Effects of dietary vitamin E and synthetic antioxidants on composition and storage quality of channel catfish, Ictalurus punctatus

Two experiments were conducted to investigate the effects of natural and synthetic antioxidants in the diet on body composition and storage quality of channel catfish. An initial 12-week feeding trial in aquaria evaluated semipurified casein/gelatin diets containing two levels of vitamin E (60 or 240 mg dl-α-tocopheryl acetate/kg) with (1) no synthetic antioxidant, (2) ethoxyquin (150 mg/kg), or (3) butylated hydroxytoluene (10 mg/kg) in a factorial arrangement. In a separate 10-week feeding trial, similar diets containing vitamin E at two levels (60 or 240 mg dl-α-tocopheryl acetate/kg) with (1) no synthetic antioxidant, (2) butylated hydroxyanisole (10 mg/kg), or (3) Endox TM (125 mg/ kg) were evaluated. None of the antioxidants tested significantly altered growth, feed efficiency or proximate composition of whole-body and fillet tissues. Fish fed diets with 240 mg dl-α-tocopheryl acetate/kg had significantly higher levels of α-tocopherol in fillet samples than did those fed 60 mg dl-α-tocopheryl acetate/kg diet, but synthetic antioxidants in the diet did not affect tissue levels of α-tocopherol. Oxidation of lipids in frozen channel catfish fillets was determined by 2-thiobarbituric acid (TBA) analysis before and after 6 months at − 18 °C. Oxidative stability of fillets from catfish fed all dietary treatments was not significantly reduced during the 6-month storage period. When oxidation of the fillets was forced by flushing the samples with oxygen, TBA values were significantly reduced in samples from fish fed the higher level of vitamin E; whereas none of the synthetic antioxidants reduced oxidation. These data indicate that increasing supplemental vitamin E in the diet from 60 to 240 mg dl-α-tocopheryl acetate/kg provides additional protection against lipid oxidation in fillet tissue.