Effect of time of day and type of shading on the physiological responses of crossbred calves in tropical environment

Many studies report adverse environmental conditions, damage yield, especially in dairy cows. However, studies on the effects of environment on young animals, especially calves of mixed race, are rare. Study effects of time, day and type of shading on the physiological responses of crossbred calves in tropical environment. Twenty-four Holstein and SPRD (without defined breed) calves were identified in two nursery facilities, one provided with natural shading and the other provided with artificial shading by means of cement tile. In both facilities, environmental data including air temperature, wind speed, and black globe temperature were recorded between7 a.m. to 4 p.m. to calculate the radiant thermal load. Physiological responses, rectal temperature and respiratory rates were measured in the morning and in the afternoon. The natural shading provided less thermal comfort because of higher radiant thermal load, especially in the afternoon. The crossbred calves showed higher rectal temperature and respiratory frequency as compared with SPRD calves in both periods and in both nursery facilities, with the highest values reported under natural shading. Calves of different genotypes respond differently in hot environments, should be to test in future research another types of trees to verify their thermal quality.