The biological activity of natural source tocopherols in chickens fed fresh or oxidized fat rich in linoleic acid

Three experiments were carried out with male broiler chickens reared from day- old to 6 weeks of age on semi-purified diets containing 10% fresh (Expt. 1 and 3) or oxidized (Expt. 2) re-esterified triglycerides with a fatty acid composition similar to that of soya bean oil containing increasing concentrations of either a mixture of d-alpha-, gamma-, delta-tocopherylacetate (d-tocopherols) of natural source or dl-alpha- tocopheryl acetate (dl-tocopherol). In Expt. 1 and 2 the mixture of d-tocopherols consisted of 35.7% d-alpha-, 45.3% d-gamma- and 19.0% d-delta-, while in Expt. 3 the distribution was 25.3% d-alpha-, 28.1% d-gamma- and 10.8% d-gamma- in 35.8% re-esterified triglycerides. The relative biopotency of d-alpha-: gamma-: delta-tocopherol was anticipated to be 100:25:1, whereas that of dl-alpha-tocopherol was 74% relative to d-alpha-tocopherol. The experiments demonstrate that the results obtained for the biological activity depend on the response parameters chosen. With respect to gain in weight, feed conversion, relative organ weight, packed cell volume (PCV), ELP (erythrocyte lipid peroxidation), plasma activities of glutamate-oxaloacetate-transaminase (GOT), creatine kinase (CK) and glutathione peroxidase (GSH-Px) and plasma Na+ concentration, the mixture of natural source tocopherols was identical to that of dl-alpha-tocopheryl acetate, although the concentration of alpha-tocopherol was only about one third of that of dl-alpha-tocopherol. Differences between natural source and synthetic tocopherols were expectedly observed with respect to plasma concentrations of alpha-, gamma-, delta-tocopherol. Differences between the two forms as to muscular dystrophy, in vitro haemolysis and potassium concentration in plasma were ambiguous. It is suggested that the function of d-alpha-, gamma-, delta-tocopherol in erythrocyte fragility and skeletal muscle structure should be compared to that of dl-alpha-tocopherol in future investigations.