Gene expression profiles in cows subjected to different stress level as assessed by cortisol in milk

To assess how different levels of stress exposure affect gene regulation mechanisms in cattle, we investigated gene expression in 13 Italian Red Pied dairy cows falling in the high- and low-variant tails of the distribution of milk cortisol concentration (MC), a neuroendocrine biomarker of stress in dairy cows, measured in 126 animals belonging to the same farm in the framework of the Gen2Phen Italian project. The ‘low-’ and ‘high-cortisol’ groups of animals had MC<370 pg/ml and>810 pg/ml, respectively. To date, 13 animals (6 low- and 7 high-MC) have been sequenced. We detected significant fold differences in the expression of 324 genes. KEGG and Gene Ontology (GO) pathway analyses indicated that these genes were mainly involved in immune regulatory pathways, glucocorticoids metabolism and nervous system functions. Cows were ranked on the basis of cortisol in the milk and the 10 cows with the higher and the 10 cows with the lower concentrations were selected for transcriptome analysis.