J. Anim Sci.
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J. Anim Sci. 1965. 24:536-540.
© 1965 American Society of Animal Science
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Estrous Cycle Synchronization and Fertility of Gilts Fed Progestational and Estrogenic Compounds1

W. G. Pond, W. Hansel, J. A. Dunn, R. W. Bratton and R. H. Foote

Cornell University, Ithaca, New York2

Abstract

Eighty-five Yorkshire and Berkshire x Yorkshire gilts were used in three experiments to determine the effect of the addition of a progesterone or estrogen derivative to the feed on the estrous cycle and on subsequent fertility. In experiment 1 the addition to the ration of 0.66 or 1.1 mg. of AMP per kg. of body weight for a 15-day period was effective in inhibiting estrus in all gilts during the feeding period. Twenty-one of 22 treated gilts showed signs of estrus within 1 week after hormone withdrawal. Some of the gilts in each group slaughtered 2 or 4 days following artificial insemination had a high incidence of cystic ovarian follicles, especially gilts on the 0.66 mg. level. The estrous cycle was synchronized to some degree at the second cycle following hormone withdrawal (21- to 33-day cycles). Conception at this estrus using natural service was 83.3%. Average litter size for the six gilts that farrowed in each of the control, 0.66-mg. and 1.1-mg. groups was 8.7, 10.2 and 7.8 live pigs, respectively.

In experiments 2 and 3 the feeding of 16 mg. of MEE per gilt daily for 9 days, followed by feeding 1.32 mg. of MAP per kg. of body weight daily for 9 days, inhibited estrus in 29 of 31 gilts. Treated gilts showed typical signs of estrus, including swollen vulvas and behavioral changes, 3 to 8 days after hormone withdrawal in experiment 2 and 4 to 10 days in experiment 3. However, 2 of 11 treated gilts in experiment 2 and 5 of 20 in experiment 3 refused to accept the boar. First service conception of mated gilts was 81.8% for controls and 77.8% for treated gilts in experiment 2 and 100% for controls and 93.3% for treated gilts in experiment 3. Corresponding average litter sizes (live+stillborn pigs) were 8.1 and 8.9 in experiment 2 and 10.4 and 11.7 in experiment 3.

Footnotes

1 The authors wish to thank J. R. Jones, R. W. Gardner and H. VanBlake for their assistance in collecting data; G. Kiger, R. Carpenter and H. Perrine for feeding and care of the animals; R. G. Zimbelman. The Upjohn Co., Kalamazoo, Michigan, for providing 6-methyl-17-acetoxyprogesterone; and G. E. Short, G. D. Searle and Co., Chicago, Illinois, for providing the 17{alpha}-acetoxy-6-methylpregna-4, 6-dien-3, 20-dione (SC 10363) used in these studies.

2 Department of Animal Husbandry.






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Copyright © 1965 by the American Society of Animal Science.