Culling associated with Neospora caninum infection in dairy cows.

OBJECTIVES: To estimate the extent to which cows infected with Neospora caninum were culled, compared with noninfected cows, and to identify differences in reasons for culling between infected and noninfected cows. ANIMALS: 442 Holstein cows on a commercial dairy with 36% seroprevalence for N caninum. PROCEDURE: Culling of cows was done after first calving without knowledge of N caninum serologic status.
RESULTS: Risk of a seropositive cow dying was not different from that of a seronegative cow (P = 0.50). Seropositive cows were culled 6.3 months earlier than seronegative cows, and had a 1.6 times greater risk of being culled, compared with seronegative cows (P = 0.004), after adjusting for culling risk associated with abortion. For cows culled for low milk production, culling risk for a seropositive cow was twice that for a seronegative cow (P = 0.007).
CONCLUSIONS: The economic impact of N caninum infection in dairy cattle can be expected to extend beyond that for abortion alone. Costs of the disease also may include premature culling and diminished milk production. CLINICAL RELEVANCE: Plans to control N caninum infection on dairies should include consideration that benefits may include reduction in premature culling and increase in milk production.