title: Predicted ages of dairy calves when colostrum-derived bovine viral diarrhea virus antibodies would no longer offer protection against disease or interfere with vaccination.
abstract: OBJECTIVE
  To develop models that could be used to predict, for dairy calves, the age at which colostrum-derived bovine viral diarrhea virus (BVDV) antibodies would no longer offer protection against infection or interfere with vaccination.
  
  
  METHODS
  Prospective observational field study.
  
  
  METHODS
  466 calves in 2 California dairy herds.
  
  
  METHODS
  Serum BVDV neutralizing antibody titers were measured from birth through 300 days of age. The age by which colostrum-derived BVDV antibodies had decayed sufficiently that calves were considered susceptible to BVDV infection (ie, titer < or = 1:16) or calves became seronegative was modeled with survival analysis methods. Mixed-effects regression analysis was used to model colostrum-derived BVDV antibody titer for any given age.
  
  
  RESULTS
  Half the calves in both herds became seronegative for BVDV type I by 141 days of age and for BVDV type II by 114 days of age. Rate of antibody decay was significantly associated with antibody titer at 1 to 3 days of age and with whether calves were congenitally infected with BVDV. Three-month-old calves were predicted to have a mean BVDV type-I antibody titer of 1:32 and a mean BVDV type-II antibody titer of 1:16.
  
  
  CONCLUSIONS
  Results provide an improved understanding of the decay of BVDV-specific colostrum-derived antibodies in dairy calves raised under typical field conditions. Knowledge of the age when the calf herd becomes susceptible can be useful when designing vaccination programs aimed at minimizing negative effects of colostrum-derived antibodies on vaccine efficacy while maximizing overall calf herd immunity.
authors.affiliation: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616, USA.
authors.forename: Claudia A
authors.initials: CA
authors.lastname: Muñoz-Zanzi
authors.forename: Mark C
authors.initials: MC
authors.lastname: Thurmond
authors.forename: Wesley O
authors.initials: WO
authors.lastname: Johnson
authors.forename: Sharon K
authors.initials: SK
authors.lastname: Hietala
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D000914:Antibodies, Viral / Q000009:adverse effects / Q000097:blood / Q000276:immunology*; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000517:prevention & control*; D002417:Cattle; D003126:Colostrum / Q000276:immunology*; D001908:Diarrhea Viruses, Bovine Viral / Q000276:immunology*; D005260:Female; D007112:Immunity, Maternally-Acquired; D009500:Neutralization Tests / Q000662:veterinary; D011446:Prospective Studies; D013997:Time Factors; D014611:Vaccination / Q000662:veterinary*
chemical_list: D000914:Antibodies, Viral