Effects of dietary lipid level on liver and muscle lipid deposition in juvenile haddock, Melanogrammus aeglefinus L

The effects of dietary lipid levels on growth, feed utilization, hepatosomatic index (HSI), liver lipid deposition and tissue fatty acid composition in haddock were investigated. Triplicate tanks of juvenile haddock (6.9 g) were fed graded levels of herring oil to supply 14, 16, 19 and 22% lipid (DM, dry matter) in fish meal-based, isonitrogenous diets. Growth and feed conversion ratio of juvenile haddock was not significantly (P<0.05) affected by increasing the lipid content of the diet. A significant increase in HSI (9.8-12.1%), total liver lipid (63.2-69.0%) and whole body gross energy content (6.03-6.39 kcal/g DM) were observed in haddock fed 14 vs. 22% lipid. Although the HSI of these cultured haddock was high in comparison to wild gadoids, histological analyses of these haddock livers did not reveal any overt pathology. Muscle lipid levels (1.0%) did not increase significantly with dietary lipid. Liver fatty acid levels mirrored dietary fatty acid (FA) composition. The muscle consisted mainly of polar lipid (84.3+or-2.5% of total lipid) and a large proportion (52.6+or-0.8%) of polyunsaturated FA. A dietary lipid level of 14% DM or less is recommended for juvenile haddock..