HORMONAL INDUCTION OF OVULATION AND SUBSEQUENT FERTILITY IN ADULT CYCLING EWES*

Adult cycling ewes of Nali breed were treated with LHRH and Proges terone + PMSG to see their effects on ovulation rate, estrous behaviour and fertility. 4 ewes out of 12 from the control group were laparotomi zed and the remaining 8 were subjected to natural breeding. The second group of 12 ewes was treated with 300 ug of LHRH on day 16 of the estrous cycle and 11 were laparotomized and 8 were bred. In the third group, B ewes were treated with 10 mg. Progesterone daily for 14 days and 1000L.U. of PMSG on progesterone withdrawal and three ewes were laparotomized and four naturally bred. In the fourth group, 8 ewes were treated with 25 mg. progesterone on day 0,7 and 14 of the estrous cycle and 750 1.U. PMSG was administer ed on day 7 or 14 with two laparotomized and four bred. A repeat trial was conducted in group 3 with 12 ewes half of which received 1000 J.U. and the rest half 1500 J.U. PMSG. All the 12 ewes in this group were naturally bred including the 6 laparotomized ones. There was suppression of overt oestrus in all the treated groups, the maxi mum suppression being observed in group 3. Ovulation was 100% in the progesterone treated group (3 & 4) and 81.8% in the LHRH treated group but there was no lambing in group 3 and only 50% in group 4 against 62% in group 2 and 66.7 in group 1. Oestrous duration and cycle length was decreased in LHRH treated group and increased in progesterone treated group in comparison to control. Ovulation time from onset of oestrus was 47 and 51 hours respectively in group 3 and 4 in comparison to similar values of 28 hours in group 1 and 2. Superovulation was not detected in any of the treated groups.