RELATIONSHIPS BETWEEN LEUKOCYTE COUNTS IN BULK MILK AND APPARENT QUARTER INFECTIONS IN DAIRY HERDS

Abstract

Bulk tank milk samples and quarter samples from 15,982 cows were collected from 285 herds enrolled in the New York State Mastitis Control Program. Culture and strip-plate examination findings from quarter samples were correlated with bulk milk cell counts. A correlation of 0.50 was found between percent quarters yielding mastitis pathogens and bulk milk cell counts. A correlation of 0.51 was found between percent quarters producing abnormal secretions and bulk milk cell counts. These relationships indicated the bulk milk cell count was not a reliable measure of herd infection or prevalence of abnormal secretion. The most prominent trend in a relationship between pathogens and increased bulk milk cell count was found for Streptococcus agalactiae and a lesser relationship between staphylococci and increased bulk milk cell count. Herds classified as having low bulk milk cell counts produced an average of 1,759 lb. of milk more than herds with high bulk milk cell counts. Only three milking and management practices were found to be associated with bulk milk cell counts.