Reductions in milk production and reproductive performance are an economic loss to dairy producers. This publication discusses strategies that can be used on commercial dairies to reduce the effects of heat stress on dairy cattle. Signs of heat stress become evident in dairy cows when the THI exceeds 72. Measurements should be taken at the level of the cows' back, along the feeding area, in the freestalls and in the holding pen. Heat Loss in Dairy Cows Dairy cows dissipate heat through conduction, convection, radiation and evaporative cooling.
Conduction is based upon the principal that heat flows from warm to cold.
This method of heat loss requires that a cow have physical contact with surrounding objects. When a cow wades into a pool, she is cooled by conduction. Cooling by convection occurs when the layer of air next to the skin is replaced with cooler air. Radiation of body heat can occur This text was extracted from the publication, MF-2319.