The Influence of Receptor Cows Day of Estrus Manifestation on Pregnancy Rate at Legal Amazon

This study aimed at evaluating the pregnancy rate and determining the optimal moment for embryo transfer (ET) to bovine females, according to the moment of estrus. For such, 2.234 receptor cows from the herds raised within the Legal Amazon Region were submitted to ET. Among the receptors, 31 manifested estrus two days before (D-2) in vitro fertilization (IVF); 473 one day before (D-1); 1.247 presented estrus signs at the day (D-0) of IVF, 472 one day after (D+1) and 11 females presented estrus behavior two days (D+2) after IVF. Thus, all animals submitted to ET, 35.27% showed to be pregnant, out of which 57.90% received the embryos at D0, 0.37% at D-2, 22.34% at D-1, 19.02% at D+1 and 0.37% at D+2. It can be concluded that synchrony of up to ± 1 day is better to achieve pregnancy from in vitro produced embryos and that the season in the Legal Amazon Region is not a limiting factor to maintain the gestation of these embryos.