The aim of this study was to evaluate the effects of differents sperm concentration and incubation time during in vitro fecundation on sperm penetration, monospermic fecundation and cleavage rates, using sperm of Gyr bulls. In vitro matured oocytes (n=817) were distributed into treatments to in vitro fertilization (IVF) in a factorial design, with two sperm concentration (2 and 4×10(6) spermatozoa/ml), two incubation time (12 and 18h) and two bulls (A and B). Viable spermatozoa were obtained by swin-up. The IVF was realized in Fert-Talp medium with heparin, on incubator with 5% CO2 and 95% humidity in air, at 39ºC. After insemination, 359 oocytes were fixed and stained to determine penetration and polyspermy rates. The remainder were co-cultivated in bovine oviduct epithelial cells and TCM-199, for 72h, to evaluate cleavage rate. The penetration, monospermic fecundation, and cleavage rates were not affected (P>0.05) by sperm concentration and incubation time. Higher (P<0.05) penetration and cleavage rates were observed for bull B (83.3 and 81.8%, respectively) than for bull A (66.3 and 64%, respectively). Bull B showed a tendency to present higher (P<0.07) polyspermy than bull A (16.4 and 6.25, respectively). No interactions among treatments were observed.
Bovine; Gyr; in vitro fertilization