Interactions of Dietary α-Tocopherol, Oxidized Menhaden Oil and Ethoxyquin on Channel Catfish (Ictalurus punctatus)

Abstract

A 3 × 3 × 2 factorial feeding study with channel catfish (Ictalurus punctatus) included the following dietary treatments: 0, 25, and 100 mg/kg dl-α-tocopherol; 0, 10, and 100 g/kg oxidized menhaden oil; and 0 and 125 mg/kg ethoxyquin. Fish fed diets containing oxidized menhaden oil without supplemental α-tocopherol or ethoxyquin exhibited poor growth, food conversion, and survival rates; high incidence of three distinct gross syndromes—exudative diathesis, muscular dystrophy, and depigmentation; fatty livers; anemia; and pronounced histological changes in muscle fibers, kidney, and pancreatic tissue. Although these conditions were improved by the addition of either α-tocopherol or ethoxyquin, analysis of variance of data revealed differentiation in effects. Tocopherol had a very strong main effect on all variables; yet, ethoxyquin did not have a significant effect (P > 0.05) on hematocrit levels and incidences of muscular dystrophy. Growth reduction, hematological changes, and the occurrence of muscular dystrophy and fatty livers were not observed in fish fed diets without oxidized menhaden oil, α-tocopherol, or ethoxyquin. However, high incidences of exudative diathesis, depigmentation, and mortality were present in this dietary treatment. Data from this study suggest that 25 mg/kg α-tocopherol and 125 mg/kg ethoxyquin, or 100 mg/kg α-tocopherol should provide adequate protection in most practical catfish diets.