Hormonal Control of Reproductive Activity in the Cycling and Anestrous Ewe1

Abstract
A single injection of progesterone in macrocrystalline suspension inhibited estrus and follicular growth in the cycling ewe for a period of 12 to 16 days. The duration of inhibition depended upon the stage of the breeding season when the treatment was administered. In the anestrous ewe, the optimum interval necessary between the injection of progesterone suspension and PMS to induce follicular growth, ovulation, and estrus was 16 days. Approximately 50% of the anestrual ewes treated with progesterone-PMS came into estrus and 37.5% of these lambed following service at the induced estrus. Eighty-seven percent of the anestrous ewes administered 200 µg. of macrocrystalline estradiol 30 hours after the PMS injection exhibited estrus, but only 28.5% of the ewes serviced produced lambs. Although 50 to 200 µg. of the sodium salt of estradiol administered 30 hours after PMS did not influence the incidence of estrus, it definitely enhanced fertility. Five of six ewes serviced following progesterone-PMS-sodium salt of estradiol treatment produced lambs. Ewes that lambed during October were successfully bred 40 to 60 days later while still milking. Copyright © . .