DOSE-RESPONSE EFFECTS OF VITAMIN-E SUPPLEMENTATION ON GROWTH-PERFORMANCE AND MEAT CHARACTERISTICS IN BEEF AND DAIRY STEERS

This study examined dose-response effects of supplemental dietary dl-a lpha-tocopheryl acetate (VE) on growth performance, immune response, a nd carcass and meat sensory characteristics in two breeds of cattle. S eventy-five crossbred beef steers (361 +/- 22 kg) were blocked by weig ht, randomly assigned to one of five treatment groups, and fed a ratio n supplemented with 0, 250, 500, 1000 or 2000 IU VE steer(-1) d(-1). S ixty Holstein steers (366 +/- 22 kg)were similarly blocked and allocat ed (no 250 IU treatment). Four days post-slaughter the left sirloin su bprimal of each steer was removed and vacuum packaged. On day 13, smal l cores were cut from the gluteus medius (GM) and packaged with O-2-pe rmeable wrap; these were then displayed under 45-W natural white light for up to 10 d at 4 degrees C. Serum alpha-tocopherol increased (P < 0.0001) with increasing VE in both breeds, although more so (P < 0.000 1) in beef steers. The GM alpha-tocopherol levels increased linearly ( P < 0.0001) with increasing VE, but more so (P < 0.0002) in beef steer s. The levels of alpha-tocopherol in semimembranosus muscle, perirenal and subcutaneous fat, and liver also increased linearly (P < 0.0001) in both breeds. Growth performance of all steers and carcass character istics of beef steers were not affected (P > 0.10) by VE. Dairy steers receiving 1000 IU d(-1) had darker (P < 0.03) ribeyes. There were no effects (P > 0.10) of VE on sensory attributes of frozen streaks. Surf ace metmyoglobin formation was deterred by VE supplementation in meat from beef (linear, P < 0.016) but not dairy (P > 0.10) steers. Lipid o xidation was suppressed (linear, P < 0.0002) by VE but more so (P < 0. 0001) in beef than in dairy meat (72.9% vs. 40.0% suppression, respect ively, at 2000 IU d(-1)). Immune response increased (P < 0.074) at hig her levels of VE. In summary, VE supplementation improved immune respo nse and increased serum and muscle alpha-tocopherol levels, resulting in delayed metmyoglobin formation (beef) and lipid oxidation (beef and dairy) in a dose-dependent manner. Supplemental VE was more effective in meat from beef steers than in that from dairy steers.