A healthy respiratory system is essential to allow horses to perform to the best of their ability. Horses are stabled for increasing amounts of time during the winter months. This can lead to irritation of the respiratory tract causing a cough and nasal discharge which requires time off work and can be costly to treat. The irritants causing inflammation of the airways include dust, spores from mould and ammonia. Young horses exposed to a stabled environment can develop ‘inflammatory airway disease’ (IAD). Continued exposure of the airways to irritants leads to individual horses becoming allergic to these. IAD then progresses to Equine Asthma between 7 and 12 years of age. Equine asthma was formerly known as Recurrent Airway Obstruction (RAO), COPD (Chronic Obstructive Pulmonary Disease), small airway disease or broken wind.
A cough, nasal discharge and marked breathing effort using the abdominal muscles (‘heaves’) are all signs of Equine Asthma. The signs are caused by the lower airways narrowing through muscle spasm and excess mucus production. The more the airways react, the more sensitive they become to other irritants.
Diagnosis is through clinical examination and assessment and sampling of the lower respiratory tract using an endoscope.
Treatment involves the use of medication to relax the airways and stop muscle spasm.
Irritants can be removed from the horse’s environment with the correct management. Equine Asthma is effectively a disease caused by the domestication of the horse and stabling. Fortunately, 80% of horses can be treated by a change in management alone by providing a well-ventilated environment and reducing exposure to irritants.
Soaking hay for at least 20 minutes with complete immersion under the water will remove dust and spores allowing a forage suitable to feed. Alternatively steaming hay will have the same beneficial effects without the mess and waste of soaking. Haylage is suitable to feed as its production avoids dust and spores. Bucket feed should be dampened prior to feeding.
Dust free bedding can also help to reduce the irritant burden on the horse’s respiratory tract. Rubber mats, paper, shavings and aubiose bedding are preferable to straw. Ammonia is produced from urine in bedding and therefore provision of a dry clean bed with adequate drainage is of utmost importance.
Providing access to grazing for as long as possible will obviously reduce exposure to stable irritants and the head down posture will allow drainage of mucus from the lungs. If the horse has to be stabled then feeding all food from the floor will assist drainage and prevent the aerosol production of dust when pulling hay out of a haynet. Stabling in an outside block rather than within a building will provide fresh air. Muck heaps and hay stores should be positioned away from stable blocks. Mucking out of stables should be carried out whilst the horse is outside as this generates airborne particles contributing to airway irritation.