Control of ovulation and fixed time insemination in heifers following cloprostenol
Roche, J.F.
Veterinary Record 100(22): 468-470
1977
ISSN/ISBN: 0042-4900 PMID: 327675 Document Number: 117497
Heifers were given 2 injections of 500 mu g cloprostenol (Estrumate, ICI), 11 days apart, and their reproductive tracts were recovered at slaughter. The percentage of heifers that had ovulated 72, 78, 92 and 96 h after the 2nd injection was 0, 31, 61 and 95 resp. Injection of synthetic LHRH 48 h after the 2nd injection of cloprostenol significantly advanced the time of ovulation in animals slaughtered 78 h after the 2nd cloprostenol injection. Insemination 48, 60 or 72 h after cloprostenol treatment resulted in lower CRs (10-29%) than 2 inseminations 60 and 72 or 48 and 72 h after treatment (50-53%). The CR to insemination at the observed oestrus was 46-60% for untreated controls and 66% for heifers treated with cloprostenol. Use of LHRH did not increase the CR to a single insemination 72 h after treatment with cloprostenol.