Ileal digestibility of amino acids in conventional, fermented, and enzyme-treated soybean meal and in soy protein isolate, fish meal, and casein fed to weanling pigs.

An experiment was conducted to determine the apparent (AID) and standardized (SID) ileal digestibility of CP and AA in weanling pigs of 4 soybean products, fish meal, and casein. The 4 soybean products were conventional dehulled soybean meal (SBM), soy protein isolate (SPI), fermented soybean meal (FSBM), and enzyme-treated soybean meal (ESBM). Seven weanling barrows (initial BW: 10.9 +/- 2.3 kg) were individually fitted with a T-cannula in the distal ileum. The barrows were allotted to a 7 x 7 Latin square design with 7 diets and seven 7-d periods. Six cornstarch-based diets were prepared using each of the protein sources as the sole source of CP and AA. An N-free diet was used to measure basal endogenous losses of CP and AA. Results showed that except for Lys, the AID and SID of AA in FSBM was not different from SBM, and with a few exceptions, the AID and SID of most AA in SBM, FSBM, and ESBM were not different from each other and from the AID and SID of AA in fish meal. Likewise, the AID and SID of AA in ESBM and SPI were not different, but the AID and SID of most AA in SPI were greater (P < 0.05) than in SBM and FSBM. The AID and SID of most AA in SPI were not different from the AID and SID of AA in casein. In conclusion, FSBM and ESBM had similar SID of most AA as SBM, but SPI has the greatest SID of AA among the 4 soybean products. Casein had the greatest SID of AA among the protein sources studied.