In an in vitro study embryos produced by insemination of Brahman oocytes with Angus spermatozoa
were more thermo-tolerant than embryos produced by insemination of Holstein oocytes with
Angus semen (Block et al., 2002). In contrast, there were no differences in thermo-tolerance between
Holstein×Brahman embryos and Holstein×Angus embryos. These results indicate that the contribution
of the oocyte plays a more crucial role in the ability of Brahman embryos to resist effects of heat
shock than the contribution of the spermatozoa