Effect of dietary linolenic acid and docosahexaenoic acid on growth and fatty acid composition of rainbow trout (<i>Salmo gairdneri</i>)

Abstract

Abstract Methyl linolenate 18∶3ω3 and docosahexaenoate 22∶6ω3 were incorporated in semipurified diets at several levels and fed to trout previously maintained on a fat‐free diet. After 14 weeks, the weight gain and feed conversion of the fish on each diet were determined. The fatty acid composition of the lipid from each group of fish was analyzed by gas liquid chromatography. Both 18∶3ω3 and 22∶6ω3 fed at the 1% level supported maximum growth of the fish. The control group, which were fed no ω3 fatty acids, exhibited a shock syndrome, poor appetite and a very slow growth rate. Tissue fatty acid analysis revealed eicosatrienoic acid 20∶3ω9 accumulated in the phospholipid fraction of this group. The 20∶3ω9 level was lowered when either 18∶3ω3 or 22∶6ω3 was included in the diet. Analysis showed that the dietary 18∶3ω3 was rapidly converted by the fish into 22∶6ω3 with a high concentration in the phospholipid. However 22∶6ω3 fed to the fish remained unchanged and little or no retroconversion of this fatty acid was observed.