Encyclopedia of Animal Science Bioavailability: Amino Acids

The main goal in formulating animal feeds is to supply nutrients in amounts and relative proportions that optimize performance. This is particularly important with respect to amino acids (AA), as the feed ingredients used to supply AA are often expensive. Furthermore, any AA supplied in excess is deaminated and the resulting nitrogen excreted, thus posing a potential environmental problem. Because animals do not store excess AA in the body, the exact needs for protein synthesis need to be supplied each day. Therefore, the AA requirements of the animal and the dietary concentration of AA need to be known. However, availability of AA in many feedstuffs is not known, and thus, digestibility measurements are used as reasonable estimates of availability. The current contribution covers aspects of bioavailability of AA in feed ingredients with particular emphasis on pig nutrition. The determination of AA digestibility coefficients and the application to estimate bioavailability is discussed.