Arteriosclerosis in Atlantic salmon. Effects of dietary cholesterol and maturation.

Coronary arteriosclerosis was examined in cultured Atlantic salmon (Salmo salar L.) maintained on normal and cholesterol-enriched diets in both freshwater and saltwater during the period when they normally mature (June to December). The incidence of lesions was high (48% or greater) in all experimental subgroups (assigned according to diet, salinity, sex, and maturation status). The primary factor in the development of arteriosclerotic lesions was not established, but the high frequency of lesions in immature fish suggests that it was not maturation. However, maturation was associated with a significant increase in the incidence of lesions and was, therefore, an important secondary factor in the etiology of the disease. Furthermore, diet had a secondary influence on the development of lesions since the cholesterol supplement was also associated with an increase in the incidence of lesions. The cholesterol supplement significantly increased the total plasma cholesterol level in all subgroups; the low density lipoprotein fraction (total cholesterol minus the high density lipoprotein fraction) was also elevated in seven of eight paired subgroups. Plasma free fatty acids and triglycerides were unaffected by the cholesterol supplement. The elevated total cholesterol and low density lipoprotein levels resulting from the cholesterol-enriched diet and the associated increase in the incidence of lesions was most prominent in mature males and females held in freshwater. Salinity had no demonstrable effect on lesion incidence, but the severity of lesions tended to be greater in freshwater fish.