Biochemical and histological effects of feeding thermally oxidized rapeseed oil and lard to rats.

Four groups of weanling rats were fed semisynthetic diets containing 15 percent by weight of dietary fats for 28 days. Two groups received thermally oxidized low-erucic acid rapeseed oil (OLE) or lard (OLA) and the other two groups received the respective fresh fats (FLE, FLA) as controls. Average daily feed consumption and feed efficiency were not affected by either OLE or OLA, however final body weights were depressed by the OLA in the diet. The relative heart weights and heart total lipids were significantly increased in both the OLE and OLA groups. A majority of the animals in both the OLE and OLA groups exhibited various gross symptoms attributable to heated fat toxicity such as seborrhea, diarrhea and polyuria. Excessive hair loss was noted in all the animals fed the heated fats. Tissue fatty acid changes due to OLA were confined largely to the polar liver lipids, whereas OLE produced dramatic changes in both the neutral heart lipids as well as in the neutral and polar liver lipids. Histological evaluation of the hearts, livers and kidneys indicated that OLA was very injurious to the kidneys, whereas OLE caused greater damage to both the hearts and livers.