Poor Performance: What the Research Says
Evidence from 60 peer-reviewed studies
1 Systematic Review
19 Cohort Study
15 Case Report
25 Expert Opinion
What Professionals Should Know
- •The consensus definition provides a hierarchical framework for diagnosing mild-moderate asthma in horses, but practitioners should recognise that individual diagnostic indicators do not correlate consistently with each other across published literature.
- •Current evidence is strongest for using cough and tracheobronchial mucus as diagnostic indicators; relationships between BAL cytology findings and lung function testing are more variable and warrant cautious interpretation.
- •Standardised diagnostic protocols and reporting methods are needed to improve clinical decision-making; when possible, use multiple diagnostic approaches rather than relying on single indicators.
- •Heart rate variability analysis during treadmill exercise testing can help identify cardiac arrhythmias and lameness in Thoroughbreds presenting with poor performance
- •Lower HRV during submaximal exercise may indicate lameness, while higher HRV across all phases may signal underlying arrhythmias requiring further investigation
- •Treadmill exercise testing with HRV analysis provides objective data to differentiate between cardiac and musculoskeletal causes of poor performance in racehorses
- •Horses with poor performance may have underlying musculoskeletal pain even without overt lameness signs; use RHpE to identify subtle pain indicators during ridden work
- •Saddle fit should be routinely evaluated as a significant contributor to performance issues—37% of poor performers in this study had ill-fitting saddles
- •Diagnostic anaesthesia combined with saddle adjustment can substantially improve ridden gait quality and reduce pain-related behavioural signs, making it a valuable diagnostic and therapeutic approach
- •Do not rely on antibody serology alone to diagnose Lyme borreliosis in horses; clinical signs and epidemiological context are essential for interpretation
- •Routine serological screening for Borrelia burgdorferi without clinical suspicion is not recommended and may lead to misdiagnosis
- •When evaluating lameness, poor performance, or apathy in horses, consider that seropositivity does not confirm active disease—further diagnostic investigation is necessary
- •Overground endoscopy should be performed at multiple exercise intensities, as many obstructions appear only at lower speeds and may be missed with high-speed testing alone
- •Expect to find multiple concurrent upper airway abnormalities in barrel racing horses with respiratory complaints or performance issues—single-abnormality cases are less common
- •Nasopharyngeal collapse and palatal instability are the most frequent findings in this performance group; management strategies should address these primary obstructions and any secondary abnormalities identified
- •Poor racing performance is the dominant concern triggering veterinary examination in flat racing—trainers and veterinarians should investigate systemic issues when horses underperform rather than assuming catastrophic injury
- •Step-up in race class significantly increases incident risk; careful conditioning and gradual class progression may reduce injuries in Thoroughbred flat racers
- •Epistaxis screening and exclusion protocols appear effective at reducing race-day bleeds, suggesting similar pre-entry health screening for other conditions could be beneficial
- •Race field size significantly impacts incident risk—larger fields (>8 horses) require enhanced safety protocols and veterinary oversight
- •Poor performance is the primary welfare concern in harness racing and warrants investigation; fracture rates are reassuringly low compared to other racing codes
- •Steward reporting systems effectively capture welfare issues, providing practitioners with data-driven insight into race-day safety and animal welfare management
- •Serum pNF-H levels <0.412 ng/mL are normal in healthy standardbred racehorses; higher levels may indicate neurologic injury or disease requiring further investigation
- •This reference range applies to both pre- and post-race samples, making pNF-H a useful objective biomarker for detecting subclinical neurologic problems affecting performance
- •Unlike some biomarkers, pNF-H does not vary significantly with age or normal training stress, simplifying interpretation in clinical practice
- •When diagnosing hindlimb PSD, screen all limbs for concurrent suspensory ligament injuries, especially in young horses and heavier-bodied individuals
- •Young horses and those with higher bodyweight:height ratios warrant closer monitoring and potentially modified work programs to prevent multiple suspensory ligament injuries
- •Certain breeds (Warmbloods, Thoroughbreds, Irish Draughts) show predisposition to concurrent suspensory injuries; consider this when assessing prognosis and rehabilitation
- •HSTM exercise testing remains a viable diagnostic tool for poor performance cases, with adverse events occurring in only 15% of tests and most not preventing completion
- •Even when tests cannot be completed, most cases yield a diagnostic finding regarding the performance problem, so the test should not be abandoned prematurely
- •Clinicians should recognize that different types of adverse events have variable impacts on test completion and diagnostic yield
- •Sampling only one lung with pooled BALF cytology is diagnostically reliable and can confidently diagnose equine asthma, reducing procedural burden and cost compared to bilateral sampling
- •For EIPH diagnosis, pooled sampling remains valid but with slightly lower agreement; practitioners should be aware of the 7.8% misclassification risk in borderline cases
- •Neutrophil proportions and macrophage ratios from pooled samples are highly reliable and should be the primary focus of interpretation in respiratory disease screening
- •Consider abdominal sand accumulation as a differential diagnosis in horses presenting with multiple signs including colic, poor performance, diarrhea, and abdominal sensitivity—radiography can confirm diagnosis
- •Management and feeding behavior significantly influence sand accumulation risk; greedy eaters and subordinate horses in groups warrant closer monitoring in sand-prone geographic areas
- •The nonspecific nature of clinical signs means sand accumulation should be on the differential list for performance problems and gastrointestinal complaints, not just overt colic cases
- •Race distance and horse experience level (ratings bands) are modifiable risk factors that racing authorities should consider when structuring races to reduce failures to finish
- •Seasonal variations in failure to finish rates suggest environmental or management factors may be optimizable to improve horse welfare and race completion rates
- •The low failure to finish rate relative to catastrophic injury rates internationally indicates New Zealand racing conditions or practices may provide protective factors worth investigating for broader application
- •Head and neck position during riding may directly affect airway diameter and respiratory function in sport horses
- •Consider head-neck positioning as a potential modifiable factor when addressing poor performance or respiratory noise complaints
- •Dynamic assessment of the pharynx during exercise with varied head positions may help diagnose upper airway dysfunction
- •Misbehaviour should be evaluated as a potential indicator of underlying musculoskeletal pain rather than assumed to be purely behavioural, prompting veterinary assessment
- •Understanding risk factors for misbehaviour in young/amateur horses can help inform preventive management strategies to reduce both performance issues and rider safety incidents
- •Pony Club horse handlers should be educated on misbehaviour as a multi-factorial issue involving pain, performance, and safety considerations
- •Radiographs and scintigraphy together are more informative than either alone for thoracolumbar pain diagnosis, but diagnostic analgesia remains essential for accurate localization and ruling out referred pain from limbs or sacroiliac joints
- •Presence of spinous process lesions on imaging does not automatically mean they are the primary pain source—always perform systematic diagnostic analgesia of forelimbs, hindlimbs, and sacroiliac joints before attributing poor performance to back pain
- •Horses with multiple concurrent spinal lesions (spinous process abnormalities plus intervertebral joint osteoarthritis) are at highest risk for thoracolumbar pain; breed predisposition exists with Thoroughbreds more commonly affected
- •Resting endoscopy alone is insufficient for diagnosing dynamic upper airway problems in performance horses—exercising videoendoscopy is essential for accurate assessment
- •Pharyngeal wall collapse is the most common finding in nonracing horses with respiratory complaints; consider this when investigating poor performance or abnormal breathing
- •Head and neck position during exercise significantly affects airway visualization—horses may require flexion positioning during endoscopy to reveal obstructions that affect performance
- •When interpreting negative findings from field endoscopy (overground), ensure racing conditions have been appropriately replicated, as this technique may miss dorsal displacement of the soft palate more often than treadmill testing
- •Treadmill endoscopy may be more reliable for definitively ruling out dorsal displacement of the soft palate in racehorses with respiratory concerns
- •Both techniques appear equally valid for diagnosing dynamic laryngeal collapse, so choice can be based on availability and practical considerations
- •Pressure algometry provides a practical, objective tool for documenting and tracking pain in the neck, back, and croup—useful for monitoring response to treatment or exercise modifications
- •Baseline MNT values differ significantly between horses based on age, breed, sex, and fitness; establish individual baseline measurements rather than relying on population averages
- •Symmetrical measurements across the midline are expected in healthy horses; asymmetrical thresholds may indicate regional pain or pathology worth investigating
- •Always exercise horses for 15 minutes at trot and canter before nuclear scintigraphy of the distal limb to optimize image quality and diagnostic accuracy
- •Pre-injection bandaging does not improve radiopharmaceutical uptake, so it is not necessary for diagnostic purposes
- •Thermographic assessment of foot surface temperature may be a useful non-invasive screening tool to predict distal limb perfusion status
- •CT imaging of the caudal spine and pelvis is a valuable diagnostic tool for horses with hindlimb lameness, poor performance, or suspected lumbosacroiliac pain, as diverse osseous pathologies can be identified
- •Be aware that many affected horses have multiple concurrent lesions; finding one abnormality should prompt careful examination for others in the region
- •CT findings do not always correlate with clinical signs—imaging results must be interpreted alongside clinical examination and response to treatment, as causality remains unproven
- •In Icelandic horses presenting with poor performance and/or multi-limb lameness, consider underlying myopathy and measure resting and post-exercise serum CK activity as a screening tool
- •Muscle biopsy of the semimembranosus may be warranted when CK elevation is documented, as clinical signs alone cannot distinguish affected from unaffected horses
- •Exercise intolerance and gait abnormalities in this breed warrant investigation beyond lameness diagnostics, as a breed-specific myopathy appears to be emerging
- •Viral pathogens may be uncommon causes of respiratory disease in horses; consider other differential diagnoses (bacterial, fungal, inflammatory, environmental) before extensive viral screening
- •Next-generation sequencing is a useful diagnostic tool for investigating unexplained respiratory cases, but negative results do not exclude viral involvement in small populations
- •Gammaherpesvirus 2 should be considered in young horses presenting with poor performance and cough during early training phases
- •Consider rib fractures in horses presenting with poor performance or resistance to work, not just after obvious trauma—clinical palpation alone is unreliable for diagnosis
- •Use ultrasonography as first-line imaging after scintigraphy for confirming rib fractures; radiography has poor sensitivity (42%) and should not be relied upon alone
- •Most rib fractures can be managed conservatively with good outcomes (51% return to previous level); surgery is reserved for non-healing fractures with persistent clinical signs
- •When evaluating horses with poor performance or cardiac murmurs, anechoic zones in the interatrial septum on standard ultrasound may represent anatomical variants rather than pathological shunts—3D and ICE imaging can provide definitive characterization
- •ICE is a feasible and valuable clinical tool in equine practice for detailed assessment of cardiac structures and hemodynamic flow patterns when transthoracic imaging is inconclusive
- •A patent foramen ovale with left-to-right shunt may not always have significant clinical implications; detailed imaging helps determine hemodynamic significance and guide clinical decision-making
- •Assess individual horse temperament before treadmill introduction using standardized tests to predict habituation difficulty and tailor training approaches
- •High-timidity horses require extended, patient habituation protocols with increased handling familiarity, while high-flightiness horses may habituate more readily with repeated exposure
- •Recognize that some temperament traits (freeziness, curiosity) are stable and cannot be modified through habituation, so management strategies should accommodate individual personality types rather than expecting complete behavioral change
- •Horses with chronic piroplasmosis presenting with poor performance and muscle atrophy may have autoimmune-mediated myopathy; consider serology and muscle biopsy for diagnosis
- •Autoimmune mechanisms appear central to piroplasmosis-associated myopathy, suggesting immune-modulating treatments may warrant investigation alongside anti-parasitic therapy
- •Muscle fiber atrophy and degeneration in chronically infected horses likely results from inflammatory cytokine activity rather than direct parasite damage to muscle tissue
- •Standing laryngoplasty is a safe, well-tolerated alternative to general anesthesia for treating recurrent laryngeal neuropathy in nonracing horses, with high success rates and minimal complications.
- •The standing approach allows surgeons to fine-tune arytenoid abduction degree in real-time under endoscopic visualization, reducing risk of hyperabduction.
- •Cost and recovery time are substantially reduced compared to general anesthesia procedures, making this technique practical for private practice and lower-value horses.
- •Poor performance in racehorses with concurrent fever and elevated liver enzymes warrants hepatic ultrasound and consideration of liver biopsy for definitive diagnosis
- •Diffuse hepatic fibrosis can present with nonspecific signs; baseline liver function tests and imaging should guide further diagnostic workup
- •Chronic liver disease in performance horses may manifest subtly as declining performance before overt clinical signs develop
- •Dynamic endoscopic examination during high-speed exercise is essential for diagnosing VRDDLM, as the condition may not be visible at rest
- •When VRDDLM is identified, thoroughly investigate for concurrent upper airway pathologies (vocal cord prolapse, soft palate displacement) as these frequently coexist and may be more clinically significant
- •The clinical relevance of VRDDLM alone remains unclear; focus diagnostic and treatment efforts on concurrent obstructive lesions that are better understood
- •If a horse has no visible arytenoid abduction at rest after laryngoplasty, expect dynamic collapse during exercise; however, grade 3-4 resting abduction does not guarantee normal upper airway function during work.
- •Exercise endoscopy is necessary to fully assess post-laryngoplasty patients with ongoing poor performance, as resting exams miss critical dynamic obstructions involving multiple structures.
- •Respiratory noise alone cannot diagnose the cause of upper airway dysfunction—look for concurrent vocal fold billowing, soft palate displacement, and pharyngeal involvement to explain poor performance.
- •Horses with exercise-induced performance problems require dynamic endoscopy during actual work, not resting examination, for accurate diagnosis
- •Over-ground telemetric endoscopy offers a practical alternative to treadmill examination, allowing assessment in the horse's normal working environment
- •Identifying dynamic URT obstruction during realistic exercise conditions enables targeted treatment planning for performance issues
- •This condition may be clinically silent at rest but could contribute to poor performance or respiratory noise during exercise; high-speed treadmill endoscopy may be needed to detect it during work
- •Prevalence in Clydesdales (5.2%) suggests breed predisposition; consider laryngeal pathology in draft horses with unexplained poor performance
- •Clinical significance remains unclear from this case series; further investigation needed to determine whether intervention is warranted
- •This uncommon upper airway problem can only be diagnosed using high-speed treadmill videoendoscopy—standard endoscopy at rest will miss it.
- •Affected horses are predominantly young males (2-5 years) in racing disciplines; consider this diagnosis in Thoroughbreds and Standardbreds with poor performance or respiratory noise that fail other diagnostic workups.
- •The condition may develop after previous laryngeal surgery for RLN, suggesting a possible link to advanced adductor nerve involvement requiring further investigation.
- •Sacroiliac joint pathology should be considered as a differential diagnosis in horses presenting with poor performance, back pain, or hindlimb lameness rather than assuming it is a diagnosis of exclusion
- •A validated injection technique is now available for therapeutic intervention and diagnostic confirmation of sacroiliac joint involvement
- •Practitioners should develop skill in this periarticular injection technique to improve diagnostic accuracy and treatment options for performance horses
- •Before attributing poor performance or 'behavioral issues' to training or temperament, systematically rule out physical causes that may be causing discomfort or pain
- •Collaborate with veterinarians early when performance horses show signs of behavioral problems, as these often indicate underlying pain, lameness, or other medical conditions
- •Understand that advocating for horse welfare means ensuring physical health is optimized before behavioral interventions are considered
- •Do not assume low thyroid hormone concentrations equal hypothyroidism in horses—consider nonthyroidal illness syndrome and other secondary causes before supplementing
- •Use dynamic testing (TRH stimulation) to help clarify thyroid function when blood hormone concentrations alone are ambiguous
- •Recognise that T4 supplementation is frequently used off-label for obesity and poor performance despite limited evidence supporting true primary hypothyroidism as the cause
- •Diagnosis of sacroiliac dysfunction requires a systematic approach combining clinical examination, ultrasonography, scintigraphy, and periarticular anesthesia—do not rely on any single test as definitive.
- •Be aware that sacroiliac joint injections may spread to adjacent structures like the lumbosacral joint, potentially confounding diagnostic and therapeutic outcomes.
- •Consider computed tomography for horses with suspected sacroiliac dysfunction when diagnosis remains unclear after conventional diagnostic workup, as it provides superior anatomic detail of bony structures.
- •Atrial fibrillation is treatable with good prognosis, but recurrence is common—work with your veterinarian on a long-term monitoring strategy if your horse has been diagnosed.
- •Multiple factors influence AF development (training intensity, age, underlying health issues), so a comprehensive approach to managing comorbidities may help prevent recurrence.
- •Modern diagnostic tools like cardiac mapping and implantable ECG devices can now better characterize individual cases, potentially allowing more targeted treatment decisions for your horse.
- •Consider advanced imaging (CT/MR) when routine endoscopy and radiography are inconclusive for upper airway problems, as they provide superior anatomical detail for diagnosis
- •Functional testing methods (spirometry, EIT, IOS) offer objective assessment of lower airway disease and may help differentiate functional impairment from structural abnormalities
- •A systematic approach combining traditional techniques (clinical exam, endoscopy, imaging) with newer functional diagnostics improves diagnostic accuracy and may identify performance-limiting respiratory disease earlier
- •Recognize that gammaherpesvirus infection is nearly universal in equine populations and monitor for clinical signs, particularly respiratory disease and performance issues, especially in recently transported horses.
- •Be aware that stress from transport can trigger viral reactivation and shedding; implement stress-reduction strategies during and after transport when possible.
- •Understand that antiviral treatments lack proven efficacy for these infections, so focus on supportive care, stress management, and general immune support rather than expecting pharmaceutical solutions.
- •EGGD is associated with altered gastric microbiota composition; monitoring Sarcina abundance could potentially aid in diagnosis or monitoring of disease progression
- •The sampling method (sheathed cytology brushes) is reliable for obtaining gastric microbiota samples during routine gastroscopy in performance horses
- •While microbiota alterations are evident in EGGD, the causative relationship remains unclear—microbiota changes may be secondary to disease rather than primary drivers
- •Unexplained performance loss or reduced fitness in horses warrants cardiac evaluation including auscultation and ECG; subtle cases may require long-term monitoring to confirm pAF diagnosis
- •Early detection and treatment of paroxysmal AF is important because untreated episodes can lead to permanent atrial fibrillation and chronic performance issues
- •Consider adopting newer long-term ECG monitoring technologies adapted from human medicine to improve diagnostic capability and capture intermittent arrhythmias
- •Consider the cervical spine as a differential diagnosis in horses presenting with poor performance or behavioral problems, as clinical presentations vary significantly depending on which tissues are involved.
- •Implement a systematic diagnostic approach including thorough clinical evaluation and appropriate imaging to identify the specific pathologic process before selecting treatment, rather than using a one-size-fits-all approach.
- •Recognize that cervical pain can involve bone, soft tissue, or nerve structures, each requiring different management strategies to effectively return horses to sustainable performance.
- •Consider paroxysmal atrial fibrillation as a differential diagnosis in racehorses presenting with intermittent poor performance that cannot be explained by other causes
- •Implantable loop recorders offer a practical diagnostic tool for detecting PAF in horses when traditional ECG monitoring fails to capture episodic arrhythmias
- •Early detection of PAF may enable targeted management strategies to improve or maintain performance in affected racehorses
- •Don't rely solely on sensor-based gait analysis thresholds for lameness diagnosis—normal variation between horses and days means individual baseline comparison is essential
- •Understanding the biomechanical basis of head nod and hip hike (reduced force in the affected limb) helps interpret what the sensors are actually measuring and why visual assessment still matters
- •Consider measuring withers movement and multi-limb compensation patterns in complex lameness cases, as these parameters may reveal the full clinical picture beyond simple limb-by-limb assessment
- •Consider exercising endoscopy under working conditions (harness, overcheck, load) rather than resting exams when evaluating draught horses with respiratory issues, as airway problems are most obvious during actual work
- •Overground endoscopy provides more realistic assessment of URT function in competition draught horses than stationary evaluations
- •Dynamic testing under harness and load may identify airway conditions affecting performance that resting endoscopy could miss
- •Proximal suspensory desmitis should be included in your differential diagnosis list for any lame horse, particularly those with obscure forelimb or hindlimb lameness
- •Diagnostic imaging including ultrasound and nuclear scintigraphy can help confirm the condition and guide treatment planning
- •Treatment approaches range from conservative management to advanced therapies, allowing tailoring to individual cases and performance goals
- •Don't assume back pain is ISP—rule out lameness and use diagnostic blocks before imaging to confirm clinically significant kissing spines
- •Corticosteroid injections serve both therapeutic and diagnostic roles in ISP management
- •Two proven surgical options exist (ostectomy vs. desmotomy); choice depends on case specifics and surgeon experience—discuss both with your vet
- •Back pain diagnosis remains challenging and relies heavily on clinical palpation skills; integrating diagnostic analgesia blocks into your workflow can help confirm the source of pain more definitively
- •If using injection-based treatments, ultrasound guidance for vertebral facet and sacroiliac joint injections has become standard practice among peers and may improve targeting accuracy
- •Consider discussing complementary therapies (osteopathy, kinesiotherapy, acupuncture) with clients as evidence of their use among equine practitioners has grown significantly
- •Epiduroscopy offers a potential advanced diagnostic tool for horses with persistent back pain that has not been clarified by standard imaging (radiography, ultrasound, MRI)
- •This technique may enable direct visualization and potentially therapeutic intervention in the epidural space, addressing cases where imaging has been inconclusive
- •Consider referral for epiduroscopy when dealing with performance horses with back pain where conventional diagnostics have not identified a clear cause
- •Establish a protocol for professional saddle fit assessment at least annually, and more frequently if work intensity changes
- •Evaluate saddle fit both before and after exercise as back dimensions change during work
- •Investigate hindlimb lameness as the primary cause when saddle slip occurs, rather than automatically assuming saddle fit problems
- •Avoid using numnahs that apply pressure to spinous processes; use pads only temporarily to address specific fit issues
- •Physiotherapy addresses movement restoration and function in horses with musculoskeletal and neuromuscular issues—understand these principles to work effectively with PT practitioners
- •Knowledge of biomechanics and neuromotor control is essential for farriers and therapists designing interventions for back pain, poor performance, and joint problems
- •Consider the rider as part of the treatment system; asymmetries or dysfunction in the rider may contribute to equine musculoskeletal problems
- •ESWT is an available treatment option for lame horses; consult with specialized equine lameness centers for assessment and suitability
- •This therapy should be integrated into a broader diagnostic and rehabilitation protocol rather than used in isolation
- •When evaluating poor performance, systematically assess all three elements (horse soundness/pain, rider position/ability, saddle fit) rather than assuming one primary cause
- •Request dynamic saddle pressure analysis during ridden work when available, not just static fitting assessment, to identify focal pressure areas
- •Poor performance attributed to 'the horse' may reflect rider biomechanics or saddle fit issues—address all three before considering lameness investigations
- •Pelvic bony deformation is a normal physiological response to sacroiliac joint movement, not necessarily pathological—this should inform clinical assessment of horses with suspected SI joint problems
- •Asymmetric pelvic mechanics are expected during normal movement; look for dysfunction patterns rather than assuming symmetry is normal
- •Understanding that the pelvis deforms dynamically may help explain why some horses with SI joint issues show inconsistent performance or gait abnormalities
- •Facet joint osteoarthritis should be considered as a primary diagnosis in horses presenting with thoracolumbar pain and poor performance, not just as an incidental finding
- •Multiple lesions in the caudal thoracic/cranial lumbar region are common; imaging should focus on T15-L1 when back pain is suspected
- •The presence of dorsal spinous process impingement significantly alters clinical presentation, so concurrent abnormalities should be assessed to guide prognosis and treatment decisions
- •When investigating poor performance complaints, systematically assess multiple body systems (lungs, heart, muscles, energy metabolism) rather than relying on single tests.
- •Spirometry and field-applicable exercise testing techniques provide valuable objective data to differentiate real pathology from training or management issues.
- •Consider the individual horse's status, history, and possibility of subclinical disease when interpreting functional test results in performance evaluation.
- •High-speed treadmill videoendoscopy should be routinely used for horses presenting with poor performance or respiratory noise, as nearly half develop detectable upper airway abnormalities during exercise that may not be apparent at rest
- •Plan for multiple concurrent airway abnormalities when counseling owners on diagnosis and prognosis, as half of affected horses have more than one condition
- •Horses with respiratory noise complaints have a much higher yield (82%) for finding pathology compared to poor performers (49%), helping prioritize diagnostic resources
- •The sacroiliac joint is highly stable with minimal normal movement; clinical signs attributed to SIJ disease may reflect dysfunction rather than instability
- •Ligament integrity is critical to SIJ stabilization—ligamentous tears observed at necropsy likely compromise joint support and warrant investigation as sources of hindlimb lameness
- •Current in vivo assessment methods for SIJ pathology are limited due to the small magnitude of normal movement; rely on clinical signs, imaging, and response to localized treatment rather than movement analysis
Key Research Findings
A scoping review of 45 studies across 6092 horses identified consensus diagnostic criteria for mild-moderate equine asthma including cough, poor performance, increased tracheobronchial mucus, inflammatory BAL cytology, and pulmonary dysfunction.
Evidence was more consistent for certain diagnostic relationships (e.g., cough and tracheobronchial mucus) than others (e.g., BAL cytology and lung function).
High risk of bias in approximately 50% of articles in domains of study power and masking limited strength of conclusions.
Heterogeneity in clinical and laboratory measures across 44 predominantly observational and cross-sectional studies (median 74 horses) precluded meta-analysis and highlighted need for standardisation.
During submaximal exercise, lameness was associated with decreased logRMSSD (B = -0.19, p = 0.006)
During submaximal exercise, arrhythmia was associated with increased logRMSSD (B = 0.31, p = 0.04)
During strenuous exercise and recovery, arrhythmia was associated with significantly increased HRV indices (logSDRR B = 0.51, p < 0.001; RMSSD B = 0.60, p < 0.001)
Presence of arrhythmia increased HRV in both exercise phases and recovery, while lameness decreased HRV during submaximal exercise
Median RHpE scores decreased significantly from 9/24 before intervention to 2/24 after diagnostic anaesthesia and saddle change (p < 0.001)
34.7% of horses showed bilaterally symmetrical short step length and/or restricted hindlimb impulsion despite only 30% being continuously lame
No correlation existed between RHpE score and maximum lameness grade before diagnostic anaesthesia (Spearman's rho = 0.09, p = 0.262)
37.3% of horses had ill-fitting saddles considered likely to influence performance
23% of horses suspected of Lyme borreliosis and 17% of clinically healthy horses were seropositive for Borrelia burgdorferi sensu lato (p = 0.371), with no significant difference between groups
Anaplasma phagocytophilum seropositivity was 20% in suspect horses versus 16% in healthy horses (p = 0.108), showing only minor differences
Dual seropositivity (both pathogens) was 6% in suspect horses and 2% in healthy horses
Evidence Base
Mild-moderate equine asthma: A scoping review of evidence supporting the consensus definition.
Kinnison T, McGilvray T A, Couëtil L L et al. (2022) — Veterinary journal (London, England : 1997)
Systematic Review
Heart rate variability during high-speed treadmill exercise and recovery in Thoroughbred racehorses presented for poor performance.
Hammond Anna, Sage William, Hezzell Melanie et al. (2023) — Equine veterinary journal
Cohort Study
Application of the Ridden Horse Pain Ethogram to 150 Horses with Musculoskeletal Pain before and after Diagnostic Anaesthesia.
Dyson Sue, Pollard Danica (2023) — Animals : an open access journal from MDPI
Cohort Study
Gehlen Heidrun, Inerle Katharina, Bartel Alexander et al. (2023) — Animals : an open access journal from MDPI
Cohort Study
Upper airway endoscopy in exercising horses: Findings in 164 barrel racing horses with respiratory clinical signs and/or poor performance.
Massie S L, Léguillette R (2023) — Veterinary journal (London, England : 1997)
Cohort Study
Race-Level Reporting of Incidents during Two Seasons (2015/16 to 2016/17) of Thoroughbred Flat Racing in New Zealand.
Gibson Michaela J, Bolwell Charlotte F, Gee Erica K et al. (2022) — Animals : an open access journal from MDPI
Cohort Study
Race-Level Reporting of Incidents during Two Seasons (2015/16 to 2016/17) of Harness Racing in New Zealand.
Gibson Michaela J, Roca Fraga Fernando J, Bolwell Charlotte F et al. (2022) — Animals : an open access journal from MDPI
Cohort Study
Levels of Serum Phosphorylated Neurofilament Heavy Subunit in Clinically Healthy Standardbred Horses.
Rojas-Núñez Irene, Gomez Adriana Morales, Selland Emily K et al. (2022) — Journal of equine veterinary science
Cohort Study
An investigation into the occurrence of, and risk factors for, concurrent suspensory ligament injuries in horses with hindlimb proximal suspensory desmopathy
Gruyaert M., Pollard D., Dyson S. J. (2020) — Equine Veterinary Education
Cohort Study
Prevalence of adverse events and their effect on completion of high speed treadmill exercise tests at a single institution (2000-2015).
Brown K, Stefanovski D, Davidson E (2020) — Equine veterinary journal
Cohort Study
Bronchoalveolar lavage fluid from both lungs in horses: Diagnostic reliability of cytology from pooled samples.
Hermange T, Le Corre S, Bizon C et al. (2019) — Veterinary journal (London, England : 1997)
Cohort Study
Owner-Reported Clinical Signs and Management-Related Factors in Horses Radiographed for Intestinal Sand Accumulation.
Niinistö Kati E, Määttä Meri A, Ruohoniemi Mirja O et al. (2019) — Journal of equine veterinary science
Cohort Study
Analysis of Failure to Finish a Race in a Cohort of Thoroughbred Racehorses in New Zealand.
Tanner Jasmine, Rogers Chris, Bolwell Charlotte et al. (2016) — Animals : an open access journal from MDPI
Cohort Study
Pharyngeal diameter in various head and neck positions during exercise in sport horses.
Go Li-mei, Barton Ann Kristin, Ohnesorge Bernhard (2014) — BMC veterinary research
Cohort Study
Misbehaviour in Pony Club horses: incidence and risk factors.
Buckley P, Morton J M, Buckley D J et al. (2013) — Equine veterinary journal
Cohort Study
Close, impinging and overriding spinous processes in the thoracolumbar spine: the relationship between radiological and scintigraphic findings and clinical signs.
Zimmerman M, Dyson S, Murray R (2012) — Equine veterinary journal
Cohort Study
Exercising upper respiratory videoendoscopic evaluation of 100 nonracing performance horses with abnormal respiratory noise and/or poor performance.
Davidson E J, Martin B B, Boston R C et al. (2011) — Equine veterinary journal
Cohort Study
Comparisons of overground endoscopy and treadmill endoscopy in UK Thoroughbred racehorses.
Allen K J, Franklin S H (2010) — Equine veterinary journal
Cohort Study
Mechanical nociceptive thresholds in the axial skeleton of horses.
Haussler K K, Erb H N (2006) — Equine veterinary journal
Cohort Study
Factors influencing blood flow in the equine digit and their effect on uptake of 99m technetium methylene diphosphonate into bone.
Dyson S, Lakhani K, Wood J (2001) — Equine veterinary journal
Cohort Study
Show 40 more references
Computed tomography of the equine caudal spine and pelvis. Pathological findings in 56 clinical cases (2018-2023).
Ogden Nadine Kristina Elise, Winderickx Katja, Stack John David (2025) — Equine veterinary journal
Case Report
Chronic idiopathic myopathy in Icelandic horses: A case series.
Hansen Sanni, Hopster-Iversen Charlotte, Berg Lise et al. (2025) — Equine veterinary journal
Case Report
The Role of Viral Pathogens in Horse Respiratory Diseases: A Cytological and Molecular Approach Using Next-Generation Sequencing.
Mazzei Maurizio, Sorvillo Benedetta, Sgorbini Micaela et al. (2024) — Animals : an open access journal from MDPI
Case Report
Rib fractures in adult horses as a cause of poor performance; diagnosis, treatment and outcome in 73 horses.
Hall Suzy, Smith Roger, Ramzan Peter H L et al. (2023) — Equine veterinary journal
Case Report
Three-dimensional and catheter-based intracardiac echocardiographic characterization of the interatrial septum in 2 horses with suspicion of a patent foramen ovale.
Vernemmen Ingrid, Paulussen Ellen, Dauvillier Julie et al. (2022) — Journal of veterinary internal medicine
Case Report
Horse Behavior, Physiology and Emotions during Habituation to a Treadmill.
Masko Malgorzata, Domino Malgorzata, Lewczuk Dorota et al. (2020) — Animals : an open access journal from MDPI
Case Report
Inflammatory Myopathy in Horses With Chronic Piroplasmosis.
Pasolini Maria P, Pagano Teresa B, Costagliola Alessandro et al. (2018) — Veterinary pathology
Case Report
Laryngoplasty in standing horses.
Rossignol Fabrice, Vitte Amélie, Boening Josef et al. (2015) — Veterinary surgery : VS
Case Report
Diagnostic exercise: poor performance in a racehorse.
Giannitti F, Petrov R, Parker J et al. (2014) — Veterinary pathology
Case Report
Dynamic ventrorostral displacement of the dorsal laryngeal mucosa in horses.
Pollock P J, Kelly P G, Reardon R J M et al. (2013) — The Veterinary record
Case Report
Exercising videoendoscopic evaluation of 45 horses with respiratory noise and/or poor performance after laryngoplasty.
Davidson Elizabeth J, Martin Benson B, Rieger Randall H et al. (2010) — Veterinary surgery : VS
Case Report
Clinical trials using a telemetric endoscope for use during over-ground exercise: a preliminary study.
Franklin H, Burnt J F, Allen K J (2008) — Equine veterinary journal
Case Report
Ventroaxial luxation of the apex of the corniculate process of the arytenoid cartilage in resting horses during induced swallowing or nasal occlusion.
Barakzai S Z, Es Cert, Milne E M et al. (2007) — Veterinary surgery : VS
Case Report
Upper airway dysfunction associated with collapse of the apex of the corniculate process of the left arytenoid cartilage during exercise in 15 horses.
Dart Andrew J, Dowling Bradley A, Smith Christine L (2005) — Veterinary surgery : VS
Case Report
Development and validation of a periarticular injection technique of the sacroiliac joint in horses.
Engeli E, Haussler K K, Erb H N (2004) — Equine veterinary journal
Case Report
The "misbehaving" performance horse: is it ever behavioral?
Contino Erin K (2025) — Journal of equine veterinary science
Expert Opinion
Diagnosis and management of thyroid disorders and thyroid hormone supplementation in adult horses and foals.
Bertin François-René, Frank Nicholas, Breuhaus Babetta A et al. (2024) — Equine veterinary journal
Expert Opinion
Review of the clinical diagnosis of sacroiliac dysfunction in horses - Challenges and limitations.
Walter L J, Stack J D, Winderickx K et al. (2024) — Veterinary journal (London, England : 1997)
Expert Opinion
Fundamentals of arrhythmogenic mechanisms and treatment strategies for equine atrial fibrillation.
Premont Antoine, Balthes Samantha, Marr Celia M et al. (2022) — Equine veterinary journal
Expert Opinion
Advances in the Diagnosis of Equine Respiratory Diseases: A Review of Novel Imaging and Functional Techniques.
Kozłowska Natalia, Wierzbicka Małgorzata, Jasiński Tomasz et al. (2022) — Animals : an open access journal from MDPI
Expert Opinion
Recent advancements in our understanding of equid gammaherpesvirus infections.
Easton-Jones Charlotte (2022) — Equine veterinary journal
Expert Opinion
A study comparing the healthy and diseased equine glandular gastric microbiota sampled with sheathed transendoscopic cytology brushes.
Voss Sarah J, McGuinness David H, Weir William et al. (2022) — Journal of equine veterinary science
Expert Opinion
Paroxysmal Atrial Fibrillation in Horses: Pathophysiology, Diagnostics and Clinical Aspects.
Kjeldsen Sofie Troest, Nissen Sarah Dalgas, Buhl Rikke et al. (2022) — Animals : an open access journal from MDPI
Expert Opinion
Equine Cervical Pain and Dysfunction: Pathology, Diagnosis and Treatment.
Story Melinda R, Haussler Kevin K, Nout-Lomas Yvette S et al. (2021) — Animals : an open access journal from MDPI
Expert Opinion
Implantable loop recorders can detect paroxysmal atrial fibrillation in Standardbred racehorses with intermittent poor performance.
Buhl Rikke, Nissen Sarah D, Winther Marie L K et al. (2021) — Equine veterinary journal
Expert Opinion
Sensor-based equine gait analysis: more than meets the eye?
T. Pfau (2019) — UK-Vet Equine
Expert Opinion
Exercising upper respiratory videoendoscopic findings of 50 competition draught horses with abnormal respiratory noise and/or poor performance.
Hackett E S, Leise B S (2019) — Equine veterinary journal
Expert Opinion
An overview of proximal suspensory ligament desmitis
Anderson Jonathan (2019) — UK-Vet Equine
Expert Opinion
Diagnosis and management of impinging spinous processes
Fiske-Jackson Andy (2018) — UK-Vet Equine
Expert Opinion
Two Multicenter Surveys on Equine Back-Pain 10 Years a Part.
Riccio Barbara, Fraschetto Claudia, Villanueva Justine et al. (2018) — Frontiers in veterinary science
Expert Opinion
Epiduroscopy of the lumbosacral vertebral canal in the horse: Technique and endoscopic anatomy.
Prange T, Shrauner B D, Blikslager A T (2016) — Equine veterinary journal
Expert Opinion
Saddles and girths: What is new?
Dyson Sue, Greve Line (2016) — Veterinary journal (London, England : 1997)
Expert Opinion
Introduction to Equine Physical Therapy and Rehabilitation.
C. McGowan, Suzanne Cottriall (2016) — The Veterinary clinics of North America. Equine practice
Expert Opinion
Extracorporeal Shockwave Therapy for the Horse
Morton Alison (2013) — EDIS
Expert Opinion
The horse-saddle-rider interaction.
Greve, Dyson (2013) — Veterinary journal (London, England : 1997)
Expert Opinion
Deformation of the equine pelvis in response to in vitro 3D sacroiliac joint loading.
Haussler K K, McGilvray K C, Ayturk U M et al. (2009) — Equine veterinary journal
Expert Opinion
Osteoarthritis of the thoracolumbar synovial intervertebral articulations: clinical and radiographic features in 77 horses with poor performance and back pain.
Girodroux M, Dyson S, Murray R (2009) — Equine veterinary journal
Expert Opinion
Physiology of equine performance and associated tests of function.
Evans D L (2007) — Equine veterinary journal
Expert Opinion
High-speed treadmill videoendoscopic examination of the upper respiratory tract in the horse: the results of 291 clinical cases.
Tan Rachel H H, Dowling Bradley A, Dart Andrew J (2005) — Veterinary journal (London, England : 1997)
Expert Opinion
In vitro assessment of movements of the sacroiliac joint in the horse.
Degueurce C, Chateau H, Denoix J M (2004) — Equine veterinary journal
Expert Opinion