Buserelin administered at heat detection or at Artificial Insemination moment effect in Brown Swiss cows` conception rates

The present study aimed to evaluate the effect of the GnRH analog buserelin acetate (SincroforteTM, Ouro Fino, Cravinhos, SP, Brazil) used at the time of heat detection or at the artificial insemination (AI) moment, on the conception rate in Brown Swiss cows, with ranging daily milk production of 10 to 15 L. Sixty (60) animals were used, randomly distributed in one of the three groups: Group I (n=20) 0.01mg of buserelin acetate were administered, IM at the moment of heat detection; Group II (n=20) 0.01mg of buserelin acetate were administered, IM at the moment of AI; and, Group III (n=20) were administered 1mL of saline solution, IM at the moment of AI. All cows were inseminated 12 hours after the heat onset (observed twice daily, detected with observation of mount acceptation), by the same technician, using frozen semen from certified breeder. The gestation diagnosis was performed 45 days after the AI by transretal palpation associated to an ultrasonographic examination, performed by a specialized veterinary. The obtained data were analyzed using Fisher`s Exact Test, with 5% of significance level. The conception rate of the group I was 85%* (17/20), of the group II was 65% (13/20) and of the group III was 60%* (12/20). The statistical analyses permit to infer of the superiority tendency observed between group I and group III (*p=0.0776), but no difference were observed between groups II and I or between groups II and III (p>0.1). These results permit to conclude that the administration of buserelin acetate at time of heat detection in Brown Swiss cows lead to an increased conception rate.