The heat production of hens and cockerels maintained for an extended period of time at a constant environmental temperature of 23 °C

Abstract

SUMMARY Hens and cockerels of a White Leghorn strain (‘H & N’) were kept at a constant temperature of 23 °C from 1 year until 2¼ years of age. The mean fasting heat production, which was measured 6 times during this period, varied between 404 and 464 kJ/kg 0·75 /day for the hens and between 223 and 349 kJ/kg 0·75 /day for the cockerels. The sex difference in heat production is discussed and an attempt is made to explain the variation in heat production for each sex.