Estimation of the heat stress probability in cows in an uninsulated cowshed during summer heat

The air temperature and relative humidity in the cowshed were examined during summer heat period to determine the comfort of dairy cows by calculating the temperature-humidity index (THI). These values were depended on the time of day. The difference in average temperatures inside and outside the cowshed didn't exceed 23° C. During the summer heat period (+36.9 °C), the uninsulated cowshed was cooler because of the tent (which had provided shadow against the sunlight) and the continuous work of large diameter fans. The relative air humidity in the room was on average 1-14% higher than outside, due to the release of moisture by animals and evaporation from the surrounding equipment. Therefore, THI outside and inside the cowshed differed by 2-3 units (P<0.05). It exceeded the comfortable value (68) for cows during 18 hours per day, with a maximum increase to 81. The THI in the room itself was also different. The difference between the central and side parts of an uninsulated cowshed reached 3-4 units (P<0.05). This was depended on its location relatively to the four points of compass (from north to south) and the time of day, which means, on the degree of warming up the room by the rays of sunlight.