Insemination and embryo transfer programs: Effect of estrous on pregnancy and embryonic and fetal losses in bovine

The primary objective of implementing embryo transfer in meat operations is to accelerate the rate of genetic progress in the herd. Among the main factors that affect the use of these technologies are related to the nutrition, the management and the synchronization of the estrus. As a result of research conducted in the last 20 years, the use of the receptor has increased through the application of protocols that synchronize ovulation and allow the transfer of embryos without the need for oestrus detection, generally known as fixed-time embryo transfer. (FTET). Although these protocols have functioned well for several years, attention has recently been directed to the effect of estrus expression and estradiol concentrations during pre-ovulatory follicle growth on embryonic growth and pregnancy. The experiments reviewed in this document demonstrate that oestrus expression is positively associated with high pregnancy rates and reduced pregnancy losses in recipients receiving frozen / thawed bovine embryos produced in vitro and in vivo.