Changes in long‐chain fatty acid composition of milk fat globule membrane and expression of mammary lipogenic genes in dairy cows fed sunflower seeds and rumen‐protected choline

Summary The aim of this experiment was to investigate the effect of dietary supplementation of crushed high oleic sunflower seeds (HOS) and rumen‐protected choline (RPC) on the fatty acid (FA) profile of phospholipids and sphingomyelin and mammary transcription of genes that are important for milk fat synthesis and de novo synthesis of sphingolipids. Twenty‐four cows were divided into four groups that either received an unsupplemented diet (Control), the Control diet supplemented with 50 g RPC per day, a diet supplemented with HOS at 10% of dry matter, or RPC and HOS in combination (RPC + HOS). RPC supplementation had no effect on the FA composition of milk or sphingomyelin. Cows receiving RPC and RPC + HOS had increased incorporation of C22:5 (n‐3) into phospholipids. Milk FA proportion of C18:0 and C18:1 isomers was increased in cows receiving HOS (HOS and RPC + HOS). Sphingomyelin proportion of C22:0 was increased in cows receiving HOS and RPC + HOS, at the expense of C23:0. HOS supplementation further increased the proportion of unsaturated fatty acids (UFA) in milk phospholipids. HOS supplementation increased mammary transcription of UDP‐glucose ceramide glycosyltransferase ( UGCG ), sterol response element‐binding protein cleavage‐activating protein ( SCAP ) and peroxisome proliferation‐activated receptor Gamma subunit C 1b ( PPARGC1b ), and reduced transcription of insulin induced gene 1 ( INSIG1 ) and fatty acid‐binding protein 3 ( FABP3 ). Dietary supplementation of RPC increased mammary transcription of fatty acid desaturase 1 ( FADS1 ) and longevity assurance gene 2 ( LASS2 ), and reduced transcription of sphingomyelin synthase ( SGMS ). The results show that the FA profile of milk phospholipids is sensitive to dietary lipid supplementation and, to a minor degree, RPC supplementation. Furthermore, transcription of genes that are important for milk fat synthesis and sphingolipids synthesis is affected by dietary supplementation of RPC and HOS.