title: Neospora caninum serostatus and culling of Holstein cattle.
abstract: 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.
authors.affiliation: Department of Population Medicine, Ontario Veterinary College, University of Guelph, Canada.
authors.forename: Gerard
authors.initials: G
authors.lastname: Cramer
authors.forename: David
authors.initials: D
authors.lastname: Kelton
authors.forename: Todd F
authors.initials: TF
authors.lastname: Duffield
authors.forename: Jamie C
authors.initials: JC
authors.lastname: Hobson
authors.forename: Kerry
authors.initials: K
authors.lastname: Lissemore
authors.forename: Sharon K
authors.initials: SK
authors.lastname: Hietala
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Peregrine
mesh_terms: 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
chemical_list: D000913:Antibodies, Protozoan