The Journal of nutrition
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The Journal of nutrition · Oct 1991
Composition of nitrogen-containing fractions in digesta from the distal ileum of pigs fed a protein-free diet.
The levels of free, peptide-bound and protein-bound amino acid nitrogen in endogenous N at the distal ileum of the pig were determined when the digestion of protein after sample collection was minimized. Six 14-kg pigs were fed a protein-free diet and samples of digesta from the distal ileum were collected. The digesta were centrifuged and the supernatant ultrafiltered. ⋯ The mean amounts of nitrogen from individual amino acids (free + peptide) in the ultrafiltrate (expressed as percentages of the total nitrogen for the respective amino acid in whole ileal digesta) were low, ranging from 3.0% for isoleucine to 16.6% for proline. The finding that free amino acid N + peptide N is a small fraction of total N in endogenous ileal digesta supports the use of a new method for determining endogenous loss, whereby the animal is fed hydrolyzed casein and the ileal digesta are ultrafiltered. The high-molecular-weight fraction provides a measure of endogenous nitrogen loss.