title: Evaluation of digital and optical refractometers for assessing failure of transfer of passive immunity in dairy calves.
abstract: BACKGROUND
  Failure of transfer of passive immunity (FTPI) is the underlying predisposing risk factor for most early losses in dairy calves. Refractometers, either optical or digital, can be used to assess FTPI as a part of calf health monitoring program on dairy operations.
  
  
  OBJECTIVE
  To evaluate the performance of and differences between digital Brix and optical refractometers for assessing FTPI in dairy calves.
  
  
  METHODS
  Two hundred Holstein calves from 1 to 11 days of age.
  
  
  METHODS
  A cross-sectional study was designed to measure serum IgG concentration by radial immunodiffusion (RID) assay, digital Brix and optical refractometers. The correlation coefficients (r) between the 2 refractometers were plotted against each other and against the measured IgG concentration from RID. The Se, Sp, and accuracy of digital Brix and optical refractometers for assessing FTPI using previously recommended cut-offs were calculated. A receiver operating characteristic curve was created and used to identify the optimal cut-off for this dataset.
  
  
  RESULTS
  The RID IgG concentration was positively correlated with digital Brix (r = 0.79) and optical (r = 0.74) refractometers. The best combination of Se (85.5%), Sp (82.8%), and accuracy (83.5%) of digital Brix refractometer was at 8.3%Brix. For optical refractometer, the best combination of Se (80%), Sp (80.7%), and accuracy (80.5%) was at 5.5 g/dL.
  
  
  CONCLUSIONS
  Both refractometers exhibited utility in assessing FTPI in dairy calves.
authors.affiliation: Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada, C1A 4P3; Infectious Diseases, Department of Animal Medicine, Faculty of Veterinary Medicine, Zagazig University, Zagazig City, 44511, Sharkia Province, Egypt.
authors.forename: I
authors.initials: I
authors.lastname: Elsohaby
authors.forename: J T
authors.initials: JT
authors.lastname: McClure
authors.forename: G P
authors.initials: GP
authors.lastname: Keefe
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002417:Cattle / Q000276:immunology / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D007112:Immunity, Maternally-Acquired / Q000502:physiology*; D012031:Refractometry / Q000295:instrumentation*
keywords: Immunoglobulin G; Radial immunodiffusion assay; Serum total protein
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