Print Email Facebook Twitter 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 Title 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 Author Leterme, P. Théwis, A. François, E. van Leeuwen, P. Wathelet, B. Huisman, J. Instituut voor Landbouwkundig Onderzoek en Biochemische Produkten TNO Publication year 1996 Abstract 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. Subject Biology15NEndogenousIleal digestibilityPigsAmino acidAmino acid blood levelAmino acid metabolismAnimal experimentDigestionNonhumanProtein secretionSmall intestine absorptionSwineAnimalBloodChemistryEnzymologyMetabolismPhysiologyProtein intakeTimeWheatAmino AcidsAnimalsBileDietary ProteinsDigestionEnzymesIleumLeucineMaleMucinsNitrogenNitrogen IsotopesPancreasPeasStarchSwineTime FactorsTriticum To reference this document use: http://resolver.tudelft.nl/uuid:00920243-5f31-45c7-9360-1dc4d4f62f30 TNO identifier 233433 ISSN 0022-3166 Source Journal of Nutrition, 126 (9), 2188-2198 Document type article Files To receive the publication files, please send an e-mail request to TNO Library.