In heat stressed cows the duration and intensity of estrus was reduced in some studies
[16,17] but was unchanged in others [18]. The balance of these and other studies suggest
that heat stress reduces the duration and intensity of estrus in dairy cattle. For example, in
summer, motor activity and other manifestations of estrus are reduced [13,19] and the
incidence of anestrus and silent ovulation are increased [17]. These effects lead to a
reduction in the number of mounts in hot weather compared to cold weather [20], leading to
poor detection of estrus. Therefore, in hot climates there is a reduction in the number of
inseminations and an increase in the proportion of inseminations that do not result in
pregnancy