Effect of Supplemental Vitamin E Form on Serum α-Tocopherol Levels and Blood Oxidative Stress Parameters in Response to a Novel Exercise Challenge

Vitamin E has an integral role in preventing cellular damage associated with free radicals. It is essential in the equine diet and found in natural as well as synthetic sources (α-tocopheryl acetate). Because of structural differences, bioavailability of forms may vary. The objective of this study was to assess serum α-tocopherol and oxidative parameters in response to vitamin E form. Sixteen mature horses were confined to stalls for a 2-week washout period, and then randomly assigned to one of four treatment groups for a 2-week feeding trial, each receiving 4,000 IU/d ([1] synthetic all-rac-α-tocopheryl acetate powder; [2] natural RRR-α-tocopheryl acetate powder; [3] micellized RRR-α-tocopherol liquid; and [4] micellized RRR-α-tocopherol powder). Serum α-tocopherol was assessed prefeeding on days 1, 7, and 14 and 4 hours postfeeding on days 1 and 14. Serum α-tocopherol prefeeding levels were higher on days 7 and 14 across treatments as compared with day 1 (P < .05). Horses on liquid micellized RRR-α-tocopherol showed the greatest response to supplementation on day 1 (P < .05). Across exercise time points, horses receiving micellized RRR-α-tocopherol exhibited higher serum α-tocopherol levels as compared with horses receiving acetate-bound treatments (P < .05). When treatments were pooled, horses receiving micellized RRR-α-tocopherol maintained total whole blood glutathione levels after an exercise challenge, whereas horses receiving acetate bound forms showed a decrease postexercise (P = .03). In addition, horses on synthetic α-tocopherol acetate showed the highest levels of plasma protein oxidation postexercise (P < .05). Results indicate that micellized RRR-α-tocopherol may be beneficial when horses are challenged with a novel exercise test.