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 partitioned gains in empty body weight (EBW) to fat and fat-free matter. These models 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 growing to the mature mathematical formulation. This transition point and the rate at which the transition occurs between the two mechanisms were estimated from published data. Evaluation results with data on steers 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 prediction of empty body composition at final slaughter. Evaluation results with full-fed growing cattle that were slaughtered at market weights suggest that partitioning of EBW gains can be fully described by the mathematical formulation used for growing cattle. However, for cattle that 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 observed final composition. These results suggest that the integrated model would accurately predict the changes in body composition of cattle of all ages, under different systems of nutritional management.