Modeling the Physiological Growth of Swine Part II: Validation of Model Logic and Growth Concepts
This is the second report in a three-part series on development and validation of the NCPIG computer model. For the model describing the physiological growth of swine, three simulation experiments were conducted to mimic experimental treatments (control, medium, high growth) for contemporary crossbred swine. For the two controlled growth experiments, the model adequately simulated liveweight growth (± 1 kg), but was unable to achieve the liveweight growth rate of 1 kg/day of the experimental animals in the high growth treatment. The simulated values for the empty body components of fat, protein, water and ash were within ± 1.0% (empty body weight basis) of the observed values for the control and medium growth rate treatments, but for the high growth treatment, the model was less accurate in fat and water retention (–3% for fat; + 2.7% for water on empty body basis). Simulated feed intake ranged from + 4.1% to –3.5% of the average experimental intake for the three treatments. Feed to gain ratios were higher than those found for the experimental pigs. The results indicate that the NCPIG model adequately simulates controlled intake conditions, but improved model logic is needed to more accurately simulate an ad-lib growth situation where the animal is fed a high energy diet.