GAM analysis incorporating both linear and smoothing components. Parameters df Chi-square Pr> chisq Linear(Citrulline) 1 14.4400 0.0004** Linear(Lysine) 1 1.040 0.315 Linear(Histidine) 1 2.280 0.139 Linear(Arginine) 1 0.078 0.784 Spline(Citrulline) 2 8.596 0.014** Spline(Lysine) 2 0.145 0.930 Spline(Histidine) 2 6.284 0.043** Spline(Arginine) 2 2.141 0.343 GAM analysis incorporating only linear components. Linear(Citrulline) 1 13.0320 0.0007** Linear(Lysine) 1 0.476 0.494 Linear(Histidine) 1 1.638 0.205 Linear(Arginine) 1 0.0001 0.989

Table 3: Model analysis of deviance tests. Two GAM analyses are shown. For each, the DF, degrees of freedom and dominant factors significant at the level alpha=0.1 (*) and 0.05(**) are shown for each parameter.