Effect of buserelin acetate at artificial insemination on pregnancy per AI in dairy cows inseminated with sexed semen.

This study determined whether administration of buserelin acetate (BA), a gonadotropin-releasing hormone agonist, during timed artificial insemination (TAI) improves pregnancy per AI (P/AI) of dairy cows inseminated with sexed semen. A total of 116 Girolando cows from three commercial dairy farms were randomly assigned to two treatment groups: Buserelin Group (BG; n = 58) that received 10 µg BA during AI, and Control Group (CG; n = 58) that did not receive an ovulation inducer. All animals were subjected to a standard ovulation-synchronization protocol, with AI performed 48 h after removing the progesterone device. Cyclicity status at the beginning of the protocol and preovulatory follicle (POF) diameter were included as covariates in statistical analysis. No significant difference in P/AI was observed between treatments (22.4% in BG vs. 13.8% in CG; P = 0.11). Exploratory subgroup analyses indicated a numerical tendency toward relatively high P/AI in anestrous cows treated with BA at the beginning of the protocol. Additionally, cows in BG with a POF < 13 mm showed numerically greater P/AI than did those with POF ≥ 13 mm. Overall, BA administration during AI did not significantly improve P/AI in dairy cows impregnated with sexed semen. The subgroup findings should be cautiously interpreted as the study was not specifically designed or powered for these comparisons. Further studies with relatively large populations are warranted to confirm these potential associations.