Label-free-based proteomics analysis reveals differential proteins of sheep, goat, and cow milk

Regarding the limited information on species protein differences between sheep, goat, and cow milk, we analyzed the differentially expressed proteins in sheep, goat, and cow milk and their functional differences using label-free proteomics technology to identify potential biomarkers. In all, 770 proteins and 2,914 peptide segments were identified. Statistical analysis showed significant differences in the relative abundances of the 74 proteins among sheep, goat, and cow milk. CSN3 and LALBA can be used as potential biomarkers for goat milk, XDH can be used as a potential biomarker for cow milk, and CTSB and BPIFB1 can be used as potential biomarkers for sheep milk. Functional analysis using Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes showed that these significantly different proteins were enriched by different pathways, including thyroid hormone synthesis and glycerol phospholipid metabolism. The data revealed differences in the amounts and physiological functions of the milk proteins of different species, which may provide an important basis for research on the nutritional composition of dairy products and adulteration identification technology.