Genetic Variation of Hypothalamic-Pituitary-Adrenal Axis Activity in Farm Animals and Beyond

Many experimental data in several species clearly demonstrate the important genetic contribution to variations in HPA axis activity. The influence of corticosteroid hormones on adaptive processes and on production traits such as growth rate, feed efficiency, carcass composition, and meat quality is a strong impetus to the search for the molecular bases of these differences for efficient genetic selection.

Three main sources of genetic variability have been documented so far in farm animal species, the adrenal cortex sensitivity to ACTH-regulating corticosteroid hormone production, the bioavailability of corticosteroid hormones and especially corticosteroid-binding globulin capacity, and glucocorticoid receptor function. The effect of single mutations may be dependent on the genetic background, and genetic variation of cortisol levels may have different functional consequences depending on the molecular mechanisms responsible for this change.

Understanding the genetic basis of HPA axis activity allows the development of genomic tools and breeding technologies aimed at improving adaptive capacity and stress tolerance in farm animals and their use as valuable models for the genetic study of the HPA axis and the correlation with adaptation, metabolism, and other functions regulated by adrenal hormones, and associated pathologies (obesity, cardiovascular, etc.). The next step will be to explore HPA axis variability from a system genetics perspective including the multiple sources of variation and their interactions. This multifactorial approach is a prerequisite to the use of the HPA axis phenotypes in the genetic selection for more productive and robust animals, with a high level of production of quality products.