Integrated lipidomics and fatty acid positional distribution for nutritional assessment of nine mammalian milks

The nutritional value of milk fat depends on lipid and fatty acid composition. This study characterized the lipidomics and fatty acid positional distribution of milk from nine mammalian species: cow, buffalo, yak, goat, sheep, camel, mare, donkey, and human. Lipid molecular species were profiled by liquid chromatography-tandem mass spectrometry. Fatty acid positional distribution was determined using NH₂ and Si solid-phase extraction, selective sn-1/3 hydrolysis by Candida antarctica lipase B, and sn-2 monoacylglycerol quantification by gas chromatography-mass spectrometry. Ruminant milks showed high compositional similarity and differed from camel and monogastric milks. Compared to human milk, animal milks had higher triacylglycerols, phosphatidylcholines, phosphatidylethanolamines, and sphingomyelins, but lower free fatty acids and diacylglycerols. Short-chain fatty acids consistently occupied sn-1/3 positions, whereas medium-chain, long-chain, odd-chain, and branched-chain fatty acids favored sn-2 position. Monogastric milks exhibited sn-2 preference for palmitic acid and other saturated fatty acids and sn-1/3 preference for unsaturated fatty acids; ruminant and camel milks showed the reverse. Bray-Curtis analysis identified donkey milk as the closest lipidomic analog to human milk, followed by mare milk. These findings provide a systematic reference for evaluating mammalian milks and data for humanized infant formula lipid design.