Endogenous Amino Acid Loss at the Terminal Ileum of Rats Fed Water-Extractable or Alkali-Extractable Soluble Non-Starch Polysaccharides Obtained from Wheat Bran When Fed with and Without Xylanase

摘要

The objective of these studies was to determine how the endogenous amino acid flow at the terminal ileum of rats is affected by feeding diets containing water extractable or alkali extractable soluble non-starch polysaccharides obtained from wheat bran. In addition, the effect of xylanase on endogenous amino acid flow was studied. In experiment one, 40 Sprague-Dawley rats (190.9±2.0 g) were fed one of four protein-free diets, based on cornstarch, sucrose and soybean oil that contained 0, 20, 30, or 40 g kg 1 of water-extractable soluble non-starch polysaccharides. In experiment two, 40 Sprague-Dawley rats (204.3±1.6 g), were randomly allotted to one of four protein-free diets in a 2 x 2 factorial design with the diets containing 30 g kg 1 of either water-extractable or alkali-extractable soluble non-starch polysaccharides. The diets were fed with or without xylanase (2500 FTU/g) added at the expense of cornstarch. Chromic oxide (6 g kg 1 diet) was included in all diets as an indigestible marker. Both experiments lasted 8 d. The rats were killed on day 8 and the digesta contained in the final 20 cm of the ileum was obtained for assay. The results of experiment one revealed that adding graded levels of water-extractable soluble non-starch polysaccharides significantly increased (linear and quadratic effect; p<0.01) the endogenous flows of amino acid and nitrogen at the terminal ileum. The endogenous loss of nitrogen increased by 19.11 mg for every g kg 1 increase in water-extractable soluble non-starch polysaccharides in the diet. Putrescine and spermine levels in the ileum increased (linear and quadratic effect; p<0.05) as the level of water-extractable soluble non-starch polysaccharides in the diet increased. Acetate, propionate and butyrate levels also increased (linear and quadratic effect; p<0.05) with increasing levels of water-extractable non-starch polysaccharides. In experiment two, with the exception of glycine, dietary supplementation of alkali-extractable non-starch polysaccharides significantly increased the endogenous amino acid loss at the terminal ileum compared with water-extractable non-starch polysaccharides (p<0.05). The addition of xylanase significantly decreased ileal endogenous amino acid loss in rats. The overall results of these experiments indicate that the presence of soluble non-starch polysaccharides increases endogenous amino acid loss at the terminal ileal, which may explain the reduction in the digestibility of crude protein and amino acids commonly observed in animals fed diets containing a high concentration of soluble non-starch polysaccharides.