Electrical conductivity in fraction-collected quarter milk samples with low somatic cell counts

Electrical conductivity and somatic cells were measured in fraction-collected quarter milk samples of 32 quarters (8 cows) at 3 morning and 3 evening milkings to compare the diagnostic capacity. The mean somatic cell count in the foremilk fraction (FOM) was 44,000 cells/ml. The intermilking intervals were 10 and 14 h. The first milk jets (FIM), the milking fractions of the last minute of milking (L-3, L-2, L-1) and the stripping fraction (SM) showed significantly increased cell count levels compared to the fractions of the first minute of milking (F-1, F-2, F-3). The highest cell count value was measured in the SM fraction (195,000 cells/ml). The electrical conductivity showed a plateau in the fraction FOM to L-3 and the values in the fraction L-2 to SM were significantly decreased compared to the values of the earlier fractions. The lowest conductivity values were found in SM. To evaluate the influence of the intermilking interval and the udder health status the quarters were split into 2 groups based on the threshold value of 50,000 cells/ml in the FOM fraction. Group 1 (G1) had a mean value of 18,000 cells/ml, group 2 (G2) a mean of 95,000 cells/ml. The first 4 milk fractions (FIM to L-3) had at evening milking after an interval of 10 h significantly increased cell counts but significantly decreased electrical conductivity values compared to the corresponding values at morning milking. The somatic cell count indicated a higher diagnostic capacity compared to the electrical conductivity due to significant differences between G1 and G2 in all milk fractions which were not identified for the electrical conductivity.