Figure 5. Effect of increasing temperature humidity index on milk yield in lactating Holstein
cows.
Evaluation of data on minimum THI indicates that milk yield losses become significant when
minimum THI on any given day is 65 or greater. Average losses in milk yield per day were 2.2
kg per day between a minimum THI of 65 and 73. Thus suggests that cooling of dairy cows
should be initiated anytime minimum THI is 65 or above or when average THI is 68.