A proteomic perspective on the changes in milk proteins due to high somatic cell count

Abstract

Although cows with subclinical mastitis have no difference in the appearance of their milk, milk composition and milk quality are altered because of the inflammation. To know the changes in milk quality with different somatic cell count (SCC) levels, 5 pooled bovine milk samples with SCC from 10(5) to 10(6) cells/mL were analyzed qualitatively and quantitatively using both one-dimension sodium dodecyl sulfate PAGE and filter-aided sample preparation coupled with dimethyl labeling, both followed by liquid chromatography tandem mass spectrometry. Minor differences were found on the qualitative level in the proteome from milk with different SCC levels, whereas the concentration of milk proteins showed remarkable changes. Not only immune-related proteins (cathelicidins, IGK protein, CD59 molecule, complement regulatory protein, lactadherin), but also proteins with other biological functions (e.g., lipid metabolism: platelet glycoprotein 4, butyrophilin subfamily 1 member A1, perilipin-2) were significantly different in milk from cows with high SCC level compared with low SCC level. The increased concentration of protease inhibitors in the milk with higher SCC levels may suggest a protective role in the mammary gland against protease activity. Prostaglandin-H2 D-isomerase showed a linear relation with SCC, which was confirmed with an ELISA. However, the correlation coefficient was lower in individual cows compared with bulk milk. These results indicate that prostaglandin-H2 D-isomerase may be used as an indicator to evaluate bulk milk quality and thereby reduce the economic loss in the dairy industry. The results from this study reflect the biological phenomena occurring during subclinical mastitis and in addition provide a potential indicator for the detection of bulk milk with high SCC.

Inclusion of grape marc in dairy cattle rations alters the bovine milk proteome

“…These same proteins have also been identified as potential proteins of interest in mastitis research, which is another circumstance of shifted passage dynamics between the blood and milk. Zhang et al (2015) identified a relationship between SCC score of the milk and BTN, apolipoprotein E, clusterin, kininogen-1, sodium dependent phosphate transport protein 2B, and platelet glycoprotein 4 abundance. In the experiment by Zhang et al (2015), none of these proteins followed a positive linear correlation with increasing SCC content of milk, but instead these proteins all peaked in abundance in the samples containing between 4 × 10 5 and 7.5 × 10 5 cells/l and were often present at significantly lower abundances in the milk with the highest SCC content (10 6 cells/ml) compared to the low SCC milk sample.…”

“…Zhang et al (2015) identified a relationship between SCC score of the milk and BTN, apolipoprotein E, clusterin, kininogen-1, sodium dependent phosphate transport protein 2B, and platelet glycoprotein 4 abundance. In the experiment by Zhang et al (2015), none of these proteins followed a positive linear correlation with increasing SCC content of milk, but instead these proteins all peaked in abundance in the samples containing between 4 × 10 5 and 7.5 × 10 5 cells/l and were often present at significantly lower abundances in the milk with the highest SCC content (10 6 cells/ml) compared to the low SCC milk sample. Our observation of lower serum albumin in milk from GPM-fed cows is contradictory to the well reported increase of serum albumin in milk, including by Zhang et al (2015), during mastitis conditions; however, this could be a result of our enrichment method, specifically the inclusion of ProteoMiner treatment in our workflow, and hence interpretation of this specific protein should be done with caution.…”

Somatic cell count and milk yield on physicochemical components of milk from free-stall housed cows

“…According to Auldist and Hubble (1998), due to the reduction in casein synthesis and a simultaneous increase in serum milk proteins, there is no consensus in the literature regarding the increase in the total protein percentage in the milk of animals with high SCC. In a recent study, Zhang et al (2015) tried to understand the changes in the quality of milk with different SCC levels (10 5 to 10 6 cells mL -1 ). They discovered that milk samples with higher SCC have higher concentrations of proteins with immunological function (cathelicidins, prostaglandins and immunoglobulins).…”

“…When mastitis occurs, although milk is visually normal, it has a high somatic cell count (SCC) and a change in its natural composition, such as increased levels of serum proteins (ZHANG et al, 2015), and a decrease in the casein, lactose, total solids and fat contents. These changes depend on the degree of infection and the stage of the disease in the animal (PEREIRA et al, 1997;SILVA et al, 2010;COELHO et al, 2012;GUARIGLIA et al, 2015).…”

Optimization of Preservation Methods Allows Deeper Insights into Changes of Raw Milk Microbiota

“…Whether they involve gene expression analyses of microbial communities (metatranscriptomics), identification and quantification (meta-metabolomics) of their metabolites or proteome analysis (metaproteomics), they all depend on microbiome stability for consistent and reliable study results. Sodium azide, one of the main constituents of azidiol, has been successfully used to minimize bacterial growth during proteomic studies on distinct matrices such as milk [69] or urine [70]. Additionally, chloramphenicol, another constituent of azidiol, has been extensively used in studies characterizing proteome dynamics of microbial antibiotic resistance.…”