Herd-level economic analysis of the impact of paratuberculosis on dairy herds

Objective-To perform a herd-level analysis of economic losses associated wi th paratuberculosis in dairy herds. Design-Cross-sectional study. Sample Population-A multistage stratified random sample of 121 dairy herds in Michigan. Procedure-A 2-part questionnaire was used to gather data on management prac tices, herd productivity, labor use, and expenditures. Blood samples were c ollected from a random sample of cows greater than or equal to 2 years old in each herd and tested for antibodies to Mycobacterium paratuberculosis. A herd was considered negative for paratuberculosis if results for all cows tested were negative, Multivariable linear regression was used to evaluate the data. Results-A 10% increase in proportion of cows positive for paratuberculosis was associated with a 33.4 kg (73.5 lb) decrease in mean weight of culled c ows. Mortality rate among herds positive for paratuberculosis was 3% higher than rate among herds negative for paratuberculosis. Herds positive for pa ratuberculosis did not have a significantly higher annual number of hours o f labor per cow than did herds negative for paratuberculosis, Clinical Implications-For a herd of average size and cull rate, the reducti on in mean weight of culled cows attributable to paratuberculosis represent ed a loss of approximately $1,150 annually for each 10% increase in herd pr evalence of paratuberculosis. The increased mortality rate attributable to paratuberculosis represented a loss of between $1,607 and $4,400 on the bas is of lost slaughter value and cost of replacement heifers.