ARTICLE FEED & ADDITIVE MAGAZINE January 2024 55 Plant-based ingredients are the most cost-efficient alternative feed for fish in the aquafeed industry. Non-starch polysaccharides (NSPs) reduce the digestibility and bioavailability of nutrients in fish. NSPs are indigestible carbohydrates that can promote microbial growth in the gut. These prebiotics have shown beneficial effect on fish growth and health. These changes in GIT altogether stimulate the immune system, thus, enhancing the host’s protection against infections. ROLE OF NON-STARCH POLYSACCHARIDES (NSP) AND INDIGESTIBLE OLIGOSACCHARIDES IN FISH NUTRITION Ranju Kumari Mfsc scholar Department of Fish Nutrition and Feed Technology, ICAR-Central Institute of Fisheries Education, Mumbai, India Feed costs account for over 50% of the variable costs in most aquaculture operations, therefore applying the best feeding strategy can have a significant impact on optimizing profit, which is the primary goal of commercial aquaculture. Fish meal due high protein content and favourable amino acid profile is an important protein source among commercial feeds and is preferred by fish culturists, however, due its restricted production (which increases its cost), the use of plant-based ingredients is increasing currently. Plant-based ingredients so far are the most cost-efficient alternative feed for fish in the aquafeed industry. This has increased the dietary content of indigestible carbohydrates such as non-starch polysaccharides (NSP) or dietary fibers which reduces the feed digestibility and bioavailability of nutrients. Non-starch polysaccharides (NSPs) are a complex group, composed predominantly of linked monomers of hexoses and pentoses, e.g., galactose, glucose, arabinose, xylose and mannose that cannot be digested in fish and hence reduces the apparent digestibility of the diet and has negative impacts on growth. This is because the enzymes such as β-glucanases or β-xylanases that digest NSPs are scarce or absent in fish. Thus, the dietary NSPs remain indigestible and cannot be used as an energy source. NSP-containing diets in fish has slower rate of gastro-intestinal passage and also shown to reduce the availability of nutrients. Through proper management of the NSPs in these plant materials, plant resources can very well be utilised as cheaper fish feed ingredients. The utilisation of exogenous enzymes (β-glucanases and β-xylanases) in feed processing decrease the negative effects of NSP and thus improve the nutritive value of feed. Moreover, NSPs such as β-glucans and mannose promote colonisation and microbial growth in the gut, thereby acting as immunostimulants. The hydrolysed products of NSP, so called as indigestible oligosaccharides (or prebiotics) have shown beneficial effect on fish growth and health. Indigestible oligosaccharides are small fragments of carbohydrates (in between of simple sugars and
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