Changes in the body weights and the final carcass compositions of adult cockerels fed less than their maintenance requirements.

Seventy-two adult Single Comb White Leghorn (SCWL) cockerels of each of two strains were fasted for 48 hr. Twenty-four birds of each strain were killed and frozen. Eight birds of each strain were fasted for an additional 11 days and 4 birds of each strain received, by intubation, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 g of a high energy feed daily for 10 days, after which they were fasted for 48 hr. Birds were weighed and their excreta were collected at 24-hr intervals. At the conclusion of the experiment, all birds were killed and their carcasses, together with those of the initial slaughter group (IS), were assayed for water, protein, fat, and ash. All experimental birds lost weight. The change in body weight (delta BW) decreased linearly as feed input increased. Solution of the derived regression equation provided a mean estimate of .355 MJ/BW.75 kg/day (.0848 Mcal/BW.75 kg) for the energy requirement to maintain body weight. The estimate fails to take account of changes in body composition, but correction for this was impractical because of the large among bird variation. For the fasted birds, the delta BW displayed a logarithmic-decay pattern over time. Carcass protein and water increased with feed input but carcass fat was independent of feed input. However, the proportions of the carcass constituents did not vary with feed input. The proportion of carcass protein was greater and of carcass fat less at the end of the experiment than in the IS birds.