Investigations on the synchronization of oestrus and ovulation in German Mutton Merino ewes by means of Gonavet and PGF2 alpha analogues

Wolf, R.; Wolf, M.; Richter, A.

Wissenschaftliche Zeitschrift Karl Marx Universitat Leipzig, Mathematisch Naturwissenschaftliche Reihe 39(3): 250-257


Accession: 002144556

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17 German Mutton Merino ewes, aged 1.5-4 yr, were treated with 250 mu g of the PGF2 alpha analogue Oestrophan, blood samples were collected at 2-h intervals from the onset of oestrus, and oestrous ewes were laparotomised. The incidence of oestrus was 76.5%, and oestrus occurred 38-50 h after treatment. The oestrous ewes showed an increase in blood LH concentration immediately after or 2-3 h after treatment, and some of the non-oestrous ewes also showed an LH peak. The av. interval between final treatment and the LH peak was 48.2+or-4.8 h, 8 of the 13 ewes ovulated, with an av. ovulation rate of 1.67, and the remaining 5 ewes had preovulatory follicles. In a 2nd trial, 38 ewes were treated twice with 175 mu g cloprostenol, with an interval of 9 days between treatments, and received 10 mu g GnrH 44 or 48 h later (groups 1 and 2 resp.), or received no further treatment (controls). All ewes exhibited oestrus 45- 51 h after the 2nd cloprostenol injection. In the 2 experimental groups resp., the LH peak occurred 2-4 h and 46 h after the 2nd cloprostenol injection; it was not synchronized in controls. All experimental ewes ovulated vs. 10 of the 13 controls, and there were no significant differences between the 3 groups in ovulation rate (1.75, 1. 54 and 1.60 resp.). In a 3rd trial, 102 ewes which had returned to oestrus in Nov.-Dec. were treated twice with 125 or 175 mu g cloprostenol, at an interval of 9 days, and 53 of the ewes also received an injection of 10 mu g GnrH 35 h after the 2nd cloprostenol injection. For ewes treated or not treated with gonavet and inseminated twice (50-52 h after cloprostenol treatment and again 7 days later), the lambing rate was 143 and 158% resp.