BOVINE MASTITIS PATHOGENS IN NEW-YORK AND PENNSYLVANIA - PREVALENCE AND EFFECTS ON SOMATIC-CELL COUNT AND MILK-PRODUCTION

Milk samples were collected from 108,312 dairy cows during 1601 farm v isits made between January 1991 and June 1995. The herd visits were ma de by personnel from the Central Laboratory of the Quality Milk Promot ion Services at Cornell University (Ithaca, NY) to farms located in ce ntral New York and northern Pennsylvania. Dairy Herd Improvement Assoc iation records were available for 32,978 cows in 327 herds. Intramamma ry infections, as defined by positive milk cultures, were present in 4 8.5% of all cows and in 36.3% of cows in herds enrolled in the Dairy H erd Improvement Association. Over 75% of the intramammary infections w ere caused by Streptococcus agalactiae, Streptococcus spp. other than Strep. agalactiae, Staphylococcus aureus, and coagulase-negative staph ylococci. Mean days in milk at the time of diagnosis, linear score of the somatic cell count, cost of milk loss per lactation, and milk prod uction effects were calculated for 24 etiologic agents of bovine masti tis.