[Persistent udder edema as a herd problem: a literature review].

The data presented in literature suggest that disturbances of volume regulation do not have a role in the pathogenesis of persistent udder oedema. Instead, they favour local mammary problems. The presence of both mast cells and oedema, especially in subcutaneous tissue, focuses attention on the role of mast cells in the pathogenesis of persistent udder oedema via increased endothelial permeability due to histamine release. The dissociation constants (Kd) for the high-affinity glucocorticoid receptor of normal and oedematous udders are not significantly different, and nor are there differences between the total quantity of dexamethasone bound (Bmax) and mast cell density in normal and oedematous udders. It has been shown that, in cattle, the concentration of histamine is higher in milk than in plasma. In addition, the urine histamine concentration is affected by the diet. Treatments to reduce udder oedema include combined salt and water restriction, supplementation with potassium or vitamin E (alpha-tocopheryl acetate), sodium restriction, and administration of hydrochlorothiazide intramuscularly, chlorothiazide orally, or sodium-acetazolamide orally and/or parenterally (i.v./i.m.). A low cation-anion balance in a diet containing 1.6% calcium also seems to reduce mammary oedema formation.