Low plasma cortisol and fecal cortisol metabolite measures as indicators of compromised welfare in domestic horses (Equus caballus).
Authors: Pawluski Jodi, Jego Patrick, Henry Séverine, Bruchet Anaelle, Palme Rupert, Coste Caroline, Hausberger Martine
Journal: PloS one
Summary
# Editorial Summary Chronic stress in horses produces complex HPA axis responses that don't always follow expected patterns, complicating welfare assessment through cortisol alone. Pawluski and colleagues measured both plasma cortisol and fecal cortisol metabolites (FCM) in 59 horses from three riding centres, correlating these biomarkers against observable welfare indicators including postural abnormalities, spinal pathology, and haematological markers such as anaemia. Horses displaying compromised welfare—characterised by persistent backward ear posture, vertebral problems, or anaemia—demonstrated *lower* rather than elevated cortisol levels in both plasma and faecal samples, challenging the assumption that chronic stress invariably elevates cortisol output. Notably, evening plasma cortisol positively correlated with FCM levels, suggesting that FCM may offer a non-invasive, time-integrated indicator of HPA axis activity where single plasma samples might miss important variations. These findings have significant practical implications: equine professionals should recognise that withdrawn behaviour and postural changes associated with pain or depressive states may occur alongside suppressed rather than elevated cortisol, meaning standard stress markers alone are insufficient for comprehensive welfare evaluation, and multimodal assessment combining behavioural observation, clinical examination, and FCM sampling may provide more reliable welfare assessment than relying on cortisol concentrations in isolation.
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Practical Takeaways
- •Monitor for low cortisol (both plasma and fecal measures) as a potential red flag for welfare problems—don't assume stressed horses always have high cortisol; chronic stress may suppress it
- •Behavioral signs (ears back, withdrawn posture) combined with physical findings (vertebral issues, anemia) warrant investigation of underlying chronic pain or environmental stressors
- •Fecal cortisol metabolite sampling offers a non-invasive way to assess welfare status and could be useful for tracking horses suspected of chronic stress or pain over time
Key Findings
- •Horses with compromised welfare (unusual ear position, vertebral problems, anaemia) showed lower plasma cortisol and fecal cortisol metabolite (FCM) levels than healthy horses
- •Evening plasma cortisol levels positively correlated with FCM levels, suggesting FCM may reliably reflect systemic cortisol status
- •Withdrawn postures and depressive-like behavior were associated with lower plasma cortisol levels
- •Low cortisol levels, rather than elevated levels, may indicate chronic stress and welfare compromise in domestic horses