Fatty acid profile of phospholipids and sphingomyelin in milk and regulation of sphingomyelin synthesis of mammary glands in cows receiving increasing levels of crushed sunflower seeds

摘要

The objective of this study was to investigate theeffect of increasing dietary supplementation of crushedsunflower seed (CSS) in the diet of dairy cows on thefatty acid (FA) composition of phospholipids andsphingomyelin in milk, and on mammary transcriptionof genes that are important for sphingomyelin denovo synthesis. Four groups of 6 cows received dietssupplemented with CSS at 0% (control), or 5, 10, or15% of dry matter for a 5-wk experimental period. Milksamples and mammary biopsies were collected at theend of the experiment. Phospholipid concentration inmilk fat decreased linearly with CSS supplementation.Sphingomyelin concentration in milk fat was unaffectedby CSS supplementation. Daily yield of phospholipidsdecreased linearly with CSS supplementation. Dailyyield of sphingomyelin was not significantly affected.The CSS supplementation linearly increased the proportionof monounsaturated FA in milk phospholipids.The major isomer incorporated into phospholipids wasC18:1 (n-9 cis), which showed a linear increase withCSS supplementation. The C22:0 proportion in sphingomyelinincreased linearly with CSS supplementationand constituted between 15.2 to 25.4% of total FA insphingomyelin. However, CSS supplementation linearlydecreased C23:0 sphingomyelin. Mammary transcriptionof serine palmitoyl transferase, long chain subunit1 and subunit 2, the rate-limiting enzymes in ceramidesynthesis, showed a linear decrease with increasing CSSsupplementation. In conclusion, the data showed thatdietary supplementation of CSS linearly increased theproportion of unsaturated FA and monounsaturatedFA in milk phospholipids with no effect on phospholipidconcentration. In addition, CSS supplementationlinearly decreased n-3 polyunsaturated fatty acid proportionin sphingomyelin. The results further showedthat mammary transcription of important genes forsphingomyelin de novo synthesis is regulated by lipidsupplementation.