Sensitivity analysis on a model simulating the digestion and metabolism of nitrogen in the growing pig

The relative effect on whole‐body protein deposition of changes to key parameters of a computerised model simulating the digestion and metabolism of nitrogen (N) in the growing pig was determined. The parameters investigated included: the ‘ideal’ level of the first limiting amino acid for pig growth (ε i ), the N requirement for maintenance (N O ), the maximum rate of protein deposition physiologically possible ( Pr ), the energy required for maintenance ( Em ), the ratio of minimum lipid to protein in daily tissue deposition ( Ld: Pd ), the energy cost of depositing 1 g protein ( ep ), and the energy cost of depositing 1 g lipid ( el ). Each model parameter was made either proportionally (0.05, 0.10, 0.15, 0.20) greater or less than its standard value, and simulated values of protein deposition ( Pd ) were generated. A 1% increase in Pr gave an increase in Pd of 1.35 g/day. A 1% increase in ε 8 (isoleucine) gave a decrease in Pd of 0.98–1.96 g/day, whereas a 1% increase in Em led to a decrease in Pd of 0.80 g/day. A 1% increase in N o, eh ep , or Ld: Pd decreased Pd by only 0.20 g/day. The analysis identified ε i, Pr , and Em as critical parameters within the growth model.