Financial Effect of Mycobacterium paratuberculosis in a Dairy Herd

Influence on Mastitis, Milk Production and Cull Rate in Clinically Normal Cows

Abstract

A 210 cow Holstein dairy herd contained approximately 45 cows that were Mycobacterium paratuberculosis-positive on the basis of fecal culture during a one year study. Farm management participated in the NY State Paratuberculosis Eradication Program. Paratuberculosis-positive cows were grouped separately from negative cows, but they were otherwise managed identically. During the year of the study, 180 paratuberculosis-negative cows and 113 clinically normal paratuberculosis-positive cows 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 paratuberculosis-positive cows. Dairy Herd Improvement Association (DHIA) records were kept for milk somatic cell count Linear Scores (LS), mature equivalent (ME) milk production new mastitis infections and chronic mastitis infections. Beginning in second lactation, and increasing with advancing parity, paratubculosis-positive cows had lower ME milk production than did negative herdmates. However, rates of new and chronic mastitis infections, as measured by DHIA LS were significantly (P < 0.05, P = 0.05, respectively) lower in cows with nonclinical paratuberculosis. Infected cows were culled from the herd at a faster rate than were negative herdmates. Overall, paratuberculosis was associated with economic benefit due to lower rates of mastitis in positive cows, but a net financial loss resulted because of reduced milk production and increased culling rates.