Association of serologic status for Neospora caninum with postweaning weight gain and carcass measurements in beef calves

Objective-To determine the seroprevalence for Neospora caninum in a population of beef calves in a feedlot and the association of serologic status with postweaning weight gain and carcass measurement. Design-Longitudinal observational study. Animals-1,009 weaned beef steers from 92 herds. Procedure-Samples were obtained from all steers at time of arrival at a feedlot. Serologic status for Neospora spp was determined, using an agglutination test. Results of serologic testing were compared with I calf growth and carcass data, using multivariate regression with generalized estimating equations. Results-Of 1,009 carves, 131 (12.98%) were seropositive, and 54 of 92 (58.7%) consignments had greater than or equal to 1 seropositive calf. Median within-consignment prevalence for consignments in which there was greater than or equal to 1 seropositive calf was 20%. Seropositive status was associated with significant reductions in average daily gain, live body weight at slaughter, and hot carcass weight and an increase in ribeye area-to-hot carcass weight ratio. Seropositive status also was associated with significant increases in cost of treatment and significant reductions in income. Sick seropositive calves had the highest cost of treatment. An economic loss of $15.62/calf was projected for seropositive calves. Conclusions and Clinical Relevance-Significant reductions in postweaning weight gain, carcass weight, and economic return were associated with detection of antibodies to N caninum in beef calves ina feedlot.