Identifying ‘chronic stress’ in horses

An important challenge for those working in the animal welfare arena is to identify when animals are being subjected to chronic stress.  Researchers have uncovered a set of variables that may act as an indicator horses are suffering from chronic stress and that intervention is necessary.  The results of a recent scientific study indicate that for horses, low cortisol levels may be cause for concern when accompanied by at least three other symptoms such as ears cocked back more than half the time, anemia and vertebral problems, and may indicate that the horses are suffering adverse effects stemming from chronic stress.

Animal welfare: Potential new indicator of chronic stress in horses

Cortisol, deemed the quintessential stress hormone, allows us to cope with important events and imminent threats. A spike in cortisol levels mobilizes necessary resources — such as by tapping into our body’s reserves to produce energy — and then allows us to return to a stable state. But can our bodies cope with prolonged or repeated stress in the same way? Some studies report lower cortisol levels in humans — or other mammals — subject to chronic stress, while other studies contradict these findings. In light of this, is cortisol still a reliable stress indicator?

To answer this question, researchers from Rennes, France, studied 59 adult horses (44 geldings and 15 mares) from three different riding centers, under their usual living conditions: Horses were kept in individual stalls that are both spatially and socially restrictive and rode by unexperienced equestrians — both potential stressors that, if recurrent, can lead to chronically compromised welfare. The scientists monitored various behavioral and sanitary indicators of the horses’ welfare and measured cortisol levels using blood and stool samples…

Surprisingly, cortisol levels in horses showing signs of compromised welfare (e.g., ears pointed back, back problems, and anemia) were lower than in other horses. These findings are in accord with early observations by the ethology team, which recorded abnormally low cortisol concentrations in horses with depressive-like behavior…

This study demonstrates that…under a certain threshold, low cortisol levels may be cause for concern.


Journal Reference: Jodi Pawluski, Patrick Jego, Séverine Henry, Anaelle Bruchet, Rupert Palme, Caroline Coste, Martine Hausberger. Low plasma cortisol and fecal cortisol metabolite measures as indicators of compromised welfare in domestic horses (Equus caballus). PLOS ONE, 2017; 12 (9): e0182257 DOI: 10.1371/journal.pone.0182257