Mastitis continues to be a problem for dairy producers across the globe. The disease can manifest itself in a clinical and subclinical form. Clinical mastitis causes economic loss due to treatment costs, lost quarters, potential animal deaths and mostimportantly, discarded milk. Subclinical mastitis on the other hand, silently reduces milk production and quality until detected with a somatic cell count. Management strategies can have a large impact in the prevention of mastitis. However, there is agrowing pool of evidence that nutrition is linked to mastitis in the dairy cow. Factors linked to mastitis in the mature dairy cow often are associated with mastitis in the first lactation cow also, and in many studies both age groups were included. There may also be risk factors unique to the heifer due to differences in feeding management during the rearing or pre-calving portion of the heifer programme. At the onset of lactation, heifers may suffer the effects of a depressed immune system in specificsituations. Negative energy balance and elevated serum beta-hydroxybutyrate have been implicated in reducing leukocyte functionality; thus increasing the risk of diseases like mastitis. Several trace minerals and vitamins have a direct effect on the function of the immune system and therefore could have a direct effect on the ability of a cow to combat mastitis. The dairy cow's requirements for vitamins and minerals are affected by a variety of factors such as age, pregnancy, and production level or for the heifer, rate of growth (NRC, 2001). It has been accepted that for some vitamins and minerals, the amount required by the animal for optimal immune function is greater than the amount required for growth and reproduction. By the time clinical signsof deficiency are observed, growth, immunity, and fertility likely have already been compromised (NRC, 2001).
展开▼
