Comparative proteomics analysis of plasma proteins during the transition period in dairy cows with or without subclinical mastitis after calving

The transition period is the most critical time of the cow's lactation cycle that is associated with the onset of mastitis. In this study, changes of plasma proteins in cows (n = 12) with or without subclinical mastitis after calving were determined by two-dimensional electrophoresis (2-DE), which detected 18 spots with variations in protein spots abundance. These spots were identified by liquid chromatography coupled with tandem mass spectrometry. The changes in protein profile from day 21 before calving to day 1 after calving were similar in cows with or without subclinical mastitis. Abundance of α1 acid glycoprotein (AGP) and haptoglobin was dramatically increased at parturition, while transthyretin was down-regulated at parturition, and apolipoprotein E and immunoglobulin gamma 1 were up-regulated at postpartum compared with prepartum in periparturient dairy cows. In cows infected with subclinical mastitis, AGP, haptoglobin, and serum amyloid A were dramatically increased and continued to be elevated in plasma from day 1 to day 21 after calving compared with cows free of mastitis. Changes of protein in plasma at parturition may serve as an immune system response to parturition and lactation process at the protein level and suggest that these altered proteins would not serve as a potential marker for predicting if the periparturient dairy cows are susceptible to subclinical mastitis.