Effect of dietary protein, energy, and feed pelleting on the response of chicks to early feed restriction.

In three trials, male broiler chicks were subjected to a 6-day feed restriction regimen designed to retard growth severely. In one trial, the amino acid requirements during refeeding were evaluated by testing the adequacy of diets based on model calculations. In two additional trials, the response of feed-restricted birds to increased dietary energy density and to feed pelleting was compared with that of birds fed ad libitum. Results of the first trial showed that weight gain and feed efficiency during the first 2 wk of refeeding were reduced when the diet contained less than the model-calculated protein level for this period. No improvement in performance could be obtained when dietary protein was increased by 1% above model-calculated requirements. An increase in dietary nutrient density resulted in an enhanced growth rate. Feed efficiency was improved by an increase in nutrient density and by early feed restriction with no significant feed restriction x diet density interactions. Pellet-feeding resulted in improved growth without affecting feed efficiency, whereas feed restriction resulted in improved feed efficiency only. Interaction between pelleting and feed restriction was not significant for any of the variables. In all three trials, abdominal fat was reduced by feed restriction without any interaction with energy, protein, or dietary form. The results suggest that the requirements for some amino acid increase after feed restriction and that feed consumption does not limit the accelerated growth response at that time.