Effect of Neospora caninum infection on milk production in first-lactation dairy cows

OBJECTIVE: To determine whether cows seropositive to Neospora caninum produced less milk during their first lactation than seronegative cows. DESIGN: Repeated-measures, prospective study. ANIMALS: 372 Holstein cows in their first lactation. PROCEDURE: Cows were tested repeatedly before and during their first lactation for antibodies to N caninum. One-way and repeated-measures ANOVA were used to determine whether mean daily milk weights and milk weights from Dairy Herd Improvement Association testing were less for seropositive cows than for seronegative cows. RESULTS: Weekly mean daily milk weights for the 118 seropositive cows were significantly less than those for the 254 seronegative cows, and milk production for seropositive cows (mean, 55.2 lb/cow/d) was 2.5 lb/cow/d less than that for seronegative cows (mean, 57.7 lb/cow/d). Analysis of results from Dairy Herd Improvement Association testing revealed that production of seropositive cows was less for milk (3.1 lb/cow/d), fat-corrected milk (3.6 lb/cow/d), and fat (0.14 lb/cow/d) than production of seronegative cows. CLINICAL IMPLICATIONS: The economic impact of N caninum infection in dairy cows can include reduced revenues from decreased milk production, which may warrant culling of young, seropositive replacement stock.