A PRACTICAL EVALUATION OF MILK CONDUCTIVITY MEASUREMENTS

SUMMARY The milk electrical conductivity of 31 cows milked with a Liberty automatic milking system was monitored for 15 weeks. An alert triggered when conductivity rose by 17.5% corresponded with a rise in cell count to more than 400,000 cells/ml. When a trigger equivalent to a cell count rise to more than 200,000 cells/ml was applied then the sensitivity for mastitis detection was 80% and the specificity was 63%. When milk samples were analysed for pathogenic bacteria then the rate of false positive triggers was 12%.