Lipid peroxidation status as an index to evaluate the influence of dietary fats on vitamin E requirements of young pigs

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Abstract
The aims of the present study were to establish a suitable criterion for estimating the vitamin E requirement for young pigs, and to investigate the influence of dietary fats on the requirement of this nutrient. In Expt 1 weaned pigs were given a semi-purified diet supplemented with 0,20, or 100 mg DL- α-tocopheryl acetate/kg. Pigs in Expt 2 were fed on diets containing 10 g sunflower oil (SO) stripped of vitamin E/kg in diets 1 and 2, 100 g SO/kg in diets 3 and 4, and 100 g tallow/kg in diet 5. Diets 2, 4 and 5 were supplemented with DL-α-tocopheryl acetate at 20 mg/kg for 0·28 d and 50 mg/kg for 29–56 d of the experiment respectively. Results showed that vitamin E concentrations in plasma and tissues reflected dietary levels of vitamin E. No apparent clinical signs of vitamin 'E deficiency were observed, but pigs fed on diets without vitamin E supplementation showed a higher (P < 0·05) lipid peroxidation status as indicated by thiobarbituric acid-reactive substances in erythrocytes, and ethane and pentane levels in exhaled gases than those fed on supplemental diets. This indicated that the former was deficient in vitamin E. Data in Expt 1 suggested that supplementation with 20 mg DL-α-tocopheryl acetate/kg is adequate for young pigs when the diet contains 30 g lard/kg. However, results in Expt 2 showed that this level was inadequate when the diet contains 100 g SO/kg or its equivalent to 70 mg polyunsaturated fatty acids (PUFA)/g. Vitamin E and lipid peroxidation status of pigs were affected by both dietary vitamin E and dietary PUFA. This demonstrates that the requirement for vitamin E in young pigs increases as PUFA levels in the diet increase. The present study shows that lipid peroxidation response of pigs is a suitable index to evaluate vitamin E requirements.