ABSTRACT
Diet additives have been defined as nonnutritive ingredients or nonnutritive components of ingredients that are included in diet formulations to influence physical or chemical properties of the diet or affect fish performance or quality of resulting products. This chapter discusses purified nutrient supplements such as amino acids, lipids/fatty acids, and minerals that may be added to diets to improve their nutritional value. Most plant feedstuffs contain lower concentrations of crude protein and relative amounts of indispensable amino acids compared to fish meals and other protein feedstuffs of marine origin. The chapter focuses on exogenous enzymes, prebiotics, and probiotics, as well as the feeding stimulants or palatability enhancers because such additives tend to have the greatest potential application in aquafeeds when feedstuffs of marine origin are replaced with plant feedstuffs. In recent years many exciting studies have shown the potential use of probiotics in aquaculture through diet manipulation to enhance growth, immunity, and resistance of aquatic animals to various diseases.
