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Hypervitaminosis A in Rainbow Trout (Salmo gairdneri): Toxicity Signs and Maximum Tolerable Level¹

Department of Nutrition, University of Guelph, Guelph, Ontario, Canada N1G 2W1

Duplicate groups of juvenile trout were reared on practical trout diets supplemented with geometrically increasing levels of vitamin A (as retinyl palmitate) from 4,000 to approximately 8,104,000 IU/kg diet for 16 weeks at 15.2 ± 0.5°. The major signs of hypervitaminosis A in rainbow trout were growth depression, increased mortalities, abnormal and necrotic anal, caudal, pectoral and pelvic fins, and paleyellow, fragile livers. The maximum tolerable level of vitamin A in rainbow trout is approximately 904,000 IU/kg diet, whereas levels above 2,704,000 IU/kg diet are toxic. Hypervitaminosis A in trout also resulted in the occurrence of some spinal deformities; however, there was no apparent effect of excess vitamin A on ascorbic acid metabolism. Liver iron levels declined with increasing levels of dietary and liver vitamin A, indicating an effect of vitamin A on liver iron metabolism in trout. No effect of increasing dietary vitamin A was apparent in the mineral content of the kidney, skin-scales and vertebrae.

KEY WORDS: • trout • hypervitaminosis A • maximum tolerable level vitamin A • necrotic fins

¹ This work was financed by grants from the Natural Science and Engineering Research Council, the Ontario Ministry of Agriculture and Food, and the Ontario Ministry of Natural Resources.

Manuscript received 22 November 1982.