Changes in electrical conductivity and somatic cell count between milk fractions from quarters subclinically infected with particular mastitis pathogens

Cows with subclinical intramammary infections were identified by milk bacteriology. The mastitis pathogens included Staphylococcus aureus (n=9), Streptococcus uberis (n=10) and coagulase-negative staphylococci (n=10). Samples of first fore milk, main flow milk and strippings milk fractions were collected from each quarter and laboratory measurements were made of electrical conductivity, milk fat concentration and somatic cell count. Conductivity measurements were corrected for milk fat concentration and within-cow inter-quarter conductivity ratios calculated. Repeatability estimates of all measurements between days were calculated. In the case of infected quarters, all conductivity values decreased markedly (P