Energy, metabolism of young, unadapted calves

Calves reared for veal or other meat production are usually purchased before 2 weeks of age. The first weeks at the rearing unit represent a critical phase regarding their health. During this period calves are fed at a very low level. In this thesis, the energy metabolism of young, newly purchased calves, as affected by feeding level and ambient temperature, was studied. It was found that such calves are highly dependent upon body energy reserves due to restrictive feeding, their high maintenance requirements, and the low availability of nutrients from the diet. During this period, the response of these animals to temperature is not consistent with the current concept of thermoregulation. Thermal requirements are affected by the calf's posture (standing or lying). The influence of temperature on heat production of calves varies within a day. Part of this circadian fluctuation is related to the within day variation in time spent standing. The first 2 weeks after arrival the calves are not in a steady-state regarding their energy metabolism. Both the relationship between heat production and feeding level and heat production and temperature, change with time after arrival.