Preliminary Evaluation of the Fossomatic Somatic Cell Counter for Analysis of Individual Cow Samples in a Central Testing Laboratory1

Abstract

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.