Mucin output in ileal digesta of pigs fed a protein-free diet.
Daily outputs of mucin in ileal digesta were estimated in three barrows fed a protein-free diet while administered either saline (SAI) or a complete amino acid mixture (AAI) intravenously. The water soluble-ethanol precipitable fraction of ileal digesta (crude mucin; CM) was used to estimate the composition of mucin in ileal digesta. This fraction exhibited a carbohydrate composition characteristic of mucin and had a high threonine, serine and proline content (40 mol/100 mol). The proportions of soluble gastric and intestinal mucins, approximately 27 and 73%, respectively, were estimated from the N-acetylglucosamine (GlcNAc)/N-acetylgalactosamine (GalNAc) ratio in CM. The daily outputs of soluble mucin, 2.75 and 3.41 g/day from SAI and AAI pigs (p = 0.13), respectively, were determined from the GalNAc outputs in CM, assuming the above contributions of gastric and intestinal mucins. The estimated soluble mucin outputs accounted for more than 99% of the fucose, galactose, GalNAc and GlcNAc in CM. Total mucin outputs in ileal digesta, 5.32 and 5.65 g/day from SAI and AAI Pigs (p = 0.24), respectively, were determined from the total GalNAc output in digesta, assuming soluble and insoluble mucin had similar compositions. Based on these outputs, mucin represented approximately 30, 7 to 22, 15 and 11% of the endogenous threonine, proline, serine and protein, respectively, in ileal digesta. Approximately 74, 76, 100 and 53% of the fucose, galactose GalNAc and GlcNAc, respectively, in ileal digesta from pigs in this study was attributed to mucin. The results from this study demonstrate the importance of mucin as a source of some endogenous amino acids and carbohydrates.
Lien
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Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Canada.
Sauer
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Fenton
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D000116:Acetylgalactosamine / Q000032:analysis; D000117:Acetylglucosamine / Q000032:analysis; D000596:Amino Acids / Q000008:administration & dosage / Q000032:analysis / Q000378:metabolism; D000818:Animals; D018753:Diet, Protein-Restricted; D005643:Fucose / Q000032:analysis; D005690:Galactose / Q000032:analysis; D005766:Gastrointestinal Contents / Q000737:chemistry*; D007082:Ileum; D007262:Infusions, Intravenous; D007413:Intestinal Mucosa / Q000502:physiology*; D008297:Male; D009077:Mucins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D013552:Swine
D000596:Amino Acids; D009077:Mucins; D005643:Fucose; D000116:Acetylgalactosamine; D000117:Acetylglucosamine; D005690:Galactose