Subclinical diseases underlying poor performance in endurance horses: diagnostic methods and predictive tests.
Authors: Fraipont A, Van Erck E, Ramery E, Richard E, Denoix J-M, Lekeux P, Art T
Journal: The Veterinary record
Summary
# Editorial Summary Endurance horses frequently underperform without obvious clinical signs, yet identifying the underlying causes remains challenging for practitioners. Fraipont and colleagues examined 38 endurance horses using comprehensive diagnostics—including treadmill and field exercise testing, Doppler echocardiography, airway endoscopy, respiratory fluid analysis, and standard haematological/biochemical panels—to characterise subclinical disease patterns in poor performers versus those performing well. Every poorly performing horse harboured at least one subclinical condition, with most carrying multiple concurrent disorders; well-performing horses remained disease-free. Respiratory tract pathology was most prevalent, followed by musculoskeletal and cardiac abnormalities, and poor performers demonstrated significantly reduced lactate thresholds (VLA4) and submaximal velocities at 160 and 200 bpm on both treadmill and field testing, alongside impaired heart rate recovery. These findings emphasise that systematic multi-system screening—particularly respiratory assessment—is essential when investigating performance decline, and that exercise testing parameters offer measurable markers to guide diagnostic investigation and monitor therapeutic response in endurance athletes.
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Practical Takeaways
- •Unexplained poor performance in endurance horses should trigger comprehensive screening for subclinical diseases—particularly respiratory, musculoskeletal, and cardiac conditions—rather than attributing underperformance to training or management alone
- •Standardised exercise testing with heart rate monitoring and blood lactate measurement can help identify at-risk horses; significantly lower VLA4 and V160/V200 values warrant further diagnostic investigation
- •Multiple concurrent subclinical disorders are common in underperforming endurance horses, so a single diagnosis should not conclude the investigation
Key Findings
- •All 38 poorly performing endurance horses had subclinical diseases, with most having multiple concomitant disorders, while well-performing horses were disease-free
- •Respiratory disorders were the most frequently diagnosed subclinical condition, followed by musculoskeletal and cardiac problems
- •Poor performers showed significantly lower velocities at blood lactate 4 mmol/l (VLA4) and at heart rates of 160 and 200 bpm compared to controls
- •Poor performers exhibited slower heart rate recovery post-exercise on both treadmill and field testing