Aerobic cellular metabolism requires oxygen for the efficient production of energy and consequently produces reactive
oxygen species (ROS) including oxygen ions, free radicals and lipid hydroperoxides. The levels of cellular ROS
are maintained within a narrow physiological range to optimize cell performance and prevent cellular damage
by a network of antioxidant defense mechanisms. Increased oxygen metabolism during the periparturient
period, however, augments the rate of ROS production and the subsequent depletion of important antioxidant
defenses