MILLIKIN: NUTRIENT REQUIREMENTS OF FISHES 



eluded the following physiological and morpho- 

 logical changes: hemorrhage around the base of 

 the dorsal fin, loss of skin mucosa, and "slough- 

 ing off of scales and fins (Aoe and Masuda 1967). 

 Quantitative inositol requirements are avail- 

 able only for common carp and red sea bream. 

 Common carp require 4 g inositol/kg dry diet for 

 maximal weight gain, feed conversion, and pre- 

 vention of skin lesions (Aoe and Masuda 1967). 

 Red sea bream require between 550 and 900 mg 

 inositol/kg dry diet in direct proportion to die- 

 tary glucose concentrations of 10 to 40% (Yone 

 1975). Currently, quantitative inositol require- 

 ments for salmonids are based upon dietary con- 

 centrations (250 to 400 mg/kg dry diet) that were 

 included in the control diets used to determine 

 qualitative vitamin requirements of chinook 

 salmon (Halver 1957). 



Vitamin A 



Vitamin A has been shown to be an essential 

 dietary constituent for channel catfish (Dupree 

 1966), rainbow trout (Kitamura et al. 1967b), 

 common carp (Aoe et al. 1968), goldfish (Jones et 

 al. 1971), and brook trout (Poston et al. 1977). 

 General physiological functions of vitamin A in 

 fish include a role in maintaining normal growth 

 rate, pigmentation, and vision. Long-term feed- 

 ing studies have consistently yielded various eye 

 malformations (e.g., popeye, cataracts, hermor- 

 rhage) in fish fed vitamin A-deficient diets. Rain- 

 bow trout fed no supplemental vitamin A in a 

 semipurified diet developed corneal pitting and 

 homogeneous clouding, thickening of the corneal 

 epithelium, and degeneration of the retina (Pos- 

 ton et al. 1977). However, growth during the 22- 

 wk period was similar regardless of dietary vita- 

 min A content (0% vs. 10,000 International Units 

 (IU) vitamin A/kg dry diet). Brook trout of a 

 smaller initial weight (0.15 g) than the rainbow 

 trout fingerlings (5.9 g) grew significantly faster 

 over a 20-wk period when fed 10,000 IU vitamin 

 A/kg dry diet compared with 0% vitamin A (Pos- 

 ton et al. 1977). Pronounced eyeball protrusions 

 and dermal depigmentation occurred in brook 

 trout fed vitamin A-deficient diets. Histopatho- 

 logical examinations of eyes of salmonids have 

 shown that lens damage does not occur in vita- 

 min A-deficient fish (Poston et al. 1977). Vitamin 

 A deficiency symptoms in channel catfish include 

 depigmentation, opaque and protruding eyes, 

 atrophy, and death (Dupree 1970). Vitamin A- 

 deficient goldfish developed exophthalmos, loss 



of scales, anorexia, and eventual mortality (Jones 

 etal. 1971). 



Conversion efficiency of /3-carotene to vitamin 

 A has been examined indirectly for channel cat- 

 fish and brook trout. Dupree (1966) indicated 

 that 12 mg /?-carotene/kg dry diet (equal to 20,000 

 IU of vitamin A/kg dry diet) were insufficient to 

 prevent popeye in channel catfish fed vitamin A- 

 deficient diets, whereas 450 IU of vitamin A/kg 

 dry diet were sufficient to prevent occurrence of 

 popeye in channel catfish fed diets devoid of /3- 

 carotene. These results suggested an inefficient 

 conversion rate (if any) of /3-carotene to vitamin 

 A in channel catfish (Dupree 1966). In a separate 

 study, channel catfish fingerlings (mean initial 

 weight = 2.25 g) fed 1,000 IU vitamin A acetate 

 had optimal weight gain and no occurrence of 

 popeye or other vitamin A deficiency symptoms 

 (Dupree 1970). Poston etal. (1977) demonstrated 

 indirectly that brook trout can convert dietary 

 /3-carotene into vitamin A with conversion effi- 

 ciency being greater at 12.4°C than at 9°C. Indi- 

 viduals fed 6 mg /3-carotene/kg dry diet (10,000 

 IU vitamin A activity/kg for many terrestrial 

 animals) without supplemental vitamin A did 

 not develop depigmentation or pronounced eye- 

 ball protrusion. However, brook trout fed 10,000 

 IU vitamin A palmitate/kg dry diet without sup- 

 plemental /3-carotene grew significantly better 

 than fish fed 6 mg /3-carotene/kg dry diet. Addi- 

 tionally, brook trout fed 0.6 mg /3-carotene/kg 

 dry diet (1,000 IU vitamin A activity) during the 

 same experimental period developed pronounced 

 eyeball protrusion at either 9° or 12.4°C. 



Vitamin D 



Qualitative requirements for cholecalciferol 

 have been determined for channel catfish and 

 rainbow trout. Lovell and Li (1978) demonstrated 

 the essentiality of dietary cholecalciferol for 

 channel catfish fingerlings via greater weight 

 gain and bone mineralization (total body ash, 

 phosphorus, and calcium) in individuals fed 500 

 IU cholecalciferol/kg dry diet compared with 0% 

 dietary cholecalciferol. Hypervitaminosis was 

 not detected since dietary cholecalciferol concen- 

 trations as high as 1,000,000 IU/kg dry diet did 

 not suppress body weight gain nor body fixation 

 of calcium and phosphorus. Barnett et al. (1979a) 

 established the essentiality of cholecalciferol for 

 rainbow trout fingerlings using two dietary con- 

 centrations (0% vitamin D 3 compared with 1,000 

 IU/kg dry diet). These investigators found that 



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