Investigation of respiratory disorders in thoroughbred racehorses training at the Brazilian Jockey Club

Athletic horses need to maintain healthy airways for optimal performance. This study investigated the presence of respiratory problems in apparently healthy Thoroughbred racehorses in training. According to the Revised Consensus Statement on Inflammatory Airway Diseases of Horses (2016), determining the prevalence of respiratory disorders in different equine populations is fundamental for understanding these diseases. In total, 72 clinically sound Thoroughbred racehorses, in training at the Brazilian Jockey Club (JCB), were initially examined using interpleural pressure measurement by ventigraphy and respiratory endoscopy. When secretions were present in the airways, transendoscopic tracheal aspiration was performed, and the sample was sent for cytology. The main findings included a combination of bronchospasm and tracheal secretions with 61% of the cytology slides showing neutrophil counts ≥20%. Overall, a significant number of the horses displayed signs suggestive of inflammatory airway disease (mild equine asthma), including 47% with increased DPplmax, 11% with tracheal mucus accumulation [mucus score (MS) ≥2] and 18% with carina edema. This was more pronounced in 2-year-old horses within the population studied. These findings are consistent with the literature and reinforce the importance of routine respiratory examination of athletic horses. There is a high incidence of subclinical respiratory disorders in Thoroughbred racehorses in training at the JCB and a significant association between tracheal MS≥2, carina edema, and elevated DPplmax.