Prediction of the standardized ileal true digestibility of amino acids from the chemical composition of oilseed meals in the growing pig

Digestibility experiments using growing pigs fitted with an ileorectal anastomosis were performed to measure the standardized ileal true digestibility (ITD) of amino acids in five cotton seed meals (CSM) and three palm kernel meals (PKM), differing in their level of non starch polysaccharides (NSP), as expressed by NDF content and the nitrogen content of NDF (N NDF). The NDF content in CSM ranged from 273 to 475 g kg−1 on dry matter (DM) and the crude protein content from 384 to 506 g kg−1 DM. The latter values were not correlated with the NDF content. For PKM, NDF varied from 592 to 686 g kg−1 and the crude protein content from 151 to 177 g kg−1. Results obtained for CSM clearly demonstrate a curvilinear relationship, except for methionine, between ITD of amino acids and NDF content. Furthermore, if the composition of the CSM as ash, fat, total nitrogen, nitrogen from NDF (N NDF) and total gossypol (TGOS) contents is known (g kg−1 DM), the quantity of digestible amino acid can be predicted for lysine, threonine and tryptophan with reasonable precision, but less for sulfur amino acids. As an example for lysine, dLys ( g kg −1 DM )=6.5116(1.0939)+0.1411 N (0.0158)−0.1673 NNDF (0.0091)−0.0124 NDF (0.0010) R2=0.993. For PKM, the relationships were more difficult to assess because of a narrow range in NDF level and the heterogeneity of response between pigs, especially for the higher NDF contents. In addition, the current data confirmed that the nitrogen content in the NDF fraction of NSP, often considered in ruminant protein nutrition, could be also an useful predictor of true ileal digestible values for selected amino acids in the pig