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The mechanism of the anti-nutritive activity of isolated wheat pentosans was investigated by examining the roles of digesta viscosity and gut microflora in broiler chickens. Wheat pentosans were isolated by alkaline extraction and purified by sequential treatment with pancreatin, α-amylase and lichenase, and high-speed centrifugation. Some of the pentosans were depolymerised using a β-xylanase, which reduced the relative viscosity of the polysaccharides 4 fold. Inclusion of 35g alkali-extractable pentosans (containing 854g arabinoxylans/kg DM) per kg diet significantly (P<0.05) depressed broiler performance and the viscosity of the digesta of these birds was significantly (P<0.05) higher than that of controls. Addition of the same amount of depolymerised pentosans had no significant effect on bird performance and had less effect on digesta viscosity. Supplementation of the diet containing wheat pentosans (30g/kg) with procaine penicillin (150mg/kg) did not improve bird performance. It is concluded that the wheat pentosans elicit their anti-nutritive activity predominantly through increasing the viscosity of digesta. |
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