Objective-To determine the seroprevalence for Neospora caninum in a populat
ion of beef calves in a feedlot and the association of serologic status wit
h 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 fee
dlot. Serologic status for Neospora spp was determined, using an agglutinat
ion test. Results of serologic testing were compared with I calf growth and
carcass data, using multivariate regression with generalized estimating eq
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 wi
thin-consignment prevalence for consignments in which there was greater tha
n or equal to 1 seropositive calf was 20%. Seropositive status was associat
ed with significant reductions in average daily gain, live body weight at s
laughter, and hot carcass weight and an increase in ribeye area-to-hot carc
ass weight ratio. Seropositive status also was associated with significant
increases in cost of treatment and significant reductions in income. Sick s
eropositive 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 we
ight gain, carcass weight, and economic return were associated with detecti
on of antibodies to N caninum in beef calves ina feedlot.