Acclimation of young calves to high temperatures: physiologic responses.

Four 2- to 3-month-old male Bos taurus calves kept in an ambient environment of 18.3 C and 50% relative humidity for a week were then exposed to 40.5 C and 50% relative humidity atmosphere in a climatic chamber for short-term (2 weeks) acclimation. The exposure time was 12 hours each day. Their respiratory rate, skin temperature, and rectal temperature rose sharply on the 1st day of exposure and then gradually declined with continued exposure. The heart rate, on the ohter hand, declined with successive days of exposure. A gradual increase in sweating rates of calves was observed after the 2nd day of exposure. Most of the acclimation in these physiologic measurements was completed in the first 9 to 10 days of exposure and it was concluded that young calves have a well-developed power of acclimation to high temperature