Social interaction in horses can impact long term stress levels

Cortisol is a hormone secreted in humans and animals when stressed. The hormone can be a life saver in dangerous situations but in long term situations it can be destructive. When testing the cortisol levels in hair samples from horses, researchers found a connection between stress and the social life of the horses.

Lina Roth was surprised by the findings that management regime did not have an effect on the cortisol secretion.  Anna Nilsen

A research team at Linköping University has studied how stress can be measured through hair samples from horses. The samples where collected from the horse’s body hair and mane. The samples were then analyzed for cortisol levels. This is a method already proven effective on humans and dogs and in this study, led by Lina Roth, the results prove that the method is effective in horses too.

– By measuring cortisol levels, we have been able to study the horses stress levels for a longer time, Lina Roth says.

In this study, the researchers cut hair from the side of the horse and, also, took samples from the mane, on a total of 153 horses. The results of both the samples correlated, which indicates that the method is valid.

– Now, we need a standardized method for testing. The mane is more homogeneous in different horse races than the fur is. Also, the sample needs to be cut really close to the skin of the horse which can be frightening to them if you use the clipper on the body, says Lina Roth.

Universitetslektor Lina Roth forskar om djurs beteende, välfärd och sinnesförmågor. Photo credit Anna NilsenSeven different stables participated in the study. They were compared separately and compared in groups, based on the management regimes of the stable, free-roaming horses, riding school horses and trotter horses.

We thought there would be a difference in cortisol levels between the different management regimes, but it wasn’t, says Lina Roth.

However, there was a difference in social interactions between the horses. During the same time frame that the samples were collected, the research team studied the behavior of the horses. The results show that the free-roaming horses were behaving nicer towards each other, with less negative social interactions.  

– There were fewer negative encounters there, like threatening behavior, kicks and biting, between the free-roaming horses, were their lifestyle is closer to their natural behavior.  

 Even though the research team didn´t find a difference in cortisol levels between management regimes, there were noted differences between the stables, which impacted the horse’s social lives. – The stable with the lowest hair cortisol levels also had the most positive interactions.

The results of the study open new interesting areas for Lina Roth and the research team. If the management regimes don´t influence the stress levels, maybe the humans around them do.

– Going forward, that would be interesting to study. Could it possibly be that humans surrounding the horses have an effect. We already showed, in earlier research, that dogs reach the same long-term stress levels as their owners, says Lina Roth.

Artikel: Hair cortisol in horses (Equus caballus) in relation to management regimes, personality and breed Mathilde Sauveroche, Josefine Henriksson, Elvar Theodorsson, Ann-Charlotte B. Svensson Holm, Lina Roth (2020) Journal of Veterinary Behavior, Publicerad online den 27 februari 2020,DOI: 10.1016/j.jveb.2019.12.002

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