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This literature review analyzes the historical development of polo, its organizational structure, the course of the game, as well as the breeding, rearing, and training practices of polo horses. Frequently occurring ailments, such as musculoskeletal injuries, respiratory diseases, and internal illnesses, are highlighted. Lameness is a major problem, with injuries to the superficial digital flexor tendon being the most common cause. Other notable diseases include exercise-induced pulmonary hemorrhage (EIPH), myositis, rhabdomyolysis, and equine infectious anemia (EIA). To ensure the welfare of polo horses, effective prevention and management strategies are crucial. These include proper training, the adaptation of the ground surface, appropriate shoeing, and compliance with animal welfare guidelines and association rules. Collaboration between associations, players, organizers, and veterinarians is crucial. Promoting responsible management practices and raising awareness among stakeholders can help ensure that polo continues to thrive while maintaining high animal welfare standards.

Thyroid diseases in horses are rare and pose challenges for veterinarians due to the complexity of clinical and diagnostic approaches. This retrospective case series describes cases of equine thyroid disease in a referral hospital population. Files of horses examined for suspected thyroid disease at an equine university clinic between 2009 and 2024 were reviewed. Data from nine horses examined for suspected thyroid disease, including signalment, clinical presentation, laboratory results, imaging findings, fine needle aspirates, biopsies, diagnoses, and treatments, were summarised. Diagnoses included thyroid adenoma (n = 6), multiple thyroid cysts (possibly thyroid adenoma (n = 1)), non-thyroidal illness syndrome (NTIS, n = 1), and iodine deficiency goitre (n = 1). Diagnostic modalities varied, with, besides manual palpation performed in every patient, basal thyroid hormone measurement and ultrasonography being the most common. Low serum iodine concentrations were noted in four horses, yet iodine supplementation was inconsistently applied. Hemithyroidectomy was performed in four horses, enabling histopathological diagnosis (three out of four). Despite being rare, thyroid diseases in horses require consistent and thorough diagnostic approaches, including imaging, laboratory, and histopathological examinations. Improved screening tools and research could enhance the diagnostic accuracy and management of equine thyroid disorders.

Polo is an equestrian sport with a long tradition, but to date there is little scientific data on health risks, particularly lameness. In an international online survey, 145 polo players (47.6% female, 52.4% male) with an average of 13.4 years of playing experience were questioned about lameness risks and influencing factors. The respondents reported a median of six horses, most frequently mares as their best-performing and healthiest animals. Horse age was significantly associated with the risk of lameness, increasing by approximately 19.5% per year (OR = 1.195; p = 0.030) and differed depending on the breed of horse. Player-related variables such as age, sex, level of experience and type of husbandry had no significant influence. Risk perception was only associated with the handicap: players with a higher handicap rated the risk of injury as lower. Sex, age and horse ownership were not relevant. Unfavourable ground conditions were cited as the most common cause of injury (58.6%). The results show that players believe key predictors of lameness, in particular the age and breed of the horses, are objective factors, while subjective risk assessments are primarily influenced by the players’ level of experience. Further studies are necessary to improve horse health in polo and to enable preventive measures.

The ‘positive list for equines’ (Regulation (EC) No 1950/2006) was implemented in the European Union in 2006. The drugs listed are approved for use in slaughter equines under certain conditions, although those drugs are not approved for use in livestock and are not listed in Table 1 of the annex to Regulation (EU) No 37/2010. The usage of such drugs has to be documented in the equine passport and a withdrawal period of six months must be adhered to before the equine can be slaughtered for human consumption. Since the withdrawal period is long, correct documentation is particularly important. This study compared the results of two sub-studies. In sub-study 1, 116 veterinarians and nine equine clinics in Germany were surveyed about the methods and drugs used for castration of equine stallions. In sub-study 2, the documentational findings of 195 equine passports, belonging to 194 horses and one donkey, were analyzed. Regarding sub-study 1, the most commonly used method for castration was reported as ‘laid down’. Drug combinations entailing at least one drug from the ‘positive list’ were used by 86.7% (91/105) of veterinarians castrating horse stallions ‘laid down’ and by 64.3% (36/56) of veterinarians utilizing this method on donkey stallions. Regarding sub-study 2, drug documentation was verified in the passports of 4.6% (9/195) of all equines and in just 12.0% (3/25) of those belonging to slaughter equine geldings. Anesthetics from the ‘positive list’ were documented in 4.0% (1/25) of equine passports belonging to slaughter geldings. Because of the high discrepancy of the drug combinations used by veterinarians and the documentation actually found in equine passports, we conclude that drug administration is very seldom documented in equine passports in Germany. This could result in drug residues in equine meat and poses a potential risk for consumers.

In Europe, equines destined for human consumption (hereafter called slaughter equines) are subject to the same restrictions of usage of veterinary drugs as other food-producing animals, with amendments regulated in the so-called ‘positive list’, Regulation (EC) No. 1950/2006. Due to the complex legal requirements for drug administration in slaughter equines, it might be that specific knowledge regarding the legislation of slaughter equines may be insufficient among veterinarians, equine owners, and equine keepers. To study this assumption, three target group-specific surveys were conducted in 2021. Answers from 153 equine treating veterinarians, 170 equine owners, and 70 equine keepers were included in the analysis. In total 68.4% (91/133) of the participating veterinarians, the regulations of the ‘positive list’, Regulation (EC) No. 1950/2006, were ‘rather complicated’ to ‘complicated’. Among the participating veterinarians, 38.4% (58/151) did not or could not answer correctly how to proceed if a slaughter equine is scheduled to receive phenylbutazone, usage of which is prohibited in all livestock by Regulation (EU) No. 37/2010. Simultaneously, 56.2% (86/153) of the participating veterinarians named phenylbutazone as the, or one of the, most often used non-steroidal anti-inflammatory drugs. Altogether, 41.2% (70/170) of participating equine owners and 42.9% (30/70) of equine keepers did not know under which circumstances an equine can legally be slaughtered for human consumption. In total, 34.3% (24/70) of the equine keepers classified their knowledge of national regulations for animal keepers regarding the documentation of drug usage in equines as ‘poor’ to ‘nonexistent’. This lack of knowledge in all three surveyed groups, combined with the complex legal regulations regarding the usage and documentation of drugs in slaughter equines, could result in missing and false documentation, treatment of slaughter equines with prohibited substances and therefore pose a risk factor for drug residues in equine meat.

Amino acid (AA) metabolism and the adaptation of muscles to increased physical performance are interdependent. This field study examined changes in plasma amino acid (PAA) concentrations and two metabolites (ammonia and urea) before and after cross-country (CC) competitions throughout an entire eventing season and their associations with performance outcomes in eventing horses. Twenty horses from nine different Warmblood breeds were evaluated between two and seven times across 14 international eventing competitions over a 23-week period. A total of 55 rides were sampled. Blood samples were collected at four time points: before the start (TP0), 10 min after completion of the CC ride (TP1), 30 min post-CC (TP2), and the next morning (TP3). A mixed ANOVA revealed significant effects (p < 0.05) of calendar week on PAA concentrations for asparagine, ornithine, and proline. Correlations between CC scores and PAA concentrations were observed for 4 of the 25 measured parameters. TP0 leucine concentrations and TP2 histidine concentrations correlated negatively with CC penalty score, whereas TP1 proline concentrations and TP3 alanine concentrations correlated positively with CC penalty score. These results indicate that higher plasma leucine concentrations may contribute to improved performance in eventing horses. Additionally, alanine and proline show potential as performance-related diagnostic biomarkers.

This study examines seasonal changes in muscle and heart parameters in eventing horses over the course of a competition season. Blood levels of the enzymes creatine kinase (CK) and aspartate aminotransferase (AST) as well as the heart muscle-specific concentration of cardiac troponin I (cTnI) were measured before (pre), 30 min (p30) and 24 h (p24) after competitions. Creatine kinase (CK: median pre-competition = 175 U/L, 30 min post = 221 U/L, 24 h post = 140 U/L), aspartate aminotransferase (AST: pre = 319 U/L, p30 = 335 U/L, p24 = 333 U/L), and cardiac troponin I concentration (cTnI: pre = 0.006 ng/mL, p30 = 0.011 ng/mL, p24 = 0.007 ng/mL) exhibited partial normalization by 24 h post-exercise but at the same time demonstrated significant seasonal variation (p < 0.001). Echocardiographic assessments revealed sustained high-level myocardial velocities, with occasional modest seasonal declines. A significant correlation was identified between cTnI levels and early diastolic myocardial velocity (Em) (Spearman’s Rho: pre-exercise 0.323, Rho p30: 0.357), whereas a negative correlation was manifest at 24 h (Spearman’s Rho = −0.300). These findings suggest a heightened sensitivity of diastolic myocardial velocity to myocardial injury. Given that diastolic dysfunction frequently constitutes an early manifestation of myocardial compromise, our results underscore the utility of biomarkers alongside myocardial velocity measures as valuable tools for the early detection of subclinical fatigue in high-performance sport horses.

Plasma amino acid (PAA) concentration in horses vary according to the exercise type. This study evaluated the changes in PAA levels and the associated metabolites, urea and ammonia, following short-duration, high-intensity cross-country exercise in eventing horses. Twenty eventing horses participated in 55 rides at 14 international competitions (2* to 4* levels) across five venues in Germany and Poland. Blood samples were collected at four timepoints: before exercise (TP0), at 10 min (TP1), and at 30 min (TP2) post-exercise, as well as in the morning on the day after the competition (TP3). A total of 23 different PAAs and two metabolites (ammonia and urea) were analyzed. PAA concentration difference over time was assessed by a mixed ANOVA. Significant fluctuations were observed in 18/25 parameters. For 21/23 PAAs, levels increased at TP1 and/or TP2, while cysteine concentrations decreased. Concentrations returned to pre-competition levels for 21/23 PAAs by TP3. Proline levels remained elevated (p = 0.002), while those of glycine significantly decreased (p = 0.027) at TP3. Plasma ammonia and urea levels increased at TP1, TP2 and TP3. This study provides foundations for supplementation strategies and can inform future works exploring PAAs’ role in performance and training adaptation in eventing horses and their potential as performance-related biomarkers.

The diagnosis of internal neoplasia in horses is challenging. Increased production of hormones physiologic for adult animals (e.g., adrenocorticotropin, norepinephrine, and erythropoietin) or typical for the foetal phase (alpha‐fetoprotein, anti‐Müllerian hormone, and parathyroid‐hormone‐related protein) might aid in tumour diagnostics. Thymidine kinase‐1 and alkaline phosphatase are examples of intracellular enzymes, whose activity in the blood may increase in some neoplasia cases. Furthermore, inappropriate production of abnormal monoclonal or autologous antibodies can accompany lymphoma and multiple myeloma. Many of those tumour markers lead to clinical or laboratory changes, called paraneoplastic syndromes, such as hypercalcaemia and erythrocytosis. The interpretation of the results of the tumour marker measurements in horses is complicated due to many factors affecting the markers’ concentration or activity (e.g., young age, pregnancy, and inflammation) and other diseases triggering the same changes. Moreover, the presence of paraneoplastic syndromes is inconsistent, which leads to low sensitivity of those substances as tumour markers. In conclusion, screening for neoplasia in horses is not recommended. The measurement of tumour markers should be performed only in risk groups with suspicious clinical or laboratory findings, and the results should be interpreted with caution. It is advisable to add inflammatory markers to the tumour profile or repeat the measurements. The measurement of tumour markers in horses should be performed only in risk groups or in patients with suspicious clinical/laboratory findings (paraneoplastic syndromes). The results should be interpreted with caution as many factors (e.g., young age, pregnancy and inflammation) affect their concentration or activity. It is advisable to add inflammatory markers to the tumour profile or repeat the measurements. Abbreviations: ACTH, adrenocorticotropin; AFP, alpha‐fetoprotein; AMH, anti‐Müllerian hormone; EPO, erythropoietin; NE, norepinephrine; PTHrP, parathyroid‐hormone‐related protein.

High elimination rates and concerns for horse welfare are important issues in endurance riding. Improved understanding of the causes of elimination could increase completion rates in this sport. We have identified pre-ride laboratory risk factors that enable an assessment of potential elimination before the ride. A longitudinal cohort study was performed among 49 healthy horses competing in the 160 km endurance ride at the 2016 World Championship of Endurance Riding in Samorin/Slovakia. Blood samples were taken before the event. For statistical evaluation, horses were categorized into three groups: finishers, lame horses, and metabolically eliminated horses. Risk factors were calculated for each group using multinominal logistic regression. δ-Aminolevulinic-dehydratase (ALAD), thiobarbituric acid reactive substances (TBARSs), iron, and serum amyloid A (SAA) were measured and did not show an impact on the race outcome, but elevated pre-ride superoxide dismutase (SOD) was shown to have an effect on lameness elimination (p = 0.011). It might serve as an indicator for withdrawing horses at risk of later elimination before endurance rides, ultimately resulting in lower elimination rates and an increase in overall horse welfare.