Nutritional effects of autoxidized fats in animal diets

Abstract

1. Turkey poults were fed from day-old to 6 weeks on a practical-type diet containing 10 % white fish meal (supplying 0.7 % lipid) and other constituents, mainly cereals (supplying 3.3 % lipid), together with either 1.5 % of anchovy oil that had been allowed to autoxidize under various conditions or 1.5 % of fresh beef fat.2. For group I the whole diet with anchovy oil was stored in air at 15° for 3 months before feeding. Its lipid oxidized only slowly, with no appreciable rise in peroxide value and little destruction of its polyunsaturated fatty acids. For groups 2 and 3 the anchovy oil was mixed with the white fish meal, and the mixture was stored for 3 months, by which time most of its polyunsaturated fatty acids had been destroyed by autoxidation and the pv of the extractable lipid, after reaching a peak of 260 μmoles/g, had fallen again to 110. At this point the anchovy oil-fish meal premixture was further mixed with the basal diet and used, either immediately (group 2) or after 3 months' further storage (group 3). 3. The turkeys in all three groups receiving ‘fish oil’ remained healthy and grew well, with only slightly apparent (and not significantly) lower weight gains than those on the control diet. There was no significant treatment effect on liver weight, serum aspartate amino-transferase or serum alanine aminotransferase activity. All the birds stored vitamin A in their livers, though the diets had provided not more than adequate supplies of this vitamin, but the reserves accumulated were significantly lower when the diets contained oxidized fat. On roasting, the turkeys of group 1 had a definite and objectionable fishy flavour, whereas those of groups 2 and 3 were as palatable as the controls on the beef fat diet.