[An outbreak of lipoid liver degeneration (LLD) in Atlantic salmon (Salmo salar) in a fish farm and attempts to cure the disease (author's transl)].

A description of a field experiment on the therapeutic effect of 4 different drugs against lipoid liver degeneration is given in a natural outbreak of the disease in a fish farm. The diagnosis was based on pathological and histopathological changes in the liver and characterized on the basis of the degree of ceroid deposited in the liver cells. The size and weight of the fish had no influence on the deposition, but it was shown that LLD caused a higher mortality in Atlantic salmon than in rainbow trout, showing a weekly mortality of 2.5 and 0.3%, respectively. In the field experiments therapeutic effect was obtained with 1) Vitamin E, mixed into the feed in amounts of 90 mg alpha-tocopherol + 450 mg ethoxyquin pr. kg wet feed. 2) A combination of alpha-tocopherol and selene mixed into the diet in amounts of 20 mg tocopheryli acetas and 0.4 mg natrii seleniis pr. kg wet feed. The cause of the disease is not verified, but it seemes that rancid material in the diet was the main etiological factor. Predisposing factors influencing the peroxydation of the feed under practical conditions in Norwegian fish farms have been discussed.