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Simple Summary: There is a lack of understanding as to whether the bacteria isolated from swabs of the surface of the lining of broodmares' uteri (endometrial swabs) are present due to infection or contamination, or whether they are, in fact, part of the normal flora. This study aimed to understand this further by investigating endometrial swabs taken from a population of Thoroughbred broodmares and submitted to a laboratory in the UK between 2014 and 2020; by describing bacterial prevalence (the estimated percentage of swabs from which bacteria are isolated); and by evaluating whether bacterial prevalence changed over time or between mares of different ages and with differing amounts of inflammation of the uterine lining. Over the 7-year period, 18,996 endometrial swabs were submitted from 6050 mares on 290 farms. The overall prevalence of bacteria was 35.5%. Beta-hemolytic Streptococcus (17.9%) and E. coli (10.3%) were the most prevalent types of bacteria. The prevalence of bacteria changed over time (between different years in which mares were sampled) and was also impacted by the mare age and by whether there was inflammation of the uterine lining at the time of sampling. Results from this study provide up-to-date prevalence estimates and suggest that the interpretation of Thoroughbred endometrial swab findings is complicated. Determining whether endometrial microbial isolates are pathogens, contaminants, or even part of the "normal" microbiome is extremely complex, particularly given the absence of "gold standard" tests for endometritis. Population-level benchmarking and temporal monitoring can provide novel insights and a wider context to improve understanding. This study aimed to (i) estimate the prevalence of endometrial isolates from swabs of Thoroughbred broodmares in Newmarket, UK between 2014 and 2020; and (ii) evaluate the effects of year, mare age, and cytology findings on isolate prevalence. Generalised linear mixed models with a logit link, both null models and models using year of sampling, mare age, or cytology findings as predictors, were fitted to estimate isolate prevalence. Over the 7-year period, data were available from 18,996 endometrial-swab samples from 6050 mares on 290 premises. The overall isolate prevalence was 35.5% (95% confidence interval (CI) 33.0–37.9), and this varied significantly between years. The most prevalent isolates were β-hemolytic Streptococcus (17.9; 95% CI: 17–19) and E. coli (10.3%; 95% CI: 9.0–11.6). Isolate prevalence increased with mare age except for E. coli isolates, and with increasing category of cytology findings except for α-hemolytic Streptococcus isolates. The results provide novel estimates of isolate prevalence and highlight knowledge gaps around potential complexities in the interpretation of findings. [ABSTRACT FROM AUTHOR]

Simple Summary: Vitamin D biology in equids is unique and poorly understood. Naturally managed (grazing) horses rely on dietary vitamin D2 (ergocalciferol) to provide adequate vitamin D, because endogenous ultraviolet radiation-mediated synthesis of vitamin D3 (cholecalciferol) is ineffective in this species. To test the hypothesis that the management of stabled, non-grazing racehorses is a risk factor for low vitamin D status, the vitamin D status of non-grazing Thoroughbred racehorses in Hong Kong (HK) and grazing Thoroughbred racehorses in the United Kingdom (UK) was compared. The HK horses had lower serum concentrations of 25-hydroxyvitamin D2 (25OHD2) and total 25-hydroxyvitamin D (total 25OHD: the index of vitamin D status), reflecting reduced dietary vitamin D2 intake. These data indicate that HK racehorses required dietary vitamin D3 supplementation to maintain adequate vitamin D status. The inverse relationship between the serum concentrations of 25OHD2 and 25OHD3, previously identified in humans, was observed for the first time in horses, indicating that further study is needed to determine the optimal form of dietary vitamin D supplementation for Thoroughbred racehorses. There is a paucity of data relating to the vitamin D status of racehorses. We hypothesised that the management of racehorses in Hong Kong (HK) predisposes to low vitamin D status unless they receive dietary supplementation. Serum concentrations of 25-hydroxyvitamin D2 (25OHD2), 25-hydroxyvitamin D3 (25OHD3) and total 25-hydroxyvitamin D (total 25OHD) for 79 non-grazing HK racehorses were compared with those for 22 racehorses training in the United Kingdom (UK) that grazed for ≥1 h/d, and for which published data exists. A nested group of 41 HK horses was sampled twice to determine the effect of the duration in HK on vitamin D status. The HK horses had significantly lower serum concentrations of total 25OHD and 25OHD2 than the UK horses; 25OHD2 was undetectable in 15/79 HK sera and serum concentrations of 25OHD2 declined with the duration in HK. The main determinants of vitamin D status were assessed using linear regression; the retained variables were the 25OHD3 concentration and the duration in HK. The inverse relationship between the serum concentrations of 25OHD2 and 25OHD3, previously identified in humans, was observed for the first time in horses. In conclusion, HK racehorses have low serum 25OHD2 and total 25OHD concentrations and rely on D3 supplementation to maintain adequate vitamin D status. Further study is required to determine the optimal form of dietary vitamin D supplementation for Thoroughbred racehorses. [ABSTRACT FROM AUTHOR]

Tongue‐ties (TTs) are used to aid control and aim to conservatively treat upper airway disorders in racehorses. However, welfare concerns have led to their use being banned in other equestrian disciplines. In the United Kingdom, TTs have been reported to be used in approximately 5% of starts. The frequency of their use elsewhere is unknown. The objectives of this retrospective single cohort study were to estimate the frequency of TT use within the Australian Thoroughbred (TB) racing industry, and to describe usage patterns. Data of all Australian TB horse races from 2010 to 2013 calendar years were collected by accessing the Racing Information Services Australia database. Frequency of TT use was calculated, and usage patterns were explored at the start, horse and trainer levels. Between 2010 and 2013, there were a total of 728,678 starts from 62,377 horses prepared by 4927 trainers and that raced on 1453 race dates across 402 venues. Tongue‐ties were used in 21.4% of starts; however, frequency varied according to location, race, trainer and horse. At the horse level, 32.2% wore a TT at least once and 7.6% wore it at every race on record. At the trainer level, 71.3% used TTs in at least one of their horses but only 1.4% used them systematically. The present study concludes that TT use in Australian TB racehorses, during the period 2010–2013, was common and considerably higher than previously reported in the United Kingdom. Most Australian trainers use the device and appear to adapt its usage according to individual horse and race factors. [ABSTRACT FROM AUTHOR]

Background: Up-to-date estimates of early-life morbidity and mortality in Thoroughbreds are lacking., Methods: A birth cohort was established on Thoroughbred stud farms across the UK and Ireland. All veterinary interventions for disease or injury between birth and 18 months of age or leaving the study were recorded. Multilevel Poisson regression models with farm and foal as random effects were fitted to estimate incidence rates., Results: Data were available for 3328 foal-months at risk for 275 foals on seven farms. The overall rates of disease and injury requiring veterinary intervention and mortality were 11.9 cases/100 foal-months at risk (95% confidence interval [CI] 8.6-16.2) and 0.2 cases/100 foal-months at risk (95% CI 0.1-0.4), respectively. Almost half (n = 133/273, 49%, 95% CI 43-55) of the live-born cohort required veterinary intervention for musculoskeletal disease or injury, equating to 5.8 cases/100 foal-months at risk (95% CI 4.1-8.2), predominantly reported as developmental orthopaedic disease (DOD)., Limitations: Convenience sampling of participants may affect the generalisability of the findings., Conclusions: Rates of musculoskeletal disease and injury, in particular DOD, on Thoroughbred stud farms were high. Further work to identify modifiable risk factors and further understanding of the economic impact of these conditions and long-term consequences for musculoskeletal health and performance is required., (© 2023 The Authors. Veterinary Record published by John Wiley & Sons Ltd on behalf of British Veterinary Association.)

It is in the horse racing industry's interest to understand all factors that impact performance to maintain the integrity of the sport. There is some evidence that the start of flat races can affect racehorse performance. However, limited research exists on the explicit effect that waiting at the start and inside starting stalls (also known as starting gates or barriers) has on racehorse finishing position. This study investigated how temporal, behavior and loading related factors associated with the period before the start of the race influences racehorse performance. A cross-sectional design evaluated performance of 546 horses across eight flat race days at Chelmsford City Racecourse in November and December 2020, using televised racing coverage. Time horses spent inside starting stalls, the use of loading aids and jockey behaviors were recorded. Notational analysis was used to determine how much horses sweat and their behavior before, during and after loading. Behavior was categorized using an ethogram adapted from previous published research recording conflict behavior in horses. Horses that spent under 50 s inside starting stalls were more likely to win (p < 0.05) or finish in the top three (p < 0.01). Those showing moderate adverse behavior before loading (p < 0.01) and no adverse behavior inside stalls (p < 0.05) were more likely to win and place first to third, respectively, although behavior during loading had no significant effect. Horses sweating to the point of foaming (p < 0.01) and requiring specialist loaders (p < 0.05) were more likely to win, although the use of other loading aids did not significantly affect performance. Jockeys that pushed their bodyweight forwards in the saddle during loading were significantly more likely to place first to fourth (p < 0.05). A horse's chance of placing first to third was reduced by 15% for every increase in drawn order (p < 0.01; CI:0.77–0.96) and by 59% when the horse spent over 50 s inside stalls (p < 0.05; CI:0.19–0.92). A horse's likelihood of placing decreased by 13% for every year of age (p < 0.05; CI:0.78–0.97) and by a further 17% for each additional horse in the field (p < 0.001; CI:0.00–0.83). Racehorses showing adverse behavior inside stalls were 52% less likely to place (p < 0.05; CI:0.00–0.48). This research demonstrates that the start of flat races can influence performance, highlighting the importance of warm-up protocols and starting gate training to optimise performance. With further longitudinal research, these findings could support adjustments to the rules of racing regarding the start to improve and maintain the integrity of horseracing in the UK. • Racehorse behavior at the start and in starting stalls affects race performance. • Horses inside starting stalls for a shorter time are more likely to win and place. • Willingness to load and loading aids do not seem to affect racehorse performance. • The amount horses sweat prior to racing affects subsequent finishing position. [ABSTRACT FROM AUTHOR]

Enhanced understanding of reasons for, and timings of, mortality in Thoroughbreds prior to entering race training is warranted to provide insight into this population's health status. The aims of this study were to describe pathologies diagnosed at post-mortem (PM) examination in Thoroughbreds aged from birth to 18 months and investigate associations between age and pathology. Reports from a pathology laboratory in Newmarket, UK, were used to identify eligible cases examined between January 2006 and December 2020. Reported pathologies were extracted and categorised where appropriate. Comorbidities and pathogens identified were reported where available. Associations between age and selected pathologies were assessed using logistic regression. Of 144 eligible Thoroughbreds presented for PM, 137 had an available report and pathologist's diagnosis. Congenital defects were most commonly reported (20%; n = 28/137; 95%CI 15–29), 69% of which (n = 19/28; 95%CI 49–82) were conformational manifestations of developmental orthopedic disease (DOD). Pneumonia was an important pathology (14%; n = 20/137; 95%CI 36–53) during the pre-weaning period, where Rhodococcus equi was identified in 50% (n = 10/20; 95% CI 29–70) of cases. Odds of congenital defects (OR 56.6; 95%CI 7.0–460.0; P < 0.001) were significantly greater in horses aged 0–2 days compared to 4–18 months at PM. Odds of pneumonia (OR 4.3; 95%CI 1.1–1.7; P = 0.04) were significantly greater in horses ages 1–4 months compared to 0–2 days at PM. This study shows that conformational manifestations of DOD are an important contributor to perinatal mortality, and that pathologies reported at PM vary with age in young Thoroughbreds. • Post-mortem findings from young Thoroughbreds are described. • The majority of cases presented in the neonatal period. • Congenital limb defects were an important contributor to perinatal mortality. • Rhodococcus equi was an important pathogen, particularly in pre-weaning pneumonia. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to identify risk factors, during racing, associated with imminent fatal distal limb fracture in Thoroughbreds. One hundred and nine cases of fatal distal limb fracture were identified from all 59 UK racecourses over a 2-year period (February 1999–January 2001). Three uninjured control horses were randomly selected from the same race as the case horse. Videos of races in which fractures occurred were viewed using a defined protocol. Fractures in flat races occurred at any time during the race, whereas 74% (45/61) of cases in national hunt type races occurred in the second half of races. More than 75% (79/103) of cases were spontaneous, i.e. there was no obvious external influence such as a fall at a fence or collision with another horse. Sixty-six percent (44/67) of horses, sustaining a forelimb fracture, fractured the forelimb they were using as lead leg at the time of fracture. When case and control horses were compared, horses that were: (a) making good progress through the race, (b) reluctant to start and (c) received encouragement in the final 10s before the time of fracture, were more likely to sustain a fracture. [Copyright &y& Elsevier]

Abstract: 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 50km, 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. [Copyright &y& Elsevier]

Background: Slab fractures of the third carpal bone (C3) are a common injury of Thoroughbred racehorses. Results of arthroscopically guided repair have not been reported since the initial description of the technique in 1986. Additionally, fracture details and racing outcomes in a population of Thoroughbreds racing under UK jurisdiction have not previously been described., Objectives: To report the frequency distribution of C3 slab fractures and to determine the impact on racing performance following arthroscopically guided repair in a population of Thoroughbred racehorses., Study Design: Retrospective case series., Methods: Case records of Thoroughbred racehorses undergoing arthroscopically guided repair of C3 slab fractures at Newmarket Equine Hospital between 2006 and 2015 were retrieved. Radiographs and arthroscopic studies were reviewed. The effect of demography and fracture morphology on racing outcome was evaluated., Results: C3 slab fractures occurred most commonly through the radial facet in a frontal plane (45/71 63.4%). Comminution was identified during arthroscopy in 42/71 (59.2%) fractures and occurred most frequently at the palmar margin of the fracture. Forty-one out of 65 horses (63.1%) raced at least once post-operatively. Females were less likely to return to racing compared to males (P<0.001). Horses that had raced before injury were more likely (OR 4.4, 95% CI 1.4-13.5, P = 0.01) to race after injury compared to horses that were unraced at the time of injury. After injury horses had a small but significant reduction in racing performance., Main Limitations: The series is a preselected population of Thoroughbred racehorses which referring veterinary surgeons considered potential candidates for surgical repair., Conclusion: Fracture configurations can be identified radiographically but is not a reliable predictor of comminution or other intra-articular lesions. Arthroscopy not only directs repair but also identifies and facilitates management of concurrent lesions. The results reported should assist in formulating appropriate prognoses for Thoroughbred horses racing in the UK., (© 2019 EVJ Ltd.)