Soy protein isolate

Effects of increasing dietary protein on standardized ileal digestibility of amino acids in diets fed to growing pigs

Apparent ileal digestibility (AID) of amino acids (AA) is affected by dietary AA levels because of different contributions of endogenous AA to the ileal digesta from pigs fed diets with different levels of AA. Because of the influence of dietary protein and AA on calculated values for AID, values for AID obtained in individual feed ingredients are not always additive in mixed diets. Therefore, values for standardized ileal digestibility (SID) of AA, which are corrected for the basal ileal endogenous losses of AA, are used in diet formulations to avoid the influence of endogenous AA on digestibility values, and SID values are, therefore, additive in mixed diets.

When the direct procedure is used to determine AA digestibility, diets containing cereal grains are sometimes formulated to contain AA below the requirement. In contrast, if the SID of oilseed meals or other protein-rich ingredients are determined, concentrations of AA may be at or above the requirement. Because the influence of the basal endogenous losses of AA is eliminated in the calculations of SID values, it is assumed that values for SID are not influenced by dietary concentrations of AA. However, to our knowledge this hypothesis has not been experimentally verified, but it is an important question because it may influence how diets used in digestibility experiments are formulated. Therefore, four experiments were conducted to test the hypothesis that the SID of AA by growing pigs is not influenced by dietary AA levels.

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Analysis of published data for standardized ileal digestibility of protein and amino acids in soy proteins fed to pigs

C. Pedersen, C, J. S. Almeida, and H. H. Stein. 2016. Analysis of published data for standardized ileal digestibility of protein and amino acids in soy proteins fed to pigs. J. Anim. Sci. 94(Suppl. 3):340-343. Link to full text (.pdf)

Amino acid digestibility in dairy proteins compared with plant proteins

Mathai, J. K., Y. Liu, and H. H. Stein. 2016. Amino acid digestibility in dairy proteins compared with plant proteins. J. Anim. Sci. 94(Suppl. 2):104 (Abstr.) Link to abstract (.pdf)

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Nutritional value of soy products fed to pigs

Stein, H. H., J. A. Roth, K. M. Sotak, and O. J. Rojas. 2013. Nutritional value of soy products fed to pigs. Swine Focus #004. Link to full text (.pdf)

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

Cervantes-Pahm, S. F., and H. H. Stein. 2010. Ileal digestibility of amino acids in conventional, fermented, and enzyme treated soybean meal and in soy protein isolate, fishmeal, and casein fed to weanling pigs. J. Anim. Sci.  88:2674-2683. Link to full text (.pdf)

Digestibility of amino acids in novel soybean products

Raw soybeans contain antinutritional factors such as trypsin inhibitors (TI) and lectins.  The production of soybean meal involves a heating step, which reduces these anti-nutritional factors. However, conventional soybean meal contains compounds which can cause digestive disturbances in weanling pigs. Soybean meal is therefore limited in pig starter diets. Other protein sources, such as fish meal, casein, and soy protein isolate, are used for young pigs.

Two new soybean products were recently introduced to the U.S. feed market.  Fermented soybean meal (FSBM) and enzyme-treated soybean meal (ESBM) are believed to have a lower concentration of antinutritional factors and a higher concentration of crude protein and amino acids than conventional soybean meal.  They are also believed to be better tolerated by young pigs. However, not much is known about the digestibility of the protein in these two products.

This experiment was conducted to compare the digestibility of amino acids in weanling pigs of FSBM, ESBM, conventional de-hulled soybean meal, fish meal, casein, and soy protein isolate.

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