Effect of timing of injection with pregnant mare's serum gonadotrophin on fixed-time artificial insemination of seasonally anoestrous ewes

Abstract

SUMMARYEffect of timing of pregnant mares's serum gonadotrophin (PMSG) injection combined with a progestagen-impregnated vaginal sponge on fixed-time artificial insemination with fresh, undiluted semen during the nonbreeding season was investigated. PMSG injection 2 days before sponge removal (group A) caused significantly earlier oestrus than injection at the time of sponge removal (group B). Lambing percentages in a total of 320 ewes after fixed-time insemination at 36 h (64·1%) and 48 h (47·2%) in group A, and 48 h (59·5%) and 60 h (39·5%) in group B were not significantly different from those resulting from ‘at oestrus’ insemination (500% and 511% in groups A and B, respectively). The present results indicate that the optimum time for fixed insemination may depend upon the time of PMSG injection associated with progestagen treatment.