The invention provides a milking system (20) for detecting disease in a mammal, comprising: teat cups (26, 27), each teat cup in fluid communication with a teat line (30-33), probes (100, 102, 104, 106) being in contact with milk in the system, the system further comprising means (50-53, 60) for supplying AC current to said probes at a frequency of greater than 60 megahertz, and means (70) for measuring a shift in phase angle between voltage and current signals while AC current is applied to said probe that results from the milk.
