A comparison of the energy metabolism of two breeds of hens and their cross using respiration calorimetry.

1. The maintenance energy requirement of the Black Australorp, White Leghorn and Black Australorp times White Leghorn hen was 911, 765 and 885 kJ/d respectively and availability of metabolisable energy of the diet was 79, 84 and 92%. 2. Heat production, after 30 h of starvation, was 311, 395 and 387 kJ/kg W0-75/d for the Australorp, Leghorn and crossbred, respectively. 3. It was calculated that availability of metabolisable energy was 51% for protein and 96% for fat retention. 4. Water consumption was significantly higher for the Black Australorp at the mean level of food intake for all hens, and increased more rapidly per unit intake than was observed for the other two breeds.