Assessment of stress in dogs through cortisol measurement: From a physiological indicator to a welfare biomarker

Abstract

Stressors of varying intensity are an integral part of dogs' lives and may affect their behaviour, health status and overall welfare. Activation of the hypothalamicpituitary-adrenal (HPA) axis leads to increased cortisol secretion, making cortisol one of the most widely used physiological indicators of the stress response. Cortisol can be measured in a range of biological samples, including blood, saliva, urine, faeces and hair, each providing insight into different aspects of stress-related physiological activity. Alterations in cortisol concentrations may occur in dogs exposed to a wide range of situations, including shelter housing, transportation, veterinary procedures, environmental changes, sporting activities and participation in dog shows. At the same time, substantial inter-individual variation in the magnitude of the response may be observed even among dogs exposed to comparable environmental conditions. The observed variation may reflect the combined effects of environmental influences, physiological status and genetic background. Hair cortisol analysis has gained interest as an indicator of long-term stress exposure because it reflects HPA axis activity over extended periods. In contrast, salivary cortisol determination represents a practical and non-invasive method for assessing acute responses to specific stimuli. Blood cortisol measurement allows the assessment of short-term changes in cortisol concentrations, although the sampling procedure itself may influence the animal's stress response. Urinary and faecal cortisol measurements provide a broader, time-delayed insight into glucocorticoid excretion and metabolism and may therefore be useful for assessing cumulative stress responses. The complementary information contained in different biological samples enables a broader assessment of the stress response, particularly when physiological measures are interpreted alongside behavioural indicators. In addition, research has begun to examine genetic factors that may influence individual stress responsiveness, particularly NR3C1 gene, which encodes the glucocorticoid receptor. Understanding the relationships between cortisol concentrations, stress responsiveness and genetic background could facilitate the identification of more reliable welfare biomarkers, improve welfare assessment in dogs and support more individualized management and care of dogs exposed to diverse environmental and social challenges.