EFFECT OF OXYTOCIN ADMINISTRATION ON THE OESTROUS CYCLE OF UNILATERALLY HYSTERECTOMIZED HEIFERS

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Abstract
The effect of oxytocin administration on the estrous cycle was studied in 16 uterine-intact and 32 surgically prepared unicornual heifers. Unilateral hysterectomy was performed on Day 3 of the estrous cycle and oxytocin or an equivalent volume of physiological saline was administered daily from Day 3 to Day 7 or 8. Oxytocin produced significantly shorter estrous cycles in the intact heifers and in the unicornual heifers with the retained uterine horn adjacent to the CL, but not in the unicornual heifers with the retained horn opposite to the CL. These results strongly suggest that at least part of the effect of oxytocin is exerted through local, utero-ovarian channels. A unilateral effect of the uterus on the CL was demonstrated in unicornual heifers that did not receive oxytocin. The estrous cycles were extended and the CL persisted when the retained horn was opposite to the CL, but not when the retained horn was adjacent to the CL.