title: The economic effects of an estrus synchronization protocol using prostaglandin in beef heifers.
abstract: We estimated the effect of estrus synchronization on reproduction, production and economic outcomes in 272 beef heifers randomly allocated to a synchronized Test group or an unsynchronized Control group. The Test group received AI upon estrus detection for 6 days followed by PGF2 treatment of heifers that had not shown estrus by day 6 (PGF/6). In both groups AI was continued for 50 days, followed by a 42-day bull breeding period. Heifers were followed through their second breeding season and until they had weaned their first calves. Synchronization resulted in a reduction in median days to first insemination (8 vs. 11 in the Test and Control groups, respectively, P<0.01) and median days to calving of calves born to AI (14 vs. 20, P=0.04). There was no significant difference in pregnancy rate to the AI period (60.0% vs. 51.8%, P=0.18), final pregnancy rate (82.2% vs. 83.2%, P=0.87) or pregnancy rate to the subsequent breeding season (96.0% vs. 95.0%, P=1.00). Although mean calf weaning mass was not significantly different (207.0 kg vs. 201.4 kg, P=0.32), the total mass of calves weaned in this study was 14,843 kg vs. 13,060 kg and the benefit: cost ratio for synchronization was 2.8. It was therefore concluded that a PGF/6 protocol may affect the total mass of calves weaned by changing days to calving, weaning rate, the ratio of male: female calves born and/or the birth mass of calves.
authors.affiliation: Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa. dietmar.holm@up.ac.za
authors.forename: D E
authors.initials: DE
authors.lastname: Holm
authors.forename: P N
authors.initials: PN
authors.lastname: Thompson
authors.forename: P C
authors.initials: PC
authors.lastname: Irons
mesh_terms: D000818:Animals; D001835:Body Weight; D001947:Breeding / Q000191:economics*; D002417:Cattle / Q000502:physiology*; D015237:Dinoprost / Q000008:administration & dosage / Q000494:pharmacology*; D004973:Estrus Synchronization / Q000187:drug effects*; D005260:Female; D005298:Fertility; D007315:Insemination, Artificial / Q000662:veterinary; D008297:Male; D011247:Pregnancy; D012744:Sex Ratio; D014886:Weaning
chemical_list: D015237:Dinoprost