Various methods of estimating somatic cell levels in milk were compared with the direct microscopic somatic cell count (DMSCC). The electronic cell count (ECC) using centrifugation to separate cells from milk yielded correlation coefficients of 0.870 to 0.907 when compared to DMSCC. The Wisconsin mastitis test (WMT) yielded correlation coefficients of 0.714 to 0.753 when compared to the DMSCC. The diphenylamine filter-DNA method yielded correlation coefficients of 0.988 to 0.991 when compared to the DMSCC. The filter-DNA method was modified by using indole instead of diphenylamine to obtain color. This method reduced the time for color development from 16 hr to 10 min. The correlation coefficients were 0.987 to 0.990 using this method when compared to the DMSCC.

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Author notes

1Research supported by the College of Agricultural and Life Sciences and by PHS Research Grant UI00124 from the National Center for Urban and Industrial Health. Paper No. NS 715.