[Energy metabolism of chicks at low environmental temperatures]

The daily energy metabolism of growing chickens for meat production (origin T 82) fed ad libitum was measured from the 5th up to the 65th day of life at environmental temperatures decreasing in the course of development (25, 20, 15, 15, 15, 10, 10, 5 and 5 degrees C, resp.). Further in each period the heat production was measured through a wide range of temperatures (Maximum 40 degrees C to 5 degrees C in steps of 5 K) by 30-minute short time measurements. The mean live weight of the chickens was 75 g at the beginning of the experiment and 3416 g (male) or 2952 g (female) at the end of the experiment. The digestibility of energy and nutrients was independent of the stage of development. On average the total efficiency of utilization of metabolizable energy was 39.2 +/- 4.8% and the partial efficiency of utilization was 69.7 +/- 2.1%. 15-38% of the produced heat, caused by thermoregulation. The thermoneutral temperature decreased in the course of development from 35 to 18 degrees C and in the same way the thermoregulatory heat production decreased from 23 to 12 kJ/kg LW0.75.d.K. In the 2nd period the thermoregulatory heat production was extraordinarily high at an amount of 28 kJ/kg LW0.75.d.K.