1854
Transcriptome profiling of milk in dairy cows fed linseed
Feeding linseed to dairy cows results in milk fat depression (MFD), but there is a wide range of sensitivity, with some cows not showing any reduction in milk fat, while others having a strong MFD. The objective of this study was to compare the mRNA expression of transcripts expressed in pelleted milk cells in cows resistant or sensitive to MFD. Four cows were selected from a dairy farm after a switch from a control diet to a linseed-rich diet: two were resistant to MFD and had high milk fat content before (4.06 %) and after the change (4.36 %) (R-MFD); and two were sensitive to MFD and milk fat content decreased after the change into the linseed diet (3.56 to 2.54%, S-MFD). Fresh milk samples were collected from each cow the week before and two weeks after the diet change, and transcriptional profiling of mRNA was analyzed by Illumina RNA-sequencing technology. A total of 24,880 transcripts were tested. When S-MFD were fed linseed, 54 transcripts increased mRNA expression by 3 to 23 fold, and 9 transcripts decreased mRNA expression by 3 to 5 fold compared with the same cows fed the control diet. When R-MFD cows were fed linseed, 306 transcripts increased mRNA expression by 2 to 12 fold and 544 transcripts decreased mRNA expression by 2 to 9 fold compared with the same cows fed the control diet. The largest differences were observed between R-MFD and S-MFD cows when fed linseed, where the R-MFD cows increased mRNA expression of 668 transcripts by 2 to 20 fold and decreased mRNA expression of 1161 transcripts by 2 to 81 fold compared with S-MFD cows. When cows were fed the control diet, the R-MFD cows increased mRNA expression of 156 transcripts by 2 to 23 fold and decreased mRNA expression of 740 transcripts by 2 to 42 fold compared with S-MFD cows. When R-MFD cows were compared with S-MFD cows regardless of the diet fed, 91 mRNA transcripts were expressed more, and 460 transcripts were expressed less in R-MFD compared with S-MFD cows. As an example, the gene of the fatty acid binding protein 7 increased mRNA expression by 19 (in the linseed diet) and 20 (in the control) fold in R-MFD compared with S-MFD cows. This preliminary study show the potential of Illumina RNA-sequencing technique to find new candidate genes implicated in MFD.
Keywords: RNA-sequencing, milk fat depression, linseed