Transcriptome Profile in Dairy Cows Resistant or Sensitive to Milk Fat Depression

SIMPLE SUMMARY: In the last 20 years, there has been interest in modifying this fatty acid profile to increase the content in polyunsaturated fatty acids which are healthier for human health. However, long chain polyunsaturated fatty acids cause milk fat depression. We observed a wide variation in the sensitivity of cows to induced milk fat depression caused by feeding on linseed-rich diets. We identified 15 genes as key gene regulators harboring SNP in cows fed the linseed-rich diet. The selected genes are novel candidates to be involved in the resistance or sensitivity of dairy cows to milk fat depression, and open the opportunity to select cows genetically resistant to milk fat depression. ABSTRACT: Feeding linseed to dairy cows results in milk fat depression (MFD), but there is a wide range of sensitivity among cows. The objectives of this study were to identify target genes containing SNP that may play a key role in the regulation of milk fat synthesis 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 with a high milk fat content in the control (4.06%) and linseed-rich (3.90%) diets; and two were sensitive to MFD with the milk fat content decreasing after the change from the control (3.87%) to linseed-rich (2.52%) diets. Transcriptome and SNP discovery analyses were performed using RNA-sequencing technology. There was a large number of differentially expressed genes in the control (n = 1316) and linseed-rich (n = 1888) diets. Of these, 15 genes were detected as key gene regulators and harboring SNP in the linseed-rich diet. The selected genes MTOR, PDPK1, EREG, NOTCH1, ZNF217 and TGFB3 may form a network with a principal axis PI3K/Akt/MTOR/SREBP1 involved in milk fat synthesis and in the response to diets that induced MFD. These 15 genes are novel candidate genes to be involved in the resistance or sensitivity of dairy cows to milk fat depression.