Effect of Oxidized Fish Oil, DL-α-Tocopheryl Acetate and Ethoxyquin Supplementation on the Vitamin E Nutrition of Rainbow Trout (Salmo gairdneri) Fed Practical Diets

Publisher Website
Google Scholar
Abstract
A factorial experiment was conducted using two degrees of oxidation of the 7.5% supplemental fish oil (peroxide values of 5 and 120 meq/kg oil), two levels of supplemental dl-α-tocopheryl acetate (0 and 33 mg/kg diet) and two levels of ethoxyquin (0 and 125 mg/kg diet) supplementation. Dietary thiobarbituric acid number, weight percentage of polyunsaturated fatty acids and omega-three fatty acids in the total fatty acids were significantly (P < 0.05) different between diets with fresh and highly oxidized oil. Dietary RRR-α-tocopherol was significantly (P < 0.05) reduced by the addition of highly oxidized oil after 24 weeks storage of the feed while supplemental dl-α-tocopheryl acetate level was not changed. Fish fed the various diets showed no differences in growth, feed:gain ratio, carcass composition or plasma glutathione peroxidase activity. The mortality, percent red cells hemolyzed by hydrogen peroxide, plasma and liver RRR-α-tocopherol concentrations were significantly (P < 0.05) affected by the addition of highly oxidized oil or dl-α-tocopheryl acetate but not by ethoxyquin except that mortality was reduced by supplementary ethoxyquin. The results of this study suggested that no vitamin E or ethoxyquin supplementation was needed to prevent a deficiency of vitamin E in rainbow trout fed a practical diet containing 7.5% of a good quality herring oil for 24 weeks.