Bovine postparturient hemoglobinemia: hypophosphatemia and metabolic disorder in red blood cells.

Mechanism of hemolysis in postparturient hemoglobinemia was studied in 7 cows. Cows 1 to 5 had a history of hemoglobinemia at a previous calving, but hemoglobinemia did not occur during the present parturition. Cow 6, a daughter of cow 4, and cow 7 from another farm, developed postparturient hemoglobinemia and had hemoglobinuria on days 20 and 21 and 10 to 17 after calving, respectively. During the time cows 6 and 7 had hemoglobinuria, both cows had a marked decrease in serum inorganic phosphorus, RBC adenosine 5'-triphosphate (ATP), and reduced glutathione, and a significant (P less than 0.01) increase in methemoglobin concentration. In cow 6, these changes were observed before the onset of hemoglobinuria, indicating metabolic disorder of RBC. After phosphate administration IV, serum inorganic phosphorus was corrected, and RBC ATP was increased above base-line value. During the time cows 6 and 7 had hemoglobinuria, PCV, hemoglobin concentration, and RBC count decreased progressively and reached nadir values, 40% to 50% of baseline values, on day 22 in cow 6 and on day 19 in cow 7. Cows 6 and 7 were anemic, even after serum inorganic phosphorus and RBC ATP values returned to acceptable values. Glycolytic disorder and depletion of ATP, resulting from phosphorus deficiency, appeared to be a primary and essential step leading to hemolysis in postparturient hemoglobinemia in cows 6 and 7.