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Effect of CIS and Trans Isomers of Clomiphene on Reproductive Performance in Ewes^{1, 2,}

Cornell University, Ithaca, New York 14850

Abstract

Trans-clomiphene injected intramuscularly daily for 16 days in doses ranging from 0.17 mg to 4.5 mg/day did not result in synchronized estrus cycles following withdrawal and had no effect on ovulation rate or fertility. On the other hand, 1.5 mg of cis-clomiphene injected daily for 16 days resulted in 4 of 5 ewes being in estrus within a 48-hr, period at the end of the treatment period. This dose of cis-clomiphene completely blocked ovulation and caused a significant reduction in the number of follicles greater than 4 mm in diameter (P<.01) and a significant increase in the number of services required for conception (P<.01). Doses of .012, .06 and 0.3 mg of cis-clomiphene per day had no effect on the occurrence of estrus, ovulation rate or fertility, except that the dose of .06 mg caused a significant increase in the number of functional corpora lutea (P<.05). Neither isomer of clomiphene stimulated body weight gains or wool growth. However, cis-clomiphene could prove useful if used prior to gonadotropin injections in synchronization techniques designed for inseminating animals at a predetermined date without regard to the occurrence of estrus.

¹ This project was supported by a grant from Hess and Clark, Division of Richardson-Merrell Inc. of Ashland. Ohio.

² The authors are grateful to Mrs. Lois Merrill for valuable technical assistance in conducting this experiment and L. G. Hunt for his expert advice and help in conducting this experiment and Dr. D. E. Hogue for grading the wool samples.

³ Present address: Department of Animal Science, Iowa State University, Ames 50010.

⁴ Department of Animal Science.