MILLIKIN: NUTRIENT REQUIREMENTS OF FISHES 



reached a maximum when blood L-ascorbic acid 

 concentrations reached 7 Aig/ml (Murai et al. 

 1978). Rainbow trout which were considerably 

 younger (0.3 g) than channel catfish from the 

 previous study, required about 80 mg of dipotas- 

 sium ascorbic-2-sulfate (DAS)/kg dry diet over a 

 20-wk period to avoid ascorbic acid deficiency 

 symptoms in the majority of fishes, and 160 mg 

 DAS/kg dry diet to achieve normal growth (Hal- 

 ver et al. 1975). 



Choline 



Dietary essentiality of choline has been demon- 

 strated for rainbow trout (McLaren et al. 1947), 

 brook and brown trout (Phillips and Brockway 

 1957), lake trout (Phillips 1959b), chinook salm- 

 on (Halver 1957), coho salmon (Coates and Hal- 

 ver 1958), channel catfish (Dupree 1966), rainbow 

 trout (Kitamura et al. 1967a), common carp 

 (Ogino et al. 1970a), Japanese eel (Arai et al. 

 1972a), and red sea bream (Yone 1975). Choline 

 deficiency symptoms in fish include poor growth 

 and feed efficiency, anorexia, fatty livers, and 

 hemorrhagic areas in kidneys, liver, and intes- 

 tine. 



Quantitative choline requirements have been 

 estimated for common carp fingerlings and lake 

 trout fingerlings. Ketola (1976) examined rela- 

 tive growth rates of lake trout fed an unsupple- 

 mented diet (30 mg choline/kg dry diet) compared 

 with equimolar supplements of aminoethanol, 

 dimethylaminoethanol, methylaminoethanol, be- 

 taine-HCl, and choline (equivalent to 2,600 mg 

 choline/kg dry diet). Lake trout fed the unsupple- 

 mented diet and aminoethanol and betaine sup- 

 plements had reduced growth rates and high 

 liver fat content. It was concluded that since 

 betaine, a source of labile methyl groups, did not 

 affect growth or liver fat content, any metabolic 

 function of choline in regulation of liver fat in 

 lake trout is unrelated to transmethylation. In a 

 separate feeding study, a quantitative dietary 

 choline requirement of 1,000 mg/kg dry diet was 

 determined for lake trout fingerlings (Ketola 

 1976). Common carp require an estimated mini- 

 mal dietary choline-Cl concentration of 2,000 

 mg/kg dry diet based upon slightly reduced 

 growth and fatty livers in individuals fed cho- 

 line-deficient diets (Ogino et al. 1970a). The pos- 

 sible role of methionine as a methyl donor and its 

 relative efficiency in preventing fatty liver and 

 hemorrhagic degenerations of kidneys of choline- 

 deficient fish has not yet been investigated. 



Folic Acid and Cyanocobalamin 



Qualitative folic acid requirements have been 

 demonstrated for brook, brown, and rainbow 

 trout (Phillips and Brockway 1957), chinook 

 salmon (Halver 1957), coho salmon (Coates and 

 Halver 1958), channel catfish (Dupree 1966), 

 rainbow trout (McLaren etal. 1947; Kitamura et 

 al. 1967a), Japanese eel (Arai et al. 1972a), and 

 rohu, Labeo rohita (John and Mahajan 1979). 

 However, common carp fingerlings (mean initial 

 weight = 2.5 g) fed several folic acid concentra- 

 tions (0 to 15 mg/kg diet) over 16 wkdid not show 

 differential responses in growth, feed conversion, 

 folic acid liver content, and erythrocyte counts 

 (Aoe et al. 1967b). 



Folic acid deficiency symptoms in chinook 

 salmon include poor growth, anorexia, anemia, 

 lethargy, dark coloration, and megaloblastic 

 erythropoiesis (Halver 1957), while coho salmon 

 displayed poor growth and anorexia (Coates and 

 Halver 1958). Channel catfish fed folic acid-defi- 

 cient diets displayed lethargy, anorexia, and in- 

 creased mortality (Dupree 1966). Anemia in coho 

 salmon fed folic acid-deficient diets was macro- 

 cytic with poikilocytosis of erythrocytes and a 

 reduction in number of the erythrocytes (Smith 

 and Halver 1969). Clinical folic acid deficiency 

 symptoms in coho salmon in the same study in- 

 cluded reduced growth, pale gills, exophthalmia, 

 dark coloration, and distended abdomens with 

 ascites fluid. These authors suggested that blood 

 cell formation in fish is very sensitive to folic acid 

 deficiency because of the importance of folic acid 

 in incorporation of nucleotides into deoxyribo- 

 nucleic acid. Phillips (1963) detected anemia 

 (type was not reported) in brook trout fingerlings 

 fed folic acid-deficient diets after 9 wk. 



Qualitative cyanocobalamin requirements 

 have been demonstrated for chinook salmon 

 (Halver 1957) and channel catfish (Dupree 1966). 

 Halver (1957) reported growth retardation and 

 reduced hemoglobin concentrations and erythro- 

 cyte numbers in chinook salmon fed a cyanoco- 

 balamin-deficient diet for 16 wk. Channel catfish 

 fed cyanocobalamin-deficient diets displayed 

 growth retardation after 36 wk (Dupree 1966) or 

 lower hematocrits after 24 wk (Limsuwan and 

 Lovell 1981). Limsuwan and Lovell( 1981) demon- 

 strated that intestinal microorganisms synthe- 

 sized about 1.4 ng of cyanocobalamin/g body 

 weight per day. Lack of differences in growth, 

 hemoglobin concentration, and erythrocyte num- 

 bers in fish fed either 21.8 ng cyanocobalamin/g 



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