Beyond Glucocorticoids: Integrating Dehydroepiandrosterone (DHEA) into Animal Welfare Research

Simple Summary It is considered best practice in the field of animal welfare to utilize multiple indicators of welfare when assessing an individual’s current state. While welfare scientists have traditionally relied on glucocorticoids to gain insight into an animal’s physiological condition, there are limitations to relying solely on these biomarkers. Fortunately, other biomarkers, such as dehydroepiandrosterone and its sulfate ester—collectively referred to as DHEA(S)—help provide a more complete picture of hypothalamic–pituitary–adrenal (HPA) axis activity and functionality. There is evidence that the ratio of glucocorticoids:DHEA(S) may serve as an indicator of immune function, mental health, cognitive performance and overall welfare. The current review highlights studies that have utilized the ratio of glucocorticoids:DHEA(S), outlines methodological considerations and discusses how the ratio can best be applied to assess animal welfare. Abstract Animal welfare researchers are committed to identifying novel measures for enhancing the quality of life of individual animals. Recently, welfare scientists have emphasized the need for tracking multiple indicators of an animal’s behavioral, emotional and mental health. Researchers are currently focused on integrating non-invasive physiological biomarkers to gain insight into an individual’s welfare status. Most commonly, the animal welfare community has analyzed glucocorticoid hormones and their metabolites as a measure of stress. While glucocorticoids provide valuable information about hypothalamic–pituitary–adrenal (HPA) axis activity, there are limitations to utilizing these hormones as the sole measure of long-term stress and welfare. Other biomarkers, such as dehydroepiandrosterone and its sulfate ester—collectively referred to as DHEA(S)—help provide a more complete picture of HPA activity. DHEA(S) counteracts the effects glucocorticoids by having anti-aging, immune-enhancing and neuroprotective properties. Recent studies have examined the ratio of glucocorticoids to DHEA(S) as a way to better understand how the HPA axis is functioning. There is evidence that this ratio serves as an indicator of immune function, mental health, cognitive performance and overall welfare. We review studies that employed the glucocorticoid:DHEA(S) ratio, outline methodological considerations and discuss how researchers can integrate glucocorticoids, DHEA(S) and the glucocorticoid:DHEA(S) ratio into welfare assessments.