Amino acid digestibility and poultry feed formulation: expression, limitations and application

The nutritional value or quality of dietary proteins used for poultry feed formulation varies: amino acid availability is an important measure of protein quality. Determination of ileal digestibility values has become the preferred method for estimating amino acid availability. This review discusses the different approaches to the expression of digestibility results, including correction for endogenous loss and the derivatisation of standardised values. Sources of variation in values include, the assay protocol, anti-nutritional factors in feedstuffs and feed milling. Feed formulating with ileal digestibility values should allow higher dietary inclusion levels of protein feedstuffs of lower quality provided that values of different feedstuffs are additive, the age of the bird and the use of feed enzymes are considered. An Australian data set of "ileal digestible amino acid values in feedstuffs for poultry" that has recently be published is described. This overview is intended to stimulate interest in the generation and application of ileal digestibility as a method for estimating amino acid availability in poultry nutrition.