Fats and Oils
Fats and oils are used as energy sources, to provide essential fatty acids, and to coat the outside of pelleted feeds to reduce abrasiveness (resulting in less fines) and minimize dustiness. Fats from livestock and poultry processing (animal fats) are highly saturated, but are and poultry processing (animal fats) are hithly saturated, but are effective sources of energy for warm and coldwater fishes. Vegetable oils are generally higher priced than animal fats in the United States because of their value for human use, but are also good energy sources f or fish. Marine fish oils are used in feeds for trout, salmon, and cultured marine fish because they are a source of essential (n-3) fatty chain (over 20-carbon) n-3 fatty acids. Animal fats and vegetable oils and linseed oils, most are low in n-3 fatty acids. Catfish oil, which is recycled back into catfish feeds. Is similar to livestock and poultry fat in fatty acid composition. Fatty acid composition of fats and oils from various sources used in fish feeds is presented in Appendix A, Table A.4 (see page 253).
Fibrous Feedstuffs
Fish do not require fiber in the diet and, being monogastric animals, do not digest fibrous feeds well. It is unlikely that adding fiber to practical diets that contain 3% to 5% fiber will have any measurable benefit. In most cases, the concern is to avoid excessive levels of fiber in fish diets because high fiber levels reduce the binding quality of processed feeds, inhibit feed intake by fish, and increase fecal waste production.