PSIII-14 Pregnancy rate following fixed time AI in beef cows with or without oxytocin injection.

Abstract Fixed-time artificial insemination (FTAI) protocols are potential tools for the beef industry as they reduce time and labor for estrus detection by inseminating females at a predetermined time to provide a chance for conception on the first day of the breeding season. Our aim for this study was to determine if oxytocin injection at the time of FTAI would impact pregnancy rates in beef cattle. Thirty-three Black Angus based cattle were used. Cows were estrus synchronized used the 7-day Co-Synch+CIDR® (7dCSC) protocol, receiving GnRH and CIDR insertion on Day 0, and prostaglandin F2α (PG) injection and CIDR removal on Day 7 with AI and GnRH injection 66 ± 3 h later. Animals were randomly assigned to receive oxytocin (1.5 cc i.m., 30 USP units) at AI (OXY) or not (CON). Estrus detection patches were placed on all animals at CIDR removal/second PG injection. Along with body condition score (BCS), estrus indicators recorded at AI included estrus patch status (color change or missing), color of vulva mucus membrane (pink vs pale), texture of the cervix (hard vs soft), and the status of insemination (easy vs hard). Pregnancy was determined by transrectal ultrasonography at 62 days after FTAI. Data were analyzed with a mixed model procedure (GLIMMIX) and Pearson correlations using SAS. Pregnancy rate to AI for only those pregnant (83.3 ± 10.8% for CON vs 83.3 ± 15.2% for OXY) as for the total inseminated (40.8 ± 15.5% for OXY vs 66.2 ± 12.4% for CON) was not impacted by oxytocin treatment or body condition score, or number of estrus indicators. The number of estrus indicators was positively related to days post-partum at AI (r=0.47, P< 0.02), but no other correlations were noted. In summary, there were no effects of oxytocin on pregnancy rates to fixed-time AI under the conditions of this study.