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Miscellaneous
+ In the absence of cystine Carbohydrates: Carbohydrate requirement of carp species is highly variable ranging from 10–45%. Common carp utilizes 25% carbohydrates effectively as energy source (Takeuchi, Watanabe and Ogino, 1979; Sen et al., 1978), while for mrigal fingerlings it is 28% in synthetic diets (Singh, Sinha and Kumar, (unpubl.). Although higher levels of carbohydrate may be utilized by carps, diets containing over 40% dextrin results in retarded growth and lowered feed efficiency due to lower digestibility. The most likely symptom of over supply of carbohydrates in diet is excessive deposition of fat in the liver and carcass. However, the protein requirements of carps can be brought down to some extent by raising the level of dietary carbohydrates. Lipids: The polyunsaturated fatty acids (PUFA) is considered to be the most important class of lipids as far as lipids are concerned. Carps can derive their lipid requirement from natural feed available in the pond since these compounds are readily available in planktonic and other biotic communities. Lipids are also considered to be the most important sparing compounds. By adding 5% of soyabean oil the optimum protein requirement of young mirror carp can be brought down to 33% from 38%. The addition increases the dietary metabolized energy from 2.8 to 3.1 Kcal/g. Vitamins: Studies on vitamin requirements of fish are very limited. The values of quantitative requirements of vitamins in common carp and the symptoms of their major deficiencies are presented in Table 15.
N = No dietary requirement demonstrated under
various environmental condition. Minerals and trace elements: Like higher vertebrates, carps also have dietary requirements of minerals such as calcium, iron, magnesium and phosphorus and trace elements such as cobalt, iodine, zinc, copper, manganese, sulpher, fluorine, molybdenum, etc. For common carp the minimum requirement of phosphorus in the diet is 0.6–0.7% and that of calcium is about 0.028%. 1% dicalcium-phosphate is recommended in the feed for adult fish in polyculture system in ponds. Trace elements are growth stimulants and are required in traces. Sen and Chatterjee (1976, 1979) reported that cobalt chloride and manganese at the rate of 0.01 mg/day/fish gives higher rates of survival and growth of spawn, fry and fingerlings of Indian major carps. Rohu requires about 0.014% dry diet of iron. In general, carps appear to be less sensitive to mineral deficient diets than other fish possibly due to meeting their dietary mineral requirements from natural sources under pond culture condition. Common feedstuffs: A large number of feed stuffs are presently being used as supplementary feed for carps in undrainable pond culture systems. Some of them are widely available and extensively used. These may be broadly classified into two groups: the feeds of plant origin and the feedstuffs of animal origin. Cakes of oil seeds such as groundnut, mustard, linseed, coconut, etc., are a most useful and widely used feedstuff of plant origin with high fat and protein contents. Brans of rice, wheat and other grains are equally popular and used in combination with oil cakes. Such meal as soya waste after oil extraction is excellent feed for carps. Broken cereals such as rice, wheat, maize, etc., are good but expensive feed materials. Leafy feeds are suitable for grass carp. Tender leaves of various aquatic and terrestrial plants (cassava, maioc, colocasia, banana, sweet potatoes, maize, etc.) and green animal fodder such as berseem, napier, paranapier, elephant grass, etc., are also used. Miscellaneous items such as kitchen wastes, household scraps, residues of bakery, beer brewing or rice-wine industry wastes can be profitably used as fish feed. Dried fish meal (fish flour) is the most common and cheapest source of animal protein and widely used in livestock and fish feeds. Slaughterhouse offals, prawn head meal, bone meal, silkworm pupae and items like snails, oligochaete worms, etc., are also widely used depending on their availability and price. Nutritive values of some commonly used feedstuffs are presented in Table 16. Digestibility and absorption greatly vary with the quality of the feedstuffs and also from fish to fish. The values of total digestible nutrients in common feedstuffs are given in Table 17.
DM - Dry matter; Usually the crude protein level of the supplementary feed is fixed at about 5 to 10% below the dietry protein requirement of the fish to be fed. Vitamins, minerals and trace elements are added as required.
Based upon the nutrient specifications, a number of test diets for carp fry, fingerling and brood fish are under extensive trials to determine which would be the preferred formulations in terms of efficiency and cost. The conventional rice-bran and oil cake mixture lacks animal protein, minerals and vitamins and rapidly separates into its component ingredients during the feeding process. Considerable improvement is possible if this conventional rice-bran and oil cake mixture is simply fortified with 15–25% fish meal, 0.1% mineral mixture, 0.1% vitamin mixture and pelletized. Although mineral and vitamin mixtures are commercially available as common additive of animal feed, fish meal at a reasonable price may not be easily available in rural areas. |
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