Preliminary Evaluation of the Fossomatic Somatic Cell Counter for Analysis of Individual Cow Samples in a Central Testing Laboratory .

This study evaluated the feasibility of using the Fossomatic somatic cell counter in the Dairy Herd Improvement Association (DHIA). DHIA utilizes preserved milk samples which have usually been stored for 1-5 days. Milk samples were stored for various periods, up to 7 days, and were preserved with (a) dichromate at 5 C, (b) dichromate at ambient temperatures, or (c) without dichromate at 5 C. These samples were evaluated with the Fossomatic and compared to direct microscopic cell counts (DMC) of these same milks when fresh. The best storage scheme was dichromate preservation at 5 C. The correlation between Fossomatic (FOM) at 7 days and DMC was .96. The regression equation was FOM = 20 + 1.11 (DMC). Analysis of variance of treatments 1 and 2 was significantly different (P < .01) with treatment 1 (dichromate at 5 C) having lower mean counts and a high correlation with DMC. Results were not sufficiently different, however, to appreciably change the evaluation of an individual cow's mastitis status. Treatment 3 (unpreserved milk) gave lower correlation coefficients than treatment 1 or 2 and at times, samples were uncountable. Comparison of the somatic cell count with bacterial isolation showed that 68% of 929 mammary quarters had <500,000 cells/ml and no bacterial infection. Agreement between California Mastitis Test (CMT) and Fossomatic scores decreased with increasing cell numbers/ml to a low of 16% agreement for CMT 3. The Fossomatic flouro-optical quantitative technique for somatic cells affords a low sample cost, high volume, accurate system adaptable for central laboratory use.