Q. I live in California where our air quality has been poor due to wildfire smoke. I’ve been wearing an N95 mask (a respiratory device that eliminates 95% of very small particles) when outside doing barn chores, but my horse is living outside and breathing the air with no filtration system. I haven’t ridden for more than two weeks. Now that we’ve had rain, the air quality is much better, and I am planning on putting my horse back in work. I’m worried about his lung health though. Is there a supplement that might help?
A. Protecting lung health is vital to equine performance, so you were wise not to work your horse in poor-quality air. Equine lung performance isn’t greatly altered by conditioning the way that the other systems of the horse can be improved (i.e., the cardiovascular and musculoskeletal systems). Therefore, any damage to lung tissue can have a lasting effect on lung health and future performance ability.
I would strongly recommend that, before putting your horse back to work, you contact your veterinarian for guidance. At the end of 2017 the University of California Davis School of Veterinary Medicine published some guidelines for horses exposed to wildfire smoke, which state that airway damage resulting from smoke can take four to six weeks to heal and that ideally horses should not return to work for this amount of time after smoke has cleared. Obviously, this will depend on how severe the air pollution was where your horse lives. Your veterinarian should be able to guide you as to how long is appropriate to give your horse before retuning him to work.
You can certainly help limit further lung irritation. For example, consider wetting all feed to reduce dust inhalation and using low-dust bedding. There is limited research in horses looking at what supplement ingredients might support lung health. Typically supplements marketed to support lung health contain a combination of ingredients including, omega-3 fatty acids, vitamin C, MSM, quercitin, superoxide
Omega-3 fatty acids, in particular DHA, have been shown to have positive effects in human patients with asthma. Several compounds known as proresolving mediators appear to be generated from omega-3 fatty acids. These mediators promote the resolution of eosinophilic inflammation (eosinophils are oxidant-sensitive cells considered to be key effectors in allergic inflammation) in the airways. Research in horses has shown that a supplement containing DHA improved chronic lower airway inflammatory diseases in the study horses.
N-acetyl cysteine (NAC) also influences eosinophils. In test-tube research using human eosinophils, NAC inhibited eosinophil functions, which in lung tissue could have a positive impact in mediating eosinophil-related inflammation.
Quercitin is a flavonol that occurs naturally in many vegetables. As an antioxidant it scavenges free radicals preventing them from causing damage to tissue. Based on work in test tubes, scientists also believe it has anti-allergic properties in part due to its ability to inhibit histamine production as well as the release of pro-inflammatory cytokines. Data on quercitin and its impact on respiratory allergies is preliminary, and more work is needed to determine its true impact.
Doctors believe an imbalance between oxidants and antioxidants is partly to blame for the onset and progression of chronic obstructive pulmonary disease (COPD) in people. Vitamin C and superoxide dismutase (SOD) are both antioxidants, while superoxide is an anion that plays a key role in regulating oxidative stress and can cause damage to lung tissue. Researchers know that SOD can degrade superoxide anions, however, data proving that dietary SOD supplementation positively benefits patients with asthma is limited.
In the case of vitamin C, one study found that horses with recurrent airway obstruction had lower concentrations of vitamin C in their airway fluid and that those with the lowest levels also had airway inflammation. There is also research in horses in to the use of supplemental vitamin C (ascorbic acid). We know that horses make their own vitamin C and that dietary sources are not particularly well absorbed, so at least 3 grams are necessary to have an impact. impact. However, when supplemented, the horse’s own production is reduced; therefore, don’t remove it abruptly if supplementing vitamin C for more than 10 days. Rather, gradual withdrawal from the diet is recommended.
Your best approach is to limit environmental pollution in the form of dust and molds and feed a source of omega-3 fatty acids and vitamin C. These two nutrients have at least been shown to have benefits in horses even if data as to their impact on respiratory health is limited. Other ingredients might help, but keep in mind that a good amount of this research is test-tube based and/or conducted in other species, and, therefore, these substances might not actually benefit horses.