Evaluation of the THI

The THI is an index that allows the evaluation of thermal stress. It takes into account temperature and humidity.

The drier and colder the air is, the easier it is to evacuate heat, and vice versa. A moderate temperature (24°C for example) but associated with a high humidity (80%) leads to a THI of 73, which is considered dangerous.

This index can be specified taking into account the air speed. Indeed the air facilitates the evaporation of sweat and the evacuation of heat through the skin.

For example, an air speed of 2.5m/s lowers the THI by 5 points.

Measurements should be taken as close as possible to the animals: if possible in the sleeping area at animal level. In the case of permanent sensors, make sure they are protected from the animals.

Be careful, after a hot period, the animals take time to recover. Even if the THI drops below acceptable thresholds, it is considered that it takes as much time to recover as the hot period itself.