Respiratory Rate Recovery After Submaximal Lunging Exercise Is Delayed in Asthmatic Horses with Neutrophilic Airway Inflammation

Equine asthma is a common cause of poor performance, but little is known about its impact on submaximal exercise. The aim of the present study was to evaluate the effects of equine asthma and potential confounding factors on recovery of respiratory rate (RR) and heart rate (HR) after a lunging exercise test. Thirty-seven horses completed a standardized 15 min lunging exercise including HR and RR recording pre- and up to 30 min post-exercise and venous blood lactate measurement. Endoscopy was performed and bronchoalveolar lavage fluid cytology was used to categorize horses as controls or asthmatics. In the univariate analyses, asthmatic horses (<i>n</i> = 21) showed prolonged RR recovery (OR 52.25, 95% CI 5.17-528.28, <i>p</i> = 0.001) and took more than 15 min to return to pre-exercise levels. Prolonged recovery was associated with bronchoalveolar lavage fluid neutrophilia (OR 1.14, 95% CI 1.01-1.29, <i>p</i> = 0.04) and also with trot velocity (OR 17.32, 95% CI 1.23-244.15, <i>p</i> = 0.03). HR recovery increased with higher training level (OR 0.14, 95% CI 0.02-0.83, <i>p</i> = 0.03) and decreased with age (OR 1.20, 95% CI 1.03-1.40, <i>p</i> = 0.02). RR recovery after the submaximal lunging exercise could offer a practical test for functional deficits associated with equine asthma.