Growth and hepatic antioxidant enzyme activity of juvenile Arctic charr (Salvelinus alpinus) fed on diets supplemented with ethoxyquin, rosemary (Rosmarinus officinalis), or bladder wrack (Fucus vesiculosus)

The efficacy of the natural antioxidants rosemary (RM) and bladder wrack (BW), a seaweed, were compared to that of the synthetic ethoxyquin (EQ) in stabilizing lipid oxidation. The three antioxidants (RM, BW, and EQ) were added to 200 g samples of herring oil in triplicates, at five different concentrations (i.e., 100, 200, 300, 400, and 500 ppm EQ equivalent). Two months later, the levels of lipid oxidation in the samples were determined by assaying free fatty acids (FFA), peroxide value (POV), and anisidine value (AnV). The effects of RM, BW, or EQ on the growth and hepatic antioxidant enzyme activity of Arctic charr (stocked at mean body mass ± SD = 2.41 ± 0.11 g and farmed for 67 days) were studied in quadruplicate groups of 60 fish per tank. Catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) activities were studied in fish fed RM, BW, or EQ at 100, 300, and 500 ppm EQ equivalents. A control diet with 0 ppm was also included in the trial. To an extent, both RM and BW stabilized lipid oxidation in herring oils, but RM was more effective. At elevated concentrations, the performance of RM is similar to that of EQ. Growth was significantly affected by antioxidant type and concentration, being fastest in the group fed either no antioxidant or RM diets and poorest in diets containing either EQ or BW. The average body mass of the fish group fed antioxidant-free diet was 23% higher (P < 0.0001) than in the groups fed diets treated with EQ and BW. The activities of CAT, GPx, and SOD increased with dietary inclusion of RM as opposed to BW and EQ. The results suggest that RM could be used to replace EQ in stabilizing lipid oxidation. Additionally, RM does not suppress growth as EQ does.