Effects of supplementation of dietary antioxidants and chelated trace minerals in periparturient dairy cows and subsequent response to intramammary bacterial challeng

Two experiments were conducted to investigate the effects of supplementation of synthetic dietary antioxidants and different sources of a blend of trace minerals on two distinct situations of immune dysfunction in dairy cows. In the first experiment, the effects of these supplements on health, metabolism, and production variables of periparturient dairy cows were examined. Supplementation over National Research Council requirements may not be beneficial to multiparous cows, although signs of antioxidant status and health improvement were seen when primiparous cows were supplemented. Treatments did not affect dry matter intake. Milk yield was not different over time between treatments in primiparous cows; however, the control group showed slightly increased milk production in multiparous cows. Animals fed organic trace minerals had lower incidence of displaced abomasum and metritis compared to animals fed inorganic forms, even with higher incidence of clinical ketosis. However plasma concentrations of glucose, non-esterified fatty acids, and beta-hydroxybutyrate were not affected by treatment. Animals fed organic trace minerals also had greater lymphocyte DNA damage than those fed inorganic trace minerals. Multiparous cows subjected to the combination of dietary antioxidants and organic trace minerals had increased rabies antibody titers in response to vaccination, suggesting an enhanced adaptive immune response. In the second experiment, we evaluated the response of supplemented early lactation dairy cows submitted to experimental Escherichia coli mastitis. Supplementation over National Research Council requirements may not be beneficial to primiparous cows, although production variables were improved when multiparous cows were supplemented with inorganic trace minerals. Dry matter intake and milk production were inversely related to somatic cells score. Milk quality was altered in the infected quarter and to a lesser extent, in control quarters. Feed efficiency declined after bacterial infusion as well as lymphocyte DNA damage. In conclusion, response of primiparous and multiparous animals varies among parities under different situations of stress. Interestingly, the effects of inorganic and organic trace minerals on animals are altered in these situations and the intensity of stress may affect the response.