Artificial cooling of cows during the summer through use of shades and fans with or without a complementary sprinkling system will improve expression of oestrus. In a Mississippi study, fan cooling of shaded, lactating Holsteins that were synchronized with two injections of prostaglandin F2a resulted in 71% exhibiting oestrus as compared to 33% for shaded cows without fan cooling. In an Israeli study, short-term cooling of Holsteins using intermittent application of ‘sprinklers and fans resulted in more cows showing standing oestrus (70%) than was seen in noncooled cows (45%). Ovulation without manifestation of oestrus was more frequent in the noncooled cows.