Q. My veterinarian just diagnosed my 23-year-old mare with heaves. What’s the best feed and forage for her? I know, ideally, being on pasture is best for the condition but, unfortunately, she can only be turned out at night because of an allergy to midges.

—Barb, via e-mail

A. Heaves is a common name for recurrent airway obstruction (RAO), which is one of the syndromes characterized under the equine asthma umbrella. Horses with RAO often have a narrowed airway, produce mucus in their airways, and suffer from bronchospasm (a temporary constriction of the airways into the lungs caused by muscle contraction).

Unlike horses that have inflammatory airway disease (IAD, another equine asthma syndrome), horses with RAO have trouble breathing at rest, resulting in an increased resting respiratory rate and cough.

Management Tip: Limit Access to Irritants

A big component of managing asthmatic horses is to limit contact with anything that might be an airway irritant, so it’s best to avoid keeping such equids in dusty environments and limit their contact with mold spores. Of course, this can make the typical barn environment challenging: Bedding is often dusty, and even good-quality hay contains dust and low levels of mold spores. Look for dust-free bedding and avoid using straw—frequently, it is contaminated with mold.

Another tip: It’s best to remove horses from stalls when they’re cleaned because the process disturbs settled mold and dust, rendering it airborne and more likely to come in to contact with lung tissue.

And, sweep barn aisles rather than using leaf blowers, which generate huge amounts of airborne particles that are potentially hazardous to all horses—not just those with asthma. Ideally, keep horses with asthma out of stalls when barns are being swept, as well.

Feeding Forage

Research has shown that using specially designed hay steamers can essentially eliminate mold and dust from hay. While these steamers are, by far, the most effective way of reducing these irritants, they’re not always a practical or financially viable option.

In such cases soaking hay is the next best choice. Hay only needs to be soaked for a short period of time to reduce mold and dust contamination; avoid lengthy soaking, which can reduce the hay’s nutritional value.

If neither option is practical, consider using hay pellets or cubes, because these are less dusty than long-stem hay. You can use an automatic feeder to provide pellets at intervals around the clock.

Regardless of what forage form you choose, try to feed from ground level. This is a more natural grazing position and has been shown to benefit respiratory health, because the horse’s airways are able to drain properly.

Potential Pasture Problems

Pasture is a good option for some horses with RAO. However, others can be irritated by pollen during the spring and summer. Given your horse’s age, I’d recommend asking your veterinarian to confirm that your horse does not have pituitary pars intermedia dysfunction (PPID, or equine Cushing’s disease), which can lead to insulin resistance and laminitis development, especially when horses are on pasture.

Aged horses have an increased risk of comorbidities, or multiple diseases occurring simultaneously. A 26-year retroactive study of 70,744 horses in the United Kingdom showed that veterinarians diagnosed 1,232 horses with RAO; of those 11% also had PPID. If your horse has PPID, as well as RAO, and especially if she’s insulin resistant, this might impact how you manage her pasture access.

Feed Fatty Acids

Finally, consider feeding omega-3 fatty acids, which research indicates help support a healthy inflammatory response. One supplement shown to help horses with equine asthma provides docosahexaenoic acid (DHA), a form of omega-3 found in algae and fish oil, as well as other ingredients including certain mushrooms, MSM, and vitamin C.

The Bottom Line

Feeding an appropriate diet is an important part of managing horses with RAO. But, ultimately, your horse might need medication for part of the year or even year-round to help control inflammation and improve lung function. Your veterinarian can advise you on the best form of management specific to your horse’s needs.