Effects of Low-Intensity Exercise on Exhaled Breath Condensate Biomarkers in Healthy Horses

Abstract Exhaled breath condensate (EBC) has emerged as a promising diagnostic tool for equine respiratory disease. However, the influence of exercise on the biomarkers of EBC remains unclear. This study aimed to evaluate the influence of low-intensity exercise on EBC biomarkers (hydrogen peroxide, pH, and nitrite) in healthy horses and to assess the feasibility of postexercise sample collection under real-world conditions. Twenty clinically healthy horses (ten Quarter Horses and ten Brazilian Sport Horses) were evaluated. Respiratory rate (RR) and heart rate (HR) were recorded at rest, followed by EBC collection using a collector developed by our research group. Horses then performed 10 min of trotting, low-intensity protocol, after which RR, HR, and EBC samples were reassessed. Upper airway endoscopy and tracheal lavage with differential cytology confirmed respiratory health. Biomarker concentrations were analyzed by using appropriate parametric tests. Light exercise significantly increased RR, HR, and EBC sample volumes (p < 0.05). Sample volume evidenced a weak association with ambient temperature (p = 0.014, r = 0.186) and relative humidity (p = 0.010, r = 0.218). Exercise did not significantly affect pH (p = 0.380), hydrogen peroxide (p = 0.152), or nitrite (p = 0.218). Nitrite was negatively associated with ambient temperature (p = 0.023, r = −0.056) and relative humidity (p < 0.001, r = −0.428) and evidenced a moderate positive association with hydrogen peroxide in postexercise (p = 0.004, r = 0.611). Under the conditions evaluated, light exercise did not alter equine EBC biomarker concentrations, supporting the feasibility of postexercise sampling.