Department of Animal Science Florida Agricultural
Mimeograph Series No. 62-2 Experiment Station
EFFECT OF TEMPERATURE ON EARLY EMBRYO SURVIVAL IN GILTS
A. C. Warnick, V. E. Caldwell, H. D. Wallace
and A. Z. Palmer I/
With year-around farrowing, it is important to know the effect of
temperature upon reproductive performance to provide the best environ-
ment for the breeding herd. It is possible that the management could
be modified if high temperatures during the summer months had a harmful
influence on litter size. The objective of this experiment was to com-
pare ovulation rate, conception rate and number of embryos at 25 days
in gilts at 600 F., 900 F. and those at atmospheric temperatures in
shaded pens. Also, some gilts were switched 3 days after breeding be-
tween the two temperatures to determine if time of cooling had an in-
fluence on embryo survival.
Thirty-two Duroc x Landrace gi ts were randomly assigned to one of
the five following groups 10 days following first estrus.
Group I Control (Ample natural shade on pasture)
Group II Heat Heat (Constant temperature room at 90 F.)
Group III Heat Cool (One-half of gilts in II moved to 600 F.
3 days postbreeding)
Group IV Cool Cool (Constant temperature at 600 F.)
Group V Cool Heat (One-half of gilts in IV moved to 900 F.
3 days postbreeding)
The gilts were mated once during early estrus to a Duroc boar that
was kept in the cold room at 600 F. Gilts were killed 25 days after
breeding to obtain counts of the numbers of corpora lutea and number of
normal embryos in the uterus. The gilts were self-fed a ration con-
taining 15% protein as shown in Table I. The gilts weighed approximately
220 Ibs. when the experiment began. The gilts were assigned to their
respective groups beginning on August 23 and continuing through October
20, 1960. The breeding of the gilts continued from August 30 to October
30, 1961. Slaughter dates which terminated the experiment for a par-
ticular gilt ranged between September 24 to November 23, 1960. Rectal
temperatures were taken of the gilts.
L/ Warnick, Associate Physiologist; Caldwell, Graduate Assistant.
Wallace, Animal Husbandman; Palmer, Associate Animal Husbandman;
Department of Animal Science.
COMPOSITION OF RATION
Alfalfa Leaf Meal (17%) 10.0
Ground Whole Oats 20.0
Yellow Corn 56.0
Soybean Oil Meal 12.0
Ground Limestone 0.6
Steamed Bone Meal 0.7
Trace Minerals 0.1
Aurofac 10 0.1
Results and Discussion
One gilt at 900 F. and one at 600 F. returned to estrus before 25
days postbreeding indicating no-temperature effect on conception rate.
These two gilts were rebred and became pregnant but are not included
in the data on embryo number. The average number of corpora lutea at
second estrus was 16.3 in gilts with natural shade, 15.6 in gilts at
900 F. and 14.7 in gilts at 600 F. There was considerable variation in
number of corpora lutea among gilts varying from 12 to 25, so tempera-
ture apparently had no direct effect on number of eggs ovulated.
The average number of embryos and percentage embryonic survival
for gilts in the five groups is shown in Table 2. Gilts kept continu-
ously at 90 F. (Group II) had only 9.4 embryos compared to 14.1 for
gilts in the Heat-Cool sequence (Group 111); however, there was con-
siderable variation within treatment groups. These differences in
embryo number among the groups were not statistically significant.
The percentage embryonic survival based on the number of corpora lutea
shows similar trends. It is interesting that the control gilts (Group
I) kept in a well-shaded area had approximately the same number of em-
bryos as those kept continuously at 60 F. (Group IV).
EMBRYONIC SURVIVAL TO 25 DAYS AT DIFFERENT TEMPERATURES
Group No. gilts Avg. No. Avg. No. %
C. L.* Embryos Survival**
I Control with shade 6 16.3 12.5 77
It Heat Heat 5 14.6 9.4 64
Ill Heat Cool 7 16.0 14.1 88
IV Cool Cool 6 14.8 12.8 86
V Cool Heat 6 14.8 11.2 75
* Corpora lutea represents eggs ovulated.
** % = Total No. Embryos
Total No. C. L.
If the data from the gilts in Groups II through V are combined,
one can compare sequence of heating or cooling on embryo survival, Table
3. There was no difference in number of embryos, 12.0 vs. 12.2, for
gilts at 600 F. and 900 F., respectively, up to 3 days postbreeding. How-
ever, gilts kept at 900 F. from 3 to 25 days postbreeding had only 10.4
embryos compared to 13.5 for the gilts kept at 600 F. It would appear
that heating exerts some harmful physiological effect after the embryo
enters the uterus at 3 days rather than up to time of fertilization or
shortly thereafter. This is different than ewes where high temperature
has a deleterious effect on embryo survival before 3 days postbreeding
(Alliston and Ulberg, 1960).
EFFECT OF A CONTROLLED TEMPERATURE ON NUMBER OF EMBRYOS IN GILTS
Period I* 600 F. 900 F. Avg,
Period 2** 600 F. 12.8 14.1 13.5
900 F. 11.2 9.4 10.4
Avg. 12.0 12.2
* Period 1--14 days (Prior to 3 days postbreeding).
** Period 2--22 days (3 to 25 days postbreeding).
The average rectal temperatures of gilts taken at approximately
2:00 P.M. on the same day was 102.2, 102.8 and 103.3 degrees Farenheit
at 600 F., natural shade and 900 F., respectively. The average body
temperature for the pig is 102.50 F. with a range from 101.6 to 103.6
according to Dukes (1947).
A comparison was made of the reproductive efficiency with 32 Duroc
x Landrace gilts at 600 F., 900 F. and at prevailing outside tempera-
tures with natural shade between August 23 and November 23, 1960. The
gilts were assigned to their respective locations 10 days after their
first estrus and bred once at their second estrus to a fertile boar and
killed 25 days later to determine ovulation rate and number of embryos.
Temperature had no influence on number of eggs ovulated or conception
rate. Prior to 3 days after breeding, there was little influence of
temperature on number of embryos. However, gilts kept at 900 F. from 3
to 25 days postbreeding had 3.1 fewer embryos than those at 600 F. Gilts
kept on pasture with ample natural shade had nearly as many embryos as
those gilts kept at 600 F.
These data suggest the importance of keeping the breeding female in
the coolest part of the farm particularly after breeding during the hot
Alliston, C. W. and L. C. Ulberg.
perature on early pregnancy
Journal of Animal Science.
1960. The influence of ambient tem-
loss as determined by embryo transfer.
Dukes, H. H. 1947. The Physiology of Domestic Animals. Comstock Pub-
lishing Company, Inc. Ithaca, New York.