Background: Resting behaviors and stress parameters in hospitalized horses remain poorly characterized.
Objectives: To compare recumbency duration, salivary cortisol, and heart rate variability (HRV) in healthy horses across two hospital stall environments and their home environment. Animals: Six healthy mares from a teaching herd.
Methods: A case-control study in which each horse served as its own control. Horses were monitored for three days at home before spending three days in each of the two hospital stalls: HS-1 (standard indoor stall) and HS-2 (outdoor-facing stall with reduced monitoring, added exercise, and nighttime darkness). Recumbency was recorded, salivary cortisol was measured by ELISA, and HRV (SDNN and RMSSD) was assessed via ECG. A mixed-effects model evaluated environment and day as fixed effects, with horse as a random effect. Pairwise comparisons were adjusted for multiple testing.
Results: Recumbency decreased in both hospital environments (HS-1: -99.3 min, p = 0.02; HS-2: -92.9 min, p = 0.03). Salivary cortisol increased in both hospital environments (HS-1: +0.04 µg/dL, p = 0.02: HS-2: +0.08 µg/dL, p < 0.01). HRV parameters increased in both hospital settings (HS-1 SDNN: +0.04, p = 0.01; HS-1 RMSSD +0.04, p < 0.01; HS-2 SDNN: +0.07, p < 0.01; HS-2 RMSSD: +0.04, p < 0.01). No significant differences were found between HS-1 and HS-2. Conclusions and Clinical Importance: Hospitalization increased cortisol and reduced recumbency duration, indicating higher stress and decreased resting behavior. Unexpected HRV increases warrant further study. Environmental modifications in HS-2 did not mitigate these effects.
