Differential Expressions Between Colostrum and Mature Milk in Primiparous Holstein Cows with Integrations of Lipidomic and Proteomics

In the current study, by integrating the analyses of lipidomics and proteomics, the compositional differences between colostrum and mature milk of Holstein cows were systematically investigated. We have identified a total of 1863 lipid metabolites and 1690 proteins. A small portion of them were highly differentiated between colostrum and mature milk. Among them, 23 highly differentiated lipid metabolites and 17 proteins were screened to run correlation analysis. The results showed that they are highly correlated; therefore, they could serve as biomarkers to distinguish colostrum from mature milk. Furthermore, among lipid metabolites, triacylglycerol (TG) (10:0_11:0_12:0) and sphingomyelin (SM) (20:0;2O/44:11) were identified as key regulatory molecules in glycerophospholipid metabolism and sphingomyelin metabolism. In proteins, cadherin 3 (CDH3) protein and alpha-S1-casein (CSN1S1) protein have been identified as potentially important characteristic proteins. In addition, the level of α-ketoglutarate (α-KG) in colostrum was two-fold lower than that in mature milk and its level strongly correlated with several differentiated metabolites and tricarboxylic acid (TCA) cycle-related proteins, including isocitrate dehydrogenase 1 (IDH1), aconitase 1 (ACO1), and dihydrolipoamide dehydrogenase (DLD). This indicates that α-KG is one of the most important differential molecules to determine the compositions of colostrum and mature milk. These findings provide molecular basis for understanding the nutritional value and the regulatory mechanisms related to the compositions of colostrum and mature milk.