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Increased Ovulation Rate of Adult Ewes Treated with Anti-Bovine LH Antiserum During the Normal Breeding Season

US Department of Agriculture and Cornell University, Ithaca, NY³

Abstract

Adult Suffolk ewes (n=14) were treated on d 10 of the estrous cycle with anti-bovine luteinizing hormone (LH) antiserum. Control ewes (n=10) were treated with normal horse serum. Estrous behavior and the number of corpora lutea and ovarian follicles were examined at the subsequent estrous cycle. Daily plasma concentrations of progesterone (P₄), follicle stimulating hormone (FSH) and estradiol were determined before and after treatment. Ewes treated with antiserum had a higher (P<.05) ovulation rate (2.7 ± .2) than did controls (2.1 ± .1). No differences were found in the numbers of large (> 5 mm) or small (< 5 mm) follicles between treatment groups. Estrus was delayed (P<.025) approximately .6 d in ewes treated with antisera. Immunoreactive FSH increased (P<.05) within 1 d after treatment and remained higher than the controls for 5 d. Peak estradiol concentrations occurred on d 17 for treated ewes compared with peak concentrations on d 15 or 16 for control ewes. The P₄ concentrations were generally less (P<.025) in treated ewes throughout the luteal phase of the treatment cycle. These data demonstrate that ovulation rate is increased in ewes treated with LH antiserum. The marked increase in plasma FSH suggests a possible mechanism whereby ovulation rate is enhanced.

¹ Present address and reprint requests: Western Region, Agricultural Research Service, USDA, U.S. Sheep Exp. Sta., Dubois, ID 83423.

² The technical assistance of R. R. Saatman, W. G. Gardner and J. P. Miller is gratefully appreciated. The authors thank Dr. Doug Bolt for the FSH antiserum. The secretarial help of Sue Hawk, Helen Dormady, Vicki Gunter and Pat Wells is also acknowledged. Mention of trade names or companies does not constitute an implied warranty by USDA or the authors. Some of these data previously presented to the Society, for the Study of Reproduction, July 23–27, 1984, Laramie, WY.

³ Dept. of Physiol., New York State College of Vet. Med.