Different Expressions of Dietary Protein and Amino Acid Digestibility in Pig Feeds and Their Application in Protein Evaluation: A Theoretical Approach

Abstract

Abstract There is a distinction between the terms apparent, true, real, and “net” ileal protein and amino acid digestibility. For low-protein feedstuff's, “apparent” values relate directly to the feedstuff and are accurate estimates of net digestibility. For diluted protein-rich feedstuffs, apparent values underestimate the net digestibility, which, however, can be obtained from apparent digestibility by mathematical extrapolation. “True” digestibility values have traditionally been obtained by correcting ileal digesta flows for endogenous protein determined after feeding an N-free mixture. Such values are not affected by the protein content of the test diet (degree of dilution) but are generally underestimated and influenced by the amount of endogenous protein loss induced by the N-free mixture. True digestibility determined using enzyme hydrolysed casein includes the minimal or “basal” endogenous loss induced by protein-containing feedstuffs and is, by definition, not influenced by different N-free mixt...