Comparison of heat production of chickens measured by energy balance and by gaseous exchange.

An open-circuit respiration calorimeter suitable for chickens or other small animals has been constructed. The system contains two animal chambers and is capable of determining heat production of two animals or groups of animals independently and simultaneously with gas collection apparatus for continuous sampling of chamber gases. The operation of the system was tested in two experiments by determining heat production of two groups of 10-week-old, full-fed cockerels over a 4-day period both by energy retention (body balance) and gaseous exchange. Heat production (kilocalories per bird per 24 hours) as determined by energy balance versus gaseous exchange was 359 versus 348 in one experiment and 395 versus 393 in the other. The agreement was sufficiently close to support the use of respiration calorimetry to measure heat production of chickens under experimental conditions in this laboratory without killing the experimental subjects. On the basis of metabolic body weight (in kilograms, W0.75) heat production measured in this manner was 161 and 173 kcal (day . W0.75) in experiments 1 and 2, respectively.