EFFECT OF EXOGENOUS OXYTOCIN ON ESTROUS-CYCLE LENGTH AND CORPUS-LUTEUM LYSIS IN EWES

The effect of exogenous oxytocin on estrous cycle length and corpus luteum lysis was investigated. A total of 111 ewes was used in 4 separate experiments. The results of experiment 1 showed no significant reduction of estrous cycle length of oxytocin-treated ewes; however, 2 out of 8 ewes experienced new estrus 6 days after the initial one. The results of experiment 2 clearly showed (P<0.05) the luteolytic property of 50 IU of oxytocin when administered at days 1 to 7 of the cycle. The results of experiments 3 and 4 showed that the destruction of the endometrium or uterine ablation (hysterectomy) negated the luteolytic property of oxytocin. It was concluded that the administration of 50 IU of oxytocin daily from days 1 to 7 of the cycle resulted in luteal lysis in ewes and that the luteolytic action of oxytocin was mediated through the endometrium.