Lactating dairy cows are susceptible to heat stress
( HS) during summer because of elevated internal
heat production associated with lactation. During
periods of HS, milk production, feed intake, and physical
activity are decreased (6). At the same time,
reproductive ability is compromised (5, 8, 20).
Productive and reproductive losses associated with
HS are economically significant (13). Nevertheless,
the physiological mechanisms that lead to summer
infertility are only partially understood.