Influence of sodium chloride and potassium bicarbonate on udder edema and selected blood parameters

Forty-four first lactation heifers were fed NaCl (23 and 136 g/d) or KHCO3 (0 and 272 g/d) beginning 42 d prepartum and continuing to 10 d postpartum to study the influence of these salts on udder edema and selected blood parameters. Addition of NaCl or KHCO3 singly to the diet significantly increased the severity of udder edema, but the addition of both salts did not increase edema. Blood samples were collected from the jugular vein at 42 d prepartum and at 1, 3, and 10 d postpartum. Hematocrit and pH were measured on whole blood and osmolarity on serum samples. Concentrations of protein, Ca, Na, K, and Cl in serum were also determined. Serum total proteins were reduced and serum osmolarity was increased in the cows fed NaCl. Blood pH was elevated in the group receiving KHCO3. Serum K was higher in groups receiving supplemental KHCO3. No differences across dietary treatments were observed in the other parameters. Although addition of NaCl or KHCO3 to the diet increased the severity of udder edema, the exact mechanism causing edema could not be determined.