The study sought to evaluate whether environment temperature (T) and relative humidity (UR) had an impact on the leucogram and cytology of the respiratory tract of healthy cattle. Blood and tracheobronchial lavage were collected from 5 female healthy 4 to 7-month-old Jersey calves in three moments: T1 (T=5ºC, UR=93%) T2 (control environment temperature, T 22ºC, UR 80%), and T3 (T=30ºC, UR=41%). Monocytosis in the leucogram and a decrease in alveolar giant macrophages were observed in T3. It appears that the weather condition had an influence on the respiratory immune system of the calves due to a stress situation. We conclude that elevated temperature associated with low relative humidity appears to favor respiratory disease in 4 to 7-month-old calves.
Respiratory tract; environment temperature; cattle
