The Effects of Evaporative Cooling on Folliculogenesis and Ovarian Hormones during the Estrous Cycle of Dairy Holstein Cows during the Summer Months in Saudi Arabia

Heat stress is identified as a major cause of lower productive and reproductive performance in animal farming. This situation is more common in Saudi Arabia than in other countries because of extremely high ambient temperatures experienced during the summers. The evaporative cooling cow group had significantly increased serum E2 concentrations on days 7 and 14 - 19 of their estrous cycles, and significantly decreased serum P4 concentrations on days 7 - 18 of their estrous cycles. Evaporative cooling plus shade lowered ambient temperatures (41.80 ± 0.74 versus 47.40˚C ± 0.84˚C) have increased the relative humidity (0.33 ± 0.01 versus 0.24 ± 0.01) and decreased the temperature humidity index (80.24 ± 0.60 versus 84.77 ± 0.68) when compared with shade alone. However, cows under shade alone, compared to cows under evaporative cooling with shade, had a larger number of small (10.04 ± 0.54 versus 4.72 ± 0.58), medium (2.80 ± 0.21 versus 1.79 ± 0.17), and large follicles (6.82 ± 0.28 versus 5.66 ± 0.22). These results demonstrated that while evaporative cooling had positive effects on dairy cows in this experiment, changes could have been more profound, if installations of curtains and fans were implemented, which might need further investigation.