Application of the law of diminishing returns to partitioning metabolizable energy and crude protein intake between maintenance and growth in egg-type pullets

SUMMARY Experiments designed to investigate the effect of dietary nutrient concentrations on the growth and development of pullets are relatively long term and expensive to conduct. As the cost of research increases, mathematical models become valuable tools to answer research and development questions. Modeling growth curves allows nutritionists and poultry researchers to predict dynamic or daily nutrient needs more adequately than using fixed requirements. The potential and validity of a specially reparameterized monomolecular model to partition nutrient intakes between requirements for maintenance and growth was previously demonstrated in relation to ruminants, pigs, chickens, turkeys, and broiler breeder pullets. In the current study, the model was evaluated for its ability to estimate ME and CP requirements for maintenance and growth in egg-type pullets. On the basis of the results of this study, along with those previously reported for chickens, turkeys, and broiler breeder pullets, this model is advantageous because it can predict the magnitude and direction of responses of growing poultry to dietary ME and CP intakes without requiring initial assumptions. The model also has the advantage of biological interpretability of the parameter estimates. One of the main consequences of this interpretability is that the results from several experiments can be pooled to obtain the best estimates of the response coefficients.