title: Association of herd composition, stocking rate, and duration of calving season with fecal shedding of Cryptosporidium parvum oocysts in beef herds.
abstract: OBJECTIVE
  To evaluate the association of herd demographics, parturition variables, stocking rate, and rotational grazing practices with the probability of fecal shedding of Cryptosporidium parvum from beef cow-calf herds in California.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  38 beef cow-calf operations.
  
  
  METHODS
  Fecal specimens were collected and examined for C parvum oocysts, using immunofluorescent microscopy. Association between various demographic and management factors and the probability of shedding C parvum were statistically evaluated.
  
  
  RESULTS
  Adjusted for age and month of collection of a fecal sample, cattle from herds with a high number of young calves (< or = 2 months old) on the day of sample collection, a high stocking rate (No. of cattle/acre/mo), or a longer calving season were more likely to shed C parvum oocysts, compared with cattle from herds with fewer young calves, a lower stocking rate, or a shorter calving season. Cattle from herds with a higher number of older calves (> 2 months old) on the day of sample collection were less likely to shed C parvum oocysts, compared with cattle from herds with fewer older calves. Using our multivariate model, rotational grazing systems or season of onset of calving were not associated with shedding status for C parvum oocysts.
  
  
  CONCLUSIONS
  Reproductive management that would result in a shorter calving season and use of a lower stocking rate for cattle may be associated with reduced risk of C parvum shedding. Intensive rotational grazing systems and time of year for onset of calving season apparently have little effect on reducing prevalence of oocyst shedding.
authors.affiliation: Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California-Davis, Tulare 93274, USA.
authors.forename: E R
authors.initials: ER
authors.lastname: Atwill
authors.forename: E M
authors.initials: EM
authors.lastname: Johnson
authors.forename: M G
authors.initials: MG
authors.lastname: Pereira
mesh_terms: D000367:Age Factors; D000822:Animal Husbandry; D000818:Animals; D002140:California; D002417:Cattle; D002418:Cattle Diseases / Q000469:parasitology* / Q000635:transmission; D003430:Cross-Sectional Studies; D003457:Cryptosporidiosis / Q000469:parasitology / Q000635:transmission / Q000662:veterinary*; D016785:Cryptosporidium parvum / Q000502:physiology*; D005243:Feces / Q000469:parasitology; D005260:Female; D019085:Fluorescent Antibody Technique, Direct / Q000662:veterinary; D016015:Logistic Models; D015999:Multivariate Analysis; D012621:Seasons