The use of 15N-labeled dietary proteins for determining true ileal amino acid digestibilities is limited by their rapid recycling in the endogenous secretions of pigs
article
We assessed the use of 15N-labeled dietary proteins as a possible tool for the determination of the true ileal amino acid (AA) digestibility in pigs. The first experiment was designed to study the dietary N excretion pattern at the ileum subsequent to the ingestion of a single 15N-labeled meal. In a second experiment, we compared ileal endogenous AA outputs and true AA digestibility estimates obtained in pigs ingesting 15N-labeled dietary proteins in a single meal vs. intravenous infusion of [15N]Ieucine for 10 d during the ingestion of a pea-based diet and a protein-free starch diet. The proportion of endogenous N found in the ileal digesta differed when the label was delivered orally (50%) vs. intravenously (72%) and changed with time. As a consequence, the true ileal AA digestibilities measured with labeled diets were lower. A third experiment demonstrated that this was due to the rapid recycling of labeled dietary N in endogenous moieties, because 15N was found in blood within 10 min of consuming the labeled meal, within 50 min of consumption in pancreatic enzymes, 90 min in bile and 4 h in ileal mucins. We conclude that the use of 15N-labeled meals for determination of true ileal AA digestibilities is limited by the fast recycling of dietary N in endogenous secretions following a single 15N-labeled meal. The accuracy of results will depend on meaningful estimates of AA flow during a limited period and accurate estimates of 15N in AA.
Topics
15NEndogenousIleal digestibilityPigsAmino acidAmino acid blood levelAmino acid metabolismAnimal experimentDigestionNonhumanProtein secretionSmall intestine absorptionSwineAnimalBloodChemistryEnzymologyMetabolismPhysiologyProtein intakeTimeWheatAmino AcidsAnimalsBileDietary ProteinsDigestionEnzymesIleumLeucineMaleMucinsNitrogenNitrogen IsotopesPancreasPeasStarchSwineTime FactorsTriticum
TNO Identifier
233433
ISSN
00223166
Source
Journal of Nutrition, 126(9), pp. 2188-2198.
Pages
2188-2198
Files
To receive the publication files, please send an e-mail request to TNO Repository.