Medical causes of poor performance and their associations with fitness in Standardbred racehorses.
Authors: Lo Feudo Chiara M, Stucchi Luca, Conturba Bianca, Stancari Giovanni, Zucca Enrica, Ferrucci Francesco
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Medical causes of poor performance in Standardbred racehorses A cohort of 259 nonlame Standardbred trotters presenting with poor performance underwent comprehensive investigation including exercise treadmill testing, airway endoscopy, bronchoalveolar lavage, and gastroscopy to identify subclinical medical disorders and their effects on measurable fitness parameters. Moderate equine asthma and equine gastric ulcer syndrome emerged as the most prevalent conditions, with exercise-induced pulmonary haemorrhage, dynamic upper airway obstructions, cardiac arrhythmias, and exertional myopathies also documented across the population. Fitness variables—specifically treadmill velocity at 4 mmol/L plasma lactate and at 200 beats per minute heart rate—were significantly compromised by multiple factors: bronchoalveolar lavage neutrophilia, multiple dynamic airway obstructions, exertional myopathies, and squamous gastric disease all reduced performance capacity, whilst haemosiderin accumulation (indicating previous pulmonary bleeding) correlated with airway inflammatory markers. These findings reinforce that poor performance in racehorses is genuinely multifactorial; practitioners should recognise that a single lameness exclusion is insufficient, and that subclinical respiratory disease, gastric pathology, and myopathic changes warrant investigation through exercise testing and ancillary diagnostics when performance deficits persist. The data suggest targeting anti-inflammatory strategies and gastric management may improve fitness outcomes, though the complex interactions between conditions mean individualised diagnostic protocols remain essential for optimal case management.
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Practical Takeaways
- •Poor performance in Standardbreds is multifactorial; respiratory disease (asthma, EIPH, airway obstruction) and gastric ulcers account for the majority of subclinical causes in nonlame horses—exercise testing with endoscopy and BAL is valuable for diagnosis.
- •Multiple concurrent disorders are common; horses with elevated inflammatory markers on BAL or muscle enzymes often have additional pathology affecting fitness that may not be apparent on clinical exam alone.
- •Fitness variables measured on treadmill testing (lactate threshold, velocity at HR 200) are reliable indicators of performance impairment and can guide treatment priorities and return-to-racing decisions.
Key Findings
- •Moderate equine asthma and gastric ulcers were the most prevalent disorders in nonlame Standardbreds with poor performance, followed by EIPH, DUAOs, arrhythmias, and myopathies.
- •BAL neutrophilia, multiple DUAOs, exertional myopathies, and squamous gastric disease negatively affected treadmill velocity at lactate threshold and HR 200 bpm.
- •Increased creatine kinase activity was significantly associated with BAL neutrophilia, DUAOs, premature complexes, and gastric ulcers.
- •Hemosiderin score correlated positively with BAL inflammatory cells (neutrophils, eosinophils, and mast cells).