The amino acid requirements of chicks: experimental validation of model-calculated requirements

The amino acid requirements of broiler chicks, on a weekly or biweekly basis, were calculated according to a model presented previously (Hurwitz et al., 1978). Based on the present results, the model has been somewhat modified. The model requirements provided the basis for computer-designed diets which were fed to chicks of different ages and were composed to others computed on the basis of NRC (1971, 1977) requirements. In all cases the model-based diets, which were considerably lower in protein, supported weight gains equivalent to those obtained on NRC-based diets. The relatively poorer feed efficiency observed in the first trial with chicks fed the model-based diets, could be alleviated by equalizing both energy and lipid concentrations in the experimental diets. Thus, equal growth and feed efficiency were obtained with the model and NRC (1971)-based diets, for 2- to 10-week-old chicks. The possible reasons for the slightly higher abdominal fat content of the chicks fed the model-based diets are discussed.