Effects of parenteral selenium and vitamin E on performance, health and humoral immune response of steers new to the feedlot environment.

Five trials with steers new to the feedlot environment were conducted to determine the effects of one or two i.m. injections of selenium (Se) and(or) vitamin E (Vit E) on performance, health status and serum antibody response to Pasteurella haemolytica vaccination. In all trials, performance and average number of days sick per steer were not affected (P greater than .05) by single injection of Se and(or) Vit E. In Trial 1, 26 steers (avg initial wt 267 kg) were treated with 1) no Se or Vit E or 2) 25 mg Se (as Na2SeO3) plus 340 IU Vit E (as [d]-alpha-tocopheryl acetate). P. haemolytica serum immunoglobulin G (IgG) titers on d 7 and 14 were greater (P less than .05) for steers receiving 25 mg Se plus 340 IU Vit E. In Trial 2, 141 steers (avg initial wt 204 kg) were treated with 1) no Se or Vit E, 2) 25 mg Se, 3) 340 IU Vit E or 4) 25 mg Se plus 340 IU Vit E. Serum IgG titers were greater (P less than .05) only for Treatment 4 on d 6. Trial 3 was conducted using 107 steers and the same treatments as in Trial 2. By d 14, titers for treatment 4 were greater (P less than .05) than those for Treatments 1 or 3, but not greater than those for Treatment 2. In Trial 4, serum IgG titers were unaffected (P greater than .05) when 48 steers (avg initial wt 248 kg) were treated with 1) no Se or Vit E, 2) 25 mg Se plus 340 IU Vit E 14 d prior to shipping or 3) 25 mg Se plus 340 IU Vit E 14 d prior to shipping, plus repeat injection on day of arrival at the feedlot. In Trial 5, 107 steers were treated with 1) no Se or Vit E, 2) 25 mg Se plus 340 IU Vit E or 3) 50 mg Se plus 680 IU Vit E. Serum IgG titers increased linearly (P less than .01) due to treatment on d 7, 13 and 20 and a quadratic response (P less than .05) was observed on d 27. In these trials, serum antibody response to P. haemolytica vaccination was enhanced with the combination of Se and Vit E; however, performance and health status were not affected.