An experiment was conducted to determine the apparent ileal digestibility (AID) and the standardized ileal digestibility (SID) of the crude protein and amino acid in four processed soybean products, in conventional dehulled soybean meal (SBM), and in a conventional 00-rapeseed expeller meal (RSE). The four processed soybean products included two sources of enzyme-treated soybean meal (ESBM-1 and ESBM-2), an extruded soybean meal (ESBM), and a soy protein concentrate (SPC). Weanling barrows weighing about 9.3 kg were surgically equipped with a T-cannula in the distal ileum. Twenty-seven pigs were randomly allotted to a cornstarch-based diet where the test protein ingredient was the only source of crude protein and amino acid. Two groups of pigs were fed an N-free diet for calculating basal endogenous losses of crude protein and amino acid.

The digestibilities studies results are shown in the following table. Generally, the digestibilities of the five soy-based ingredients were not greatly different. The digestibilities of crude protein and some amino acids were significantly greater (P›0.05) for the one enzyme-treated soybean meal compared to the higher protein SPC. Relative large differences in digestibilities were observed comparing the soy-based ingredients compared to the rapeseed meal. The results of this research study indicates that although processing of SBM results in increased concentration of crude protein, processing may also reduce the digestibility of AA, which is likely due to heat damage during processing.

Digestibilities of crude protein and amino acids in enzyme-treated soybean meal, extruded soybean meal, soy protein concentrate, conventional dehulled soybean meal, and a conventional 00-rapeseed expeller meal fed to pigs.