Reduction of sperm transport in ewes by superovulation treatments

Abstract

Oestrus was synchronized in ewes by (a) withdrawal of an intravaginal progestagen sponge after 12 days or (b) injection of PGF-2α on Day 11 of the oestrous cycle. In addition, ewes were treated with (a) no hormone, (b) 1500 i.u. PMSG 48 h before sponge removal or PG injection, or (c) 24 mg porcine pituitary FSH in multiple injections commencing 48 h before sponge removal or PG injection, in a 2 x 3 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 oestrus. At 24 h after insemination one uterine horn and one 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.