Health

Get Expert Tips for Feeding a Horse with Equine Asthma

Horses with respiratory issues can be triggered by environmental factors, but also by dusty or moldy hay. Find out how to avoid exacerbating their symptoms.

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By: Shannon Pratt-Phillips, Ph.D. |

Equine asthma is more commonly referred to as RAO (recurrent airway obstruction), but is also called COPD (chronic obstructive pulmonary disorder) or heaves. These conditions are recognized when a horse’s airways narrow (bronchoconstriction) in response to an irritant, and when coupled with excessive mucous production, result in difficulty breathing and coughing. There is also a form of RAO that is known as summer- or pasture-asthma and is attributed to higher temperatures and humidity, and some grasses, molds and spores common in the late summer, primarily in the southern U.S.

Horses with equine asthma may have acute attacks or generalized difficulty breathing due to excessive mucous production. They may also be more likely to cough and have difficulty when exercising. Some horses with chronic conditions develop “heave lines,” which is the result of well-developed abdominal muscles (an equine six-pack).

Common Causes of Equine Asthma

The most common irritants that trigger equine asthma are dust particles from hay and/or bedding, mold spores, ammonia and/or pollens, particularly for the summer type. Therefore, prevention and management of this condition can be accomplished by minimizing these in the horse’s environment. Straw and sawdust produce more dust than good quality wood shavings or shredded newspaper. Ammonia (produced from urine by bacteria in stalls, bedding, cracks in the floor, etc.) can also irritate the airways. Frequent stall cleaning and ammonia reducing applications, such as Sweet PDZ or Odor-No-More may also be helpful. The nitrogen in urine that triggers ammonia production can also be minimized by not overfeeding protein. Most of these horses do best when kept outside as much as possible to reduce barn-related irritant exposure.

Feeding Solutions for Equine Asthma

Hay is another major culprit of triggering equine asthma. Dust and mold particles found in hay can be very irritating and can trigger a reaction in afflicted horses. There are several ways to minimize the risk of hay, as well as other high-fibre feeds that could be offered to decrease the amount of hay fed to the horse.

One of the first things to do when purchasing hay is to look at it carefully; open up a bale or two, shake open some flakes and look and smell to determine the dust and mold level. Ideally, you also can have your hay tested for mold presence before you purchase it. It should have less than 500,000 colony forming units per gram (cfu/g) when fed to the horse. While soaking and/or steaming can decrease mold and dust, some hay is simply unsuitable for horses. Another good reason to get your hay tested is to ensure its mineral content – as both steaming and soaking hay can decrease mineral content of the hay, which could be problematic if not accounted for elsewhere in the horse’s diet.

  • Wetting or dampening hay is quick and easy, and decreases dust particles. It will not greatly affect the mineral content of the hay, nor will it affect any water soluble carbohydrates (WSC, simple sugars) that could affect the calorie content of your hay. However, decreasing WSC in hay might also be valuable for an insulin resistant and/or obese horse.
  • Soaking hay in water (at cool to room temperature for about 30-60 minutes) will also greatly reduce dust and mold, and will also decrease NSC. However, it can also start to decrease potassium, which might be a good thing for horses with hyperkalemic periodic paralysis or HYPP, and phosphorus. These reductions increase with longer soaking. Soaking hay does not do much to mold particles, however. An easy way to soak hay is to put it in a hay net and place it in a tub of water. Alternatively, you can make a great contraption using two muck tubs. Drill holes (about 1 cm in diameter) in one tub. Then sit that one in the other tub, put hay in and fill with water. When you’re ready, just lift up the holed bucket and water will drain out, and you can place the whole tub in your horse’s stall for eating.
  • Steaming hay with a commercial hay steamer is an effective and easy, but costly, method. Typically, hay should be steamed for about 90 minutes. Once steamed, it should be fed immediately. Steaming appears to decrease phosphorus by about 16%. Steaming kills mold, though it is unknown if dead mold can also cause problems. Hay produced in some parts of Canada is already low in phosphorus, so it should be tested to determine if supplementation will be needed. The cost of different steamers varies, but typically start at close to $1,000 up to $3,000. Some horse owners have found success by using a steam generator ($75 to $100) and a plastic “deck box” or other type of tub to hold the hay.
  • All wet/damp/steamed hay should be removed and cleaned away within a few hours of offering, otherwise it will start to mold and defeat the purpose!

Hay Replacements for Horses with Equine Asthma

If your horse with equine asthma won’t tolerate any loose hay, hay cubes or haylage might be another option. This way your horse is still getting some hay, but in a lower dust format. You would probably want to soak the cubes too. Other feeds that are high in fibre that can offset the amount of hay your horse needs to eat would be beet pulp and rice bran. These feeds are high in fibre, and will help keep the horse’s hindgut happier than just feeding less hay altogether.

Of course, your veterinarian might also have drugs and other recommendations for your horse. But, from a nutritionist standpoint, always try to purchase the best (appropriate nutrient content, low dust and mold) hay for your horse. Remember to visit with an equine nutritionist when working through your horse’s diet, particularly if you are changing how you feed it or what you are feeding.