147 PREGNANCY RATES OF RECIPIENT ANIMALS FOLLOWING APPLICATION OF A SELECTIVE PROSTAGLANDIN F_2α RECEPTOR ANTAGONIST DURING EMBRYO RECOVERY

Abstract

Companion research presented at this meeting has indicated that addition of a prostaglandin_2α (PGF_2α) receptor (FPr) antagonist to culture medium prevented the detrimental action of PGF_2α on embryo development. The aim of this study was to evaluate addition of an FPr antagonist to the collection medium on pregnancy rates after transfer of bovine embryos to recipient animals. An initial experiment was performed to determine in vitro development of in vivo-derived morula-stage frozen-thawed embryos cultured in KSOM-PVA medium with 1000 nm AL-8810 (Cayman Chemical Inc., Ann Arbor, MI, USA) (AL, n = 94), 1000 nm AL-8810 and 10 ng mL^–1 PGF_2α (Cayman Chemical Inc.) (AL+PGF, n = 94), 10 ng mL^–1 PGF_2α (PGF, n = 94), or serving as controls (CON, n = 91). Embryos remained in their treatment for a 30-h period until blastocyst development was recorded. In a subsequent experiment, embryos were recovered (n = 783) from superovulated donors on Day 7 after artificial insemination with medium containing 1000 nm AL-8810 (AL), 100 nM AL-8810 (AL100), or with vehicle (VEH: 1 mL DMSO; Sigma-Aldrich, St. Louis, MO, USA) in a double blind study. Following collection, embryos were classified by stage and quality, and then transferred fresh to recipients or frozen (ethylene glycol, direct transfer). Frozen embryos, following thawing, were transferred during the subsequent breeding period. Pregnancy rates were determined by ultrasonography (28–35 days post-transfer) and confirmed by calving date. Data were analyzed using the GLIMMIX procedure of SAS (SAS Institute, Inc., Cary, NC, USA). Results from the initial experiment indicated that culture of in vivo-derived bovine embryos in medium containing AL-8810 improved blastocyst development compared to PGF (58.5% v. 45.7%; P = 0.05). In addition, a strong tendency to increase embryo development was observed in AL+PGF compared to PGF treatment group (57% v. 45.7%; P = 0.07). Overall pregnancy rates of fresh and frozen embryos were increased in the AL and AL100 groups (55% and 58%, respectively) compared to VEH (43%; P = 0.009). Since AL treatments did not differ in pregnancy rates, subsequent analysis combined AL and AL100 data. Transfer of frozen embryos collected with medium containing AL-8810 (n = 238) increased pregnancy rates (AL, 45%) compared to embryos recovered without (n = 221) AL-8810 (VEH, 34%; P = 0.01). Transfer of fresh embryos collected with medium containing AL-8810 (n = 241) tended to have increased pregnancy rates (AL, 76%) compared to control (n = 83; VEH, 66%; P = 0.09). Although data collection continues, no abnormalities in calf health, birth weight, or weaning weight have been observed between any treatments. In conclusion, recovery of embryos with flushing medium containing an FPr antagonist improved pregnancy rates after transfer.

Funding was provided by Ultimate Genetics and the Tennessee Agricultural Experiment Station for completion of these studies.