Performance of roof-mounted misting fans to regulate heat stress in dairy cows

Abstract

Heat stress can negatively affect cow's physiology, behavior, and milk production. This study evaluates the effectiveness of roof mounting misting fans to improve heat and humidity index which reduces heat stress in a cowshed. Local climatic conditions were monitored and cooling system ability to control heat stress were assessed. Measurements were conducted at different cooling zones and levels comparing with shaded and open zones. The temperature and humidity index measurements outside the cowshed THI_out showed that animals exposed to high degrees of heat stress during most of the day. The average value of THI_out was 87.49, whereas the average value of adjusted outside temperature and humidity index THI_adj was greater than THI_out by 10% when solar radiation was considered. The maximum difference of hourly averages for temperature and humidity indices THI_adj and THI occurred at noon when the intensity of solar radiation was highest. The average value for temperature and humidity index under misting fans THI_fan was 82.27 whereas inside the cowshed under shade THI_shade was 85.20. This conclude that the misting fans was able to reduce heat stress in a limited degree. Further improvement in terms of the cowshed design aspects and an increase of cooling efficiency is needed.

Keywords: Heat stress; Misting cooling fans.; Temperature and humidity index.