Effect of administering oxytocin or cloprostenol in the periovulatory period on pregnancy outcome and luteal function in mares.

Abstract Mares ( n =37) were treated from 4 h after breeding through 2 days post-ovulation with oxytocin or cloprostenol. Oxytocin (20 units i.m.) was administered every 6 h and cloprostenol (250 mcg i.m.) daily. Luteal function was impaired for several days following treatment, however, lower progesterone levels among cloprostenol treated mares in this study did not result in decreased pregnancies. Pregnancy outcome at 15 days post-ovulation was not different between the oxytocin (13/18) and cloprostenol (13/19) treatment groups, respectively ( P =0.80). The results of this study indicate cloprostenol can be used to treat post-breeding mares through the second day following ovulation without decreasing pregnancy outcome.