Oocytes from Nelore and crossbred (B. t. indicus×B. t. taurus) cows were randomly allocated into
eight groups, four control groups, in which oocytes from Nelore or crossbred cows were matured,
fertilized with Nelore or Angus semen and cultured at 39 ◦C (Groups N×N, A×N, N×CB and A×CB;
N=Nelore, CB = crossbred and A = Angus, where the first letter is the breed of the bull and the second
is the breed of the cow). For each of the control groups above therewere respective heat shock groups.
Embryos assigned to the heat shock groups were placed in an incubator at 41 ◦C for 12h (at 12, 48 or
96 hpi) and at 39 ◦C thereafter.