In a recent study (Pegorer, 2005) the effect of sire and sired breed on conception rates of Holstein
cows were evaluated during the summer in Brazil. A total of 1113 Holstein cows were AI with semen
from four Gyr sires (B. t. indicus) or three Holstein sire. The use of Gyr bulls increased pregnancy rate
when compared to Holstein bulls (P = 0.008). This result is in accordance to the present work obtained
in vitro in Nelore cattle and indicate that use of indicus sires may result in greater pregnancy rates in
lactating Holstein cows during heat shock.