Hair cortisol in horses ( Equus caballus ) in relation to management regimes, personality, and breed

Hair cortisol is a promising biomarker to measure long-term stress because cortisol is incorporated into the hair shaft as it grows. However, few studies have previously assessed hair cortisol concentrations (HCCs) in horses. In this study, HCC was evaluated in both mane hair from the neck and body hair from the withers in 153 horses of different breeds, from seven different stables with three different management regimes (free-roaming horses, riding school horses, trotter horses). In addition, 4 hours of behavioral observations were performed at each stable, and for 43 of the horses, a personality survey was completed. Mane and withers HCC correlated moderately, but significantly (rs = 0.48, P < 0.001). Differences between the stables were found for both mane and withers hair (both P < 0.01) and the stable with lowest HCC also showed highest occurrences of positive social and resting behaviors (both P < 0.01). There were no significant differences in HCC between the management regimes although free-roaming horses showed less negative social behavior compared to riding school horses (P = 0.041) and trotter horses (P = 0.055). The personality traits “dominance, anxiousness, and excitability” revealed weak to moderate correlations with mane HCC (rs = −0.34, P = 0.027; rs = −0.46, P = 0.002; rs = −0.31, P = 0.043, respectively), which might suggest that personality could also be related to long-term stress levels in horses. © 2020 Elsevier Inc.