Factors Affecting Hair Cortisol Concentration in Domestic Dogs: A Focus on Factors Related to Dogs and Their Guardians

Considering the controversial findings in the existing literature, this study aimed to deepen the knowledge about Hair Cortisol Concentration (HCC) in dogs by evaluating the influence on HCC of some factors related to dogs and guardians. Hair was collected from two groups: 128 Healthy Dogs (HD) and 25 dogs with a primary Chronic Gastroenteric Disease (CGD). Guardians of HD filled in a questionnaire, including dogs and respondents' demographic information, and the perceived welfare and behaviour of the dog. HCC were measured with an enzyme immunoassay kit. A Wilcoxon rank-sum test was conducted to compare HCC in HD and CGD. For HD, a multiple linear regression and an ordinary logistic regression were performed with the dependent variable being HCC and the independent variables being dog and guardian characteristics and the questionnaire evaluations. HCC was statistically lower in CGD (medians: 4.79 versus 6.41 pg cortisol/mg hair; W = 961, <i>p</i> < 0.001). A positive association between HCC and guardian's age was found (β: 0.012; t-value = 3.205; <i>p</i> < 0.01). Previous literature has shown that several factors can affect HCC in dogs; however, given the controversial results, a large sample and a multiparametric analysis, as in this study, can advance knowledge and highlight newly investigated factors. This study revealed the importance of also considering factors related to the guardian and the possibility that multiple factors interact and collectively influence HCC.