VARIATION OF LIPID AND TOCOPHEROL COMPOSITION IN 3 STRAINS OF CHANNEL CATFISH (ICTALURUS-PUNCTATUS)

Three strains of channel catfish (Ictalurus punctatus), which were designated as 'AQUA', 'LSU' and 'MSU', were examined for their lipid and tocopherol composition to delineate if genetic strains exhibited the potential to vary in their susceptibility to lipid oxidation. Since age, diet and environmental conditions were similar for all strains, growth and compositional differences were ascribed to genetic factors. Significant differences were noted between strains in their muscle tissue for triacylglycerol (TG) levels, fatty acid composition. and tocopherol levels. The largest quantity of TG was found in the LSU strain whereas the smallest quantity was found in the AQUA strain. Levels of polyunsaturated fatty acids (PUFA) in the TG and total lipid (TL) fraction were highest in the AQUA strain and lowest in the MSU strain. Similarly, a peroxidizability index, which took into account the differences in susceptibility of unsaturated fatty acids to oxidize, was highest in AQUA and lowest in MSU for the TG and TL fractions. The peroxidizability index for the phospholipid fraction did not vary between strains. Adopting a relative antioxidant effectiveness value of 0.31 for gamma-tocopherol, the LSU, MSU and AQUA catfish strains were calculated to contain 37.72, 22.79 and 42.49 nmol of alpha-tocopherol equivalents, respectively. The MSU catfish strain exhibited the highest ratio (nmol PUFA/nmol alpha-tocopherol equivalents) suggesting that its tissue would be the least stable to oxidation.