Neospora caninum serostatus and culling of Holstein cattle.
OBJECTIVE
To determine whether time until culling or risk of culling was associated with Neospora caninum serostatus among Holstein cattle in dairy herds in Ontario.


METHODS
Retrospective cohort study.


METHODS
3,412 cows in 56 herds.


METHODS
Blood samples were collected, and serum was tested for antibodies against N. caninum. Information on cows that were culled was collected during the 1- to 2-year period that producers were unaware of serostatus of individual cows in their herds.


RESULTS
Herd prevalence of N. caninum-seropositive cows ranged from 0 to 68.3% (median, 7.0%). During the time of the study, 184 of 359 (51.3%) N. caninum-seropositive cows were culled, compared with 1,388 of 3,053 (45.5%) seronegative cows. Mean time from blood sample collection to culling for seronegative cows (289 days; 95% confidence interval, 280 to 299 days) was not significantly different from mean time for seropositive cows (296 days; 95% confidence interval, 269 to 323 days). Survival analysis indicated that N. caninum serostatus was not associated with time to culling or risk of culling.


CONCLUSIONS
Results suggest that N. caninum serostatus of Holstein cows in Ontario was not significantly associated with either time to culling or risk of culling. Thus, N. caninum serostatus alone should not be used to determine whether cows should be culled.
Cramer
Gerard
G
Department of Population Medicine, Ontario Veterinary College, University of Guelph, Canada.
Kelton
David
D
Duffield
Todd F
TF
Hobson
Jamie C
JC
Lissemore
Kerry
K
Hietala
Sharon K
SK
Peregrine
Andrew S
AS
D000034:Abortion, Veterinary / Q000469:parasitology*; D000822:Animal Husbandry / Q000379:methods / Q000592:standards; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology*; D003048:Coccidiosis / Q000453:epidemiology / Q000662:veterinary*; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D018688:Neospora / Q000276:immunology*; D009864:Ontario / Q000453:epidemiology; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000453:epidemiology / Q000662:veterinary; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D016036:Seroepidemiologic Studies
D000913:Antibodies, Protozoan