EFFECT OF DIETARY VITAMIN-E SUPPLEMENTATION ON THE INTEGRITY OF SKELETAL-MUSCLE IN EXERCISED HORSES

The effect of vitamin E intake on indicators of muscle integrity was s tudied in exercised horses. Nineteen horses were blocked by sex and th en assigned to one of three diets: no supplemental vitamin E (BASAL), BASAL plus 80 IU of supplemental vitamin E/kg DM (80), or BASAL plus 3 00 IU of supplemental vitamin E/kg DM (300). The BASAL diet contained less than 44 IU of vitamin E/kg DM, but it was adequate in all other n utrients. During the 90-d treatment period, horses were exercised 5 d/ wk; in addition, serum and middle gluteal muscle alpha-tocopherol conc entrations were measured at 0, 30, and 90 d. All horses performed a re peated submaximal exercise test (RSET) at the end of the 90-d period. The following were measured before and after the RSET: alpha-tocophero l, thiobarbituric acid reactive substances (TBARS), conjugated diene ( CD) concentrations of the middle gluteal muscle, and serum creatine ki nase (CK) and aspartate aminotransferase (AST) activities. Serum a-toc opherol concentrations of horses receiving the BASAL and 80 diets decr eased (P <.05 and P <.06, respectively) during the 90-d treatment peri od but did not change in horses receiving the 300 diet. Serum and musc le alpha-tocopherol concentrations were higher (P <.05) at 30 and 90 d in horses receiving the 300 diet than in horses receiving the BASAL a nd so diets. Serum CK and AST activities increased (P <.05) following RSET but were not affected by dietary vitamin E level. Muscle alpha-to copherol level did not affect muscle CD or TBARS.