Effects of selenium supplementation on serum cortisol in repeatedly handled cattle

this study evaluated the relationship between se supplementation and serum cortisol in repeatedly handled cattle. sixty nellore calves were randomly distributed into four experimental groups, which were fed a mineral-protein mixture added with se to achieve individual daily supplementation of 0 (gc), 3.6 (g3.6), 5.4 (g5.4) and 6.4 (g6.4) mg se. stressful handling procedures and blood sampling were performed on days 0, 15, 30, 60, 90 and 120. serum cortisol increased until day 90 and decreased on day 120, irrespective of se supplementation. this finding shows that cattle reached a stress state but adapted. cortisol and se levels were not markedly correlated. serum se increased over the course of the experiment in the supplemented groups. however, because serum se decreased in gc, it may have mobilized to form the selenoproteins needed to remove metabolic wastes from handling-related oxidative stress.