Effect of shipping and chromium supplementation on performance, immune response, and disease resistance of steers.

Forty-eight Angus crossbred steers (263 +/- 2 kg initial BW) were blocked by weight and randomly assigned within weight group to treatment. Treatments consisted of control or .4 mg of supplemental Cr as Cr-nicotinic acid complex/kg of DM. Steers were fed diets containing 90% corn silage (DM basis) and 10% of a soybean meal-mineral-vitamin supplement. After 56 d on the dietary treatment, half of the steers in each treatment were transported 343 km and unloaded in an unfamiliar location. The next day, d 58, shipped steers were returned to the feedlot (50 km). On d 58 after shipped steers were returned to the feedlot, all steers were inoculated with infectious bovine rhinotracheitis virus (IBRV) intranasally. Average daily gain from d 0 to 80 was increased (P < .10) by supplemental Cr. There was a shipping x time interaction for serum cortisol concentrations. Shipping increased (P < .02) serum cortisol on d 58, but 7 d after transport there were no effects of shipping on serum cortisol. Transportation increased (P < .05) the ratio of neutrophils to lymphocytes. Supplemental Cr did not affect rectal temperature after the IBRV challenge or the antibody response to IBRV or porcine red blood cells. Immunoglobulin G antibody response to porcine red blood cells was decreased (P < .09) by shipping. Supplemental Cr as Cr-nicotinic acid improved ADG of growing steers, regardless of whether they had been stressed by shipping. Supplemental Cr did not affect any of the immune responses that were measured.