Results of the sensitivity analysis for parameters concerning the basic growth model are given in Table 2 and those of the FA model in Table 3. The influence of minLP and PDmax on model predictions was relatively small. A 20% change in minLP resulted only in a 5% change in predictions of total body lipids and FA mass at slaughter. Variation in minLP had little or no effect on palmitic, stearic and oleic acid contents but was negatively correlated with the linoleic acid content. An increase in PDmax resulted in a decrease in lipid and FA mass. For a 20% change in PDmax, a 4% change in body lipid and FA mass was observed. Changes in backfat FA contents were relatively minor, except for linoleic acid, which seem positively correlated with PDmax. The FI had by far the strongest effect on predicted lipid variables. The response of body lipid and FA mass was about three-fold the change in FI. Reducing FI resulted in minor and strong increases of, respectively, palmitic and linoleic acid contents. In contrast, both stearic and oleic acid contents were strongly reduced. An increase of FI had an opposite effect on FA composition, but to a lesser extent.
Concerning model parameters specific to FA metabolism (Table 3), dietFAstore was particularly sensitive to the linoleic (and linolenic) acid content: a 20% variation of dietFAstore implied a 16% change of linoleic acid. The effects on the other FA were relatively minor and opposite to the change of the parameter. As anticipated, variation in novoFAcomp strongly affected backfat FA composition and, as a result of the model structure, it did not affect the linoleic acid content. Changing the value of a single FA in novoFAcomp leads to an obligatory change in the other FA, affecting the backfat FA composition accordingly. Consequently, a 20% increase of palmitic acid in the novoFAcomp led to a 10% increase in palmitic acid and a 5% decrease of both stearic and oleic acids in backfat. Similar responses were observed for the sensitivity of stearic and oleic acid in the novoFAcomp, although results differed somewhat in magnitude.