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United States Department of Agriculture

Agricultural Research Service


item Mader, Terry
item Davis, Shane
item Gaughan, John
item Brown Brandl, Tami

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 8/20/2004
Publication Date: 8/26/2004
Citation: Mader, T., Davis, S., Gaughan, J., Brown Brandl, T.M. 2004. Wind speed and solar radiation adjustments for the temperature-humidity index. Meeting Abstract. 16th Conference on Biometeorology and Aerobiology,Vancouver, British Columbia, Canada. B.3. CDROM.

Interpretive Summary: Environmental conditions including temperature, humidity, wind speed, and solar radiation all affect the sensation of heat and the discomfort level of animals. An equation developed in 1959 has been used by the cattle industry to determine the level of discomfort due to the heat. However, this equation does not include the factors of wind speed or solar radiation. Data from several studies provided a basis for including adjustments for wind speed and solar radiation.

Technical Abstract: Wind speed (WSPD, m/s) and solar radiation (RAD, kcal/meter squared) are known to influence the magnitude of heat stress experienced by livestock. Data from three summer feedlot studies were utilized to determine WSPD and RAD adjustments to improve the temperature-humidity index (THI). Visual assessments of heat stress based on panting scores (0 = no panting, 4 = severe panting) were collected from 1400 to 1700 hr during the three summer studies. Based on these data, the adjustments to the THI for WSPD and RAD are 1.992 and 0.0079, respectively. Three separate cattle studies were utilized to evaluate the relationship between the adjusted THI and panting score. The mean R-square between THI and mean panting score was 0.39, while the mean R-square between the adjusted THI and mean panting score was 0.50. Although knowledge of THI alone is beneficial in determining the potential for heat stress, adjustments for WSPD and RAD are essential to more accurately assess animal discomfort.

Last Modified: 10/16/2017
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