Abstract
It is challenging to measure long-term endocrine stress responses in animals. We investigated whether cortisol extracted from dog hair reflected the levels of activity and stress long-term, during weeks and months. Hair samples from in total 59 German shepherds were analysed. Samples for measuring cortisol concentrations were collected at three occasions and we complemented the data with individual scores from the Canine Behavioural Assessment and Research Questionnaire (C-BARQ). Generalised linear mixed model (GLMM) results showed that hair cortisol varied with season and lifestyle: competition dogs had higher levels than companion, and professional working dogs, and levels were higher in January than in May and September. In addition, a positive correlation was found between the cortisol levels and the C-BARQ score for stranger-directed aggression (r = 0.31, P = 0.036). Interestingly, the factor “playing often with the dog” (r = −0.34, P = 0.019) and “reward with a treat/toy when the dog behaves correctly” (r = −0.37, P = 0.010) correlated negatively with cortisol levels, suggesting that positive human interactions reduce stress. In conclusion, hair cortisol is a promising method for revealing the activity of the HPA-axis over a longer period of time, and human interactions influence the cortisol level in dogs.
Highlights
It is challenging to measure long-term endocrine stress responses in animals
Samples for measuring cortisol concentrations were collected at three occasions and we complemented the data with individual scores from the Canine Behavioural Assessment and Research Questionnaire (C-BARQ)
Generalised linear mixed model (GLMM) results showed that hair cortisol varied with season and lifestyle: competition dogs had higher levels than companion, and professional working dogs, and levels were higher in January than in May and September
Summary
It is challenging to measure long-term endocrine stress responses in animals. We investigated whether cortisol extracted from dog hair reflected the levels of activity and stress long-term, during weeks and months. Results suggest habituation to novel and potential stressful situations, since the cortisol levels were negatively correlated with dog park visit frequency[5]. Since cortisol levels in blood and saliva correlate well[7], non-invasive saliva sampling has become a useful method to avoid additional stress due to sampling Both cortisol in blood and saliva reflect a momentary measurement in real time and to measure long-term cortisol secretion, indicating possible long-term stress, multiple samples are needed. A promising non-invasive method to study prolonged changes in the HPA-axis activity is to measure cortisol incorporated in hair[10,11,12,13,14,15]. It is likely that this is the case in hair cortisol even though, to our knowledge, there is no study confirming this
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