Effect of vitamin E supplementation on alpha-tocopherol and beta-carotene concentrations in tissues from pasture- and grain-fed cattle

The effects of dietary vitamin E supplementation of grain-fed cattle on lipid oxidation and meat colour have been extensively investigated, but little attention has been given to pasture-fed. cattle where meat is likely to contain naturally high amounts of alpha -tocopherol and carotenoids. In the work described, we evaluated the effects of pasture-feeding alone and with vitamin E supplementation on tissue levels of anti-oxidants and compared the findings with those obtained for grain-fed cattle with and without supplementation. Sorghum was the major component of the grained-based ration. alpha -Tocopherol concentrations in plasma, muscle and fat tissues of pasture-fed cattle were not affected by vitamin E supplementation (2500 IU/head/day for 132 days prior to slaughter) while those of grain-fed cattle increased significantly. The alpha -tocopherol concentrations in the supplemented grain-fed cattle were similar in muscle and liver to pasture-fed animals but were lower in their fat (P < 0.05). The major carotenoid present in all tissues studied from pasture-fed was beta -carotene and its contents in plasma., liver, fat and muscles were decreased (P < 0.05) by supplementation with vitamin E. Carotenoids were essentially absent in grain-fed cattle except for small amounts in liver. The implication of this study for the meat industry is that cattle grazed on good pasture can achieve concentrations of alpha -tocopherol in muscles and other tissues at least as high as those obtained by supra-nutritional supplementation of grain-fed cattle with vitamin E. However, alpha -tocopherol supplementation of pasture-fed cattle reduced tissue concentrations of beta -carotene, which would reduce carcase fat yellowness and make pasture-fed cattle more acceptable to some Asian markets. (C) 2001 Elsevier Science Ltd. All rights reserved.