Response of Young Channel Catfish to Diets Containing Purified Fatty Acids

Nine-gram channel catfish Ictalurus punctatus fed 10 weeks on diets containing ethyl esters of stearic, oleic, linoleic, and linolenic acids did not demonstrate a strong requirement for linolenic-family fatty acids. Growth was inhibited when diets contained 1% or 2% linolenic acid (by weight) but no oleic or linoleic acids. If channel catfish require dietary linolenic acid, it is at a concentration below 1%. The previous view that poor growth of channel catfish on diets supplemented with vegetable oils was due to high levels of linoleic acid appears to have been incorrect. Soybean oil, and other vegetable oils, contain several percent linolenic acid. Growth depression may occur when such oils are utilized at levels of 5 to 10% of the diet. Proximate analyses revealed that fish on all diets had similar body compositions of lipid, protein, and moisture. Among the fatty acids, dietary linoleic and linolenic acid were stored and fish became depleted in those acids when they were excluded from the diet. Most groups of fish showed histological evidence of myopathy and myocarditis; fish on the fat-free diet had the fewest abnormalities. Received October 19, 1982 Accepted June 15, 1983