Effects of feeding by crop intubation on energy metabolism and physical activity in domestic cockerels.

1. Heat production and physical activity were measured in cockerels given the same amount of food either conventionally or by direct intubation into the crop. 2. The thermogenic effect of feeding (heat increment per unit weight of food) was about 30% less with tube-feeding. 3. The difference in heat increment of feeding, and therefore in efficiency of energy utilisation, was entirely attributable to the circumvention of feeding activity by intubation.