Alterations in Whey Protein Abundance Correlated with the Somatic Cell Count Identified via Label-Free and Selected Reaction Monitoring Proteomic Approaches

TL;DR

This study identifies specific whey proteins in milk that change with somatic cell count, offering new indicators for udder health and milk quality.

Contribution

The study reveals novel correlations between specific whey proteins and somatic cell count, providing potential biomarkers for intramammary infections.

Findings

Proteins like azurocidin 1 and kininogen-2 increase with higher somatic cell count.

Topoisomerase I, tropomyosin-1, and desmin decrease with elevated somatic cell count.

Differentially abundant proteins are linked to immune response and localization functions.

Abstract

The somatic cell count (SCC) in milk is widely recognized as a reliable indicator for assessing udder health and milk quality. However, the precise relationship between the SCC and milk quality remains inadequately understood. In this study, we conducted a comprehensive analysis of milk samples with varying SCCs to better understand the correlation between specific whey protein levels, the SCC, and intramammary infections. Transition changes in whey protein components dependent on the milk SCC were observed, and several proteins were found to be correlated with SCC. These findings provide a better rudimentary understanding of how milk quality corresponds to the SCC.

The somatic cell count (SCC) is widely used to assess milk quality and diagnose intramammary infections. Several whey proteins have been shown to correlate significantly with SCC and are considered potential indicators of udder health. However, the relationship between milk whey proteins and SCC has not been fully elucidated. In this study, milk samples were grouped into five categories based on SCC levels. Subsequently, whey proteins were identified using a label-free proteomics approach, and the differential abundance of proteins was validated through a selected reaction monitoring (SRM) method. The levels of various proteins, including azurocidin 1 and kininogen-2, exhibited an increase, whereas topoisomerase I, tropomyosin-1, and desmin showed a significant decrease depending on the SCCs. Principal component analysis unveiled that these proteins contributed to the developmental alterations in milk proteins. A majority of these differentially abundant proteins were associated with response to stimulus, localization, and defense response. Our results provide fundamental information on the SCC that can be utilized for evaluating milk quality and serve as potential indicators for detecting intramammary infections.

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