Untargeted metabonomic analysis reveals the composition and changes of milk metabolites in dual-purpose cattle (Bos taurus) population

The milk metabolite composition and utility of dual-purpose cattle breeds are frequently disregarded. Using LC‒MS/MS, we constructed expression profiles of 4217 and 3718 milk metabolites from 198 Xinjiang brown cattle (XJBC) and 158 Chinese Simmental cattle (CSC), respectively. 2930 and 2446 metabolites in XJBC milk (XJBCm) and CSC milk (CSCm) exhibit specificity, respectively. Compared with CSCm, XJBCm has a higher percentage of milk fat, milk protein, and lactose, as well as more varieties and higher expression levels of fatty acids, glycerophospholipids, diradylglycerols, carbohydrates, nucleosides, and nucleotides. Differentially expressed metabolites (DEMs) analysis showed that some lipids and lips-like molecules, organic acids and derivatives, organic oxygen compounds, organoheterocyclic compounds and other metabolites were differentially expressed in different lactation stages of XJBC and CSC. Parity and age had no significant effect on the expression of metabolites in milk. Meanwhile, 192, 1,488, 1,979, and 1484 DEMs were screened in low vs. high milk fat percentages, low vs. high milk protein percentages, low vs. high lactose percentages, and low vs. high somatic cell counts (SCCs) of XJBCm, respectively. Kyoto encyclopedia of genes and genomes (KEGG) analysis showed that DEMs may be related to the SCC, milk fat percentage, milk protein percentage, and lactose percentage in XJBCm and CSCm by participating in glucose, lipid, purine, hormone, bile acid, and energy metabolism-related pathways or ABC transporters. Finally, 3′,5′-cGMP, glyoxylate, uric acid, L-glutamine, xylitol, L-arginine, L-glutamate, cinnamaldehyde, and phorbol are candidate marker metabolites associated with SCC in dual-purpose cattle milk. • Milk metabolite profiles from two largest dual-purpose cattle breeds in china were built. • The nutritional characteristics of dual-purpose cattle were revealed. • Lactation stage significantly affects the expression of milk metabolites from dual-purpose cattle. • Multiple marker metabolites associated with SCC were identified in dual-purpose cattle.