Oxytocin increases pregnancy rates after fixed time artificial insemination in Kazak ewes.

Abstract

It is probable that reduced pregnancy rates in ewes after fixed time artificial insemination (FTAI) is attributable, in part, to the reduced number of normal spermatozoa that colonize the oviduct. Administration of oxytocin stimulates both cervical dilation and uterine/oviductal contractility. The hypothesis that oxytocin can enhance sperm transport into the uteri and the oviducts, and thereby increase pregnancy rates, was tested in the present study. Oestrus was synchronized in 199 multiparous Kazak ewes using intravaginal flurogestone-impregnated sponge. The sponge was left in the vagina for 12days followed with an injection of 330IU of eCG at sponge removal. Each ewe was intracervically inseminated twice at 50hr and 62hr after the removal of sponges using an insemination catheter containing 0.25ml of diluted semen. Semen was collected from seven Texel rams and all the ejaculates were pooled and diluted in ultra-high temperature-treated commercial skimmed milk without (Control group, 0.05ml of saline per mL milk, n=144) or with oxytocin supplement (Oxytocin group, 0.5U of oxytocin per ml milk, n=55). Pregnancy status was determined by transabdominal ultrasound examination 45days after insemination. Lambing performance was recorded at delivery. Significant differences were observed between the Oxytocin group and the Control group in terms of the pregnancy rate and the fecundity rate (85.5% and 92.7% versus 68.8% and 72.9%, respectively). In conclusion, low dose oxytocin supplementation of semen extender significantly increased pregnancy and fecundity rates in oestrus-synchronized Kazak ewes after FTAI.