Burke, Nathaniel Caleb2014-03-142014-03-142007-07-26etd-08162007-174653http://hdl.handle.net/10919/34587Metabolic redox status may have important implications to cattle health and production. Antioxidants and biomarkers of oxidative stress were evaluated in cattle under three phases of management. Each phase stood alone as a treatment model, and managerial aspects during the phase were evaluated as potential moderators of redox balance. Yearling heifers were used to assess the impact of fescue toxicosis and heat stress on selected markers in study 1. Intravaginal temperatures, ADG, serum prolactin, plasma malondialdehyde, and whole blood Se, along with peripheral blood mononuclear cell glutathione peroxidase, glutathione reductase, and reduced:oxidized glutathione were determined during summer grazing. Results suggested that endophyte consumption does not promote oxidative stress in cattle. Heat stress may alter glutathione redox of white blood cells. In study 2, effects of gradual weaning strategies (anti-suckle nose clip and fenceline wean) and transport were evaluated in calves. Calf weights, Se and malondialdehyde in plasma, along with glutathione peroxidase and glutathione reductase in leukocytes were measured at -7, 0, 1, and 7 days surrounding weaning and transport. Little benefit of gradual weaning was detected, and oxidative stress may have been negligible. In study 3, the influences of grain- and forage-based diets were compared in finishing steers pre- and post-harvest. Total antioxidant capacity and malondialdehyde concentration of plasma, along with serum alpha-tocopherol, beta-carotene, and gamma-tocopherol were measured. Antioxidants and lipid oxidation were assessed in beef. Forages promoting plasma antioxidant capacity may protect cattle against oxidative stress. Antioxidants derived from forages inhibit lipid oxidation in pasture-finished beef.In Copyrightendophyteoxidative stressweaningantioxidantscattleforage-finished beefThesishttp://scholar.lib.vt.edu/theses/available/etd-08162007-174653/