Anyone who has experienced asthma understands how difficult rigorous exercise can be. Horses with severe equine asthma (SEA) also struggle with exercise intolerance, often necessitating early retirement or euthanasia. Researchers at the University of Montreal evaluated the impact of submaximal aerobic exercise on airway obstruction during exacerbation of SEA. The researchers hypothesized that low-intensity aerobic activity would induce bronchodilation in these horses. This study represents a first step toward determining whether exercise is safe, well-tolerated, and potentially beneficial in horses with severe equine asthma.
Preliminary Study Phase
The study’s preliminary phase aimed to test feasibility and safety, as well as confirm the onset of bronchodilation in SEA horses after exercise. It included 10 horses, aged 17.5-22.5 years, from a research herd. The horses had been diagnosed with SEA based on historical development of airway obstruction and bronchial inflammation when exposed to hay. Nine weeks prior to the study, the horses were exposed to hay for four weeks to induce exacerbation for another study. Then, they were fed oiled-mixed hay five weeks prior to the study to improve their lung function. The horses were experiencing varying degrees of asthma exacerbation at the time of the study.
The researchers evaluated the horses’ lung function in springtime temperatures before and 15 minutes after exercise. The exercise protocol involved longeing horses for a total of 25 minutes at the walk and trot outside on a dirt or grass paddock. They allowed horses to move at their own pace and did not measure speed.
Researchers administered salbutamol by inhalation immediately after measuring post-exercise lung function; they measured lung function again five minutes after administration (20 minutes after exercise). They also evaluated blood lactates, heart rates, and respiratory rates.
Main Study
Once the preliminary phase proved safe and demonstrated “bronchodilation with exercise in horses in exacerbation,” the researchers added a control model to confirm that bronchodilation occurred due to exercise. The main study began as a crossover design one month after the preliminary phase. Each horse either underwent the same exercise protocol as in the preliminary phase or was turned out for 25 minutes in the same exercise paddock. Following a one-week washout period, the horses reversed roles.
Researchers measured lung function before exercise or turnout and 15 minutes later. Salbutamol was then administered to the turned-out horses only, and lung function was reassessed in both groups five minutes later. This was to compare bronchodilation induced by B2-agonist medication (salbutamol) versus bronchodilation induced by exercise.
In the main study, all eight horses experienced clinical exacerbation of SEA (six of the eight participated in the preliminary study). Three of the eight displayed a cough during exercise.
The results:
- The degree of bronchodilation following exercise was similar to that achieved with B2-agonist inhalation.
- Lung function improvement was comparable to healthy horses, which typically experience a 45-70% reduction in airway resistance following exercise.
The authors summarized: “Exercise-induced bronchodilation occurs even during more chronic exacerbations, and mild-intensity exercise produces a significant bronchodilatory response, which lasts at least 20 minutes after exercise.”
Take-Home Message
Mild exercise (longeing at aerobic paces of their choosing for 25 minutes without tack or rider) can provide bronchodilation in asthmatic horses experiencing exacerbation. The extent of low-intensity-exercise-induced bronchodilation is similar to that achieved with a B2-adrenergic agonist.
This exercise protocol has only been evaluated in a controlled research setting and should not be implemented in horses with severe asthma at this stage. The safety of exercise—particularly repeated exercise—requires further investigation before this approach can be recommended in clinical practice.
Reference
Mainguy-Seers S, Grondin SM, Lavoie JP. Field-applicable low-intensity exercise induces bronchodilation in horses with severe asthma. Equine Veterinary Journal Oct 2025; DOI: 10.1111/evj.70111
Related Reading
- Disease Du Jour: Upper Airway Disorders in Horses
- Positive TW Culture Not Associated With Bacterial Infection in Horses With Asthma
- Research Spotlight: Managing Equine Asthma
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