Pregnancy retention of bovine recipients following transfer of embryos exposed to a prostaglandin F₂[alpha] receptor antagonist

Increasing efficiency and success of multiple ovulation and embryo transfer continues to be a goal of researchers and practitioners. Reports of pregnancy rates exist; while few evaluate term development and offspring performance. Previously, Scenna, et al. (2008) exposed embryos to three collection medium treatments while being collected from superovulated, beef donors on day 7. Medium treatments consisted of commercial medium plus 1 mL DMSO (VEH), commercial medium plus 100 nM of AL 8810 (AL100), or a commercial medium plus 1000 nM of AL 8810 (AL1000). Embryos (n = 1,734 at 6 locations across 17 replicates) were transferred (fresh or frozen in ethylene glycol) by five experienced technicians. Pregnancy rates increased in recipients receiving embryos collected in media containing AL100 (65%) and AL1000 (60%) compared to Vehicle (50%; P = 0.0007) as previously reported.As a continuum of this research interest, pregnancy retention rates (PRR) of recipient animals receiving embryos exposed to the above treatments, and performance of resulting offspring was evaluated. Pregnancy retention rate was defined as the percentage of recipients calving that were diagnosed pregnant after embryo transfer. Calving information was available on 910 confirmed pregnancies ot the 1,734 transfers (VEH, n = 294; AL100, n = 267; AL1000, n = 349). Similar to initial pregnancy rates, PRR did not differ between AL100 and AL1000 (95% ± 0.10 and 91% ± 0.02, respectively; P = 0.72); therefore, these groups were combined for subsequent analysis of PRR. Addition of AL 8810 to collection media of embryos increased PRR compared to VEH (92% ± 0.02 vs. 83% ± 0.03, respectively; P = 0.01). Furthermore, a trend was noted for improved average daily gain differences between fresh and frozen embryos (1.13 kg ± 0.03 vs. 1.02 kg ± 0.05, respectively, P = 0.07).Analysis of other production traits (gestation length, sex ratio, birth weight, weaning weight, death loss) revealed no differences due to collection media treatment, transfer type (fresh vs. frozen), or interactions. Therefore, inclusion of a prostaglandin F₂[alpha] receptor antagonist to collection media of embryos increased initial pregnancy rates and subsequent pregnancy retention rates without influencing calf viability or normality.