Comparative analysis of sheep, goat, and cow milk based on non-targeted metabolomics

Sheep milk is rich in milk fat, milk protein, vitamins, and minerals, and is also an important source of natural bioactive substances. In recent years, the food and drug functions of sheep milk have been explored, so it is important to understand the specific metabolites in sheep milk in order to study its specific functions. In this study, we performed routine composition analysis of sheep, goat, and cow milk, and non-targeted metabolomics was used to quantify differences in milk metabolites and related metabolic pathways. The contents of fat, non-fat solids, protein, and total solids in sheep milk were significantly higher than those in goat and cow milk (P < 0.05). In total, 178 metabolites were identified in sheep and goat milk, of which 74 were elevated abundance and 104 were lower concentration in sheep milk. In total, 223 metabolites were identified in sheep and cow milk, of which 80 were elevated abundance and 143 were lower concentration in sheep milk. The results indicated that the main differences in metabolites between sheep milk and other milk samples were lipids, lipid analogues, organic acids and their derivatives, organic heterocyclic compounds, nucleotides, nucleotides and their analogues, and were identified through KEGG analysis, mainly enriched in metabolic pathways. This conclusion was consistent with the previous research results of our laboratory that dietary sheep milk can improve lipid metabolism. This study identified the differential metabolites between sheep milk and cow milk as well as goat milk, laying a foundation for subsequent research on the specific bioactive substances and their functions in sheep milk.