title: The epidemiology of subfertility in non-seasonal calving dairy herds in the Camden region of New South Wales: preliminary investigation of risk factors.
abstract: OBJECTIVE
  To investigate relationships between biographic, reproductive, production and disease traits and subfertility among 965 Holstein cows from 10 non-seasonal calving dairy herds in the Camden region of New South Wales.
  
  
  METHODS
  A retrospective case-control study
  
  
  METHODS
  Biographical, disease and reproductive data were collated from computerised records for cows with lactations that commenced between 1 July 1995 and 30 June 1996 and univariable and bivariable associations with subfertility were determined.
  
  
  RESULTS
  Records from 965 cows that conceived were considered for risk factor analyses. Associations between subfertility and a number of risk factors (P < 0.3) were detected. Significant (P < 0.05) risk factors for subfertility in multiparous cows included herd of origin and, after controlling for the effect of herd, subfertility in the previous lactation, greater than 62 days dry, parity greater than five, interval between calving and first recorded heat, metritis and cystic ovarian disease. Herd of origin and, after controlling for herd effects, dystocia, metritis and percentage of milk fat plus protein at the time of first service were significant (P < 0.05) risk factors for subfertility in primiparous cows. The direction and magnitude of these associations are presented.
  
  
  CONCLUSIONS
  Subfertility has a similar rate of occurrence in the herds examined to that reported overseas. Although herd of origin has a substantial effect on individual risk of subfertility, cow-level risk factors for subfertility are likely to exist. Exposures differ between primiparous and multiparous cows.
authors.affiliation: University Veterinary Centre, Faculty of Veterinary Science, The University of Sydney, Camden, New South Wales.
authors.forename: N
authors.initials: N
authors.lastname: Moss
authors.forename: I J
authors.initials: IJ
authors.lastname: Lean
authors.forename: S W J
authors.initials: SW
authors.lastname: Reid
authors.forename: D R
authors.initials: DR
authors.lastname: Hodgson
mesh_terms: D000818:Animals; D016022:Case-Control Studies; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000209:etiology*; D003612:Dairying / Q000706:statistics & numerical data; D005260:Female; D007246:Infertility / Q000453:epidemiology / Q000209:etiology / Q000662:veterinary*; D007774:Lactation; D009517:New South Wales / Q000453:epidemiology; D012098:Reproduction; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons