Sincronização hormonal e seleção de receptoras para Transferência de Embriões em Tempo Fixo (TETF) em bovinos leiteiros e de corte : revisão de literatura

Abstract

Brazil stands out globally in livestock production and in the application of reproductive biotechnologies in cattle, being one of the world's leading producers and commercial suppliers of bovine embryos. One of the main stages of this biotechnology is embryo transfer, in which embryos obtained from genetically superior donors and sires are transferred to recipient females responsible for maintaining pregnancy until parturition. Therefore, proper synchronization and careful selection of recipient females, as well as the choice of an appropriate hormonal protocol, are essential, considering the distinct metabolic demands of beef and dairy cattle. This study aimed to analyze the scientific literature on the main hormonal protocols used for the synchronization of beef and dairy cattle recipients for fixed-time embryo transfer (FTET), as well as the criteria adopted for recipient selection. The reviewed literature indicates that the most suitable protocols for beef cattle include two prostaglandin administrations, equine chorionic gonadotropin (eCG) associated with estradiol cypionate (EC) at progesterone (P4) implant removal, and the use of gonadotropin-releasing hormone (GnRH). For dairy cattle, the best results were reported with protocols based on the MMSINCRO strategy. Regarding recipient selection, females with a body condition score (BCS) between 3.0 and 3.5, good health status, heifers, and the presence of a highly vascularized corpus luteum achieved the best reproductive outcomes.