Efficiency increase in the embryo recipients results with resynchronization protocols

The aim of this study was to evaluate the effectiveness of a resynchronization protocol on pregnancy rate in crossbred heifers used as embryo recipients. This experiment was conducted on a farm located in southwest Minas Gerais. Experiment 1: Aimed to evaluate the efficiency of 1 mg of estradiol benzoate (EB) in the synchronization of follicular development wave. 40 crossbred females divided into two groups were used. G1 - 1mg of BE; and G2 - 1 ml saline. Changes in follicular dynamics were accompanied by ultrasound. The 1mg BE Application proved effective (95%) in synchronization of follicular development. Experiment 2, it was produced 368 embryos in vitro (PIV) using donor Gir (Bos taurus indicus) and sexed semen of the Dutch race. The transfer of embryos was synchronized through an embryo transfer protocol at fixed time (FTET). D0: it was implanted an intravaginal progesterone device – PID plus 0.5 mg of estradiol benzoate - BE intramuscular (IM); D8: Remove PID plus 0.5 mg of estradiol cypionate - EC MI and 0.125 mg of D-cloprostenol. On the day of embryo transfer (D17) recipients were evaluated by ultrasound (Mindray® - M5). Fourteen days after embryo transfer (ET) recipients were randomly divided into two groups: G1 (n = 184) initiation of resynchronization protocol by inserting a PID application of 1 mg of EB and G2 (n = 184) it was not treated. This procedure was developed to evaluate the effect of estradiol application in early pregnancy. In D39 all recipients passed via pregnancy diagnostic ultrasound (US). In G1 pregnant only removed the PID. Eight days later, all recipients were reassessed by ultrasound for the diagnosis of pregnancy. In females pregnant of the G1 was only removed the DIP (D39) and females do not pregnant in this group received 0.5 mg of EC and 0.15 mg of D-Chloprostenol intramuscular and PID was removed. Ten days later females were again evaluated and those capable were inovulated. Already in G2 the beginning of the second FTET protocol only begins after the diagnosis of non-pregnancy (D39), repeating the same procedure D8. It was compared by X2 pregnancy rate after the first and second transfer embryos and the number of pregnant recipients at 30 and 45 days. The pregnancy rate after the first TE had no difference between the groups (P> 0.05 to 52.2 vs. 48.9% for G1 and G2, respectively). This result confirms that the insertion of a DIP application of 1 mg estradiol benzoate cows in early pregnancy does not interfere with the maintenance of pregnancy. There was no difference in pregnancy rates after the second TE (P > 0.05 to 47.9 vs. 48.8% for G1 and G2, respectively). This result shows that the resynchronization does not interfere with the fertility of the recipient. It follows that the resynchronization protocol used does not affect the maintenance of early pregnancy in recipient and may provide a pregnancy advance and allow pregnancy receiving a short period of time.