Prediction of protein accretion, support costs and lipid accretion in the growing female pig and dry sow

A predictive model of the female pig was developed to evaluate an alternative approach to conventional energetics. The emphasis in this approach focused on derivation of variable support costs rather than fixed maintenance, and the role of protein as a major driving force in growth and development. Protein support costs were incorporated in an equation developed to predict protein accretion under various live weight and nutrient intake combinations. Maximal rates of protein accretion were genetically determined, and varied with live weight in a skew parabolic function. Published rates of protein and lipid accretion for female pigs (1·8-154 kg live weight) were used to evaluate the relationship between energy support costs (Es), protein and energy intake levels. Es was related to body protein content and rate of protein accretion (r = 0·989). The resultant equations for protein and energy support costs and rate of protein accretion were used in the context of a complete model to estimate lipid accretion and live weight gain. Actual vs predicted rates of lipid accretion agreed well (r = 0·972). Prediction of protein and lipid accretion and live weight change for growing pig data not used in parameter estimation closely followed the observed magnitude and response. The derived model equations provided a system to allow analysis of compositional changes in the growing and non-reproducing female pig, in addition to providing a framework for predicting these responses in the reproducing sow