Amino Acid Bioavailability

An International Committee on Terminology to Report Amino Acid Bioavailability and Digestibility issued a report on the terminology used to describe the bioavailability and ileal digestibility of amino acids in swine feed ingredients.  The Committee developed a detailed technical review of the advantages and disadvantages for various amino acid digestibility measurements.  Briefly, apparent ileal digestibility (AID) is calculated by comparing total ileal outflow of amino acids (sum of endogenous losses and undigested dietary amino acids) to dietary amino acid intake.   One disadvantage of AID values for the various feed ingredients is that they are not additive in formulating feeds. This disadvantage is partially corrected for in standardized ileal digestibility (SID) by accounting for endogenous losses of amino acids.  While correcting AID values for both endogenous losses and specific losses caused by the ingredient’s characteristics (type of fiber and antinutritional factors) results in the true ileal digestibility (TID).  Agreement on terminology and improving measurements to better define the quality of various feed ingredients is important in formulating swine rations.  The Committee suggested that SID values should be used for formulating swine feeds until the more accurate TID values become available.

So how does this relate to soybean meal use?  In the paper, the Committee provides a table that reported various ileal digestibility values for selected protein supplements that have use in swine rations.



These data clearly demonstrate the relatively high quality of soybean meal, regardless of ileal digestibility measurement, when compared to other oil seed meals that can be used in swine rations.  These data also show that improperly processed soybean meal can be easily identified using ileal digestibility values.  One can predict that growth studies will reflect the quality differences between the two soybean meals.  The Committee encouraged the use of SID values in formulating swine rations since they are available and reflective of the protein quality of feed ingredients.  Improvements, or refinements, in feed formulation will continue to show the value of soybean meal in highly productive swine rations.

Stein, H.H., and co-workers.  2007.  Invited review: Amino acid bioavailability and digestibility in pig feed ingredients: Terminology and application.  J. Animal Sci. 85: (172-180).