Experiments were conducted at a dairy farm located in Inhauma, Minas Gerais, Brazil (latitude 1982902800S,
longitude 4482302300W) during the summer of 2003 and 2004. Lactating Holstein cows (B. t. taurus) were
maintained in a free-stall barn containing sprinklers and fans thatwere turned on during the hottest hours of the
day (10:00–15:00 h). Cows were inseminated with frozen-thawed semen from a total of seven sires (four
Gyr and three Holstein). Semen was processed at Central Bela Vista (Pardinho, Sa˜o Paulo, Brazil), and each straw
of semen had at least 15 million sperm at the time of freezing.