The Effects of Evaporative Cooling on Heat Stressed Dairy Holstein Cows Under a Semi-Arid Environment in Riyadh Area, Saudi Arabia

Heat stress has been identified as a major cause of lower productive and reproductive performance in animal farming. Methods for protecting livestock from heat stress were investigated during the summer months, where one six Holstein cows kept under shade only (group 1), and another six cows kept under shade with evaporative cooling (group 2). The results show that shade and water sprayers (evaporative cooling) significantly lowered ambient temperature and thus reduced the heat stress experienced by dairy cows in Saudi Arabia. Evaporative cooling plus shade, lowered ambient temperature (41.80 ± 0.74 vs. 47.40 ± 0.84°C), increased relative humidity (0.33 ± 0.01 vs. 0.24 ± 0.01) and decreased the temperature humidity index (80.24 ± 0.60 vs. 84.77 ± 0.68) when compared to shade alone. In addition, cows kept under evaporative cooling (38.4 ± 0.32°C) experienced lower rectal temperatures compared to cows under shade alone (39.53 ± 0.44°C). Cows under evaporative cooling had higher serum concentrations of triidothyronine (2.50 ± 0.90 vs. 0.75 ± 0.20 ng/ml) and thyroxine (11.94 ± 1.60 vs. 7.22 ± 1.88) than cows under shade alone. Thus, evaporative cooling can decrease the heat stress experienced by dairy cows in Saudi Arabia and limit its associated detrimental effects