Effects of simple environmental enrichment on the welfare of stabled horses

Fargo with a jolly ball during research on horse welfare and enrichment 
tools to improve behaviour,healtth and welfare of stabled horses.
(Jael Mackendorf / UC Davis)

Horses evolved to move and forage for much of the day, yet many domesticated horses spend most of their time confined to stalls with limited opportunities for grazing or exploration. This mismatch between natural behaviour and management practices is associated with a range of welfare concerns, including frustration-related behaviours, gastric ulcers, and compromised musculoskeletal health. Recent research from the University of California, Davis, published in the journal Animals, provides evidence that simple, low-cost enrichment strategies can help address these issues in stabled horses.

The study investigated whether common enrichment items (hay feeders, large rubber activity balls, and shatter-proof mirrors) could influence both behaviour and physiological indicators of arousal in competition horses. The work was led by Miranda Brauns during her master’s studies in animal biology at UC Davis, under the supervision of Dr. Amy McLean in the Department of Animal Science and involved collaboration with the UC Davis Intercollegiate Equestrian Team. Ahmed Ali at Clemson University and Jeannine Berger at Sacramento Veterinary Behavior Services also contributed to this research.

The researchers worked with nine stabled American Quarter Horses and American Paint Horses housed at the UC Davis Equestrian Center. Horses were kept in individual stalls within an open-air barn but received daily exercise, including approximately 90 minutes of training and 30 minutes of turnout. Despite this routine, the horses still spent a large proportion of the day confined, particularly between feeding and exercise periods - times when boredom and frustration are likely to peak.

Enrichment items used for the hay feeder, activity ball, and mirror treatments.(c) Brauns et al 

Each horse was fitted with a smart halter capable of continuously recording heart rate and respiration rate, providing insight into physiological arousal and emotional state. Over a four-week period, enrichment items were introduced four times daily in randomised trials. Each session lasted 30 minutes, after which the item was removed. Between different enrichment types, a five-day washout period was used to reduce carryover effects. In total, researchers and student volunteers collected and reviewed around 720 hours of video footage, scoring behaviours such as grazing, locomotion, and frustration-related actions (e.g. stomping, kicking, and tail swishing).

The results showed that enrichment had clear and measurable effects on horse behaviour. Across all item types, horses spent more time engaging in foraging-like behaviours and locomotor movement and showed significant reductions in frustration behaviours compared with control periods without enrichment. These changes were most pronounced during midday and afternoon sessions (around 12:00 and 16:00), when horses did not normally receive feed. This finding suggests that enrichment is particularly valuable during periods of low stimulation between routine meals and exercise.

Physiological data supported the behavioural observations. Enrichment increased heart rate relative to control conditions, indicating heightened arousal and engagement, though respiration rate was not affected. Importantly, the increased heart rate was interpreted not as stress, but as a sign of positive stimulation, especially when accompanied by reduced frustration behaviours. Among the enrichment types, hay feeders produced the strongest overall effects, resulting in activity patterns most like those seen in free-ranging horses. This aligns with the species’ strong motivation to forage for many hours a day. Activity balls also promoted interaction and movement, while mirrors elicited mixed responses: geldings tended to show more interest, whereas mares were more likely to avoid them. Mirrors were also associated with lower evening heart rates compared with other times of day, suggesting a calming effect in some contexts.

From an applied perspective, the findings highlight the potential for simple enrichment tools to improve equine welfare without major changes to housing systems. By providing enrichment, particularly forage-based options, during times when horses are otherwise inactive, owners and managers may reduce boredom-related behaviours and support both mental and physical health. The authors emphasise that enrichment does not replace turnout or exercise but serves as an important additional management tool.

While the study involved a relatively small number of horses and short-term trials, it reinforces the importance of aligning management practices with species-typical behaviours and suggests that even modest interventions can have meaningful welfare benefits. Further research with larger populations and longer time frames will be needed to assess long-term impacts and refine recommendations for different enrichment types.

For more details, see: 

Brauns, Miranda, Ahmed Ali, Jeannine Berger, and Amy McLean. 

Physiological and Behavioral Responses of Stabled Horses (Equus caballus) to Three Types of Environmental Enrichment

Animals (2025) 15, no. 19: 2779. 

https://doi.org/10.3390/ani15192779