title: Protein expression in dairy cows with and without subclinical hypocalcaemia.
abstract: OBJECTIVE
  To determine differences in plasma proteomic profiles between healthy cows and those with subclinical hypocalcaemia within 12 hours after calving, and thereby explore the underlying biological mechanism of subclinical hypocalcaemia in dairy cows.
  
  
  METHODS
  Plasma samples were collected within 6 hours of calving from Holstein cows on a farm in Heilongjiang, China; 32 with subclinical hypocalcaemia (plasma calcium concentration 1.38-2.00 mmol/L and no clinical signs) and 59 control cows (plasma calcium concentration 2.10-2.8 mmol/L). Plasma samples were applied to weak cationic exchange protein chips for protein profiling by surface-enhanced laser desorption/ionisation time-of-flight mass spectrometry (SELDI-TOF-MS), and the data were analysed using the PBS-IIC system. The amplitude of peaks for the two groups were compared using the Wilcoxon sum-rank test, and the mass-to-charge ratio of the peaks that differed was used to identify peptide fragments using the Swiss-Prot protein database.
  
  
  RESULTS
  Seven peaks were identified in the subclinical hypocalcaemia group that differed from those of the control group (p<0.001), that represented six unique proteins. Expression of serum albumin, fibrinogen alpha chain, amyloid beta A4 proteins and neurosecretory protein VGF were increased, and expression of apolipoprotein A-II and serum amyloid A proteins were decreased in the subclinical hypocalcaemic cows compared with control cows.
  
  
  CONCLUSIONS
  Use of SELDI-TOF-MS technology can effectively identify differences in plasma protein expression patterns in cows with subclinical hypocalcaemia. Neurosecretory protein VGF and amyloid beta A4 protein might represent useful biomarkers for diagnosis of subclinical hypocalcaemia.
authors.affiliation: a College of Animal Science and Veterinary Medicine , Heilongjiang Bayi Agricultural University , Daqing 163319 , China.
authors.forename: P X
authors.initials: PX
authors.lastname: Wang
authors.affiliation: a College of Animal Science and Veterinary Medicine , Heilongjiang Bayi Agricultural University , Daqing 163319 , China.
authors.forename: S
authors.initials: S
authors.lastname: Shu
authors.affiliation: a College of Animal Science and Veterinary Medicine , Heilongjiang Bayi Agricultural University , Daqing 163319 , China.|b Synergetic Innovation Center of Food Safety and Nutrition , Northeast Agricultural University , Harbin 150030 , China.
authors.forename: C
authors.initials: C
authors.lastname: Xia
authors.affiliation: c College of Animal Science and Veterinary Medicine , Jilin University , Chang Chun 130062 , China.
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.affiliation: a College of Animal Science and Veterinary Medicine , Heilongjiang Bayi Agricultural University , Daqing 163319 , China.
authors.forename: L
authors.initials: L
authors.lastname: Wu
authors.affiliation: a College of Animal Science and Veterinary Medicine , Heilongjiang Bayi Agricultural University , Daqing 163319 , China.
authors.forename: B
authors.initials: B
authors.lastname: Wang
authors.affiliation: a College of Animal Science and Veterinary Medicine , Heilongjiang Bayi Agricultural University , Daqing 163319 , China.
authors.forename: C C
authors.initials: CC
authors.lastname: Xu
authors.affiliation: a College of Animal Science and Veterinary Medicine , Heilongjiang Bayi Agricultural University , Daqing 163319 , China.
authors.forename: J
authors.initials: J
authors.lastname: Liu
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000378:metabolism*; D003612:Dairying; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D006996:Hypocalcemia / Q000378:metabolism / Q000662:veterinary*
keywords: SELDI-TOF-MS; Subclinical hypocalcaemia; dairy cows; plasma proteomics