Different Expressions of Dietary Protein and Amino Acid Digestibility in Pig Feeds and Their Application in Protein Evaluation: A Theoretical Approach
Titel:
Different Expressions of Dietary Protein and Amino Acid Digestibility in Pig Feeds and Their Application in Protein Evaluation: A Theoretical Approach
Auteur:
Boisen, Sigurd Moughan, Paul J.
Verschenen in:
Acta agriculturae Scandinavica. Section A, Animal science
Paginering:
Jaargang 46 (1996) nr. 3 pagina's 165-172
Jaar:
1996-08-01
Inhoud:
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 mixtures used to dilute the experimental mixtures. Real digestibilities (including in vitro measures) are direct measures of the digestibility of a feed protein, and are not influenced by endogenous loss. Values for apparent and real protein and amino acid digestibility are. not directly suitable for use in practical protein evaluation systems but those for net or true digestibility can be used. Both sets of values can be calculated from determinations of either real or apparent digestibility. For net digestibility, total endogenous protein loss is included in the digestibility coefficients. For true digestibility, only the extra endogenous loss is included in the digestibility coefficients while the basal endogenous loss needs to be standardized and included in the estimate of amino acid requirements.
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