Use of the Fossomatic Somatic Cell Counts in a Mastitis Control Program1

Abstract

The Fossomatic determination of somatic cells present in individual cow milk samples was instituted in the Virginia Dairy Herd Improvement testing program in June, 1976. During the first 6 months the average count was 449,060 cells/ml for 113,735 observations. The average percentage of cows according to ranges in cell counts was: under 150,000, 47.9%; 150–400,000, 25.8%; 400–800,000, 12.5%; 800–1,500,000, 7.2%; and over 1,500,000, 6.6%. The percentage of cows with less than 150,000 cells/ml was reduced for September, 1976. On a herd basis, 66% averaged less than 500,000 cells/ml, 30% between 500 to 1,000,000, and 4% exceeded 1,000,000. The percentage of herds with less than 500,000 cells/ml decreased from June to September, 1976 but increased in October. Quarters infected with primary pathogens were estimated by Westgarth's equation to be 10.4% resulting in a calculated 5% reduction in total herd milk production. Procedures are described which would assist dairymen in the interpretation of somatic cell counts.