Dietary vitamin E concentration and duration of feeding affect tissue α-tocopherol concentrations of channel catfish ( Ictalurus punctatus)

Abstract

Semipurified diets containing 30% crude protein from casein and gelatin were supplemented with three concentrations of dl- α-tocopheryl acetate (0, 240 or 1000 mg/kg) and fed to channel catfish (initial average weight = 36.4 g) for 6 weeks. Factorial analysis of variance indicated a significant ( P<0.001) effect of dietary vitamin E on α-tocopherol concentrations of plasma, liver and muscle; levels of α-tocopherol in these tissues were directly related to dietary vitamin E levels. Concentrations of α-tocopherol in plasma and liver reached approximate maxima by week 2; whereas, fillets of fish fed diets with 240 and 1000 mg dl- α-tocopheryl acetate/kg had progressively higher concentrations of α-tocopherol after 2, 4, and 6 weeks of feeding. Levels of α-tocopherol in fillet tissue that had previously been shown to improve oxidative stability were achieved after 6 weeks of feeding the diet containing 240 mg α-tocopherol/kg; similar levels were attained within 2 weeks of feeding the diet containing 1000 mg α-tocopherol/kg. This information may be used in developing diet and/or feeding regimes to improve the oxidative stability of channel catfish fillet tissue prior to harvest and processing.