Tratamentos hormonais e seus efeitos sobre a produção de embriões bovinos in vivo e in vitro

Abstract

Embryo transfer (ET) allows the multiplication of genetically superior females, contributing to increased efficiency in food production. However, both in in vivo and in vitro embryo production systems there is still place for improvement. In the first study the objective was to identify if a single PGF administration at the time of artificial insemination (AI) improves fertilization and embryo production rates. Embryo donor cows (n=35) were submitted to superovulation (SOV) twice (n=70). In each round, half of the cows were not treated (control; n=35) or treated with PGF (482µg cloprostenol; n=35) at the time of the first AI. The number, stage of development and quality of embryos were recorded on the day of embryo recovery. The medians (CI 95%) for control and PGF groups were, respectively, 12 (10-18) and 15 (12-18) total structures; 9 (7-11) and 7 (6-10) viable embryos; 1 (0-1) and 1 (1-3) degenerated embryos; and 1 (0-3) and 2 (0-5) oocytes (P>0.05). In conclusion, a single PGF treatment at the time of the first AI does not affect the embryo production of superovulated cows. In the second study the objective was to evaluate the effect of an injectable hormonal treatment to synchronize the follicular wave of Bos taurus donors on progesterone (P4) concentration, number and quality of cumulus-oocyte complexes (COCs) recovered by ovum pick up (OPU) and in vitro embryo production (IVP) efficiency. Bos taurus cows (n=11) were submitted to four OPU sessions (n=44). On day zero (D0) the cows were allocated to control (not synchronized) or treated group (2 mg of estradiol benzoate; 150 µg of D-cloprostenol; and 300 mg of injectable progesterone). On day 6 (D6) the OPU procedures were performed. There was no difference (P>0.05) between control and treatment, in the medians (CI 95%) of total and viable structures, being, respectively, 12 (6-15) and 10 (9-19) total oocytes; 5.5 (5-8) and 6 (5-9) viable oocytes; the rate of embryo production was 28% (21-46%) for control and 33% (22-45%) for treatment. A significant difference (P<0.05) was observed in the concentration of progesterone on D6, being 2.8±0.8 and 1.1±0.2 ng/mL for control and treated groups, respectively. In conclusion, under the conditions of this study, the hormonal treatment for pre-aspiration synchronization did not improve the analyzed parameters, consequently, its application is not recommended. New studies are necessary to improve in vivo embryo production and to increase the number and quality of aspirated structures for bovine in vitro embryo production.