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

Abstract

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 (εi), the N requirement for maintenance (NO), 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 ε₈ (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 No, eh ep, or Ld: Pd decreased Pd by only 0.20 g/day. The analysis identified εi, Pr, and Em as critical parameters within the growth model.

Keywords:

• pigs
• models
• simulation
• sensitivity analysis
• nitrogen metabolism