The associations between culling due to clinical Johne's disease or the detection of Mycobacterium avium subsp. paratuberculosis fecal shedding and the diagnosis of clinical or subclinical diseases in two dairy herds in Minnesota, USA.

Our objectives were to identify associations between clinical or subclinical diseases and subsequent culling because of clinical Johne's disease (JD) or the detection of fecal shedding of Mycobacterium paratuberculosis (Map) after 305 days in milk (DIM). A total of 1297 cows from two Minnesota dairies were enrolled in the study. From study cows, fecal samples were obtained prior to calving (close-up period) and after at least 305 DIM or at the time of leaving the herd (sold/dead). Between 3 and 21 DIM, blood samples were obtained for serum betahydroxybutyrate (BHB) and serum total-protein testing. Body-condition score (BCS) was evaluated during the close-up period, between 3 and 21 DIM, and at the end of lactation. The diagnosis time (DIM) of clinical disease events (culling because of JD clinical signs, ketosis, lameness, mastitis, displacement abomasum, injury, metritis, milk fever, pneumonia, and retained placenta) was recorded. Sixty-six cows were culled because of JD clinical signs (CCDJ) with average DIM of 209. CCDJ was associated with event of pneumonia (n=131) (OR=3.0, 95% CI=1.0-6.0) and level of fecal shedding (light: OR=13.0, 95% CI=5.3-30.0; moderate: OR=34.0, 95% CI=13.0-89.0; heavy: OR=66.0, 95% CI=26.0-171.0). Detection of fecal shedding at the end of the lactation (n=79) was associated only with event of pneumonia (OR=2.0, 95% CI=1.0-4.0).