Digestible amino acids for poultry and swine

A review and comparison of feedstuff amino acid digestibility values for poultry and swine is presented and the use of amino acid digestibility and availability is discussed. The effect of overprocessing on amino acid digestibility of oilseed meals is also reviewed. In general, true digestible amino acid values determined in cecectomized roosters are 5–10% higher than apparent digestibility values determined in ileal-cannulated pigs. Several studies have shown beneficial responses to formulating diets based digestible amino acid values vs. total amino acid values. However, feedstuff amino acid digestibility values determined via balance assays are often higher than amino acid availability values determined by slope-ratio growth assays. In addition, recent work with pigs suggests that the ileal digestibility assay overestimates the amount of amino acids available or utilizable for protein synthesis. Finally, overprocessing of oilseed meals greatly reduces the amount of digestible or available lysine, whereas other amino acids are usually much less affected. Protein solubility in KOH is a good in vitro assay for detecting decreased protein quality due to overprocessing and the use of Coomassie Blue dye simplifies and reduces the time required to conduct the assay.