Changes in temperature in the environment significantly influence the behaviour of the animal. The temperature range (thermoneutral zone) for a dairy cow is -5°C to +21°C, and at lower or higher temperatures, this causes changes in normal behavior - the body's energy balance is disturbed. Thus, it is common that summer air temperatures can cause heat stress to the dairy cow, which also results in reduced production. Heat stress occurs when the outside air temperature is higher (and at the same time the humidity is high) out of the animal's thermal comfort zone, i.e. the outside temperature "load" is greater than the animal's ability to get rid of excess body heat. High-yielding and multiparous dairy cows are thought to be particularly sensitive to heat stress. Heat stress in an animal occurs when the air temperature is between 24°C and 27°C.
With one degree (°C) rise in air temperature (at sub-optimal air temperature) the cow's water consumption increases by about 1.5 liters.
Source: Loomade heaolu. Õpik kõrgkoolidele
Watch a short video ‘Managing Heat Stress in Dairy Cows’: