Equine asthma is marked by airway inflammation and can cause clinical signs ranging from occasional coughing to overt labored breathing. | Shelley PaulsonEquine asthma is a chronic inflammatory respiratory disease in horses marked by airway inflammation, bronchial hyperresponsiveness, and in advanced cases, airway remodeling, or a progressive thickening and damage of the airway walls.Horses can develop two types of equine asthma: mildmoderate (MEA), which often presents as exercise intolerance and an occasional cough, and severe asthma (SEA), which causes overt labored breathing at rest.Clinical signs of MEA often surface subtly and get missed until the horses condition worsens. Therefore, early detection plays a critical role once you suspect your horse has MEA.Researchers on a recent study, including Kelsey Hart, DVM, PhD, Dipl. ACVIM, professor at the University of Georgias College of Veterinary Medicine, in Athens, examined whether polyphenols, a nutritional intervention, could shift airway inflammation in horses with asthmaa novel adjunctive approach beyond environmental management and pharmaceutical use.Studying Polyphenols for Horse With AsthmaIn the first part of their study, the researchers examined eight healthy horses and 10 horses with equine asthma over a six-to-eight-week period to determine whether a dietary supplement containing mixed polyphenols (naturally occurring micronutrients with powerful antioxidant and anti-inflammatory properties) could reduce equine airway and systemic inflammation (as measured in the horses blood).In the second part, the researchers randomly assigned five asthmatic horses to either a polyphenol supplement or a control group (no supplement). They fed the horses in both groups a low-dust diet for four weeks, followed by four weeks of dusty hay to exacerbate airway inflammation.The team measured outcomes through inflammatory markers in the lungs via bronchoalveolar lavage (BAL) and in systemic circulation via blood tests.Effects of Polyphenol Supplementation on Equine AsthmaSupplementation with mixed polyphenols reduced several markers of airway inflammation in asthmatic horses in the first part of the study compared to the nonsupplemented control group. Specifically, the percentage of neutrophils and the concentration of interleukin-6, both of which indicate inflammation, were decreased in fluid obtained from the horses lungs via bronchoalveolar lavage (BAL).In the healthy horse group, supplementation produced less dramatic effects (because baseline inflammation was already low), but the researchers still observed trends toward lower inflammation levels.When to Consider Polyphenol SupplementationIf your horse shows mild signs of poor performance, an occasional cough, or has a history of airway inflammation, talk with your veterinarian about using a supplement such as mixed polyphenols. However, supplementation does not replace core environmental management (dust control, ventilation, hay quality) or any necessary medical interventions (e.g., corticosteroids).Take-Home MessageThe researchers findings suggest that polyphenol supplementation can be beneficial for horses with mild-to-moderate equine asthma by reducing airway inflammation in conjunction with good environmental management and might be a beneficial adjunct to the management of some horses with asthma. However, to best improve equine respiratory health and performance, a holistic approach that considers adequate barn management practices and nutrition remains vital.The study, Effects of mixed polyphenol supplementation on lower airway inflammation in horses with Equine Asthma Syndrome, appeared in the Journal of Equine Veterinary Science in November, 2025.