Selenium Associated Oxidative Stress in the Mammary Gland of Periparturient Dairy Cows

SELENIUM ASSOCIATED OXIDATIVE STRESS IN THE MAMMARY GLAND OF PERIPARTURIENT DAIRY COWS By Stacey Lynn Aitken Dairy cows experience tremendous stressors during the periparturient period leaving them susceptible to numerous metabolic and infectious diseases. Mastitis continues to be the number one disease afflicting dairy cows during this time period. An inability to compensate for fetal demands and the onset of lactation alters a dairy cow’s nutritional status significantly around the time of calving. Antioxidant deficiencies as a consequence of low selenium levels during the periparturient period are associated with increased susceptibility to mastitis. The benefit of selenium to mammary gland health may be attributable to its incorporation into selenoproteins, which participate in immune regulation, partly due to their ability to control oxidative stress. Oxidative stress is the result of decreased antioxidant potential and increased reactive oxygen species production. Increased levels of reactive oxygen species contribute to inflammation by causing either direct cellular damage or altering signaling pathways in immune cells. The ability of selenoproteins to control oxidative stress, such as during the periparturient period, may reduce the incidence and severity of mastitis lessening economic burdens to the dairy industry. The goal of this thesis is to examine selenoprotein activity within the mammary gland of periparturient dairy cattle and determine if it may contribute to oxidative stress and proinflammatory gene expression during this time period.