Effects of progestagen, PMSG and artificial insemination time on fertility and prolificacy in Corriedale ewes.

摘要

The aim of the study was to evaluate the effects on fertility and prolificacy of treatment with a progestogen (60 mg MAP or 30 mg FGA administered via intravaginal sponges), followed by 250 IU PMSG or saline at sponge removal, and insemination 48 or60 h later. 120 Corriedale ewes were studied in a 2 X 2 X 2 factorial experiment during the breeding season with 15 females in each group. Each ewe was inseminated in the external os of the 1st cervical fold with 500 X 106 spermatozoa. The overall fertility rate (percentage of inseminated ewes that lambed) after treatment including MAP, FGA, PMSG and saline was 56.6, 56.1, 57.7 and 55.2 respectively, and fertility after insemination at 48 or 60 h averaged 50.9 and 61.8% respectively. The correspondingprolificacy rates (number of lambs per ewe lambing X 100) were 110, 122, 120, 113, 114 and 118%. Insemination at 60 h improved the fertility over insemination at 48 h (P<0.05). There were no significant interactions among progestogen treatments, PMSG andtime of insemination.