The relationship between lung inflammation and aerobic threshold in standardbred racehorses with mild-moderate equine asthma

Mild–moderate equine asthma (MEA) is a common disease of young racehorses characterized by inflammation of the lower airways diagnosed by cytological examination of bronchoalveolar lavage fluid (BALF), and it is considered an important cause of poor performance. The most common parameter of athletic capacity associated with horse performance is the speed at 4 mmol/L of lactate (VLA4). The aim of the present work was to evaluate the relation between the different BALF inflammatory cells and VLA4 in racehorses affected by MEA. A population of Standardbred racehorses that underwent an accurate protocol for poor performance evaluation was collected for a retrospective study. Horses with any other alteration potentially influencing performance were excluded, thus considering only subjects with BALF cytology consistent with MEA. A sample of 30 horses (3.4 ± 1.0 years old) was selected. The relationship between BALF inflammatory cell differential count and VLA4 was evaluated by means of linear regression. Statistical analysis showed a significant relation (p = 0.015, r2 = 0.19) between the increase in the differential count of neutrophils in BALF and the decrease in VLA4. The results obtained suggested that the accumulation of neutrophils in the airways of MEA horses may have a direct impact on athletic capacity, possibly due to impaired alveolar blood-gas exchanges during strenuous exercise.