Single-confinement housing can pose welfare risks to domestic horses. This study investigated horses’ stress responses when confined to single stalls in different stable designs in a tropical savanna region to address a gap in the literature. In total, 23 horses were assigned to a stable with a central corridor and solid external walls (A) (N = 8), a stable with one side corridor and solid external walls (B) (N = 6), or a stable with a central corridor and no solid external walls (C) (N = 9). Air velocity, relative humidity, air temperature, and noxious gases were measured inside the stables, and the heart rate and HRV of the horses were also determined. The relative humidity was lower in stable C than in stable A (p < 0.05), while the air temperature was higher in stable C than in stable B (p < 0.05) during the day. The airflow and ammonia levels were higher in stable C than in stables B and A (p < 0.01–0.0001). Overall, horses’ HRV in stable A was lower than in those in stables B and C (p < 0.05–0.01). Horses in stable A tended to experience more stress than those in other stables.

The physiological capabilities of horses begin to decline after they reach 15 years of age. However, some exceptionally talented horses can continue their sports careers beyond this age, raising concerns about their welfare. This study investigated animal welfare by observing resting heart rate (HR) and heart rate variability (HRV) metrics in geriatric horses participating in similar training or physical activities compared to younger adult horses over 30 min periods. Forty-six horses of varying ages and activity levels were divided into four groups, including horses under 15 years practising structured training for dressage (AL-1; N = 13) and school riding (AL-2; N = 13) and horses aged between 15 and 20 years participating in AL-1 (N = 10) and AL-2 (N = 10). In adult horses, the HR decreased in those performing AL-1, which was observed alongside an increased RR interval compared to those participating in AL-2 (p < 0.05 for both). Meanwhile, HRV increased in adult horses (measured by pNN50) but decreased in geriatric horses (measured by SDANN, SDNNI, DC, and SD2) participating in AL-1 when compared to their counterparts in AL-2 (p < 0.05 for all). Adult horses exhibited better autonomic regulation while engaged in structured dressage training than geriatric horses. These findings underscore the necessity for the careful management of physical activities to ensure the well-being of all horses, particularly older ones.

Changes in resting heart rate (HR) and HR variability (HRV) are utilised to assess training effects in horses. However, limited research has examined how these variables reflect training effects during exercise sessions and recovery periods, particularly in horses of different ages. This study investigated how HR and HRV changed during exercise sessions and recovery periods in untrained adult horses (UAHs; n = 9) and geriatric horses (UGHs; n = 9). HR and HRV were measured before and during a 54 min exercise bout over a 12-week training programme. Mixed-effects model with Greenhouse–Geisser correction was used for statistical analysis. The duration of elevated mean HR, sympathetic nervous system index, and stress index during the exercise sessions gradually decreased over the 12 weeks for both UAHs and UGHs. However, this decrease was faster in UAHs than in UGHs. Mean HR consistently decreased during the exercise sessions for both UAHs and UGHs over the 12 weeks. Furthermore, HRV returned to baseline faster in UAHs than in UGHs during the exercise bouts. These results indicate that the 12-week structured exercise programme positively influenced HR and HRV adaptation during exercise and recovery periods in UAHs and UGHs, with the adaptations differing dynamically between them.

Horses competing in eventing competitions encounter significant challenges that increase their risk of severe injuries and metabolic disorders. Numerous studies have focused on the risk of such injuries and disorders during the cross-country segment. While one study has examined autonomic responses during this segment, research on these responses across all three phases of competition, particularly during one-day events, is still limited. The objective of this study was to analyse the autonomic responses of horses by measuring heart rate (HR) and heart rate variability (HRV) during three exercise tests and their recovery while competing in the Fédération Équestre Internationale Eventing World Challenge. HR and HRV were monitored in 10 horses during the competition; however, data were collected from only nine horses, as one was eliminated. Beat-to-beat (RR) interval decreased from control (1742 ± 202.3 ms) during dressage (D), jumping (J) and cross-country (CC) tests, lasting 60 min after cross-country (60-CC) (D: 594.6 ± 40.2 ms, J: 420.6 ± 94.5 ms, CC: 358.0 ± 66.9 ms and 60-CC: 1424.2 ± 98.3 ms vs. control: 1742.0 ± 202.3 ms, p < 0.05–0.001). HR increased during the exercise tests, extending to 60-CC (D: 101.4 ± 7.0 beats/min, J: 148.2 ± 30.5 beats/min, CC: 172.0 ± 27.0 beats/min and 60-CC: 42.2 ± 3.0 beats/min vs. control: 34.8 ± 3.7 beats/min, p < 0.05–0.001). Various HRV metrics were lower during J than D, including standard deviation of normal-to-normal RR interval (D: 25.4 ± 9.1 ms vs. J: 9.8 ± 6.2 ms, p < 0.01), total power band (D: 512.4 ± 261 ms2 vs. J: 126.8 ± 180.4 ms2, p < 0.05) and standard deviation 2 (D: 35.0 ± 12.5 ms vs. J: 13.4 ± 8.9 ms, p < 0.01). Changes in the parasympathetic and sympathetic nervous system indices corresponded with RR interval and HR modifications, respectively. The study found that autonomic responses were significantly pronounced during three exercise tests, with notably stronger reactions observed during the jumping and cross-country segments of the Eventing World Challenge. This preliminary study provides valuable insight into the autonomic regulation of horses during these phases of one-day eventing competitions.

Long-distance road transport is known to be stressful for horses, with most research conducted in temperate climates. This study investigated horses’ stress responses during long-distance transport before and after a jumping competition in a tropical environment. Ten healthy horses (aged 7.9 ± 1.9 yr) were studied. Blood cortisol concentrations, hematology, and heart rate (HR) variability (HRV) were monitored during outbound (OTJ) and inbound journeys (INJ). Cortisol concentrations increased 5 min after unloading and remained elevated for up to 180 min in the OTJ (P < 0.05 to 0.001); during the INJ, levels returned to baseline and remained stable after 60 min (P < 0.01 to 0.001). White blood cell and neutrophil counts were higher in the OTJ than the INJ in the 60 to 180 min after unloading (P < 0.05). Beat-to-beat (RR) intervals decreased during 120 min of transport (P < 0.05 to 0.0001) and 60 min after unloading (P < 0.05) in OTJ and INJ. Parasympathetic nervous system index decreased over 30 min during travel (P < 0.01) and 30 min after unloading (P < 0.05) in OTJ, while slightly decreasing at 60 to 90 min into the INJ. HR and sympathetic nervous system (SNS) index increased at 30 to 60 min during travel (P < 0.05 to 0.0001) and 30 min after unloading (P < 0.001) in the OTJ, while they increased at 60 to 90 min during travel in the INJ. The standard deviation of the averages of RR intervals in 5-min segments (SDANN) and the mean of the standard deviations of RR intervals in 5-min segments (SDNNI) showed greater values during the OTJ than the INJ 330 to 360 min after unloading (P < 0.01 to 0.001). Stress index increased at 30 to 120 min of travel in both the OTJ and INJ (P < 0.05 to 0.001). High-frequency (HF) band power increased, with a concurrent decrease in the low-frequency (LF) band and LF/HF ratio at 90 to 440 min of travel (P < 0.05 to 0.0001 for all variables). The standard deviation 2/standard deviation 1 ratio was reduced at 120 to 600 min of travel (P < 0.05 to 0.0001). Correlations between environmental parameters and HRV variables were mainly observed during the INJ. In summary, horses primarily experienced stress during the initial hours of travel and immediately after unloading. Stress responses differed between journeys and were partly influenced by environments and housing conditions. This study highlights welfare considerations concerning horse transport for equestrian events in tropical climates.

Single-confinement housing can pose welfare risks to domestic horses. This study investigated horses’ stress responses when confined to single stalls in different stable designs in a tropical savanna region to address a literature gap. In total, 23 horses were assigned to a stable with a central corridor and solid external walls (A) (N = 8), a stable with one side corridor and solid external walls (B) (N = 6) or a stable with a central corridor and no solid external walls (C) (N = 9). Air velocity, relative humidity, air temperature and noxious gases were measured inside the stables, and the heart rate and HRV of the horses were also determined. The relative humidity was lower in stable C than in stable A (p < 0.05), while the air temperature was higher in stable C than in stable B (p < 0.05) during the day. The airflow and ammonia levels were higher in stable C than in stables B and A (p < 0.01–0.0001). Overall, horses’ HRV in stable A was lower than in those in stables B and C (p < 0.05-0.01). Horses in stable A tended to experience more stress than those in other stables.