Soybean meal is an excellent source of protein for pigs because of its excellent amino acid profile and its high amino acid digestibility. However, the presence of anti-nutritional factors such as trypsin inhibitors, lectins, oligosaccharides, and antigenic proteins reduces the inclusion level in weanling diets.  The oligosaccharides can be reduced or eliminated by processing the soybean meal via aqueous ethanol extraction, fermentation, or enzymatic treatment.  Reducing the concentration of oligo­saccharides will increase the concentration of other nutrients such as crude protein.

Soy protein concentrate and soy protein isolate have low levels of stachyose and raffinose and antigenic proteins, and greater digestibility of amino acids and energy than soybean meal.  Enzyme-treated soybean meal also has low concentration of oligosaccharides, and fermented soybean meal contains no stachyose or raffinose.  However, fermented soybean meal sometimes has a reduced digestibility of lysine because of Mailard reactions caused by excess heating during drying after fermentation, but this is usually not observed in enzyme-treated soybean meal where the amino acid digestibility is similar to soybean meal.