Energy metabolism of growing broiler chickens kept in groups in relation to the environmental temperature. 2. Heat production, thermoregulatory heat production and thermoneutral temperature (short term measurement)]

In 5 experiments the weekly rhythm of the heat production of growing young broiler chickens kept in groups between their 5th and 57th days of life was measured according to the method of short-time measuring (30-minute measuring periods) in dependence on environmental temperature (ET) between 40 and 5 degrees C in stages of 5 K by means of gas exchange and indirect calorimetry. The keeping temperature ranged from one experiment to the other from 35, 30, 25, 20 to 15 degrees C. The dependence of heat production on ET is parabolic in the medium and high ranges of temperature. As a rule, heat production increases progressively with very low ET. Thermoneutral temperature depends on both, the age (live weight) of the chickens and environmental temperature. Thermoregulatory heat production decreases with growing age. It changed from 24 kJ/kg LW0.75.d.K at the beginning to 8 kJ/kg LW0.75.d.K at the end of the experiments.