No abstract

1. The mechanism of the anti-nutritive activities of soluble non-starch polysaccharides (NSPs) in broiler diets was investigated with emphasis on the inter-relationship between viscosity and fermentation along the gut. Isolated soluble NSP were added to a control diet to effect high gut viscosity, and in vivo depolymerisation of the NSP was achieved using a commercial glycanase. 2. Addition of soluble NSPs significantly (P < 0.01) increased gut viscosity, reduced the AME of the diet and depressed the growth and FCE of the birds. Enzyme supplementation of the NSP-enriched diet reversed the adverse effects, increasing (P < 0.01) weight gain, FCE and AME. Comparisons of the viscosities (mPa) in birds fed on the NSP-enriched diet and the same diet supplemented with enzyme were respectively: 11.9 v. 2.3 in the duodenum; 78.3 v. 4.4 in the jejunum and 409.3 v. 10.8 in the ileum. 3. Caecal volatile fatty acid concentration was markedly (P < 0.01) elevated by enzyme supplementation, whereas ileal fermentation was inhibited. 4. Microscopic examination revealed that, among birds fed on the NSP-enriched diet, there had been extensive small intestinal fermentation, which was eliminated by the enzyme supplementation. 5. Addition of a synthetic antibiotic (Amoxil) had no beneficial effects. 6. The current study demonstrated that increased fermentation occurs in the small intestine when a large amount of viscous NSPs is present in the diet and this is detrimental to the performance and well-being of poultry.

1. To study gut health, a multi-pronged approach is necessary. It should be considered from the point of view of immunology, microbiology and nutrient supply. 2. The impact on gut health often comes from microbial imbalance in the gut, which will be exacerbated if antibiotics are withdrawn from feed. 3. Any gut damage caused by pathogens will lead to poor gut health, which will, in turn, affect nutrient utilisation efficiency. Subclinical forms of infection with no obvious signs of lesions are often financially more devastating than acute, short-term infections. Necrotic enteritis in poultry is one such example. 4. Dietary factors that modulate the immune system and gut microflora should be considered when formulating diets and managing feeding practices.