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The non-starch polysaccharides (NSPs) of cereals exhibit anti-nutritive activity when present in broiler diets. The high levels of arabinoxylans (pentosans) in rye and β-glucans in barley are responsible for the poor nutritive value of these cereals. Australian wheats vary considerably in their nutritive value with some having very low apparent metabolizable energy (AME <13 MJ/kg) values. Recent studies have shown that the low AME wheat problem is probably due to the variation in the levels of the water-soluble wheat NSPs which are predominantly pentosans. When pentosans isolated from rye or wheat are added to broiler diets, dose-dependent depressions in nutrient digestion and growth occur. Several treatments have been shown to be effective in improving the nutritive value of cereals. Soaking the cereals in water or adding NSP-degrading enzymes decreases the anti nutritive activity of the NSP. Addition of antibiotics to diets also has been shown to increase the nutritive value of diets with high levels of NSP suggesting that the action of these materials is, at least in part, mediated by the gut microflora. |
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