MAMMARY IMMUNOLOGY AND MASTITIS SUSCEPTIBILITY DURING THE PERIPARTURIENT PERIOD: IMPACT OF OXIDATIVE STRESS

摘要

Dairy cows undergo substantial metabolic and physiological adaptations during the transition from pregnancy to lactation. Coordinated shifts in nutrient partitioning must occur in order to meet the increased demand for energy and other nutrients necessary for fetal growth and lactation (Drackley, 1999). The considerable increase in oxygen requirements during times of enhanced metabolic demands results in augmented production of reactive oxygen species (ROS). An imbalance between increased productionof ROS and the availability of antioxidant defenses needed to reduce ROS accumulation during the periparturient period may expose cows to increased oxidative stress. Early studies suggested a role of oxidative stress in the etiologies of dairy cattle disorders since supplementation with certain antioxidant micronutrients could ameliorate the severity of a variety of metabolic and infectious diseases (Miller et al., 1993). There are now several more recent studies to support the concept that oxidative stress is a significant underlying factor to dysfunctional host immune and inflammatory responses that can increase the susceptibility of dairy cattle to a variety of health disorders, particularly during the transition period (Bernabucci et al., 2005; Castillo et al., 2005; Sordillo, 2005; Sordillo and Aitken, 2008; Wilde, 2006). This paper will not only summarize how oxidative stress impacts immunity and mastitis susceptibility in periparturient dairy cattle, but also suggest how the protective effectsof certain antioxidants can be optimized.