Studies Into Determination of Urinary Ph in Dairy Cows. Aspects of the Method and Suitability of the Ph Intra Partum for the Prospective Prediction of Calcium and Phosphate Concentrations in the Plasma Postpartum

Abstract

Objective: The aim was to investigate if refrigeration, storage and time of day influence the results of urinary pH determination in dairy cows. Additionally it should be examined whether the urinary pH intra partum can provide information on the current calcium and phosphate concentrations in blood and on the second day post partum. Material and methods: Experiment 1: Catheter urine was collected from 10 lactating cows and divided into three fractions stored at different temperatures (room temperature; 8 degrees C; -20 degrees C). The pH of all fractions was measured directly after collection and two, six, 12 and 24 hours later. Experiment 2: Catheter urine was collected from 13 lactating cows at 8:00, 12:00 and 16:00 hour, in three cows also at 20:00, 24:00 and 4:00 hour and urinary pH was determined immediately. Experiment 3: In 12 cows with dystocia during the obstetric examination as well as two days later urinary pH plasma concentrations of ionized calcium and inorganic phosphate were measured. Results: Experiment 1: Temperature and duration of storage significantly influenced urinary pH. There was a significant difference between the measured values immediately after urine collection and the later times (p < 0.000). Experiment 2: The time of day showed a significant influence on urinary pH. Values at 24:00 hour significantly differed from those at 8:00 (p = 0.001), 12:00 (p = 0.004) and 16:00 hour (p = 0.005). Experiment 3: Determination of urinary pH intra partum does not allow any conclusions with regard to current calcium and phosphate concentrations in plasma and with these parameters two days post partum. Clinical relevance: All together the median differences of the urinary pH - stored at various temperatures and different periods of time or collected at different times of day - were small, but differed statistically significant in some cases.