Effects of supplementary amino acids on available energy of soybean meal determined by difference and regression methods fed to growing pigs

This study was conducted to evaluate effects of inclusion level and supplementary amino acids (AAs) on digestible energy (DE) and metabolizable energy (ME) values of soybean meal (SBM) fed to growing pigs, determined by difference and regression methods. Sixty pigs were fed 10 diets according to a 5 × 2 factorial arrangement. Two control diets contained 97.34% corn without supplementary AAs or 95.61% corn with supplementary AAs. Eight diets were formulated by replacing corn and AAs in control diets with 8%, 15%, 25% and 31% SBM. There was no difference in DE and ME values of SBM determined by difference method as inclusion level of SBM increased or crystalline AAs were added. No difference was observed in DE and ME values of SBM determined by the two methods in diets without supplementary AAs, but the values determined by the difference method were greater (P < 0.05) than those determined by regression method when crystalline AAs were added in diets. In conclusion, inclusion level and supplementary AAs did not affect DE and ME values of SBM calculated by difference or regression methods. There were differences in DE and ME values of SBM determined by the difference method and the regression method when crystalline AAs were added in diets.