[en] The current 15N-leucine infusion technique may overestimate the ileal endogenous nitrogen losses in pigs. To determine the reason, we infused four cannulated pigs intravenously, fed them a pea-based diet with 15N-leucine, and examined some methodological variables. Neither the blood sampling time nor the choice of precursor pool (total N or amino acid N of deproteinized plasma) or the method of estimation of the isotopic equilibrium level significantly affected the results. On the other hand, the 15N-enrichment of purified mucin, isolated from ileal digesta, was higher than that of the plasma amino acid pool (0.114 vs. 0.077 atom % excess). The endogenous proportion of the labeled amino acids (Ala, Gly, Ile, Leu and Val) in the ileal digesta ranged from 23 (Leu) to 74% (Ala), compared with 70% for total N. The low value of leucine was ascribed to the constant marker infusion condition. In pigs infused with 13C-leucine, a similar endogenous proportion was obtained for lumenal leucine with 13C-leucine and 15N-leucine infusion. However, the 13C-enrichment of the leucine bound to mucin was markedly lower than that of plasma leucine (38%). The endogenous amino acid flows were also estimated by combining the ileal N flow measured with 15N and the endogenous amino acid profile obtained by means of an N-free diet. They were different from those obtained with the 15N-amino acid dilution technique. We conclude that the precursor pool currently used (plasma total N or total a-amino acid N pools) is a poor indicator of the enrichment of the secretions and that the infusion of one labeled amino acid is not sufficient to extend the method at the amino acid level.
Disciplines :
Animal production & animal husbandry Agriculture & agronomy
Author, co-author :
Leterme, Pascal; Faculté Universitaire des Sciences Agronomiques de Gembloux - FUSAGx > Unité de Zootechnie
Seve, Bernard; Inra > Station de Recherches Porcines
Thewis, André ; Université de Liège - ULiège > Gembloux Agro-Bio Tech
Language :
English
Title :
The Current N-15-Leucine Infusion Technique Is Not Suitable For Quantitative Measurements Of Ileal Endogenous Amino Acid Flows In Pigs
Publication date :
1998
Journal title :
Journal of Nutrition
ISSN :
0022-3166
eISSN :
1541-6100
Publisher :
American Society of Nutritional Sciences, Bethesda, United States - Maryland
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