Dietary Carbohydrate Utilization by Fish
Aquaculture production is forecast to nearly double by the year 2010. Increased production can only be sustained with a concomitant increase in the production of aquafeeds. Presently, the protein source of choice in most aquafeeds is fish meal. Global fish meal production has remained relatively static over the past two decades, and there is no evidence to suggest that it will increase in the future. Therefore, alternative protein sources to fish meal will have to be found. Plant protein sources have been identified to have the greatest potential to replace fish meal protein. However, plant ingredients contain significant quantities of carbohydrates. The ability of fish to utilize dietary carbohydrates as energy sources to spare protein for growth varies, both among and within species. This review discusses the variability of carbohydrate utilization by fish commonly produced by aquaculture. Factors that affect carbohydrate utilization as an energy source to spare protein are carbohydrate origin, inclusion content, physical state, and molecular complexity. There appears to be potential for the use of supplemental enzymes to enhance carbohydrate utilization; however, care must be exercised with the use of such products as some of the breakdown products, particularly from nonstarch polysaccharides, such as galactose and xylose, are not tolerated by most fish if digested. The increased availability of these monomers may be detrimental to fish growth performance and health. Warmwater omnivorous fish have a greater potential to utilize dietary carbohydrate as an energy source to spare protein, than do coldwater and carnivorous species which utilize dietary carbohydrate poorly or not at all. This will place restrictions on the use of plant protein sources, which contain significant quantities of .carbohydrate in diets for coldwater and carnivorous fish. Consequently, the production costs of diets for warmwater omnivorous species will be cheaper than for coldwater and carnivorous species. This may have implications in the future for the selection of suitable species of fish to provide protein for human consumption.
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Document Type: Research Article
Affiliations: Univeisity of Idaho, Hagerman Fish Culture Experiment Station, 3059-F National Fish Hatcheiy Road, Hagerman, Idaho 83332, USA. [email protected]
Publication date: October 1, 2003