Effect of dietary linolenic and linoleic acids upon growth and lipid metabolism of rainbow trout (Salmo gairdneri).

Nine diets, each containing different levels of linoleic acid (18:2 omega 6) and linolenic (18:3 omega 3) were fed to duplicate groups of rainbow trout for 14 weeks. The growth rate, feed efficiency, accumulated mortality, and fatty acid composition of neutral fat and phospholipids of these groups of fish were determined. The growth was slow in the groups of fish receiving diets containing (A) low concentration of 18:3 omega 3and (B) high concentration (5%) of 18:2 omega 6. The accumulated mortality was high in these groups of fish. The diet containing 1% of 18:3 omega 3 alone supported rapid fish growth with low mortality . The feed efficiency of this diet was also high. The metabolism of 18:2 omega 6 and 18:3 omega 3 in fish and their conversion to more unsaturated fatty acids typical of fish lipids was investigated.