Efecto de la aplicación de la hormona de crecimiento recombinante (rbST) sobre la respuesta superovulatoria y la viabilidad embrionaria en ovejas de pelo

The objective of this study was measure the effect of using nutritional high quality protein and its interaction with recombinant growth hormone over the ovulatory response and embryo viability in hair ewes. Twelve adult multiparous Pelibuey ewes were used and randomly submitted to two different treatments. In treatment A (TA, Control group), the ewes received a superovulation treatment without the application of recombinant growth hormone (rbST) in treatment B (T₈), the ewes received the same superovulation treatment with the addition of 100 mg of recombinant bovine somatotropin (rbST). The induction and synchronization of the estrous cycle was realized by the insertion of vaginal sponges impregnated with 40 mg of FGA during 14 days, with sponge change at the seventh day. To induce the superovulation follicle stimulating ovine hormone (oFSH) was used in decreasing doses levels (every 12 h) starting 72 h before the sponges withdrawal. In the first application 2 mL of prostaglandin PGF_2α were additionally applied. The application of 100 mg of rbST was done during the eighth administration of oFSH. The ewes were inseminated 56 ± 1 h after the sponge withdrawal with refrigerated semen (10⁸ sperm/ straw). The embryos were collected 5 days after the insemination and the embryo viability was measured by morphological evaluation. An increase was observed in all the variables evaluated in the rbST group: corporea lutea (89 vs 119), corporea lutea considered (77 vs 117), embryos recovered (64 vs 78), viable embryos (35 vs 64), and viable embryos by ewe (5.8 vs 10.6), with statistical significance, considered ovulation rate (86.52% vs 96.64%) and embryo viability rate (54.69% vs 82.05%) (P<0.01), this is probably due to the effect of rbST over the growing insuline factors that control the follicular esteroidogenesis. The rbST application before the ovulation influence the maturation of higher amount of follicles and increase the quantity and viability of the embryos obtained.