[Methodical influence on selected parameters of the acid-base equilibrium in urine samples from dairy cows]

Estimation of net acid base excretion (NABE) in urine samples of dairy cows has often been reported in the veterinary literature. NABE has been proved to be meaningful in estimation of disturbances in the cows acid base equilibrium. In order to examine the meaningfulness of this method different factors with possible influences on NABE were tested. Estimation of simple and fractionated NABE lead to comparable results. Whereas implementation of fractionated NABE is linked with higher expense, simple NABE gives information at lower expense. After four days storing of urine samples in the refrigerator the concentration of NH4+ increased significantly. In view of using this parameter to estimate the acid metabolic situation this may lead to false information. Therefore urine samples should be examined at least within three days after collecting and refrigerated storing. Sediment distribution significantly influenced all urine parameters. Above all the shift of the values into direction of the reference limit may result in the assessment of individual cows as risk group. Homogeneous mixing of the urine samples must be carried out before NSBA-determination. A higher air portion in the sample containers lead to a significant increase of the pH in urine samples. To prevent influences of the air on urine samples, sample containers should be filled completely.