A COMPUTER-MODEL TO PREDICT COMPOSITION OF EMPTY BODY-WEIGHT CHANGES IN CATTLE AT ALL STAGES OF MATURITY

We developed methods to integrate two published models that partitione d gains in empty body weight (EBW) to fat and fat-free matter. These m odels were based on separate mathematical formulations for growing and mature cattle. We assumed that as cattle grow from birth to maturity a transition would occur at some point in the life cycle from the grow ing to the mature mathematical formulation. This transition point and the rate at which the transition occurs between the two mechanisms wer e estimated fi om published data. Evaluation results with data on stee rs that were full-fed to grow from birth to 815 kg EBW showed that the methods used to integrate the two models provided an accurate predict ion of empty body composition at final slaughter. Evaluation results w ith full-fed growing cattle that were slaughtered at market weights su ggest that partitioning of EBW gains can be fully described by the mat hematical formulation used for growing cattle. However, for cattle tha t were restricted in growth, then realimented, the results showed that a model with a transition to the mathematical formulation for mature cattle, during the realimentation phase, accurately predicted the obse rved final composition. These results suggest that the integrated mode l would accurately predict the changes in body composition of cattle o f all ages, under different systems of nutritional management.