Milk protein profiles in response to Streptococcus agalactiae subclinical mastitis in dairy cows

Anim Sci J. 2016 Jan;87(1):92-8. doi: 10.1111/asj.12391. Epub 2015 Dec 3.


The objective of this study was to investigate the milk protein profiles of normal milk and those of milk during the course of subclinical mastitis, caused by natural Streptococcus agalactiae infection. Two-dimensional gel electrophoresis and liquid chromatography mass spectrometry were used to assess protein profiles and to identify the proteins. The results showed that S. agalactiae subclinical mastitis altered the protein profiles of milk. Following Mascot database matching, 11 and 12 protein types were identified in the milk collected from healthy and S. agalactiae subclinical mastitic udders, respectively. The distinct presence of the antibacterial protein cathelicidin-1 was detected in infected milk samples, which in turn was highly correlated to the severity of subclinical mastitis as represented by the milk somatic cell count (r = 0.616), but not the bacterial count. The protein profile of milk reveals changes in the host response to S. agalactiae intramammary infection; cathelicidin-1 could therefore serve as a biomarker for the detection of subclinical mastitis in dairy cows.

Keywords: 2D-PAGE; antimicrobial protein; bovine; mammary gland; proteomics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antimicrobial Cationic Peptides / analysis
  • Biomarkers / analysis
  • Cathelicidins
  • Cattle
  • Chromatography, Liquid
  • Electrophoresis, Gel, Two-Dimensional
  • Female
  • Mass Spectrometry
  • Mastitis, Bovine / diagnosis
  • Mastitis, Bovine / metabolism*
  • Mastitis, Bovine / microbiology*
  • Milk / chemistry*
  • Milk / cytology
  • Milk Proteins / isolation & purification*
  • Milk Proteins / metabolism*
  • Severity of Illness Index
  • Streptococcal Infections*
  • Streptococcus agalactiae*


  • Antimicrobial Cationic Peptides
  • Biomarkers
  • Milk Proteins
  • Cathelicidins