144 PREGNANCY RETENTION OF BOVINE RECIPIENTS FOLLOWING TRANSFER OF EMBRYOS EXPOSED TO A PROSTAGLANDIN_2α RECEPTOR ANTAGONIST DURING COLLECTION

Abstract

Increasing efficiency and success of MOET continues to be a goal of researchers and practitioners. Although numerous studies report success in establishing pregnancies, fewer evaluate term development and report number of live calves born. In a previous study, Scenna FN et al. (2008 Reprod. Fertil. Dev. 20, 154) exposed embryos to 3 different medium treatments while being collected from superovulated beef donors on Day 7. Medium treatments consisted of a commercially available medium plus 1 mL of DMSO (Control), commercial medium plus 100 nm of AL-8810 (AL100), or a commercial medium plus 1000 nm of AL-8810 (AL1000). Embryos were evaluated for grade and stage according to IETS guidelines. Embryos (n = 1734 at 6 locations across 13 replicates) were transferred (fresh or frozen in ethylene glycol) by 4 experienced technicians. Pregnancy rates were determined by ultrasonography 28 to 35 days after transfer and were increased in recipients receiving embryos collected in media containing AL100 (65%) and AL1000 (60%) compared with Control (50%; P < 0.05) as previously reported. As a continuum of this research interest, pregnancy retention rates (PRR) of recipient animals receiving embryos exposed to a prostaglandin F_2α receptor antagonist (AL100 or AL1000) during collection or serving as nontreated controls were determined. Pregnancy retention rate was defined as the percentage of animals calving that were diagnosed pregnant at 28 to 35 days after transfer. From this pool of recipient animals, calving information was available to date on 494 confirmed pregnancies (presence of an embryo with a heartbeat). Data were obtained on 192 Control, 108 AL100, and 194 AL1000 recipients and analyzed using generalized mixed model analysis of variance (Glimmix) in SAS (SAS Institute, Cary, NC). Similar to initial pregnancy rates, PRR did not differ between AL100 and AL1000 (89 ± 0.04% and 90 ± 0.03%, respectively; P > 0.10); therefore, these groups were combined (AL) for subsequent analysis of PRR. Regardless of treatment, overall PRR were 88 ± 0.01% for fresh and 85 ± 0.03% for frozen embryos (P > 0.10). Additionally, gestation length (days) was similar between recipient animals receiving Control (282 ± 1.19), AL100 (281 ± 1.30) or AL1000 (281 ± 1.17; P > 0.10). However, addition of AL to collection medium of embryos increased PRR compared with Control (90 ± 0.03% v. 83 ± 0.03%, respectively; P = 0.06). Currently, an interaction was not noted between freezing method and media treatment (P > 0.10). Although collection of data continues, addition of a prostaglandin F_2α receptor antagonist to the collection medium of embryos improves PRR of recipient animals without altering gestation length.