Nutrition and mastitis.

Increasing evidence presents a relationship between nutrition and mammary resistance to infection. The role of nutrition in mammary resistance has been best defined for antioxidants. To optimize this interaction, rations should be balanced and formulated for lactational stage. Although supplementation of nutrients with antioxidant function may enhance immune resistance against infections, therapeutic roles for nutritional management of clinical mastitis, as yet, are not well documented. The need to monitor herd antioxidant status as part of a mastitis control program is critical because (1) antioxidant supplementation improves mammary resistance to infectious disease during the most critical period for enhanced resistance, the dry and early postpartum periods; and (2) dry cows and heifers often are on a marginal plane of Se supplementation, particularly during periods of risk for mastitis and reproductive disorders. In areas where forages contain less than 0.1 ppm Se (dry matter) because of low soil availability, herds should be tested for Se status and, if found to be below optimum levels, increased dietary supplementation or sustained-release Se boluses should be considered. Similarly, vitamins A (or beta-carotene) and E status should be monitored in herds, especially confined herds receiving a large proportion of ensiled forages.