CONTROL OF ESTRUS, OVULATION AND FERTILITY IN RELATION TO ARTIFICIAL-INSEMINATION IN THE ANGORA GOAT

Purebred and crossbred Angora does (792) were used in an artificial insemination (AI) program. Does were treated with intravaginal pessaries containing 20 mg Cronolone or with a single i.m. injection of 100 .mu.g of the prostaglandin analog Estrumate (I.C.I.) to control the time of estrus or they remained untreated. Pessaries were left in situ for 16, 18 or 20 days while Estrumate was given 6-11, 13-16 or 18-20 days after estrus or at unknown times after estrus. After treatment the does were run with harnessed vasectomized bucks and they were inspected for estrus at 12 h intervals. Does in estrus were inseminated 0-2 or 12-14 h after the detection of estrus and each doe received 0.1 ml semen collected by electroejaculation from Angora bucks. Does (232) were treated with and retained pessaries; 167 (72%) were inseminated, of which 82 (49%) kidded. Of 115 does treated with Estrumate at known times, 83 (72%) were inseminated, of which 36 (43%) kidded. Of 151 does treated with Estrumate at unknown times, 72 (48%) were inseminated, of which 40 (56%) kidded. Of 277 untreated does 223 (81%) were inseminated, of which 149 (67%) kidded. Time of AI after the detection of estrus had little effect on kidding performance. In does treated with Estrumate at known times the majority (82%) were in estrus 48-72 h after treatment with no effect of time of treatment on incidence of estrus or on fertility. Estrus after removal of pessaries occurred 12-24 h earlier than after Estrumate and there were effects of duration of insertion of pessaries on time and precision in time of estrus. Estrus occurred earlier and with less precision as the duration increased and there was a suggestion of lowered fertility in does treated for 20 days; this indicated that the dose of Cronolone used in the pessaries was marginal. Treatment depressed fertility but the kidding performance of does treated with pessaries for 16 days and in estrus 36-60 h after removal of pessaries approached that of untreated does (61 vs. 67%).