Efeito do momento da inseminação artificial com sêmen sexado na produção de embriões de doadoras da raça nelore (Bos indicus) superovuladas

Abstract

The effect of the moment of TAI with sex-sorted sperm in embryo production of Nellore (Bos indicus) superovulated donors was evaluated. To this end, 16 cycling donors were used, aged between 4 and 10 years, and postpartum than 40 days. The animals were divided evenly into four groups, according to the moment of TAI (12 and 24 vs. 18 and 30h after administration of pLH) and type of sperm used (conventional vs. sex-sorted). The groups were divided as follows: TAI with conventional sperm 12 and 24h (CSG12/24) and, 18 and 30h (CSG18/30); TAI with sex-sorted sperm 12 and 24h (SSG12/24) and, 18 and 30h (SSG18/30). The design was completely randomized, in a 2x2 factorial scheme, with all the animals in their respective categories, submitted to all treatments (randomized cross-over) in a total of four replicates, with an interval of 42 days between replicates and 16 repetitions per treatment. Donors were synchronized with intravaginal progesterone device (P4) for 7 days. On the day of device insertion (D0) was administered 2.0mg i.m. of Estradiol Benzoate. From D4 to D7, all donors were treated with 8 decreasing doses of FSH (133mg i.m.; 12/12h). On D6, all animals received two applications of PGF2α (0.53mg i.m.) after each application of FSH. At the last dose of FSH (D7) the P4 device was removed and, donors received the administration of pLH 12h later (25mg i.m.; D8). The embryonic structures were collected seven days after application of LHp (D15) and, were quantified and classified according to morphology and quality (IETS, 1998). The variables were analyzed by Proc GLM procedure of SAS®. In groups GSC12/24, GSC18/30, GSS12/24 and GSS18/30 were recovered, respectively: total of embryonic structures (2.9 ± 1.1, 3.4 ± 0.8, 2.6 ± 1.2, 4.1 ± 1.3); unfertilized oocytes (0.0 ± 0.0, 0.1 ± 0.1, 1.7 ± 1.2, 0.4 ± 0.2); transferable embryos (2.6 ± 1.0, 2.7 ± 0.7, 0.5 ± 0.3, 2.2 ± 1.0); freezable (2.4 ± 1.0, 2.7 ± 0.7, 0.5 ± 0.3, 2.0 ± 1.0) and degenerate (0.3 ± 0.1, 0.7 ± 0.4, 0.4 ± 0.3, 1.5 ± 0.8). There were no differences between groups (P > 0.05). As there was no interaction between treatments, it was possible to evaluate the main effects (type of sperm type and moment of insemination). As verified between groups, no difference was found for any of the variables analyzed between the main effects (P > 0.05). The results did not confirm the hypothesis that the delay in six hours in the FTAI with sex-sorted sperm in superovulation protocols results in increased production of viable embryos obtained from Nelore donors.