CERVICAL-DILATION WITH EXOGENOUS OXYTOCIN DOES NOT AFFECT SPERM MOVEMENT INTO THE OVIDUCTS IN EWES

Exogenous oxytocin aids in the transcervical passage of an AI gun into the uterus of ewes, and it may be an effective adjunct to sheep AI pr ocedures. However, the effects of oxytocin on sperm transport and fert ility are unclear. Thus, experiments were conducted to evaluate the ef fects of oxytocin on variables that may affect fertility. In Experimen t 1, five ewes/group received intravenous injections of 0, 50, 100, 20 0 or 400 USP units of oxytocin. Oxytocin enhanced (P < 0.001) uterine entry; the rates were 0% for control, 60% for the 50- and 100-unit dos es, and 100% for the 200- and 400-unit doses. In Experiment 2, five ew es/group received intravenous injections of 0, 50, 100, 200, or 400 US P units of oxytocin, and the effect on uterine contractions was observ ed with a laparoscope. Oxytocin induced myometrial tetany within 2 min . The dose affected (P < 0.05) the duration of tetany, which was 0, 21 , 27, 29, and 41 min for the 0-, 50-, 100-, 200- and 400-unit doses, r espectively. In Experiment 3, either 0 or 200 USP units of oxytocin we re injected intravenously 52 h after removal of progestogen pessaries from 20 ewes. Ewes were inseminated laparoscopically 10 min later with fresh, extended semen (500 x 10(6) sperm cells) into the right uterin e hem. Ewes were slaughtered 20 h after AI, and the numbers of spermat ozoa were determined. Oxytocin did not affect (P > 0.05) the movement of spermatozoa throughout the uterus and into both oviducts. In summar y, oxytocin induced myometrial tetany and permitted the passage of the tip of an AT gun into the uterus. However, oxytocin did not disrupt s perm transport to the oviducts. We conclude that oxytocin-induced cerv ical dilation may be a useful adjunct to transcervical intrauterine AI procedures for sheep.