Reduction in bovine milk fat globule size is characterized by remodeling of membrane-associated lipids in milk.

Milk fat globule (MFG) size is closely linked to milk lipid interfacial organization, but its association with membrane-associated lipid remodeling remains unclear. Here, milk composition, MFG size distribution, fatty acid profiles, and whole-milk lipidomics were analyzed in conjugated linoleic acid (CLA)-supplemented cows. CLA supplementation reduced milk fat content and shifted MFGs toward smaller sizes. Whole-milk lipidomics showed that the small-MFG phenotype was accompanied by remodeling of membrane-associated lipid classes, particularly sphingolipids. Among major sphingolipids, hexosylceramides (HexCer) showed the most consistent associations with MFG structural traits and were characterized by increased lower-carbon molecular groups and reduced abundance-weighted carbon number and double bond number. These findings identify HexCer as a prominent sphingolipid structural marker associated with MFG size reduction.