Biology of Reproduction, Vol 15, 115-117, Copyright © 1976 by Society for the Study of Reproduction

Increase in Ovulation Rate in Sheep Following Administration of an LHRH Analogue

¹ Reproduction Research Section, University of Melbourne, and Department of Agriculture, Victoria, S. S. Cameron Laboratosy, Werribee, 3030, Australia

A nonapeptide (D-Ser (TBU)⁶-EA^{1 0}; Hoe 766; Hoechst AG), 25 times more potent than LHRH in LH and FSH releasing activity, was administered (2 µg s.c. in 0.5 percent gelatin) to ewes on Day 1 (n=51), Day 12.5 (n=48) or Day 14.5 (n=39) of the estrous cycle (Day 0 = day of estrus). A control group (n=23) was not treated. Ovulation rate at the estrus or time of expected estrus following treatment was increased (P<0.05) in ewes injected on Day 12.5 (1.36) compared to ewes in the control group (1.09) and ewes injected on Day 1 (1.13), but not in ewes (0.05<P<0.10) injected on Day 14.5 (1.29). Less ewes expressed estrus following treatment with Hoe 766 on Day 14.5 (35 percent) than on Day 12.5 (64 percent) or than on Day 1 (90 percent) c.f. Control group (82 percent). These results suggest Hoe 766 may be a useful agent to increase ovulation rates in sheep and support the concept that gonadotropin concentrations in peripheral plasma on Day 12-14 of the ovine estrous cycle may be important in determining ovulation rate at the subsequent estrus.

Note:
ACKNOWLEDGMENTS Drs. R. Humke and J. Sandow of Hoechst AG, Germany kindly made available the supplies of LHRH and Hoe 766. The technical assistance of Peter Langdon, Robert Baxter, Jean Burhop and Enid Pruysers is gratefully acknowledged. The work was supported by grants from the Australian Meat Research Committee and the Australian Wool Research Trust Funds. Our thanks to Lyn Bourke for the typing and to Dr. E. Shepherd of I.C.I. Australia for supplying prostaglandin.