Reduction of sperm transport in ewes by superovulation treatments

Abstract

Estrus was synchronized in ewes by withdrawal of an intravaginal progestagen sponge after 12 days or injection of PG[prostaglandin]F-2.alpha. on Day 11 of the estrous cycle. Ewes were treated with no hormone; 1500 IU PMSG [pregnant mare serum gonadotropin] 48 h before sponge removal or PG injection; or 24 mg porcine pituitary FSH in multiple injections commencing 48 h before sponge removal or PG injection, in a 2 .times. factorial design. Ewes were inseminated with 0.2 ml fresh undiluted semen into the neck of the cervix 48 h after sponge removal or PG injection. Normally cyclic ewes were similarly inseminated within 12 h of observed standing estrus. At 24 h after insemination 1 uterine horn and 1 oviduct were flushed for recovery of spermatozoa and ova. When compared with naturally cyclic ewes, PG synchronization resulted in a marked reduction in the numbers of spermatozoa recovered (P < 0.05), and sponge synchronization led to a small, non-significant, reduction. Within the synchronized ewes, PMSG and FSH resulted in an equivalent superovulatory response, but there was a marked reduction in sperm recovery when compared with unstimulated animals (P < 0.01), with the greatest reduction attributable to PMSG treatment. Spermatozoa were recovered from fewer ewes treated with PMSG than with FSH (P < 0.05). Despite the observed impairment of sperm transport, a high fertilization rate was observed within each group and there were no differences between treatments. [Failure of fertilization after superovulation is a major factor limiting the success of embryo transfer in sheep.].