Transcriptome analysis reveals key information on improving duck yolk lipid contents induced by dietary fish oil or flaxseed oil

Genes participating in the changes of yolk lipids by unsaturated oils remain elusive. In this study, ducks were randomly assigned to 3 groups, fed with basal-diet (C), basal-diet-plus-2%-flaxseed-oil (FL), or basal-diet-plus-2%-fish-oil (F), respectively. A digital-gene-expression-profiling analysis of livers were performed after four weeks. Compared to C, 36 and 25 differently-expressed-genes (DEG) were identified in FL and F, respectively. These genes participated in lipid metabolism pathways. In both F and FL, the sterol 12 α-hydroxylase 1 gene was down regulated, as well as the fatty acid synthase gene and stearoyl-CoA desaturase gene. In FL, the fatty acid desaturase 2 gene (FADS2) and elongation of the very long-chain fatty acids protein 2 gene (ELOVL2) were up regulated, and the CYP2U (cytochrome P450, family 2, subfamily U) was down regulated. However, the FADS2 and ELOVL2 were down regulated in F to possibly prevent the redundancy of body n-3 PUFAs. In conclusion, FL and F had different molecular pathways to reduce yolk cholesterol and increase n-3 PUFAs. However, CYP8B1 and FADS2 were the key genes in the regulation of both of them. α-linolenic acid in the FL might be transformed to longer n-3 PUFAs. In addition, this study adds sequence information to duck.