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Airway Disease in Sedentary, Asymptomatic HorsesBy Kentucky Equine Research Staff · March 21, 2017

Diagnosis of certain airway problems in horses remains challenging for veterinarians. To determine if common diagnostic tests are related to lung function, researchers recently studied a group of sedentary, asymptomatic horses.

Veterinarians use a roster of criteria to determine if a horse suffers from inflammatory airway disease, or IAD, which can be loosely defined as nonseptic inflammation characterized by the presence of mucus on endoscopy, inflammatory changes in bronchoalveolar lavage fluid (BALF), or pulmonary dysfunction, including coughing. Little information is available regarding the correlation between BALF and pulmonary function testing (PFT) in horses.

In this study, 38 horses underwent PFT and histamine bronchoprovocation with flowmetric plethysmography to diagnose IAD. Bronchoalveolar lavage was performed 1 to 5 days after bronchoprovocation. Bronchoalveolar lavage is a procedure in which a bronchoscope is passed through the nose and into the lungs. Fluid is then squirted into the lung and recollected for microscopic examination.

Of the tested asymptomatic horses, 52% were diagnosed with airway hyperreactivity. BALF cytology revealed, on the other hand, that 95% of horses had IAD. The number of horses in this study with IAD, as evidenced through hyperreactivity and BALF cytology, was greater than researchers anticipated, given that none of the horses showed sign of the disease, though no background information was given on the management of the study horses. Because of this, the researchers questioned the prudence of using invasive lung tests on horses without any symptoms and encouraged further investigation in horses with historical and clinical signs of the disease.

Because of its anti-inflammatory properties, omega-3 fatty acids have been found to help horses with airway disease. Dietary supplementation of the omega-3 known as docosahexaenoic acid (DHA) can be an effective therapeutic approach when coupled with a low-dust diet to reduce airway inflammatory symptoms. Supplementing with marine-derived sources, such as EO•3, means the horse is directly receiving the long-chain omega-3 fatty acids DHA and EPA (eicosapentaenoic acid). Supplementation with plant-based sources (flaxseed, for example) require the conversion of short-chain fatty acids (ALA) to EPA and DHA. This conversion is thought to be inefficient in the horse.

*Cullimore, A.M., C.J. Secombe, G.D. Lester, and I.D. Robertson. 2016. The relationship between bronchoalveolar lavage fluid cytology and airway hyperreactivity in a population of sedentary horses. In: Proc. 38th Bain Fallon Lectures. Equine Veterinarians Australia, p. 17.