| dc.description.abstract | The present study was designed as 5 X 4 factorial to investigate the effects of using sperm from 5 bulls, and varied sperm-oocyte incubation times (5, 10, 15 and 20 h) on the fertilization, cleavage rates and blastocyst formation on an in vitro bovine embryo production system. The bulls included a tetraparental Chimera, its sires (Japanese Black and Limousin), its maternal grand-sires (Japanese Brown and Holstein). The proportion of polyspermy, 2-pronuclei formation, fertilization, cleavage and development to blastocyst were affected ( p < 0.01) by the duration of sperm-oocyte incubation, as well as by the interaction between bulls and their corresponding sperm-oocyte incubation time. Blastocyst rate observed after 5 h in oocytes inseminated with Chimera, Japanese Black and Limousin were higher ( p < 0.05) than those observed at 20 h incubation. The proportion of blastocysts from oocytes inseminated with Japanese Black observed at I 0 h of incubation did not differ from that of Chimera, but both were higher ( p < 0.05) than those observed for the Limousin, Japanese Brown and Holstein sires. The present study showed that there was an effect by the duration of sperm-oocyte incubation on in vitro embryo development. The optimal time of sperm-oocyte incubation for the Chimera was similar to that of its sires (Japanese Black and Limousin) but differed from its maternal grand-sires (Japanese Brown and Holstein). The fertilization rates for the sperm from the Holstein bull increased up to 15 h suggesting that this might be the only bull that would benefit from a long incubation period for insemination. © 1997 Elsevier Science B.V. | en |
