Description of a growth simulation model for predicting the effect of diet on broiler composition and growth

The growth simulation program, BPHL (Bromley Park Hatcheries Limited), is a computerized, mechanistic, deterministic and dynamic approach to the evaluation of the effects of diet on broiler carcass composition and growth. Daily growth is simulated with information on the initial age and live weight of the bird, number of days over which the diet is to be fed, protein and amino acid densities of the diet, dietary metabolizable energy, and whether feed intake is to be simulated or data provided. Output provides information on a daily basis with respect to daily and accumulated deposition and current bird status for protein, fat, water, and ash body content. Carcass weight, feather weight, live weight, feed eaten, feed deprivation heat loss, limiting amino acids, food conversion ratio, and percentage carcass fat are also provided. The approach employs empirically derived first-limiting amino acid coefficients relating to accretion efficiency and dietary concentration to define limits of protein retention, uses mathematical expressions describing feed intake and heat loss trajectories as datum patterns prescriptive of the strain, introduces calibration as a device for improving correspondence between simulated and field performance, and relies on an assumption that deviations to the datum patterns of food intake and heat output caused by strain and environmental factors can be duplicated by simple multiplers acting on the expressions. The program may be used as a tool for exploring the predicted effect of specific dietary characteristics and strain parameters on growth, body composition, and performance.