Effects of Climatic Conditions on Energy Metabolism and Performance of Calves

Abstract

The effects of cold are especially critical in newborn calves due to their high energy losses through the wet hair coat and the great variability in summit metabolism. Nevertheless, high-vitality calves can withstand low ambient temperatures, whereas premature or dystocial calves are unable to increase their heat production to compensate for their high heat loss and they become hypothermic.

During the rearing period, the energy expenditures and the lower critical temperature of calves depend on breed, physiological stage, feeding level and climatic factors (temperature, wind and rain). The performance of healthy calves kept outdoors in winter in moderate climatic conditions is not significantly different from that of calves reared in a heated barn or under shelter, except at low temperatures associated with very high humidity. The weight gain of suckler calves is reduced only at very low temperatures. Shelters with walls alone have a greater protective effect than a roof alone. Shelters with both walls and roof almost eliminate the depressive effect of climate.

Calves are more sensitive to heat than to cold, especially when their production level is high. The effect depends on ambient temperature, air humidity and velocity, and solar radiation. Adaptation to heat is long and incomplete. However, calves are able to withstand high temperature and humidity for several hours, without any significant reduction in performance, if they can recover at a lower temperature during the night.

The physiological responses of calves to cold and heat are briefly discussed in relation to energy metabolism, thermoregulation and performance, especially in the case of dystocial calves born in winter and rapidly growing calves in Mediteranean regions during the summer period.