PREDICTION OF PROTEIN ACCRETION, SUPPORT COSTS AND LIPID ACCRETION INTHE GROWING FEMALE PIG AND DRY SOW

A predictive model of the female pig was developed to evaluate an alte rnative approach to conventional energetics. The emphasis in this appr oach focused on derivation of variable support costs rather than fixed maintenance, and the role of protein as a major driving force in grow th and development. Protein support costs were incorporated in an equa tion developed to predict protein accretion under various live weight and nutrient intake combinations. Maximal rates of protein accretion w ere genetically determined, and varied with live weight in a skew para bolic function. Published rates of protein and lipid accretion for fem ale pigs (1.8-154 kg live weight) were used to evaluate the relationsh ip between energy support costs (Es(T)), protein and energy intake lev els. Es(T) was related to body protein content and rate of protein acc retion (r2 = 0.989). The resultant equations for protein and energy su pport costs and rate of protein accretion were used in the context of a complete model to estimate lipid accretion and live weight gain. Act ual vs predicted rates of lipid accretion agreed well (r2 = 0.972). Pr ediction of protein and lipid accretion and live weight change for gro wing pig data not used in parameter estimation closely followed the ob served magnitude and response. The derived model equations provided a system to allow analysis of compositional changes in the growing and n on-reproducing female pig, in addition to providing a framework for pr edicting these responses in the reproducing sow.