α-Tocopherol levels in different organs of Atlantic salmon (Salmo salar L.)—Effect of smoltification, dietary levels of n-3 polyunsaturated fatty acids and vitamin E

Abstract

Atlantic salmon ( Salmo salar ) juveniles were fed a basal diet coated with 16% sardine or capelin oil (68 or 42 g n-3 PUFA per kg dry diet, respectively), each supplemented or not with 300 mg dl -α-tocopheryl acetate per kg. The unsupplemented diets contained 28 ± 4 and 31 ± 9 mg/kg α-tocopherol, respectively. There was a 5–7-fold increase in whole body α-tocopherol concentration in response to vitamin E supplementation, but the relative distribution of α-tocopherol between organs was similar in all groups. There was only a weak effect of dietary n-3 PUFA on the tissue levels of α-tocopherol. The ratio of α-tocopherol to PUFA in the fish tissues is probably critical in protection against lipid oxidation, and may modulate the vitamin E requirement. During smoltification, the whole body α-tocopherol concentration was unchanged or slightly increasing. All groups showed a 40–50% reduction of α-tocopherol concentration in the kidney and adipose tissue, possibly linked to changes in osmoregulation and mobilization of vitamin E. The body level of α-tocopherol seems to be higher in fish than in mammals. A species-specific tissue “distribution key” for α-tocopherol appears to be present in several fish and mammal species.