J. Anim Sci.
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J. Anim Sci. 1977. 45:336-341.
© 1977 American Society of Animal Science
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Corpus Luteum function in Ewes Given Estradiol during the Estrous Cycle or Early Pregnancy1

R. J. Kittok and J. H. Britt

Michigan State University2, East Lansing 48824

Abstract

Three experiments were conducted to assess the anti-luteolytic action of a conceptus in ewes given doses of estradiol capable of causing premature regression of the corpus luteum. Ewes given 250 µg estradiol-17ß per day on days 11 and 12 or 12 and 13 following mating to a vasectomized ran had less serum progesterone (ng/ml) on day 14 than did similarly mated control ewes (.4 ± .1 vs 1.9 ± .6; Exp. 1). However, estradiol treatment during these stages caused a decline in serum progesterone in only six of 12 ewes mated to intact rams. Of ewes mated to intact rams in a second experiment, four of eight and one of eight given 125 or 250 µg estradiol per day, respectively, on days 11 and 12 post-mating were pregnant on day 16. Pregnant ewes had higher serum progesterone on day 15 (1.6 ± .7 ng/ml) than nonpregnant ewes (.3 ± .1 ng/ml). In a third experiment, five of 17 ewes mated to intact rams and given 125 µg estradiol on days 11 and 12 were pregnant on day 20. These pregnant ewes had higher serum progesterone on day 14 than ewes similarly mated but not pregnant on day 20 (4.1 ± .3 vs 1.4 ± .3 ng/ml). On days 11 through 20, serum progesterone in estradiol-injected ewes that were pregnant on day 20 did not differ from levels in normal pregnant ewes. The presence of a conceptus in the uterus on days 11 to 13 prevented estradiol-induced luteolysis in some ewes.

Footnotes

1 Published with the approval of the Director of the Michigan Agriculture Experiment Station as Journal Article No. 7234.

2 Animal Reproduction Laboratory, Department of Dairy Science.






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Copyright © 1977 by the American Society of Animal Science.