Effects of diet supplementation and body cooling on Friesian calves reared in high ambient temperatures in the eastern desert of Egypt.

Four groups of 10 Friesian male calves were fed on rice straw ad libitum and concentrate for 2 months. The first group was fed in winter. The other 3 groups (1, 2 and 3) were fed in summer. Group 1 was fed the same diet as the winter group, Group 2 was fed on the same diet as Group 1 but it was supplemented with urea and a minerals and vitamins mixture and Group 3 animals were fed on the same diet as Group 1 and cooled by sprinkling and drinking cool water. The results showed that high ambient summer temperatures induced highly significant decreases in weight gain and feed efficiency and deleterious effects on thyroid, liver and kidney functions. The diet supplemented with urea, minerals and vitamins improved liveweight gain and restored some blood components, but the effects of high ambient temperature were not completely alleviated since the calves still had increases in transaminase enzyme activities, rectal temperature and respiration rate. Cooling the animals during summer led to improved body liveweight gain, feed efficiency and certain body functions. In addition, the cooling treatment reduced the heat load and aided the animals to reach a steady physiological state, confirming that the cooling treatment was more effective than diet supplementation in removing heat load during the summer.