Determination of the potassium balances in dairy cows and the examination of daily and lactation period-associated variations.

The objectives of this study were to evaluate a method of determining the i nternal and external potassium balances in dairy cows and to determine dail y and lactation period-associated variations of these balances. Ingested po tassium, milk potassium concentration (LK) and potassium urinary fractional clearance (FeK) defined the potassium external balance. Serum (SK) and red blood cell (CIEK) potassium concentrations defined the potassium internal balance. Whole blood, urine, and milk were collected at different times of the day from 19 cows, grouped in 5 lactation periods. Significant differenc es were observed for LK between lactation periods. Significant variations o ccurred during the day for CIEK, LK, and FeK. Thus, in order to monitor pot assium balances during a time period, samples should be collected at the sa me time each day. This method of determining both potassium balances simult aneously could be useful in the study of the bovine hypokalemia syndrome.