Low-intensity exercise may briefly ease severe equine asthma
A new Equine Veterinary Journal study suggests that a simple management step, low-intensity exercise performed under field conditions, may briefly improve airway function in horses with severe equine asthma. In the online-ahead-of-print paper, researchers led by Sophie Mainguy-Seers and Jean-Pierre Lavoie reported exercise-induced bronchodilation with a mean approximately 50% reduction in pulmonary resistance after submaximal aerobic exercise, a response described as comparable to bronchodilator therapy. (vettimes.com)
That’s a noteworthy development in a condition where the standard playbook has long centered on environmental antigen avoidance plus corticosteroids and bronchodilators when needed. Severe equine asthma, formerly grouped under terms such as heaves or recurrent airway obstruction, is a chronic inflammatory lower-airway disease strongly linked to inhaled dust, mold, endotoxins, and other barn or forage exposures. Consensus and review literature continue to frame environmental management as the foundation of care, with medication layered on when clinical signs or lung-function impairment warrant it. (pubmed.ncbi.nlm.nih.gov)
The new exercise paper appears to matter because it moves a physiologic observation into a more usable setting. Vet Times, citing the EVJ article, said the exercise was field-applicable and low-intensity, not a laboratory-only protocol, which makes the finding more relevant to ambulatory practice and day-to-day management. If the bronchodilation effect is reproducible and sustained long enough to improve comfort or function, it could offer veterinarians another tool for selected horses, especially where drug use is constrained or pet parent adherence is uneven. Still, the currently available reporting does not establish exercise as a replacement for anti-inflammatory treatment or environmental control. (vettimes.com)
The second recent EVJ paper adds an important note of caution on supportive management. In a prospective crossover study, Université de Montréal investigators fed steamed hay and dry hay for four weeks each to horses with severe equine asthma in remission, with a four-week washout period. Lung resistance at 5 Hz increased over time in both groups, and the study found no significant difference between steamed and dry hay. According to the PubMed abstract, the authors concluded that steamed hay caused a mild but significant deterioration in lung function and inflammation and did not outperform dry hay in preventing exacerbation under the study conditions. (pubmed.ncbi.nlm.nih.gov)
That result cuts against the common assumption that steamed hay is automatically protective in severe equine asthma. It also lands in the middle of a more nuanced evidence base. Earlier work has shown that steaming can reduce respirable particles and, in some settings, improve clinical scores or lung function, while other studies have found inconsistent benefit or only partial improvement compared with alternatives such as pellets, soaked hay, haylage, or broader environmental modification. AAEP educational material likewise emphasizes that reducing respirable dust exposure, not simply choosing one forage-processing method, is the main goal. (pubmed.ncbi.nlm.nih.gov)
Industry and expert commentary available in current coverage reinforces that point. AAEP guidance stresses that environmental management is the mainstay of treatment in equine asthma, including ventilation, bedding choice, forage handling, and minimizing dust in the horse’s breathing zone. Vet Times’ recent equine asthma review also highlighted both of these EVJ papers together, presenting low-intensity exercise as an intriguing non-drug option while noting that the steamed-hay study found mild worsening rather than protection. That combination is useful context for clinicians because it suggests the field is refining, not overturning, the current management hierarchy. (aaep.org)
Why it matters: For veterinary professionals, the practical takeaway is twofold. First, low-intensity exercise may emerge as a helpful adjunct for some horses with severe asthma, potentially offering transient bronchodilation without adding another drug exposure. Second, forage advice may need to be more precise than “feed steamed hay.” Severe equine asthma cases still require individualized plans built around exposure reduction, monitoring, and realistic pet parent compliance. In practice, that means asking not just whether hay is steamed, but how forage is stored, how stalls are ventilated, what bedding is used, whether the horse is indoors for long periods, and whether objective measures such as BALF cytology or lung-function testing are available to assess response. (pubmed.ncbi.nlm.nih.gov)
What to watch: The next steps are likely to focus on duration and repeatability of the exercise effect, which horses benefit most, and whether structured low-intensity exercise can reduce drug use or improve quality of life when paired with standard environmental control. On the nutrition side, expect closer scrutiny of steamed hay protocols, comparisons with pellets and other low-dust forage options, and more emphasis on measuring real-world dust exposure rather than assuming a preparation method will translate into clinical benefit. (vettimes.com)