Veterinary: Hair of the dog – testing stress levels in shelter dogs

Testing cortisol levels in hair samples could be an effective method for measuring long-term stress in shelter dogs, reports a paper published in Scientific Reports. The findings suggest that hair sampling appears to be a useful additional tool in monitoring dog welfare and for welfare research.

Dogs can suffer from chronic stress in environments such as shelters, which can lead to long-term medical and behavioural problems. A common approach for testing stress is by measuring levels of the hormone cortisol in the blood or urine. However, these methods can be invasive and only indicate stress levels at a specific time, rather than long-term.

Janneke van der Laan and colleagues investigated whether sampling hair cortisol concentration (HCC) – a non-invasive technique – would be an accurate biomarker for long-term cortisol levels in shelter dogs. They measured HCC in 52 dogs (18 female and 34 male) admitted to an animal shelter in the Netherlands between October 2018 and August 2019. Dogs displaying high anxiety or aggressive behaviour were excluded from the study. Hair samples were taken during admittance to the shelter, after 6 weeks in the shelter, 6 weeks after adoption, and 6 months after adoption. A shave/re-shave protocol was used, where a bald spot was shaved or cut to allow a re-shave of newly grown hair after the period of interest. Urine samples were also taken on five occasions both during their time in the shelter and after adoption. A single hair sample was also taken from a control group of 20 non-shelter pet dogs.

There were no significant differences in HCC between shelter dogs at intake compared to the control group. The authors report that, for shelter dogs, HCC after 6 weeks in the shelter were significantly higher than when the dogs had entered the shelter. However, HCC in both post-adoption samples were not significantly higher than at shelter intake. There was a significant but moderate positive correlation between HCC and urinary cortisol levels in shelter dogs, suggesting that HCC represents a valid biomarker for cortisol and therefore stress in dogs. The authors add that further research on HCC is needed in larger sample sizes including a broad range of dog breeds with different hair types.