Transition cow immune function and interaction with metabolic diseases.

Nearly all dairy cows experience some degree of immune suppression during the 2 to 3 weeks before and after calving. Typically, this is in the area of a 25 to 40% decline in both neutrophil function (innate immunity) and lymphocyte function (acquired immunity). Metabolic diseases, such as milk fever and ketosis, exacerbate immune suppression at this time; often resulting in closer to 60 to 80% loss of immune function. Several other so called metabolic disorders, such as retained placenta and metritis, may actually be manifestations of a poorly functioning immune system. Maintaining feed intake in the days before and after calving appears to be critical to early lactation immune competence. Preventing milk fever and ketosis can help prevent major loss of immune function and therefore reduce incidence of diseases, such as retained placenta, that occur secondary to a poorly functioning immune system. The immune system of the periparturient cow is also sensitive to inadequate dietary vitamin E, selenium, and trace minerals, such as zinc and copper.