The aim of this study was to evaluate ovarian pre-stimulation using recombinant bovine somatotropin (rbST) or rbST associated to FSH on follicular population, oocyte retrieval and in vitro embryo production in Gir cows (Bos indicus). Estrous cycle of non-lactating cycling cows with similar body and reproductive conditions were synchronized with cloprostenol followed by norgestomet ear implants, replaced every fourteen days. The animals were randomly distributed in three treatments: TI or control (punctured without pre-stimulation), TII (injection of 160 mg of rbST, before each aspiration) and TIII (injection of 160 mg of rbST followed by administration of 250 U.I. of FSH, before each aspiration). Oocytes were maturated and fertilized in vitro and presumptive zygotes were cultured in vitro for 192 hours post-fertilization. Treatments did not differ for ovarian follicular population. However, an increase in the diameter of the largest follicle and in the number of large and medium follicles with reduction in the number of small follicles was observed for TIII. Oocyte recovery did not differ between TI and TIII, but recovery rate was lower for TII. The number of grade I oocytes was higher and the number of degenerated oocytes was lower for TIII than for TI or TII. The rbST increased cleavage rate and blastocyst production, and when associated to FSH the quality of oocyte in Gir animals was improved.
bovine; Gir; ovum pick-up; rbST
