Abstract
Dairy cattle health, wellbeing and productivity are deeply affected by stress. Its influence on metabolism and immune response is well known, but the underlying epigenetic mechanisms require further investigation. In this study, we compared DNA methylation and gene expression signatures between two dairy cattle populations falling in the high- and low-variant tails of the distribution of milk cortisol concentration (MC), a neuroendocrine marker of stress in dairy cows. Reduced Representation Bisulfite Sequencing was used to obtain a methylation map from blood samples of these animals. The high and low groups exhibited similar amounts of methylated CpGs, while we found differences among non-CpG sites. Significant methylation changes were detected in 248 genes. We also identified significant fold differences in the expression of 324 genes. KEGG and Gene Ontology (GO) analysis showed that genes of both groups act together in several pathways, such as nervous system activity, immune regulatory functions and glucocorticoid metabolism. These preliminary results suggest that, in livestock, cortisol secretion could act as a trigger for epigenetic regulation and that peripheral changes in methylation can provide an insight into central nervous system functions.
Highlights
Dairy animals experience a large variety of stressors that can modify normal behavior and growth, leading to a decrease in productive performances
We investigated the potential regulatory roles of epigenome signatures in the blood of dairy cows falling in the extreme category of the distribution of cortisol concentration in milk
These works suggest that milk cortisol concentration can be considered a valid proxy of blood cortisol.The use of milk cortisol as a biomarker of environmental stimuli in dairy cows was reported by Tsukada et al
Summary
Dairy animals experience a large variety of stressors that can modify normal behavior and growth, leading to a decrease in productive performances. Normal physiological events such as calving, onset of lactation, lactation, weaning and group rearrangement can cause metabolic and environmental conditions which lead to stress, an impairment of animal wellbeing and a consequent decrease in the quality of animal products. Under these stressful conditions, the hypothalamic–pituitary–adrenal (HPA) axis, the autonomic nervous system, and the immune system are called into action to re-establish homeostasis [1]. Since blood sampling is often a source of stress, milk can be viewed as a viable and non-invasive way to measure cortisol levels in lactating cows, as it can be measured without the manipulation of animals
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