The Use Of N-15-Labeled Dietary Proteins For Determining True Ileal Amino Acid Digestibilities Is Limited By Their Rapid Recycling In The Endogenous Secretions Of Pigs
[en] 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-leucine 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 ¡leal 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 ¡leal mucins. We conclude that the use of 15N-labeled meals for determination of true ¡leal 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.
Leterme, Pascal; Faculté Universitaire des Sciences Agronomiques de Gembloux - FUSAGx > Unité de Zootechnie
Thewis, André ; Université de Liège - ULiège > Gembloux Agro-Bio Tech
Francois, Etienne; Centre de Recherches Agronomiques - CRA W, Gembloux, Belgique > Station de Chimie et Physique Agricoles
Van leeuwen, Piet; TNO-ILOB
Wathelet, Bernard ; Université de Liège - ULiège > Gembloux Agro-Bio Tech
Huisman, Joop; TNO-ILOB
Language :
English
Title :
The Use Of N-15-Labeled Dietary Proteins For Determining True Ileal Amino Acid Digestibilities Is Limited By Their Rapid Recycling In The Endogenous Secretions Of Pigs
Publication date :
1996
Journal title :
Journal of Nutrition
ISSN :
0022-3166
eISSN :
1541-6100
Publisher :
American Society of Nutritional Sciences, Bethesda, United States - Maryland
IRSIA - Institut pour l'Encouragement de la Recherche Scientifique dans l'Industrie et l'Agriculture F.R.S.-FNRS - Fonds de la Recherche Scientifique TNO-ILOB, Wageningen, Belgique
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