Factors influencing heat stress in cattle

Recognize stress for the animals in the barn

In order to correctly recognize and assess the current heat load in cows, various climate parameters must be taken into account. Here is an overview of how the situation in the barn can be optimally assessed:

• Air temperature: The higher the temperature, the greater the stress for the animals.
• Relative humidity: High humidity makes it more difficult to release heat through respiration.
• Wind speed: A higher wind speed can support cooling.
• Heat or solar radiation: Direct sunlight increases the body temperature of the cows.

The TH Index (Temperature-Humidity Index) is used to assess the current risk to the cows. The THI provides a reliable way of assessing the stress level for the animals. It is calculated as follows:
THI = 0.8 x ambient temperature + ( relative humidity/100 x (ambient temperature – 14.4) ) +46.4

This index allows farmers to quickly recognize when additional measures to cool the animals are necessary. The THI value provides a guide to specifically prevent heat stress and ensure the well-being of the cows. For example, a THI of 68 is already mild heat stress.