The automatic Milk Cell Counter (MCC) and semi-automatic electronic cell counter (ESCC) of Coulter Electronics were compared with each other and with the direct microscopic cell count (DMSCC) on raw milk samples with various cell counts. The average DMSCC count on 241 samples of milk with Wisconsin Mastitis Test (WMT) results of 22 mm and higher was 55,000 cells/ml above the average MCC count when calibrated to a 4.4-μm minimum particle diameter. This difference is statistically significant at the 1% level. On 24 different raw milk samples of widely varying somatic cell count analyzed in replicate six times per sample, the standard deviations for replicate samples were 34,300, 34,900 and 136,000 for the MCC, ESCC and DMSCC, respectively. For these tests, the MCC had been calibrated to a 4.3-μm minimum particle diameter. The average difference between counts by the MCC and ESCC methods was only 6080/ml, but this was statistically significant at the 5% level. The average MCC count with the equipment set at 4.3-μm minimum particle diameter was 58,000 above the average DMSCC count.

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Author notes

1Paper No. 10,548, Scientific Journal Series, Minnesota Agricultural Experiment Station, St. Paul, MN 55108.

2Dairy Quality Control Institute.

3Department of Food Science and Nutrition.

4Department of Agricultural Engineering.