Validation of a mathematical model to explain variation in apparent ileal amino acid digestibility of diets fed to pigs.

Var ia t ion in apparent ileal digestibility o f amino acids w i t h i n the same diet is partly related to the amino acid composition o f feed protein and endogenous protein. Mathematical model which estimate the apparent ileal amino acid digestibility coefficients, based on apparent ileal digestibility coefficients o f the diet protein and the amino acid composit ion o f the diet protein as factors, has been described i n literature. I n the present study, apparent ileal amino acid digestibilities o f pigs fed eighteen different diets w i th a wide range o f different protein sources were determined and the mathematical model f rom the literature was validated. Results o f the validation showed that the mathematical model explained 60-94% o f the variat ion in apparent ileal amino acid digestibility o f sixteen diets. However, variations for diets w i t h Phaseolus beans and meat and bone meal as protein sources were explained by only 45 and 27%, respectively. Standard error o f prediction (SEP) was about 2-3 times higher as compared to the standard error o f the mean (SEM) o f the determinations between animals. For most o f the feedstuffs, the factors o f the model explain the main part o f the variat ion in apparent amino acid digestibility ( R 2 > 0.60). I f the explained part o f the variat ion in apparent amino acid digestibility is small, R 2 < 0 . 5 0 , other factors which are not included in the model have major effects on apparent digestiblity o f the amino acids. K E Y W O R D S : pigs, ileal digestibility, amino acids, mathematical model 304 LEEUWEN V A N P. ET A L .