The pathological effects of dietary rapeseed oil (RSO) in rats have been investigated. Rats given 60 cal% RSO for 2 weeks showed fatty accumulation in the heart, skeletal muscles and adrenals. In another experiment, 60 cal% RSO was given for 2, 4, 8 and 16 weeks. The fatty infiltration of the skeletal muscles, adrenals and hearts regressed with the increase in the dietary period, but in the heart, necrotic foci, aggregations of mono-nuclear cells, and an increase in the connective tissue elements ensued. From a 2-week dose-response study, 20 cal% RSO was established as the minimum level causing the fatty accumulation. Similar lesions were produced by feeding RSO or glyceryl trierucate on an isocaloric erucic acid basis. Erucic acid thus appears to be the constituent in RSO responsible for its pathological effects. It was shown that the fatty infiltration of the heart and skeletal muscles occurs after 1 day of RSO feeding and becomes most severe after 3–6 days. The myocardial fatty infiltration in rats given RSO for 3 days markedly decreased after the feeding of this oil had been discontinued. It is suggested that the fatty infiltration of the heart and skeletal muscles by RSO reflects a slower oxidation of fatty acids in these organs.

The pathological effects of dietary rapeseed oil (10–60 cal%) in Pekin ducklings have been investigated. The oil produced growth retardation, mortality, increase in hematocrit and reticulocyte count, severe hydropericardium, hypertrophy of the heart, cirrhotic changes of the liver, lipidosis of the spleen and fatty accumulation associated with cell infiltration in the heart and skeletal muscles. 30 cal% rapeseed oil appeared to be the minimum level causing these changes. It is demonstrated that the pathogenicity of rapeseed oil is due to its erucic acid content.

Diets containing rapeseed oil (RSO) or glyceryl trierucate (GTE), each supplying 25 cal% erucic acid, were compared for their effect on the cardiac morphology in male Wistar rats after 1 week, and on growth, pathology and heart and kidney weights after 24 weeks. Sunflowerseed oil (SSO) and a rapeseed oil supplying ca. 4 cal% erucic acid (LER) served as control fats. The RSO and GTE diets produced similar effects. After 1 week, cardiac lipidosis was observed in both dietary groups; after 24 weeks, lipidosis had decreased remarkably and cellular scars were the main pathological feature. The severity of the lipidosis and of the fibrotic changes was similar in both groups. Growth and the relative weights of the heart and kidneys were significantly different – mutually as well as in comparison with the control rats fed SSO. It was concluded that erucic acid is the main pathogenic fatty acid in RSO, but other long-chain fatty acids may also play a minor role. The animals fed LER showed normal growth and organ weights compared with the SSO group. Slight cardiac lipidosis was observed after 1 week. After 24 weeks, some animals showed cardiac cellular scars varying in intensity from slight to moderate. In a second experiment, Sprague-Dawley rats were fed 0, 5, 10, 15, 20, 25 or 30 cal% RSO in diets made isocaloric in fat by addition of SSO. The rats were killed after 3 and 6 days and 32 weeks. All rats fed RSO for 3 and 6 days showed a dose-related lipidosis of the heart. The groups fed RSO for 32 weeks showed myocardial changes which were already manifest in a few animals on the 5 cal% RSO diet. Incidence and severity of these changes increased according as the RSO content of the diet was increased.

Diets containing rapeseed oil (RSO), or RSO supplemented with olive oil (OLO, rich in oleic acid), safflower oil (SAF, rich in linoleic acid) or tallow (TAL, comparatively rich in palmitic acid) were compared for their nutritional and pathogenic characteristics in ducklings. Unsupplemented RSO and the mixtures RSO-OLO and RSO-SAF caused growth retardation, mortality, lipidosis of the spleen cirrhotic changes of the liver and vacuolar changes of the heart and the skeletal muscles. The mixture RSO-TAL caused no mortality and a better growth. It also improved the liver and spleen morphology and decreased the hydropericardium incidence but did not markedly alter the incidence or severity of the vacuolar changes of the myocardium and skeletal muscles. In another experiment the effects of supplementing diets isocaloric in fats and in erucic acid with increasing levels of hardened palm oil (HPO) or glyceryl trilaurate (GTL) were investigated. Increasing levels of HPO increased growth and decreased the incidence and severity of liver cirrhosis, hydropericardium and splenic lipidosis. The vacuolar changes of the skeletal muscles were not improved, but those of the myocardium became severer. The supplement of GTL augmented all lesions, decreased growth and increased mortality. It is concluded that the nutritional and pathological properties of RSO in ducklings are determined both by the excess of erucic acid and the deficit of palmitic acid in the oil.

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