THE EFFECT OF ENVIRONMENTAL LIGHT AND
TEMPERATURE ON THE THYROID SECRETION

RATE AND OTHER PHYSIOLOGICAL
PROCESSES IN SHEEP

Thesis for Hm Degree of pl‘l. D.
MICHIGAN STATE UNIVERSITY
Theodore Matthew Hoersch
1960

0-169

This is to certify that the
thesis entitled

THE EFFECT OF ENVIRONMENTAL LIGHT AND
TEMPERATURE ON THE THYROID SECRETION RATE
AND OTHER PHYSIOLOGICAL PROCESSES IN SHEEP

presented by

Theodore Matthew Hoersch

has been accepted towards fulfillment
of the requirements for

Ph. D. degree in Animal Husbandry

Major professor

Sept. 23, 1960
Date

 

LIBRARY

Michigan State
University

 

THE EFFECT OF ENVIRONMENTAL LIGHT AND TEMPERATURE
ON THE THYROID SECRETION RATE
AND OTHER PHYSIOLOGICAL PROCESSES IN SHEEP

by

Theodore Matthew Hoerech

AN ABSTRACT

Submitted to the School for Advanced Graduate Studies of
Michigan State University of Agriculture and
Applied Science in partial fulfillment of
the requirements for the degree of

DOCTOR OF PHILOSOPHY

Department of Animal Husbandry‘

1960

Approved _ _x;::jI2ILégIL;:Z;£;E2szzqz<2722 _______

ABSTRACT T. M. Hoersch

Quantitative measures of the thyroid secretion
rate were Obtained on 64 ewes using the thyroxine substi-
tution method. These animals were maintained under con-
trolled conditions of light and temperature. There were
six variants in light exposure ranging from 4 through 24
hours per day and two temperatures, 50° and 90° F. Each
of the 12 trials lasted 50 days.

Decreasing the ambient temperature from 90° F. to
50° F. induced a three-fold increase in the thyroid se-
cretion rate, which was significant (P< .01).

Increasing the hours of light in increments of 4
hours produced a biphasic effect within the range 4
through 24 hours per day. Differences between the highest
and lowest values were significant (P<:.Ol). By increas-
ing the illumination from 4 hours daily to 12, thyroid
activity was progressively depressed, but with added
light above 12 hours the thyroid secretion rate steadily
rose. The highest values were obtained under continuous
light and the parabolic pattern was in evidence under
both 50° and 90° F. temperatures.

151

The zero time percent uptake of I was increased
by the elevated ambient temperature and increasing the

hours of daily illumination significantly (P<:.Ol)

ABSTRACT T. M. Hoersch

depressed the uptake of radioiodine. A significant nega-
tive correlation of -.255 existed between the thyroid
secretion rate and zero time percent uptake; but the se-
cretion rate could not be significantly related to 1151
output half-time (Th).

Ten individual comparisons were made between the
thyroid secretion rate and thyroid epithelial cell height
in ewes maintained under 12 hours of light. There was a
positive relationship (r a .580, P<:.08) between these
two measures of thyroid activity.‘ The acinar cell heights.
of ewes subjected to the 50° F. temperature were signifi-
cantly (P< .01) greater than those kept at 90° F.

An augmented secretion by the thyroid gland was
associated with increased gains in body weight and im-
proved feed efficiency.

Body weight gains and feed efficiency were Signi-
ficantly improved at the 50° F. temperature as compared
to the warmer (90° F.) environment; but temperature had
no effect on feed consumption. A 12:12 light to dark
ratio was most conducive to rapid gains.

Water consumption was stimulated by the higher
ambient temperature and within temperatures it paralleled
feed consumptibn. Thyroid activity had no effect on

water intake.

ABSTRACT T. M. Hoersch

Both respiratory rate and rectal body temperatures
were significantly (P<Z.Ol) elevated by the increased
ambient temperature and these two measures were signifi-
cantly correlated (r . .391, P<:.Ol). There was a ten-
dency for both respiration rates and rectal body tempera-
tures to decrease with increasing hours of light to 12
hours and then increase with increasing illumination to
24 hours.

A ratio of 16 hours light to 8 hours darkness in-
hibited the estrous cycle in some ewes during the normal
breeding season. Temperature had no significant effect
on the cessation of the estrual periods in this investi-
gation.

Estrus was not induced during the normal anestrous
season by a 16 hour darkness to 8 hour light ratio at

either 50° F. or 90° F.

THE EFFECT OF ENVIRONMENTAL LIGHT AND TEMPERATURE
ON THE THYROID SECRETION RATE
AND OTHER PHYSIOLOGICAL PROCESSES IN SHEEP

by

Theodore Matthew Hoersch

A THESIS

submitted to the School for Advanced Graduate Studies of
Michigan State University of Agriculture and
Applied Science in partial fulfillment of
the requirements for the degree of

DOCTOR OF PHILOSOPHY

Department of Animal Husbandry

1960

6/5744
b/[f/(p/

 

ACKNOWLEDGEMENTS

The author wishes to express his gratitude to Dr.

H. W. Newland, under whose guidance this program was com-
pleted, for his advice, encouragement and help. With equal
appreciation thanks is extended to Dr. H. A. Henneman, who
was most instrumental in designing this experiment and
under whose supervision this work was initiated.

The writer considers himself privileged to have had
the Opportunity to associate with such a gentleman and
scientist as Dr. E. P. Reineke. His physical efforts,
direction, and inspiration during the entire course of
this study will long be remembered. ‘

Thanks and acknowledgement are due Drs. Lois Calhoun
and D. E. Ullrey for their advice concerning the histologi-
cal aspects of this work and their critical reading of the
manuscript. Also appreciation is extended to Dr. W. T.'
Magee for his invaluable aid in assisting with the statis-
tical analyses.

Sincere gratitude is expressed to Mrs. Mary Hillman
for her careful efforts in typing the final manuscript and
to Mrs. Betty Brazier for her preparation of the initial
cOpy. Thanks are also due Lee Bell, shepherd, and his
assistants, Jack Matthews and Larry Cotton, for their help

with the sheep.

The financial aid in the form of an assistantship,
facilities and materials provided by Michigan State Uni-
versity were all greatly appreciated.

The author is eSpecially indebted to his wife,
children, parents and relatives, for it was their help,
sacrifices and encouragement which made this study possi-

ble.

Theodore Matthew Hoersch

candidate for the degree of

Doctor of PhiIOSOphy
Final examination: September 16, 1960, 101 Anthony Hall

Dissertation: The Effect of Environmental Light and
Temperature on the Thyroid Secretion Rate
and Other Physiological Processes in Sheep

Outline of Studies:
Major subject: Animal Husbandry
Minor subjects: Physiology, Anatomy

Biographical Items:
Born, July 8, 1955, Detroit, Michigan
Undergraduate Studies, Michigan State Uni-
versity, 1953-1957
Graduate Studies, Michigan State Univer-
sity, 1958-1960

Experience: Graduate Assistant, Michigan State University,
1958-1960 ‘
Member of Alpha Gamma Rho, Alpha Zeta, and
Phi Kappa Phi

TABLE OF CONTENTS

I. INTRODUCTION . . . . . . . . . . . . . . . . .
II. OBJECTIVES . . . . . . . . . . . . . . . . . .
III. REVIEW OF LITERATURE . . . . . . . . . . . . .
IV. MATERIALS AND METHODS . . . . . . . . . . . .

A.
B.
C.
D.
E.
F.

Chambers . . . . . . . . . . . . . . . .
Animals . . . . . . . . . . . . . . . . .
Feed and Water. . . . . . . . . . . . . .
Thyroid Activity Measurements . . . . . .
Breeding Data . . . . . . . . . . . . . .
Other Physiological Information . . . . .

V. RESULTS AND DISCUSSION . . . . . . . . . . . .

A.

B.

C.

D.

E.

F.

G.

Thyroid Secretion Rate as Affected by
Ambient Temperature and Artificial Light.

The Effect of Ambient Temperature and
Artificial Light on Zero Time Percent Up-
take Of 1151. O O O O O O O O O O O O O O

The Effect of Ambient Timperature and
Artificial Light on 113 Output Half-time

TH). . . . . . . . . . . . . . . . . . .

The Effect of Ambient Temperature on
Thyroid Epithelial Cell Height and Its
Relationship to Other Thyroid Measures. .

A

 

Body Weight Gains as Affected by Ambient
Temperature and Artificial Light. . . . .

Feed Consumption as Affected by Ambient
Temperature and Artificial Light. . . . .

Feed Efficiencg as Affected by Ambient
Temperature an Artificial Light. . . . .

Page

28
28
29
51
32
35
56

37

57

45

52

56

65

68

H.

I.

J.

K.

L.

TABLE OF CONTENTS (Continued)
Page

Water Consumption as Affected by Ambient
Temperature and Artificial Light. . . . . 70

Respiration Rate as Affected by Ambient
Temperature and Artificial Light. . . . . 75

Rectal Temperature as Affected by Ambient
Temperature and Artificial Light. . . . . 75

The Influence of Ambient Temperature and
Artificial Light on the Cessation of the
Breeding Season in Ewes . . . . . . . . . 78

The Influence Of Ambient Temperature and
Artificial Light on the Induction Of Es-
trus in Ewes. . . . . . . . . . . . . . . 81

VI. SUMMARY AND CONCLUSIONS . . . . . . . . . . . 84
VII . BIBLIOGMI O O O O O O O C O O O O O O O O O 89
VIII. “PMDIX 0 CI 0 O O O O O O O O O O O O O O O O 100

TABLE

II

III

IV

VII

VIII

IX

XI

XII

XIII

XIV

 

LIST OF TABLES

DescriptionOfSheep.... see. 0000

Effect of Ambient Temperature and Artificial
Light on Thyroid Secretion Rate in Sheep . .

Effect Of Ambient Temperature and Artifiiial
Light on Zero Time Percent Uptake of I 3 . .

Correlation Coefficients Between Thyroid
Secretion Rate and Zero Time Percent Uptake.

Comparisons Between Zero Time Percent Uptake
Values Obtained by Henderson (1958) and the
Present Study. I O O O O O O O O O O O O O 0

Effect of igpient Temperature and Artificial
Light on I Output Half-time (TH). . . . .

Correlation Coefficiigis Between Thyroid
Secretion Rate and I Output Half-time

()eeoeooeeeoeeeeeeeeee

Effect Of Ambient Temperature on Histologi-
cal and Isotopic Measures of Thyroid Activ-
ity and Relationships Between Measurements .

Effect of Ambient Temperature and Artificial
Light on may Weight Gain-8 e e e e e e e e 0

Correlation Coefficients Between Thyroid
Secretion Rate and Body Weight Gains . . . .

Correlation Coefficients Between Zero Time
Percent Uptake and Body Weight Gains . . . .

Effect of Ambient Temperature and Artificial
Light on Feed Consumption. . . . . . . . . .

Effect of Ambient Temperature and Artificial
Light on Feed Efficiency . . . . . . . . . .

Effect of Ambient Temperature and Artificial
Light On Water Consumption . . . . . . . . .

Page

30

58

46

SO

51

55

55

57

62

66

69

71

LIST OF TABLES (Continued)
TABLE Page

XV Effect of Ambient Temperature and Artifi-
cial Light on Respiration Rate . . . . . . 73

XVI Effect of Ambient Temperature and Artifi-
cial Light on Rectal Temperature . . . . . 76

Figure

LIST OF FIGURES
Page

Effect of Ambient Temperature and Artifi-
cial Light On Thyroid Secretion Rate . . . 41

Effect of Ambient Temperature and Artifi-
gig} Light on Zero Time Percent Uptake Of

O O O O O O O O O O O O O O O O O O O 49

Inhibitory Effects Of 16 Hours Light Per
Day and Two Ambient Temperatures on the
Cessation of the Breeding Season in Ewes . 80

APPENDIX

A

B

LIST OF APPENDICES

Thyroid Secretion Rates at Various Tem-
perature and Light Conditions . . . . . .

Zero Time Percent Uptake at Various Light
Conditions and 50° F. Temperature . . . .

Zero Time Percent Uptake at various Light
Conditions and 90° F. Temperature . . . .

1131 Output Half-time (TH) at Various
Light Conditions and 50° F. Temperature .

1131 Output Half-time (TM) at Various
Light Conditions and 90° F. Temperature .

Thirty Day Body Weight Gains at Various
Light Conditions and 50° F. Temperature .

Thirty Day Body Weight Gains at Various
Light Conditions and 90° F. Temperature .

Feed Consumption Values at Various Light
Conditions and 50° F. Temperature . . . .

Feed Consumption Values at Various Light
Conditions and 90° F. Temperature . . . .

Feed Efficiency Indices at Various Light
Conditions and 50° F. Temperature . . . .

Feed Efficiency Indices at Various Light
Conditions and 90° F. Temperature . . . .

Water Consumption Values at Various Light
Conditions and 50° F. Temperature . . . .

Water Consumption values at Various Light
Conditions and 90° F. Temperature . . . .

Respiration Rates at Various Light Condi-
tions and 50° F. Temperature . . . . . .

Respiration Rates at Various Light Condi-
tions and 90° F. Temperature . . . . . .

Page

101

105

106

107

108

109

110

111

112

115

114

115

116

117

118

LIST OF APPENDICES (Continued)
APPENDIX Page

P Rectal Body Temperatures at Various Light
' Conditions and 50° F. Temperature . . . . 119

Q Rectal Body Temperatures at Various Light
Conditions and 90° F. Temperature . . . . 120

 

I. INTRODUCTION

During the last 65 years much attention has been
focused on the thyroid in an attempt to determine and
regulate the activity of the gland. It has been estab-
lished that the thyroid influences approximately 40% of
the metabolism of warm-blooded animals and may indirectly
affect reproduction, as well as many other functions.

It has become apparent that if practical applica-
tion is to be made of thyroactive substances the physio-
lOgical dose-rate must be established. With this end in
mind Henneman 2;,gl. (1952, 1955) develOped a method for
quantitatively ascertaining the daily secretion of thyroid
hormone.

Previous research has indicated that thyroid ac-
tivity in several species varies with season. While the
effect of increased temperature as a thyroid suppressing
agent has been fairly well elucidated, the literature is
scant and confusing in regard to the effect of light on
thyroid activity. Interactions between light and temper-
ature further complicate research when both components
are exerting an effect as is the case under normal condi—
tions.

In this eXperiment both light and temperature have

been controlled in an attempt to assess the effect on

-1...

thyroid activity due to each. Furthermore, an endeavor
was made to express the results in quantitatively useful
terms, namely milligrams of thyroid hormone secreted per
day.

Numerous workers have considered other indices of
thyroid activity, such as thyroid acinar cell height,
1131 uptake and output, to be valid measures of thyroid
activity. Therefore, efforts have been made in this study
to relate these measurements to thyroid secretion within
individual sheep.

Since previous work has suggested that temperature
and light play a role in the initiation and termination
of the sheep's breeding season the effects of these two
factors on the estrual pattern have also been investi-
gated.

The general objective of this study was to provide
greater basic understanding of the effects of light and
temperature on thyroid activity and the relation of this
activity to traits of economic importance. In the future
it may be possible to select for the desired state of
thyroid activity and to exploit the gland for greater

economic production.

II. OBJECTIVES

1. To investigate the effects Of ambient temperature and
artificial light on the thyroid activity of ewes as
evaluated by:

a. Thyroid secretion rate
151

131

b. Uptake of I
c. Output of I
d. Thyroid epithelial cell height
2. To investigate the effects of ambient temperature and
artificial light on:
a. Body weight gains
b. Feed consumption
c. Water consumption
d. Feed efficiency
e. Respiration rate
f. Rectal temperature
g. Induction of estrus
h. Cessation of the cycling period
5. To correlate various measures of thyroid activity with

each other and with other physiolOgical responses.

III. REVIEW OF LITERATURE

As early as 1895 Magnus-Levy noted that oxidative
metabolism was stimulated by the administration of desic-
cated thyroid. Later Mdrch (1929) described a standard
method for assaying thyroidal materials by measuring the
carbon dioxide production of white mice to which thyroid
preparations had been administered. Subsequently Teitel-
baum and Harne (1941) described a closed circuit respiro-
meter in which oxygen consumption could be read directly.

With these methods it was possible to record in-
creases in metabolism due to the administration of thy-
roidal materials, but it remained for Dempsey and Astwood
(1945) to develop a procedure for quantitatively measur-
ing the daily secretion of thyroid hormone. These workers
fed an antithyroid drug which enlarged the gland. They
then injected thyroxine to reduce the hyperplasia induced
by the goitrogen. The thyroid secretion rate was con-
sidered that level where the injected hormone reduced the
gland size to normal. The main problem with this method
was that it involved sacrificing the animal.

Mixner g3 g1. (1944) described a biological assay
using a modification of this procedure. These workers
fed 0.1 percent thiouracil or thiourea to young chicks

for fourteen days and then injected increasing levels of

- 4 -

5

thyroxine to reduce gland size. In describing their tech-
nique the workers also reported that there was a difference
in thyroid hormone secretion due to breed and sex.

With the advent Of radioactive iodine Perry (1951)

measured the rate of loss of 1151

from the thyroid gland
of the rat and found it was markedly inhibited by thyroxine
administration. Conversely, when thyrotrOpic hormone ex-
tracts were injected he noted a tremendous outpouring of
radioiodine from the gland.

The findings of Wolff (1951) supported Perry's re-
search. The former noted that hypophysectomy lengthened

the biological half-life of 1131

in rats as did 15 micro-
grams of thyroxine per day. Also he, too, reported that
thyrotropin stimulated 1151 release. It is of interest to
note that this researcher found that large doses of iodide
failed to accelerate the release of previously injected
1131. This is important because it lends support to the
concept that there is not a direct relationship between
uptake and output as assumed by some workers.

Henneman 23 gl. (1952, 1955) were the first to de-
scribe a method for quantitatively determining the thyroid
secretion rate in intact animals. These workers injected
graded dosages of 1-thyroxine into sheep previously in-
jected with 1131. When the thyroxine level prevented fur-
ther output of radioiodine from the gland this was con-

sidered to be the thyroid secretion rate.

This method has also been extended to rats by
Reineke and Singh (1955), dairy cattle by Lewis 23 gl.
(1955). mice by Amin 22 Rio (1957). piss by Frape 2’9. 21-
(1958), goats by Flafiboe and Reineke (1959), chickens by
Mellen and Wentworth (1959), mink by Reineke 25 3;. (1960)
and rainbow trout by Hoffert (1959).

Reineke (1959) has recently shown thyroid secretion
to be rather constant in several species of animals when
expressed as micrograms of thyroxine per kilogram of body
weight to the 0.73 Power.

While thyroid secretion rate estimates are considered
valid measures of thyroid activity, a relatively long
period of time is required for their execution. For this
reason much interest has been generated in recent years
in uptake and output tests.

Werner g§,gl. (1949) have described a 24-hour uptake
test for the purpose of studying normal and disordered
thyroid function in man. These workers state that normal
uptake at 24 hours lies somewhere between 10 and 40 per-
cent of the administered dose.

In regard to uptake it should be recognized that in
clinical procedures involving thyroid disease a high up-
take is associated with an active gland; whereas, with
normal domestic and laboratory animals a low uptake is

usually found to be associated with high thyroid activity.

Reineke g2 El. (1956) working with inbred and F1
hybrid mice reported a low uptake and a rapid output was
accompanied by an elevated thyroid secretion rate. Chai
g§_§;. (1957) reporting on the same study indicated that
there were differences in uptake and output between dif-
ferent strains and the F1 hybrids were intermediate in
thyroid activity between the two parent strains. Amin 33
£1. (1957) also found that thyroid secretion rates of the
hybrid mice were somewhere between their inbred parents.
These studies are significant because they indicate that
it may be possible to select for thyroid activity since
it may be controlled under a given set of conditions by
genetic factors.

Freinkel and Lewis (1957) observed that half-time
turnovers for shorn sheep were shorter than in unshorn
sheep, but no difference was found in circulating protein-
bound iodine (PBI) values.

Henderson (1958) maintained sheep under controlled
conditions of light and temperature and found an inverse
relationship between maximum percent uptake and turnover
rate.

Lodge 25 gl. (1958) reported an inverse relationship
between thyroid secretion rate and 48 hour uptake in dairy
calves. The same workers concluded that uptake was high-

est in the summer and lowest in the spring.

Seidell and Fenger (1915) Observed that beef, sheep
and hOg thyroids had the highest iodine content in August
and September. The sheep thyroids were lowest in iodine
and largest in size during April and May. These two
workers also stated that the glands contained about three
times as much iodine from June to November as between
December and May.

Kendall and Simonsen (1928) also noted this increase
in iodine content in the summer. The peak of iodine con-
centration was reached in July and declined to a low in
January. They, like their predecessors, reported a 500
percent difference in total iodine due to the seasonal
effect.

Zalesky (1955) observed that the thyroid gland of the
thirteen-lined ground squirrel followed a seaSonal pattern
as evaluated by histometric assays. During hibernation
the gland was relatively quiescent, but in periods of
activity, such as pregnancy, thyroid activity was markedly
stimulated.

Reineke and Turner (1945) using the goitrogen techni-
que for measuring thyroid secretion in 2-week old chicks
reported that thyroid activity was lowest in March and
rose in October and November. Later Turner (1948) noted

a decline in thyroid activity in leghorn hens in May.

9

Brody (1945) has plotted the metabolism in Cal./24
hours of a castrate male sheep over a period Of four years.
It can be observed that metabolism reaches a peak in May
and declines to a low in August and September. The same
author has reported that resting metabolism in goats is
highest in February and falls in the summer. Reports of
thyroid activity which parallel these seasonal patterns
in metabolism have recently been described.

Henneman 93 gl. (1955) noted that thyroid secretion
in ewes reached a peak in March and declined to a low in
July. Griffin (1955) found the same pattern in rams.

Premachandra g; g1. (1957) observed that thyroid
secretion rates in cattle were highest in December to
April and lowest during May through September. Lodge gg
El. (1958) have since reported that values for thyroxine
secretion in cattle are higher in May than in August-
September.

Flamboe and Reineke (1959) found that the thyroid
secretion rate of dairy goats declines to a lower level in
July than during the remainder of the year.

Since the turn of the century there have been numer-
ous attempts to elucidate the factors responsible for the
seasonal rhythms in metabolism and thyroid activity. The
pattern is usually attributed to seasonal changes in tem-

perature and light.

lO

Cramer (1916) observed that when animals were exposed
to cold the colloid in the thyroid vesicles became dimin—
ished and the acinar cells were enlarged.

Mills (1918) wrote that high external temperature re-
duced thyroid activity as evaluated by morphology and rate
of growth. He also noted that low temperatures increased
thyroid activity and accelerated growth.

Skoog (1959) noted the alterations in the histology
of the thyroid gland imposed by heat and cold. He reported
that animals maintained in a cold room had epithelial cells
three times as tall as controls kept at normal room tem-
perature. On the other hand, heat depressed the Size of
the parenchymal cells and also the gland size.

Zalesky and Wells (1940) confirmed the finding that
low environmental temperature stimulates thyroid size.
Working with the ground squirrel they Observed a signifi-
cant increase in thyroid weights in both males and females
due to decreased temperature.

Dempsey and Searles (1945) reported that temperatures
of 95° F. reduced follicle cell size and increased colloid
storage, while cold (55° F.) increased cell height.

Dempsey and Astwood (1945) using their then newly described
goitrogen technique found that thyroid secretion was stim-

ulated by reduced environmental temperature.

11

Hurst and Turner (1948) concluded that lowering the
environmental temperature increased the thyroid secretion
rate in mice.

While Catz 23 gl. (1955) found that temperature had
little or no effect on the uptake of radioiodine by rats,
they did observe that decreased temperature stimulated
thyroid epithelial cell height.

Blincoe and Brody (1955) reported that temperatures

or above 95° F. depressed thyroid uptake of 1131

in Jersey,
Brown Swiss, Holstein and Brahman cattle. Later Blincoe
(1958) observed that some breeds of cattle were more
tolerant than others with regard to the effect of heat on
thyroid activity. Eighty degree F. temperature depressed
the thyroid activity of Shorthorns by 45 percent as judged
by 1151 uptake, but Santa Gertrudis cattle were affected
only slightly and Brahmans not at all.

Brown-Grant (1956) studied the effects of moderate
chilling on thyroidal radioiodine Output in rats and ob-
served that the rate of release was stimulated by cold
exposure within eight hours. Acute exposure to severe
cold resulted in either no change or a reduced rate.

Henderson (1958) using the same environmental cham-
bers as reported in this study concluded that, within the
range 50° to 90° F., decreasing ambient temperatures stim-
ulated thyroid epithelial cell height, thyroid secretion

151

rate, and I release but had no effect on zero timelnmake.

12

Knigge and Bierman (1958) have Shown that the central
nervous system is involved in the cold-induced release of
thyroidal I131. These workers found that the hamster's
thyroidal radioiodine release is accelerated within twelve
hours by a temperature of 5° C., but after hypOphysectomy
the release cannot be stimulated by cold.

While it is fairly well established that high tempera-
tures suppress thyroid activity and cold stimulates the
gland the effect of increased or decreased light has not
been satisfactorily resolved. This may be due, in part,
to the fact that the majority of the experiments conducted
along this line have been carried out using either complete
light or darkness. Few researchers have actually increased
or decreased the light in small increments over a wide
range of light-to-dark ratios.

Kenyon (1955) and Mayerson (1955) agreed that they
could find no hypertrOphy or colloid loss in rats main-
tained under complete darkness. Dempsey and Searles (1945)
observed that continuous light reduced thyroid epithelial
cell height, but when female rats were exposed to both
continuous light and constant refrigeration they had in-
creased thyroid acinar cell heights.

Stein and Carpenter (1945) using the salamander and
red newt as experimental animals reported that added arti-

ficial illumination (17 hours per day - 6 days per week)

13

resulted in taller acinar epithelium in the treated animals
than in controls. ,

Kleinpeter and Mixner (1947) found that the thyroid
secretion rate Of two week old male baby chicks was in-
creased from 10.7 - 20.8 percent in chicks maintained
under constant light as compared with controls, which re-
ceived 12 hours of light. These workers also reported
that quality of light had no effect.

Puntriano and Meites (1951) reported that continuous
light was responsible for reduced thyroid weight, reaction
to thiouracil and thyroid uptake of I151. Opposite results
were described for mice subjected to complete darkness.

Terry (1951) observed a higher uptake of I151 i

n
ewes under continuous darkness than in those under com-
plete light. The results of these last two experiments
are hard to interpret since a high uptake in normal do-
mestic animals is usually associated with an inactive
thyroid.

Henderson (1958) reported that ewes under twelve
hours of artificial light had increased thyroid activity
as measured by uptake and output rate as compared to ewes
maintained at 8 and 16 hours light. Opposite results were
obtained when the thyroid activity was assessed by histo-

logical cell height determinations.

14

It has been established that the thyroid gland in-
fluences approximately 40 percent of the resting metabo-
lism of an animal. Therefore, under a given set of physi-
ological conditions, indices such as respiration rate and
rectal temperature theoretically would appear to be mani-
festations of thyroid activity. Furthermore, it is of
the utmost importance to the animal husbandman to maintain
his animals under the most favorable conditions of light
and temperature in order to exploit their inherent utili-
tarian characteristics.

Lee gt g1. (1945) observed that air temperatures
up to 85° F. have no effect on the physiological responses
of chickens. At 90° F. rectal temperature rose from O.5°
to 1.0° F. and respiration rate increased by 5 per minute.

Breed differences in adaptability of Sheep to high
atmOSpheric temperatures have been noted by Miller and
Monge (1946). Suffolk and Rambouillet ewes had lower
respiration rates than did Southdown and Hampshire ewes.
There was a close agreement between breeding, growth and
health records of various breed groups with the efficiency
of heat disposal.

Robinson and Lee (1947) reported that animals on a
high plane of nutrition exhibited increased rectal temper-

atures and respiratory rates when exposed to hot conditions

15

as compared to animals on a lower nutritional plane.

Heitman and Hughes (1949) noted that increased
ambient air temperature caused increased body temperature
and increased respiratory rates in swine. Feed consump-
tion tended to vary inversely with air temperature. Rate
and efficiency of gain.was found to be highest in swine
weighing 70-144 pounds at 75° F., but as the weight of the
hogs increased the Optimum temperature decreased to 60° F.
Heitman gt El. (1951) later reported that water consumption
was also depressed by increased ambient temperature.

Newland g§,§l. (1952) found that body temperatures
of newborn pigs dropped sharply during the first 50 min-
utes after birth and returned to normal within 2 days.

The decline in body temperature was inversely related to
both birth weight and environmental temperature.

Ragsdale 33 51. (1949) observed that water consump-
tion in dairy cattle tended to parallel feed consumption,
but at temperatures above 80° F. the water intake in-
creased with increasing temperatures. These authors con-
cluded that the Optimal temperature zone for quantity and
efficiency of milk production appeared to be around 50° F.

Kibler and Brody (1949) noted in dairy cattle that
rectal temperatures increased as a result of increasing
air temperatures from 50° to 100° F. This was accompanied

by a progressive increase in respiration to more than four

16

times the rate at 50° F., but heat production was reduced
by 20-50 percent at temperatures above 70° F., associated
with decreasing feed consumption and thyroid activity.

Reik 33 gl. (1950) found a sharp rise in respiration
rates in sheep following exposure to temperatures of 50-45°
C. for seven hours. Corriedales had the greatest respira-
tory volume, but the Merinos respired faster. Sheep on an
extremely high plane of nutrition were less tolerant of
heat than those on a medium level. An extremely low diet-
ary level interfered. with heat regulation.

Kibler and Brody (1951) concluded that Brown Swiss
had a higher reapiration rate than Brahman cattle within
the temperature range, 40-105° F. Below 90° F. the rectal
temperatures of all groups were constant. Heat production
as measured in calories per hour declined with increasing
air temperature.

Ragsdale 23 gl. (1951) concluded that the critical
air temperature for Brown Swiss cattle appeared to be 85°
F. Temperatures above this level depressed feed consump-
tion with consequent loss of body weight. The same authors
(1955) reported that relative humidity had no effect on
feed and water consumption at temperatures less than 75°
F. At high humidities, accompanying temperatures of above
75° F., water and feed consumption was inhibited.

McDowell 23 El. (1955) working with Jersey and Sindhi-

Jersey crossbred cows Observed that the crossbreds showed

17

a smaller rise in rectal temperature than did Jerseys

when exposed to temperatures of 105° F. They reported
that respiration rate was not as effective an index of
heat tolerance as respiratory volume and could find no
Significant correlation between rectal temperature and
respiratory rate.

Fletcher and Reid (1955) maintained three groups of
sheep: control, clipped on the back, and shorn. These
researchers noted that shorn lambs had a lower respiration
rate and rectal temperature than did unshorn or clipped.

Casady gg’gl. (l956)1nne reported that correlations
were higher between chamber temperatures of 60, 70, 80,
85, 90 and 95 degrees and respiratory rate, rump skin
temperature and scrotal skin temperature in young bulls
than correlations between rectal temperature and the same
responses. Respiration rateswere most closely associated
with rectal temperatures at chamber temperatures of 80-90°
F.

Foote 33 gl. (1957) found highly significant differ-
ences in rectal temperatures of rams maintained at ambient
temperatures of 79, 82 and 95° F. Rectal temperatures
were 102.56, 102.91 and 104.50 degrees for the respective
groups.

Kibler (1957) noted that Shorthorns grown at 80° F.

experienced constant physical stress as evidenced by

18

rectal temperatures of 104° F. and respiration rates of

90 per minute. Brahmans produced the least heat and were
most tolerant to heat. Santa Gertrudis, a breed which
descended from a cross of the two named breeds, were inter-
mediate in all respects.

Appleman and Delouche (1958) reported that decreas-
ing temperatures from 20° C. to 0° 0. resulted in a Slight
decrease in water consumption in goats. This was accom-
panied by a 1° F. drop in rectal temperature and a small
suppression of the respiratory rate. Conversely, increas-
ing ambient temperature from 20° to 40° C. resulted in
increased water consumption, increased rectal temperature
and a marked increase in respiration rate.

Brody g§,§l. (1954) observed that in cattle there
was a tendency for feed consumption and body weight.to
increase with increased light to 90 BTU/ft.2/hour and
then to decline. Water consumption increased with in-
creasing light. |

Kibler and Brody (1954) observed that respiration
rates increased in Holstein and Brahman cows with increas-
ing intensity of radiation when the temperature was main-
tained at 45° F. At this temperature rectal temperatures
remained normal, but when the ambient temperature was
raised to 70° F., rectal temperatures rose to 5.5 to 4°

F. above normal.

19

It is recognized that the thyroid gland plays an
important role in many of life's physiological processes.
Many attempts have been made to manipulate the gland, but
the results are inconsistent possibly because the level of
administration of thyroid stimulating or depressing ma-
terials has not been within physiological limits.

Reineke and McMillan (1946) reported that thyro-
protein feeding was effective in correcting poor milk pro-
duction in sows when given at the rate of .005 percent of
the ration. This finding was confirmed by Johnson 23 gl.
(1959) who reported that baby pig gains were stimulated
up to five weeks of age by supplementing the sow's ration
with thyr0protein.

Beeson 33 gl. (1947) observed that feeding thyro-
protein at the level of .0088 percent of the ration to
pigs resulted in faster gains and better feed efficiency
than controls. These workers found thiouracil feeding at
0.1 percent Of the diet retarded growth, reduced feed in-
take and caused pigs to become short and chuffy.

Peo and Hudman (1960) noted increased gains of 18
percent and increased feed efficiency of 9 percent when
early-weaned pigs were fed therprotein at levels of 10
to 40 milligrams per pound of ration.

Blaxter 33 gl. (1949) have reviewed the subject of

feeding thyroidal materials and synthetic goitrOgens.

20

These authors conclude that iodinated protein increases
growth rate in pigs, but the results in beef cattle and
sheep are inconsistent because of the diversity of en-
vironmental conditions.

Singh 33 gl. (1956) reported that ewes with a faster
output of iodine from the thyroid tended to produce faster
gaining twin lambs to three weeks of age. They also found
a correlation of +.8l between thyroid secretion rate and
lamb growth.

Godfrey and Tribe (1959) indicated that wool growth
was stimulated by thyroxine implants when the Sheep were
on a restricted diet.

Burroughs g§,gl. (1960) observed increased gains of
15 percent in beef cattle when methimazole (Tapazole),

a goitrOgen, was fed at the rate of 600 milligrams per
day for 55 to 56 days. Feed efficiency was improved by
15 percent, but feed consumption was not influenced by
methimazole feeding.

Hurst and Turner (1948) concluded that thiouracil
feeding decreased the rate of growth of mice. This was
confirmed by Maqsood and Reineke (1950) who also stated
that hyperthyroidism induced by therprotein feeding
stimulated weight gains in young mice.

Grosvenor and Turner (1958) injected 5 micrograms

of thyroxine per 100 grams of body weight per day into

21

rats and reported that milk production was improved by
57.7 percent.

The role that the thyroid gland plays in the scheme
of reproduction has long been a matter of scientific in-
vestigation.

The results of Van Dyke and Ch’en (1955) indicated
that the concentration of the pituitary hormone triggering
ovulation was reduced when rabbits were thyroidectomized.

Reineke 25 gl. (1941) reported that the pituitaries
of young male goats, which had previously been thyroid-
ectomized, had a low concentration of gonadotrOpins. Also
a lack of stimulation was apparent in the testes.

Petersen 23 31. (1941) found that thyroidectomy re-
sulted in complete absence of libido in bulls, but the
artificially collected semen was normal in all respects
and produced pregnancies.

Bogart and Mayer (1946) reported that all symptoms
of summer sterility in rams were alleviated by the adminis—
tration of thyroxine or thyroactive substances with the
exception of lowered volume and motility. They suggested
that increased heat suppressed thyroid function which in
turn was responsible for the inhibition of sperm produc-
tion.

Eaton 23 gl. (1948), Warwick §§,gl. (1948) and
Black 22 El. (1950) all indicated that thyroprotein had

22

no effect on ram fertility. At high levels of feeding
therprotein had a deleterious effect on semen quality.

Meites and Chandrashaker (1948) induced both hyper-
thyroidism and hypothyroidism in rats and mice by feeding
thyroprotein and thiouracil. They concluded that a hypo-
thyroid condition is advantageous for gonadal function in
rats, but a hyperthyroid condition is conducive to in-
creased gonadal activity in mice.

Maqsood (1950) reported that mild hyperthyroidism
stimulated spermatogenesis and increased the activity of
the Leydig cells in mice, rabbits and rams. He further
wrote that thyroxine treatment improved libido in the ram
and thyroidectomy or thiouracil treatment interferred with
spermatogenesis and resulted in an abnormal appearance of
the interstitial cells.

Further information was presented by Oloufa g§_gl.
(1951) who found thyroprotein was beneficial in male rab-
bits for alleviating harmful effects due to intermittent
high temperatures. They found that continuous high tem-
perature was more detrimental to fertility than intermit-
tant heat and concluded that the effect was mediated in-
directly through the thyroid.

Reineke and Soliman (1955) have extensively reviewed
the literature in regard to the role of the thyroid hor-

mone in reproductive physiology Of the female. They

25

conclude that there is a delicate balance between the
ovary, pituitary and thyroid. Any imbalance between
these organs may be manifested by sexual irregularities
and a hyperthyroid condition favors ovulation.

Soliman and Reineke (1954) found a significant in-
crease in the 6 hour uptake of radioiodine in female rats
during estrus. The same authors (1954) noted a cyclic
variation in the uptake test which could be related to
the estrual cycle. The following year (1955) they ob-
served that estrogen administration in ovariectomized

rats promoted increased uptake of I131

by the thyroid.

Moon and Turner (1960) later duplicated this experiment
using the thyroid secretion rate estimate and obtained

the same results.

While it is of academic interest to elucidate the
factors responsible for seasonal breeding habits in all
animals it is a matter of economic importance to the
sheep raiser. To what extent seasonal light and tempera-
ture influence the thyroid gland which in turn affects
the gonads is still a matter of conjecture. It is well
established that ewes begin to come into estrus in the

northern hemisphere when the days become shorter and the

temperature starts to decline.

Rowan (1925) concluded that gradual increments of
increased light stimulated gonadal activity in Junco

starlings.

24

Bissonnette (1952) reported that female ferrets sub-
jected to an extra 6—6.5 hours of light exhibited estrus
between October and January while controls underwent no
change. Marshall (1940) working with the same specie in-
dicated that the acceleration of the estrus cycle was cor-
related with the degree of light intensity. Irradiated
females stOpped cycling soon after being placed with the
males, probably as a result of c0pu1ation, but pregnancy
did not ensue. No explanation was Offered for the failure
of the females to become pregnant.

Hart (1950) also investigated photOperiodicity in
the female ferret and reported that estrus is effected by
a contrast sensitive mechanism which is stimulated by the
light: dark ratio, not the total light. He further stated
that in the ferret the ratio Should be two parts light to
one part darkness to induce estrus. Doubling the number
of light-dark contrast periods from one every 24 hours to
two per 24 hours does not materially accelerate estrus as
compared to the one contrast period. -

Hammond (1944) indicated that the breeding season
of sheep is evenly spaced on either side of the shortest
day of the year. Furthermore, cycling begins later in
those ewes younger than 500 days. _

Sykes and Cole (1944) were successful in getting 5

out of 8 ewes to lamb in November when they first graduaxbr

25

increased light until 5 additional hours of daylight were
added in March. Then they decreased the illumination,
through May to the point where the experimental animals
were receiving 6 hours less daylight than normally existed.

Yeates (1949, 1955) reported that the onset of the
breeding season is a response to decreasing light and oc-
curs 15 to 16 weeks after the change from increasing to
decreasing light. The estrous periods stop 14 to 19 weeks
after the change over. Neither candle power nor tempera-
ture had an effect on the onset or continuation of estrus.

Hart (1950) found that in sheep, as in ferrets, it
was not necessary to decrease the light gradually, but a
ratio of one part light to two parts darkness was neces-
sary to induce estrus. Ewes in deep anestrum were harder
to bring into heat than animals that had just gone out of
heat.

Hafez (1950) noted that there was a relationship
between the duration of the breeding season and the lati-
tude and altitude of origin of the breed. The same author
(1951) Observed that ewes under continuous light stOpped
cycling in 12 weeks.

Hafez (1952) later reported that transferring sheep
from one latitude to another within the same hemisphere
influenced the ovarian rhythm. When be exposed ewes to

8 hours of light and 16 hours of dark the breeding season

 

26

was hastened by 57 days, but it took from 10—25 weeks to
accomplish this end. Cessation of the breeding season was
hastened by 15 weeks by 16 hours of light and 8 hours dark,
but 6 to 24 weeks were required for the complete stOppage
of cycling activity.

Means 93 gl. (1959) were only partially successful
in inducing estrus by regulating the light. While these
workers were able to initiate an early (late summer)
breeding season in Western ewes less success was encount-
ered in Southdowns. Ten hours of light in the spring
tended to induce estrus in approximately one half the ex-
perimental animals but conception was poor.

Mercier and Salisbury (1947a) concluded that the
hours of daylight influence the fertility level in cattle
and the response is dependent on the age of the animal.
YOung bulls were found to be most fertile in the winter
while the older bulls were least fertile during the
shorter days. Reporting in another article (1947b) they
found the lowest percent successful services in winter
and spring. The monthly conception rate was related to
the average length of daylight, but a time lag of 1-2
months existed.

McKenzie and Phillips (1955) Observed that tempera-
ture had no effect on the length of time required for
ewes to come into-heat. These workers maintained ewes in

an iced cellar during the first part of August.

 

 

27

Dutt and Bush (1955) noted that ewes placed in a
cold chamber (45-48° F.) came into estrus 8 weeks earlier
than controls. Semen from rams placed in the chamber
failed to Show the marked decline in motility or percent
abnormal cells usually encountered in the summer.

Dutt 23 £1. (1956, 1959) reported that high environ-
mental temperature (90° F.) reduced the conception rate Of
ewes and increased the incidence of abnormal ova.

Casady (1955) found that initial motility, sperm
concentration and total sperm all declined when dairy
bulls were exposed to high ambient temperature. He did
find, however, that sexual libido was unaffected in the

same bulls.

IV. MATERIALS AND METHODS

A. Chambers.

Two environmental chambers were used in this study;
one was maintained at 50° F. by refrigeration while the
other was heated to 90° F. The cold room was constructed
of insulated masonite and was 10 feet wide, 20 feet long
and 12 feet high. While the relative humidity was not
recorded in this experiment, Hendefson (1958) reported a
range of 76 to 84 percent relative humidity in this same
chamber the previous year with temperatures Of 50° and
55° F-

The hot room was of brick construction and measured
20 feet wide, 26 feet long and 16 feet high. Henderson
(1958) Observed that the relative humidity in this chamber
varied from 60 to 70 percent.

In both chambers light was regulated by an electric
time switch. Each light treatment was tested at both 50°
and 90° F. temperatures. Four 500 watt bulbs were sus-
pended 8 feet from the floor in the cold room and 6 bulbs
of the same wattage hung 16 feet above the floor in the
hot chamber. Light treatments consisted of 4, 8, 12, 16,
20 and 24 hours of artificial illumination and sheep were
never exposed to natural daylight while on experiment.

With the exception of the continuous light treatment the

_ 28 _

29

lights went on twice a day for equal time periods in order
to feed, water and Obtain data on the sheep. Therefore,
there were two light-dark contrast periods in each of the
light treatments, 4 through 20 hours.

Sheep were individually penned in order to measure
each ewe's feed and water consumption. The pens were 5 by
6 and 5 by 8 feet in the cold and hot rooms respectively.
Sheep in the cold room were bedded with straw, but in the
hot chamber the pens were not bedded, but cleaned once a
day with running water Since previous work had shown the

bedding became too wet and leppy.

B. Animals.

The 71 sheep used in these experiments were ewe
lambs showing a preponderance of mutton breeding. A
description of the age, breed and weight of the experi-
mental sheep is given in Table 1.

In the original plan of this experiment it was de-
sired to investigate the effects of 50° and 90° F. tem-
peratures, as well as light, on breeding behavior. Since
Hart (1950) and Hafez (1952) had purportedly already es-
tablished that a ratio of one part light to two parts
dark induced early estrus the more pertinent concern was
the consequence of temperature differences. Therefore,
it appeared important to keep the light at an equivalent

level for both hot and cold groups and experiment on the

5O

.maompo Haw QH obaoEp ems mpdeumonp smog ma an moss do>oam .mmsonw
A.m com com .m oomv endpwhomsop can ease emew>fld hawmbo macaw pmwaa mowm .

 

ohannaonem see saoaeem oo\mH\a HH as.ee e a em

mpowbmmo momma
whopmom N onflnwmamm

 

enohmoa a saoaasm om\m \oa m nm.mm a a om
cannomaamo mm\o \0H dd oo.moa a a ma

damper; N Onwmmmonmw
neopaoa.x aaoeesm mm\oa\o mus ma.ao e = NH

onwmmmonnm
schemes searched mmxa \m ma me.mmH e = w
schemaoeo one saoaaam mm\ua\aa m oe.sm .pnmaa teach a
mQHOOon pnosflnmdxm do nausea a“ owd meadom cutaneous

cooeam Open OpesHNonmmw .pz .><

 

 

macaw mo noepmwnomon
H wands

51

same breed of sheep during an identical time of year. For
this reason the effect of breed on other physiological data
is confounded with the light treatments.

The 8, 12 and 24 hour groups were Shorn immediately
before being placed in the chambers, while the other
groups, with the exception of three Cheviots - maintained
at 20 hours of light and 50° F., had been shorn earlier
in the season. Therefore, it was not considered necessary

to shear them again.

0. Feed and Water.

All sheep were fed ad libitgm a pelleted mixture
consisting of 4 parts sun cured alfalfa meal and one part
ground yellow corn by weight. Dicalcium phosphate, trace
mineral salt, vitamins A and D, and aureomycin were like-
wise incorporated into this pellet. Also, free choice
iodized salt was available to insure adequate iodine in-
take.

The literature is quite confusing in regard to the
effect of feeding iodized salt to animals on a thyroid
experiment. Swanson 32 gl. (1957) reported that iodine
in amounts usually incorporated into dairy rations inhib-
ited uptake of radioiodine by cattle while an extremely
low level of iodine intake also inhibited 1151 uptake.
INadler and Leblond (1958) Observed the rate at which iodine

32

is retained in the rat's thyroid gland for organic binding.
They indicated that this rate is not dependent on dietary
iodine providing the iodine intake ranged from 1 to 7.5
micrograms per gram of body weight.

Water was available at all times for the ewes in the
hot chamber, but since the water was found to condense on
the refrigeration coils, it was offered only twice a day

to the sheep in the cold room.

D. Thygoid Activity Measurements.

In all of the 12 light and temperature treatments
the sheep were allowed seven days to become acclimated to
the chambers. At the end of the seven days all but the
groups on 8 hours of light were subcutaneously injected
with 100 microcuries of 1151. Since the eight hour group
averaged 155.75 Pounds in weight they were administered
125 microcuries instead of the usual one hundred.

Seven days were permitted for maximum uptake and
counts were taken on days 7, 10 and 15 postwinjection.
Immediately following the 15 day count, daily l-thyroxine
injections were begun. A given amount was administered
for 6 consecutive days and a count was taken every third
day. Then the quantity of injected hormone was doubled

and given at this rate for 6 more days, again recording

two counts. This procedure was followed in all but the

53

continuous light groups. After the output rate informa-
tion had been obtained in these groups thyroxine injec-
tions were begun as before; but in an attempt to refine
the technique injections were increased by only 50 percent
every third day. This procedure provided 5 levels of
thyroxine administration instead of the customary three.

The technique of Henneman 2g g1. (1952, 1955) was
followed for both external 1151 counting and for calculat-
ing the thyroid secretion rate.

The_l-thyroxine used for the first eight experiments
was the same as used by the Henneman group in develOping
the thyroid secretion method seven years previous to the
start of this study. It had been furnished by Glaxo
Laboratories, Greenford, Middlesex, England. For the last
four trials (4 and 24 hour groups) the l—thyroxine was in-
directly supplied by the same firm, but was Obtained from
Merck & Co., Inc., Rahway, New Jersey.

The thyroxine was weighed, dissolved in distilled
water, made slightly basic with NaOH and then acidified
with HCL. New batches of the hormone were prepared at the
start of each experiment and were kept refrigerated through—
out the injection period.

All counts were made with a scintillation counter
(Nuclear Chicago, model DS-l) and a count rate meter

(Nuclear Chicago, model 1620). Duplicate standards of

54

one-tenth the injected dose were made up at the time of
injection and any day-to-day differences in machine count-
ing or geometry could be detected in the count of the
standards. Conventional corrections were made for physi—
cal decay and background.

For zero time percent uptake studies the first
three counts were converted to logs and a regression line
calculated. Where the line of regression crossed the zero
time axis the antilog of this number was determined. This
parameter (counts per minute) was then divided by the
decay-corrected standard count and expressed as the the—
oretical zero time percent uptake.

For output rate studies T% was computed as that
length Of time required for the thyroid to lose one-half
of its theoretical zero time radio-activity.

The thyroid glands were removed from the 12 hour
light groups after 1151 uptake, output, thyroid secretion
rate and other physiological information had been collected.
The glands were then fixed in Bouin's fluid, sectioned in
paraffin and stained with Harris’hematoxylin and eosin.

A modification of the procedure of Rawson and Starr
(1958) was used for assessing the height of the thyroid
epithelium. Twenty distinct acinar cells in each gland
were measured. An eye piece was inserted in a micrOSCOpe

and calibrated by means of a Leitz echelon micrometer.

35

With the oil immersion lens one division of the eye piece

was equal to 0.9 micra.

E. Breeding Data.
In the fall of 1958 the ewes were checked under

natural conditions with a vasectomized ram in order to
verify that all were cycling. After each sheep had ex-
hibited at least one estrous period they were placed in
the environmental chambers. Lights were then regulated so
as to be on for 16 hours per day in both hot and cold cham-
bers. The vasectomized ram was maintained in the cold
chamber and was allowed to check each ewe separately twice
each day for heat.

In the spring of 1959 a vasectomized ram was placed
twice a day with a group of ewes in order to detect any
irregular cycling. When none was Observed after approxi-
mately three weeks the ewes were moved into the experi-
mental chambers. For this study the lights were set to
come on for 8 hours a day in an attempt to induce early
estrus.

The ewes in this study were then checked twice daily
with a fertile ram which was kept in the 50° F. chamber
during the course of the study. On May 28, 1959, the
cold room ewes were turned loose with the ram. At this

time the ewes in the hot room were also released from

56

'their individual pens, but it was feared that a constant
temperature of 90° F. might be detrimental to the fertility
of a ram. For this reason these hot room ewes were checked

twice a day with the ram maintained in the 50° F. chamber.

F. QEhggPhysiological Information.

Individual changes in weight, feed consumption and
water intake were all recorded for a thirty day period
while the thyroid data collections were in progress.

During this span of time 10 rectal temperature read-
ings and 10 respiration rate determinations were compiled
on each ewe. These measurements were all recorded at ap-

proximately 5 m1. 1 1 hour.

V. RESULTS AND DISCUSSION

A. Thyroid Secretiqp Rate as Affected by Ambient Tempera-
ture and Artificial Light.
The thyroid secretion rate was taken as that point
where the level of l-thyroxine injection prevented further

output of 1151

by the thyroid gland and 100 percent of the
previous count was obtained. This technique was first re-
ported by Henneman 23 gl. (1952).

In this study after 100 percent of the previous
count was obtained further counts were disregarded. Also
when the calculations revealed that a subsequent count ex-
ceeded a previous count this was considered only 100 per-
cent--the difference was regarded as counting error and
not a recycling phenomenon.

As there was a three-fold difference in the weight
of the heaviest ewe as compared to the lightest, the
thyroid secretion rate results were expressed as milli-
grams of thyroxine per kilogram of body weight to the
0.75 power as suggested by Reineke (1959).

_ Thyroid secretion rate information is reported for
64 of the 65 values obtained in this experiment. One
ewe's secretion rate was well over three times the next
highest animal's thyroid hormone production. This value
Was far more than two standard deviations away from the

mean of all the other values and therefore was not

- 57 -

38

considered to be a representative.measurement.

The effects of ambient temperature and artificial
light on thyroid secretion are presented in table 2.
Analysis of variance revealed that there were significant
differences which could be attributed to both light and

temperature.

TABLE II

Effect of Ambient Temperature and Artificial
Light on Thyroid Secretion Rate in Sheep'

 

Hours of Ambient Tem erature
Light 505 F. , 906 g. Average

 

 

4 .0058 i .0018"(5)X .0020 I .0005 (5) .0059

8 .0055 i .0010 (5) .0027 i .0007 (5) .0040

12 .0059 i .0009 (6) .0011 I .0002 (5) .0026

16 .0055 i .0009 (5) .0014 i .0004 (5) .0056

20 .0056 i .0017 (5) .0021 1 .0009 (6) .0058

24 .0089 i .0015 (6) .0028 i .0005 (6) .0059ab
Average .0058a .0020

 

‘ Values are expressed as milligrams of l-thyroxine se-
creted per kilogram of body weight to the 0.75 power.

*‘ Mean 1 standard error of the estimate.

Figures in parentheses indicate number of animals from

which mean was derived.

Significantly different EP<:.01; from least value.

Significantly different P< .05 from two least values.

0‘89

59

Ewes maintained at 50° F. had a significantly higher
(P<i.01) secretion rate than the 90° F. groups. By in-
specting the temperature averages of table 2 it can be
observed there was approximately a three-fold decrease as
a result of the higher ambient temperature.

These results agree with those of Dempsey and
Astwood (1945) and Hurst and Turner (1948). Both groups
employed the goitrogen technique for determining the
thyroid secretion rate in rats and mice, respectively,
and concluded that decreased environmental temperature
stimulated thyroid function.

While the results in this eXperiment are reported in
relation to body weight to the 0.75 power they are in
close agreement with thyroid secretion rates obtained by
Henderson (1958) under identical conditions. He reported
his values as milligrams of thyroxine secreted per 100
pounds of body weight and only under eight hours of light.

When the thyroid secretion rate information in the
present study is expressed in those terms and only the
eight hour light groups considered, the results compare as
follows: 50° F.--Henderson, .122; present study, .080.
90° F.--Henderson, .055; present study, .041. Further-
more, the earlier worker has included one value in the
50° F. group which was well over twice as high as the

second largest value. If this estimate is neglected

40

the outcome (.105, .080) is even more compatible.

This indicates that under the same environmental
conditions year to year estimates of thyroid activity, as
evaluated by the thyroid secretion rate technique, will
lie within a similar range.

Increasing the levels of artificial light in incre-
ments of 4 hours produced a biphasic effect. Starting
with 4 hours of light per day and increasing the level to
12 hours suppressed the thyroid secretion rate, but with
increasing light beyond 12 hours thyroid function was
stimulated. The results are graphically depicted in
figure 1.

The differences were significant (P< .05) when sub-
jected to analysis of variance. A studentized range test
was performed on the light treatment means and it indicated
that the 24 hour groups had a significantly (P<:.01)
higher secretion rate than the 12 hour treatments. Also,
the ewes in continuous light were secreting significantly
(P<I.05) more thyroid hormone than the sheep maintained
at both 12 and 16 hours of light.

There was no significant interaction between light
and temperature. In this and all other analyses reported
in this study statistical procedures are taken from

Snedecor (1956) .

Figure 1. Effect of Ambient Temperature and Artificial
Light on Thyroid Secretion Rate.

41

 

 

 

 

 

 

9
n
.'o 50' F
x ,31
90' F
.‘3 J
o‘ 7

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

    

 

4 8 I2 I6 20 24
HOURS OF LIGHT

DAILY MG. mnoxmt-z/ no. 300v WEIGHT
9!

 

42

It is of interest to note that 11 out of the 12 in-
dividual treatment means followed the parabolic pattern.
Only the 4 hour-90° F. average appeared to deviate from
the overall scheme. Judging from the other parameters
this value appears too low.

The symmetry of the 50 degree temperature groups,
increasing or decreasing by 8 hours on either side of the
12 hour average, is worthy of consideration. Here, the
effect of increased or decreased illumination on thyroid
activity appears equivalent. Based on the results of
this experiment constant light markedly stimulated thyroid
secretion. It would be of great academic interest to as-
certain the effect of complete darkness on the sheep's
thyroid secretion; but this was not considered feasible
in this study as the chambers had to be entered and illu-
minated for a minimum of an hour a day.

This study is in agreement with the reports of
Kleinpeter and Mixner (1947) who measured the thyroid se-
cretion rate of chicks by the goitrogen method and noted
a stimulatory effect by increasing light from 12 hours to
24 hours per day.

The results of this experiment offer a plausible
explanation for the previously reported spring peaks in

seasonal thyroid activity and metabolism.

43

Brody (1945) noted that energy metabolism in sheep-
reaches a summit in May and then declines sharply during
the summer. A similar rhythm in thyroid secretion of
ewes was reported by Henneman 23 Q1. (1955). This group
observed that the secretion rate increased to a maximum
in March and ultimately dr0pped to a low during July.
These findings have been confirmed in cattle by Lodge gp
3;. (1957) who found thyroid secretion values higher in
May than in August-September. Similar reports have been
published by Premachandra gt g1. (1957, 1958). Flamboe
and Reineke (1959) have also observed the same seasonal
phenomena in goats, but without the extreme peak in the
spring.

From the data of this and other experiments it may
generally be concluded that the increasing temperature
from March through August is a factor which tends to de-
press thyroid activity. Likewise, the declining tempera-
ture from September through February would serve to stimu-
late the action of the gland.

Considering June 21 to be the longest day of the
year and daylight steadily decreasing to December 21, the
light component would synergise with increasing air tem-
perature to depress thyroid function in the summer. This
assumption is based on the data obtained in this study
that decreasing the light to 12 hours per day inhibits

thyroid hormone production.

44

Following the decrease in length of day to intervals
less than 12 hours (September-October); this, accompanied
by colder temperatures, would stimulate thyroid activity.
Again, the theory is supported by the evidence acquired in
this investigation that decreasing the hours of light from
12 hours to 4 hours per day augments secretion by the
thyroid gland.

Activity of the gland should theoretically remain
at a constant level during the winter because of the two
opposing forces of decreasing temperature and increasing
light after December 21. The lowered temperature would
have a stimulatory consequence while the increased illu-
mination up to 12 hours in late winter would have a de-
pressing effect.

The spring crest in metabolism and thyroid activity,
heretofore, has never been adequately explained. It can-
not be a function of temperature since it is becoming
progressively warmer during the spring and this tends to
inhibit the above two faculties.

The author suggests that the increasing increment
of light beyond 12 hours in early spring is the agent re-
sponsible for the peak in thyroid secretion, which in turn

stimulates metabolism.

45

B. The Effect of Ambient Tegperature and Artificial Light

on Zero Time Percent Uptake of 1151.

 

Previous to the start of l—thyroxine injections
described in section A, three counts, unaffected by the
hormone administration, were taken on days 7, 10 and 15

after 1131

injection. Using the log of these counts a
regression line was calculated and mathematically extra-
polated back to the zero time axis.

Duplicate aliquot standards were counted at the same
distance from the scintillation tube as were the sheep's
thyroid glands. After correcting the standards back to
zero time, the theoretical zero time thyroid count was di-
vided by the standard. The results are, therefore, ex-
pressed as percent of standard.

This study was conducted to measure only the rela-
tive accumulation of radioiodine and not the rate of up-
take. Henderson (1958) had previously shown maximum
uptake in ewes on approximately day 4 post-injection.
Therefore, in this study all counts were taken on the
output side of the uptake-output curve.

The mean values for zero time percent uptake are
shown in table 5.

Analysis of variance revealed a significant differ-

ence (P<L.05) in uptake which could be attributed to the

temperature treatments. The 90° F. ewes accumulated more

TABLE III

Effect of Ambient Temperature and Artificial
Light on Zero Time Percent Uptake of I 5 *

46

 

 

Hours of Ambient Tem erature
Light 555 F. 90' F.

 

 

Average
4 21.62 i 4.75"(5)‘x 24.17 i 2.70 (4) 22.75b
8 26.01 I 2.94 (6) 27.66 I 2.77 (6) 26.84ab
12 17.04 t 1.16 (6) 22.41 I 4.88 (6) 19.75c
16 10.48 I 1.91 (5) 19.11 I 2.75 (5) 14.79
20 8.82 i 1.77 (4) 12.65 I 2.85 (5) 10.94
24 12.06 I 0.98 (6) 10.65 I 0.96 (6) 11.55
Average 16.45 19.56(1 “

 

Hoe

which mean was derived.

Significantly different
Significantly different
Significantly different

900‘”

P<
(P<

EP<

Values are expressed as zero time percent of standard.
Mean 1 standard error of the estimate.
Figures in parentheses indicate number of animals from

Significantly different (P<f.05 from 4 least values.
.01 from 5 least values.
.01 from 2 least values.

.05 from least value.

1151 than the 50° F. groups. In accord with the conclu-
sions of Reineke 23 gl. (1956), Henderson (1958), Lodge

23,31. (1958) and Flamboe and Reineke (1959),in this study

a low uptake appears to indicate a rapidly functioning

gland.

While there existed a three-fold difference in

thyroid secretion rate between the two temperature groups,

47

using the uptake measurement there was only a 17 percent
disparity between the same groups of sheep. This result
is not surprising since Henderson (1958) could show no
significant difference in zero time percent uptake due to
any one of four temperatures within the same range as was
used in this study.

Artificial light appeared to have a greater effect on
uptake than did temperature. When the treatments were
subjected to analysis of variance there were significant
differences at the one percent level.

Increasing increments of darkness stimulated uptake
and long exposure to light depressed the accumulation of
1151. Upon observing table 5 it becomes apparent that the
eight hour light groups deviate somewhat from the pattern.
It will be recalled from the description of the sheep in
the procedure that these ewes were older and much heavier
than the other sheep. Consequently, they were injected
with 25 percent more radioiodine than the others.

Whether this group had a higher uptake because they
were older or heavier cannot be ascertained from this ex-
periment. Henneman g3 g1. (1955), Wilansky gg 31. (1957)
and Flamboe and Reineke (1959) agreed that thyroid activ-
ity declines with age in several species. Thus, this high‘
uptake could be a function of age and the elevated uptake

may indicate lowered thyroid function.

48

It seems unlikely that an increased injection dose
would manifest itself in increased percent uptake. The
effects of temperature and light on zero time percent
uptake are graphically shown in figure 2.

The results of the study agree with the data obtained
by Terry (1951) and Puntriano and Meites (1951). Both
groups, the former working with sheep and the latter with
rats, reported that continuous darkness stimulated 1131
uptake and constant light reduéed radioiodine accumulation
by the thyroid.

While the author is in agreement with the data re-
ported by the above two groups,at the same time he tends
to disagree with the conclusions drawn by these workers.
They assumed a high uptake to be a function of an active
gland; Whereas, recent research, Reineke 32,31. (1956),
Henderson (1958), Lodge 23.11. (1958) and Flamboe and
Reineke (1959), has indicated the reverse to be‘true.

Correlation analysis revealed a significant"nega-‘
tive correlation of 4.255 (P< .05) between thyroid secre-
tion rate and zero time percent uptake. This corresponds
quite closely with the figure (r - -O.17) obtained be-
tween the same two measurements reported in cattle by
Lodge 23 31. (1958).

The correlation coefficients obtained within indi-

vidual groups are presented in table 4.

Figure 2.

 

[:1 90¢

 

49

Effect of Ambient Temperature and Artificial Light
on Zero Time Per e U 131

     

 

 

 

I 50'?

 

 

 

 

LIGHT

 

 

 

nouns or

 

 

 

 

 

 

 

28
2

 

0 ob a: do '
N — — *

PERCENT UPTAKE

50

TABLE IV

Correlation Coefficients Between Thyroid Secretion
Rate and Zero Time Percent Uptake

 

 

Ambient Temperature Combined

 

 

 

 

Hogizhgf g0. F9dr“? 30. F. df "%ig§£'df

4 -.724 5 -.670 2 -.685a 7

8 -.287 5 +.526 5 -.259 8

12 -.651 4 -.560 5 —.451 9

16 +.756 5 -.905a 5 -.525 8

20 -. 759 l -.193 3 -.461 6

24 +.575 4 +.062 4 +.402 10
Combined '

temperature -.242 28 -.206 28 -.2558 58

 

‘ Degrees of freedom.
a Probability < . 05 .

While correlations between secretion rate and uptake
tend to be higher within individual groups, only the 90° F.-
16 hour light and combined 4 hour light groups were signi-
ficant. Also it should be noted that 16 of the 21 coeffi-
cients presented in table 4 were negative.

Therefore, it becomes apparent that with a large
number of animals there will be a tendency toward an in-
verse relationship between thyroid secretion rate and
uptake, but uptake in a single animal is not a reliable

estimate of thyroid function.

51

It is of interest to compare the results of zero
time percent uptake obtained by Henderson (1958) with
those obtained in the present study. Only the values
obtained under identieal light and temperature conditions

are presented in table 5.

TABLE V

Comparisons Between Zero Time Percent Uptake Values
Obtained by Henderson (1958) and the Present Study‘

 

 

 

 

 

Hours of Ambient Temperature
Light 50° F. 90° E.
Henderson Present Henderson Present
8 25.52 26.01 12.88 27.66
12 14.63 17.04 9.58 22.41
16 11.95 10.48 16.74 19.11

 

‘ Values reported are averages of six ewes.

While there is a remarkable similarity between the
values acquired at 50° F.; for the most part, there are
two-fold differences between ewe groups maintained at
90° F.

The results of table 5 are quite typical of the pub-
lished literature.

Swanson g; 51. (1957) reported that dairy cattle had
a maximum uptake of 1131 of 18 percent of the dose. The
following year Lodge 23 E1. (1958) noted an average 48

52

hour uptake in the same specie of 56.4 percent. The lowest
value reported by the latter group was 26.7 percent in the
Spring.

In summary, on occasion uptake values can be dupli-
cated from year to year, but under other circumstances the

results are inconsistent.

C. The Effect of Ambient Temperature and Artigicial Light

921151 Output Half-time (3%).

The I151 output half-time was that point on the re-
gression line, described in section B, where the log of
one-half the theoretical zero time radioactivity had dis-
appeared from the thyroid gland.

Since it was desired to obtain thyroid secretion
rate information on the same ewes, only the first three
counts were unaffected by thyroxine injections. From a
statistical point of view it is somewhat dangerous to de-
termine a regression slope with only5 measurements of
thyroid 1151 activity.

The effects of ambient temperature and artificial
light on output half-time are shown in table 6.

Ambient temperature had no significant effect on
output time and the only statistical difference induced
by light was between the 16 and 20 hour values. The 16
hour ewes had a significantly faster (P< .05) output than
the 20 hour groups.

53

TABLE VI

Effect of Ambient Temperature and Artificial .
Light on 1151 Output Half-time (T%)‘

I

 

Hours of Ambient Temperature

 

 

Light 50° F. 90° F. Average
4 15.509 I 2.759%5)x 12.795 1 5.170 (4) 14.191
15.145 I 5.255 (6) 11.149 I 1.127 (6) 15.147
12 9.155 I 1.975 (6) 20.870 I 6.597 (6) 15.002
16 8.060 I 1.704 (5) 7.765 I 0.675 (5) 7.913
20 18.886 I 5.818 (5) 20.567 I 5.554 (5) 19.956a
24 15.078 I 1.856 (6) 16.892 I 1.787 (6) 15.984
Average 15.214 15.197

 

‘ Values are expressed in days.
" Mean i standard error of the estimate.
x Figures in parentheses indicate number of animals from
which mean was derived.
a Significantly different (P< .05) from least value.

The author tends to discount this dissimilarity
sinCe it is inconceivable that a small increase of 4 hours
of added illumination would decrease thyroid activity by
half. This difference appears to be a compound sampling
error of the two adjacent light treatments. Judging from
the other data in table 6 the values obtained at 16 hours
appear to be too low and outputs measured under 20 hours

of light too high.

54

‘There seem to be no real differences as measured by
output produced by either light or temperature. This
agrees with the work of Pipes 23 Q1. (1959) Who concluded
that seasonal variation did not affect T% or turnover rate
in cattle.

A relationship between thyroid secretion rate and

I151

output half-time was almost non-existent (r a .005),
and correlations within groups are non-significant and in-
consistent as can be seen from table 7.

It will be noted that no correlation coefficient
is reported for the 20 hours light-50° F. ewes. This is
because it was possible to obtain meaningful values of
output half-time on only three ewes. One of these had the
thyroid secretion rate which was three times higher than
the next highest ewe's and therefore, as previously re—
ported, this value was not considered valid.

The author attributes much of the counting incon-
sistencies to his own failure to shear the 5 Cheviots
within this group. No particular difficulties were en-
countered in determining a regression slape for the 20
hour-90° F. individuals, which were counted at the same
time and handled in a manner similar to the 50° F. sheep.

The results of table 7 support the findings of
Premachandra 32 a1. (1958) and Flamboe and Reineke (1959).

55

151

Neither group could consistently correlate I output

with thyroid secretion rate.

TABLE‘VII

Correlation Coefficients Between Thyroid Secretion
Rate and 1131 Output Half-time (Th)

 

 

 

 

 

 

Hours of 5émb§ent Tempe§83u§e CO?Ei::d
Light ° ' -————ii———-
r df"T r df r df

4 +.668 5 +.714 2 +.568 7
-.212 5 -.421 5 +.O25 8

12 +.27l 4 +.682 5 -.O98 9
16 -.752 5 +.84l 5 -.259 8
2o ----- "' -0101 3 +0275 5
24 -.555 4 +.286 4 -.555 10

Combined

temperature +.044 27 -.l60 28 +.005 57

 

* Degrees of freedom.

Differences in gland size and the possibility of
1151 sequestering by the thyroid offer logical, but rather
superficial explanations for the incompatibility of the two
measures. In the author's opinion the answer is contin—
gent upon the elucidation of the many biochemical and

genetic factors which ultimately regulate thyroid function.

56

D. The Effect of Ambient Temperature op_Thypoid Epithelia1
Cell Height and Its Relationship to Other Thyroid

Measures.

After all the isotopic and physiological data had
been obtained from the ewes_maintained at 12 hours of
light they were slaughtered. The thyroid glands were re—
moved, fixed in Bouin's fluid and sectioned at 10 micra.
Following staining with Harris' hematoxylin and eosin,
the epithelial cell height of each gland was measured using
a modification of the procedure of Rawson and Starr (1958).

The individual acinar cell heights along with cor-
responding thyroid secretion rates, uptakes and output
half-times are presented in table 8.

As can be seen from the table the 50° F. group had
cell heights approximately 25 percent greater than did the
90° F. group indicating that thyroid activity was markedly
stimulated by the lower environmental temperature. This
is in agreement with the reports of Cramer (1916), Stein
and Carpenter (1945), Dempsey and Searles (1945),

Freinkel and Lewis (1957) and Henderson (1958). All of
these workers observed an increase in cell height which
could be attributed to decreased temperatures.

It is of interest to note that there was no over-
lap of cell height values between the two temperature

groups and the difference between groups was significant

TABLE VIII

Effect of Ambient Temperature on Histological

and Isot0pic Measures of Thyroid Activity
and Relationships Between Measurements‘

57

 

 

 

 

 

Sheep no. Epith. Cell Thy. Secretion Th Zero Time
Height Rate 0 75 (days) Percent
(Micra) TSR/Kg B.W. ‘ Uptake
(ms.)
50° F.
544 9.27“ .0022 5.505 19.60
489 8.14 .0076 6.265 14.44
588 9.18 .0058 17.896 14.62
597 7.85 .0027 8.962 20.48
499 9.45 .0026 5.429 18.72
Average 8.77a .0042a 8.770 17.57
90° F.
565 6.44 .0006 5.751 19.99
459 6.26 .0008 22.962 22.98
557 6.50 .0019 28.554 15.15
555 6.57 .0015 14.095 15.50
540 6.54 .0008 5.816 45.81
Average 6.58 .0011 15.427 25.52
Correlation with cell height .58 -.4O -.55
Level of significance .08 .54 .59

 

‘ A11 ewes maintained under 12 hours of light.
“ Average of 20 measurements.

a Significantly greater (P< .01) than least value.

58

(P< .01). Mean cell heights of the_high temperature group
were very uniform, which might suggest that a critical
temperature had been reached. Possibly the epithelium
cannot be suppressed much beyond this point and remain in
a physiological state.

There is an approximate four-fold difference between
the thyroid secretion rates of the two groups and this
difference is also significant at the one percent level.
The highest correlation (r a .58, P<:.08) was obtained be-
tween thyroid secretion rate and cell height.

While the effect of artificial light on acinar cell
height was not ascertained in this histological study,
Henderson (1958) measured the thyroid epithelium of ewes
under 8, 12, and 16 hours of light. He reported that
thyroid cell height was suppressed by 12 hours of light
and increased with increasing or decreasing light. The
identical trend was obtained in thyroid secretion rate
results in the present experiment with,increasing 4 hour
increments of light from 4 to 24 hours of illumination
daily.

The correlation between cell height and output is
low (r - -.40, P< .54) and there is a probability of
about one out of three that there is no relationship be-
tween the two measures. .The same can be stated of the

correlation between cell height and uptake. The

59

coefficient (r - -.55, P< .59) is lowest and least signifi-
cant of the three comparisons.

While the correlations between thyroid epithelial
cell height and isot0pic measures were computed using only
10 animals, it will be recalled from sections B and C that
correlation coefficients were calculated between thyroid
secretion rate and the other two isotOpe measures using
many animals. There was a low inverse relationship
(r . -.255, P< .05) between secretion rate and uptake and
almost no correlation (r = .005) between the former measure
and output half-time.

The results of these experiments indicate that only
thyroid secretion rate measurements are valid for quanti-
tatively assaying the activity of the thyroid gland in the
intact animal. This is in agreement with the results of
Premachandra pp 11. (1958) and Flamboe and Reineke (1959).
Both groups reported, in essence, that thyroid secretion
rate was the only reliable index of thyroid activity in
the living animal.

These workers did not use histological studies as a
criterion for their conclusions as has been done in these
experiments. The results obtained in this investigation
bear out the statements of the above groups. The present
data indicate that thyroid secretion rate in the intact
animal can be related to the epithelial cell height

measurements obtained post mortem.

60

E. Body Weight Gains as Affected by_Ambient Temperature

and Artificial Light.

In this study the changes in body weight are reported

for a 50 day period. After 7 days were allowed for the

ewes to acclimate to the chambers the initial weights were

taken. This trial was conducted during the same time the

thyroid information was being collected.

presented in table 9.

TABLE IX

The results are

Effect of Ambient Temperature and Artificial Light
on Body Weight Gains‘

 

 

 

Hours of Ambient Temperature
Light 50° F. 90° F. Average
4 8.42 I 2.16"(6)x 0.00 I 1.17 (6) 4.21
9.75 I 2.56 (6) 15.08 I 2.85 (6) 11.42bc
12 16.57 I 1.92 (6) 10.62 I 0.44 (6) 15.50a
16 8.25 I 2.58 (6) 5.90 I 1.26 (5) 6.27
20 7.12 I 2.64 (6) —0.25 I 1.54 (6) 5.44
24 14.04 I 5.80 (6) 7.92 I 1.55 (6) 10.980
Average 10.66d

—_

1.
Mac

which mean was derived.
Significantly different
Significantly different
Significantly different
Significantly different

900‘”

5.95

Values expressed in pounds.
Mean I standard error of the estimate.
Figures in parentheses indicate number of animals from

(P< .01) from least 5 values.
(P< .OSE from least 5 values.

P<'.Ol
(P< .01

from least 2 values.
from least value.

61

The ewes maintained at 50° F. consistently gained
more weight than did the 90° F. groups and this difference
was significant (P<'.Ol). Only the sheep at 8 hours of
light and 90° F. outgained their counterparts kept at
50° F.

These results agree with the reports of Ragsdale
22 a1. (1949, 1951, 1955), Heitman pp Q1. (1951) and
Henderson (1958), who concluded that elevated ambient tem-
peratures depressed gains in dairy cattle, pregnant sows
and ewes, respectively.

There is a tendency for gains to increase with
increasing light to 12 hours and then decrease with
increased light to 20 hours. Unfortunately the cone
stant light groups do not follow this trend. This may be
due to the fact that this set of sheep was in a very thin
condition when placed on experiment. While on a previous
trial, unrelated to this study, they had a tendency to
lose weight. The data obtained in the present study may
have been influenced by the prior treatment.

Many statistically signiIicant differences were
found between the light groups and they are presented in
table 9. The most important observation is that the 12
hour group gained more (P< .01) weight than the three
lowest gaining groups. This agrees with the conclusions

of Brody pp g1.'(l954) who noted that body weight gains

62

in cattle increased with increasing light to 90 BTU/ft.2/
hour and then declined. While no measurements were taken
on radiation intensity in this study, it does appear that
there is an Optimum level of light which is most conducive
to weight gains in sheep.

There was a correlation of .240 between thyroid se-
cretion rate and body weight gains, which approached sig-
nificance (P<:.O6). Correlations within groups are pre-

sented in table 10.

TABLE X

Correlations Coefficients Between Thyroid Secretion
Rate and Body Weight Gains

 

 

 

 

 

Hoggghgf ggbignthemperggurg. Compingd
r df‘ r d? r df
4 -.875 5 -.555 5 -.086 8
+.58? 5 -.l69 5 +.118 8

12 +.105 4 -.520 5 +.482 9

16 -.765 5 +.772 5 +.Ol7 8

20 +.82O 5 +.462 . 4 +.799a 9

24 +.O68 4 -.546 4 +.5l2 lO

Combined

temperature +.O58 5O +.144 5O +.24O 62

 

 

’ Degrees of freedom.
3. Probability< .01.

65

While only the combined 20 hour light correlation
(r a +.799) was significant (P<:.Ol), it will be noted
that under both temperature conditions and 5 out of 6
light treatments positive coefficients were obtained.

This indicates that a mild degree of hyperthyroidism
stimulates weight gains in ewes. This coincides with re-
ports by Reineke and McMillan (1946), Beeson 22 a1. (1947),
Blaxter pp 21. (1949), Johnson pp Q1. (1959) and Peo and
Hudman (1960), who found either direct stimulation of
gains or indirect augmentation through increased milk pro-
duction which resulted from thyroprotein feeding to swine.
Similar results were observed in mice by Maqsood and
Reineke (1950). Although the results of the present
study are not as dramatic as those obtained in lambs by
Singh pp a1. (1956), who reported a correlation of +.8l
between thyroid secretion rate and lamb growth, they do
confirm that a positive relationship between the two fac-
tors does exist.

Correlations between uptake and gains were calculated
to determine whether a relationship did exist. If this
proved to be true it could serve as a useful tool in
selection.

Unfortunately the correlation between all the up-
takes and gains was very small (r a +.O74) and nonsignifi—

cant. The coefficients within groups are shown in table 11.

TABLE XI

Correlation Coefficients Between Zero Time Percent
Uptake and Body Weight Gains

 

 

 

 

 

 

 

H f Ambient temperature Combined
OLIShg 4500 F. 1 90° F. light
8 r df‘ r df r df
4 +.506 5 -.951a 2 +.142 7
12 +.584 4 -.250 4 —.l64 10
20 +0356 2 -0765 3 -0481; 7
24 +.O60 4 +.O40 4 +.l7l 10
Combined
temperature +.l28 5O +.097 5O +.O74 62

 

‘ Degrees of freedom.
a Probability< .05.

Only the coefficient (r = -.951) obtained on the 4
hour light-90° F. group was significant (P< .05). Within
the individual light-temperature groups there was a
tendency for the 90° F. sheep to have a negative correla-
tion coefficient and the 50° F. ewes a positive one. This
is probably a chance sampling phenomenon and it can only
be concluded from the results of this study that zero

time percent uptake and body weight gains are unrelated.

65

F. Feed Consumption as Affected by Ambient Temperature
and Artificial Ligp_.

Feed consumption was measured during the same 50
day period as were gains and thyroid activity measurements.
Since there was a three-fold difference in initial weights
between the heaviest ewe and the lightest, feed intake
was expressed as pounds of feed consumed in 50 days per
kilogram of body weight to the 0.75 power. This computa-
tion was done to adjust the ewes' body weights to a meta-
bolically equivalent weight. Brody (1945) has observed
that maintenance requirements increase with the 0.7} power
of body weight.

The effects of temperature and light on feed con-
sumption are presented in-table l2.

Contrary to most of the published literature, temper-
ature had no effect on feed consumption. Heitman and
Hughes (1949), Kibler and Brody (1949), Maqsood and
Reineke (1950), Ragsdale pp g1. (1951, 1955) and Henderson
(1958) reported that increasing ambient temperatures sup-
pressed feed intake in several species.

This failure to comply with the above reports can-
not be attributed to either the initial state of nutri-
tion or to any one extreme group. Those ewes maintained
at 12 and 24 hours of light could be classified as thin

at the start of the experiment, while the 8 hour sheep

66
TABLE XII

Effect of Ambient Temperature and Artificial Light
on Feed Consumption’

Hours of Ambient Tem erature
Light 506 F. 905 F. Average

 

 

 

 

4 6.15 I .16”(6)X 5.54 I .15 (6) 5.75

8 8.99 I .47 (6) 9.06 I .50 (6) 9.02b

12 10.26 I .55 (6) 11.58 I .62 (6) 10.92a

16 5.51 I .56 (6) 4.06 I .56 (5) 4.74

20 6.15 I .26 (5) 5.12 I .29 (5) 5.62

24 8.58 I .57 (6) 9.60 I .62 (6) 8.99b
Average 7.57 7.62

 

’ Values eXpressed as pounds of feed consumed in 50 days/
Kg. B.W.O°73
” Mean 1 standard error of the estimate.
X Figures in parentheses indicate number of animals from
which mean was derived.
a Significantly different (P< .013 from 5 least values.
b Significantly different P< .01 from 5 least values.

were in a very good condition. All three of these sets of
sheep, under both 50° F. and 90° F., consumed approxi-
mately equivalent amounts of feed. The other three sets
of ewes could be categorized as being in moderate flesh.
It should be pointed out here that these latter sheep had
feed consumption trends in accord with the above litera-
ture--i.e., the 50° F. ewes had greater feed intake than

the 90° F. sheep.

67

Half (5) of the 90° F. groups had greater feed con-
sumption values than their corresponding 50° F. counter-
parts. Again, it should be stressed that all sheep within
a given light treatment (split into two temperature groups)
were of similar breeding, size and age.

The 12 hour light ewes consumed significantly more
(P< .01) feed than all other groups, while the 8 and 24
hour sheeps' intakes were significantly greater (P< .01)
than the 4, l6 and 20 hour light groups.

The pattern in feed consumption under different light
conditions tends to be the same as body weight gains. The
author concludes that the state of nutrition at the be-
ginning of the experiment and breeding of the sheep had a
greater effect on feed consumption than did artificial
light. The sole exceptions may have been the continuous
light groups. These sheep were extremely nervous and while
the ewes did not eat for long periods at any one time,
they were perpetually coming back to consume small quanti-
ties of feed.

Analysis of variance also revealed there was a sig-
nificant (P< .05) interaction between light and tempera-
ture. The 12 hour-90° F. ewes had the greatest feed in-
take and the 16 hour-90° F. sheep the least.

I Considering all the values for thyroid secretion and

feed consumption there was no significant correlation

68

between these measures. The only significant correlation
(r a +.768, P< .05) was obtained on the 20 hour light
ewes when both 50° and 90° F. temperatures were grouped

together.

G. Feed Efficiency as Affected by Ambient Temperature and
Artificial Ligh .

Feed efficiency figures are reported as pounds of
gain per pound of feed consumed per kilogram of body
weight to the 0.75 Power. In this study some of the ewes
lost weight over the 50 day feeding trial. Therefore, the
conventional feed efficiency expression, pounds of feed
consumed per pound of gain, would be misleading and could
not be used statistically. The results are shown in table
15.

Analysis of variance revealed that the 50° F. ewes
were more efficient in converting feed to gain than the
90° F. sheep and this difference was highly significant
(P< .01). While there were no significant differences
induced by light there was a significant (P<:.O5) inter-
action between temperature and light. The most efficient
sheep were those maintained at 24 hours light-50° F. and
the least efficient were the 20 hour-90° F. ewes who
actually lost weight as a group.

Since the data from the previous section indicated

that increased temperature had no effect on feed intake,

69

TABLE XIII

Effect of Ambient Temperature and
Artificial Light on Feed Efficiency‘

 

 

Hours of Ambient Tem erature
Light 353 F. g0: F. Average

 

 

4 1.54 i .32“(6)x 0.05 i .21 (6) 0.70

1.09 i .27 (6) 1.42 i .26 (6) 1.26

12 1.58 I .15 (6) 0.93 i .06 (6) 1.25

16 1.46 i .58 (6) 1.06 I .39 (5) 1.28

20 1.58 I .59 (5) —0.17 I .51 (5) 0.60

24 1.72 I .51 (6) 0.79 I .22 (6) 1.25
Average 1.43a 0.69

 

’ Values expressed as lbs. gain/lb. feed consumed/Kg.
B.w.°-75.
“ Mean 1 standard error of the estimate.
X Figures in parentheses indicate number of animals from
which mean was derived.
a Significantly different (P< .01) from least value.

it can be concluded that thyroid state was a factor in
improving feed efficiency. The sheep at the lower temper-
ature were secreting three times as much thyroid hormone
as the 90° F. ewes. Likewise, the sheep in the cold cham-
ber were twice as efficient in converting feed as the hot
room groups.

This relationship between efficiency of gain and

thyroid secretion rate was statistically supported. There

70

was a significant (P< .05) correlation of +.268 between
the two parameters.

The results of this study agree with Beeson gt gl.
(1947), Blaxter gt 2;. (1949) and Peo and Hudman (1960);
all concluded that a mild hyperthyroid state improved feed
efficiency in swine. Ragsdale 92 al. (1949) reported that
the optimal zone for efficiency of milk production in

dairy cattle appeared to be around 50° F.

H. Water Consumption as Affected by Ambient Temperatugg
and Artificial Ligh_.

The values reported are in terms of pounds of water
consumed during the 50 day trial per kilogram of body
weight to the 0.7} power. Again, as with feed consumption,
an attempt has been made to adjust the weight of all ewes
to a metabolically equivalent weight.

In order to reduce the humidity in the cold room,
water was offered only twice a day, but the ewes in the
hot chamber had access to water at all times. Henderson
(1958) using these same chambers reported that there were
no differences in water consumption which could be attri-
buted to watering twice a day as compared to the ad libi-
tgm method. The results are presented in table 14.

Ewes at 90° F. drank significantly (P< .01) more

water than the sheep at 50° F. This trend was evident in

TABLE XIV

71

Effect of Ambient Temperature and Artificial
Light on Water Consumption‘

 

 

 

 

 

 

Hours of Ambient Temperature g__
Light 506 F. 906‘F. Average
4 15.28 I 1.27m-(6)x 17.57 i 0.68 (6) 15.42
16.25 I 0.70 (6) 22.62 1 1.75 (6) 19.42Cd
12 16.99 i 1.04 (6) 29.82 I 1.87 (6) 25.40ab
16 12.57 1 1.25 (6) 15.54 I 1.65 (5) 15.92
20 10.58 i 0.96 (6) 15.45 i 1.57 (6) 15.01
24 15.88 i 0.75 (6) 22.09 I 2.07 (6) 17.988
Average 13.92 20.65d

 

* Values expressed as pounds of water consumed in 30 days/

Kg. B.W.0-73.

*‘ Mean 1 standard error of the estimate.

N

mean.

Significantly different
Significantly different
Significantly different
Significantly different
Significantly different

(DD-00‘5”

€P<
P<
EP<
p<
(P<

.05
.01
.05
.01
.05

3

i

from
from
from
from
from

Figures in parentheses indicate numbers constituting

4 least values.
3 least values.
2 least values.
least value.
least value.

all six comparisons between the two temperature groups.

Undoubtedly differences existed, which could be attributed

to temperature, but caution should be exercised in con-

cluding that all of this was due to temperature alone.

Some of this dissimilarity in water intake between the

hot and cold chamber ewes may be a function of the water-

ing method. This cannot be discounted.

72

The increase in water consumption induced by in-
creased ambient temperature is in agreement with results
obtained by Ragsdale 33 gl. (1949, 1951) in cattle,
Appleman and Delouche (1958) in goats, and Henderson (1958)
in sheep.

Although there were many significant differences be-
tween the various light groups. as can be seen from table
14, there was also a significant (P< .Ol) interaction be-
tween light and temperature. Water consumption tends to
increase with increasing hours of light to 12 hours daily
and then declines. Again, as was the case with many other
measures, the constant light ewes did not follow this pat-
tern. Possibly their high water intake is a result of
the stress imposed by continuous light; but a more logical
explanation is that their water consumption could have
been a consequence of the ewes' thin condition at the on-
set of the experiment.

Ragsdale gt al. (1949) and Henderson (1958) both
concluded that water consumption paralleled feed intake
under controlled environmental conditions. This trend is
evident in the present study. When the averages of the
light groups are considered, the means in feed and water
consumption can be ranked in a similar order. The sole
exceptions are the 16 and 20 hour light ewes. The former
are ranked 5th and the latter 6th in water intake, but the

order is reversed on the basis of feed consumption.

73

Thyroid secretion rate was not significantly corre-

lated with water consumption at either ambient temperature.

I. Respiration Rate as Affected by Ambiept Temperature agg
Artificial Light.
Values for respiration rate are reported as flank
movements per minute. Ten such measurements were collected
on each ewe over the 30 day experimental period. The av-

erages are presented in table 15.

TABLE XV

Effect of Ambient Temperature and Artificial
Light on Respiration Rate‘

 

 

 

 

 

 

 

===========================ii :-———6—— <2:
Hogighgf oAmbient Temperaturg . Average
4 68.7 I 10.0"(6)x 174.6 I 20.5 (6) 121.7alb
44.1 I 1.5 (6) 155.2 I 2.2 (6) 98.7
12 49.4 I 4.6 (6) 144.5 I 4.2 (6) 97.0
16 61.5 I 8.8 (6) 121.4 I 8.4 (5) 88.8
20 54.7 I 1.9 (6) 115.1 I 7.9 (6) 75.9
24 57.8 I 2.4 (6) 155.2 I 14.8 (6) 95.5
Average 49.4 144.0a

 

’ Values are expressed as flank movements per minute.
" Mean I standard error of the estimate.
x Figures in parentheses indicate number of animals from
which mean was derived.
a Significantly different EP<..Olg from least value.
b Significantly different P< .05 from 2 least values.

74

The ewes maintained at 90° F. had a significantly
(P<:.01) faster respiratory rate than did the 50° F. ani-
mals. The averages of the two temperature groups, 49.4 and
144.0, agree quite closely with Henderson (1958), who re-
ported values of 43.6 and 130.3 for these respective tem-
perature groups. This same observation, that increasing
ambient temperature increases the respiratory rate, has
also been reported by Lee 23 gl. (1945), Miller and Monge
(1946), Robinson and Lee (1947), Heitman and Hughes (1949),
Heitman 33 a1. (1951), Kibler and Brody (1949, 1951, 1954),
Reik 23 gl. (1950), McDowell g§,al. (1953), Johnson and
Branton (1953), Dutt and Bush (1953), Kibler (1957) and
Appleman and Delouche (1958).

While no clear cut pattern prevailed which could be
explicitly attributed to light, the respiration rates did
decline with increasing hours of light and then increased
with constant illumination. Four hours of light produced
a significantly (P< .05) greater response than did 16 and
20 hours of light. There was a significant (P< .05) in-
teraction between light and temperature. The highest
values were obtained at 90° F. and 4 hours of light.

Respiration rate could be related neither to thyroid
secretion rate nor zero time percent uptake within either

chamber temperature.

75

McDowell 23 a1. (1953) have concluded that respira-
tory rate is not as effective as respiratory volume in
measuring heat tolerance in cattle. While no measurements
were made on reSpiratory volume in this study, it can be
concluded from the data that at a given temperature res-
piration rate is not a satisfactory indication of energy

metabolism or thyroid function.

J. Rectal Temperature as Affected by Ambient Temperature
and Artificial Light.

Ten rectal temperatures were taken on each ewe dur-
'ing the course of the 30 day experiment and the value re-
ported for each ewe is an average of the ten measurements.
A11 observations were taken at approximately 5 P.M. and
on the same days as the respiratory rates. The results
are shown in table 16.

Rectal body temperatures of the 90° F. groups were
significantly (P< .01) higher than those of the 50° F.
ewes. This agrees with previous research reported by Lee
23 al. (1945), Robinson and Lee (1947), Heitman and Hughes
(1949), Heitman gt g1. (1951), Kibler and Brody (1949,
1951), Henderson (1958) and many others. All workers con-
cluded that rectal temperatures were elevated by increas-
ing ambient temperatures above the critical temperature.

With the exception of the 12 hour light groups, rec-

tal body temperatures tended to decline with increasing

TABLE XVI

76

Effect of Ambient Temperature and Artificial Light
on Rectal Temperature‘

 

 

 

 

Hours of Ambient Tem erature
Light -—-__553-FT____-_-_E-——-95?_FT-___— Average
4 105.25 I .l3”(6)x 104.29 I .17 (6) 105.76b
102.90 I .11 (6) 104.44 I .18 (6) 105.67b
12 105.40 I .15 (6) 104.55 I .29 (6) 103.883b
16 102.60 I .15 (6) 105.21 I .18 (5) 102.88
20 102.70 I .09 (6) 105.95 I .15 (6) 105.51
24 105.06 I .09 (6) 105.94 I .16 (6) 105.50c
Average 102.98 104.06b

 

‘ Values expressed as degrees Fahrenheit.

*‘ Mean 1 standard error of the estimate.

X Figures in parentheses indicate number of animals from
which mean was derived.

OO'D

Significantly different (P< .05
Significantly different
Significantly different

(P< .Ol
(P< .05

from least two values.
from least value.
from least value.

light to 16 hours and then rise with further illumination.

The high values obtained in the 12 hour groups can be par-

tially attributed to the age of these young ewes and are

not entirely a function of light.

These sheep were only

4 to 5 months of age when placed on experiment while the

next youngest group were at least 8 months old when the

trial commenced.

Howell (1948) reported that both mouth

and axillary temperatures in men were lowered with increased

age.

77

The 12 hour ewes consumed the most feed per unit
weight compared to all other groups. This may have been
another factor which was responsible for their elevated
rectal temperatures. Both Robinson and Lee (1947) and
Reik 22 gl. (1950) observed that sheep on a high plane of
nutrition exhibited increased rectal temperatures as com-
pared to controls.

Rectal body temperatures were not significantly cor-
related with either thyroid secretion rate or zero time
percent uptake within either ambient temperature. This is
in agreement with Henderson (1958) who reported that there

0

was no significant correlation between I151

output half-
time and rectal body temperature.

Contrary to the results noted in cattle by McDowell
33 31. (1953), respiration rate and rectal body tempera-
ture could be related in this study. A positive corre-
lation of .391, which was significant (P<’.01), was ob-
tained between these two measures when both temperature
groups were pooled. Within individual temperature groups
correlations of +.354 and +.342 were found for the re-

spective 50° F. and 90° F. groups. Both of these coeffi-

cients were significant at the 5 percent level.

78

K. The Influence ofpémbient Temperature agd Artificial
Light gg_the Cessation of the Breeding Season ig_Ewes.

In the fall of 1958, ewes, after exhibiting heat
periods, were placed in the 50° F. and 90° F. chambers and
subjected to 16 hours of light daily. There were two 8
hour periods of light and two 4 hour periods of darkness
each day. This ratio of 2 parts light to 1 part dark was
selected on the basis of the reports of Hafez (1951, 1952)
who observed that this light treatment resulted in the
cessation of the breeding season in 6 to 24 weeks from the
start of the study. He agreed with Hart (1950) that gradu-
ally increasing the light was no more effective in st0p-
ping cycling than the abrupt 16 hour 1ight:8 hour dark
ratio.

While no literature is available on the effect of
heat on the cessation of the breeding season, Dutt and
Bush (1955) have reported that the onset of the breeding
season was hastened by 45-48° F. temperatures as compared

to a control temperature of 88° F. 0n the basis of this
7 information chamber temperatures of 50° F. and 90° F. were
selected for this study.

The ewes were checked twice each day with a vasectom-
ized ram from the time they entered the chambers on October
6, 1958, through January 24, 1959.

After approximately 16 weeks (110 days) one ewe in
the 50° F. chamber and two in the 90° F. chamber had

79

definitely stOpped cycling. These three sheep exhibited
only one additional heat period after being admitted to
the chambers.

Three ewes in the cold room and two in the hot room
had failed to exhibit one or more of their scheduled estrual
periods just prior to being removed from the chambers.
While no definite conclusion can be drawn, these five ewes
may have concluded their cycling season.

Two ewes maintained at 50° F. and one at 90° F. were
definitely still cycling after 110 days. The heat periods
are graphically depicted in figure 3.

Elevated ambient temperature had no significant ef-
fect on the cessation of the breeding season when the data
were subjected to analysis of variance. While the light
effect did not lend itself to statistical analysis it can
be concluded that a 2 parts light-l part dark ratio is
effective in hastening the st0ppage of the breeding season
in some ewes.

Furthermore, these data agree with those of Yeates
(1949) and Hafez (1951, 1952); the former reported 14 to
19 weeks and the latter 6 to 24 weeks as being necessary
to stop the breeding season by the above light treatment.

Ambient temperature had no effect on the length of
the interestrual period or percent of silent heats. There

were 13.8 and 10.5 percent of the theoretically possible

80

m wb<o ébmhmu

8*

 

 

 

0."... 0N6 0.0 O... 3.0 9.0
i e .e e e“
i e e e e e e e H
w "
.954‘_a .. .ow e m
. n e e e e h
.>OZ .. 2 "Ti mmemsemo some $05 98838 E Beam llw M
“annv I.AU w 0 O O O O M
tum - m u e o e e e e H
. O i
n e e e .e e e“
m 0. O O A. O ”
>nuv. . N
e e A

no.

*0

a: 5000
n;..

2..

00.

«QC

”0

“NO. Loon
5N

he.

 

 

 

.moem as nommmm wqaoomam on» no aofipmmmmo on» no moss»
umummsee pnmapse oea ens has new names meson ma co racemes anopapannH

m—s»m_

.m enamam

81

heat periods which were not accompanied by overt manifesta-
tions of estrus in the 50° F. and 90° F. chamber, respec-

tively.

L. The Influence of Ambient Temperature and Artificial
Light on the Induction of Estru§_in Ewes.

On March 1, 1959. 12 purebred English Shropshire ewes
approximately one year of age were randomly assigned to
each environmental chamber. The lights were regulated so
they would be on for 8 hours each day. There were two 4
hour periods of light and two 8 hour periods of darkness
each day. Again, as with attempts to inhibit the breeding
season, the reports of Yeates (1949), Hafez (1950, 1952)
and Hart (1950) were the basis for the selection of the
light ratio.

While McKenzie and Phillips (1933) observed no stim-
ulatory effect in inducing early estrus from refrigeration
I Dutt and Bush (1955) concluded that temperature was a fac-
tor. 0n the basis of the latter‘s report 50° F. and 90° F.
temperatures were selected for this study.

The ewes were checked twice each day with a normal
ram through May 28; subsequent to this date the ewes in
the 50° F. chamber were turned loose with a ram of known
fertility wearing a marking harness. This ram was then
placed twice each day for half-hour periods with the 90° F.
ewes which had also been freed from their individual pens

On May 28.

82

On June 4 and 9, ewes number 366 and 300 respectively
in the cold chamber had been marked; but the ram was never
actually seen breeding these two animals. Since no other
ewes had exhibited heat periods by July 1, the experiment
was terminated. To prolong the study would have infringed
upon the natural breeding season of sheep and therefore,
no conclusions could have been made. The two mentioned
ewes failed to lamb. This could either be attributed to
the ewes' failure to conceive, poor embryo survival or
false heats. The latter explanation appears to be the most
logical since none of the other ewes on the same treatment
exhibited heat or were marked by the ram.

While no conclusions can be drawn, the problem can
be posed, "Why did the ewes fail to cycle?" Location was
not a factor since Sykes and Cole (1944) were successful
in getting 5 out of 8 ewes to lamb in November at this
same experiment station. Although the previous workers
first increased light and then gradually decreased it,
Means 33 gl. (1959) at Lafayette, Indiana, subjected ewes
to an immediate 10 hour period of light and were success-
ful in inducing estrus in 27 of 39 ewes. The Purdue study
was performed at the same time of the year as the present
investigation. In one individual group of ewes receiving
two long dark periods and two short light periods per 24
hours, which was similar to the procedure in this investi-

gation, Means reported that only 2 out of 10 ewes came

83

into heat and none conceived.

Hart (1950) had been successful in hastening the on-
set of estrous in Suffolk ewes with 4-8-4-8 and 4-2-4—14
variations of the 8 hour light-l6 hour dark ratio. This
experiment had been performed in England. Therefore,
since Means g2 g1. (1959) met with failure only when they
doubled the daily light-dark contrast periods, it would
appear that an interaction exists between location and
response to a given light treatment.

The intensity of light does not appear to be a fac-
tor in inducing estrus during the non-breeding season.
Yeates (1949) used four 100 watt light bulbs suspended 5
feet 8 inches above the floor and was successful in ac-
celerating estrus in ewes. In this study four 300 watt
bulbs were suspended 8 feet from the floor in the 50° F.
chamber and six similar bulbs 16 feet above the floor
in the 90° F. room.

While it cannot be definitely determined why the
ewes failed to exhibit heat in the present study, it
seems probable that the 2 light—dark contrast periods per
day instead of the customary 1 may have been the factor

responsible for the failure encountered.

VI. SUMMARY AND CONCLUSIONS

Thyroid secretion rate values were obtained on 64
ewes under controlled conditions of ambient temperature
and artificial light. This investigation was carried out
with 12 combinations of light and temperature, each trial
lasting 30 days. In addition to thyroid secretion rate
information, the effects of temperature and light on the
following were observed:

Zero time percent uptake of 1151

1131 output half-time (Tfi)

Thyroid epithelial cell height

Body weight gains

Feed consumption

Feed efficiency

Water consumption

Respiration rates

Rectal body temperatures

Cessation of the breeding season

Induction of the breeding season

Decreasing the ambient temperature from 90° F. to

50° F. induced a three-fold increase in the thyroid secre-

tion rate, which was significant (P< .01). Increasing the

hours of light in increments of 4 hours produced a biphasic

- 84 _

85

effect within the range 4 through 24 hours per day. Dif-
ferences between the highest and lowest values were signi-
ficant (P< .01). By increasing the illumination from 4
hours daily to 12, thyroid activity was progressively de-
pressed, but with added light above 12 hours the thyroid
secretion rate steadily rose. The highest values were ob-
tained under continuous light. The parabolic pattern was
in evidence under both 50° and 908 F. temperatures.

Subjecting ewes to an elevated ambient temperature
significantly (P< .05) increased the zero time percent up-
take of 1131. Increasing the daily hours of illumination
significantly (P< .01) depressed the uptake of radioiodine.
A negative relationship (r a -.255, P< .05) existed be-
tween thyroid secretion rate and zero time percent uptake,
but the Specific factors which promote thyroid hormone se-
cretion do not necessarily inhibit 1151 uptake.

It was concluded that 1151

output half-time (T%) was
not a valid measurement of thyroid activity in this inves-
tigation and no significant correlation existed between
thyroid secretion rate and T%. Temperature and light ef-
fects could not be assessed by the latter method.

Ten individual comparisons were made between the
thyroid secretion rate and thyroid epithelial cell height

in ewes maintained under 12 hours of light. There was a

positive relationship (r a .580, P< .08) between these

86

measures which approached significance. The acinar cell
heights of ewes subjected to the 50° F. temperature were
significantly (P< .01) greater than those kept at 90° F.

The results of these experiments indicate that only
thyroid secretion rate measurements are valid for quanti-
tatively assaying the activity of the thyroid gland in the
intact sheep. Furthermore, the data reveal that the se-
cretion rate can be related to the epithelial cell height
measurement within individual animals.

Ewes maintained at 50° F. significantly (P< .01)
outgained their 90° F. counterparts during the 30 day trial
period; and a 12:12 light to dark ratio was most conducive
to rapid gains. These findings may have practical appli-
cation for the sheep raiser.

A positive correlation of .240 (P< .06) existed be-
tween thyroid secretion rate and body weight gains. Thus
it is apparent that a physiologically hyperthyroid state
stimulates rapid gains in sheep.

No conclusions could be drawn in regard to the ef-
fects of temperature and light on feed consumption and'mfis
measure was not significantly related to the thyroid se-
cretion rate in the present study.

Feed efficiency was significantly (P< .01) improved
by the 50° F. temperature when compared to the warmer

(90° F.) environment. Thyroid secretion rate was

87

significantly (P< .05) correlated (r a +.268) with feed
efficiency. Since temperature had no effect on feed con-
sumption it can be concluded that the increased secretion
by the thyroid was a factor in promoting the efficiency
of feed conversion.

Water consumption was stimulated by the higher am-
bient temperature and within temperatures it paralleled
feed consumption. Thyroid activity had no effect on water
intake.

Both reSpiratory rate and rectal body temperatures
were significantly (P< .01) elevated by the increased
ambient temperature and these two measures were signifi-
cantly correlated (r a .391, P< .01). There was a tendency
for both respiration rates and rectal temperatures to de-
crease with increasing hours of light to 12 hours and then
increase with increasing illumination to 24 hours, but ex-
ceptions occurred. It is pointed out that there was too
much variation in age and state of nutrition between light
groups to ascribe a definite effect to the light pattern
relative to the above two phenomena.

A ratio of 16 hours_light to 8 hours darkness in-
hibited the estrous cycle in some ewes. Much variation
existed between ewes in their response to this experimental
treatment. Furthermore, a time interval of over 16 weeks

is required if cycling activity is to be completely

88

inhibited in a large pr0portion of animals. From the data
obtained in this study temperature has no effect on the
cessation of the breeding season in sheep.

A 16 hour darkness to 8 hour light ratio, which was
divided into two light-dark contrast periods per day,
failed to induce estrus in ewes maintained at either 50°
F. or 90° F. temperatures. This study began on March 1,-
and was terminated 4 months later on July 1, 1959. Lit-
erature published subsequent to the completion of this
study indicates that the two contrast periods per day
instead of the normal one may have been responsible for

the failure of the ewes to exhibit estrus.

VII. BIBLIOGRAPHY

Amin, A., C. K. Chai and E. P. Reineke. 1957. Differences
in thyroid activity of several strains of mice and
F1 hybrids. Am. J. Physiol. 191:34.

Appleman, R. D. and J. C. Delouche. 1958. Behavioral,
physiological and biochemical responses of goats
to temperature, 0° to 40° C. J. Animal Sci. 17:326.

Beeson W. M., F. N. Andrews, H. L. Witz and T. W. Perry
1947. The effect of thyroprotein and thiouracil on
the growth and fattening of swine. J. Animal Sci.
6:482.

Bissonette, T. H. 1932. Modification of mammalian sexual
cycles. Proc. Royal Soc. B. 110:322.

Black, W. 6., A. L. Schick, A. L. Pepe and L. E. Casida.
1950. Some effects of testosterone propionate and
thyroprotein in rams. J. Animal Sci. 9:186.

Blaxter, K. L., E. P. Reineke, E. W. Crampton and W. E.
Peterson. 1949. The role of thyroidal materials
and of synthetic goitr0gens in animal production
and an appraisal of their practical use. J. Animal
Sci. 8:307.

Blincoe, C. and S. Brody. 1955. Environmental physiology.
XXIV. The influence of ambient temperature, air ve-
locity, radiation intensit , and starvation.on thyroid
activity and iodine metabo ism in cattle. Missouri
Agre 3:!th Stae R33. B111. 576. '

Blincoe, Clifton. 1958. Environmental physiology.
XLVII. The influence of constant ambient tempera-
ture on the thyroid activity and iodide metabolism
of Shorthorn, Santa Gertrudis and Brahman calves
during growth. Missouri Agr. Expt. Sta. Res. Bul. 649.

Brody, Samuel. 1945. Bioenergetics and Growth. Reinhold
Publishing Co., New York.

Brody, S., A. C. Ragsdale H. J. Thompson and D. M. Worstell.
1954. Environmental physiology. XXVIII. The thermal
effects of radiation intensity (light) on milk pro¢
duction, feed and water consumption and body weight
in Holstein Jersey and Brahman cows at air tempera-
tures 45°, 70° and 80° F. Missouri Agr. Expt. Sta.
Res. Bul. 556.

- 89 -

90

Bogart, R. and D. T. Mayer. 1946. Environmental tempera-
ture and thyroid gland involvement in lowered fer-
tility of rams. Missouri Agr. Expt. Sta. Res. Bul.
402.

Brown-Grant, K. 1956. Changes in the thyroid activity of
rats exposed to cold. J. Physiol. 131:52.

Burroughs, W., A. Raun, A. Trenkle and N. Raun. 1960.
Further observations upon the effects of methimazole
upon feedlot performance and carcass characteristics
of fattening cattle. J. Animal Sci. 19:465.

Casady, R. B. 1953. The effect of exposure to high am-
bient temperature on spermatogenesis in the dairy
bull. J. Dairy Sci. 36:14.

Casady, R. B., J. E. Legates and R. M. Myers. 1956. Cor-
relations between ambient temperature varying from
60° F. to 95° F. and certain physiological responses
in young dairy bulls. J. Animal Sci. 15:141.

Catz, B., Ihsan E1 Rawi and E. Geiger. 1953. Activity of
_ thyroid of cold-exposed rats evaluated by 1151 uptake
and histometric studies. Am. J. Physiol. 174:29.

Chai, C. K., A. Amin and E. P. Reineke. 1957. Thyroid
iodine metabolism in inbred and F1 hybrid mice. Am.
J. Physiol. 188: 499.

Cramer, W. 1916. On the thyroid-adrenal apparatus and
its function in heat regulation of the body. J.
Physiol. 50:38.

Dempsey, E. W. and E. B. Astwood. 1943. Determination of
thyroid hormone secretion at various environmental
temperatures. Endocrin. 32:509.

Dempsey, E. W. and H. F. Searles. 1943. Environmental
modification of certain endocrine phenomena. Endo-
crin. 32:119.

Dutt, R. H. and L. F. Bush. 1956. The effect of low en-
vironmental temperature on initiation of the breeding
season and fertility in sheep. J. Animal Sci. 14:885.

Dutt, R. H., E. F. Ellington and W. W. Carlton. 1956.
Effect of shearing and exposure to elevated air tem—
perature on fertility and early embryo survival in
ewes. J. Animal Sci. 15:1287.

91

Dutt, R. H. E. F. Ellington and W. W. Carlton. 1959.
Fertilization rate and early embryo survival in
sheared and unsheared ewes following exposure to
elevated air temperature. J. Animal Sci. 18:1308.

Eaton, 0. N., R. G. Schott, V. L. Simmons and A. H. Frank.
1948. The effects of feeding thyroprotein on semen
characteristics of rams. J. Animal Sci. 7:449.

Flamboe, E. E. and E. P. Reineke. 1959. Estimation of
thyroid sigfetion rates in dairy goats and measure-
ment of I uptake and release with regard to age,
pregnancy, lactation and season of the year. J.
Animal Sci. 18:1135.

Fletcher, J. L. and G. R. Reid. 1953. The effect of
shearing on the reaction of lambs to high environ-
mental temperatures. J. Animal Sci. 12:666.

Foote, W. G., A. L. Pope, R. E. Nichols and L. E. Casida.
1957. The effect of variation in ambient tempera-
ture and humidity on rectal and testes temperature
of shorn and unshorn rams. J. Animal Sci. 16:144.

Frape, D. L., J. W. Gage, Jr., V. W. Hays, V. C. Speer
and D. V. Catron. 1958. Studies on the iodine re-
uirement and thyroid function of young pigs.
Abstract) ,J. Animal Sci. 17:1225.

Freinkel, N. and D. Lewis. 1957. The effects of lowered
environmental temperature on peripheral metabolism
of labelled thyroxine in the sheep. J. Physiol.
135:288.

Godfrey, N. W. and D. E. Tribe. 1959. The effect of
thyroxine implantation on wool growth. J. Agr. Sci.
5133690

Griffin, S. A. 1955. The thyroid secretion rate of sheep
as related to season, breed, sex and its relation to
semen quality in the ram. Ph.D. Thesis, Michigan
State University.

Grosvenor, C. E. and C. W. Turner. 1958. Effect of Opti-

mal thyroxine levels upon milk secretion. (Abstract)
J. Animal Sci. l7fl226.

Hafez, E. S. E. 1950. Sexual season of the ewe and day-
light environment. Nature 166:822.

92

Hafez, E. S. E. 1951. Inhibitory action of artificial
light on the sexual season of the ewe. Nature
168:336.

Hafez, E. S. E. 1952. Studies on the breeding season
and reproduction of the ewe. J. Agr. Sci. 42:189.

Hammond, J. Jr. 1944. On the breeding season in sheep.
J. Agr. Sci. 34:97.

Hart, D. S. 1950. Phot0periodicity in Suffolk sheep.
J. Agr. Sci. 40:143.

Hart, D. S. 1950. Phot0periodicity in the female ferret.
J. Expt. Biology 28:1.'

Heitman, H. and E. H. Hughes. 1949. The effect of air
temperature and relative humidity on the physiolo-
gical well being of swine. J. Animal Sci. 8:171.

Heitman, H., E. H. Hughes and C. F. Kelly. 1951. Effect
of elevated ambient temperature on pregnant sows.
J. Animal Sci. 10:907.

Henneman, H. A., S. A. Griffin and E. P. Reineke. 1952.
A determination of thyroid secretion rate in intact
individual sheep. (Abstract) J. Animal Sci. 11:794.

Henneman, H. A., E. P. Reineke and S. A. Griffin. 1955.
The thyroid secretion rate of sheep as affected by
season, age, breed, pregnancy and lactation. J.
Animal Sci. 14:419.

Henderson, H. E. 1958. The effect of environmental
temperature and light on thyroid activity and cer-
tain metabolic measures in sheep. Ph.D. Thesis,
Michigan State University.

Hoffert, J. R. 1959. Determination of thyroid secretion
rate in rainbow trout, Salmo gairdnergy M.S. Thesis,
Michigan State Universi y.

Howell T. H. 1948. Normal temperatures in old age.
Lancet 254:517.

Hurst, V. and C. W. Turner. 1948. The thyroid secretion
rate in the mouse and its relation to various physi-
ological processes. Missouri EXpt. Sta. Res. Bul.

93

Johnson. C. W., V. W. Hays, V. C. Speer and D. V. Catron.
1959. Thyroprotein for lactating sows. J. Animal
Sci. 18:1224.

Johnston, J. E. and C. Branton. 1953. Effects of seasonal
climatic changes on certain physiological reactions,
semen production and fertility of dairy bulls. J.
Dairy 301 e 26:954.

Kendall, E. C. and D. G. Simonsen. 1928. Seasonal vari-
ation in the iodine and thyroxine content of the
thyroid gland. J. Biol. Chem. 80:357.

Kenyon, A. T. 1935. Thyroid hypertrOphy in the rat with
reference to the effect of light. Proc. Soc. Expt.
Biol. and Med. 32:697.

Kibler, H. H. and S. Brody. 1949. Environmental physi-
ology. VII. Influence of temperature, 50° to 5° F.
and 50° to 95° F. on heat production and cardiores-
piratory activities of dairy cattle. Missouri Agr.
Expt. Sta. Res. Bul. 450.

Kibler, H. H. and S. Brody. 1951. Environmental physi-
ology. XIII. Influence of increasing temperature,
40° to 105° F. on heat production and cardiorespira-
tory activities in Brown Swiss and Brahman cows and
heifers. Missouri Agr. Expt. Sta. Res. Bul. 473.

Kibler, H. H. and S. Brody. 1954. Environmental physi-
ology. XXXI. Influence of radiation intensity on
evaporative cooling, heat production and cardiores-
piratory activities in Jersey, Holstein and Brahman
cows. Missouri Agr. Expt. Sta. Res. Bul. 574.

Kibler . H. 1957. Environmental physiology. XLIII.
orgy metabolism and cardiorespiratory activities
in Shorthorn, Santa Gertrudis and Brahman heifers
during growth at 50 and 80° F. temperatures.
Missouri Agr. Expt. Sta. Res. Bul. 643.

Kleinpeter, M. E. and J. Mixner. 1947. The effect of the
quantity and quality of light on the thyroid activity
of the baby chick. Poultry Sci. 26:494.

 

Knigge, K. M. and S. M. Bierman. 1958. Evidence of CNS
if§ uence upon cold-induced acceleration of thyroidal
I release. Am. J. Physiol. 192:625.

94

Lee, D. H. K., K. W. Robinson, N. T. M. Yeates and M. I. R.
Scott. 1945. Poultry husbandry in hot climates -
experimental inquiries. Poultry Sci. 24:195.

Lewis, R. C., E. P. Reineke and J. R. Lodge. 1955. A
technique for estimating thyroid secretion rate in
dairy cattle. (Abstract) J. Animal Sci. 14:1250.

Lodge, J. R., R. G. Lewis and E. P. Reineke. 1957. Esti-
mating the thyroid activity of dairy heifers. J.
Dairy Sci. 40:209.

Lodge, J. R., R. C. Lewis, E. P. Rigfeke and L. D. McGiIUtmd.
1958. Thyroidal uptake of I by dairy calves. J.
Dairy Sci. 41:641.

Magnus-Levy, A. Berl. Klin. Wchnschr. 1895. 32:650.
Cited by Reineke, E. P. and C. W. Turner. Chapt.
XIX. Thyroidal substances. Emmens, C. W., Editor.
Hormone Assay. Academic Press. New York. 1950.

Maqsood, M. and E. P. Reineke. 1950. Influence of vari-
ation in environmental temperature and thyroid status
on growth and feed consumption of the male mouse.

Am. J. Physiol. 160:253.

Maqsood, M. 1950. The role of the thyroid in sexual de-
ve10pment in the male. Nature 166:692.

Marshall, F. S. H. 1940. The experimental modification of
the estrus cycle in the ferret by different inten-
sities of light. J. Expt. Biol. 17:139.

Mayerson, H. S. 1935. The effect of light and darkness
on the thyroid gland of the rat. Am. J. Physiol.

113:659.

McDowell, R. E., D. H. Lee, M. H. Fohrman and R. S. Anderson.
1953. Respiratory activity as an index of heat tol-
erance in Jersey and Sindhi x Jersey (Fl) crossbred
cows. J. Animal Sci. 12:573.

McKenzie, F. F. and R. W. Phillips. 1933. The effects of
temperature and diet on the onset of the breeding
season in sheep. Missouri Agr. Expt. Sta. Bul. 328.

Means, T. 1.1., F. N. Andrews and W. E. Fontaine. 1959. En-
vironmental factors in the induction of estrus in
sheep. J. Animal Sci. 18:1388.

95

Meites, J. and B. Chandrashaker. 1948. Effect of thyroid
status on response of the gonads to pregnant mare's
serum. J. Animal Sci. 7:542.

Mellen, W. J. and B. C. Wentworth. 1959. Thyroid studies
in the domestic fowl utilizing radioiodine. USAEC
Publication TID-7578. pp. 77—86.

Mercier, E. and G. W. Salisbury. 1947a. Fertility level
in artificial breeding associated with season, hours
of daylight and the age of cattle. J. Dairy Sci.
30:817.

Mercier, E. and G. W. Salisbury. 1947b. Seasonal varia-
tion in hours of daylight associated with fertility
level of cattle under natural breeding conditions.
J. Dairy Sci. 30:747.

Miller, J. C. and L. Monge. 1946. Body temperature and
respiration rate and their relation to adaptability
in sheep. J. Animal Sci. 5:147.

Mills, 0. A. 1918. Effects of external temperature, mor-
' phine, quinine and strychnine on thyroid activity.
Am. J. Physiol. 46:329.

Mixner, J. P., E. P. Reineke and C. W. Turner. 1944. Ef-
fect of thiouracil and thiourea on the thyroid gland
of the chick. Endocrin. 34:168.

Moon, R. C. and C. W. Turner. 1960. Effect of ovariec-
tomy and replacement therapy upon thyroxine secre-
tion rate of rats. Proc. Soc. Expt. Biol. and Med.
105 :66. '

Mfirch, J. R. 1929. Standardization of thyroid prepara-
tions. J. Physiol. 67:221.

Nadler, N. J. and C. P. Leblond. 1958. Rates of passage
of iodine into and out of the thyroid gland of the
rat under various conditions of dietary iodine in-
take and body weight. Endocrin. 62:768.

IVewland, H. W., W. N. McMillen and E. P. Reineke. 1952.
Temperature adaptation in the baby pig. J. Animal
Sci. 11:118.

(iloufa, M. M., R. Bogart and F. F. McKenzie. 1951. Ef—
fect of environmental temperature and the thyroid
gland on fertility in the male rabbit. Oregon State
College Tech. Bul. 20.

96

Peo, E. R., Jr. and D. B. Hudman. 1960. Supplementation
of pig starters with thyroprotein. J. Animal Sci.

19:477.

Perry, W. F. 1951. A method for measuring thyroid hor-
mone secretion rate in the rat with its application
to the bioassay of thyroid extracts. Endocrin. 48:
643.

Petersen, W. E., A. Spielman, B. S. Pomeroy and W. L. Boyd.
1941. Effect of thyroidectomy upon sexual behavior
of the male bovine. Proc. Soc. Expt. Biol. and Med.
46:16.

Pipes, G. W., B. N. Premachandra and C. W. Turner. 1959.
The biological half-life of l-thyroxine and l-
triiodothyronine in the blood of the dairy cow. J.
Dairy Sci. 42:1606. .

Premachandra, B. N., G. W. Pipes and C. W. Turner. 1957.
A study of thyroxine secretion in cattle. J. Animal
Sci. 16:1063.

Premachandra, B. N., G. W. Pipes and C. W. Turner. 1958.
Variation in the thyroxine secretion rate in cattle.
J. Dairy Sci. 41:1609.

Puntriano, G. and J. Meites. 1951. The effect of continu-
ous light or darkness on thyroid function in mice.
Endocrin. 48:217.

Ragsdale, A. C., D. M. Worstell, H. J. Thompson and S.
Brody. 1949. Environmental physiology. VI. In-
fluence of temperatures, 50°-0° F. and 50°-95° F.
on milk production, feed and water consumption and
body weight in Jersey and Holstein cows. Missouri
Agr. Expt. Sta. Res. Bul. 449.

Ragsdale, A. C. H. J. Thompson, D. M. Worstell and S.
Brody. 1951. Environmental physiology. XII.
Influence of increasing temperature 40° to 105° F.
on milk production in Brown Swiss cows and on feed
and water consumption and body weight in Brown Swiss
and Brahman cows and heifers. Missouri Agr. Expt.
Sta. Res. Bul. 471.

IRagsdale, A. C., H. J. Thompson. D. M. Worstell and S.
Brody. 1953. Environmental physiology and shelter
engineering. XXI. The effect of humidity on milk
production and composition, feed and water consump-
tion and body weight in cattle. Missouri Agr. Expt.
Sta. Res. Bul. 521.

97

Rawson, R. W. and P. Starr. 1938. Direct measurement of
height of thyroid epithelium; a method of assay of
thyrotrophic substances. Archives of Internal Med.
61(5):?26.

Reik, R. F., M. H. Hardy, D. H. K. Lee and H. B. Carter.
1950. The effect of the dietary plane upon the re-
action of two breeds of sheep during short exposures
to hot environments. Aust. J. Agr. Res. 1:217.

Reineke, E. P., A. J. Bergman and C. W. Turner. 1941.
Effect of thyroidectomy of young male goats upon
certain AP hormones. Endocrin. 29:306.

Reineke, E. P. and C. W. Turner. 1945. Seasonal rhythm
in the thyroid hormone secretion of the chick.
Poultry Sci. 24:499.

Reineke, E. P. and W. N. McMillen. 1946. The effect of
synthetic thyr0protein on lactation and growth in
swine. J. Animal Sci. 5:420.

Reineke, E. P. and F. A. Soliman. 1953. Role of thyroid
hormone in reproductive physiology of the female.
Iowa State College J. of Sci. 28:67.

Reineke, E. P. and 0. N. Singh. 1955. Estimation of
thyroid secretion rate of the intact rat. Proc. Soc.
Expt. Biol. and Med. 88:203.

Reineke, E. P., C. K. Chai and A. Amin. 1956. The thy-
roidal iodine uptake and output rates in inbred
mice. (Abstract) Am. J. Physiol. 187:583.

Reineke, E. P. 1959. Thyroid function in several species
of animals with special reference to environment
and body size. USAEC Publication TIE-7578. pp.
87-96. 4

Reineke, E. P., H F. Travis and P. E. Kifer. 1960.
Thyroidal 1151 turnover, thyroxine secretion rate
and thyroactive iodinated casein utilization in
mink (Mustela vison). Am. J. Vet. Res. (In press).

Robinson, K. and D. H. K. Lee. 1947. Effect of the nu-
tritional plane upon the reactions of animals to
heat. ,J. Animal Sci. 6:182.

Rowan, W. 1925. Relation of light to bird migration and
develOpmental changes. Nature 115:494.

98

Seidell, A. and F. Fenger. 1913. Seasonal variation in
the iodine content of the thyroid gland. J. Biol.
Chem. 13:517.

Singh, 0. N. . A. Henneman and E. P. Reineke. 1956.
The relationship of thyroid activity to lactation,
growth and sex in sheep. J. Animal Sci. 15:625.

Skoog, T. von. 1939. Durch extreme Temperaturen
verursachte Veranderungen der quantitativen mikro-
morphologischen Verhaltnisse in der Glandula thy-
roidea. Anat. Anz. 88:289.

Snedecor, G. E. 1956. Statistical Methods. Iowa State
College Press, Ames, Iowa.

Soliman, F. A. and E. P. Reineke. 1954. Changes in up-
take of radioactive iodine by the thyroid of the rat
during the estrous cycle. Am. J. Physiol. 178:89.

Soliman, F. A. and E. P. Reineke. 1954. Cyclic variation
in thyroid function of female mice as assessed by
radioactive iodine. J. Endocrin. 10:305.

Soliman, F. A. and E. P. Reineke. 1955. Influence of
estrogen and progesterone on radioactive iodine up-
take by rat thyroid. Am. J. Physiol. 183:63.

Stein, K. F. and E. Carpenter. 1943. The effect of in-
creased and decreased light on the thyroid gland of
Triturus viridescegg. J. Morph. 72:491.

Swanson, E. W., F. W. Lengemann and R. A. Monroe. 1957.
Factors affecting the thyroid uptake of 1151 in
dairy cows. J. Animal Sci. 16:318.

Sykes, J. F. and C. L. Cole. 1944. Modification of mating
season in sheep by light treatment. Mich. Expt. Sta.
Quart. Bul. 26:4.

Teitelbaum, H. A. and 0. G. Harne. 1941. A closed-circuit
metabolism apparatus for studying oxygen consumption
of control and thyreo-activator-treated guinea pigs.
J. Lab. Clin. Med. 26: 1521.

frerry, W. A. 1951. The effect of constant light or dark-
ness on the thyroid gland of the sheep and on the
estrous cycle. M. S. Thesis, Michigan State Univer-
sity.

99

Turner, C. W. 1948. Effect of age and season on the
thyroxine secretion rate of white leghorn hens.
Poultry Sci. 27:146.

Van Dyke, H. B. and G. Ch'en. 1933. Production of ovu-
lation by anterior lobe of pituitary of thyroid-
ectomized rabbit. Proc. Soc. EXpt. Biol. and Med.

31:327.

Warwick E. J., C. E. Childs, A. E. Flower and W. E. Ham.
1 8. Ram semen production and characteristics as
influenced by administration of thyr0pr0tein. J.
Animal Sci. 7:198.

Werner, S. C., E. H. Quimby and C. Schmidt. 1949. The
use of tracer doses of radioactive iodine, 1151,
in the study of normal and disordered thyroid func-
tion in man. J. Clin. Endocrin. 9:342.

Wilansky, D. L., L. G. S. Newsham and M. M. Hoffman.
1957. The influence of senescence on thyroid func-
tion: functional changes evaluated with 1151.
Endocrin. 61:327.

Wolff, J. 1951. Some factors that influence the release
of iodine from the thyroid gland. Endocrin. 48:284.

Yeates, N. T. M. 1949. The breeding season of the sheep
with particular reference to its modification. J.
Agr. Sci. 39:1.

Yeates, N. T. M. 1953. The effect of high air tempera-
ture on reproduction in the ewe. J. Agr. Sci.

45 31990

Zalesky, M. 1935. A study of the seasonal changes in the
thyroid gland of the thirteen-lined ground squirrel
with particular reference to its sexual cycle. Anat.
Rec. 62:109.

Zalesky, M. and L. J. Wells. 1940. Effects of low en-
vironmental temperature on the thyroid and adrenal
glands of the ground squirrel, Citellus tridecem-
lineatus. Physiol. Zool. 13:26 .

VIII . APPENDIX

-IOO-

 

lOl

.Wleommm moiwosqmmqmb

 

 

 

 

 

 

 

 

 

 

 

mmoo. omo. mod. om.oa ma.mm ma.mma omosoes
6466. mmo. 4oo. omwoa mmwom mo.oma one
mmoo. oma. oma. om.ma No.6m 6m.mma mom
4466. moo. moo. om.Hm oa.mm mm.ooa 66m
6m66. 646. 446. mm.oa 44.o4 66.o6H m4m
mooo. moo. mmH. Hm.oa mo.om mm.oma own

.m .oo a phase mason m
omoo. 4mo. 4m6. 64.6H om.o4 oo.oo omsno>4
mmoo. 466. moo. o4.m4 ow.om om.oHH mos
omoo. 466. N66. om.ma HH.44 mm.oo mod
oooo. 6H6. 4H6. oo.4H mm.64 66.6o mmz
Hmoo. omo. omo. om.ma 46.64 6o.HoH Hoe
Haoo. oao. oHo. mm.oH o4.o4 mm.664 cos

.6 .oo : pmmmm mesomum
mooo. moo. Hoo. m4.oa mm.m4 oo.mo omssooa
wmo . ~46. omo. omwnwl ma.m4 66.no, mmm
omoo. N46. 646. mo.ma oo.m4 ma.oo mm
4ooo. mmo. 466. Ho.oa ma.m4 ma.oo me
mmao. How. mom. om.6a mo.o4 om.ooH Hos
N666. ooa. moo. mm.4a oo.om mo.mm 644

.m ooo u woman mason w
“.msv “.msv A.ms6 A.ms6 A.orav .oooeH

no.6.a.m .mm .e.m woos mos no.6.mm .s.m unease sesame moonm

\mma \mme mason seem hoom

 

 

4 NHQZHMMd

mqoflpw6q60 panA new oaspmsomaoa mdoanm> pm mopmm soapmnoom oaonhfia

 

102

.604 6&64 no domqaonU

 

 

 

 

 

 

 

 

 

 

4466. 666. 446. 66.64 66.46 66.66 omosota
6666. 646. 446. 66.64 .-. 44466.1:166466 646
6466. 666. o4o. 46.64 66.66 66.66 666
o466. 466. 666. 66.44 46.o6 66.46 666
6666. 646. 666. 44.44 66.66 66.46 666
6666. 446. 646. 46.64 46.66 66.46 o64
.M .66 .. 664.4. 6.44:. 36.1614
o666. 466. 646. o6.44 o6.o6 o6.66 owmno><
66666 646. 666. 66.44 66.66» 66.66 oo4
6666. 466. 666. o6.44 oo.66 66.o6 6o6
6666. 444. o66. 46.64 46.46 66.66 666
6666. 644. o66. 46.44 66.66 66.66 o64
6666. 666. 466. 64.44 o6.66 66.66 446
4666. 646. 466. 46.64 66.66 66.46 664
.M .66 .. 64416144111666.6116 64
6666. 446. o66. 66.46 44.66 64.644 owono>4
6666. 666. 666. 66.66 6o.66 664664 646
6666. 466. 666. 4o.66 46.66 66.664 666
4466. 666. 466. 6o.66 46.46 66.644 666
6466. 466. 666. 66.46 66.66 66.644 666
6466. 666. ooo. 64.66 66.66 66.664 666
.6 .6o 1 7664616666616
4.666 4.686 4.686 4.646 4.6646
66.6.3.6 .64 .4.6 4664 666 66.6.66 .6.6 666466 66646: .66664
\666 \664 64446 6666 soon 66646

IIIIIIIIIIIIIIIIIIIIIIIIdaaaIuuuqIaauHIduuaAuaauqIIIIIIIIIIIIIIIIIIIIIIIIIII

ms64p46qoo pawHH 6mm onspmnomsoa 656446> pm 66p6m no4ponoom.64646na

103

.4OH owmq no wmnqmpnop

 

 

 

 

 

 

 

 

6666. 666. 666. 66.64 46.66 66.46 6666664
4666. 466. 666. 66.6 66.66. 66.66; 66
6646. 664. 664. 46.64 46.64 66.464 666
6666. 664. 466. 66.6 66.46 66.64 64
6666. 666. 466. 66.64 44.64 66.664 646
6466. 666. 466. 66.64 66.64 66.664 666
.6 .66 u 66644 66666.66
4466. 666. 666. 66.64 46.64 64.664 6664664
6666. 646. 646. 66.64 66.64 66.664 66
6666. 446. 646. 46.64 66.66 66.444 46
6466. 666. 466. 64.64 64.64 66.664 644
4666. 646. 666. 64.64 66.66 66.644 644
6666. 646. 646. 66.64 66.64 66.664 464
.6 .66 n 66646.66666164
6666. 666. 666. 64.64 66.66 66.644 6664664
6666. 666. .666. 66.64I1 46.64 66.664 664
6466. 666. 666. 66.64 46.46 66.444 66
6666. 664. 644. 46.64 64.66 66.444 664
6666. 466. 666. 64.64 46.46 66.644 66
6666. 446. 646. 66.64 66.64 66.664 64
.61666 n 66646:66666.64
6.666 6.666 6.666 6.666 6.6646
66.6.6.6 .66 .6.6 6664 666 66.6.66 .4.6 666466 666466 .66664
\666 \666 64466 .6666 6666 66666

 

 

‘Ilrb‘ril-, AI Illlll’! [It I

 
 

-6664 6466.66661666666m66
ma64p46qoo 66669 666 69566966969 636666> 66 mouwm nowpmnoom 6666669

104

 

 

 

 

 

 

 

 

 

 

umoo. m¢o. 0:0. um.¢a um.mm mm.¢w omuno><
mm . mmo. «mo. om.wm :m.n¢ mm.mm sum
«:00. «no. ooo. mH.¢H om.nm ma.mm mom
:noo. mmo. omo. oo.¢a mn.mm mu.mm azm
maoo. umo. mmo. um.¢a oH.mm m~.¢m mam
mmoo. m3 . go . mm .3 mm .mm on .em mi.
#moo. omo. m¢o. Hm.ma nu.mn nm.mm mmm
.mnummuulmmummummmmmumm
mmoo. «ma. omH. mu.ma mm.om mm.mu emanapa
mmoo. Imam. mmmw mmqwm mm.¢m WMJuN: mom
m¢oo. mso. Hmo. mm.ma ¢H.u¢ oo.¢oa emu
emoo. ¢oo. mac. um.ma mm.¢m ma.mu aom
Hmao. mam. mm”. mu.ma oo.mm um.am as:
:moo. mm”. am”. mm.ma :o.mm mm.mu osu
omao. sow. . “ma. oo.ma mu.mm mu.mu mom
oh ad“ I 9””de ago“ #M
Hmoo. :mo. mmo. ma.ma H¢.H¢ om.am omunmpa
¢mn . :mm. mmn. ,mwaw¢ . :::mmqm¢ quwms umm
mmoo. «no. mmo. mm.na mo.am om.maa azm
:ooo. mod. mac. oa.mn mm.~¢ mm.om now
5000. mfio. moo. mu.ma Hu.mm ma.mm a:
uooo. mac. ”Ho. :s.¢a mm.mm mm.uw mom
Haoo. was. mac. Hm.ma mm.a¢ mm.am cam
0% o I n. 3 ON .
A.mav A.wav A.mav A.wuv A.uegv
mu.o.a.m .mu .3.m *ooa mma mu.o.mm .s.m pnmaos pamaos .aaoua
\mma \Mma hafidn bdom 560m 900nm

 

A 0a 0 a scam conufivnooV
mnowpadnoo pnwwq dam mnspwnmmaoa maoflnw> pd mmpwm noaponoom caonhna

105

APPENDIX B

Zero Time Percent Uptake at Various Light Conditions
and 50° F. Temperature

W

 

 

 

 

 

Sheep Hours Percent Sheep Hours Percent
Ident. Light Uptake Ident. Light Uptake
148 4 11.50 16 16 7.04
151 4 10.74 27 16 5.49
WF 4 25.74 182 16 15.49
BS 4 35.64 33 16 10.54
233 4 ‘ggggg 186 16 13.82
Average 4 21.62 Average 16 10.48
369 8 28.46 670 20 13.70
343 8 35.07 618 20 8.53
366 8 13.93 GB 20 7.81
372 8 23.28 BC 20 5.26
337 8 25.18
300 8 30.16
Average 8 26.01 Average 20 8.82
463 12 14.43 707 24 9.16
344 12 19.60 740 24 13.99
489 12 14.44 475 24 14.27
388 12 14.62 204 24 10.27
397 12 20.48 CNT 24 10.28
499 12 18.22 206 24 14.42
Average 12 17.04 Average 24 12.06

 

Average of all ewes at 50° F. 16.45

106

APPENDIX C

Zero Time Percent Uptake at Various Light Conditions
and 90° F. Temperature

 

 

 

Sheep Hours Percent Sheep~ Hours Percent

Ident. Light Uptake Ident. Light Uptake
150 4 25.20 171 16 21.46
N51 4 26.38 115 16 9.50
N52 4 28.73 115 16 19.67
198 4 16.36 24 . 16 18.54
_ 65 1Q 1112

Average 4 24.17 Average 16 19.11
375 8 30.46 654 20 21.54
306 8 23.80 606 20 13.26
305 8 18.82 NT 20 6.06
365 8 24.47 BNT 20 6.96
360 8 38.28 627 20 15.35
313 .8. 321.115 _

Average 8 27.66 Average 20 12.63
459 12 22.98 965 24 8.11
363 12 19.99 743 24 9-77
349 12 16.87 389 24 9.63
357 12 13.33 HNT 24 15.01
335 12 15.50 203 24 10.09
540 11 1211 m 2.1. 11.11

Average 12 22.41 Average 24 10.63

 

Average of all ewes at 90° F. 19.36

107

APPENDIX D

1151 Output Half-time (ms) at Various Light Conditions
and 50° F. Temperature

W

 

 

Sheep Hours TH Sheep Hours Tfi

Ident. Light (days) Ident. Light (days)
148 4 22.617 16 16 12.528
151 4 18.663 27 16 11.182

W? 4 17.291 182 16 3.858
BS 4 8.097 33 16 4.777
233 .51 m 186 E. 1222.6.

Average 4 15.309 Average 16 8.060
369 8 9.401 670 20 13.714
343 8 11.936 CB 20 12.444
366 8 41.124 BC 20 30.499
372 8 12.003
337 8 6.798
300 _§. _9_v.§_1.1 _

Average 8 15.145 Average 20 18.886
463 12 10.948 707 24 6.493
344 12 5.303 740 24 15.711
489 12 6.263 - 475 24 14.873
388 12 17.896 204 24 , 16.150
397 12 8.962 CRT 24 17.908
499 1g .42 206 24‘ 12:334.

Average 12 9.133 Average . 24 15.078

 

Average of all ewes at 50° F. 13.214

108

APPENDIX E

I131 Output Half-time (T%) at Various Light Conditions
and 90° F. Temperature

I”. I. —'--—-_———_——-'-—-—.-

 

 

 

 

Sheep' Hours Tfi Sheep Hours Tfi

Ident. Light (days) Ident. Light (days)
150 4 11.654 171 16 8.021
N51 4 10.793 113 16 10.288
N52 4 6.935 115 16 6.603
198 4 21.798 24 16 6.837

—- 65 1Q .2193

Average 4 12.795 Average 16 7.765
375 8 10.177 654 20 12.601
306 8 12.898 606 20 14.159
305 8 14.034 NT 20 31.990
365 8 12.680 BNT 20 19.471
360 8 7.496 627 20 24.614
513 _§. 316.311.- _

Average 8 11.149 Average 20 20.567
459 12 22.962 965 24 19.962
363 12 5.731 743 24 20.082
349 12 48.088 389 24 20.217
357 12 28.534 HNT 24 16.334
335 12 14.093 . 203 24 15.844
340 11 .2216; _.

Average 12 20.870 Average 24 x 16.892

.11

Average of all ewes at 90° F. 15.197

109

APPENDIX F

Thirty Day Body Weight Gains at Various Light Conditions
and 50° F. Temperature

1.. __--—1.__..__. . -_..- -._._._....

Hours Gain

         

Sheep Hours Gain Sheep-

 

 

Ident. Light (Pounds) Ident. Light (Pounds)
156 4 8.75 16 16 11.50
148 4 8.50 27 16 6.00
151 .4 0.75 182 16 -1.50

WF 4 10.75 33 16 16.00
BS 4 16.50 ABS 16 12.50
235 .1 2.22 186 1.6. .2102

Average 4 8.42 Average 16 8.25
369 8 21.50 670 20 5.25
34H 8 4.00 618 20 2.75
366 8 7.50 LC 20 7.00
372 8 11.00 CB 20 10.25
337 8 5.50 677 20 18.00
300 _§ .9129. BC 3.9. 22152

Average 8 9.75 Average 20 7.12
463 12 9.50 707 24 11.00
344 12 21.75 740 24 0.75
489 12 19.25 475 24 26.75
388 12 13.75 204 24 9.25
397 12 20.00 206 24 14.50
499 11 1110.9. CM 11 11.29

Average 12 16.37 Average 24 14.04

Average 6?_EIIewes at 55‘7F. 10766-

 

 

110

APPENDIX G

Thirty Day Body Weight Gains at Various Light Conditions
and 90° F. Temperature

 

 

 

Sheep Hours Gain Sheep' Hours Gain

Ident. Light (Pounds) Ident. Light (Pounds)
150 4 2.00 171 16 4.50
N51 4 0.00 113 16 7.00
N52 4 -0.50 115 16 6.00
165 4 -4.00 24 16 1.50
198 4 4.25 65 16 0.50

BT J}, -1. __

Average 4 0.00 Average 16 3.90
373 8 13.50 654 20 -3.50
306 8 23.50 606 20 -4.25
305 8 19.00 NT 20 1.25
365 8 7.00 603 20 1.25
360 8 9.00 BNT 20 4.50
313 _§ _§;59_ 627 29, -0.

Average 8 13.08 Average 20 -0.25
459 12 10.00 965 24 10.50
363 12 12.75 743 24 -1.00
349 12 10.25 389 24 13.25
357 12 10.75 HNT 24 8.50
335 12 10.00 203 24 4.25
540 11 11.99. m 2.1 1.2.19.9.

Average 12 10.62 Average 24 7.92

 

 

 

Average of‘EII ewes at 90' P. 5.93

111

APPENDIX.H

Feed Consumption values at Various Light Conditions
and 50° F. Temperature

 

 

 

 

 

 

Sheep Hours Feed Sheep Hours Feed
Ident. Light .Consump.‘ Ident. Light Consump.‘
156 4 6.06 16 16 6.45
148 4 6.39 27 16 4.06
151 4 6.01 182 16 4.83
W? 4 5.83 33 16 6.73
BS 4 5.78 ABS 16 6.31
233 _‘_|; _6_=_§4_ 186 1_6_ 1,112
Average 4 6.15 Average 16 5.31
369 8 8.93 670 20 5.74
34H 8 10.11 618 20 5.40
366 8 8.43 LC 20 6.88
372 8 10.62 CB 20 6.16
337 8 7.52 677 20 6.44
300 _§ Qiil ._ __._
Average 8 8.99 Average 20 6.13
463 12 8.85 707 24 9.26
344 12 10.36 740 24 8.46
489 12 12.56 475 24 7.15
388 12 9.89 204 24 7.38
397 12 10.82 CRT 24 9.03
499 3,2 M 206 24 8&2
Average 12 10.26 Average 24 8.38
Average of-EIIewes at 50* F. ‘7757.-

‘ Values eXpressed as pounds of feed consumed during 30 days
per kilogram of body weight to the 0.73 power.

 

 

 

 

112

APPENDIX I

Feed Consumption Values at Various Light Conditions
and 900 F. Temperature

 

 

 

 

Sheep Hours Feed Sheep Hours Feed
Ident. Light Consump.‘ Ident. Light Consump.‘
150 4 5.61 171 16 4.25
N51 4 5.13 113 16 4.03
N52 4 5.60 115 16 2.89
165 4 4.85 24 16 5.14
198 4 5.21 65 16 3.99
ET ‘1 5.1.6.2 _ .—
Average 4 5.34 Average 16 4.06
375 8 7-35 654 20 4.19
306 8 10.62 606 20 4.83
305 8 10.23 603 20 5.46
365 8 8.67 BNT 20 5.95
360 8 8.31 627 20 5.14
313 Q 2112 ._. ____
Average 8 9.06 Average 20 5.12
459 12 11.30 965 24 8.05
363 12 11.17 743 24 7.58
349 12 11.31 389 24 11.28
357 12 14.34 HNT 24 10.55
335 12 9.71 203 24 9.40~
540 12. 11.1“»: m 2.1 1912:».
Average 12 11.58 Average 24 9.60
Average of all ewes at 90'7F} ‘ 7.62-‘-

‘ Values expressed as pounds of feed consumed during 30 days
per kilogram of body weight to the 0.73 power.

113

APPENDIX J

Feed Efficiency Indices at Various Light Conditions
and 50° F. Temperature

 

~—
r

 

 

 

$61.11;. E12111: Index’ I262: . £12111: Index“
156 4 1.44 16 16 1.78
148 4 1.33 27 16 1.48
151 4 0.12 182 16 -0.31
NP 4 0.90 33 16 2.38
'38 4 1.86 ABS 16 1.98
233 1 1.11 186 15 1.11
Average 4 1.34 Average 16 1.46
369 8 2.41 670 20 0.91
344 8 0.40 618 20 0.51
366 8 0.90 LC 20 1.02
372 8 1.04 CB 20 1.66
337 8 0.73 677 20 2.79
300 §. 1:118. __ __
Average 8 1.09 Average 20 1.38
463 12 .l.07 707 24 1.19
344 12 2.10 740 24 0.09
489 12 1.53 475 24 3.74
388 12 1.39 204 24 1.25
397 12 1.85 CNT 24 2.44
499 1g 1‘24 206 24, ;&gg
Average ‘12 1.58 . Average 24 1.72

Average of‘EII ewes at 50375: ‘I743-

 

 

‘ Values expressed as pounds of gain per pound of feed con»
sumed per kilogram of body weight to the 0.73 Power.

APPENDIX K
Feed Efficiency Indices at Various Light Conditions

and 90° F. Temperature

114

.

 

 

 

Sheep Hours OSheep Hours
Ident. Light Index’ Ident. Light Index’
150 4 0.36 171 16 1.06
_N51 4 0.00 113 16 1.74
N52 4 0.09 115 16 2.08
165 4 . -0.10 24 16 0.29
198 4 -0.77 65 16 0.12
131‘ ‘1 9122 _... _...
Average 4 0.05 Average 16 1.06
375 8 1.84 654 2O -O.83
306 8 2.21 606 20 ~0.88
305 8 1.86 603 20 0.23
365 8 0.81 BNT 20 0.76
360 8 1.08 627 20 -0.15
313 Q. 9121 .__ .___.
Average 8 1.42 Average 20 -0.17
459 12 0.88 965 24 1.30
363 12 1.14 743 24 -0.13
349 12 0.91 389 24 1.17
357 12 0.75 HNT 24 0.81
335 12 1.03 203 24 0.45
340 12 .0_e.§.§ FM‘ 2‘1 1:12
Average 12 0.93 Average 24 0.79
Average (Ti aIl ewes at W 0769—

‘ Values expressed as pounds or gain per pound of feed con-
sumed per kilogram of body weight to the 0.73 power.

115

APPENDIX L

Water Consumption Values at Various Light Conditions
and 50° F. Temperature

 

 

Sheep Hours Water Sheep Hours Water
Ident. Light Consump.‘ Ident. Light Consump.’
156 13.59 16 16 12.06
148 4 10.96 27 16 11.98
151 4 11.17 182 16 11.42
WF 4 19.17 33 16 17.79
BS 4 13.54 ABS 16 13.49
235 1 111.22. 186 19. .2112
Average 4 13.28 Average 16 12.57
369 8 16.16 670 20 11.87
34H 8 19.22 618 20 8.98
366 8 14.61 LC 20 12.63
372 8 16.86 GB 20 12.56
337 8 15.99 677 20 10.76
500 .61 11mg BC .22 .6122
Average 8 16.23 Average 20 10.58
463 12 13.30 707 24 12.90
344 12 17.03 740 24 12.67
489 12 21.22 475 24 13.23
388 12 16.50 204 24 12.25
397 12 17.58 CRT 24 15.61
499 12. 16.111 206 .21 12.15.:
Average 12 16.99 Average 24 13.88

 

Average of all ewes at 508 F.

 

‘ Values expressed as pounds of water consumed during 30
days per kilogram of body weight to the 0.73 power.

1332——

116

APPENDIX,N

Water Consumption Values at Various Light Conditions
and 90° F. Temperature

 

 

 

 

 

Sheep— Hours Water Sheep Hours Water

Ident. Light Consump.‘ Ident. Light Consump.‘
150 4 18.03 171 16 12.40
N51 4 15.88 113 16 14.59
N52 4 17.34 115 16 13.37
165 4 15.97 24 16 21.69
198 4 20.47 65 16 15.65

22 1 12.12 ’ _

Average 4 17.57 Average 16 15.54
375 8 18.16 654 20 14.53
306 8 22.34 606 20 12.79
305 8 30.30 NT 20 12.74
365 8 20.46 603 20 13.34
360 8 20.51 BNT 20 20.62
313 8. 22.122 627 .229 1131.61

Average 8 22.62 Average 20 15.45
459 12 '28.87 965 24 17.01
363 12 26.20 “743 24 15.43
349 12 31.57 389 24 24.60
357 12 37.00 HNT 24 28.94
335 12 23.98 203 24 22.05
340 12. 11.21- m 2.1 21.12

Average 12 29.82 Average 24 22.09

Average 01—511 ewes at 90*F. 1KE2§7_-

' Values expressed as pounds of water consumed during 30
days per kilogram of body weight to the 0.73 power.

117

APPENDIX N

Respiration Rates at Various Light Conditions
and 50° F. Temperature

 

 

 

' Sheep Hours Resp. Sheep Hours Resp.
Ident. Light Rate‘ Ident. Light Rate‘
156 4 42.0 16 16 72.8
148 4 56.8 27 16 85.2
151 4 66.8 182 16 37.6
WF 4 95.0 33 16 78.4

BS 4 88.4 ABS .16 61.2
233 ‘i 2212 136 .115. 3119.
Average 4 65.7 Average 16 61.5
369 8 40.4 670 20 39.2
34H 8 40.4 618 20 37.2
366 8 45.6 LC 20 36.0
372 8 47.2 CB 20 35.6
337 8 42.0 677 20 34.4
500 2 12.2 BC 22 2212
Average 8 44.1 Average '20 34.7
463 12 47.6 707 24 43.6
344 12 39.6 740 24 42.4
489 12 54.4 475 24 34.0
388 12 40.0 204 24 32.0
397 12 69.6 CNT 24 43.2
499 12, 42,3 206 24 11:6
Average 12 49.4 Average 24 37.8
Average air-3'11; ewes at W m

 

 

 

' Values are reported as flank movements per minute.

APPENDIX 0

Respiration Rates at Various Light Conditions
and 90° F. Temperature

118

 

 

 

 

Sheep Hours Resp. Sheep Hours Resp.
Ident. Light Rate‘ Ident. Light Rate‘
150 4 118.0 171 16 93.4
N51 4 204.4 113 16 136.2
N52 4 236.4 115 16 136.0
165 4 134.4 24 16 110.8
198 4 139.6 65 16 130.8
M 1 2.12.2 _ '
Average 4 174.6 Average 16 121.4
375 8 148.8 654 20 120.0
306 8 152.0 606 20 142.0
305 8 160.8 NT 20 84.8
365 8 158.8 603 20 120.0
360 8 150.8 BNT 20 110.4
313 §. 1.13.1.9. 62? 29 19112
Average 8 153.2 Average 20 113.1
459 12 128.0 965 24 97.2
363 12 136.0 743 24 204.8
349 12 153.2 389 24 177.2
357 12 148.8 HNT 24 138.8
335 12 154.0 203 24 149.6
340 1; 14 .2 FNT 24. lfilgé
Average 12 144.5 Average 24 153.2
Average 6?_5117ewes at 90F—F. ~14430

‘ Values are reported as flank movements per minute.

 

 

 

APPENDIX P
Rectal Body Temperatures at Various Light Conditions

and 50° F. Temperature

119

 

 

 

 

Sheep Hours Temp. Sheep Hours Temp.
Ident. Light (° F.) Ident. Light (° F.)
156 105.10 16 16' 102.75
148 4 102.86 27 16 102.95
151 4 103.17 182 16 102.19
hr 4 103.67 33 16 102.82
BS 4 103.58 ABS 16 102.69
233 1 121.21 186 12 192.23
Average 4 103.23 Average 16 102.60
369 8 102.65 670 20 102.77
34H 8 102.77 618 20 102.32
366 8 102.79 LC 20 102.85
372 8 102.79 CB 20 102.84
337 8 103.43 677 20 102.57
300 2 123.22 BC 22 12222
Average 8 102.91 Average 20 102.70
463 12 102.79 707 24 102.91
344 12 103.87 740 24 103.32
489 12 103.36 475 24 102.69
388 12 103.54 204 24 103.11
397 12 103.64 CNT 24 103.23
499 ;g 10 .2 206 g4 195;;;
Average 12 103.40 Average 24 103.06
Average of all ewes at 50° F. 102.98

APPENDIX Q
Rectal Body Temperatures at Various Light Conditions

and 90° F. Temperature

120

 

 

 

Sheep Hours Temp. Sheep Hours Temp.

Ident. Light (° F.) Ident. Light (° F.)
150 4 103.61 171 16 102.50
N51 4 104.75 113 16 103.47
N52 4 104.13 115 16 103.23
165 4 104.08 24 16 103.48
198 4 104.58 65 16 103.41

HT 4, 104. __

Average 4 104.29 Average 16 103.21
375 8 104.90 654 20 103.64
306 8 104.03 606 20 103.96
305 8 104.40 NT 20 104.03
365 8 104.77 603 20 104.49
360 8 104.77 BNT 20 103.62
313 2 193.29 627 29 193189.

Average 8 104.44 Average 20 103.93
459 12 104.83 965 24 103.66
363 12 104.76 743 24 103.80
349 12 103.93 389 24 103.54
357 12 105.30 HNT 24 104.30
335 12 103.47 203 24 103.87
348 12 193.29 m 21 19122

Average 12 104.35 Average 24 103.94

Average of all ewes at 90° P. 104.06