Factors associated with safe completion of Fédération Equestre Internationale eventing cross-country (2008-2018).

BACKGROUND: Equestrian eventing involves competing in three phases: dressage, jumping, and cross-country. Competitors are ranked by number of penalties accrued-with those who have fewer penalties ranked higher. Completing the cross-country phase with zero obstacle penalties is commonly referred to as 'running clear'. Understanding factors associated with running clear can help athletes plan strategically for success, while also helping governing bodies to refine qualification criteria for elite levels. OBJECTIVES: This study was carried out to identify factors associated with running clear in the cross-country phase of Fédération Equestre Internationale (FEI) eventing. STUDY DESIGN: Retrospective cohort study of 107 348 horse starts worldwide in all FEI competitions between January 2008 and December 2018. METHODS: Multivariable logistic regression models constructed stepwise using a bi-directional process. Two study cohorts were assessed: a complete cohort that met all inclusion requirements and separately, a cohort that included only horses starting at the level above their previous start. RESULTS: Sixteen factors were associated with running clear. Factors associated with increased likelihood of doing so included lower event level, lower dressage score earlier in the event, fewer recent FEI event starts, and more clear runs in their previous three FEI events. For horses that had stepped up an event level, 14 of these factors were still associated with running clear. MAIN LIMITATIONS: Data available covered only FEI events, no national federation competitions were available for inclusion in horse histories. No prior veterinary information or data on training were available. CONCLUSIONS: This study provides a framework that allows stakeholders to potentially better understand the appropriate level of competition for any particular horse/rider combination, given the combination's recent history. This could provide an additional direct benefit in terms of safety by reducing the likelihood of a combination falling during cross-country.

Anomalous Incidence of Fatal Musculoskeletal Injury in North American 2-Year-Old Thoroughbred Racehorses in the Year 2020.

Racehorse training and racing schedules in many parts of the United States and Canada were interrupted or otherwise reduced during the first three to six months of 2020. This was an indirect consequence of mitigations to prevent the spread of the pandemic virus COVID-19. Data from the Equine Injury Database, a census-level survey of all race starts made in the USA and Canada, were used to analyse the incidence of fatalities in 2009-2022 among three age cohorts of racehorses within each year. There was a statistically significant increase in the incidence of musculoskeletal fatalities among 2-year-old Thoroughbreds in 2020, compared to the period 2009-2019. In 2021 and 2022, the training schedules of 2-year-old horses returned to pre-2020 levels, as did the incidence of fatalities. The delayed start to training for 2-year-old horses was associated with an increase in risk of fatal musculoskeletal injury for those horses during 2020, but the risk for the same horses in 2021-when they were 3 years old-was not significantly different to the risk for 3-year-olds in any other year. The increased risk of fatal musculoskeletal injury in 2020 was only found among horses that were 2 years old in 2020-horses aged 3 years or more in 2020 were not at increased risk.

Fédération Equestre Internationale eventing: Fence-level risk factors for falls during the cross-country phase (2008-2018).

BACKGROUND: The equestrian discipline of eventing tests athletes' and horses' skill over three phases: dressage, jumping and cross-country. Falls during cross-country can be particularly serious and result in serious or fatal injury for both horse and athlete. Cross-country course and fence design are crucial contributory factors to safety. OBJECTIVES: To provide descriptive statistics and identify fence-level risk factors for horses competing in Fédération Equestre Internationale (FEI) events worldwide. STUDY DESIGN: Retrospective cohort study. METHODS: Data were collected for every horse start worldwide in all international (CI), championship (CH), Olympics (OG) and World Equestrian Games (WEG) eventing competitions between January 2008 and December 2018 and univariable logistic regression, followed by multivariable logistic regression were applied. The final model was built in a stepwise bi-directional process, with each step assessed by the Akaike information criterion. RESULTS: Risk factors were identified at the fence level covering aspects of fence design and course design. Ten fence types were at increased odds of a fall occurring compared with square spread fences, and seven types were at reduced odds. Fences with an approach downhill (odds ratio [OR] 1.35, 95% confidence interval [CI] 1.19-1.52), with landing into water (OR 1.82, CI 1.62-2.01), frangible devices (OR 1.28, CI 1.15-1.41) and later elements of combined obstacles (OR 1.33 CI 1.25-1.42 for the second element, OR 1.21 CI 1.10-1.32 for later elements) were associated with increased risk of falls occurring. MAIN LIMITATIONS: Although the dataset covers every international competition worldwide, it does not include national-level competitions. CONCLUSIONS: It is recommended that the most challenging fences are placed near the beginning of the course, and not in downhill or water settings. The complexity of individual elements in combined fences should be reduced. Adopting evidence-based course design is a crucial intervention for reducing the incidence of horse falls and associated serious and fatal injuries to horse and human athletes.

Fifteen risk factors associated with sudden death in Thoroughbred racehorses in North America (2009-2021).

OBJECTIVE: To identify risk factors associated with race-related sudden death in Thoroughbred racehorses in the US and Canada. ANIMALS: 4,198,073 race starts made by 284,387 Thoroughbred horses at 144 racetracks in the US and Canada between 2009 and 2021. PROCEDURES: Study data were extracted from the Equine Injury Database, which contains detailed records of 92.2% of all official race starts made in the US and Canada during the study period. Forty-nine potential risk factors were analyzed using univariable and multivariable logistic regression. Cases were defined as race starts that resulted in fatality within 3 days of racing, in which at least 1 of 5 codes relating to sudden death was recorded. Fatalities due to catastrophic musculoskeletal injury were omitted from the study cohort. RESULTS: 536 race starts resulted in sudden death, an incidence rate of 0.13/1,000 starts. Fifteen risk factors were significantly associated with sudden death, including horse age and sex, season and purse of race, race distance, and horses' recent history of injury and lay-up. Horses racing while on furosemide medication were at 62% increased odds of sudden death. CLINICAL RELEVANCE: Associations found between previous injury and sudden death suggests preexisting pathology could contribute in some cases. The association between furosemide and sudden death prompts further study to understand which biological processes could contribute to this result.

Fédération Equestre Internationale eventing: Risk factors for horse falls and unseated riders during the cross-country phase (2008-2018).

BACKGROUND: Eventing is an equestrian sport that tests athletes' and horses' skill over three phases: dressage, jumping and cross-country. Falls during the cross-country phase can have very serious outcomes up to and including death for both horse and athlete. Therefore, understanding risk factors associated with falls is essential for improving equine and human welfare. OBJECTIVES: To provide descriptive statistics and identify risk factors at the horse-, athlete- and course-level affecting horses competing in Fédération Equestre Internationale (FEI) events worldwide. STUDY DESIGN: Retrospective cohort study. METHODS: Data collected by the FEI of every horse start worldwide in all international (CI), championship (CH), Olympics (OG) and World Equestrian Games (WEG) competitions between January 2008 and December 2018 were analysed. Descriptive statistics followed by univariable logistic regression to identify risk factor candidates for inclusion in the final multivariable logistic regression model. Models were constructed stepwise using a bi-directional process and assessed using the Akaike information criterion. RESULTS: Factors associated with increased risk of falls and or unseated rider included: higher event levels, longer course distances, more starters at cross-country phase and less experienced horses and athletes. MAIN LIMITATIONS: The data set is geographically comprehensive but covers only FEI competitions, not National Federation events, that is not every competition started by every individual horse. Nor does the data set include any prior veterinary information or data on training or schooling. CONCLUSIONS: This is the first large-scale epidemiological study of cross-country falls in FEI eventing. Results suggest that a potential risk profile can be constructed for each horse-athlete combination prior to entering a given competition, based on individual histories and course-level factors. This could lead to interventions that can reduce the number of falls, thus protecting equine and human welfare.

Factors associated with completion of Fédération Équestre Internationale endurance rides (2012-2019): Modelling success to promote welfare-oriented decisions in the equestrian sport of endurance.

Endurance riding is a popular equestrian sport organised at the international level by the Fédération Équestre Internationale (FEI). The sport involves prolonged exercise at speed over significant distances, which puts a substantial load on equine athletes' musculoskeletal systems and metabolism and contributes to the risk of injuries and other veterinary problems. The FEI employs a system of in-ride veterinary inspections aimed at early detection of such problems and elimination of horses unfit to continue in the ride. To date, risk factors for elimination due to irregular gait or metabolic problems have been the primary focus of scientific enquiry. The present study is the first large-scale multivariable study to report factors associated with the positive outcome of endurance rides - their successful completion. This retrospective observational cohort study used data from the FEI's Global Endurance Database. The study cohort included 74,629 starts made by 21,346 unique horses in one-day international-level competitions held worldwide between July 2012 and December 2019. Forty-one potential factors identified based on previous studies and a priori hypotheses were considered in the analysis. Univariable and multivariable logistic regression analyses were performed to investigate associations between ride completion and predictor variables and their interactions. The study identified 19 factors and four interactions associated with an increased or decreased likelihood of successful ride completion. High competition frequency (fewer days over mandatory out of competition period; Wald χ2 71.35, P-value <0.0001), fast riding speed (236.57, <0.0001), upward changes in competition level and riding speed between two successive rides (103.59, <0.0001 and 87.60, <0.0001) were associated with a decrease in the likelihood of ride completion. These factors can be effectively regulated by appropriate rules and considered by athletes when planning competition schedules, preparing ride strategies, or indeed during the ride itself. Other identified factors, including horse and rider age, sex, completions and eliminations history, contribute to an estimate of the likelihood that a particular combination completes a ride and thus can aid veterinarians at veterinary inspections as additional inputs supporting their decision-making when assessing horses' fitness to continue in the competition. The study's main limitation is an absence of data on national-level rides. Such data and data on training and veterinary histories remain difficult to access and were unavailable for the analysis. The present study's results demonstrate that shifting the focus to modelling the positive outcome is a valuable approach offering evidence-based recommendations for good horsemanship, better-informed veterinary inspections, and welfare-oriented rules.

Association between the administration of phenylbutazone prior to racing and musculoskeletal and fatal injuries in Thoroughbred racehorses in Argentina.

OBJECTIVE: To examine the association between prerace administration of phenylbutazone and the risk of musculoskeletal injury (MSI) and fatal injury in Thoroughbred racehorses that raced between 2006 and 2015 at 2 of the 4 official racetracks in Argentina. SAMPLE: Data from racetrack databases and veterinary reports on 283,193 race starts. PROCEDURES: Data were collected relating to race performance and injury outcomes for starts at these tracks. The incidence of MSI and fatal injury was calculated for each year, stratified by the declared prerace administration of phenylbutazone. Univariable logistic regression, followed by multivariable logistic regression, was used to identify significant risk factors for both MSI and fatal injury. RESULTS: Analyses identified associations between the declared prerace administration of phenylbutazone and the risk of MSI and fatal injury during racing. Horses with declared prerace phenylbutazone administration had greater odds of MSI (OR, 1.45 [95% CI, 1.03 to 2.04]) and fatal injury (OR, 1.59 [95% CI, 1.1 to 2.27]) than did horses racing without prerace phenylbutazone administration. These associations remained significant when other risk factors were accounted for in both multivariable models. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested an association between the prerace administration of phenylbutazone and the risk of MSI and fatal injury in Thoroughbred racehorses during racing. Although these results did not imply a direct causal relationship between prerace phenylbutazone administration and injury, they may be considered in the development of more conservative medication policies to optimize racehorse welfare in North and Latin America.

The association between clinical parameters recorded at vet gates during Fédération Equestre Internationale endurance rides and the imminent risk of elimination.

BACKGROUND: Endurance competitions over distances of 80-160 km are required by Fédération Equestre Internationale (FEI) rules to be divided into a number of stages between three and six. These stages are also known as "loops". Veterinary inspections, designed to ensure horse welfare, are conducted at the end of each loop, with details recorded on a separate "vet card" for each horse. OBJECTIVES: To identify risk factors recorded on vet cards that were associated with elimination at subsequent loops. STUDY DESIGN: Retrospective cohort study. METHODS: Data relating to 3213 horse starts worldwide in international (CEI) events during 2014 were analysed. Univariable logistic regression was used to identify risk factors for potential inclusion in a final multivariable logistic regression model. Models were constructed stepwise using backwards-removal and assessed using the Bayesian information criterion. RESULTS: Risk factors were identified, which would allow an "in-ride" risk profile to be constructed for each horse which evolves as the horse progresses through the ride. Some risk factors such as abnormal gait and high heart rate were found to be repeatedly associated with imminent failure to qualify. MAIN LIMITATIONS: This is a relatively small study in terms of cohort size, based on the data that were available at the time of the study. Although comprehensive ride history data were also available for each horse via the main FEI database, training data were not. CONCLUSIONS: By identifying risk factors observed during the veterinary inspections at the end of a loop that are strongly associated with elimination at the end of the next or subsequent loops, these results provide an evidence-base for educational initiatives and regulatory changes that will inform the way veterinary delegates use veterinary inspections to help identify horses at risk of imminent FTQ.

Effect of osteoarthritis on the repeatability of patella tendon angle measurement in dogs.

OBJECTIVE: To evaluate the influence of osteoarthritis on the measurement of patella tendon angle (PTA) and determine intraobserver and interobserver variability. STUDY DESIGN: Retrospective clinical study. SAMPLE POPULATION: Eighty-seven mediolateral radiographs that were obtained prior to tibial tuberosity advancement. METHODS: Radiographic osteoarthritis was scored by 2 observers using guidelines derived from the International Elbow Working Group Protocol. Patella tendon angle was measured by 3 observers on 3 occasions, with at least 7 days between measurements. The data were statistically analyzed via weighted κ and Kruskal-Wallis testing. RESULTS: A fair strength of agreement was found among observers scoring osteoarthritis, with the same grades in 48% of radiographs. The intraobserver average bias between PTA measurements 1 and 3 ranged from -0.38° to -0.94°. Interobserver bias in angle measurement ranged from -0.92° to -2.00°. Observer 1 had the narrowest range of PTA differences (12.1°), and observer 3 had the highest range of PTA differences (23.5°). Observer 2 had the lowest mean bias (-0.38°). The mean bias was lowest between observers 1 and 2 (-0.92°) and highest between observers 1 and 3 (-2.0°). The mean intraobserver standard deviation of the PTA measurement differences was 2.90°, and interobserver standard deviation of the PTA measurement differences was 2.26°. The degree of osteoarthritis did not influence PTA measurements or their variability. CONCLUSION: The current study did not find evidence of an influence of osteoarthritis on PTA or on the repeatability of measurements. CLINICAL SIGNIFICANCE: Our findings suggest that osteoarthritis should not affect the radiographic planning for tibial tuberosity advancement surgery. The high variances in PTA measurement in less experienced observers may influence the clinical outcome of surgery.

Risk factors for equine fractures in Thoroughbred flat racing in North America.

The aim of this paper is to identify risk factors associated with equine fractures in flat horse racing of Thoroughbreds in North America. Equine fractures were defined as any fracture sustained by a horse during a race. This was a cohort study that made use of all starts from the racecourses reporting injuries. The analysis was based on 2,201,152 racing starts that represent 91% of all official racing starts in the USA and Canada from 1st January 2009-31st December 2014. Approximately 3,990,000 workout starts made by the 171,523 Thoroughbreds that raced during that period were also included in the analysis. During this period the incidence of equine fractures was 2 per 1000 starts. The final multivariable logistic regression models identified risk factors significantly associated (p<0.05) with equine fracture. For example, horses were found to have a 32% higher chance of sustaining a fracture when racing on a dirt surface compared to a synthetic surface; a 35% higher chance if they had sustained a previous injury during racing and a 47% higher chance was also found for stallions compared to mares and geldings. Furthermore, logistic regression models based on data available only from the period 2009-2013 were used to predict the probability of a Thoroughbred sustaining a fracture for 2014. The 5% of starts that had the highest score in our predictive models for 2014 were found to have 2.4 times (95% CI: 1.9-2.9) higher fracture prevalence than the mean fracture prevalence of 2014. The results of this study can be used to identify horses at higher risk on entering a race and could help inform the design and implementation of preventive measures aimed at minimising the number of Thoroughbreds sustaining fractures during racing in North America.

Risk factors associated with fatal injuries in Thoroughbred racehorses competing in flat racing in the United States and Canada.

OBJECTIVE To identify risk factors associated with fatal injuries in Thoroughbred racehorses in the United States and Canada. DESIGN Retrospective study. ANIMALS 1,891,483 race starts by 154,527 Thoroughbred racehorses at 89 racetracks in the United States and Canada from 2009 to 2013. PROCEDURES Data were extracted from the Equine Injury Database, which contained information for 93.9% of all official flat racing events in the United States and Canada during the 5-year observation period. Forty-four possible risk factors were evaluated by univariate then multivariable logistic regression to identify those that were significantly associated with fatal injury (death or euthanasia of a horse within 3 days after sustaining an injury during a race). RESULTS 3,572 race starts ended with a fatal injury, resulting in a period incidence rate of 1.9 fatal injuries/1,000 race starts. Twenty-two risk factors were significantly associated with fatal injury. Risk of fatal injury was greater for stallions than for mares and geldings and increased as the number of previous nonfatal injuries and race withdrawals and level of competitiveness (eg, horse's winning percentage and race purse) of the horse or race increased. CONCLUSIONS AND CLINICAL RELEVANCE Results identified several risk factors associated with fatal injuries in Thoroughbred racehorses. This information can be used as a guideline for the identification of racehorses at high risk of sustaining a fatal injury and in the design and implementation of preventative measures to minimize the number of fatal injuries sustained by horses competing in flat racing in the United States and Canada.

Evaluation of a novel echocardiographic view for the assessment of the pulmonary artery in dogs.

OBJECTIVES: 1) To describe a novel echocardiographic view (left cranial oblique) for the assessment of the pulmonary artery in dogs 2) To compare this novel view with other standard views. ANIMALS: Prospective inclusion of 48 echocardiograms performed on client-owned dogs. METHODS: Two standard views and the novel view were compared for quality of 2D images and spectral Doppler traces and also for pulmonary annulus diameter and spectral Doppler velocities. Association between view, heart rate and body weight and quality, annulus diameter, pulsed-wave and continuous-wave velocities were analyzed using regression analysis. Agreement between views was assessed by Bland-Altman analysis. Pulsed-wave and continuous-wave velocities were compared using the sign test for medians. RESULTS: Forty-eight studies were undertaken of which thirty-nine were analyzed. The quality of 2D images was associated with view and heart rate. No significant difference was found in quality of spectral Doppler traces between views. Annulus diameter showed significant association with view, heart rate and weight. This measured about 0.26 cm less on one particular view. Spectral Doppler velocities showed no association with view, heart rate or weight. Continuous-wave velocities were significantly higher than pulsed-wave velocities in every view. CONCLUSIONS: The novel left cranial oblique view can be used as an additional tool for the echocardiographic evaluation of the pulmonary artery. The pulmonary annulus diameter was consistently smaller measured from the one standard view compared to both the novel and other standard views. Comparable quality and velocities were obtained for spectral Doppler. Continuous-wave and pulsed-wave modes were not interchangeable.

A genome-wide association study demonstrates significant genetic variation for fracture risk in Thoroughbred racehorses.

BACKGROUND: Thoroughbred racehorses are subject to non-traumatic distal limb bone fractures that occur during racing and exercise. Susceptibility to fracture may be due to underlying disturbances in bone metabolism which have a genetic cause. Fracture risk has been shown to be heritable in several species but this study is the first genetic analysis of fracture risk in the horse. RESULTS: Fracture cases (n = 269) were horses that sustained catastrophic distal limb fractures while racing on UK racecourses, necessitating euthanasia. Control horses (n = 253) were over 4 years of age, were racing during the same time period as the cases, and had no history of fracture at the time the study was carried out. The horses sampled were bred for both flat and National Hunt (NH) jump racing. 43,417 SNPs were employed to perform a genome-wide association analysis and to estimate the proportion of genetic variance attributable to the SNPs on each chromosome using restricted maximum likelihood (REML). Significant genetic variation associated with fracture risk was found on chromosomes 9, 18, 22 and 31. Three SNPs on chromosome 18 (62.05 Mb - 62.15 Mb) and one SNP on chromosome 1 (14.17 Mb) reached genome-wide significance (p < 0.05) in a genome-wide association study (GWAS). Two of the SNPs on ECA 18 were located in a haplotype block containing the gene zinc finger protein 804A (ZNF804A). One haplotype within this block has a protective effect (controls at 1.95 times less risk of fracture than cases, p = 1 × 10(-4)), while a second haplotype increases fracture risk (cases at 3.39 times higher risk of fracture than controls, p = 0.042). CONCLUSIONS: Fracture risk in the Thoroughbred horse is a complex condition with an underlying genetic basis. Multiple genomic regions contribute to susceptibility to fracture risk. This suggests there is the potential to develop SNP-based estimators for genetic risk of fracture in the Thoroughbred racehorse, using methods pioneered in livestock genetics such as genomic selection. This information would be useful to racehorse breeders and owners, enabling them to reduce the risk of injury in their horses.

An online survey of horse-owners in Great Britain.

BACKGROUND: Contingency planning for potential equine infectious disease outbreaks relies on accurate information on horse location and movements to estimate the risk of dissemination of disease(s). An online questionnaire was used to obtain unique information linking owner and horse location to characteristics of horse movements within and outwith Great Britain (GB). RESULTS: This online survey yielded a strong response, providing more than four times the target number of respondents (1000 target respondents) living in all parts of GB. Key demographic findings of this study indicated that horses which were kept on livery yards and riding schools were likely to be found in urban environments, some distance away from the owner's home and vaccinated against influenza and herpes virus. Survey respondents were likely to travel greater than 10 miles to attend activities such as eventing or endurance but were also likely to travel and return home within a single day (58.6%, 2063/3522). This may affect the geographical extent and speed of disease spread, if large numbers of people from disparate parts of the country are attending the same event and the disease agent is highly infectious or virulent. The greatest risk for disease introduction and spread may be represented by a small proportion of people who import or travel internationally with their horses. These respondents were likely to have foreign horse passports, which were not necessarily recorded in the National Equine Database (NED), making the location of these horses untraceable. CONCLUSIONS: These results illustrate the difficulties which exist with national GB horse traceability despite the existence of the NED and the horse passport system. This study also demonstrates that an online approach could be adopted to obtain important demographic data on GB horse owners on a more routine and frequent basis to inform decisions or policy pertaining to equine disease control. This represents a reasonable alternative to collection of GB horse location and movement data given that the NED no longer exists and there is no immediate plan to replace it.

Summary of current knowledge of the size and spatial distribution of the horse population within Great Britain.

BACKGROUND: Robust demographic information is important to understanding the risk of introduction and spread of exotic diseases as well as the development of effective disease control strategies, but is often based on datasets collected for other purposes. Thus, it is important to validate, or at least cross-reference these datasets to other sources to assess whether they are being used appropriately. The aim of this study was to use horse location data collected from different contributing industry sectors ("Stakeholder horse data") to calibrate the spatial distribution of horses as indicated by owner locations registered in the National Equine Database (the NED). RESULTS: A conservative estimate for the accurately geo-located NED horse population within GB is approximately 840,000 horses. This is likely to be an underestimate because of the exclusion of horses due to age or location criteria. In both datasets, horse density was higher in England and Wales than in Scotland. The high density of horses located in urban areas as indicated in the NED is consistent with previous reports indicating that owner location cannot always be viewed as a direct substitute for horse location. Otherwise, at a regional resolution, there are few differences between the datasets. There are inevitable biases in the stakeholder data, and leisure horses that are unaffiliated to major stakeholders are not included in these data. Despite this, the similarity in distributions of these datasets is re-assuring, suggesting that there are few regional biases in the NED. CONCLUSIONS: Our analyses suggest that stakeholder data could be used to monitor possible changes in horse demographics. Given such changes in horse demographics and the advantages of stakeholder data (which include annual updates and accurate horse location), it may be appropriate to use these data for future disease modelling in conjunction with, if not in place of the NED.

A genome-wide association study of osteochondritis dissecans in the Thoroughbred.

Osteochondrosis is a developmental orthopaedic disease that occurs in horses, other livestock species, companion animal species, and humans. The principal aim of this study was to identify quantitative trait loci (QTL) associated with osteochondritis dissecans (OCD) in the Thoroughbred using a genome-wide association study. A secondary objective was to test the effect of previously identified QTL in the current population. Over 300 horses, classified as cases or controls according to clinical findings, were genotyped for the Illumina Equine SNP50 BeadChip. An animal model was first implemented in order to adjust each horse's phenotypic status for average relatedness among horses and other potentially confounding factors which were present in the data. The genome-wide association test was then conducted on the residuals from the animal model. A single SNP on chromosome 3 was found to be associated with OCD at a genome-wide level of significance, as determined by permutation. According to the current sequence annotation, the SNP is located in an intergenic region of the genome. The effects of 24 SNPs, representing QTL previously identified in a sample of Hanoverian Warmblood horses, were tested directly in the animal model. When fitted alongside the significant SNP on ECA3, two of these SNPs were found to be associated with OCD. Confirmation of the putative QTL identified on ECA3 requires validation in an independent sample. The results of this study suggest that a significant challenge faced by equine researchers is the generation of sufficiently large data sets to effectively study complex diseases such as osteochondrosis.

Histopathologic features of distal tarsal joint cartilage and subchondral bone in ridden and pasture-exercised horses.

OBJECTIVE: To determine whether histopathologic characteristics of the osteochondral units of equine distal tarsal joints were associated with exercise history in horses without lameness. SAMPLE POPULATION: 30 cadaver tarsi from horses without lameness and with known exercise history were separated into 3 groups: nonridden, pasture exercise (group P); low-intensity, ridden exercise (group L); and high-intensity, elite competition exercise (group E). PROCEDURES: Standardized sites from the centrodistal and tarsometatarsal joints under went histologic preparation. A grading system was adapted to describe location, depth, and shape of lesions; cellular arrangement; organization at cartilage and subchondral bone (SCB) junctions; and organization of SCB. A high score signified a more severe pathological change than a low score. Exercise groups were compared by calculation of Spearman rank correlations. RESULTS: In the centrodistal joint, lesions were present in groups L and E but only medially. Cellular arrangement scores were higher at the dorsomedial location in group P than in groups L and E. Groups L and E had higher scores than group P for the organization of the cartilage, SCB junctions, and SCB, with higher scores at the dorsomedial location. In the tarsometatarsal joint, lesions were evident across the whole joint surface, with more severe lesions located laterally in all 3 groups. Overall, group E had higher scores for cellular arrangement and SCB organization than groups P and L. CONCLUSIONS AND CLINICAL RELEVANCE: Ridden exercise may increase the risk of osteochondral lesions at distal tarsal sites predisposed to osteoarthritis relative to the risk with nonridden exercise.

External characteristics of the lateral aspect of the hoof differ between non-lame and lame horses.

During a pre-purchase examination (PPE) there is always a debate about how clinical findings of the hoof different from ideal should be interpreted in relation to future lameness risk and/or unsuitability of the horse for the potential purchaser. The objectives of this study were to describe and compare external angular measurements, linear ratios and hoof capsule characteristics of non-lame and lame feet. Photographs of feet from 300 horses with foot pain and 25 non-lame horses were analysed. Hoof wall, heel and coronary band angles and hoof wall length and height, weight-bearing length, coronary band length and height of the coronary band at dorsal and palmar locations were measured and expressed as linear ratios. Mean hoof wall, heel and coronary band angles were larger in lame compared with non-lame feet; only the ratio of dorsal to palmar coronary band heights and the shape of the coronary band were significantly different between lame and non-lame horses. Growth rings were divergent and horn tubules were non-parallel in lameness of >3 months. At a PPE, a larger ratio of dorsal to palmar coronary band heights in one limb may be indicative of previous lameness in that foot. Changes in coronary band shape and divergent growth rings and horn tubules would suggest a longer duration.

Identification of risk factors for lameness in dressage horses.

The aim of this study was to describe the prevalence of illness and lameness at different anatomical sites in registered United Kingdom dressage horses and to identify risk factors for lameness. A questionnaire was sent to all 11,363 registered members of British Dressage in 2005, with one questionnaire assigned per horse. Four multivariable logistic regression models were developed for each section of the questionnaire. A final mixed effects logistic regression model was developed which combined the results from all prior models. Owners reported that 33% of horses had been lame at some time during their career, with 24% of these within the previous 2 years. A number of factors were associated with the occurrence of lameness in the last 2 years, including age, height, indoor arenas, horse-walkers, lunging (as protective), back problems, arenas that become deeper in wet conditions and sand-based arenas. These factors were included as variables in a final model to provide information for selection of horses, development of safer arenas and more effective training regimens to minimise the onset of lameness.

Effect of exercise on thicknesses of mature hyaline cartilage, calcified cartilage, and subchondral bone of equine tarsi.

OBJECTIVE-To investigate effects of exercise on hyaline cartilage (HC), calcified cartilage (CC), and subchondral bone (SCB) thickness patterns of equine tarsi. SAMPLE POPULATION-30 tarsi from cadavers of horses with known exercise history. PROCEDURES-Tarsi were assigned to 3 groups according to known exercise history as follows: pasture exercise only (PE tarsi), low-intensity general-purpose riding exercise (LE tarsi), and high-intensity elite competition riding exercise (EE tarsi). Osteochondral tissue from distal tarsal joints underwent histologic preparation. Hyaline cartilage, CC, and SCB thickness were measured at standard sites at medial, midline, and lateral locations across joints with a histomorphometric technique. RESULTS-HC, CC, and SCB thickness were significantly greater at all sites in EE tarsi, compared with PE tarsi; this was also true when LE tarsi were compared with PE tarsi. At specific sites, HC, CC, and SCB were significantly thicker in EE tarsi, compared with LE tarsi. Along the articular surface of the proximal aspect of the third metatarsal bone, SCB was thickest in EE tarsi and thinnest in LE tarsi; increases were greatest at sites previously reported to undergo peak strains and osteochondral damage. CONCLUSIONS AND CLINICAL RELEVANCE-Increased exercise was associated with increased HC, CC, and SCB thickness in mature horses. At sites that undergo high compressive strains, with a reported predisposition to osteoarthritic change, there was increased CC and SCB thickness. These results may provide insight into the interaction between adaptive response to exercise and pathological change.