Special scientific report--wildlife

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TEST OF GRIT TYPES IN
ALLEVIATING LEAD POISONING
IN MALLARDS

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UNITED STATES DEPARTMENT OF THE INTERIOR

FISH AND WILDLIFE SERVICE

BUREAU OF SPORT FISHERIES AND WILDLIFE

Special Scientific Report - Wildlife No. 107

UNITED STATES DEPARTMENT OF THE INTERIOR, STEWART L. UDALL, SECRETARY
Stanley A. Cain, Assistant Secretary for Fish and Wildlife and Parks

Fish and Wildlife Service, Clarence F. Pautzke, Commissioner
Bureau of Sport Fisheries and Wildlife, John S. Gottschalk, Director

TEST OF GRIT TYPES IN
ALLEVIATING LEAD POISONING IN MALLARDS

By Alfred J, Godin
Patuxent Wildlife Research Center, Laurel, Maryland

Special Scientific Report — Wildlife No. 107
Washington, D.C. • June 1967

For sale by the Superintendent of Documents, U.S. Oovemment Printing Office
Washington, D.C. 20402 - Price 16 cents

CONTENTS

Page

Abstract ii

Materials and methods 1

Results 2

Mortality 2

Body weight losses 3

Shot retention 3

Food consumption 4

Gizzard examination 4

Conclusions 4

References 5

Tables ; • . 6

ABSTRACT

Mallard ducks (Anas platyrhynchos) were given either 0, 2,
or 4 No, 6 lead shot in combination with 4 grit treatments; no
grit, coarse sand, mica granite, and crushed oystershell. Each
combination was replicated three times. Ducks were maintained
on a diet of whole corn. An analysis of variance indicated no
significant differences in mortality in relation to grit type,
but a significant difference (at 0.05 level) in mortality between
the lead shot doses. Oystershell grit apparently reduced mor-
tality of ducks dosed with 4 shot but not to a degree statistically
significant. In all treatments, mortality was closely associated
with shot retention. Ducks retaining shot for 2 weeks usually
died.

11

TEST OF GRIT TYPES IN ALLEVIATING LEAD POISONING IN MALLARDS

For many years wildlife investigators and sportsmen alike
have been concerned over the annual waterfowl mortality caused
by lead poisoning. Wetmore (1919) and others focused on the
fact that lead poisoning frequently occurred in wintering areas
deficient in grit and suggested grit be added to such areas. As
part of the current research being conducted on lead poisoning
by the Section of Wetland Ecology of the Patuxent Wildlife
Research Center, a study was initiated to determine possible
effectiveness of various grit types in alleviating lead poisoning.

Special thanks are extended to Hsin-yuan Tu, Geologist, Soil
Survey Laboratory, Soil Conservation Service, U.S. Department of
Agriculture, Beltsville, Md. , for determining the mineral and
chemical composition of grit types. Thanks are also due biolo-
gists Harold D. Irby, Louis N. Locke, Robert G. Heath, and John L.
Sincock, Patuxent Wildlife Research Center, for their valuable
assistance.

MATERIALS AND METHODS

A 60-day test was made using 288 first-year, drake mallards.
The ducks were obtained in late July from a breeder in Birdsboro,
Pa. Two weeks before initiation of the study, the ducks were
wing-clipped (primaries cut off one wing) and placed in 36 pens
for conditioning. Pens were 9x5x2 feet high and provided
with a 260- gallon stock-watering tank (Cornwell and Hartung, 1963).
Each pen and tank was partitioned into two units to hold eight
ducks. Birds were deprived of grit during this conditioning
period. Before putting J:he birds on test, grit removal was
attempted on 12 live mallards with a water aspirator (Nord, 1941).
This was found impractical and was discontinued.

A 3 X 4 factorial comparison was made of the effects of 3
quantities of No. 6 lead shot per bird (0, 2, and 4) in combination
with, (1) no additional grit and the addition of (2) coarse sand,
(3) mica granite, and (4) crushed oystershell. The 12 treatments
were replicated 3 times and randomly assigned to the 36 pens.
Since treatments could not be initiated in all pens at one time,
the replicates were "blocked" into 3 time periods, each period
being assigned 1 pen of each of the 12 treatments. The replicates
were initiated between August 26 and September 13, 1965.

Lead shot were placed in the gizzard using a funnel and small
plastic tube. Initially each duck was weighed and leg-banded.
Body weights were also recorded at 14- day intervals, at the time
of death, and at the end of the test. All ducks were fluoroscoped
on the 14th and 28th day after dosing to determine shot retention.
Ducks not given lead were fluoroscoped to provide comparable
handling.

Cages were flushed with water daily and each tank was drained,
cleaned, and refilled every 3 days. Whole corn and the assigned
grit were offered ad libitum.

The average daily corn consumption per duck was calculated
at intervals for each treatment group by multiplying the number
of surviving ducks by the number of days required to nearly
empty a feeder. The bird-days for a group were calculated when-
ever a duck died and the amount of corn consumed was divided by
the bird-days to estimate average consumption per bird day.

At the end of the test, surviving ducks were killed and all
ducks necropsied. The condition of the gizzard and the number
of lead shot retained were recorded.

RESULTS

Mortality

Percent mortality over the 60-day period for all treatment
replicates is shown in Table 1. The greatest mortality of ducks
given lead shot, regardless of grit type, occurred between 16-20
days after dosing. Within 25 days after dosing, 27 percent of
the ducks given 2 shot, and 51 percent of the ducks given 4 shot,
succumbed. Only 8 ducks which had been given lead lived beyond
the 25th day after dosing.

An analysis of variance of percent mortality for the first
25 days (Table 2) showed no significant difference among grit
types. A significant difference in mortality between the 2-shot
and 4-shot doses was demonstrated at the 0.05 level of significance.
The mean percents of mortality over the first 25 days for 2 and
4 shot treatments, regardless of grit type, were 28 and 53,
respectively. Over the 60-day period mean percents of mortality
for the 2 and 4 shot treatments were very similar at 35 and 54,
respectively.

Body Weight Losses

The percent loss of initial body weight at 14-day intervals
over the 60-day test is presented in Table 3. The peak weight
losses (up to 24 percent) among all grit treatments and shot
doses were recorded during the first 28 days. Ducks which died
during the test, however, frequently lost more than 50 percent
of their initial body weight.

Weight losses among lead-dosed survivors and those birds
not given lead were similar. The consistent weight loss by all
birds could have resulted from the inadequacy of the corn diet.
Several factors could explain why weight losses among lead-dosed
survivors were less than expected: Survivors may have rid them-
selves of shot early enough to avoid poisoning; they may have been
hardier birds initially; or, as mortality progressed, they may
have experienced less stress from crowding than did the undosed
birds. There was no apparent relationship between mortality and
initial body weight.

Shot Retention

The percent of shot retention, as determined by fluoroscopy,
for mallards surviving 14 and 28 days after dosing is presented
in Table 4. Fourteen days after dosing, 29 percent of those
ducks given 2 shot and 54 percent of those ducks given 4 shot
had retained at least 1 shot in their gizzards. Twenty-eight
days after dosing only one surviving duck (on 2 shot dose) had
retained shot.

All ducks on coarse sand which had retained shot at 14 days
died before fluoroscopy on the 28th day. However, all ducks
which passed their shot before the 14th day survived the 60-day
test (Table 5).

Of the ducks given 4 shot, a higher percent of those on
oystershell grit retained shot to the 14th day than on other
grit types. Paradoxically, ducks on oystershell grit and given
4 shot suffered the lowest percent mortality of the 4 grit
treatments.

The number and percent of ducks which retained shot at death
for each grit treatment are shown in Table 6. Slightly more than
half of the ducks given 2 lead shot and offered coarse sand, mica
granite, and oystershell grit retained shot at death.

Bellrose (1959) cited work by Jordan that showed penned,
wild mallards which were force fed 1 or more No. 6 shot passed
the shot as early as the first week or as late as several weeks
after dosing. This was also true in this study.

Food Consumption

The average daily corn consumption per duck for the control
ducks (no grit, no shot) during the 60-day test was 0,12 pound.
This corresponds closely with Jordan's (1953) study in which
wild penned mallards consumed 0.13 pound of corn daily in early
fall. Corn consumption by birds for each treatment is shown in
Table 7. Average consumption per bird decreased with increased
shot dose on all grits except crushed oystershell.

Gizzard Examination

Among birds which died during the test in the same treatment,
pathological conditions of the keratinous pads and interpad mucosa
of the gizzards varied from a normal yellow color to dark, greenish-
brown staining with ulcerations.

The gizzards of the 60-day survivors on crushed oystershell
had a characteristic white coating on the inner lining, and the
gizzards of the survivors on other grits appeared a normal yellow
color without ulcerations.

Ducks not offered additional grit retained considerable grit
which had been ingested before they were put on test.

CONCLUSIONS

1. Mortality of lead-dosed mallards varied among treatment
replicates. The greatest mortality of ducks on the different grit
types and given 2 or 4 shot occurred 16-20 days after dosing.
Bellrose (1959) observed that mallards with lead shot still in
the gizzard died on the average of 21 days after ingesting it, and
that 20 days was the average "turnover" period of leaded mallards
in the wild.

2. An analysis of variance indicated no significant differences
in mortality in relation to grit types, but a significant difference
at the 95 percent level of confidence was demonstrated in mortality
between shot dosage levels. The total mortality of ducks given 4
shot was lowest for the group an oystershell grit but the difference
was not statistically significant. However, the comparatively lower
mortality of lead-dosed ducks given oystershell grit suggests that
further studies of a calcium grit might be fruitful.

3. The greatest body weight losses occurred in the first

28 days after dosing among all treatments. Ducks that died which
had been given either 2 or 4 lead shot lost an average of 54
percent of their initial body weight. There appeared to be no
relation between mortality and initial body weight.

4. Shot retention 2 weeks after dosing as determined by
fluoroscopy was greater in the ducks given 4 shot than those
given 2 shot. Twenty-eight days after dosing only one surviving
duck had retained at least one shot. Although a greater percent
of the ducks given crushed oystershell grit and 4 lead shot had
at least 1 shot at 14 days. This group of ducks suffered the
least mortality among the other grit treatments given 4 lead shot.

5. Gizzards of lead-dosed mallards which died during the
test were stained a dark, greenish-brown and had ulcerations.

LITERATURE CITED

Bellrose, Frank C. 1959. Lead poisoning as a mortality factor
in waterfowl populations. Illinois Natural History
Survey Bulletin 27(3) :235-288. Urbana Illinois.

Cornwell, George and Rolf Hartung. 1963. A holding pen for

diving ducks. Journal of Wildlife Management 27(2) :
290-292.

Jordan, James S. 1953. Consumption of cereal grains by migratory
waterfowl. Journal of Wildlife Management 17(2) : 120-123.

Nord, Warren H. 1941. A technique of removing lead from the
gizzards of living waterfowl. Journal of Wildlife
Management 5(2) : 175-179.

Wetmore, Alexander. 1919. Lead poisoning in waterfowl. USDA
Bull. 793:1-12

Table 1. Mortality (in percent) durin<? a 60-day test among
replicated pens of 8 mallards each treated with
grit and lead shot.

Percent Mortal

ity by Repl:

Lcates

Lea

d Shot Doi

sage

No

Shot

2

Shot

4

Shot

Treatment

A

B

C

Ave.

A

B

C

I've.

A
25

B
50

C Ave.

No Grit

0

0

0

0

25

38

38

33

100 58

Coarse Sand

0

13

0

4

50

13

25

29

13

100

75 63

Mica Granite

0

0

0

0

25

38

50

38

65

50

63 58

Crushed

0

0

0

0

38

13

75

42

25

38

50 38

Oystershell

Mean

1

35

54

Table 2. Percent mortality for first 25 days among 8 duck

replicates given lead shot and various grity types.

Oystershell

Percent Mortality by Replicates

Lead Shot Dosage

2 Shot 4 Shot

Treatment

A

B C Ave. ABC

Ave,

No Grit

25

25

25

25

Coarse Sand

50

13

25

29

Mica Granite

25

13

50

29

Crushed

25

0

63

29

Mean

28

25 50 88 54
13 100 75 63
63 50 63 58
25 38 50 38
53"

Table 3. Percent loss of initial body weight of survivors at 14 day
intervals over 60-day test period.

Lead Shot Dosage

No Shot 2 Shot 4 Shot

Day Day Day

Treatment No. 14 28 42 56 60 No. 14 28 42 56 60 Na. 14 28 42 56 60
Birds % Wt. Loss Birds % Wt. Loss Birds % Wt. Loss

No Grit 24 8 11 12 14 16 16 7 9 9 11 12 10 9 8 6 9 12

Coarse 23 6 9 11 11 12 17 13 12 11 10 10 9 13 13 9 7 6

Sand
Mica 24 n 13 n n H 15 11 12 13 12 11 10 24 22 18 17 18

Granite
Crushed 24 11 12 11 10 10 14 4 6 5 4 4 15 10 10 10 8 8
Oyster she 11

Table 4. Retention of at least 1 shot in the gizzard as revealed by 14
and 28 day post-dosage fluoroscopy.

Lead Shot

Dosage

2

Shot

4

Shot

14

days

28

days

14

days

28

days

Treatment No.
Dosed

No.
Alive

7o with
1 Shot

No.
Aliv£

7o with
: Shot

No.
Alive

7o with
i Shot

No.
Alive

7o with
; Shot

No Grit 24
Coarse Sand 24

Mica 24

Granite
Crushed 24

Oystershell

23
23

24
24

48
13
25
29

18
20
19
19

6
0
0
0

21
22
23
24

52
50
48
63

11
11
12
15

0
0
0
0

Total
Average

94

29

76

1

90

53

49

0

Table 5. Shot retention (at least 1 shot) by 60-day survivors given
2 or 4 lead shot as determined by 14 and 28 day post-dosage
fluoroscopy.

Lead

Shot

Dosage

2

Shot

4

Shot

Treatment

No.
Dosed

60-day
survivors

7o with
14 day

shot
28 day

60-day
survivors

7o with
1 14 day

shot
28 day

No Grit

24

16

25

6

10

10

0

Coarse Sand

24

17

0

0

9

0

0

Mica Granite

24

15

7

0

10

10

0

Crushed
Oystershell

24

14

7

0

15

40

0

Table 6. Number of mallards which died during the 60-day test and retained
at least 1 lead shot.

Lead Shot Dosage

Treatment No. 2 Shot 4 Shot

Dosed No. Died 7o with shot No. Died 7. with shot

No Grit 24 8 100 14 93

Coarse Sand 24 7 57 15 87

Mica Granite 24 9 56 14 86

Crushed 24 10 60 9 100

Oystershell ,

Table 7. Food consumption per bird per day (lb.) over 60-day test for
mallards given various types of grit and lead shot.

Treatment

Average food intake per bird per day (lb.)
Lead Shot Dosage

No Shot

2 Shot

4 Shot

No Grit .12

Coarse Sand . 11

Mica Granite . 10

Crushed Oystershell .09

10
09
10
09

08
08
09
09

Mean

.11

10

09

Note — The author's present address is

Alfred J. Godin , State Supervisor
Wildlife Services, USBSFW
256 State Office Building
Hartford, Connecticut 06115

* U S, GOVERNMENT PRINTING OFFICE . 1967 0—274-763

The Department of the Interior, created in 1849, is a Department of
Conservation, concerned with management, conservation, and develop-
ment of the Nation's water, wildlife, fish, mineral, forest, and park and
recreational resources. It has major responsibilities also for Indian and
Territorial affairs.

As America's principal conservation agency, the Department works to
assure that nonrenewable resources are developed and used wisely, that
park and recreational resources are conserved for the future, and that
renewable resources make their full contribution to the progress, pros-
perity, and security of the United States, now and in the future.

UNITED STATES

DEPARTMENT OF THE INTERIOR

FISH AND WILDLIFE SERVICE

BUREAU OF SPORT FISHERIES AND WILDLIFE

WASHINGTON. D. C. 20240