CLINICAL AND PATHOLOGICAL MANIFESTATIONS
OF ZINC DEFSCIENCY AND ZlNC TOXKITY

lN GROWING CHICKENS

Thesis {or ”to Doqru of M. S.
MICHKGAN STATE UNWERSETY

Charles Franklin Hall
1959

adv-‘-

THESIS

 
  
  
   

  
  

LIBRARY

Michigan Sta £6

,3 University 6"

CLINICAL AND PA'IHOLCISICAL MANIFESTATIONS OF ZINC DEFICIENCY

AND ZINC ‘IDXICI'IY IN GROWING CHICKENS
By
CHARLES FRANKLIN HALL
AN ABSTRACT

Submitted to the College of Veterinary Medicine
Michigan State University of Agriculture and
Applied Science in partial fulfillment of

the requirements for the degree of

MASTER OF SCIENCE
Department of Veterinary Pathology

1959

Approved WW

ABSTRACT

Three purified diets were randomly assigned to nine groups of
one-day-old chicks thus providing three lots of chicks on each diet.
The basal ration (zinc deficient) contained 16 ppm of zinc; the control
ration contained 20 ppm of added zinc, or a total of 36 ppm; and the
toxic ration contained 5,000 ppm of added zinc, or a total of 5,016 ppm.
Environmental sources of zinc were eliminated by coating cages with
plastic and by supplying distilled drinking water in glass waterers.

One lot of chicks on each diet was withdrawn for study when the
chicks were 10, 17 and 31 days old, respectively.

Zinc-deficient birds failed to grow well, did not feather properly
and developed severe dermatitis, particularly on the feet. Patho-
logical findings included hyperkeratosis, an apparent increase in
number of islets of Langerhans in the pancreas accompanied by loss of
chromatin in the cells of the islets, an apparent inhibitory effect on
deposition of lymphoid tissue, and a decrease in blood lymphocyte levels.

Birds fed toxic levels of zinc failed to grow and were all dead
before 31 days of age. Pathological findings included severe fatty
change in the liver, hyaline and hydropic changes in the pancreas and
differential leukocyte counts characterized by an increase in immature

lymphocytes. It is concluded that Changes were due to a combination of

starvation and toxicity.

CLINICAL AND PA'IHOLOGICAL MANIFESTATIONS OF ZINC DEFICIENCY

AND ZINC TOXICITY IN GROWING CHICKENS

By

CHARLES FRANKLIN HALL

A THESIS

Submitted to the College of Veterinary Medicine
Michigan State University of Agriculture and
Applied Science in partial fulfillment of

the requirements for the degree of

MASTER OF SCIENCE
Department of Veterinary Pathology

1959

INDEX

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . 1
REVIEW OF LITERATURE . . . . . . . . . . . . . . . . . . . . . . 2
Zinc - An Essential Trace Mineral . . . . . . . . . . . . . 2
Zinc in Swine Nutrition . . . . . . . . . . . . . . . . . . 2
Zinc in Poultry Nutrition . . . . . . . . . . . . . . . . . 3
OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
EXPERIMENTAL PROCEDURE . . . . . . . . . . . . . . . . . . . . . 8
RESULTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . .ll
Livability and Growth . . . . . . . . . . . . . . . . . . .11
External Symptoms and Lesions . . . . . . . . . . . . . . .ll
Hematology. . . . . . . . . . . . . . . . . . . . . . . . .14
Microbiological Findings. . . . . . . . . . . . . . . . . .18
Histopathological Findings. . . . . . . . . . . . . . . . .18
DISCUSSION . . . .. . . . . . . . . . . . . . . . . . . . . . .27
SUMMARY. . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

REFERENCES CI'I'ED I I I I I I I I I I I I I I I I I I I I I I I I 31

TABLE 1

TABLE 2

TABLE 3

TABLE 4

LIST OF TABLES

C(MPOSITION OF THE BASAL DIET . . . . . .
LIVABILIflI I I I I I I I I I I I I I I I
Gm. I I I I I I I I I I I I I I I I I

SUMMARY OF DIFFERENTIAL LEUCOCYTE COUNTS.

12

12

17

------------

.................

----------------------

 

 

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

LIST OF FIGURES

'IHE NOMAL (A) AND ZINC-DEFICIENT (B) CHICK.

FOOT - NORMAL (A) AND ZINC-DEFICIENT (B)
(DORSALVIEW)OI-ooeoooooee

FOOT - NORMAL (A) AND ZINC-DEFICIENT (B)
(VENTRALVIEW)Io-oooaoooon

LYMPHOCYTIC ACCIMULATIONS - DIFFUSE (A)
ANDFOLLICULAR(B)..........

SKIN - NORMAL (A) AND ZINC-DEFICIEN‘I' (B) .

SKELETAL MUSCLE - NOBVIAL (A) AND ZINC-TOXIC (B).

LIVER - ZINC-TOXIC (A,B) AND ZINC—DEFICIENCY? (C).

PANCREAS - CONTROL (A), ZINC-DEFICIENT (B)

ANDZINC'IOXIC‘C)OQcocoon-ea.-

13

15

16

19

20

22

24

25

ACKNOWLEDGEMENTS

The author is indebted to a number of people for the successful
completion of this study:

To Dr. C. C. Morrill, Head, Department of Veterinary Pathology,
for his guidance;

To Dr. R. F. Langham and Dr. C. K. Whitehair of the Department of
Veterinary Pathology for assistance and guidance;

To Dr. P. J. Schaible and Dr. R. H. Roberson" of the Department of
Poultry Science for supplying the birds, feed, equipment and labor
necessary to carry out this study; ‘

To his fellow graduate students for supplying morale and assistance
when needed;

To Mrs. Beverly Seward for assistance in preparation of the
manuscript;

And most of all, to his wife, Alice, and daughter, Eleanor,
for making the necessary sacrifices that would allow for completion

of the study.

* Present address: Poultry Department, New Mexico A. & M. College,
State College, New Mexico.

-1-

INTRODUCTION

Zinc and other trace'mdnerals are known to be essential elements
in the metabolism.of farm animals, including poultry. Until recently
it was considered that common feedstuffs contained enough available
zinc to meet the nutritive requirements of animals.

When parakeratosis of swine was demonstrated to be, at least in
part, a zinc deficiency disease, it appeared desirable to study the
zinc needs of chickens more closely. This has been done by a number
of workers.

The research described in this thesis was undertaken to determine

the pathology of experimental zinc deficiency and toxicity in chickens.

-2-

REVIEW OF LITERATURE
Zinc - An Essential Trace Mineral

Morrison (12) states that the presence of zinc in animal tissues
has long been recognized. The premise that the mineral is essential
to life has been supported by the work of many investigators. In 1934
Todd's: 31. (23) demonstrated that rats failed to grow prOperly and
develop normal hair when deficiencies of zinc existed in rations. More
recently other investigations have shown zinc to be essential to the
proper development of swine (7,8,9,24), chickens (l3,14,19,25) and
turkeys (22).

The functions of zinc are not completely understood, but McCollum
._E._l' (10) and Pensack and Klussendorf (16) cite references indicating
that zinc has a profound effect on a number of enzyme systems. Hormone
associations are also suggested.

Zinc is abundant in nature. Most forage and pasture plants contain
30-100 ppm of zinc on a dby basis. These levels have been considered
to be sufficient to meet the needs of animals raised under normal condi-
tions (5).

Zinc in Swine Nutrition

In 1953 Kernkamp and Ferrin (4) described a denmatosis of swine
characterized by parakeratosis. Attempts to transmit the disorder were
unsuccessful, and these workers suggested that the condition might be
nutritional or metabolic in origin.

Shortly thereafter Tucker and Salmon (24) reported that the
feeding of added zinc had a beneficial effect on parakeratotic swine.
These (24) and other workers (7,8,9,16) also demonstrated.the relation-

ship of high calcium diets to the incidence of the disorder and suggested

-3-

that calcium interfered with the availability of zinc in the ration.
Hanson and Sorensen (3) have suggested that parakeratosis may be
closely related to fatty acid deficiency.

To determine at what levels zinc could be safely added to swine
rations, several workers (1,8) studied possible toxic effects of
high levels of added zinc. Lewis‘gt‘gl. (8) reported that no toxic
effects appeared in pigs being self-fed on a ration containing 1,000
ppm supplemental zinc. Brink'gt‘gl. (1) reported that diets containing
above 2,000 ppm of zinc produced toxicity in weanling pigs characterized
by depressed rate and efficiency of gain, lowered feed intake, arthritis,
axillary Space hemorrhage, gastritis, catarrhal enteritis, mesenteric
congestion, and hemorrhages in the ventricles of the brain, lymph nodes
and spleen. Toxic levels of zinc frequently produced death within 21 days.

Zinc in Poultry Nutrition

Following the discovery that added zinc in the ration exerted a
beneficial effect in the prevention and cure of parakeratosis in swine,
many investigators fed diets containing various levels of zinc to
poultry.

Mehring gtMgl. (11) found that rations containing up to 814 ppm of
zinc produced no apparent adverse effects when fed to chickens. Pensack
and.K1ussendorf (16) fed added zinc to broilers at levels up to 3,000
ppm. Levels above 1367 ppm of added zinc suppressed.growth but did not
produce anatomical or pathological change. These workers concluded that
suppressed growth was due to reduced feed intake rather than to toxicity.
Sturkie (21) studied the effects of 2,320 ppm of zinc in the drinking
water of six laying hens. During the 20 day period of the trial, water

consumption drOpped to one half of normal, body weight decreased 0.40

-4-

pounds per bird, and production ceased. One bird died during the
course of the trial. When water without added zinc was restored, water
consumption returned to normal levels immediately, and four of five
survivors were laying within ten days.

Pensack and Klussendorf (16) fed White Rock hens for eleven months
on diets containing 180 ppm of added zinc. Production, fertility and
hatchability in treated pens were comparable to that in untreated
pens; and zinc content of eggs was not increased. All treated birds had
differential leucocyte counts within normal range.

Roberson (17) reports that naturally occurring zinc deficiency has
not been observed in chickens. However, the zinc needs of growing
chickens have been studied by a number of workers in recent years. Young
{gt‘gl. (25) have presented evidence to show that not more than 40 ppm.of
added zinc is required for maximum growth and development when the basal
diet contains 15 ppm of zinc. Pensack gt 21. (15) suggest that no more
than 20 pm of zinc is required to meet the needs of the growing chick
when purified casein rations are fed. Roberson and Schaible indicate
that 30 ppm or more supplemental zinc make a ration independent of that
in the basal ingredients. Edwards (2) 23‘31. presented evidence in
1958 to show that a Chick’s environment and source of water may supply
the Chick's need for zinc even when purified diets containing no zinc
are fed.

Symptoms of zinc deficiency in poultry have been described by
several investigators. O'Dell and.Savage (l3) and.O’Dell‘gt‘§l. (14)
describe the symptoms of zinc deficiency in chicks as slow growth,
shortening and thickening of the long bones, development of frizzled

feathers, labored respiration, unsteady gait, keratosis of the skin and

increased packed cell volume.

Supplee st 21. (22) report that zinc-deficient turkey poults fail
to grow well, have abnormal bone formation and fail to develop normal
feathers.

Roberson and Schaible (19) and Roberson (17) report that condi-
tions causing acute zinc deficiency in the growing chick produced
depressed growth, poor utilization of feed, failure to feather prOperly
with retention of body down and a ragged condition of wing feathers,
dermatitis of feet and a stilted gait.

Young 33 31. (25) described similar symptoms in young chicks and
described a near absence of barbs on all but the tips of the primary
wing feathers.

The histopathology of zinc deficiency in chickens has been described
by O'Dell 23 a1. (14) and'Young 33 31. (25).

O’Dell gj‘gl. (14) found that the epiphyseal cartilage of long
bones was reduced considerably in width and that there was less cell
division than normal. ‘Maturing cartilage cells were small and appeared
less active than normal. The bony collar of the shafts of long bones
was thinner, but shaft diameter was greater than in the control birds.
Osteoblasts were fewer in number, and the Haversian canals were larger.
Hematopoietic activity in Haversian canals was increased.

Lymphoid tissues of the thymus and bursa of Fabricius were atrophic
in zinc-deficient chicks.

The skin of deficient chicks showed hyperkeratinization, particularly
marked on the wings, legs and feet. Hyperkeratinization of skin extend-

ing into the feather follicles resulted in atrophy of follicles and feathers.

-6-

Esophageal changes were characterized by parakeratosis. Hyper-
plasia of pancreatic tissue with an increased number of islets of
Langerhans was seen, but many of the islets cells had undergone
hydropic degeneration.

Similar bone changes have been described by Young ££.El- (25).

 

 

-7-

OBJECTIVES
At the time the studies described in this thesis were initiated
no published information was available as to the pathological changes
accompanying zinc deficiency and toxicity in chickens.
These studies were initiated to determdne what changes, if any,
would be produced in selected tissues of growing chickens being fed

rations deficient and toxic with respect to zinc levels.

-3-

EXPERIMENTAL PROCEDURE

The randomization of chicks to pens or replicates was made in the
following manner: one-day-old, White Rock, male chicks received from
a commercial hatchery were weighed and distributed into consecutive
weight groups, such as 36-38, 39-41, etc., each having a weight range of
three grams. The groups with the lowest and highest weights were
discarded. An equal number of chicks from each weight group were
randomized to each pen. This method.minimized the effect of initial
weight differences on final results. In these studies 90 chicks were
assigned to nine pens of 10 chicks each.

Three purified diets were randomly assigned to the pens in tripli-
cate, thus providing three lots of chicks on each diet. The basal
diet (Table 1) contained 16 ppm of zinc and served as the zinc-deficient
diet. The second diet (control) contained 20 ppm.of added zinc producing
a total zinc level of 36 ppm. The third diet (toxic) contained 5,000
ppm of added zinc producing a total zinc level of 5,016 prm. Added
zinc was supplied in the form of zinc sulfate.

Birds were maintained in electrically heated, starting batteries
with raised wire floors. Tb prevent environmental sources of zinc
from influencing results, all battery parts were coated with opoxy-
resin except the wire floors and dropping pans which were coated with
shellac. The galvanized (zinc plated) water troughs were replaced with
one—gallon, glass, baby chick founts with plastic bases. Distilled
water was used instead of tap water as a source of drinking water.

Three pens of birds, i.e. one replicate of birds on each diet,
were withdrawn for study when chicks were 10, 17 and 31 days old.

Hereafter, these age groups will be referred to as replicate one,

TABLE 1

COMPOSITION OF THE BASAL DIET

 

 

 

Ingredients Grams/Kg.
Glucosel 627.00
Isolated soybean protein2 250.00
Corn oil ' 30.00
Ground cellulose3 30.00
DLemethionine 7.00
Glycine 3.00
CaHPO4 22.00
CaOO3 14.70
NaCl 6.00
M9304 2.50
FeSO4-7H20 0.333
KI 0.333
CuSO4°5H20 0.026
CoClz-GHZO 0.0017
NazMoO4-2H20 0.0083
ZnSO 0.00
Chol ne chloride 1.50
Inositel 0.25
Niacin 0.05
CaPantothenate 0.02
a-Tbcopherol acetate 0.02
Thiamin HCl 0.01
Riboflavin 0.01
Pyridoxine HCl 0.045
Folic acid 0.004
Menadione ’ 0.0005
Biotin 0.0002
Vitamin BIZ (1 mg/gm) 0.02
Vitamin A (250,000 IUlgm) 0.02
Vitamin 03 (200,000 ICU/gm) 0.002

 

l - Cerelose, Corn Products Sales Co., 440 New Center Bldg.,
Detroit, Michigan.

2 - Drackett Assay Protein C-l, The Drackett Products Co.,
Cincinnati 32, Ohio.

3 - Solka Floc, The Brown Co., Berlin, New Hampshire.

-10-

replicate two and replicate three respectively.

Average bird weight, symptoms and external lesions were determined
prior to killing the birds. The tissues from one half of each pen
sample were pooled.for microbiological examination. Selected tissues
of remaining birds from each pen were collected for pathological exami-
nation. Blood films were prepared from each bird, stained according to
the Wright method, and differential leucocyte counts determined. Skin,
skeletal muscle, heart, lung, liver, spleen, pancreas, duodenum, kidney,
adrenal, testis and brain were collected in 10% isotonic formalin for
histopathological examination.

Uniform techniques of tissue collection were employed to allow
for accurate appraisal of any tissue change noted. Skin was collected
from.an interdigital space on the foot. Skeletal muscle was collected
from the superficial pectoral muscle and was trimmed on a longitudinal
plane. Heart was collected and trimmed in cross section at the mid-
ventricular level. Lung was trimmed in cross section at midplevel
antero-posteriorly. Liver and spleen were trimmed in cross section.
Pancreas and duodenum were collected together and trimmed in cross section
at a level midway down the duodenal loop. A triad of tissue consisting
of kidney, adrenal and testis was removed and in a plane that would
allow for a single imbedding procedure. Brain was removed in $232 and
trimmed on a sagittal plane.

Following fixation, dehydration, imbedding and sectioning, tissues
were stained with hematoxylin and eosin. Selected tissues were also

stained with Sudan IV for fat and with Mallory's aniline blue.

-11-

RESULTS
Livability and Growth

Livability during the course of the experiment is given on
Table 2.

Average growth rates for birds are given on Table 3.

In replicate one (10 days old), 10 control birds averaged 75.2
grams; 10 zinc-deficient birds averaged 66.4 grams; and 8 surviving
zinc-toxic birds averaged 38.5 grams.

In replicate two (17 days old), 10 control birds averaged 166.1
grams; 10 zinc-deficient birds averaged 94.1 grams; and 6 surviving
zinc-toxic birds averaged 49.2 grams.

In replicate three (31 days old), 8 surviving control birds
averaged 300.5 grams; and 9 surviving zinc-deficient birds averaged
143.1 grams. No survivors were on the toxic ration at the time samples
were taken.

External Symptoms and Lesions

All control birds on each replicate appeared normal when examined.

Zinc-deficient birds appeared to be normal in replicate one except
for slight growth depression.

When replicate two of zinc-deficient chicks was examined, stunting
was readily observable. Feathering was not proceeding at a normal rate,
and the bodies of the birds were still primarily covered with down.
Wing feathers which were present were juvenile and ragged. No evidence
of skin change was noted.

Zinc-deficient birds of replicate three had symptoms and external
lesions as described for replicate two, but the changes were more

pronounced (Figure 1). In addition the shanks of birds in this group

-12-

TABLE 2

LIVABILITY

H
k
H

 

Surviving Chicks of 10 Started

 

 

Treatment Replicate one Replicate two Replicate three
(10 days old) (17 days old) (31 days old)
Control 10 10 8
Zinc deficient 10 10 9
Zinc toxic 8 6 0
TABLE 3
GROWTH

 

-_

i

Average Weight in Grams

 

Treatment Replicate one Replicate two Replicate three
(10 days old) (17 days.old) (31 days old)

Control 75.2 166.1 300.5

Zinc deficient 66.4 94.1 143.1

Zinc toxic 38.5 49.2

 

 

.13..

 

B

‘I'
Figure l : A, The normal chicken; B, The zinc-deficient chicken.

*Courtesy of P. J. Schaible and R. N. Roberson.

-14...

showed bluish discoloration. Dermatosis was not generalized, but the
feet of the chicks had severe encrustations dorsally (Figure 2) and
ventrally (Figure 3). The skin was cracked in some of the birds, and
Open bleeding was observed. Gross bone deformities as described by
O'Dell‘gt‘gl. (14) and Young 23 a1. (25) were not observed.

Zinc—toxic birds in replicate one were stunted and'weak. The
skeletal muscles appeared pale and grayish.

When replicate two of zinc-toxic birds was examined, stunting was
very severe. Chicks were extremely weak and had difficulty standing.

All birds in replicate three of zinc-toxic birds were dead prior
to the sampling period.

No gross internal lesions were noted in any of the birds examined.
Size of organs varied between treatment groups, but this was considered
proportionate to weight differences of birds.

Hematology

Blood films were prepared from birds which were killed for
histopathological examination. The results of differential leucocyte
counts are summarized in Table 4.

No attempt was made to classify lymphocytes as to size. The
relative numbers of large and small lymphocytes was considered to be
in normal range except in blood films prepared from birds fed toxic
levels of zinc. In these instances, a marked increase in numbers of
large lymphocytes was seen.

All differential counts were considered to be in normal range
except for replicate one birds fed toxic levels of zinc and replicate
three chicks fed deficient levels of zinc. In each instance the

lymphocyte count was low and the heterophil count high.

 

*
Figure 2 : A, Foot from a normal chicken (dorsal view). B, Foot from a
zinc-deficient chicken with hyperkeratosis (dorsal view).

*Courtesy of P. J. Schaible and R. N. Roberson.

-15..

 

I»
Figure 3 : A, Foot from a normal chicken (ventral view). B, Foot from
a zinc-deficient chicken with hyperkeratosis (ventral view).

*Courtesy of P. J. Schaible and R. N. Roberson.

-17_

TABLE 4

SIMMARY OF DIFFERENTIAL LEUOOCYTE COUNTS]-

 

 

Replicate one (10 days old)

 

 

 

 

 

Lympho- Hetero— Mono- Eosino— Baso— Myelo-
Treatment cytes phils cytes phils phils cytes
Control 71.6 21.0 4.6 1.6 1.2
Zinc deficient 66.4 25.2 4.6 0.8 2.6
Zinc toxic 47.5 46.0 3.5 .___ 2.0 1.0
Replicate two (17 days old)
Lympho— Hetero— Mono— Eosino- Baso- ‘Myelo—
Treatment cytes phils cytes phils phils cytes
Control 66.4 26.8 2.8 ____ 4.0 ___
Zinc deficient 57.4 35.2 2.6 1.0 3.6 0.2
' Zinc toxic 66.6 21.6 3.3 2.0 5.6 0.6
Replicate three (31 days old)
Lympho- Hetero- Mono- Eosino- Baso- Myelo-
Treatment cytes phils cytes phils phils cytes
Control 67.0 26.8 3.4 0.4 2.2 0.2
Zinc deficient 47.0 45.2 3.2 0.2 4.0 0.4
Zinc toxic2

 

l EXpressed in numbers of cells per 100 counted
2 No survivors

-18..

Microbiological Findings
Intestinal contents from each replicate of control and treatment
groups yielded coliform and Proteus organisms. These organisms were
not considered to be pathogenic to the chicks.
Pooled tissues, consisting of heart, lung, liver and spleen,
failed to yield micro-organisms when inoculated on bovine bloodpenriched
tryptose agar and incubated for 48 hours at 37.5 C. This was uniformly
true for each treatment group of each replicate.
Histopathological Findings

General Findings:

 

Lymphocytic accumulations, diffuse and follicular (Figure 4), were
observed in assorted tissues of all chicks examined. Accumulations
were most evident in the tissues from control birds of replicate three.
Numerous mitotic figures were present in affected areas. On the other
hand, few accumulations were seen in the tissues from zinc-deficient
chicks of replicate three.
Skin;

The skin from control birds appeared to be normal. The epidermis
was 4-7 cells thick and was covered by a thin layer of keratin (Figure 5).

The skin from zinc-deficient birds was thickened. The epidennis,
in some sections, was increased in thickness up to 20 layers of cells.
The layer of keratin was also thickened up to five times normal. Nuclei'
were not present in the keratinized layer; but in some sections, the
line of demarcation between the stratum granulosmm and the stratum.corneum
was indistinct, many of the outer cells of the stratum.granulosum appear-
ing to be undergoing keratinization. These changes are illustrated in

Figure 5.

-19-

 

Figure 4: A, Diffuse lymphocytic accumulations in the small intestines.
B, Follicular lymphocytic accumulations in the pancreas. X 150, H. & E.
stain.

—20-

     
  

'n ,. 7’3"). ,n N. '."'
in ,e' .. ;.«..“.-.. , ,5 ,
‘ fi \ 7’ V. ‘ .
‘\l .. " ' ‘

‘1'”
..U'I:.

  

     

*v

Figure 5: A, Skin from a normal chicken. B, Skin from a zinc-deficient
chicken with hyperkeratosis. '

X 150, H. & E. stain.

-21-

The skin of birds fed toxic levels of zinc appeared nonmal.

Skeletal muscle:

 

The fibers of skeletal muscle from control birds were normal in
appearance. In bundles, individual fibers were rather indistinct;
and the nuclei were pale and rather sparsely distributed (Figure 6).

Skeletal muscle from zinc-deficient birds had.more distinct
fibers and nuclei, but individual fibers appeared somewhat smaller in
cross section than those of the controls.

The skeletal muscle fibers in birds fed toxic levels of zinc were
very small in cross section. The nuclei'wereiquite numerous and
deeply basophilic. The individual fibers were quite distinct. The
fibers did not appear degenerative (Figure 6).

Cardiac muscle:

 

Myocardial change, characterized by the presence of diffuse and
focal aggregates of heterophils and lymphocytes, was seen in individual
birds from each treatment group. The reaction was not consistently
found in any treatment group, however. Since bacterial pathogens were
not isolated from pooled tissues, including heart, these findings are of
unknown significance.

Lung:

Hemorrhage, considered to be due to extraction, was seen in the
lungs of all birds. Lymphocytic accumulations, mild to marked, were
present about primary bronchi in all chicks.

E1125:
No significant changes were observed in the livers of control birds.

No changes were noted in the livers of zinc-deficient chicks from

-22-

   

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Skeletal muscle

B

Figure 6: A, Skeletal muscle from a normal chicken.

Note small individualized fibers with num-
X 650, H. 8: E. stain.

from a zinc-toxic chicken.
erous deep staining nuclei.

-23-

replicates one and two. Slight fatty changes were noted in one of the
birds on replicate three (Figure 7).

Marked fatty change, confirmed by Sudan IV stain, was observed in
the livers of birds fed toxic levels of zinc. Fat was uniformly dispersed
throughout liver tissue (Figure 7).

m:

The Spleens of control birds appeared more congested than did the
spleens of the zinc-deficient and zinc-toxic chicks. Spleens of the
zinc-toxic chicks were very small and had little blood present.
Pancreas:

Pancreatic tissue was considered normal in control birds other
than for lympho—follicular reactions which were marked in one bird
from replicate three. Normal pancreatic tissue is shown in Figure 8.

There was an apparent increase in the number of islets of
Langerhans in zinc-deficient birds. Little chromatin material was
present in the cells of the islets (Figure 8).

The pancreatic tissue of birds on toxic levels of zinc appeared
quite degenerative. Outlines of acini were hazy as cells appeared
individualized. Cellular swelling, hydropic change and some hyaline
degeneration were noted. Few distinguishable islets of Langerhans were
seen (Figure 8).

Duodenum:

Duodenal lymphocytic accumulations were observed in all groups of
chicks. Although primarily diffuse, occasional follicular accumulations
were seen. These findings appeared most severe in the control birds in
replicate three and least severe in the zinc-deficient birds in replicate

three.

 

Figure 7: A, Liver from a zinc-toxic chicken showing fatty change.
X 550. H- &-E. stain. B, Liver from a zinc-toxic chicken showing fatty
change. X 650, Sudan IV stain. C, Liver from a zinc-deficient chicken
containing vacuoles, but essentially normal. X 650, H. & E. stain.

 

Figure 8: A, Pancreas from a normal chicken. B, Pancreas from a zinc-
deficient chicken showing loss of chromatin within the cells of the
islets of Langerhans. C, Pancreas from a zinc-toxic chicken showing
hyaline change. X 650, H. & E. stain.

.0)

-26-

Kidney, Adrenal, Testis and Brain:

No significant lesions were noted in any treatmentlgroup.

-27-

DISCUSSION
Zinc Deficiency

Suppression of growth, ragged feathering and dermatosis were
observed in chicks fed zinc-deficient diets. These changes were
also noted by O'Dell and Savage (13), O'Dell £3 31. (14), Roberson and
Schaible (l9), and Roberson (17). The bone changes described by these
workers were not observed in this study.

Differential leucocyte counts of birds on zinc-deficient diets
were normal in replicates one and two. The drop in lymphocyte count
in replicate three could be due to (a) some factor completely unrelated
to the zinc deficiency, or (b) the direct effects of zinc deficiency.
O’Dell gt _a_l_. (14) report that lymphoid tissues of (the thymus and bursa
of Fabricius were atrophic in chicks on zinc—deficient diets. These
tissues were not examined in this study, but other tissues, i.e. liver,
pancreas, spleen, intestines and lungs from birds on replicate three,
revealed less diffuse and follicular lymphocytic accumulations than did
tissues from control birds on replicate three. These findings suggest
that the normal or pathological presence or absence of lymphocytes in
blood and other tissues may be influenced by zinc deficiency.

The microscopic skin changes observed in this study were more
severe than those described by O'Dell 33 El: (14). This is most likely
due to the fact that skin from the foot was examined in this study, and
it would.be expected that trauma would aggravate lesions. Changes
observed were typical of hyperkeratosis, whereas zinc deficiency in swine
is characterized by parakeratosis (4).

Skeletal muscle fibers were somewhat smaller in cross section than

those of controls, but this was considered to be due to suppressed growth.

-23-

Pancreatic changes were characterized by an apparent increase in
the number of islets of Langerhans and loss of chromatin within the
cells of the islets. These changes are similar to those seen by
O'Dell‘gt‘al.(l4).

Zinc Tbxicity

Severe growth depression and mortality were produced in this
study by 5,016 ppm of zinc. Pensack and Klussendorf (l6), and
Roberson (17), have reported that poor growth is characteristic in chicks
when zinc levels in the ration are 3,000 ppm and above. Pensack and
Klussendorf (16) suggested that the poor growth at such levels was due
to reduced feed intake rather than to direct toxic effects. These
workers did not observe any gross anatomical or pathological changes
when levels up to 3,000 ppm of zinc were added to the ration.

This suggests the possibility that chick mortality observed in
this study may have been due to starvation rather than to direct toxic
effects.

The lesions in birds fed high levels of zinc were most apparent in
the liver and pancreas. The severe fatty change seen in the liver re-
affirms the thought that starvation.may have influenced losses. Hyaline
and hydropic changes were in evidence in the pancreas, and few islets of
Langerhans were distinguishable. That these and the liver changes may
have been due to toxicity seems plausible when it is remembered that
liver and pancreas concentrations of zinc increase more markedly than do
concentrations in other tissues when zinc content of diet is increased (8).
Kidney tissue is saturated at a relatively low concentration of dietary
zinc (8) and.may explain why kidney changes were not observed. Likewise,

the lymphocytic shift to more immature forms in the birds on high levels

-2 9-

of zinc suggests that a toxic effect might be present.
Individual muscle fibers did not appear degenerate but were
small in cross section, individualized and had numerous deeply

staining nuclei.

It is considered that changes seen are due to a combination of

starvation and toxicity.

-30-

SUMMARY

White Rock, male, broiler chicks were maintained on zinc-deficient
(16 ppm), zinc-adequate (36 ppm), and zinc-toxic (5,016 ppm), diets
for periods of 10, 17 and 31 days. Environmental sources of zinc were
eliminated by coating cages with plastic and by supplying distilled
water in glass waterers for drinking purposes.

Symptoms of zinc deficiency were impaired.growth rate, poor
feathering and dermatitis. Differential leucocyte counts revealed a
drOp in numbers of lymphocytes. iMicroscopic manifestations were hyper-
keratosis of the skin, an apparent increased number of islets of
Langerhans in the pancreas accompanied by loss of chromatin in the cells
of the islets, and reduced amounts of lymphoid tissue.

Zinc toxicity was characterized by poor growth and complete
mortality within 31 days. Lesions observed in birds were fatty changes
in the liver, and hydropic and hyaline changes in the pancreas. Differen-
tial leucocyte counts revealed a predominance of immature cells in the
lymphocytic series. These manifestations are considered to be due to

the combined effects of toxicity and starvation.

9.

10.

11.

12.

13.

14.

-31-

REFERENCES CITED

Brink, M. E., D. E. Becker, S. W. Terrill and.H. H. Jensen. Zinc
Toxicosis in the Weanling Pig. J. Ani. Sci., 11 (1958): 1186.

EWards, H. M., Jr., R. J. Young and M. B. Gillis. Studies on
Zinc in Poultry Nutrition. I. The Effect of Feed, water and
Environment on Zinc Deficiency in Chicks. Poultry Sci., _31
(1958): 1094.

Hanson, L. S., and D. K. Sorensen. As cited in Dunne, H. W.:
Diseases of Shrine. Iowa State College Press, Ames (1958): 650.

Kernkamp, H. C. H. and E. F. Ferrin. Parakeratosis in Swine.
J. A. V. M. A., .123 (1953): 217.

Klussendorf, R. C.: Zinc: In Parakeratosis and in Health. Vet.
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Klussendorf, R. C. and J. M. Pensack. Newer Aspects of Zinc
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Lewis, P. K., Jr., W. G. Hoekstra, R. H. Grmmner and P. H. Phillips.
The Effect of Certain Nutritional Factors Including Calcium,
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Lewis, P. K., Jr., W. G. Hoekstra and R. H. Grurmner. Restricted
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Luecke, R. W., J. A. Hoefer, W. S. Brammell and D. A. Schmidt.
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Mehring, A. L., Jr., J. H. Brumbaugh and H. W. Titus. A
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Morrison, F. 8.: Feeds and Feeding. The Morrison Publishing
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O’Dell, B. L., and J. E. Savage. Symptoms of Zinc Deficiency in
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-32-

Pensack, J. M., J. N. Hensen and P. D. Bogonoff. The Effect
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Pensack, J. M., and R. C. Klussendorf. Newer Aspects of Zinc
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Roberson, R. N.: The Role of Zinc in Poultry Nutrition. Doctoral
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Roberson, R. N., P. J. Schaible and.K. E. Johnson. The Removal
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Roberson, R. N., and P. J. Schaible. The Zinc Requirement of the
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Slinger, S. J., J. D. Summers and'W. F Pepper. Effect of Zinc on
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Sturkie, P. D.: The Effects of Excess Zinc on water Consumption in
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Supplee, W. C., G. F. Combs and.D. L. Blamberg. Zinc and Potassium
Effects on Bone Formation, Feathering and Growth of Poults. Poultry
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Todd,'W. H., C. A. Elvehjem and E. B. Hart. Zinc in the Nutrition
of the Rat. Am. J. Physiol., 107 (1934): 146.

Tucker, H. F., and W. D. Salmon. Parakeratosis or Zinc Deficiency
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Young, R. J., H. M. Edwards, Jr. and M. B. Gillis. Studies on Zinc
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(1958): 1100.

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Thesis
Hall, Charles Franklin
Zinc deficiency and zinc
toxicity in growing chickens.

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