FINANCIAL EFFECTS OF MYCOBACTERIUM-PARATUBERCULOSIS ON MASTITIS, MILK-PRODUCTION, AND CULL RATE IN CLINICALLY NORMAL COWS

Approximately 45 Holstein cows that were Mycobacterium paratuberculosi s-positive on the basis of fecal culture were maintained at any one ti me in a 210-cow dairy herd. Farm management participated in the New Yo rk State Paratuberculosis Eradication Program. Paratuberculosis-positi ve cows were grouped separately from negative cows, but they were othe rwise managed identically. During a 1-year study, 180 paratuberculosis -negative cows and 113 clinically normal paratuberculosis-positive cow s were identified. From paratuberculosis-negative cows, 6, 100 quarter milk samples were aseptically collected for microbiologic culture of mastitis pathogens, and 3, 129 quarter samples were obtained from para tuberculosis-positive cows. Dairy Herd Improvement Association (DHIA) records were used to monitor milk somatic cell count linear scores (LS ), mature equivalent (ME) milk production, new mastitis infections, an d chronic mastitis infections. Overall, paratuberculosis was associate d with economic benefit due to lower rates of mastitis in positive cow s, but a net financial loss resulted because of reduced milk productio n and increased culling rates.