Identification of modifiable factors associated with owner-reported equine laminitis in Britain using a web-based cohort study approach.

BACKGROUND: Equine laminitis is a complex disease that manifests as pain and lameness in the feet, often with debilitating consequences. There is a paucity of data that accounts for the multifactorial nature of laminitis and considers time-varying covariates that may be associated with disease development; particularly those that are modifiable and present potential interventions. A previous case-control study identified a number of novel, modifiable factors associated with laminitis which warranted further investigation and corroboration. The aim of this study was to identify factors associated with equine laminitis in horses/ponies in Great Britain (GB) using a prospective, web-based cohort study design, with particular interest in evaluating modifiable factors previously identified in the case-control study. RESULTS: Self-selected horse/pony owners in GB submitted initial baseline and follow-up health and management questionnaires for 1070 horses/ponies between August 2014 and December 2016. The enrolled horses/ponies contributed 1068 horse-years at risk with a median of 38 days between questionnaire submissions. Owners reported 123 owner-recognised and/or veterinary-diagnosed episodes of active laminitis using a previously-validated laminitis reporting form. Multivariable Cox regression modelling identified 16 risk/protective factors associated with laminitis development. In keeping with the previous case-control study, a prior history of laminitis (particularly non-veterinary-diagnosed episodes), soreness after shoeing/trimming and weight gain were associated with higher rates of laminitis. There is now strong evidence that these risk factors should be used to guide future recommendations in disease prevention. Factors with some prior evidence of association included breed, steroidal anti-inflammatory administration, transport and worming. The modifiable factors amongst these should be the focus of future laminitis studies. The remainder of the identified factors relating to health, turnout and grazing management and feeding are novel, and require further investigation to explore their relationship with laminitis and their applicability as potential interventions. CONCLUSIONS: This study has demonstrated a temporal relationship between a number of horse- and management-level factors and laminitis, identifying potential interventions and important risk groups for which these interventions would be of particular importance. These results serve as a sound evidence-base towards the development of strategic recommendations for the horse/pony-owning population to reduce the rate of laminitis in GB.

Effects of external ambient temperature at loading, journey duration and flock characteristics on the dead-on-arrival rate in broiler chickens transported to slaughter in Great Britain.

Broiler mortality during transport and lairage, prior to slaughter, has negative welfare and economic implications. Knowledge of the factors affecting the dead-on-arrival (DOA) rate can help identify risk-mitigating strategies. The objectives of this study were to determine the DOA rate in broiler chickens transported to slaughter in Great Britain and associated risk factors. Requested data for all loads of broilers transported to slaughter by 5 large British commercial companies on 57 randomly-selected dates in 2019 were obtained and combined with weather data extracted from the Met Office MIDAS Open database. The DOA rate was described overall and per load using summary descriptive statistics. Mixed-effects Poisson regression was used to evaluate considered flock-, journey- and weather-related risk factors. Results were reported as incidence rate ratios (IRR) and 95% confidence intervals (CI). On the selected dates, 25,476 loads transported 146,219,189 broilers to slaughter. The overall mean DOA rate was 0.08%. The median DOA rate per load was 0.06% (interquartile range 0.03-0.09%; range 0.00-17.39%). Multiple risk factors were identified including loading temperature and catch method. At relative humidity ≤80%, the DOA rate was 16.89 (95% CI 15.25-18.70, P < 0.001) times higher for loads loaded in external ambient temperatures >30.0°C compared to those loaded in temperatures between 10.1°C and 15.0°C. When relative humidity was >80%, there was a 43% increase in DOA rate for loads loaded in temperatures below freezing compared to those loaded in temperatures between 10.1°C and 15.0°C (IRR 1.43, 95% CI 1.35-1.52, P < 0.001). The DOA rate was 32% higher for loads caught mechanically compared to those caught manually (IRR 1.32, 95% CI 1.23-1.42, P < 0.001). The overall DOA rate was lower than that previously reported in Great Britain and for other European countries. Most identified risk factors had a marginal effect, however, loading temperatures >30°C substantially increased DOA rate. Internal thermal environmental conditions were not evaluated. Avoidance of loading during periods of hot weather would improve the welfare of, and reduce economic losses in, broiler chickens.

Associations between physiotherapy findings and subsequent diagnosis of pelvic or hindlimb fracture in racing Thoroughbreds.

REASONS FOR PERFORMING STUDY: Physiotherapists who work in racehorse training yards routinely treat horses' backs and hindquarters and may be able to recognise signs that indicate the presence of (impending) pelvic or hindlimb fracture before it becomes catastrophic. OBJECTIVE: To establish whether physiotherapy assessment findings in Thoroughbred racehorses referred for routine physiotherapy could be predictive of subsequent (within 30 days) pelvic or hindlimb fracture diagnosis. METHODS: Retrospective veterinary and physiotherapy data from a cohort of Newmarket (UK) Thoroughbred racehorses, were used. A case-control study compared physiotherapy assessment findings of racehorses with and without a subsequently diagnosed pelvic or hindlimb fracture. Uni- and multivariable logistic regression was used to investigate and quantify the strength of association between physiotherapy findings and subsequent fracture diagnosis. Statistical significance was set at P<0.05. RESULTS: A total of 513 horses provided 14 fracture cases for analysis. Presence of pelvic bony asymmetry, muscle atrophy of the quarters, reduced reflex movements of dorsi- and/or ventroflexion and spasm or tenderness on palpation of the gluteal muscles were significantly associated with subsequent fracture diagnosis in univariable analysis. Multivariable analysis indicated that horses subsequently diagnosed with pelvic or hindlimb fracture were 11.1 times more likely to show pelvic bony asymmetry, 4.7 times more likely to display muscle atrophy of the quarters and 6.6 times more likely to have spasm or tenderness on palpation of the gluteal muscles than those that were not. CONCLUSIONS: Racehorses presented for physiotherapy that show pelvic bony asymmetry, muscle atrophy of the quarters and/or spasm or tenderness on palpation of the gluteal muscles should alert the physiotherapist to the potential presence of (impending) pelvic or hindlimb fracture. POTENTIAL RELEVANCE: Earlier detection of (impending) pelvic or hindlimb fracture in racing Thoroughbreds could reduce the incidence of catastrophic fractures.

Factors associated with euthanasia in horses and ponies enrolled in a laminitis cohort study in Great Britain.

Euthanasia is a complex topic, with animal owners using multiple factors to shape their decision-making process. Previous epidemiological studies have described causes of equine mortality in specific populations, but there is limited evidence regarding factors contributing specifically to equine euthanasia in Great Britain (GB). This observational study used a prospective cohort design: the objectives were to describe owner-reported reasons for euthanasia, estimate the rate of euthanasia and identify associated factors in horses/ponies enrolled in a web-based epidemiological study of laminitis in GB. Self-selected horse/pony owners submitted regular management and health data over 29 months and reported dates and reasons for euthanasia during this period. The overall incidence of euthanasia was estimated and associated factors were identified using multivariable Cox regression modelling, adjusted for age, with variables retained in the final model if P ≤ 0.05. Data were available for 1070 horses/ponies contributing 1093 horse-years at risk (HYAR), with 80 owner-reported euthanasias. The incidence of euthanasia was 7.3 euthanasias per 100 HYAR (95 % confidence interval [CI] 5.9, 9.1). The most frequently reported health reasons contributing to euthanasia were laminitis-related consequences (25.0 % ; CI 16.8, 35.5 %), colic (21.3 % ; CI 13.7, 31.4 %), non-laminitic lameness (20.0 % ; CI 12.7, 30.1 %) and age-related deterioration, including owner-perceived compromised quality of life (20.0 % ; CI 12.7, 30.1 %). Health-related factors associated with significantly higher rates of euthanasia were colic (hazard ratio [HR] 26.4; CI 12.5, 55.8), pituitary pars intermedia dysfunction (HR 3.0; CI 1.7, 5.4) and lameness due to navicular syndrome (HR 5.9; CI 1.8, 20.0), soft tissue injury (HR 6.5; CI 2.7, 15.6) or laminitis (HR 2.7; CI 1.3, 5.7). Further factors included being pure bred (HR 1.7; CI 1.0, 2.8), female (HR 1.7; CI 1.0, 2.9), having poor owner-perceived hoof quality (HR 2.4; CI 1.1, 5.2), being entirely stabled (HR 5.0; HR 2.1, 12.0), being on loan or under temporary care of the study participant (HR 2.3; CI 1.2, 4.4) and participating in affiliated or professional competitions (HR 5.9; CI 2.4, 14.8). Euthanasia rates were significantly higher in the first two study years compared to the third (P < 0.001). Animals whose owners used the study's custom-designed weight tracker tool had significantly lower rates of euthanasia (HR 0.6; CI 0.3, 0.95). This study has identified a number of, arguably preventable, health-related factors associated with higher rates of euthanasia. Data on owners' decision-making process regarding euthanasia, including emotive and financial impacts, were not recorded but are important contributors to euthanasia that require better understanding.

Bone biomarkers and risk of fracture in two- and three-year-old Thoroughbreds.

The aim of this study was to determine whether bone biomarkers (osteocalcin, PICP, ICTP and CTX-I) could be used to identify 2- and 3-year-olds at increased risk of fracture in the subsequent flat racing season. It was concluded that these bone biomarkers cannot be used to identify 2- and 3-year-olds that sustain a fracture. Whether bone biomarkers have better predictive value in older horses or when measured serially in the same animal remains to be determined.

Ultrasonographic assessment of the superficial digital flexor tendons of National Hunt racehorses in training over two racing seasons.

REASONS FOR PERFORMING STUDY: It is important to ascertain the prevalence of superficial digital flexor tendon (SDFT) injuries and to improve methods of predicting injury in National Hunt (NH) racehorses. OBJECTIVES: To establish: 1) the prevalence of SDFT tendinopathy in NH horses; 2) whether routine ultrasonography can be used to predict SDFT injuries; 3) whether previous tendinopathy predisposes to reinjury; 4) a normal range for the SDFT cross-sectional area (CSA); and 5) the effects of gender, age, background (ex-flat or ex-store), limb, training and rest periods on SDFT CSA. METHODS: Routine ultrasound assessment of the palmar metacarpal soft tissues of 263 NH racehorses was performed on up to 6 occasions over 2 NH racing seasons. RESULTS: The prevalence of SDFT pathology detected using ultrasonography was 24% (n = 148), with a nonsignificant variation between yards of 10-40%. No changes in SDFT CSA or ultrasonographic appearance were detected prior to injury. Older horses had a significantly higher prevalence of SDFT pathology compared to younger horses, and horses with tendinopathy were more likely to suffer an acute injury compared to horses with no evidence of pathology. A reference range for normal CSA measurements was established as 77-139 mm2 at level 4, from 142 horses with no ultrasonographic evidence of SDFT pathology. The CSA of normal horses did not vary significantly with age, limb or over 2 racing seasons, but did with sex and background. CONCLUSIONS: The study confirms that SDFT tendinopathy is common in NH horses, with substantial variation between training yards. Ultrasonography at 3 month intervals did not seem to predict acute SDFT injuries. POTENTIAL RELEVANCE: Variation in the prevalence of tendinopathy between yards suggests that training methods may influence injury rate. It was not possible to predict injury using routine ultrasonography and therefore other methods must be identified. A normal reference range for SDFT CSA is provided.

Descriptive epidemiology of fracture, tendon and suspensory ligament injuries in National Hunt racehorses in training.

REASONS FOR PERFORMING STUDY: While fractures and tendon injuries are known to be important diseases in National Hunt (NH) racehorses during racing, there are no accurate estimates of their incidence in NH training yards. OBJECTIVES: To estimate the incidence of fractures and tendon and suspensory ligament injuries (TLIs) in NH racehorses in training; to describe the injuries incurred and to compare injury incidence rates by horse age, trainer, gender and background (ex-flat vs. ex-store horses). METHODS: Cohort data were collected from 14 UK NH training yards for 2 racing seasons. Daily exercise regimens and details of fractures and TLIs occurring in study horses were recorded. RESULTS: Data were gathered from 1223 horses that spent 9466 months at risk of injury. The fracture incidence rate was 1.1/100 horse months and varied significantly by trainer (P<0.001) but not by gender, age or background. The pelvis and third metacarpal bone (MCIII) were the most common fracture sites, although this varied between racing and training. The TLI incidence rate was 1.9/100 horse months and varied significantly by trainer (P = 0.05) and age (P<0.001) but not by gender or background. However, ex-store horses were significantly more likely to have a TLI on the racecourse than ex-flat horses (P = 0.01). Superficial digital flexor injuries accounted for 89% of all TLIs, the remainder being suspensory ligament injuries. CONCLUSIONS AND POTENTIAL RELEVANCE: Fractures and TLIs are important causes of morbidity and mortality in NH racehorses in training in England. This study provides accurate estimates of their incidence in this population and provides a baseline against which to monitor the effect of future interventions.

Incidence and clinical signs of owner-reported equine laminitis in a cohort of horses and ponies in Great Britain.

BACKGROUND: Previous robust epidemiological studies of equine laminitis have utilised only veterinary-diagnosed episodes of disease, potentially underestimating true disease frequency. OBJECTIVES: To estimate the incidence of, and describe clinical signs associated with, owner-reported active laminitis in horses/ponies, using both veterinary-diagnosed and nonveterinary-diagnosed episodes. STUDY DESIGN: Prospective cohort. METHODS: Data were collected from horse/pony owners in Great Britain between August 2014 and December 2016 using a web-based application. The incidence of owner-reported laminitis was estimated using both first incident and repeat episodes reported during the study period via a previously validated laminitis reporting form. Owner-reported clinical signs present in these episodes were recorded. RESULTS: A total of 1070 horses/ponies contributed 1068 horse-years at risk (HYAR) and 123 active laminitis episodes were reported in 97 animals. Sixty-two of these episodes (50.4%, 95% confidence interval [CI] 41.6, 59.2%) were veterinary-diagnosed and 75.3% (CI 66.7, 83.8%; n = 73) of horses/ponies reported to have laminitis during the study had a previous laminitis history. Overall owner-reported first episode incidence was 9.6 episodes (CI 7.8, 11.7)/100 HYAR, whereas incidence including repeat episodes was 11.5 episodes (CI 9.7, 13.7)/100 HYAR. Laminitis occurred throughout the year with no significant differences between seasonal incidence estimates. Incidence was highest in Connemara and New Forest and lowest in Draught and Cob breed categories. The most prevalent owner-reported clinical signs (≥70%) were difficulty turning and a short/stilted or lame walk. Laminitis was reported in all limbs, however; both forelimbs were most commonly affected (62.9%, CI 54.1, 71.7%; n = 73/116). MAIN LIMITATIONS: Self-selection enrolment of participants may limit generalisability of the findings. CONCLUSIONS: Laminitis remains a considerable year-round welfare issue of horses and ponies, with frequency estimates utilising owner-reported data more representative of the true impact of the disease. The clinical signs reported by horse/pony owners were reflective of those previously described by veterinary surgeons.

Epidemiology of race-day distal limb fracture in flat racing Thoroughbreds in Great Britain (2000-2013).

BACKGROUND: A key focus of the racing industry is to minimise the number of race-day distal limb fractures although no studies have identified risk factors for both fatal and non-fatal distal limb fractures. OBJECTIVE: To determine risk factors for race-day distal limb fractures experienced by Thoroughbred racehorses participating in flat racing in Great Britain (GB). STUDY DESIGN: Retrospective cohort. METHODS: Information was collected from all flat racing starts occurring on GB racecourses between 2000 and 2013, including horse, race, course, trainer and jockey data for each horse start and race-day injury data as reported by on-course veterinarians. Associations between exposure variables and cases of distal limb fracture were assessed using mixed-effects logistic regression analyses using data from all starts, and turf starts only. RESULTS: A total of 806,764 starts and 624 cases of distal limb fracture were included, of which 548,571 starts and 379 cases of distal limb fracture occurred on turf surfaces. In both models, increasing firmness of the going, increasing racing distance and horses in their first year of racing were at a higher risk of distal limb fracture while increasing number of previous race starts were protective. Trainer performance was associated with distal limb fracture. Generally, the risk of distal limb fracture increased with increasing horse age. Starts in selling or claiming races or Group 1, Group 3 or claiming races were at higher odds of distal limb fracture in the all starts and turf models, respectively. MAIN LIMITATIONS: Clinical diagnosis of distal limb fracture and all types of distal limb fracture considered as one outcome. CONCLUSIONS: This study confirmed previously identified risk factors for distal limb fracture including going, race distance and number of horse starts. Novel risk factors were related to trainer and horse performance, and race type. Identification of at risk groups will help inform interventions to reduce distal limb fracture occurrence in flat racing horses.

Multivariable analysis to determine risk factors associated with early pregnancy loss in thoroughbred broodmares.

Early pregnancy loss (EPL) between days 15-65 after breeding has been shown to occur in 7.9% of equine pregnancies with substantial economical, welfare and safety implications. Whilst maternal age has been recognised as an important risk factor in relation to the incidence of EPL, few other risk factors have been conclusively identified. Further, multivariable data analysis of risk factors for EPL is sparse. A prospective cohort investigation of thoroughbred broodmares in the United Kingdom was conducted over the 2013 and 2014 breeding seasons. Information relating to 28 factors including mare, stallion, pregnancy and therapeutic interventions was collected using questionnaires and entered into a custom-designed Microsoft Access database. Mixed effects logistic regression was used to determine risk factors for EPL, including 'mare' as a random effect to account for repeat pregnancies in the same mare. Stallion, stud and veterinarian were also evaluated as random effects. Variables with a p-value of <0.25 in univariable analysis were taken forward for consideration in the multivariable model which was built using a forward stepwise approach. Data were collected on 2245 pregnancies in 1753 mares. Increasing mare age (OR = 1.11, 95% confidence interval (CI) = 1.04, 1.18, p = 0.001), having had one previous foal (OR = 3.52, 95% CI = 1.56, 7.95, p = 0.002) and presence of uterine cysts (OR = 1.76, 95% CI = 1.07, 2.91, p = 0.03) were all associated with increased odds of EPL following multivariable analysis. Increasing day 15/16 scan vesicle size (OR = 0.24, 95% CI = 0.16, 0.38, p < 0.001) and the use of ovulatory induction agents (OR = 0.31, 95% CI = 0.17, 0.55, p < 0.001) were negatively associated with EPL. Stallion, stud and veterinarian were not significantly associated with EPL. Analysis of a subpopulation of 344 multiple (twin and triplet) pregnancies found that the use of flunixin meglumine at the time of manual reduction of a multiple pregnancy resulted in reduced odds of EPL (OR = 0.34, 95% CI = 0.14, 0.84, p = 0.02). Results from this study can be used by stud farm personnel when assessing their broodmare population and by clinicians when deciding upon therapeutic strategies. Additional work can be focused around these risk factors to further our understanding of the pathophysiology of EPL.

Descriptive study of current therapeutic practices, clinical reproductive findings and incidence of pregnancy loss in intensively managed thoroughbred mares.

Therapeutic practices in equine reproductive medicine have dramatically evolved over the last 20 years but current usage is not described. The aims of this study were to provide a description of medication use and clinical findings of reproductive examinations alongside measures of reproductive efficiency in thoroughbreds. A prospective cohort study was conducted in the 2013 and 2014 breeding seasons. Mare and stallion details, information on veterinary interventions and findings of reproductive ultrasound scans were collected using questionnaires and entered into a custom-designed Microsoft Access database. Descriptive summary statistics were derived directly from the database and using Microsoft Excel. Information was collected from 2246 pregnancies in 1754 mares from 29 stud farms. Ovulatory induction agents were used in 91.8% of cases, oestrus induction agents in 38.4% and covering therapies in 62.7%. Intrauterine antimicrobials were used in 49.6% of mares. Single pregnancies accounted for 83.9% of pregnancies, twins for 15.3% and triplets for 0.7%. The overall incidence of pregnancy loss between days 15-42 was 6.4% (95% CI 5.4%, 7.4%) and 1.6% (95% CI 1.1%, 2.1%) between days 43-65. A further 1.3% of pregnancies were lost by October and 4.5% by birth (including stillbirths). Eighty-three percent of all pregnancies resulted in a live foal. In conclusion, there has been a considerable increase in the use of reproductive therapeutics over the last 12 years. Nonetheless, incidence of pregnancy loss and live foal percentages remain essentially unchanged. Risk factor studies are required to determine if the substantial increase in therapeutic usage is conferring positive benefits.

Assessment of horse owners' ability to recognise equine laminitis: A cross-sectional study of 93 veterinary diagnosed cases in Great Britain.

BACKGROUND: Use of owner-reported data could further epidemiological knowledge of equine laminitis. However, owner recognition of laminitis has not previously been assessed. OBJECTIVES: The primary objective was to establish whether cases of owner-suspected laminitis would be confirmed as laminitis by the attending veterinary surgeon. Secondary objectives were to compare owner- and veterinary-reported information from veterinary-confirmed cases of equine laminitis. STUDY DESIGN: Cross-sectional study. METHODS: Twenty-five British veterinary practices were invited to submit laminitis reporting forms (LRFs) for active laminitis cases attended between January 2014 and October 2015; detailing 27 clinical signs, 5 underlying conditions and 7 risk factors associated with laminitis. Owners were invited to independently complete a modified LRF if reason for the veterinary visit was suspicion of laminitis. Differences between paired veterinary and owner LRFs, and between cases where owners did and did not recognise laminitis, were assessed using McNemar's and Fisher's Exact tests, respectively. RESULTS: Veterinary LRFs were received for 93 veterinary-diagnosed laminitis cases. All 51 owner-suspected cases were confirmed by veterinary diagnosis, with the remaining 42 (45.2%) not recognised as laminitis by owners. Undefined lameness, foot abscesses, colic and stiffness were common reasons for owner-requested veterinary visits in owner-unrecognised cases. 'Divergent growth rings' (prevalence difference: +27.3%, P = 0.01) and 'breed type' (prevalence difference: +21.2%, P = 0.04) were more commonly reported by veterinary surgeons in owner-recognised compared to owner-unrecognised cases. 'Difficulty turning', 'shifting weight' and risk factor 'body condition' were more frequently reported by veterinary surgeons whilst 'increased hoof temperature' was reported more frequently by owners. MAIN LIMITATIONS: The limited clinical data restricted statistical inferences regarding the secondary objectives. CONCLUSIONS: All owner-suspected laminitis cases were confirmed upon veterinary examination, showing validity for the inclusion of owner-reported cases in future epidemiological studies. However, failure of laminitis recognition by owners highlights further need for evidence-based education to ensure early disease detection.

Descriptive epidemiology of veterinary events in flat racing Thoroughbreds in Great Britain (2000 to 2013).

BACKGROUND: To date, no large scale studies have reported race-day events requiring veterinary attention in British Thoroughbreds racing on the flat. Quantifying and describing common injuries and health conditions affecting racehorses will enable targeted risk factor analysis aimed at reducing their occurrence. OBJECTIVE: To describe the type and incidence of race-day veterinary events experienced by Thoroughbred racehorses participating in flat racing in the UK. STUDY DESIGN: Retrospective cohort study (2000 to 2013). METHODS: Veterinary events recorded by race-day veterinarians were retrieved and linked to race start data. Race-day veterinary events were described by type, location and anatomical structure(s) affected and whether the outcome was fatal or not. Incidence per 1000 starts was calculated, both overall and by year. Stratified incidence rates were calculated for selected event categories by specific course- and horse-level variables. RESULTS: There were 7993 events experienced by 6727 horses, with an incidence of 9.37 events per 1000 starts. Soft tissue injuries other than tendon and ligament injuries were the most commonly occurring veterinary events (24.1%), followed by gait observations (21.2%) and respiratory conditions (21.2%). In total, 13.8% of events were bone injuries. The incidence of fatality (n = 628) was 0.76 per 1000 starts. Most (485/628, 77.2%) fatal events were bone injuries, 64 were due to cardiac conditions and 54 due to tendon and ligament injuries. All-weather tracks had a higher incidence of veterinary events and fatalities than turf tracks. Firmer (turf) or faster (all-weather) going were associated with a higher incidence of all veterinary events. MAIN LIMITATIONS: Events were based on presumptive, rather than definitive, veterinary diagnosis. CONCLUSION: The most common events experienced by racehorses on race-day were relatively minor and not career-ending. Although more severe bone, joint, tendon and ligament injuries were less common, they had a greater impact on whether the outcome of the event was fatal.

Description of veterinary events and risk factors for fatality in National Hunt flat racing Thoroughbreds in Great Britain (2000-2013).

BACKGROUND: No large-scale studies have described veterinary events occurring in National Hunt (NH) flat racing or investigated risk factors for fatality in this race type. OBJECTIVES: To describe injuries and conditions requiring veterinary attendance on race day and to determine risk factors for racehorse fatality in NH flat racing in Great Britain. STUDY DESIGN: Retrospective cohort study (2000-2013). METHODS: Information from all NH flat races held over the study period, including horse, race and veterinary event report details, was combined. Veterinary events were described by type and anatomical structure(s) affected. Incidence per 1000 starts were calculated for all veterinary events and by event group, and stratified by certain horse- and race-level variables. Risk factors for fatality were determined using multivariable logistic regression modelling. RESULTS: Over the 14-year study period, 544 veterinary events were recorded, providing an overall incidence of 13.0 events per 1000 starts. The most common events were bone injuries (23.5%) and tendon or ligament injuries (16.4%). A fatal outcome was recorded for 117 horses (21.5% of all events), resulting in an incidence of 2.9 deaths per 1000 starts. Odds of fatality were 4.33 (95% confidence interval [CI] 1.59-11.82; P = 0.02) times higher in races restricted to conditional jockeys compared to those that were not. Horses starting in their first race experienced 1.44 (95% CI 1.00-2.08; P = 0.05) times the odds of death compared to those that had raced before. MAIN LIMITATIONS: Classification of veterinary events frequently relied upon presumptive diagnosis. CONCLUSIONS: This study provides a benchmark for the ongoing surveillance of veterinary events in NH flat racing. These results support the phasing out of NH flat races restricted to conditional jockeys and highlight the need for further work to establish why NH flat racing Thoroughbreds competing in their first race are at increased risk for death.

Risk factors for race-day fatality, distal limb fracture and epistaxis in Thoroughbreds racing on all-weather surfaces in Great Britain (2000 to 2013).

The incidence of race-day injuries in Great Britain (GB) is higher on all-weather (AW) surfaces than on turf. However, to date no studies have focused on identifying risk factors for injury specific to AW racing. Therefore, the objective of the current study was to determine risk factors for fatality, distal limb fracture (DLF) and episodes of epistaxis in flat racing Thoroughbreds racing on AW surfaces in GB. Data included all flat racing starts on AW surfaces (n=258,193) and race-day veterinary events recorded between 2000 and 2013. Information on additional course-level variables was gathered during face-to-face interviews with racecourse clerks. Horse-, race- and course-level risk factors for each outcome were assessed using mixed-effects multivariable logistic regression including horse as a random effect. A classification tree method was used to identify potential interaction terms for inclusion in the models. During the study period, there were 233 fatalities resulting in a fatality incidence of 0.90 per 1000 starts; 245 DLF with a resultant DLF incidence of 0.95 per 1000 starts and 410 episodes of epistaxis resulting in an epistaxis incidence of 1.59 per 1000 starts. Risk factors varied for each outcome, although some factors were similar across models including the going, racing intensity, horse age, age at first race start, horse and trainer performance variables. Generally, older horses and those that had started racing at an older age were at higher risk of an adverse outcome, albeit with an interaction between the two variables in the fatality model. Faster going increased the odds of epistaxis and DLF but not fatality. Increasing race distance increased the odds of fatality but reduced the odds of epistaxis. Epistaxis was associated with type of AW surface (Fibresand versus Polytrack®), but DLF and fatality were not. This study provides further evidence of the association between the risk of race-day injuries and fatalities and current age, age at first start, race distance, going and horse performance. These findings provide the racing industry with information to develop strategies to reduce the occurrence of race-day events on AW surfaces.

A case-control study of factors associated with pelvic and tibial stress fractures in Thoroughbred racehorses in training in the UK.

Few epidemiological studies have investigated risk factors for musculoskeletal injury occurring in Thoroughbred racehorses during training, although it is the major cause of wastage in the racing industry. We recently conducted a large-scale epidemiological study to estimate the incidence of fracture in racehorses in training in the UK and to identify associated risk factors. Thirteen racehorse trainers provided data on horses in their care, with daily recording of training information and provision of details on any fractures incurred. Data were collected for 2 years, including two consecutive flat racing seasons (1999 and 2000). This paper describes findings from a nested case-control study investigating factors associated with the occurrence of pelvic and tibial stress fractures in our study population. Cases were identified from the main study and defined as horses with a pelvic or tibial stress fracture, confirmed through routine diagnostic imaging. Randomly selected controls were matched on date of fracture in the case. Age and gender of the horse, its exercise history and training surfaces were examined as explanatory variables. Exercise was quantified as cumulative distances cantered and worked at high speed in 30- and 60-day periods prior to date of fracture in the case. Conditional logistic regression was used to construct multivariable models for the 30- and 60-day periods, respectively. We hypothesised that larger cumulative exercise distances would be associated with an increased risk of pelvic or tibial stress fracture and that different training surfaces would be associated with differences in fracture risk. In the 30-day period, when adjusting for trainer, the risk of pelvic or tibial stress fracture increased with increasing distance cantered, reaching a peak at around 50 km, after which the risk reduced. This trend was not obvious in the 60-day period, with no significant association between exercise distances and risk of stress fracture. Predominant use of one particular sand-based all-weather surface was related to an increased risk of pelvic or tibial stress injury, although this finding should be interpreted with caution. Surface maintenance and construction may play a role; variables that were not considered in the current analyses, which were based on a relatively small number of cases. Trainer was associated with differences in stress fracture risk after adjusting for exercise distances and surface but age and gender were not.

Decision-tree analysis of clinical data to aid diagnostic reasoning for equine laminitis: a cross-sectional study.

The objective of this cross-sectional study was to compare the prevalence of selected clinical signs in laminitis cases and non-laminitic but lame controls to evaluate their capability to discriminate laminitis from other causes of lameness. Participating veterinary practitioners completed a checklist of laminitis-associated clinical signs identified by literature review. Cases were defined as horses/ponies with veterinary-diagnosed, clinically apparent laminitis; controls were horses/ponies with any lameness other than laminitis. Associations were tested by logistic regression with adjusted odds ratios (ORs) and 95% confidence intervals, with veterinary practice as an a priori fixed effect. Multivariable analysis using graphical classification tree-based statistical models linked laminitis prevalence with specific combinations of clinical signs. Data were collected for 588 cases and 201 controls. Five clinical signs had a difference in prevalence of greater than +50 per cent: 'reluctance to walk' (OR 4.4), 'short, stilted gait at walk' (OR 9.4), 'difficulty turning' (OR 16.9), 'shifting weight' (OR 17.7) and 'increased digital pulse' (OR 13.2) (all P<0.001). 'Bilateral forelimb lameness' was the best discriminator; 92 per cent of animals with this clinical sign had laminitis (OR 40.5, P<0.001). If, in addition, horses/ponies had an 'increased digital pulse', 99 per cent were identified as laminitis. 'Presence of a flat/convex sole' also significantly enhanced clinical diagnosis discrimination (OR 15.5, P<0.001). This is the first epidemiological laminitis study to use decision-tree analysis, providing the first evidence base for evaluating clinical signs to differentially diagnose laminitis from other causes of lameness. Improved evaluation of the clinical signs displayed by laminitic animals examined by first-opinion practitioners will lead to equine welfare improvements.

A method for isolating and culturing placental cells from failed early equine pregnancies.

Early pregnancy loss occurs in 6-10% of equine pregnancies making it the main cause of reproductive wastage. Despite this, reasons for the losses are known in only 16% of cases. Lack of viable conceptus material has inhibited investigations of many potential genetic and pathological causes. We present a method for isolating and culturing placental cells from failed early equine pregnancies. Trophoblast cells from 18/30 (60%) failed equine pregnancies of gestational ages 14-65 days were successfully cultured in three different media, with the greatest growth achieved for cells cultured in AmnioChrome™ Plus. Genomic DNA of a suitable quality for molecular assays was also isolated from 29/30 of these cases. This method will enable future investigations determining pathologies causing EPL.

Training-related factors associated with dorsometacarpal disease in young Thoroughbred racehorses in the UK.

REASONS FOR PERFORMING STUDY: Dorsometacarpal disease (DMD) is common in young Thoroughbred (TB) racehorses, often interfering with their training programme. No reports exist on incidence rate or associated risk factors in the UK. OBJECTIVES: To estimate the incidence rate of DMD in TB horses in training for flat racing in the UK and identify associated risk factors, particularly in relation to training regimens. METHODS: Data were drawn from a large prospective study in which TB horses in 13 training yards were monitored for a period of up to 2 years, recording daily training information and details of musculoskeletal injury, including DMD. The incidence of DMD was calculated and survival analysis performed to determine features of the training regimen related to the risk of disease. RESULTS: A total of 335 horses provided 4235 months at risk of DMD. Seventy-nine first episodes were recorded, resulting in an incidence rate of 1.87/100 horse months (95% confidence interval 1.50-2.33). Increasing exercise distances at canter and high speed in short periods (up to 1 month) were associated with an increasing risk of DMD. However, increasing cumulative exercise distances since entering training were associated with a decreasing risk of the disease. CONCLUSIONS: The risk of DMD in young TBs decreases with accumulation of distances exercised at canter and high speed; this reflects the adaptive response of the third metacarpal bone to the loads placed upon it. However, increasing exercise distances in short periods (up to 1 month) increases the risk of DMD, probably as a consequence of microdamage and its associated remodelling response, and should therefore be avoided. POTENTIAL RELEVANCE: Training regimens for young TBs can be adjusted to prevent the occurrence of DMD. Early but gradual introduction of small amounts of high-speed exercise may be beneficial. Canter exercise should be kept minimal on high-speed work days and large amounts of both cantering and high-speed work per week, 2 weeks or per month should be avoided, particularly during the early stages of training, in order to minimise the risk of DMD.

Biochemical markers of bone metabolism and risk of dorsal metacarpal disease in 2-year-old Thoroughbreds.

REASONS FOR PERFORMING STUDY: Dorsal metacarpal disease (DMD) is a common problem in 2-year-old racehorses and results in loss of a significant number of days from training. Biochemical markers of bone cell activity measured early in the training season could have value for identifying 2-year-old Thoroughbred racehorses that develop DMD. OBJECTIVES: To determine the association between serum concentrations of osteocalcin, the carboxyterminal propeptide of type I collagen (PICP) and the carboxyterminal cross-linked telopeptide of type I collagen (ICTP) measured early in the training season and the risk of DMD. METHODS: Blood samples were collected from 165 two-year-old Thoroughbreds during late November/early December. Osteocalcin and PICP were measured as markers of bone formation, and ICTP as a marker of bone resorption. Training and veterinary records for each horse were monitored over the following training/racing season (10 months). Cases were defined as an episode where signs of DMD were sufficiently severe for a horse to miss at least 5 consecutive days of training. Classification tree and logistic regression analysis were used to identify the most important factors suitable for prediction of DMD risk. RESULTS: There were 24 cases of DMD during the season (14.6% cumulative incidence), with an average time to recognition of approximately 6 months (May). The earliest recognised case was in February and the latest in September. Osteocalcin and ICTP concentrations in the early stages of the training season were significantly higher in horses that subsequently developed DMD (P = 0.017 and 0.019, respectively). DMD cases were also significantly older compared to noncases (21.04 vs. 20.44 months, P = 0.023). Using a multivariable logistic regression model, it was possible to postulate a set of diagnostic rules to predict the likelihood of DMD injury during the season. This suggested that horses with ICTP concentrations above 12365 ug/l and older than 20.5 months are 2.6 times more likely to develop DMD. CONCLUSIONS: The measurement of the bone resorption marker ICTP could be useful for identification of 2-year-olds at increased risk of developing DMD. POTENTIAL RELEVANCE: These findings, together with other strategies such as modification of training regimens, e.g. early introduction of short distances of high-speed exercise into the training programme, could help reduce the days lost to training as a result of DMD.