But even after the
most prolonged fasting of 14 days the heat-production was about 1,400
calories per square meter of body-surface. If it were permissible to reduce
this by 9 per cent to bring it to a basis of 24 hours lying, the heat-produc¬
tion would still be 1,270 calories at the end of this long period of fasting.
Our evidence, therefore, points strongly to the fact that the basal katab-
olism of cattle is about 1,300 calories per square meter of body-surface
per 24 hours, when the animal is lying the entire time.
In a recent article, Cochrane, Fries, and Braman6 discuss the maintenance
requirements of dry cows and use the method of computing the fasting
katabolism by comparison of the effects produced by different amounts of
the same feed. Computing the experiments on the basis of 12 hours stand¬
ing and 12 hours lying, they present values for the fasting katabolism of
3 of their cows. If the surface areas of these cows are computed from
their live weights by means of the curve in Fig. 8 (see p. 155) and if the
reported values for the fasting katabolism are divided by the surface areas,
the 24-hour heat-production per square meter of body-surface is found to
be 857, 824, and 827 calories, or, on the average, 836 calories in the case
of cow 886, 1,123 calories in the case of cow 874, and 1,079 calories in the
case of cow 887. The authors have commented upon the differences between
the values for the fasting katabolism, stating that cow 886 was extremely
quiet, spending more than half of the experimental time in the lying posi¬
tion, that cow 874 spent about half her time lying quietly, but when stand¬
ing Was much more restless, and that cow 887 stood the greater part of the
time and was more or less restless, even when lying. These experiments
were computed on the basis of 12 hours standing and 12 hours lying. If the
values were to be corrected to the basis of 24 hours lying, in order to com¬
pare them with the basal metabolism of man, they would all be reduced by
° Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, Table 55, p. 210.
5 Cochrane, Fries, and Braman, Journ. Agric. Research, 1925, 31, Table XXII, p. 1078.
THE BASAL METABOLISM OF STEERS
215
approximately 4.5 per cent. The average heat-production would then be
798 calories for cow 886, 1,073 for cow 874, and 1,030 calories for cow 887.
These values are much more in accord with those computed by Armsby,
Fries, and Braman in 1918. As a matter of fact, the average heat-produc¬
tion of cows 886, 874, and 887 would be 967 as compared with the average
value for their group of animals of 964 calories.
These values are so at variance with our own findings, both in our earlier
study of undernutrition and in this present study of fasting, as to suggest
that a serious error inherent in the method of computing the fasting
katabolism accounts for their low results. An analysis of the values for
the actually observed heat-production of these same cows, 886, 874, and
887, published by Braman® in 1924, one year previous to the publication of
the values for the computed fasting katabolism by Cochrane, Fries, and
Braman, strengthens us in our conviction that the method of computing
the fasting katabolism is in all likelihood at fault.
The minimum 24-hour heat-production of these cows, as measured in
the calorimeter, was 6,061 calories. This value was found on the eighth
and ninth days of fasting with one of the animals. Usually the heat-
production during fasting was more nearly 6,500 calories, being somewhat
lower on the second day than on the first day of fasting. On the fifth and
sixth days in the case of cow 885 the total heat-production was 6,557
calories, or essentially the same as her metabolism earlier in the fast.
On the eighth and ninth days of fasting with two other animals, 6,061
and 6,302 calories are recorded. Information is not given as to the number
of hours spent by the animals in standing and lying. Our own findings
indicate, however, that, when fasting, animals are wont to spend more
time in the lying than in the standing position. Thus, in the 4-day experi¬
ments with steers E and F (see Table 53, p. 195), on only one of the fasting
days did the animal stand more than 12 hours, that is, on February 4-5,
steer E stood for 17 hours and lay down for 7 hours. In our series of 3-day
experiments (Table 52, p. 186) longer periods of standing were more fre¬
quently observed. For purposes of discussion, however, if one assumes
that these heat values, as recorded by Braman, represent the metabolism
during a day of 12 hours standing and 12 hours lying, they could be brought
to the basis of 24 hours lying by being reduced approximately 4.5 per cent,
granting that the difference between the metabolism during 24 hours lying
and 24 hours standing is 9 per cent, as derived from the data of Fries and
Kriss. On the other hand, if one assumes that the animals were standing
the entire time, which is highly improbable, the reduction could be as
high as 9 per cent. On this last assumption, and assuming an average
fasting katabolism of 6,500 calories for cows 886 and 874, the corrected
fasting katabolism would be approximately 6,000 calories. Since cows 886
and 874 weighed approximately 400 kg., their surface area would be not
far from 4.7 square meters, according to the curve in Fig. 8 (p. 155). Their
24-hour heat-production per square meter of body-surface would therefore
be approximately 1,280 calories, on the basis of 24 hours lying. The com-
° Braman, Journ. Biol. Chem., 1924, 60, Table I, p. 82.
216
METABOLISM OF THE FASTING STEER
putation for the smaller cow 887, which weighed about 320 kg. and had
an observed total metabolism of 6,061 calories, would give about 1,350
calories per square meter of body-surface per 24 hours.
This analysis leads us to believe that the true basal or fasting katabolism
of these three cows is much more nearly 1,300 calories per square meter
of body-surface than 967 calories, the average value derived from the
fasting katabolism as computed from two feed-levels. Indeed, this average
value of 1,300 calories is about 35 per cent higher than the computed
fasting katabolism of these animals. Singularly enough, the article pub¬
lished by Cochrane, Fries, and Braman in 1925 gives no reference whatso¬
ever to the fasting values reported by Braman in 1924, although we are
inclined to think that this may possibly be due to a recognition of a necessity
for some further revision. Our own experience with the effect of different
feed-levels on fasting metabolism warrants the assertion that the fasting
katabolism of cattle per square meter of body-surface per 24 hours is
approximately 1,300 calories, save during prolonged fasting or fasting
following extreme undernutrition. If the basal katabolism of cattle in
the lying position is found to be as high as 1,300 calories, the comparison
of this value with that commonly assumed for man and woman can be
made only in full recognition of the fact that the cattle show a value
approximately 35 or 40 per cent above that for humans, and this is entirely
at variance with the hypothesis of E. Yoit and his followers.
The fact that the computation of the fasting katabolism from experi¬
ments with two different quantities of the same feed gives results far lower
than those noted when actual measurements are made of the fasting
katabolism is due, we believe, to an inherent error in the experimental
procedure. After the steer has been on submaintenance rations for some
time, his metabolism would not represent strictly the metabolic effect of
the submaintenance ration, since, as has already been stated, the metabo- .
lism at this point would also be profoundly lowered by the undernourished
condition. The computation of the fasting katabolism from the metabolism
at maintenance and submaintenance levels, therefore, gives results too low
when the submaintenance metabolism is measured after the animal has
begun to draw materially on its own body-tissue for support In our own
experiments, for example, the submaintenance ration was given for three
or more weeks prior to the measurement of its effect. This procedure at
the time was thought necessary on the conventional basis that the animal
should be adjusted to the food-level and thus have a metabolism propor¬
tional to the food intake. The measurement therefore did not represent
the effect of the reduced feed intake with the consequently lessened diges¬
tive activity and also the consequent decrease in intestinal fermentation,
because the metabolism at this stage was materially altered by under-
nutrition, i. e., by drafts upon the body organism.0 When feed is cut from
° It has been definitely shown (Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324,
1923) that when the animal is forced to draw on his own body-tissue for support, the metabolism
is depressed to an abnormally low level, since the animal parts with his own body-tissue, even for
purposes of self-preservation, only with the limit of economy, all body activities being curtailed
to save tissue.
THE BASAL METABOLISM OF STEERS
217
maintenance to submaintenance there must be some point during the transi¬
tional stage of metabolism representing the basal condition before it is
affected by undernutrition. From the previous discussion of the metabolic
plateaus it would seem that this point could best be approximated during
the second 24-hour period after feed reduction, an additional day being
possibly added as a check. In other words, a 5-day respiration experiment,
in which the first two days should represent maintenance, the third would
represent a mixed effect, and the fourth and fifth days would represent
the beginning of the submaintenance plateau (i. e., the level of metabolism
as determined by the submaintenance ration before the effect of under-
nutrition has markedly manifested itself) , appears to form the most logical
method of procedure.
Whether the same difficulty would be found if the initial feed-level were
above maintenance and the lower feed-level were at maintenance is still
open for investigation, as our experiments were not made with this point
in view. Since most studies in this field have been made upon the basis of
maintenance versus submaintenance, it would seem that this explanation
of the difference between the computed fasting katabolism and that actually
existing with the animals may serve a helpful purpose.
From the data in the series of 4-day experiments with steers E and F,
a study of a number of important problems outside of the field of fasting
metabolism becomes incidentally available, such as the relative effect of
reduction in food consisting of timothy or alfalfa hay. Thus, in the case
of steer E, there apparently was a reduction in the total heat-production
of about 3,500 calories as a result of reducing the ration from 7.00 kg. to
3.5 kg. of timothy hay. On the other hand, a reduction in the same amount
of alfalfa hay resulted in a total daily reduction of 3,800 calories. With
steer F, similar reductions resulted in a decrease of about 2,900 calories
from timothy hay and 3,400 calories from alfalfa hay.
To make such a series of experiments complete, obviously a careful
analysis of the digestibility of the hay and a determination of the nitrogen
balance should be made. On the other hand, the extra precautions taken
to secure uniformity of content of digestive tract during submaintenance
feeding (in those experiments where the effect of curtailment of ration was
compared with the effect of a full ration) by the conventional method of
preparing the animal with a preliminary feeding-period of two or more
weeks, undoubtedly resulted in a change in the nutritive level of the animal.
This has been established by the comparative results of the various fasts.
It would seem, therefore, as if the question of digestibility on lower rations
should be studied independently and not combined with a study of the
gaseous exchange. It is our purpose to discuss such data from these experi¬
ments as lend themselves to a study of these different angles later, as more
information is secured not only upon steers but upon dry cows, with which
we are at present carrying out observations. The data presented here are
therefore primarily such as bear directly on the effect of the character and
quantity of the previous feed-level and the effect of environmental tempera¬
ture upon the fasting katabolism.
218
METABOLISM OF THE FASTING STEER
This discussion is of chief significance solely from the standpoint of
comparative physiology. From the practical standpoint it may be assumed
that in general a sufficiently close approximation of the fasting katabolism
can be determined on animals, while standing, about 32 hours after the last
food, and that if a satisfactory reduction in the measurement thus obtained
is made for lying, the basal metabolism during 24 hours lying may be
computed. This procedure should give a value which is suitable as a base¬
line in studies of the superimposed effects of various factors, provided the
experiments are made shortly after this basal determination. The value
will not be uniform with different animals, even if the metabolism is com¬
puted on the basis of surface area. It will not be uniform for the same
animal at different times, particularly when there are profound, changes
in the nutritive state, for even with essentially the same nutritive state
considerable differences do occur, as is seen in Table 48 (p. 173).
In consideration of the great difference between the fasting katabolism
computed on the basis of the metabolism at two different feed-levels and
that actually found by calorimetric and gaseous metabolism measurements
during prolonged fasting, it would seem as if the computation method, at
least in its present form, has limited value.
The Minimum Heat-production of Steers per Square Meter of Body-surface per 24
Hours
In the discussion of the plateau level in the metabolism of these fasting
steers it was pointed out (see pp. 213 to 216) that the lowest level during
fasting was about 1,300 calories per square meter of body-surface per 24
hours, i. e., higher than the conventional 1,000 calories ascribed to all warm¬
blooded animals as a class. An examination of all our values indicating
the minimum heat-production per square meter of body-surface which may
be expected with steers under numerous different conditions, irrespective
of whether a plateau has been reached in the metabolism, becomes of
interest for purposes of comparison with other researches made on this
basis.
The lowest values for the 24-hour heat-production per square meter of
body-surface occur in the series of experiments involving three or four
half-hour periods of measurement. With steer C the lowest value is 1,060
calories on January 30, 1923, 49 hours after food. With steer D the lowest
value is 1,190 calories, also the same number of hours after food and at
about the same date, i. e., January 27, 1923. (See Tables 44 and 45, pp. 166
and 168.) In both of these instances the steers were at a maintenance
level of nutrition. With steer C another low value of 1,100 calories was
found on the second day of the fast in March 1924, following submainte¬
nance feeding. With steer F, a younger animal, the lowest recorded value
is 1,540 calories, 24 hours after the last food on February 19, 1924, which
happened to be the first day after a fasting experiment. With steer E it
was 1,520 calories on December 28, 1923, when the animal was upon a
submaintenance level. (See Table 57, p. 232.)
In the continuous 3-day experiments in 1924, the heat values are based
not upon three or four half-hour periods, but upon individual 8-hour
THE BASAL METABOLISM OF STEERS
219
periods. In this series the minimum heat-production of steer C was 1,580
calories on April 25, that of steer D was 1,820 calories on May 15, that
of steer E was 1,890 calories on April 11, and that of steer F was 1,850
calories on April 1. (See Table 52, p. 186.) These measurements were
all made while the animals were fasting, but immediately following mainte¬
nance rations. In the 4-day experiments in 1925, when the metabolism
was also measured in 8-hour periods, lower values were found with the
younger animals. Thus, steer E had a minimum 24-hour heat-production
of 1,230 calories per square meter of body-surface in the 8-hour period
beginning 32 hours after food on May 6-7, 1925, and steer F of 1,330
calories in the 8-hour period beginning 56 hours after food on May 14-15,
1925. In both instances the steers were fasting after a submaintenance
level of nutrition.
The lowest values found with steers C and D were, therefore, 1,060 and
1,190 calories, and with steers E and F 1,230 and 1,330 calories, respectively.
A careful examination of the conditions under which these very low
values for steers C and D were obtained brings out the fact that the
metabolism of both animals had been measured at a very low temperature
on one day and at a much higher temperature on the following day. Thus,
with steer C on January 29, 1923, at a chamber temperature of 2.9° C.,
the heat-production was 1,740 calories per square meter of body-surface.
On the next day the temperature of the chamber was raised to 24.9° C.
and the metabolism per square meter of body-surface fell to 1,060 calories.
With steer D the situation was similar, in that on January 26 the chamber
temperature was 8.8° C. and the heat-production 1,850 calories, and on
the next day the temperature was raised to 28.3° C. and the metabolism
fell to 1,190 calories. In each case the second experiment at the high
temperature was made 24 hours later than the first experiment, that is,
49 hours after food. As such large decreases in metabolism were not
obtained with these steers during the first three days of fasting after full
feeding in the series of long fasts, it is evident that these abnormally low
values are the result of the pronounced effect of the sudden transition from
a cold to a warm environment.0 This conclusion is supported by another
experiment with steer D on January 18 and 19, 1923. On the first day
the chamber temperature was 3.4° C. and the metabolism was 1,730
calories per square meter of body-surface. On the next day the temperature
in the chamber was raised to 28.2° C. and the metabolism fell to 1,290
calories. An examination of all our data shows that in practically every
instance a striking rise in temperature resulted in a greatly lowered
metabolism. When the temperature was 12° C. or above, however, the
change in metabolism was no greater than would be expected on one or
two successive fasting days.
This profound decrease in the metabolism of steers C and D, although
apparently due to a sudden change of temperature, is difficult of further
a A similar explanation does undoubtedly account for the low standard metabolism of 1,180
calories per square meter of body-surface per 24 hours noted with steer C on December 20, 1923,
when on a maintenance ration. In this instance the steer had been for approximately 24 hours
at a stall temperature of 3° C. and was then studied in the respiration chamber at a temperature
of 19.5° C. (See Table 55, p. 226.)
220
METABOLISM OF THE FASTING STEER
explanation without other data on this point. The metabolism during the
first day of fasting on the cold days, which was not far from 1,700 calories
per square meter of body-surface, is not so high with these animals as,
for example, on the first day of the long fasting experiments (see Table
50) , and it is not indicative of an especially high metabolism produced by
severe cold. The transition from the cold to the warm environment evi¬
dently had an immediate pronounced effect in lowering the metabolism,
perhaps to be explained by the fact that prior to each metabolism measure¬
ment the animals had been in their metabolism stalls for only about 16
hours at a temperature essentially the same as that which prevailed in the
respiration chamber during the experiment.
There are only a few instances where the conditions were reversed and
the metabolism was measured at a high environmental temperature on the
first day of fasting and at a low temperature on the second day. The most
striking illustration is the experiment with steer D on February 2 and 3,
1923. On February 2 the chamber temperature was 27.9° C. and the heat-
production was 1,610 calories per square meter of body-surface. The
records of stall temperature show that from 8 p. m. on February 2 until
the time of the respiration experiment on February 3 the environmental
temperature was essentially 12° C. On February 3 the chamber tempera¬
ture was 7.3° C. and the heat-production was 1,450 calories. In this
instance the drop in metabolism was hardly more than would be expected
with continued fasting, and the change in temperature apparently had no
influence upon the metabolism. Because of these sudden changes in metab¬
olism following a change in temperature, our plan of experimentation
in studying the influence of environmental temperature was altered in the
1925 series in that the animals were kept for two weeks or more prior to
an experiment at the specific temperature at which they were to be studied
in the respiration chamber.
With humans there is almost no evidence to explain this pronounced
lowering in metabolism with the change from a very cold to a warm envi¬
ronment. The Nutrition Laboratory has for many years been searching,
without success, for some factor or combination of conditions that would
result in a lowering of the so-called “basal metabolism” of humans. Pro¬
found undernutrition and fasting do lower it, but these are not immediate,
superimposed factors. It has been maintained that a warm bath lowers
the metabolism, and that the basal metabolism can only be secured when
the body is immersed in water at about 35° C.° This problem was studied
at the Nutrition Laboratory with several subjects, and it was noted that
the metabolism was not lowered by immersion in the bath.* 6 More recently
Delcourt-Bernard and Andre Mayer have reported0 that they have occa¬
sionally noted a very low metabolism with humans after prolonged immer¬
sion in a warm bath, indicating an after-effect of the bath. It is possible
that with these steers in the somewhat rapid transition from the cold to
“ Lefevre, Bull. Soc. Sci. d’Hygiene Alimen., 1922, 10, p. 595.
6 Benedict and Benedict, Bull. Soc. Sci. d’Hygifene Alimen., 1924, 12, p. 541; ibid., Proc.
Nat. Acad. Sci., 1924, 10, p. 495.
c Delcourt-Bernard and Mayer, Compt. Rend., 1925, 92, p. 62.
THE BASAL METABOLISM OF STEERS
221
the warm environment there may be a period of relaxation or adjustment
to the temperature, which may actually result temporarily in a lower
heat-production. It is unfortunate that the tests of this after-effect of
the warm environmental temperature were not prolonged sufficiently to
note whether this low metabolism remained constant or whether there was
a later reaction. This problem should be studied in the near future.
Of great importance to general physiology, however, is the fact that, at
least with steers C and D, there are two instances of a heat-production
per square meter of body-surface actually approaching 1,000 calories, the
value commonly assumed to represent the heat-production of all warm¬
blooded animals. The fact that these values were found only under the
special condition of an extreme change in temperature implies that we
have to deal here not with a persistent level of basal metabolism but with
a special, imposed condition, the effect of which, in all probability, is
transitory. When steer C was subjected to submaintenance rations and
then to prolonged fasting, the heat-production per square meter of body-
surface was, to be sure, as low as 1,110 calories. But since this value
reflects the influence of the superimposed effect of undernutrition, it can
hardly be compared directly with values found with animals at a mainte¬
nance level of nutrition, even after they have undergone several days of
fasting. Fasting per se, provided the initial level of nutrition has not been
too greatly lowered by a submaintenance ration, results in a heat-produc¬
tion per square meter of body-surface per 24 hours much nearer 1,700
calories during the first 48 hours than the 1,060 and 1,190 calories noted
with these two animals following the extreme change in temperature.
THE PHYSIOLOGICAL SIGNIFICANCE OF SURFACE AREA AND ITS RELATIONSHIP TO
HEAT-PRODUCTION
For the comparison of the true basal metabolism of these steers with
that of man, determined under the well-known prescribed conditions of
the post- absorptive state and complete muscular repose, measurements
made during periods of quiet lying, at least 48 hours after the last food,
are presumably the best. Since all of our heat values were determined
when the steers were standing or both lying and standing, they probably
should be corrected for the extra effort of standing (see p. 211), if they are
to represent conditions similar to those under which the basal metabolism
of humans is measured. We have already seen (p. 214) that the average
heat-production per square meter of body-surface of these steers 42 to 56
hours after food, which would correspond essentially to the 12-hour interval
required with man, would be about 1,700 calories at the maintenance level
and from 1,600 to 1,700 calories at the submaintenance level. If these
values were corrected for the extra effort of standing, they would still
be materially above 1,300 calories on the average.
This value of 1,300 calories per square meter of body-surface may there¬
fore be taken as the probable basal metabolism or the lowest metabolism
of these ruminants, which will remain reasonably constant for four or five
days of fasting, after which the metabolism will fall off, as indicated in
Table 50. The popular impression that the metabolism is 1,000 calories
222
METABOLISM OF THE FASTING STEER
per square meter of body-surface for all warm-blooded animals must, we
believe, be looked upon with great reserve in a refinement such as this.
The basal metabolism of man has been found with considerable exactness
to be, on the average, not far from 900 calories per square meter of body-
surface. With these steers, however, the basal values are not far from
1,300 calories, or approximately 45 per cent higher.
The rectal temperatures of these steers were about 1 degree higher than
the rectal temperature of the average man (37° C.). Physiologists, how¬
ever, in considering this law of surface area and the heat-production per
square meter of body-surface, are inclined to disregard differences in body
temperature between species, although admitting that in the individual
human small rises in temperature actually result in greater heat-production.
Emphasis has been laid upon the matter of equal conditions of nutrition in
comparing various animals. We have seen in our study of steers that the
heat-production is lower at the submaintenance level than at the mainte¬
nance level, and that during fasting it is somewhat lower than at the
submaintenance level. One of the most extensive uses to which the meas¬
ured heat-production of man and the standard values are put, however, is
the clinical application to pathological cases, in which undemutrition plays
a large role. We have yet to see indications where differences in the nutri¬
tive states of humans have been seriously taken into consideration in
assessing the measured heat metabolism and comparing it with normal
standards.
The problem of establishing a basal heat-production with ruminants,
which may be used for the comparison of the influence of the ingestion
of various types of food and the influence of various levels of feeding, is
by no means solved. Uniformity may not be hoped for with different
animals. Differences with different feed-levels will undoubtedly be found.
Differences with different environmental temperatures have already been
noted, especially on the lower feed-levels. It is believed that a study of
the reaction of an animal in a given nutritive state to the drafts upon
body material, as exemplified by these short 2-day fasting experiments,
and a study of the effect of various rations in enabling the animal to
withstand such drafts upon body material when equal states of nutrition
are assumed, may be of great value in estimating not only the nutritive
states of an animal, but the actual value of various feeds to the animal for
growth, maintenance, and protection against drafts upon body material.
Influence of the Ingestion of Food
The Immediate Reaction to the Ingestion of Food After a Prolonged Fast
In view of the difficulties experienced with humans during realimentation
after a long fast or after a long period of undemutrition,® it was considered
important to note the metabolic reaction of these steers to the ingestion
of food after prolonged fasting. A number of respiration experiments were
therefore made at the end of some of the long fasts, and the effect of the
first feed following the fast was studied in continuous half-hour periods
° Benedict, Carnegie Inst. Wash. Pub. No. 203, 1915, p. 49; Benedict, Miles, Roth- and Smith
Carnegie Inst. Wash. Pub. No. 280, 1919, p. 683.
INFLUENCE OF THE INGESTION OF FOOD
223
for from five to eight hours following the ingestion of feed, while the animal
remained inside the respiration chamber. Information was thus obtained
on the change in the respiratory quotient resulting from ingestion of food,
and particularly on the change produced in the actual metabolism, as
indicated by the carbon-dioxide excretion. From 1 to 2 kg. of chopped
hay were usually offered to the steers, and in some cases a small amount
of meal, not far from 1 kg.
In general, the animals were extremely slow about eating- When hay
alone was offered they would take an hour or more to consume even a
moderate amount, such as 1,000 to 2,000 grams. The grain, being more
palatable, was apparently relished more and eaten with greater vigor. It
would seem as if there was an instinctive control which retarded the steer
from overeating. It was believed at first that a study of the immediate
effect of feeding could be superimposed at the end of a fasting experiment,
but the small amounts of hay consumed made such experiments unsatis¬
factory and almost without significance.
A comparison of the carbon-dioxide production on the last day of the
fast with the carbon-dioxide production measured in the different half-hour
periods of the respiration experiment made almost immediately after the
animal had been fed, shows that during the first half-hour period there
was invariably a striking increase in the metabolism. In the subsequent
periods the carbon-dioxide production was irregular, with no clear indica¬
tion of a continual increase during the 5 to 8 hours under investigation.
There was always a pronounced rise in the respiratory quotient, which
slowly though continually increased. The general conclusion is that there
is an immediate response to the ingestion of food, probably depending
somewhat upon the length of time that the animals were occupied in eating
the relatively small amounts consumed. After the initial response, these
small amounts of feed did not further stimulate the metabolism.
The Metabolic Stimulus of Feeding-stuffs
The metabolism of the organism is stimulated or raised above the basal
requirements by the processes of digestion and utilization of food much as
the fire in a furnace would flare up when fanned by a blower. The separate
evaluation of the economic cost of such overhead processes with each feed¬
ing-stuff is the critical feature in the determination of the so-called “net
energy values” of feeding-stuffs. The attempt to determine this economic
cost by measuring the metabolism at two different feed-levels has, we
believe, resulted in the utilization of an unduly low figure for the metabolism
following the lower food-level. This experimental plan calls for prolonged
feeding on the curtailed ration prior to the measurement of the metabolism,
in order to secure uniformity of contents in the intestinal tract and hence
uniformity in the determination of the digestion coefficients. By this
procedure the animal is brought to a lower metabolic plane by the dual
effect of the actual reduction in feed and the condition of undernutrition
at least begun during the 3 weeks’ period of submaintenance feeding. On
the other hand, if the metabolism of an animal is first determined while
he is on maintenance feed and then shortly thereafter at essentially the
fasting stage, the difference between these two levels should indicate the
224
METABOLISM OF THE FASTING STEER
increased metabolism of the organism due to the ingestion of food. This
method is certainly justifiable when animals are fed a maintenance ration.
In order to compare the metabolism on maintenance and submaintenance
rations, or on a ration 50 per cent below maintenance, as was the case in
our research, in all probability the curtailment should not take place more
than at the most one or two days before the actual experiment, as otherwise
one will be running into the dangers of incipient undernutrition with its
well-known depressing effect upon metabolism.
Experiments on this special point have not yet been made, although they
are in our experimental plan. If we examine the data for the 4-day
experiments with steers E and F (see Table 53, p. 195) and confine our¬
selves to those experiments in which maintenance feeding with 7 kg. of
either timothy or alfalfa hay is involved, and eliminate any experiments
with unduly low chamber temperatures, we may obtain some evidence
regarding the increase in metabolism due to the feed. It will be recalled
that in these experiments the animal was fed 7 kg. of hay for at least two
weeks prior to the experiment.
The 24-hour heat-production of steer E during maintenance feeding on
timothy hay was reasonably constant at 11.6 therms0 on December 12 to
14. In the experiment beginning 32 hours after the withholding of this
ration, i. e., during the stage of so-called “fasting katabolism,” the heat-
production was 7.7 therms or 3.9 therms lower. Reversing the argument,
one can state that a fasting katabolism of 7.7 therms was raised 3.9 therms
by the regular ingestion of 7 kg. of timothy hay. In other words, there
was an increase in metabolism of 51 per cent. Similarly, in the experiment
from February 27 to March 3* * 6 the initial metabolism with 7 kg. of timothy
hay was 11.1 therms. In the basal experiment beginning 32 hours after
the last food it was 7.8 therms, or 3.3 therms lower. There was, therefore,
in this case an increase of 42 per cent with the ingestion of 7 kg. of timothy
hay. With alfalfa hay the heat-production in the March experiment was
11.5 therms during the two days on feed and 7.0 therms in the period
beginning 32 hours after the last food. The increase due to the hay was
therefore 4.5 therms or 64 per cent. The experiment of April 14 to 17
shows a heat-production during full feeding with alfalfa hay of 11.5 therms
and 32 hours after the last food 6.7 therms, i. e., an increase of 4.8 therms
or 72 per cent.
With steer F in the December experiment with timothy hay, the heat-
production was 11.9 therms on full feed and 32 hours after food it was
8.1 therms. The increase due to the hay was thus 3.8 therms or 47 per cent.
On March 23 to 25 the two days of feeding with alfalfa hay resulted in a
metabolism of 12.5 therms, which fell to 7.7 therms on the second day
without food. The difference was 4.8 therms or 62 per cent. In a second
experiment with alfalfa hay in April, the heat-production on full feed was
12.3 therms and 32 hours after food was 7.5 therms. The increase was 4.8
therms or 64 per cent.
° We use the Armsby term here, since in practical feeding problems it apparently has distinct
advantage over the large numeral calories. One therm is equivalent to 1,000 large calories.
6 The low environmental temperature obtaining in this experiment is seemingly without effect.
INFLUENCE OF THE INGESTION OF FOOD
225
Thus with both animals it is clear that the increase in metabolism pro¬
duced by the 7 kg. of timothy hay was not far from 50 per cent, but that
the increase produced by 7 kg. of alfalfa hay was nearer 60 per cent. On
this basis, therefore, the so-called “specific dynamic action,” or preferably
the “metabolic stimulus,” of alfalfa hay is measurably higher than that
of timothy hay. On the other hand, as has been pointed out before this,
the basal heat-production with alfalfa hay, determined 32 to 56 hours after
food, is perceptibly lower in general than with timothy hay. This may
possibly be accounted for by the fact that the alfalfa experiments were
at the end of the series with both animals. In other words, the steers had
been undergoing a fairly rapid series of 2-day fasts and undoubtedly their
nutritive condition must have been at a somewhat lower level at the end
of the series than it was at the beginning, in spite of the mild attempts
to make up for the loss between experiments. To make the study perfectly
clear, the experimental series should likewise have been carried out in the
reverse order. But, as stated frequently, our main object was not to study
the relative merits of alfalfa and timothy hay.
These feeds are both characterized, as is most roughage for animals, by
a low digestibility, that is, they are approximately 50 per cent digestible.
The alfalfa hay is richer in protein than is the timothy hay, which is
relatively protein-poor. Judging from experiments on mep and dogs, the
normal increase in metabolism due to the ingestion of food is by no means
of the same order of magnitude as observed with these ruminants. Thus,
Benedict and Carpenter® found in three 8-hour experiments, when the sub¬
ject ate enormous amounts of food at one meal (the fuel value of which
averaged 4,000 calories), that the total increment in heat noted in the
subsequent 8 hours was 186, 229, and 148 calories, respectively. On the
average the increase was 23 calories per hour. Since the heat-production
was about 70 calories per hour when these subjects were resting, it can be
seen that during these eight hours, when the digestive activity was greatest
there was an increase of only about 30 per cent in the heat-production due
to these enormously heavy meals. When referred to the actual fuel value
of the meal itself, this increase (termed by the authors the “cost of diges¬
tion”) is found to be not far from 5 per cent. The picture is entirely
different with steers, for the ingestion of 7 kg. of hay, of which one-half
* only is digestible, produced not during the height of digestion but through¬
out an entire 24-hour period an increase in the total heat-production of
50 per cent in the case of timothy hay and 60 per cent in the case of alfalfa
hay. In the case of the men the protein in the meal accounted in appre¬
ciable part for the increase, as the so-called “specific dynamic action” of
protein is most marked. Timothy hay, however, contains little protein,
and the stimulating effects of foods are on an entirely different plane with
ruminants than with a human being. These large increases, we believe,
may be easily accounted for by the nature of the cleavages which carbo¬
hydrate material undergoes in its passage through the intestinal tract.
Indeed, the early suggestion of Grouven, that carbohydrates for the large
0 Benedict and Carpenter, Carnegie Inst. Wash. Pub. No. 261, 1918, Table 249, p. 337.
226 METABOLISM OF THE FASTING STEER
Table 55— Standard metabolism of steer C at different levels of nutrition
Car-
Heat produced per
In-
Aver-
bon
24 hours
Heart-
di-
Res-
Stall
tem¬
pera¬
ture
Feed-level,
and dates
Live
weight
rate
per
min-
ble
loss
per
cham¬
ber
tern-
oxide
pro¬
duced
pira-
tory
quo-
Total
Per
Per
Ac¬
tivity
ute
24
pera-
per
tient
500 kg.
sq. m.
hours
ture
half
hour
Realimentation; 4 to 8
cal.
cal.
cal.
kg. hay, 2 kg. meal;1
kg.
kg.
°C.
°C.
gm.
ii
Dec. 17, 1921 ....
558.4
40
4.8
21
21.3
56.7
(0.82)
8,100
7,300
1,440
Dec. 22,1921....
570.0
38
2.2
7
11.3
59.9
(.82)
8,600
7,500
1,510
ii
Jan. 23, 1922. . . .
567.6
40
6.4
12
20.3
79.3
(-82)
11,400
10,000
2,000
II
Jan. 30, 1922. . . .
Maintenance; 9 kg.
572.2
40
24
21.6
81.0
(.82)
11,600
10,100
2,030
hi
hay:2
Mar. 21, 1922... .
Mar. 31, 1922....
596.0
592.2
8 60
24.9
71.6
(.82)
10,300
8,600
1,750
ii
40
7.4
20
22.7
66.4
(.82)
9,500
8,000
1,630
ii
Realimentation; 8 kg.
hay:
May 9,1922....
562.2
34
5.2
18
19.4
66.1
(.82)
9,500
8,400
1,680
ii
Maintenance; 9 kg.
hay, 2 kg. meal:2
5,600
1,200
ii
Dec. 13,1922....
674.8
40
9.0
18
22.1
51.5
.79
7,600
Dec. 18, 1922 _
670.8
40
12.8
26
27.0
69.4
.78
10,400
7,800
1,650
ii
Dec. 21,1922....
663.0
40
9.4
22
13.4
75.4
.84
10,600
8,000
1,690
ii
Dec. 26,1922....
674.2
40
11.2
26
26.6
66.3
.86
9,200
6,800
1,450
I
Dec. 29,1922....
676.2
38
6.6
15
6.4
70.2
.84
9,900
7,300
1,560
ii
Jan. 16,1923 4...
689.2
40
11.8
29
27.8
64.0
.85
8,900
6,500
1,390
hi
Maintenance; 9 kg.
hay:6
Apr. 3, 1923 _
705.6
6 32
9.6
21
23.1
67.5
.89
9,100
6,400
1,400
hi
Apr. 11,1923....
705.8
37
6.4
14
17.9
68.9
.83
9.S00
6,900
1,500
ii
Apr. 18, 1923 _
704.2
8 38
8.2
18
22.1
69.7
.73
11,000
7,800
1,690
ii
Apr. 24,1923....
700.8
•32
6.0
12
16.5
71.4
.78
10,700
7,600
1,650
i
Submaintenance; 4.5
kg. hay:7
May 5,1923....
669.0
36
7.2
22
25.5
55.7
.72
8,900
6,700
1,410
hi
May 11,1923....
664.2
38
4.4
16
20.5
65.1
.79
9,600
7,200
1,530
hi
May 18,1923....
662.2
32
5.2
18
21.5
54.8
.77
8,300
6,300
1,330
hi
May 24, 1924. . . .
655.2
32
4.4
17
23.5
56.1
.76
8,600
6,600
1,380
ii
Maintenance; 8 kg.
hay:8
June 18, 1923. . . .
642.8
•60
7.4
20
25.9
86.3
.79
12,800
10,000
2,080
hi
June 23, 1923. . . .
Maintenance; 9 kg.
649.2
•46
23
27.4
85.5
.89
11,500
8,900
1,860
ii
hay:2
Nov. 28,1923....
Dec. 6,1923....
Dec. 13,1923....
Dec. 20, 1923. . . .
Submaintenance; 4.5
(690.6)
690.6
690.6
693.2
44
10
22.3
72.8
.87
10,000
7,200
1,550
ii
40
13
20.3
76.9
.91
10,200
7,400
1,580
ii
36
ca. 9
23.2
77.3
.94
10,000
7,200
1,550
ii
38
3
19.5
57.2
.90
7,600
5,500
1,180
ii
kg. hay:2
Jan. 3, 1924. . . .
Jan. 11,1924....
Jan. 18,1924....
Jan. 24,1924....
Jan. 31,1924....
Feb. 7,1924....
(650.0)
650.4
655.0
655.4
646.4
629.2
38
36
3
14.0
60.4
.81
8,800
6,800
1,420
ii
7
10.1
51.1
.83
7,300
5,600
1,180
i
36
7
11.9
55.6
.82
8,000
6,100
1,290
i
36
1
9.0
59.1
.80
8,700
6,600
1,400
ii
38
14.5
56.4
.79
8,400
6,500
1,360
ii
34
ca. 1
9.3
52.5
.80
7,700
6,100
1,270
ii
Feb. 25,1924....
Maintenance; 7 kg.
631.4
34
13.8
53.4
.84
7,500
5,900
1,230
i
hay:10
Nov. 26, 1924...
744.6
11 44
1 .
18.8
73.0
.85
10,200
6,800
1,510
i
1
1 No meal given before experiments of Dec. 17 and Dec. 22.
2 Steer had received this feed daily for at least 2 weeks preceding the experimental series. * Steer was eating.
4 This experiment was preceded by a 3-day fast on Jan. 3 to 6.
5 The first experiment in this series was preceded by 5 days on 9 kg. hay; before that 9 kg. hay and 2 kg.
meal were given daily. • Steer was lying down.
7 The first experiment in this series was preceded by 9 days on 4.5 kg. hay; before that 9 kg. hay were given
* The first experiment in this series was preceded by 9 days on about 8 kg. hay; for 3 days before that 3
to 6 kg. hay and 1 to 2 kg. meal were given daily. • Steer had just stood up.
h The experiment of Nov. 26, 1924, was preceded by 4 days on 7 kg. hay daily; before that 8 kg. hay were
given daily and 2 to 8 kg. meal on some days. 11 Heart-rate on Nov. 25.
THE STANDARD METABOLISM OF STEERS 227
Table 56. — Standard metabolism of steer D at different levels of nutrition
Heart-
rate
per
min¬
ute
In¬
sensi¬
ble
loss
per
24
hours
Stall
tem¬
pera¬
ture
Aver¬
age
cham¬
ber
tem¬
pera¬
ture
Car¬
bon
Res-
Heat produced per
24 hours
Feed-level,
and dates
Live
weight
oxide
pro¬
duced
per
half
hour
pira-
tory
quo¬
tient
Total
Per
500 kg.
Per
sq. m.
Ac¬
tivity
Realimentation; 3 to 8
kg. hay, 2 kg. meal:1
kg.
kg.
°C.
°C.
gm.
cal.
cal.
cal.
ii
Dec. 17,1921....
584.4
40
6.8
21
22.3
59.7
(0.82)
8,600
7,400
1,490
Dec. 22,1921....
590.6
40
3.6
7
17.2
58.2
(.82)
8,400
7,100
1,440
ii
Jan. 23, 1922. . . .
590.6
3 40
6.2
12
23.6
67.3
(.82)
9,700
8,200
1,700
ii
Jan. 31,1922....
600.2
48
22
21.0
81.5
(.82)
11,700
9,700
1,990
in
Maintenance; 9 kg.
hay:3
ii
Mar. 21, 1922 _
611.2
4 56
24.9
86.3
(.82)
(.82)
12,400
10,100
2,080
Mar. 31, 1922....
612.6
40
6.8
20
22.8
73.7
10,600
8,700
1,780
ii
Realimentation; 4 to 9
kg. hay:
1,860
ii
May 9,1922....
570.8
46
5.6
18
22.4
73.9
(.82)
10,600
9,300
Maintenance; 9 kg.
hay, 2 kg. meal:3
ii
Dec. 15,1922....
675.6
44
13.0
27
26.0
69.8
.73
11,000
8,100
1,740
Dec. 19,1922....
670.8
40
11.8
23
10.5
80.2
.84
11,300
8,400
1,790
ii
Dec. 30,1922....
677.2
46
17.6
13
8.2
76.3
.82
11,000
8,100
1,730
i
Jan. 3, 1923. . . .
676.0
48
6.2
11
8.4
76.8
.82
11,000
8,100
1,730
i
Maintenance; 9 kg.
hay:8
hi
Apr. 4,1923....
697.8
8 46
6.6
18
21.8
80.7
.78
12,100
8,700
1,870
Apr. 12,1923....
699.2
3 46
7.8
14
18.9
78.3
.83
11,200
8,000
1,730
ii
Apr. 19,1923....
693.0
3 42
6.4
14
20.9
75.0
.76
11,500
8,300
1,780
ii
Apr. 25,1923....
693.0
3 36
9.0
20
23.6
77.3
.86
10,700
7,700
1,660
Submaintenance; 4.5
kg. hay:7
hi
May 4,1923....
672.0
48
5.8
21
24.2
67.1
.72
10,700
8,000
1,690
May 12,1923....
659.6
8 60
8.2
24
26.8
66.6
.74
10,400
7,900
1,660
hi
May 19,1923....
651.2
48
5.6
21
24.8
67.1
.73
10,600
8,100
1,710
hi
May 25, 1923. . . .
649.0
48
6.2
22
27.1
68.0
.73
10,700
8,200
1,730
m
June 1,1923....
640.8
40
7.2
19
23.6
66.3
.74
10,300
8,000
1,680
in
June 8, 1923. . . .
633.8
48
4.2
18
21.6
68.1
.78
10,200
8,000
1,670
ii
Maintenance; 9 kg.
hay:*
1,960
June 16, 1923. . . .
659.0
60
9.4
18
24.6
86.4
.84
12,200
9,300
I
June 22, 1923 ....
660.0
48
12.2
26
28.8
82.6
.85
11,500
8,700
1,840
hi
Maintenance; 9 kg.
hay:8
hi
Nov. 30, 1923... .
683.4
48
9
19.8
85.2
.86
11,800
8,600
1,850
Dec. 7,1923....
673.6
52
13
21.6
87.4
.91
11,600
8,600
1,830
in
Dec. 14,1923....
674.0
44
11
18.6
79.9
.89
10,800
8,000
1,700
hi
Dec. 21,1923....
686.8
44
8
18.4
79.6
.84
11,200
8,200
1,750
hi
Submaintenance; 4.5
kg. hay:8
1,580
ii
Jan. 4, 1924. . . .
653.2
36
5
10.6
67.3
.81
9,800
7,500
Jan. 12,1924....
633.6
40
9
11.0
60.6
.80
8,900
7,000
1,460
i
Jan. 19,1924....
Jan. 25,1924....
639.6
644.2
44
4
10.7
69.3
.82
10,000
7,800
1,630
i
48
5
10.1
61.9
.78
9,300
7,200
1,510
i
Feb. 1,1924....
627.4
42
5
6.3
65.8
.79
9,700
7,700
1,600
ii
Feb. 8,1924....
620.6
56
-6
8.9
57.6
.79
8,500
6,800
1,410
ii
Feb. 26,1924....
Maintenance; 7 kg.
614.6
42
-2
11.1
64.8
.78
9,700
7,900
1,620
i
hay:10
1,830
Nov. 26, 1924... .
715.2
11 52
17.5
81.6
.80
12,000
8,400
i
1 No meal given before experiment of Dec. 17 and Dec. 22. 1 Steer was lying down.
* Steer had received this feed daily for at least 2 weeks preceding the experimental series. 4 Steer was eating.
* The first experiment in this series was preceded by 6 days on 9 kg. hay; before that 9 kg. hay and 2 kg.
meal were given daily. 8 Steer was ruminating.
1 The first experiment in this series was preceded by 8 days on 4.5 kg. hay ; before that 9 kg. hay were given
daily. 8 Steer had just stood up.
* The first experiment in this series was preceded by 7 days on 9 kg. hay; before that 4.5 kg. hay were
given daily .
10 The experiment of Nov. 26, 1924, was preceded by 4 days on 7 kg. hay; before that 8 kg. hay were given
daily and 2 to 8 kg. meal on some days. 11 Heart-rate on Nov. 25.
228
METABOLISM OF THE FASTING STEER
part pass through the fatty-acid stage of fermentation, would fall in line
with the theory that the stimulation of fatty acids accounts for the
increased heat-production following the ingestion of food.
It is clear that this type of experiment furnishes the basis for measuring
the influence of a given amount of food upon essentially the fasting
katabolism of animals. In this preliminary discussion of this feature of
the experiments we have not given all the attention that should be given,
perhaps, to the matter of computing the metabolism to a standard day
of standing and lying, as it seemed to be a refinement hardly justified at
the present stage. Further study of standard foodstuffs, with this type
of experimentation, are now under investigation.
The Standard Metabolism of Steers under Different Conditions
In order to determine the metabolic plane upon which the steer was
living at the time of beginning a fast and to note the rapidity of recovery
after fasting, a number of standard metabolism experiments were made
with each of our four animals. As outlined in our earlier study of under-
nutrition in steers,0 the conditions prerequisite for the measurement of
the standard metabolism are that the animal should be standing quietly
and should have been without food for 24 hours. Under these conditions
the standard metabolism has been measured in four half-hour periods and
computed to the 24-hour basis. Numerous metabolism experiments of
this type were made during the feeding-periods between the fasts, the data
for which have been summarized in Tables 55, 56, and 57, for steers C, D,
and E and F, respectively. The measurements secured on the first day
of each of the fasts of 5 to 14 days and on the first day of each of the
2-day fasts in 1923 were also made under standard conditions, and although
not included in these tables, should be taken into consideration in this
discussion. (See Tables 44, 45, and 46, pp. 166, 168, and 169.)
At the start it was intended to make these measurements at a chamber
temperature of not far from 20° C. Subsequently it seemed desirable to
study also the influence of different environmental temperatures. A few
standard metabolism experiments were accordingly made at temperatures
markedly lower or higher than 20° C. In addition, in order to obtain
further information regarding the influence of maintenance and submainte¬
nance rations, a series of standard metabolism experiments were made at
these two nutritive levels. It is thus possible to note whether the new
findings confirm the earlier results obtained with our first groups of steers
subjected to prolonged undernutrition. Since steers E and F were younger
than steers C and D, it is also possible to make comparisons of the influence
of age.
Factors Other than the Nutritive Level which Affect the Standard Metabolism
The comparison of the different experiments may best be made by con¬
sidering the heat-production per 500 kg. of body-weight or per square
meter of body-surface, although on either of these two bases there are
° Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 197.
THE STANDARD METABOLISM OF STEERS
229
wide differences in the results. In the series of standard metabolism
experiments with steer C, for example, the heat-production per 500 kg.
of body-weight ranges from a minimum of 5,500 to a maximum of 10,100
calories, i. e., a range of 84 per cent. Similarly, on the basis of the heat-
production per square meter of body-surface, there is a difference of 76
per cent between the minimum value of 1,180 calories and the maximum
value of 2,080 calories. These differences can be studied intelligently
only by taking account of the various factors which affect the metabolism.
Presumably, differences in body-weight are ruled out by the computation
on the basis of per square meter of body-surface. Age probably does not
play any great role in the comparison of the results obtained with steers
C and D (although their experiments cover a 3-year period from December
17, 1921, to November 26, 1924), as they were 3*4 years old at the start.
Age does play a role if the data for steers E and F are compared with
those for steers C and D, since steers E and F were yearlings. If steers
E and F are considered alone, the factor of age does not affect the com¬
parison, since the standard metabolism experiments with steers E and F
cover a period of only 3 months. Environmental temperature undoubtedly
plays a role, for the animals were purposely studied at different tempera¬
tures. The temperature to which the animal was exposed prior to and
during the test must therefore be carefully considered.
Another factor which must not be overlooked is the variability in
activity. Although the steers soon became accustomed to the respiration
chamber and the experimental technique, there were certain roughly meas¬
urable differences in their activity in the stall, due to differences in indi¬
viduality. As shown in our earlier publication,® the maximum stall
activity rarely results in an increase in metabolism of more than 15 per
cent on the average. There were no instances of excessive stall activity
during these standard metabolism experiments, however. In accordance
with our conventional method of estimating the activity from the kymo¬
graph records, we have indicated in Tables 55, 56, and 57 whether the stall
activity inside the respiration chamber was I, II, or III. Activity I repre¬
sents the minimum degree of movement and activity III the greatest
degree, but not more than 15 per cent greater than activity I. Even
activity III, however, does not involve a degree of activity sufficient to
vitiate an experiment, although it is perceptibly greater than activity I.
As can be seen from many of these experiments, in which the activities are
different but the other factors are essentially constant, there is not a great
difference in the metabolism on those days when the activity varies from
I to III. A typical instance is the comparison of the experiments of
December 26, 1922, and January 16, 1923, with steer C. In both experi¬
ments the feed-level and the environmental temperature were the same.
Activity I prevailed during the experiment on December 26 and activity
III on January 16, and yet the heat-production per square meter of body-
surface was 1,450 calories in the first case and 1,390 calories in the second
case. Differences in activity should not, however, be wholly disregarded.
° Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 209.
230
METABOLISM OF THE FASTING STEER
Level of the Standard Metabolism at the Beginning of the Different Fasts
In general, the standard metabolism of steers C and D was unusually
high on the first day of the different fasts, save in the fast following
submaintenance feeding. Indeed, although the extreme range in the values
for the first day of fasting is not any greater than the range noted in Tables
55 and 56, actually the highest values are found with both steers at the
beginning of the fasts. Thus, in Table 50, page 178, it can be seen that
the highest value for steer C, 2,090 calories per square meter of body-
surface on the first day of the fast in November 1922, is actually somewhat
higher than the highest value, 2,080 calories, recorded in Table 55. With
steer D the highest initial value in any of the long fasts is 2,490 calories
on the first day of the fast in November 1923, and the highest value
recorded in Table 56 is 2,080 calories. These high values at the beginning
of the fasts are in part to be explained on the ground that an effort was
made, although perhaps only partly successful, to bring these animals by
feeding to a somewhat higher nutritive plane, i. e., to at least maintenance,
if not above, preparatory to withstanding the fast. This effort is undoubt¬
edly reflected in general in these somewhat higher values noted on the
first day of fasting.
Influence of Environmental Temperature Upon Standard Metabolism
In certain of these standard metabolism experiments the variation in
temperature was such as to make comparisons of the influence of the
different temperatures justifiable, for the other factors were held sufficiently
constant to consider that the temperature factor may be the determining
cause of any change noted in the metabolism. The temperature effect alone
will therefore be considered at this point. With steer C on December 29,
1922, at a chamber temperature of 6.4° C. the metabolism per square meter
of body-surface was 1,560 calories per 24 hours. The day before the
temperature was 26.6° C. and the metabolism was 1,450 calories. On
January 16, 1923, the temperature was 27.8° C. and the metabolism was
1,390 calories. Thus, seemingly the lower temperature has increased the
metabolism slightly, the increase being about 100 calories per square meter
of body-surface with a lowering in temperature of about 20° C. With
steer D on December 15, 1922, at a chamber temperature of 26° C. the
heat-production was 1,740 calories per square meter of body-surface, and
on December 30, 1922, at a chamber temperature of 8.2° C. it was 1,730
calories, or practically identical with the value obtained at the higher
temperature.
In this study it is of interest to compare the series of submaintenance
experiments with steer D from January 4 to February 26, 1924, with the
submaintenance series from May 4 to June 8, 1923. The body-weight was
about the same in both cases. The environmental temperature was much
higher in the spring series than in the winter series. The ration was
exactly the same, but the stall activity was in general a little higher in
the spring. The heat-production per square meter of body-surface is
perceptibly higher in the spring series, i. e-, about 1,690 calories as compared
with 1,540 calories in the winter series. The average chamber temperature
THE STANDARD METABOLISM OF STEERS
231
was about 24° C. in the spring and about 10° C. in the winter. A similar
comparison of the data for steer C shows the same effect, although it is
a little less striking.
This evidence tends to support our earlier suggestion made in connection
with the undernutrition studies,® that the lower environmental temperature
frequently may be accompanied by a lower heat-production. There are two
contaminating features in this evidence, however. In the first place, the
activity with both animals was slightly higher in the spring series, although,
judging from our kymograph records of the activity of the animals when
inside the respiration chamber, it would seem as if the difference in the
heat-production due to a difference in activity could hardly be more than
15 per cent. If one reduced by 15 per cent the average value noted in the
spring series, the average heat-production would be 1,440 calories as com¬
pared with the average value of 1,540 calories noted in the winter series
of 1924. On this basis the lower temperature is accompanied by a higher
and not by a lower metabolism. This is a finding fully in line with the
conclusion drawn from the analysis of the data obtained in the 4-day
respiration experiments with steers E and F when on submaintenance rations
(see p. 200). It should be pointed out, however, that the study of the*
influence of environmental temperature made during the 4-day respiration
experiments of steers E and F is based upon data obtained during one
season only of the year and that the study of the influence of environmental
temperature in the experiments in the spring of 1923 and the winter of 1924
involves the possible effect of changes in season upon the metabolism. This
factor has not as yet been thoroughly studied. If we disregard for the
moment, however, any possible seasonal variation in metabolism, the correc¬
tion of the heat-production in the spring series of 1923 for the difference in
activity brings out the fact that an average difference in temperature of
about 14° C. made but a difference of 100 calories or 7 per cent in the heat-
production per square meter of body-surface. It is obvious from this par¬
ticular comparison that the temperature effect is much less with these large
ruminants than one finds in the reported observations on other animals,
although the influence of activity and shivering has too frequently been
entirely overlooked in experiments with smaller animals.
Influence of Level of Nutrition Upon the Standard Metabolism
A comparison of the standard metabolism at the maintenance and sub¬
maintenance levels of nutrition shows that with steer C the heat-production
per square meter of body-surface per 24 hours was not far from 1,600
calories when he was receiving maintenance rations and that it was per¬
ceptibly lower in the two series of submaintenance experiments. This
finding confirms our earlier finding on the effect of submaintenance feeding.
With steer D the situation is by no means so clear. The metabolism of
this animal with full maintenance rations is perceptibly higher than that
of steer C, averaging more nearly 1,800 calories per square meter of body-
surface. On submaintenance rations the fall in metabolism is only to
about 1,700 calories in the first submaintenance series, that is, from May 4
“Benedict and Ritzman, Carnegie Inst. Wash. Pub. No. 324, 1923, p. 219.
232
METABOLISM OF THE FASTING STEER
to June 8, 1923, although in the series from January 4 to February 26,
1924, the fall is much more pronounced. In general, however, the data
for both animals support the general contention that submaintenance
feeding lowers the metabolism perceptibly.
Table 57 .—Standard metabolism of steers E and F at different levels of nutrition
Heart-
rate
per
min¬
ute
In-
Aver-
Car¬
bon
di¬
oxide
pro¬
duced
per
half
hour
Heat produced per
24 hours
Steer, feed-level,
and dates
Live
weight
Tie'
loss
per
24
hours
Stall
tem¬
pera¬
ture
cham¬
ber
tem¬
pera¬
ture
pira-
tory
quo¬
tient
Total
Per
500 kg.
Per
sq. m.
Ac¬
tivity
Steer E:
Maintenance; 5 kg.
hay; 0.68 kg. meal1 —
Nov. 26, 1923..
kg.
264.8
52
kg.
6.4
°C.
16
°C.
21.3
gm.
50.9
0.87
cal.
7,000
cal.
13,200
cal.
1,980
hi
Dec. 3,1923..
266 .4
56
5.8
15
20.0
48.3
.84
6,800
12,800
1,920
hi
Dec. 10,1923..
268.8
44
6.6
20
23.0
45.8
.85
6,400
11,900
1,790
hi
Dec. 17,1923..
270.6
48
7.0
14
18.8
48.3
.85
6,800
12,600
1,890
hi
Submaintenance; 2.5
kg. hay; 0.30 kg.
meal2 —
Dec. 28,1923..
260.0
36
4.6
15
15.7
35.8
.80
5,300
10,200
1,520
ii
Dec. 31,1923..
258.0
36
3.2
14
13.8
36.4
.78
5,400
10,500
1,560
ii
Jan. 8,1924..
255.2
36
2.4
15
17.2
36.2
.78
5,400
10,600
1,570
ii
Jan. 14,1924..
256.2
38
2.6
15.7
38.4
.77
5,800
11,300
1,680
i
Jan. 21,1924..
253.6
44
3.6
11
8.4
45.5
.76
7,000
13,800
2,030
Jan. 28,1924..
252.6
44
3.0
11
15.0
40.7
.77
6,200
12,300
1,810
i
Submaintenance; 2.5
kg. hay; 0.10 kg.
meal3 —
Feb. 4,1924..
251.0
38
2.4
15
17.6
38.6
.81
5,600
11,200
1,640
ii
Realimentation4 * —
Feb. 18,1924..
237.2
‘52
1.2
17
15.1
34.1
.76
5,200
11,000
1,580
i
Steer F:
Maintenance; 5 kg.
hay; 0.68 kg.
meal 1 —
Nov. 27, 1923..
290.0
60
5.4
18
21.8
50.9
.85
7,100
12,200
1,900
ii
Dec. 4,1923..
293.0
44
5.4
16
20.5
52.2
.85
7,300
12,500
1,940
hi
Dec. 11,1923..
296.0
52
8.0
18
22.2
46.0
.82
6,600
11,200
1,740
hi
Dec. 18,1923..
298.0
42
4.0
10
15.1
48.2
.84
6,800
11,400
1,790
hi
Submaintenance; 2.5
kg. hay; 0.30 kg.
meal2 —
Dec. 29,1923..
285.6
38
3.4
16
20.3
45.2
.80
6,600
11,600
1,780
ii
Jan. 2,1924..
284.8
42
3.2
12
15.6
41.5
.77
6,300
11,100
1,700
ii
Jan. 9,1924..
280.6
42
2.8
16
16.7
39.6
.79
5,900
10,500
1,610
i
Jan. 17,1924..
279.2
42
3.4
18
22.7
46.4
.81
6,700
12,000
1,840
i
Jan. 22,1924..
278.8
38
2.6
13
20.6
44.8
.79
6,600
12,000
1,810
i
Submaintenance; 2.5
kg. hay; 0.10 kg.
meal 3 —
Jan. 29,1924..
276.4
36
3.2
18
21.0
46.4
.79
6,900
12,500
1,900
hi
Feb. 5,1924..
272.8
40
3.0
17
16.1
42.9
.78
6,400
11,700
1,780
ii
Realimentation 6 —
Feb. 19,1924..
260.6
‘ 64
1.8
16
16.3
34.4
.73
5,400
10,400
1,540
i
1 The period of maintenance feeding began on Nov. 19, 1923.
1 The period of submaintenance feeding began on the afternoon of Dec. 17, 1923.
* The period of lower submaintenance feeding began on the afternoon of Jan. 28, 1924.
« The experiment on Feb. 18, 1924, was made 24 hours after the 5-day fast of Feb. 12 to 17. The steer had con
Burned 1.75 kg. hay and 500 gm. meal at the end of the fast, or 24 hours before this experiment.
3 Steer had just stood up.
• The experiment on Feb. 19, 1924, was made 24 hours after the 6-day fast of Feb. 12 to 18. The Bteer had con
Burned 1.45 kg. hay and 500 gm. meal at the end of the fast, or 24 hours before this experiment.
THE STANDARD METABOLISM OF STEERS
233
In considering the standard metabolism of steers E and F, and particu¬
larly the influence of a marked curtailment in ration, it must be borne in
mind that in the series of experiments reported in Table 57 these animals
were just a little over a year old. In the series of 4-day experiments from
December 1924 to May 1925, however, in which the influence of sub-
maintenance feeding was also studied (see Table 53, p. 195), they were
practically a year older, or about 21/2 years old. According to the standard
metabolism measurements reported in Table 57, the curtailment in ration
resulted at first in a material fall in the metabolism of steer E, which
persisted for the three days, December 28, December 31, and January 8.
There was then a tendency for the metabolism to rise during the rest of
the month. Prior to the curtailment in ration, the heat-production per
square meter of body-surface was approximately 1,900 calories on the
average, and during the submaintenance period it was not far from 1,700
calories, i. e., there was no appreciable change in the metabolism. Simi¬
larly with steer F, the average heat-production prior to submaintenance
feeding was about 1,800 calories and during the entire submaintenance
period it was not far from the same. It would appear, therefore, as if
the metabolism of these young animals did not react to the submaintenance
regime as in the case of the older animals, probably because a strong effort
to continue growing persisted at this age.
Complications arise, however, in making strict comparisons in that the
temperature factor undoubtedly enters into certain of these experiments.
Thus, the high heat-production of 2,030 calories per square meter of body-
surface with steer E on January 21, 1924 (see Table 57), may be in part
accounted for by the fact that the chamber temperature was but 8.4° C.
When these animals, E and F, were studied a year later, however, in the
4-day experiments (see Table 53, p. 195), there was an almost immediate
response in the metabolism to the submaintenance feeding, in spite of the
fact that prior to the respiration experiment the submaintenance ration
had been fed at the most for but three weeks. Here, again, the pronounced
changes in environmental temperature play somewhat of a role, and com¬
parisons of the various days can be made only when the environmental
temperature is taken into consideration. Yet it is clear that at the age of
2 V2 years these animals reacted strikingly to a 3 weeks’ period of lowered
food intake, in that the metabolism was distinctly depressed.
Steers C and D show an almost immediate response in metabolism to
the lower feed-level. In none of the experiments with steers C, D, E, and
F was the submaintenance regime carried far enough to note how long
the low plateau would be held. Judging from the two submaintenance
series in May 1923, and in January and February 1924, there was no dis¬
position for the metabolism per square meter of body-surface to decrease
materially in the length of time covered by these submaintenance periods.
Although the analysis of the standard metabolism of these steers is
complicated by the influence of factors such as environmental temperature,
the amount and character of the previous feed, and the age of the animal,
the most directly comparable experiments show clearly that adult animals
which have been upon full feed and are presumably in a maintenance
234
METABOLISM OF THE FASTING STEER
condition, respond definitely to a submaintenance ration in that they have
a persistently low metabolism. The two young animals, when 1 year
old, did not react so rapidly to curtailed rations, but at the age of 2V2
years the substitution of a submaintenance ration in place of the mainte¬
nance ration resulted in a distinctly lower metabolism, even when the
submaintenance regime had prevailed for only three weeks.
This particular feature of the rapidity of onset of a low metabolism
following submaintenance rations constitutes, we believe, the danger in
attempting to estimate the fasting katabolism of steers by the method
of studying the metabolism of an animal on a full maintenance ration and
then on a submaintenance ration, when the submaintenance ration has been
given for a period of three weeks or more. These conditions introduce
not only the effect of the lowered ingestion of food, which is supposed to
be studied, but the depressing effect of the submaintenance regime upon
the basal or fasting katabolism.
SUMMARY
(1) Two adult steers, C and D, were subjected at varying intervals
during a period of 2% years to 7 different fasts of from 5 to 14 days in
length. Two of the fasts followed pasture feeding, one a submaintenance
ration of hay alone, and the rest a maintenance ration of hay and meal. The
effects of intermittent fasting and of sudden and marked changes in envi¬
ronmental temperature were studied in a further series of fasts of 2 and 3
•days’ duration, at approximately weekly intervals. Two younger and
smaller steers, E and F, fasted for 5 or 6 days following submaintenance
feeding. The gaseous metabolism measurements in all these fasts were
made in three or four consecutive half-hour periods. Subsequently each
animal fasted again, and the gaseous metabolism was measured in 8-hour
periods during three consecutive days. A number of continuous 4-day
respiration experiments (2 days on feed and 2 days fasting) were made
with steers E and F when they were about 2% years old, in which the
-effects of variations in the amount and character of the ration and of
high and low environmental temperatures were studied.
(2) Great irregularity in the loss in weight during fasting could be
explained, as during the feed periods, by irregularity in the intake and
outgo of visible matter, particularly the water intake. The magnitude of
the large losses during the first few days was influenced by the pre-fasting
feed-level. The losses were largest in the fasts following pasture feeding.
In the fasts following maintenance feeding on hay and meal the losses
were much smaller, and in those which followed submaintenance feeding
they were still smaller. After the fourth day of fasting the daily losses
in live weight became smaller and nearly similar, irrespective of the
previous ration or the individual animal. It is concluded that two animals
of the same size and age, receiving feed similar in character and amount,
are fairly close physiological duplicates in respect to the loss in weight
during fasting. The loss or gain in live weight per se, however, can not
be accepted as an index of change in body-tissue without taking into
consideration other factors, particularly the consumption of water and
the excretion of urine and feces.
(3) The insensible perspiration from day to day was reasonably constant
under the same conditions of feeding, particularly if the environmental
temperature remained unchanged. Marked changes in temperature, how¬
ever, were often accompanied by changes in the insensible perspiration even
at the same feed-level, a large insensible loss frequently appearing with a
high temperature and vice versa. The chief factor affecting the magnitude
of the insensible perspiration was the amount of the ration, the loss being
higher with heavy feeding than with light feeding. When the steer had
been fasting for 24 hours there was usually a definite decrease in the
insensible perspiration, provided the temperature remained essentially
unchanged. On the second day there was a still greater decrease. After
the third or fourth day the loss remained practically constant at about
3 or 4 kg. per day in the fasts following maintenance or pasture feeding
235
236
METABOLISM OF THE FASTING STEER
and at about 2.5 kg. in the fasts following submaintenance feeding. With
the resumption of feeding the insensible perspiration increased.
(4) During fasting the water consumption was affected by changes in
the environmental temperature. On some fasting days no water was taken
and on other days fairly large amounts were taken. Steer C, when fasting
after submaintenance feeding, drank practically no water for 9 days. In
other fasts the animals refused water for periods of 3 and 4 days. In
general, less water was consumed in the fasts following submaintenance
or pasture feeding than in those following maintenance feeding. Water
may be withheld from fasting steers without detriment, especially if the
steers have previously been on reduced rations or on pasture.
(5) The daily weight of fresh feces during the feed periods was in general
twice that of the ration. During fasting the fecal excretion was greatly
reduced, although some feces were passed daily throughout the entire fast,
irrespective of its length. On the first day there was usually a small
decrease in the weight of feces. On the second day the excretion was
somewhat less than half as much as on the first day, save in the fast after
submaintenance feeding. After the fifth day the average excretion was
about 1.5 kg. per day. The number of defecations on the first day was
less in the fasts following pasture or submaintenance feeding than in those
after maintenance feeding. During the 14-day fast the number of defeca¬
tions and the amount of each defecation gradually decreased until about
the seventh day, after which there were a large number of small defecations
daily. At the beginning of the fast the feces were soft and plastic, but
as the quantity decreased during the fast they became visibly firmer, being
dry and pilular by the fifth day. After eight days their consistency was
variable, some passages being firm and fibrous and others soft. The feces
were exceedingly offensive in odor toward the end of the fast. The per¬
centage of dry matter in feces increased in some fasts and decreased in
others. A satisfactory explanation for this anomalous situation was not
found. The actual weight of dry matter in feces decreased rapidly until,
on the fifth day, the feces contained about 0.5 kg. of dry matter, irrespective
of the previous feed-level.
(6) Smaller amounts of urine were voided during submaintenance than
during maintenance or pasture feeding. The volume decreased as the fast
progressed, the lower level of excretion being noted in the fasts starting
at the low feed-level. The volume was seemingly independent of the
environmental temperature and the water intake. A maximum individual
voiding of 3,048 grams was shown by one steer on the fifth day of one
of the fasts following pasture feeding- Small amounts of less than 100
grams were sometimes passed. Large changes in the content of the bladder
thus seem possible, even under the restricted conditions of fasting.
(7) Extensive chemical analyses of the steers' urines were made. The
effect of fasting was to change the composition of the urine from one
containing a relatively low per cent of urea and significantly high amounts
of hippuric acid and amino acids to one in which the nitrogen distribution
on the percentage basis was similar to that in the urine of man when
eliminating approximately 4 grams of nitrogen. The ammonia content
SUMMARY
237
was extremely low and was not increased during fasting. The content
of ketone bodies was low. This, together with the low ammonia-content,
indicates a lack of acidosis during fasting. In the two larger animals the
creatinine excretion was relatively constant, and, per kilogram of body-
weight, was similar to that of man. Little or no creatine was excreted by
the two larger animals during fasting, but the two younger and smaller
animals excreted noticeable amounts.
(8) The total loss of nitrogen varied with the length of the fast and
the character of the preceding ration, being notably low in the fasts after
submaintenance feeding.
(9) The steers seemed to adjust themselves temperamentally to fasting
even more rapidly than to a submaintenance regime. After the second day
no particular irritation or craving for feed was shown. No signs of lack
of vigor were exhibited, the steers appearing as strong and healthy, even
on the last day of the 14-day fast, as in the early stages of fasting.
(10) The animals became more quiet and inert in their muscular exer¬
tions as the fast progressed, spending a larger proportion of the time lying
down than when on feed.
(11) Rumination practically ceased after the second day, persisting
longer after a dry ration than after pasture feeding-
(12) The heart-rate was lower during the periods of submaintenance
feeding and seemingly more rapid at the lower environmental temperatures.
Fasting resulted in an almost continuous fall in the heart-rate to a level
as low as 28 or 30 beats per minute in the longest fasts.
(13) The respiration-rate during fasting was about 9 or 10 per minute.
(14) The normal rectal temperature was not far from 38.2° C. and was
singularly unaffected by the feed-level, the environmental temperature,
or by fasting.
(15) The skin temperature was measured only during the fasts of steers
C and D following submaintenance feeding. The small amount of evidence
secured suggests that neither fasting nor submaintenance feeding has a
marked effect upon the skin temperature, but that environmental tempera¬
ture plays a large role.
(16) The respiratory quotient, when the steer was receiving feed regu¬
larly, was about 1.00 or above, depending somewhat upon the character
of the feed and the time elapsing after feed had been eaten. On the first
day of fasting the quotient was about 0.82 or 0.83. On the second and
third days it was still lower, but after the third day remained fairly con¬
stant at about 0.70, indicating that the steer was burning essentially fat.
(17) The heat-production decreased markedly during the first few days
of fasting, and less markedly thereafter. Uniformity in the heat-production
per square meter of body-surface appeared with steer C on about the fourth
day but not until the seventh or eighth day with steer D. The metabolic
level of steer D was distinctly higher than that of steer C in practically
all instances, in part explained by his greater restlessness. A higher
metabolism was noted with steers E and F when fasting after submainte¬
nance feeding, indicating the higher metabolism of the younger protoplasm.
(18) The short respiration experiment of four half-hour periods, even
when the animal is standing the entire time, gives a computed heat-
238
METABOLISM OF THE FASTING STEER
production not far from that found in 24-hour periods when the animal
is allowed to lie or stand at will.
(19) In the 4-day respiration experiments a somewhat higher heat-
production was noted with alfalfa hay than with timothy hay, when a
maintenance ration was fed. The submaintenance level of metabolism
was much lower than the maintenance level and, referred to body-weight
or body-surface, was essentially the same with both steers, regardless of
the character of the ration.
(20) The environmental temperature had practically no influence upon
the metabolism when the animal was receiving a maintenance ration of
timothy hay or when fasting after such a ration. At the submaintenance
level of nutrition with timothy hay, however, a higher metabolism was
noted with a low environmental temperature, whether the animal was
receiving feed or was fasting. The effect was apparently not proportional
to the difference in temperature.
(21) A difference of from 20 to 30 per cent between the metabolism in
the lying and in the standing position was noted on days with feed. In
some instances this difference diminished during fasting and practically
disappeared after the second or third day, but in other instances it per¬
sisted even to the fourth or fifth day. The correction for this difference
is not so important when the value of different feeds is being compared, as
it is when an approximation of the true fasting katabolism is desired. When
cattle have been fed maintenance rations, a sufficiently close approximation
of the fasting katabolism can be determined in general while they are
standing, about 32 hours after the last food, and if a satisfactory reduction
is made for lying in the measurement thus obtained, the basal metabolism
per 24 hours lying may be computed. This procedure should give a value
which is suitable as a base-line in studies of the superimposed effects of
various factors, provided the experiments are made shortly after this basal
determination.
(22) The level in the plateau of metabolism varied with the different
seasons of the year and with the quantity and character of the ration.
Thus, the so-called basal metabolism, when once attained after withholding
feed, was seemingly not constant with the same animal, even if he had
been previously upon a maintenance ration, for a higher plateau was noted
after timothy than after alfalfa hay. Submaintenance feeding, particularly
with alfalfa hay, lowered the level of the fasting metabolism markedly.
Since it is impossible with steers to insure complete muscular repose at
any time desired and complete cessation of digestive activity (except after
4 or 5 days without food) , it is debatable whether any attempt to secure
the equivalent of basal conditions in man is feasible. Furthermore, it does
not seem necessary in general practical problems to determine this
equivalent.
(23) The probable basal energy requirement of cattle is about 1,300
calories per square meter of body-surface per 24 hours, when the animal is
lying the entire time, save during prolonged fasting or fasting following
extreme undernutrition. In two instances the heat-production on this
basis of computation was 1,060 and 1,190 calories. These abnormally low
values are in part explained by the influence of a sudden transition from
SUMMARY
239
a cold to a warm environment. In general, however, fasting per se, pro¬
vided the level of nutrition has not been too greatly lowered by previous
undernutrition, results in a heat-production per square meter of body-
surface per 24 hours much nearer 1,700 calories, when the animal is standing.
(24) A comparison of the actually measured fasting katabolism with
that computed from the metabolism on maintenance and submaintenance
rations shows that the computation method gives results too low. Since
the submaintenance ration was fed for three weeks or more before its effect
was measured, the metabolism was determined not only under conditions
of less digestive activity due to the reduction in feed but during the initial
stage of undemutrition, which has been shown to lower metabolism greatly.
It is suggested that the more logical method might be to measure the
metabolism during a 5-day respiration experiment, in which the first two
days would represent maintenance feeding and the last three days sub¬
maintenance feeding. The third day would thus be a transitional period
and the level of the metabolism on the fourth and fifth days would be
that caused by the reduced ration before the effect of undernutrition was
manifested.
(25) The steers were extremely slow about eating after a fast, taking
hours to consume even 1 or 2 kg. of hay but consuming the grain with
greater relish. The metabolism increased almost immediately after the
animal was fed, the size of the increase depending somewhat upon the
time occupied in eating the relatively small amounts consumed. After
the initial response the metabolism was not further stimulated.
(26) The ingestion of 7 kg. of hay produced, not during the height of
digestion but throughout an entire 24-hour period, an increase in the total
heat-production of 50 per cent in the case of timothy hay and 60 per cent
in the case of alfalfa hay.
(27) The standard metabolism was frequently lower at the lower envi¬
ronmental temperatures. Differences in the activity of the steers obscured
the results somewhat, but it is concluded that the temperature effect is
much less with these large ruminants than with other animals.
(28) When the adult animals had been upon full feed and were pre¬
sumably in a maintenance condition, they responded definitely to a sub¬
maintenance ration in that they showed a persistently low metabolism.
Animals a year old, however, did not react so rapidly to reduction in feed,
although when they had reached the age of 21/2 years a submaintenance
regime of only 3 weeks also resulted in a distinctly lower metabolism.
ADDENDUM
Since this report was sent to the printer, several publications from other
institutions have appeared which are of interest in this connection. These
appeared too late, however, to be discussed in this monograph, and we can
here only call attention to the place of publication.0
° Forbes, Braman, Kriss, Fries, et al., Journ. Agric. Research, 1926, 33, p. 579.
Forbes, Fries, Braman, and Kriss, Journ. Agric. Research, 1926, 33, p. 591.
Fries, Beretning fra N. J. F.’s Kongress, Oslo, June, 1926.
Titus, Journ. Agric. Research, 1926, 33, p. 887.
ACKNOWLEDGMENTS
The experimental work in connection with the research reported in this
monograph was entirely carried out at Durham, New Hampshire, under
the direction of the junior author. Most of the routine work, involving the
details of handling, weighing, feeding, and watering of the animals, of
taking daily records of pulse, body temperature, and other body measure¬
ments, was in the hands of Mr. A. D. Littlehale. Assisted by chemically
trained students, he also carried out the preparation of rations and the
sampling and weighing of feeds, feces, and urine.
The gas analyses during the second year’s work of this series were made
by Mrs. Lois A. Ritzman. With this exception, all the gas analyses were
made by Miss Helen M. Hilton, who also had charge of the routine work
connected with the operation of the respiration chamber. For their fidelity
and patience we are deeply indebted.
The analyses of feed and excreta for the first four fasts were made by
Mr. J. A. Gallagher, under the direction of Dr. H. R. Kraybill, chemist
of the New Hampshire Experiment Station. Later all these determinations
were taken over by Dr. Thome M. Carpenter, of the Nutrition Laboratory
staff, who was assisted in the details of the determinations by Messrs. P.
P. Saponaro, E. L. Fox, and E. S. Mills, and Miss D. L. Tibbetts. The
computations of the results of these chemical analyses were carried out
by Mr. W. H. Leslie with his characteristic accuracy and thoroughness.
The editing of this report, as indeed the one preceding it, was in the
capable hands of Miss Elsie A. Wilson.
240
SUBJECT INDEX
pxaa
Acid bodies, Index of fasting condition . 8
In urine . 121
Stimulus to metabolism . 7,228
Acidosis . 124
Activity (muscular), degree of, during respiration experiments . 175,190,229
During fasting . 135,237
Kymograph records of . 135
Types of . 6
Age, influence on creatine excretion . 120,121
creatinine coefficient . 122
creatinine excretion . 120
metabolism . 172,177,180,191,229,233,234,239
nitrogen in urine . 122
Animals used . 38
Individuality in . 164,180,191
Psychological duplicates . 62-63 , 84 , 235
Apparatus, changes in . 24-37
Gas-analysis (Carpenter) . 31-36
Motor-generator . 25
Respiration chamber. Additions to . 26-28
Aliquo ting device . 29-31
Disk factor . 29-30
Disk opening, size of . 31
Control tests with carbon dioxide . 36-37
Swivel stanchion . 27
Appearance of animals during fasting . 136-137,237
Appetite after fasting . 136 , 223 , 239
Behavior, during fasting . 133-135,237
realimentation . 136
Body conditions . 133-137
measurements . 130-133
position, correction of basal metabolism measurements for differences in . 211—213,238
During fasting . 135, 190
During metabolism measurements . 40 , 152
Effect on metabolism . . 151-152 , 202-203 , 238
Method of recording change in . 134
Body-surface, computation of. . . . 153-156
Law of . 153,210-211,221-222
Physiological significance of. . 221-222
Relation to heat-production v . !. . 221-222
Body-temperature. See Temperature, Rectal and Skin.
Body-weight . 54-63 , 235
Changes in, during fasting . 56-63
Index of change in body-tissue . 59,63
Influence of water intake upon . 58
Method of determining . 55
Warm, empty . 154
Carbohydrates, path of absorption of . 19
Carbon dioxide, calorific value of . 146-148
Carbon-dioxide production, during feeding and fasting . 161-165,190
Measurement of, as index of heat-production . 145,161-165
Ratio between, and heat-production . 147-148
Carnivora and herbivora compared . 14
Chest circumference . 130-133
Chronology of research . 41-53
Condition of animal. See Body conditions; Flesh; Nutrition, state of.
Conditions, experimental . 41-53
Cost of digestion . 225
Digestive tract, content of. See Fill.
Disposition, during fasting . 133-134
Energy. See Heat-production; Metabolism.
Energy transformations, vital activities represented by . 4-8
'A
241
242
METABOLISM OF THE FASTING STEER
Environment. See Temperature, environmental.
Exchange, gaseous. See Metabolism.
Excreta. See Feces; Urine.
Fasts, details of 14-day fasts . .
Details of other fasts . * .
History of earlier experimental fasting .
Length of .
Practical value of .
Feces . .
Amount on feed and fasting .
Chemical composition of .
Collection of . ; . . .
Device for separation of, from urine (with cows) . . .
Dry matter in .
Frequency of . .
Influence of water consumption upon .
Nitrogen in . . . .
Physical characteristics of .
Feed, amount and kind given .
Digestibility of . . . . • > .
Energy involved in conversion of .
Influence of, on body- weight losses during fasting .
feces . .
metabolism during fasting .
metabolism after fasting .
metabolism during feeding .
rectal temperature .
respiratory quotient .
standard metabolism .
Last, before fast .
Productive use of .
Provision for, in respiration chamber. . .
Specific dynamic action of .
Feed-level preceding fasts .
Fill, after fasting .
Dry matter in .
Influence of changes in, on chest girth .
Minimum amount of .
Moisture content of .
Of fasting horse . .
Per cent of live weight .
Quantitative changes in, during fasting .
Total .
Variations in, during undernutrition .
Flesh. See, also, Nutrition, state of.
Condition of, during fasting .
Maximum loss of, during fasting .
Food. See, Feed.
Gas analysis, importance of .
Gas-analysis apparatus (Carpenter) .
Gaseous exchange. See Carbon-dioxide production.
Grain. See Feed.
Hair .
“Handling” .
Hay. See Feed.
Heart-rate .
Heat-production. See, also, Metabolism .
During fasting . . .
Computation of, from experiments at two different feed-levels
In 3 consecutive 24-hour periods .
Per 500 kg. of body-weight .
Per square meter of body-surface .
Minimum .
Humans and animals compared .
Plateau in. Incidence of . . .
Level of .
Total per 24 hours .
PAGE
. 43-48
. 48-52
. 3-4
. 55
. 9-11
. 81-97,236
. 82-89
. 91-97
. 28,82
. 106
. 91-95
. 86-89
. 87
. 95-97
. 47,89-91
. 42
. 225
. 6-8
. 56-63
. 82-89
. 198-199
. 39,222-223,239
196-198,217,238,239
. 143
. 160-161
. 231-234
. 52-53
. 5
. 26-27
. 7,225
. 55,170
. 154
. 88
. 130
. 94-95
. 17-18,92-94
. 95
. 81,97
. 17
. 16-17,88
. 54
136
128
31-32
31-36
. 137
. 136
. 137-141,237
. 237-238
. 171-192
. 10, 209-218,
223, 224, 234,239
. 185-192
.152,174-177,184
.179-180,184-185
. 216,218-222
. 211
.204^207,208,217
. 206-209,238
.171-174,180-184
SUBJECT INDEX
243
Heat production — Continued page
During 2 days on feed and 2 days fasting . 192-203
Influence upon, of body position . 151-152,202,211-213,238
environmental temperature . 219-221
feed . 196-199 , 224-228 , 239
Method of computing . , . 148-150
Of fasting cows . 22
Ratio between, and carbon-dioxide production . 23,147-148
Relation to body-surface . 153,221-222
Standard. See, also, Metabolism . 228-234
Herbivora and carnivora compared . 14
Humidity, influence of, on water consumption . 80
Index of metabolism, heart-rate as . 187 , 141
State of nutrition as . 131,133
Individuality in animals . 135,180
Insensible perspiration . 19,40,63-75,235
Investigations of others on fasting ruminants . 12-13,104-106
Katabolism. See Heat-production; Metabolism.
Ketosis . 124
Literature on fasting ruminants . 12-23,104-106
Live weight. See Body-weight.
Lying. See Body position.
Maintenance. See Feed; Feed-level; Heat-production; Metabolism.
Metabolism. See, also, Heat-production.
Basal, of steers . 203-222,238
Conditions prerequisite for measurement of . 150-152,203-204,218,221,238
Correction of, to standard day lying and standing . 211-213
Basal, of humans, effect upon, of neutral bath . 220
Factors lowering . 220
Body position during measurement of . 40,152
Fasting . 158—192
Computation of, from experiments at two different feed-levels . 10,209-218
Error in method . 213—218,223,234,239
Defined . 5 , 8—9
Minimum per square meter of body-surface . . .
Plateau in, incidence of .
Level of .
Significance of .
Time of beginning of . . .
Four -day experiments .
Heart-rate as index of .
Influence upon, of body position .
environmental temperature
feed .
state of nutrition . .
Measurements, made or computed . .
Method of presenting data on .
Standard .
Conditions necessary for measurement of . . . . .
Factors affecting .
Influence upon, of environmental temperature
feed-level .
Level of, at start of fasts . .
Methane .
. 216,218-222
. 204-207,217
. 206-209,238
. 4-5
. 8,18
. 192-203
. 137,141
. 151-152
. 219-221
. 222-228,239
. 174
. 144-150
. 156
. 228-234,239
. 9,43,151,152,228
. 228-234
. 230-233
. 231-234
. 230
22 , 144-145 , 149-150 , 160 , 204
Methods:
Chemical analysis of mine . 107
Collection of feces . 82
urine . 07
Computation of fasting katabolism of steers . 209-218,223,239
Conduct of 4-day respiration experiments . 192-194
24-hour respiration experiments . 188
Determination of body-weight . 55
body-surface . 153—156
change in position of animal . 134
Determination of chest-girth . 130
heart-rate . 137
244
METABOLISM OF THE FASTING STEER
Methods — Continued paoh
Determination of insensible perspiration . 65
rectal temperature . 142
respiration-rate . 141-142
skin temperature . 143
water consumption . 77
Device for separation of urine from feces (with cows) . 106
Presentation of gaseous metabolism data . 156—158
Separation of feces (Edin) . 88
Nitrogen, distinction between fecal and urinary . . . 129
Economy . 122-123
Fecal . 95—97 , 129
Level . 124,126, 128
Loss . 127-130 , 237
Requirement during fasting (Grouven) . 18
Urinary . 115-116,128
Nutrition, state of, at start of 3-day respiration experiments . 189
Indicated by chest girth . 131,133
Influence of, on fasting metabolism . 174
heart-rate . 137,141
metabolism in general . 222
rectal temperature . 143
standard metabolism . 231-234
Oxygen, calorific value of . 146, 150
Periods (in chamber), length of . 156,185-187,192
Perspiratio insensibilis. See Insensible perspiration.
Plan of research . 39-40,237
Plane of nutrition. See Feed-level; Nutrition, state of.
Problems studied . 39-40
Protein (dry), maximum draft upon, during fasting . 128
Quotient, respiratory . 36, 146, 158-161 , 167, 188-189,237
Rations. See Feed.
Realimentation, influence of, on metabolism . 222-223,239
Residues, intestinal. See Fill.
Respiration chamber. See Apparatus.
Respiration-rate . 141-142 , 237
Respiratory exchange. See Carbon-dioxide production; Metabolism.
quotient . 36,146, 158-161 , 167 , 188-189 , 237
Rumination . 135 , 237
Salivation . 135
Salt . 81
Size. See Body-weight.
Skin . 137
Soda-lime . 29
Specific dynamic action of food . 7,225
Standard metabolism. See Metabolism.
Standing. See Body position.
Submaintenance. See Feed; Feed-level; Heat-production; Metabolism; Under nutrition.
Surface area. See Body-surface.
Temperature,
Environmental, control of . 25
During respiration experiments . 170
Influence of, on heart-rate . 141
metabolism . 175-177 , 182-184 , 200-202 , 206 , 219-221 , 230-231 , 233 , 238
rectal temperature . 143
skin temperature . 143-144
urination . 99,103
Rectal . • . 142,222,237
Skin . 143-144,237
U ndernutrition . 4,39
Behavior during . 133
Body-surface estimations during . 154
Heart-rate during . 137
Influence of, on standard metabolism . 239
nitrogen-level . 128
Skin temperature during . 143
SUBJECT INDEX
245
Undernutrition — Continued
Variations in fill during .
Urine . . .
Acid bodies in . . .
Amount of, during fasting . . . ■ .
Analyses by other investigators .
Chemistry of .
Chlorides in . .
Collection of .
Conclusions on composition of, during fasting .
Creatine in .
Creatinine coefficient . . .
Preformed creatinine . .
Total creatinine .
Device for separation of, from feces (with cows) . .
Frequency of, during fasting . .
Hourly excretion of, during fasting .
Influence on amount of, of environmental temperature .
feed-level .
water consumption .
Litmus test .
Nitrogen in .
Economy .
Hippuric acid .
Partition of .
Urea and ammonia .
Of fasting horse .
Phenols in .
Physical properties of . . .
Phosphorus in .
Preservation of .
Relation between volume and dry matter .
nitrogen content .
water consumption .
Statistics of results on .
Timing of passing of .
Vigor during fasting .
Vital activities, phases of, represented by energy transformations
Water . . . .
Analysis of .
Consumption of, during fasting .
Influence of, on body-weight losses during fasting .
urine output .
Influence upon, of environmental temperature .
fasting (intermittent) .
feed-level . . .
humidity .
Method of determining .
Provision for, in respiration chamber . . .
Relation between, and consistency and amount of feceB.
dry matter in feed .
volume of urine .
Refusal of, for long period .
Temperature of .
Weight. See Body-weight.
PAGE
. 54
. 97-126,236-237
. 121
. 99-103
. 104-106
. 104-126
. 114
. 25,27-28,97
. 123-126
. 120-121,126
. 122
. 120
. 120
. 106
. 101-103
. 101
. 99,103
. 99
. 103
. 98-99,123
115-116, 121-122,127-128
. 122-123
. 119-120
. . 116-121
. 119
. 14
. 121
. 103
. 121
. 107
. 103
. 115-116
. 102-103
. 107-114
. 25
. 134
. 4-8
. 75-81,236
. 77
. 79-81
. 58
. 81,103
. 79
. 79-80
. 77-81
. . 80
. 77
. 27
. 87
. 76,81
. 103
. 80-81
. 77
AUTHOR INDEX
PAGE
Andersen, A. C . 145,149
Armsby, H. P . 5,10,
23,32,147,154,197,209,211
Atwater, W. 0 . 29
Awrorow, P . 75
Baer, J . 105
Bailey, C. V . 35
Bischoff, Th. L. W . 15,63
Blatherwick, N. R . 105
Braman, W. W . 22, 23,
32, 145, 147, 154, 204,211,214,215,239
Brody, S . 179
Capstick, J. W . 21,22,201
Carpenter, T. M. . - .6,34,104,105,107,225
Cochrane, D. C . 214
Cohn, G . 12,95,139
Csonka, F. A . 148
Deighton, T . 22
Delcourt-Bernard . 220
Dorno, C . 184
Du Bois, E. F . 154
Edin, H . 88
Elting, E. C . 179
Ewing, P. V., and F. H. Smith . 88
Folin, 0 . 107,120,124
Forbes, E. B . 59,106,116,152,202,239
Fries, J. A _ 23, 32, 40, 59, 106, 116, 147,
151,154,197,202,211,214,239
Grouven, H . 3,15,59,63,97,104
Haigh, L. D . 154
Harris, J. A . 153
Hasselbalch, K. A . 32
Hawk, P. B . 3
Hill, A. Y . 22
Hogan, A. G . 154
Howe, P. E . 3
Ignatief . 20
Jaquet, A . 32
Kellner, O . 76
Knoll, A. P . 139
PAGE
Kriss, M.. 40, 59, 106, 116, 151, 202, 211, 239
Krogh, A . 151
Lassaigne, J. L . 14
Lefevre, J . 220
Ling, S. M . 148
Lusk, G . 8
Magee, H. E . 202
Magendie . 12
Mayer, Andre . 220
Meeh, K . 154
Meissl, E . 20
Miles, W. R . 4,29,143,222
Mpllgaard, H . 149,212
Moulton, C. R . 154,211
Palladin, A . 105
Peters, R. A . 105
Petren, K . .115,124
Pott, A. F . ... 141
Prayon, J . 105
Rapport, D . 148
Root, H. F . .....40,64,68,75
Roth, P . 4,29,222
Rubner, M . 7
Sanctorius . 63
Sjollema, B . 106
Skouby, C. 1 . 154
Smith, H. Monmouth . 4,29,222
Talbot, F. B . 148
Tangl, F . 21
Tisdall, F. F . 107
Titus, H. W . 239
Trowbridge, P. F . 154
Valenciennes, A . 3
Van der Zande, J. E. . . . 106
Voit, E . .15,63,210,211
Weirzuchowski, M . 148
Weiss, R . 148
Willinger, J . 107
Wood, T. B . 21,201
Zuntz, N . 19,32
246
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