Western sport horse poor performance workups broaden: full analysis

A new EquiManagement report is urging veterinarians to think beyond lameness when a Western sport horse isn’t meeting expectations. Covering a presentation from the 2025 AAEP Convention, the article says poor performance in these horses is often multifactorial, with respiratory disease, muscle conditions, neurologic dysfunction, and metabolic disorders all deserving attention in the diagnostic workup. Ben Buchanan, DVM, DACVIM, DACVECC, of Brazos Valley Equine Hospital, framed the issue around both medical causes and a basic but important question: whether the horse has the genetics and capacity for the job being asked of it. (equimanagement.com)

That broader framing fits with how equine sports medicine specialists increasingly define poor performance. Purdue’s Equine Sports Medicine Center notes that the term is not a diagnosis in itself, and that veterinarians, trainers, and the pet parent need to agree on what exactly has changed, whether that’s speed, stamina, willingness, recovery time, or something else. The type of work matters, too: high-intensity, short-duration efforts place different demands on the horse than moderate or long-duration exercise, which helps explain why the same vague complaint can trace back to very different body systems. (vet.purdue.edu)

In Buchanan’s presentation, the respiratory tract stood out as a commonly overlooked source of trouble. He recommended a complete history, careful thoracic auscultation, and a low threshold for bronchoalveolar lavage as part of a standard exam, along with static or dynamic endoscopy to assess upper airway function during fatigue. The EquiManagement report cites an upper airway endoscopy study in 164 exercising barrel horses showing that halving airway size produced a 16-fold increase in pressure needed to maintain airflow, illustrating how even partial obstruction can sharply increase respiratory effort. Buchanan also pointed to bronchoalveolar lavage, thoracic ultrasound, and radiography to investigate asthma, exercise-induced pulmonary hemorrhage, and inflammatory airway disease, while also stressing environmental management such as reducing dust exposure from hay and arena footing. (equimanagement.com)

The muscle workup is just as important, especially in Quarter Horses and related breeds. Buchanan highlighted inherited and acquired contributors including PSSM1, malignant hyperthermia, HERDA, trauma, and overexertion. He advised a thorough musculoskeletal exam, creatine kinase testing, and a submaximal exercise challenge, with muscle biopsy and genetic testing considered when enzyme elevations or persistent signs warrant it. The article also notes that myofibrillar myopathy can present as persistent irritability and soreness despite no obvious cardiovascular or soundness problem, and that diagnosis requires biopsy. Supporting that concern, published research has described myofibrillar myopathy as a cause of decreased exercise tolerance and poor performance in horses, while AAEP educational material also lists poor performance, exercise intolerance, and muscle pain among the signs seen with exertional myopathies. (equimanagement.com)

One point likely to resonate with practitioners is the caution around PSSM2. EquiManagement reports that Buchanan told attendees PSSM2 testing is not yet well validated. That aligns with warnings from the British Equine Veterinary Association and UC Davis-linked publications stating that there are currently no scientifically validated genetic tests for PSSM2 or myofibrillar myopathy, despite the availability of some commercial tests. For clinicians, that means biopsy and clinical correlation still matter more than a mail-in result when trying to explain poor performance. (equimanagement.com)

Why it matters: For veterinary professionals, this is a reminder that Western performance horses deserve the same systematic, whole-horse evaluation often emphasized in other equine sports medicine settings. A horse that feels “lazy,” “stiff,” “sore,” or “not quite right” may have subtle airway disease, an exertional myopathy, a neurologic deficit, a metabolic issue, or a combination of those factors rather than a straightforward orthopedic lesion. A structured workup can help practices avoid missed diagnoses, improve communication with trainers and pet parents, and set more realistic expectations about prognosis, management, and return to work. (vet.purdue.edu)

What to watch: The next step is likely more discipline-specific guidance on how to standardize poor-performance evaluations in Western horses, including when to add dynamic airway assessment, exercise testing, muscle biopsy, and advanced neurologic workups. The conversation around validated diagnostics, particularly for suspected myopathies, also isn’t going away as practitioners balance clinical demand with still-evolving evidence. (equimanagement.com)