Use of a conductivity meter for the detection of subclinical mastitis

The conductivity of milk from 164 cows in four herds was measured. There were significant differences between the normal and the mastitic quarters in each of the four herds. However, there was a marked difference in conductivity levels between the herds, the mean conductivity of the normal quarters in one herd being higher than that of the mastitic quarters in another herd. In a trial using a hand-held mastitis detector on 123 cows from three herds, 91 per cent of the 106 mastitic quarters were detected. However, 33 per cent of the 315 normal quarters also gave a positive reading.