Exploratory Lipidomic Comparison of Neutral and Polar Lipid Profiles Between Mare and Cow Milk Under a Shared Grazing Environment

This exploratory study used UHPLC-HRMS/MS-based non-targeted lipidomics to compare milk lipid profiles between eight Yili mares and eight Xinjiang Brown cows maintained under a shared grazing environment. A total of 2460 lipid molecules were annotated across all confidence levels, and 1013 high-confidence Grade A/B lipids were retained for differential analysis. Forty-five differential lipids were identified, including 21 enriched in mare milk and 24 enriched in cow milk. Cow-milk-enriched lipids were mainly triacylglycerols with low double-bond numbers, consistent with neutral lipid deposition and glycerolipid-related features. In contrast, mare-milk-enriched lipids were more widely distributed among polar-lipid and membrane-related classes, including phosphatidylethanolamine, lysophosphatidylethanolamine, lysophosphatidylcholine, phosphatidylinositol, and ceramide, and showed broader unsaturation patterns. KEGG analysis provided supplementary, positive-ion-mode pathway support for lipid digestion and absorption, glycerolipid metabolism, cholesterol metabolism, and lipolysis-related processes, whereas negative-ion-mode mappings were not statistically significant. Overall, Yili mare milk and Xinjiang Brown cow milk shared a similar major lipid framework but differed in selected neutral-lipid and polar-lipid molecular profiles under the sampled conditions. These candidate features require validation in larger, multi-breed, multi-season datasets before being generalized as robust markers of mare-versus-cow milk differences.