An Indirect Closed Circuit Respiration Chamber Suitable for Fowl

The indirect closed circuit calorimeter, constructed of Perspex, can hold a single fowl of up to 3 kg. or six chickens from 10 to 24 days of age. Heat production is measured over a period of 24 hr. A decrease in pressure within the chamber occurs through absorption of expired CO2 in a KOH solution. A solenoid valve is activated and O2 flows into the chamber from a cylinder holding 200 1. of O2 which is weighed at the start and finish of a 24 hr. determination of heat production. Samples of chamber air are withdrawn at the start and finish of each determination and heat production is calculated from the quantitative recovery of carbonate and from the loss of weight of the O2 cylinder, after first correcting for any changes in the composition of the chamber air that occur during the 24 hr. period of measurement. Three chickens (each weighing about 1 kg.) taken from a group of 10 cross-bred cockerels, were placed one in each of three calorimeters and given a commercial cereal-based diet. The remaining 7 cockerels were killed to give initial values of body composition of the 3 experimental fowl. Heat productions were measured over a period of 12–18 days; the 3 fowl were then killed and body composition determined. Heat production of the cockerels, estimated from gaseous exchange was, on average, within 1% of values derived from the carbon and nitrogen balances. Fasting heat productions of the 3 fowl were 71, 72 and 71 kcal./kg.3/4/day and net availability (%) of metabolizable energy of the diet was 70, 70 and 61 respectively. Composition of weight gain of two of the cockerels agreed with values estimated from carbon and nitrogen balance, but for the third cockerel nitrogen retention was much higher when estimated from nitrogen balance than from carcass analysis.