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

Many studies report the relationship between adverse environmental conditions and damage yield, especially in dairy cows. However, studies about the effects of environment on young animals, especially calves of mixed breed are rare. Were studied the effects of day time and type of shading on physiological responses of crossbred calves in a tropical environment. Twenty-four ? Holstein and WDB (without defined breed) calves were identified in two nursery facilities; one provided with natural shading and the other provided with artificial shading by fiber cement tile. In both facilities, air temperature, wind speed, and black globe temperature were recorded between 7 am to 4 pm to calculate the radiant thermal load. Physiological responses (rectal temperature and respiratory rates) were measured in the morning and in the afternoon. The natural shade provided less thermal comfort because of higher radiant thermal load, especially in the afternoon. The crossbred calves showed higher rectal temperature and respiratory rate than WDB calves in both periods of day and in both nursery facilities, with the highest values recorded under natural shade. 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.