The efficacy of ram introduction, GnRH administration, and immunisation against androstenedione and oestrone for the induction of oestrus and ovulation in anoestrous post-partum ewes

Abstract

Four treatments, designed to increase plasma concentrations of LH, were assessed for efficacy at inducing oestrus and ovulation in anoestrous progestagen-pretreated Merino ewes that were 20-37 days post partum during the ovulatory season. The treatments involved the introduction of rams to ewes that had been isolated from rams, GnRH administration, and immunisation against androstenedione or oestrone. Ram introduction resulted in a higher (P<0.001) proportion of ewes showing oestrus and ovulating within 7 days ( 16 19 ewes, flock R-+) than in ewes having continuous contact with rams ( 4 20 ewes, flock R++). Treatment with GnRH (125 ng/h s.c. for 7 days) inhibited the ram effect on the number..