title: Evaluation of a cow-side milk progesterone assay and assessment of the positive predictive value of oestrus diagnosis by dairy farmers in New South Wales.
abstract: OBJECTIVE
  The three objectives of this study were to determine the positive predictive value (PPV) of oestrus diagnosis (heat detection accuracy) by dairy farmers, calculate the diagnostic sensitivity and specificity of the P4 Rapid milk progesterone assay for detecting a corpus luteum and evaluate the economics of using a cow-side milk progesterone assay designed to aid oestrus diagnosis.
  
  
  METHODS
  Milk samples were collected from 752 cows diagnosed in oestrus by farm personnel on 14 dairy farms. Samples were tested using the P4 Rapid milk progesterone assay to estimate the PPV of oestrus diagnosis at each farm and a crude pooled mean of PPV of oestrus diagnosis across all farms. A further 156 milk samples were collected from cows with luteal tissue status determined by transrectal ultrasound and tested by the P4 Rapid assay to enable calculation of the sensitivity and specificity of the P4 Rapid assay.
  
  
  RESULTS
  For pooled farm samples, the PPV was 97.0%, with a range between farms of 88.9-100%. Sensitivity of the P4 Rapid milk progesterone assay for detecting a corpus luteum was 90.1% and specificity was 98.7%. Misclassification of oestrus in cows previously identified as pregnant was the most common cause of false-positive oestrus diagnoses by farm personnel.
  
  
  CONCLUSIONS
  Routine testing of milk progesterone in all cows diagnosed in oestrus is not economically justified and may even slightly reduce submission rates; conversely, strategic use of cow-side milk progesterone assays can improve herd reproductive performance by facilitating decisions on whether to rebreed cows previously diagnosed as pregnant.
authors.affiliation: Livestock Veterinary Teaching and Research Unit, Faculty of Veterinary Science, School of Life and Environmental Sciences, The University of Sydney, Camden, New South Wales 2570, Australia.
authors.forename: L
authors.initials: L
authors.lastname: Ingenhoff
authors.affiliation: Faculty of Veterinary Science, Faculty of Veterinary Science, School of Life and Environmental Sciences, The University of Sydney, Camden, NSW, Australia.
authors.forename: E
authors.initials: E
authors.lastname: Hall
authors.affiliation: Livestock Veterinary Teaching and Research Unit, Faculty of Veterinary Science, School of Life and Environmental Sciences, The University of Sydney, Camden, New South Wales 2570, Australia.
authors.forename: J K
authors.initials: JK
authors.lastname: House
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003612:Dairying / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D004972:Estrus Detection / Q000191:economics / Q000379:methods*; D005260:Female; D008892:Milk / Q000737:chemistry*; D009517:New South Wales; D011247:Pregnancy; D011374:Progesterone / Q000032:analysis*; D012680:Sensitivity and Specificity
chemical_list: D011374:Progesterone
keywords: dairy cattle; heat detection; oestrus detection; progesterone assay