Respiration chambers were used to measure, over 24 h, the heat production of groups of starved ducklings from two batches and of starved broiler chickens from one batch up to 28 and 39 d of age, respectively. Duration of starvation prior to measurements and ambient temperature were adjusted according to the age of the birds. 2. Respiratory quotient of 0.705 for chickens was significantly lower than that of 0.713 for ducklings. 3. Starvation heat production (kJ/d) of ducklings was 804 kgW0-70 compared with 675 kgW0-74 for chickens. There were differences in heat production between the two batches of ducklings used when expressed per kg body weight (W). 4. Ducklings lost more body weight, body fat and protein than chickens during starvation. Gaseous ammonia-N was on average 9% of N excreted by ducklings and 4% of N excreted by chickens.
