Practical Feed Ingredients
Ingredients used in practical fish feeds can be classed as protein (amino acid) sources; energy sources; essential lipid sources; vitamin supplements; mineral supplements; and special ingredients to enhance growth, pigmentation, or sexual development in the fish, or physical properties, palatability, or preservation of the feed. Some feed ingredients in common use worldwide and factors influencing their use in fish feeds are discussed in the following. Nutrient composition of these and other feedstuffs is presented in Appendix A.
Fish Meal
Fish meal made from good quality whole fish that is properly processed is the highest quality protein source commonly available to fish feed manufacturers. It is a rich source of energy and minerals, is highly digestible, and is highly palatable for most fishes. Fish meal made from whole fish contains 60% to 80% protein which is 80% to 95% digestible to fishes. It is high in available lysine and methionine, the two amino acids most deficient in plant feedstuffs. Marine fish meal contains 1% to 2.5% n-3 fatty acids, which are essential in the diet of many fishes. Fish meal made from fish parts, such as waste from fish processing and canning plants, is lower in percentage and quality of protein. It is also high in ash and should be used prudently in fish diets to prevent mineral imbalances which could cause inavailability of certain minerals.
Fish meal appears to be beneficial in fish diets in ways other than helping to meet the fish’s minimum nutrient requirements. Research studies have shown that supplementation of either the lipid or the nonlipid fraction of fish meal to a nutritionally balanced channel catfish diet increased growth.
Because of its high cost, fish meal is generally used sparingly in commercial fish feeds, although some feeds, such as those fed to eels and pen-reared salmon, contain high levels of fish meal. Other animal protein sources, such as good quality blood meal, meat meal, or poultry byproduct meal, have been reported to replace some of the fish meal in experimental fish feeds.