A comprehensive index for assessing environmental stress in animals

Area of Science:

• Environmental Science
• Biometeorology
• Animal Science

Background:

• Existing heat and cold indices adjust ambient temperature (Ta) for relative humidity (RH) or wind speed (WS), but not comprehensively.
• No single model effectively integrates RH, WS, and radiation (RAD) adjustments across diverse hot and cold environmental conditions.

Purpose of the Study:

• To develop a comprehensive climate index (CCI) applicable across a wide range of environmental conditions.
• To provide adjustments to ambient temperature (Ta) for RH, WS, and RAD to determine apparent temperature.

Main Methods:

• Compiled environmental data from 9 summer and 6 winter periods with heat stress and cold conditions.
• Developed exponential relationships for RH and WS adjustments to Ta.
• Incorporated linear relationships for RAD (direct solar and ground surface) adjustments to Ta.

Main Results:

• The CCI provides adjusted apparent temperature incorporating RH, WS, and RAD.
• RH adjustments show exponential relationships, significantly impacting apparent temperature differently in hot versus cold conditions.
• WS adjustments are exponential with logarithmic components, showing greatest change per unit WS at slower speeds.

Conclusions:

• The developed CCI offers a unified approach to apparent temperature across varied climates.
• This index can enhance biological response function development and weather-dependent decision-making.
• Defined thresholds can guide management and mitigation strategies for animal comfort and protection.