A Preliminary Evaluanon of a Fish Diet Based on Roasted Soybeans and Fresh Fish

Two experimental fish diets, one consisting of50% roasted soybeans and 50% fresh fish, and another consisting of 30% soybeans, 20% corn meal, and 50% fresh fish, both with vitamin and mineral supplements, were compared to Oregon pellets in a 6 week feeding trial using yearling channel catfish (lctalurus punctatus). The experimental diets were ground, blended and pelletized by passing the ingredients through a food chopper four times. Both mixtures proved highly attractive to the fish. Fish fed either experimental diet grew as well as fish fed the Orgon pellets. The experimental diets are suggested for use in parts of the world where commercially prepared fish feeds are not available. The diets also present the possibility of using non-commercial fishes as feed for more valuable fishes. It was observed that the fish exhibited fighting when the vitamin mix was omitted. A variety of pelleted feeds for fish are now available in the United States. Included are both complete diets for raceway and cage feeding, and less complete diets that are used for feeding fish in open pond culture, where some natural food is available. These feeds are available in various sizes of dry pellets of either a floating or sinking type. In addition to these feeds, manufactured by several different companies, there is a preparation known as the Oregon pellet (Hublou, 1963; Crawford and Law, 1972). The Oregon pellet is a moist feed which requires refrigeration. It has proven highly successful in feeding trout and salmon. All of these feeds are satisfactory when they are properly used, but prepared fish feeds are not available worldwide. Further, there may be a potential for incorporating locally availablen on-commercial, non-game fishes into fish feeds. There is also a possibility of using fish viscera or scraps in locally processed feeds. The basic approach in preparing the diets suggested here is the same as that used in preparing the Oregon pellet, to the extent that the moisture from the fresh fish is incorporated into the pellet. It differs, however, in that the formula is much simpler and the facilities required to prepare it are less sophisticated. The suggestion for formulation of this pellet came from the Fish Feeds and Nutrition Workshop held September 26-28,1972, in Rapid City, South Dakota. It was suggested at this workshop that soybeans roasted at 218 C for 15 minutes, supplemented with fish meal, would approach a nutritionally complete and palatable diet for fish. We modified this suggestion by combining 50% (by weight) fresh whole ground fish and 50% roasted soybeans. In a second formulation we used 50% ground fish, 30% roasted soybeans, and 20% corn meal. Both formulations were fortified with a salt mixture and a vitamin mix (Tables 1 and 2).

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