UPLC-QE-MS Analysis of the Differences in Milk Metabolites from Guanzhong Dairy Goats at the Peak and Late Lactation Stages

In order to explore the dynamic changes of metabolites in goat milk during different lactation periods, the differential metabolites in milk from Guanzhong dairy goats at the peak and late lactation stages were investigated by ultra-high performance liquid chromatography-quadrupole electrostatic field orbitrap mass spectrometry (UPLC-QE-MS). A total of 90 differential metabolites were identified using P < 0.05, variable importance in the projection (VIP) > 1.00, and fold change (FC) > 2 or < 0.5 as criteria. Compared with late-lactation milk, 50 differential metabolites were up-regulated and 40 down-regulated in peak-lactation milk. Metabolic pathway analysis showed that these differential metabolites were significantly correlated with the biosynthesis of secondary bile acids. According to the VIP, uridine diphosphate-N-acetylglucosamine and phosphatidylethanolamine (PE, 12:0/22:2(13Z,16Z)) could be considered as potential biomarkers for the differential changes of milk metabolites from Guanzhong dairy goats during the two lactation periods, but this needs further research to be confirmed.