The aim of this study was to evaluate the effect of different sperm concentrations of Guzera bull semen during in vitro fertilization on the cleavage rate. Oocytes (n=356) obtained from a slaughterhouse ovaries, were in vitro matured and randomly divided into four treatments for in vitro fertilization, according to sperm concentrations: TI (0.5× 10(6) spermatozoa/ml); TII (1.0× 10(6) spermatozoa/ml); TIII (2.0× 10(6) spermatozoa/ml) e TIV (4.0× 10(6) spermatozoa/ml). Frozen semen from one Guzera bull was used for in vitro fertilization. The live sperms were separated by swim up, washed once by centrifugation, and then placed in in vitro fertilization media. The in vitro fertilization was performed in tubes in media with heparin and incubated in 5% CO2, at 39ºC for 20h. Thereafter, the oocytes were washed in Talp Hepes medium and cultured during three days in TCM 199 and bovine oviduct epithelial cells, at the same conditions of in vitro fertilization. From the spermatozoa used at the beginning of swim up, 10.21± 0.98% were recovered, and the motility increased from 67.5± 2.5% to 81.25± 2.4%. The cleavage rates were 31,0% (n=71), 44.7% (n=85), 55.9% (n=127), and 52.0% (n=73) for TI, TII, TIII, and TIV, respectively. The cleavage rate in TI was lower than in TIII and TIV (P<0.05). These results suggest that the best spermatic concentration during the in vitro fertilization, with Guzera bull semen, is above 1.0× 10(6) spermatozoa/ml. Sperm concentration of 0.5× 10(6) spermatozoa/ml was not efficient in this trial.
Bovine; Guzera; cleavage rate; in vitro fertilization; sperm concentration
