UNDERSTANDING PHYSICAL, FUNCTIONAL AND NUTRITIONAL ASPECTS OF (RICE) STARCH IN AQUAFEED AND FEED FORMULATION

摘要

Starch is an often-undervalued macronutrient of aquafeed due to low cost of starch sources compared to protein and oil. Other reasons for this is the absence of a real nutritional requirement, low digestibility for fish and a lack of understanding ofstarch benefits in aquafeed.The main purposes of starch inclusion in aquafeed are its binding and expansion properties. Starch serves as the binding agent to glue the blend of ingredients together and helps to create an ingestible shape for the fish in the form of a pellet. In aquafeed production we need to control the degree of expansion of the feed pellet and achieve a certain degree of pellet porosity. This is important for feed manufacturers to achieve the optimum buoyancy or sinking speed of the pellets and the associated porosity of the feed pellets to absorb oil or other liquids to meet the fish's nutritional requirements and optimize farming costs. The role of starch varies according to the species, fanning conditions, feed production equipment and other factors. In feedfor herbivorous and omnivorous fish, starch serves the purpose of binder, cheap energy source, and "filler" of the formula and expansion vehicle. Feed formulation programs tend to select the cheapest locally available starchy raw material for inclusion in a diet. Native starch is hardly digestible for fish but the aforementioned species groups have the ability to digest gelatinized starch fairly well due to sufficient amylase production in their relatively long digestive tract. Starch is, however, unable to contribute sufficient energy to meet the energy requirement in the diets for carnivorous species such as salmon. In salmon feed we lack "space" in the formula to cover all nutritional requirements, which leads to high cost of the feed formula.