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Summary Background Objectives Study design Methods Results Main limitations Conclusion Short incomplete parasagittal fractures of the proximal phalanx are common injuries described in racehorses and also horses not used for racing. Computed tomographic (CT) features have been described in horses not used for racing, but not in a racehorse population.To describe CT features of short incomplete parasagittal fractures of the proximal phalanx in a group of Thoroughbred racehorses.Retrospective observational study.CT images of 59 Thoroughbred racehorses diagnosed with 60 short incomplete parasagittal fractures of the proximal phalanx examined between January 2014 and February 2023 were reviewed retrospectively. Horse signalment and clinical features were retrieved from hospital records.50/60 fractures were dorsally biased unicortical fractures. Mean proximodistal fracture extension in forelimbs (13.6 mm ± 3.4) was less than in hindlimbs (17.4 mm ± 4.4) (p = 0.0019). There was no difference in fracture extension in the proximodistal direction according to age or gender. Fractures in 2‐year‐olds were shorter in dorsopalmar/−plantar direction (17.4 mm ± 6.3) than in 3‐year‐olds and older horses (21.7 mm ± 7.4) (p = 0.015). Periosteal new bone was present in 91.2% of fractures and endosteal new bone in 75%.Conclusions from this study can only confidently be applied to similar populations of racing Thoroughbred horses.Short incomplete parasagittal fractures of the proximal phalanx in Thoroughbred racehorses most commonly involve only the dorsal cortex and adjacent subchondral and cancellous bone. The distribution of fracture configurations differs from that described in horses not used for racing. [ABSTRACT FROM AUTHOR]

Purpose: To enhance performance in race riding, knowledge of current training workload is required. The objectives of this study were to quantify the physiological demands and profile the muscle activity of jockeys riding track-work. Methods: Ten apprentice jockeys and 48 horses were instrumented with heart-rate monitors, accelerometers, and a surface electromyography BodySuit (recording 8 muscle groups: quadriceps, hamstrings, gluteal, lower back, obliques, abdominal, trapezial, and pectoral) that recorded continuously while riding their normal morning track-work. Data were extracted and time matched into 200-m sections for analysis once the jockey reached steady-state canter (6.9 m·s−1). Results: Jockeys rode a mean (±SD) of 6 (1) horses each morning over 2.5 hours, spending ∼30 minutes at a canter (8.8 [ 0.7] m·s−1), with mean heart rate of 129 (11) beats·min–1 and ratings of perceived exertion representing easy-/moderate-intensity exercise. Mean magnitude of horse (0.17 [0.01] m) and jockey center of mass (0.16 [0.02] m) displacement per stride differed from that of the jockey's head (0.11 [0.01] m, P <.05). The majority of horse oscillation was damped in the upper body with a 3-fold reduction in the medio/lateral and fore/aft planes (P <.05), to minimize jockey head movement. Lower-body muscles absorbed horse motion, with core and upper-body muscles important for postural stabilization. Conclusions: The physiological demands of riding track-work were low, with no evidence of fatigue. Future research on jockeys in races as comparison would identify the specific requirements of a jockey-specific physical conditioning program. [ABSTRACT FROM AUTHOR]

Medial proximal sesamoid bones (PSBs) from Thoroughbred racehorses that did (Case) or did not (Control) experience unilateral biaxial PSB fracture were evaluated for bone volume fraction (BVF), apparent mineral density (AMD), tissue mineral density (TMD), and microdamage in Case fractured, Case contralateral limb intact, and Control bones. A majority of Case bones had a subchondral lesion with high microdamage density, and low BVF, AMD, and TMD. Lesion microdamage and densitometric measures were associated with training history by robust linear regression. Exercise intensity was negatively related to BVF (0.07 ≤ R2  ≤ 0.12) and positively related to microcrack areal density (0.21 ≤ R2  ≤ 0.29) in the lesion; however, in an undamaged site, the relationships were opposite in direction. Regardless of location, TMD decreased with event frequency for both Case and Control, suggesting increased bone remodeling with exercise. Measures of how often animals were removed from active training (layups) predicted a decrease in TMD, AMD, BVF, and microdamage at regions away from the lesion site. A steady-state compartment model was used to organize the differences in the correlations between variables within the data set. The overall conclusions are that at the osteopenic lesion site, repair of microdamage by remodeling was not successful (e.g., lower bone mass, increased damage, and lower mineralization) but that in regions away from the lesion remodeling successfully controlled damage (e.g., higher bone mass, less microdamage, and lower mineralization).

Simple Summary: Pain in the fetlock region is a common cause of lameness in racehorses. Radiological abnormalities of the sagittal ridge of the cannon bone have been previously linked to joint effusion, lameness and reduced sales prices. However, to date, no data exist on the development and progression of these lesions. The aim of this study was to describe the computed tomographic appearance of the sagittal ridge in young racehorses and to document the progression of the detected findings over three assessments in the first year of training and racing. At the first examination, 40 yearlings underwent computed tomographic examination of both front fetlocks. Re-examinations were performed twice, approximately six months apart on 31 and 23 horses, respectively. Computed tomographic recordings were analysed with particular attention to changes in bone density and to lesions consistent with osteochondrosis (developmental abnormality). An increase in bone density of the sagittal ridge occurred in the first six months of training. Lesions consistent with osteochondrosis could decrease in size or resolve during the first year of training. In this population of racehorses these changes were not associated with lameness. Metacarpophalangeal joint region pain is a common cause of lameness in racehorses. Radiological abnormalities in the sagittal ridge (SR) of the third metacarpal bone have been associated with joint effusion, lameness and reduced sales prices. The aims were to describe computed tomographic (CT) appearance of the SR in racehorses, and to document the progression of these findings over three assessments. Forty yearlings were enrolled at the first examination (time 0). Re-examinations were performed twice, approximately six months apart on 31 (time 1) and 23 (time 2) horses, respectively. Computed tomographic examinations of both metacarpophalangeal regions were performed with the horses in a standing position. Computed tomographic reconstructions were analysed subjectively and objectively. The mean Hounsfield Unit values (Hus) of eight radial segments and location, size and shape of hypoattenuating lesions were recorded. Mean Hus at time 1 were higher than at time 0. There was no difference between mean HU at times 1 and 2. The mean HU values of the dorsal half were higher in the right forelimbs and in fillies. Hypoattenuation was identified in 33/80 (41.3%) limbs at time 0, in 22/62 (35.5%) limbs at time 1 and in 14/46 (30.4%) limbs at time 2. All hypoattenuations were located in the dorsodistal aspect of the SR. The most common shapes were hypoattenuating lesions elongated proximodistally and those extending towards trabecular bone. An increase in attenuation of the SR occurred in the first six months of training. Hypoattenuating lesions could decrease in size and could resolve during early training. In this population, these lesions were not associated with lameness. [ABSTRACT FROM AUTHOR]

Objective: To validate a novel technique to measure limb stiffness in a clinical setting. Animals: Three horses and three ponies owned by the Royal Veterinary College. Procedures: Limb stiffness indices for both forelimbs were first derived using the gold standard of kinematic analysis. Using the same animals, limb stiffness indices were then calculated using portable floor scales to record weight and an electrogoniometer to record changes in metacarpophalangeal joint angle. The two techniques were then assessed for correlation and repeatability. Results: The repeatability of limb stiffness measurement using the novel clinical tool was considered to be good based on a small coefficient of variation (5.70%). The correlation of limb stiffness as derived by both methods was high (r = 0.78, p < 0.01). Limb stiffness was positively correlated with the mass of the subject (r = 0.85, p < 0.01), with heavier horses having greater limb stiffness. Clinical relevance: This study has compared a novel method to measure distal forelimb stiffness non-invasively in a clinical setting to kinematic analysis in six equids. It has demonstrated that limb stiffness increases in a linear fashion with body mass consistent with the role of forelimbs providing energy storage. Because in vivo limb stiffness has been shown previously to alter with injury to the superficial digital flexor tendon, it is hypothesized that this technique will offer a practical technique for the clinician to assess limb stiffness in clinical cases. Further study will be necessary to determine its clinical usefulness in such cases. [ABSTRACT FROM AUTHOR]

Copyright of Revista Cientifica de la Facultade de Veterinaria is the property of Universidad del Zulia, Facultad de Ciencias Veterinarias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Distal extremity lesions are prevalent in racehorses and cause mild–to–severe lameness, adversely affecting the racing life of horses. This study aimed to determine the incidence of distal extremity lesions in racehorses, to clinically and radiologically assess those lesions. The study included 158 limbs from 140 horses with distal extremity lesions among 282 horses of different breeds, age and sex that were presented to Equine Hospital of the Directorate of Diyarbakir, Turkey, Hippodrome with various clinical complaints during a racing season. Following anamnesis, the horses were clinically examined and lameness was localised. In cases where the lameness could not be localised upon physical examination, regional anaesthesia was performed, followed by radiological assessments based on radiographs acquired from different positions. Clinical and radiological examination revealed that 84.17% of the cases occurred in the forelimb and 15.82% in the rear limb, and the lesions in the forelimb were mostly located in the carpal joint (26.58%), metacarpus (25.31%) and metacarpophalangeal joint (23.41%), whereas those in the rear limb were located in the tarsal joint (7.5%). Therefore, the lesions in the forelimbs were more prevalent than those in the rear limbs of the affected racehorses. Radiography remains a satisfactory imaging technique for the diagnostic imaging of distal limb injuries in horses owing to its cost–effectiveness.

ObjectiveTo validate a novel technique to measure limb stiffness in a clinical setting.AnimalsThree horses and three ponies owned by the Royal Veterinary College.ProceduresLimb stiffness indices for both forelimbs were first derived using the gold standard of kinematic analysis. Using the same animals, limb stiffness indices were then calculated using portable floor scales to record weight and an electrogoniometer to record changes in metacarpophalangeal joint angle. The two techniques were then assessed for correlation and repeatability.ResultsThe repeatability of limb stiffness measurement using the novel clinical tool was considered to be good based on a small coefficient of variation (5.70%). The correlation of limb stiffness as derived by both methods was high (r = 0.78, p

Simple Summary: Most catastrophic musculoskeletal injuries in Thoroughbred racehorses involve the fetlock region. Magnetic resonance imaging (MRI) and computed tomography (CT) aid detection of potentially serious abnormalities, before they become identifiable on radiographs. However, no data exist in live horses regarding how these injuries develop and progress. The aim of this study was to describe MRI, CT and radiographic findings in the front fetlock of Thoroughbreds entering racehorse training. Forty non-lame yearlings underwent low-field MRI, CT and radiographic examinations of both front fetlocks. The most common finding was a lesion consistent with osteochondrosis (developmental abnormality) in the cannon bone. Of the 33 lesions seen in CT images, about two-thirds were detected on radiographs. In the majority of the cannon bones, there was some increase in bone density and enlargement of vascular channels, consistent with the bone's response to exercise. Small defects in the joint surface were seen in both the cannon bone (11 limbs) and the long pastern bone (19 limbs) which may indicate developmental abnormalities or subtle injuries. In conclusion, variants or abnormalities occur in the cannon bone in the fetlock region of yearling Thoroughbreds and may reflect early changes as the bone adapts to exercise or changes secondary to osteochondrosis. Most catastrophic injuries in Thoroughbred racehorses involve the fetlock. There is no description of comparative imaging in Thoroughbreds entering racehorse training. The aim was to describe MRI, CT and radiographic findings in the metacarpophalangeal joint of non-lame Thoroughbred yearlings. Forty Thoroughbreds underwent low-field MRI, fan-beam CT and radiographic examinations of both metacarpophalangeal joints. Images were assessed subjectively. A hypoattenuating lesion of the sagittal ridge of the third metacarpal bone (McIII) was identified in 33/80 limbs in CT reconstructions. Cone-shaped mineralisation in the sagittal ridge was detected in MR images (n = 17) and in CT images (n = 5). Mild hyperattenuation was common in trabecular bone in the dorsomedial (36/80) and palmarolateral (25/80) metacarpal condyles in CT reconstructions. A focal lesion in the subchondral bone was seen in the proximal phalanx (n = 19) and in McIII (n = 11). Enlarged vascular channels were detected in the metacarpal condyles in 57/80 limbs and in the proximal sesamoid bones in all limbs. Signs of bone modelling are seen in yearling Thoroughbred fetlocks. Sagittal ridge lesions were common and are likely associated with osteochondrosis or other developmental osteochondral defects. Focal lesions in the subchondral bone of McIII and proximal phalanx can indicate developmental abnormalities or subtle subchondral bone injuries. [ABSTRACT FROM AUTHOR]

Copyright of Equine Veterinary Journal is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Metacarpophalangeal joint region pain is a common cause of lameness in racehorses. Radiological abnormalities in the sagittal ridge (SR) of the third metacarpal bone have been associated with joint effusion, lameness and reduced sales prices. The aims were to describe computed tomographic (CT) appearance of the SR in racehorses, and to document the progression of these findings over three assessments. Forty yearlings were enrolled at the first examination (time 0). Re-examinations were performed twice, approximately six months apart on 31 (time 1) and 23 (time 2) horses, respectively. Computed tomographic examinations of both metacarpophalangeal regions were performed with the horses in a standing position. Computed tomographic reconstructions were analysed subjectively and objectively. The mean Hounsfield Unit values (Hus) of eight radial segments and location, size and shape of hypoattenuating lesions were recorded. Mean Hus at time 1 were higher than at time 0. There was no difference between mean HU at times 1 and 2. The mean HU values of the dorsal half were higher in the right forelimbs and in fillies. Hypoattenuation was identified in 33/80 (41.3%) limbs at time 0, in 22/62 (35.5%) limbs at time 1 and in 14/46 (30.4%) limbs at time 2. All hypoattenuations were located in the dorsodistal aspect of the SR. The most common shapes were hypoattenuating lesions elongated proximodistally and those extending towards trabecular bone. An increase in attenuation of the SR occurred in the first six months of training. Hypoattenuating lesions could decrease in size and could resolve during early training. In this population, these lesions were not associated with lameness.

Catastrophic musculoskeletal injuries (CMI) in horses are associated with both too little and too much high-speed exercise. In order to advise trainers on training and management strategies that minimize the risk of musculoskeletal injury (MSI), a better understanding of how training practices affect MSI in racehorses is needed. Data from prospective studies relating training data and MSI are complicated by the gradual development of pathology and the effect of this on the ability of horses to train consistently prior to the identification of an injury. To circumvent this, 66 Australian Thoroughbred trainers were surveyed on their intended training practices, including rest, pre-training, and race-fit practices. Associations between intended training practices and catastrophic and non-catastrophic race day MSI outcomes in two-year-old and mature (≥three-year-old) horses were assessed using multivariable negative binomial regression models. The incidence of two-year-old race day MSI was lower for trainers who preferred shorter times (weeks) to trial, less time in fast work pre-trial (p = 0.003), shorter, more frequent rest periods (p

For the safe and simple screening of equine leg bones, we applied an ultrasonic axial transmission (AT) technique to an equine bone sample with a weak bucked shin. Both experimental and simulation studies have been conducted. To simulate by the finite-difference time-domain method, a digital model of the equine leg bone was fabricated. The experimental and simulation results showed a similar tendency. The obtained apparent wave velocities in the axial direction were almost constant in the healthy part but strongly fluctuated in the bucked shin part because of the small surface irregularities. The standard deviation values of the wave velocities in the bucked shin parts were large. These results indicate that a weak bucked shin in the equine leg bone may be screened clinically by a simple evaluation of velocity fluctuation using the AT technique. [ABSTRACT FROM AUTHOR]

Anabolic androgenic steroids are synthetic substances related to the male sex hormones (androgens). These agents promote the growth of skeletal muscle (anabolic effects) and the development of male sexual characteristics (androgenic effects). Anabolic steroids have been illegally used for many years as performance‐enhancing drugs in human, equine, and canine sports and as growth promoters in livestock reared to provide meat for human consumption. The analytical challenge to developing effective means of control within these fields has been exacerbated by the reported endogenous nature of some of these steroids. Anabolic steroids have been employed extensively in equine practice over the past 50 years. Their usefulness is largely dependent on subjective opinions, as only minimal studies investigating pharmacodynamics have been carried out in horses. Therefore, their use will vary markedly between practitioners depending on their personal experiences and pressures by trainers to use them. They form part of rational therapy in a variety of conditions. In addition to their use for increasing muscle mass, they are used to varying extents in the raising of yearlings and in the training and racing of horses with the view of improving performance. The use of these agents is prohibited in the horseracing industry by the Association of Racing Commissioners International (ARCI), International Federation of Horseracing Authorities (IFHA), and Fédération Equestre Internationale (FEI). [ABSTRACT FROM AUTHOR]

Simple Summary: The main goal in selecting racehorses for breeding is usually monetary earnings, and animals that earn the highest amounts of money are usually selected for breeding. These animals are not always the fastest on the racecourse because there are several competitions where the animals were faster but the prize money for the winners was lower. This practical strategy meant that the fastest racehorses were not always selected for breeding. The present study evaluated several traits through the results of heritability, genetic correlations and trends. Results from this study indicate that when we evaluated the earnings trait together with other important traits, the best values were observed. The selection process for the best sires and dams should be performed through two stages: first, by evaluating the animals that obtained the best times and, in the second stage, by evaluating the animals that had the highest monetary earnings. The design of breeding programs using the earnings trait in conjunction with another racing performance trait can change the results observed and improve genetic gains for speed racing Quarter Horses around the world. The aim of this study was to evaluate the sprint racing performance of Quarter Horses in Brazil. Estimating genetic parameters, trends and correlations were obtained by single- and two-trait analyses using Bayesian inference (earnings to 2 years of equestrian age, best time and time class at distances of 301 m and 402 m). The data comprised a period of 38 equestrian years (1978 to 2015) with 23,482 sprint race records from 5861 animals. The heritability estimates were of low to moderate magnitude, ranging from 0.10 to 0.37 (single-trait) and from 0.15 to 0.41 (two-traits), and the repeatability was 0.31 to 0.46. The additive, residual and phenotypic correlations between earnings to 2 years of equestrian age and the other traits (best time and time class in distances 301 m and 402 m) were high (−0.95, −0.96, 0.69 and 0.92), low (−0.29, −0.37, 0.26 and 0.27) and moderate (−0.41, −0.47, 0.37 and 0.47), respectively. There is a positive genetic trend for all traits considered. However, evaluation of the last 10 equestrian years (2006 to 2015) showed negative trends (genetic loss) and trends close to zero (genetic stagnation). The design of breeding programs using the earnings trait in conjunction with other racing performance traits can enhance changes in the genetic gains as a whole in speed-racing Quarter Horses. These findings suggest that the traits studied should be included in breeding selection programs for racing Quarter Horses. [ABSTRACT FROM AUTHOR]

Copyright of Equine Veterinary Journal is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Simple Summary: Back pain in Thoroughbred racehorses is frequent and significantly decreases their athletic performance. The most common thoracolumbar alteration in Thoroughbreds is Kissing Spines Syndrome (KSS). The objective of the current study was to evaluate and compare soft tissue response to high-intensity laser therapy (HILT) by measuring changes in skin surface temperature and longissimus dorsi muscle tone, located in the thoracolumbar back area, in Thoroughbreds with back pain diagnosed with and without KSS. The Thoroughbreds were divided into two groups, those with KSS (n = 10) and those without KSS (n = 10). A single laser treatment of the longissimus dorsi muscle (on the left side, between the fifteenth thoracic and the second lumbar vertebrae) was performed. Thermographic examination and palpation were repeated before and after HILT to assess changes in skin surface temperature, muscle tone and pain response. In both groups, HILT was associated with an average skin surface temperature increase of 2.5 °C and a palpation score reduction of 1.5 points, without any differences between the groups. In conclusion, HILT was found to be a safe and supportive treatment method for longissimus dorsi muscle pain and discomfort as assessed by digital palpation in Thoroughbreds. The results of the present study are encouraging, but further studies with larger samples, a longer follow-up period and comparisons with placebo control groups are needed to draw a more valid conclusion. The reason for undertaking this study was to investigate soft tissue response to high-intensity laser therapy (HILT) by measuring changes in skin surface temperature and longissimus dorsi muscle tone in the thoracolumbar back area in Thoroughbreds with back pain and diagnosed with and without Kissing Spines Syndrome (KSS). Thoroughbreds aged 3–4 years with clinically presented back pain underwent a radiological examination (to assess a lack or presence of KSS) and longissimus dorsi muscle palpation (to assess muscle tone and pain degree). The subjects were divided into two groups, those with KSS (n = 10) and those without KSS (n = 10). A single HILT treatment on the longissimus dorsi muscle, on the left side, was performed. Thermographic examination and palpation were repeated before and after HILT to assess changes in skin surface temperature and muscle pain response. In both groups, HILT caused a significant increase in skin surface temperature of 2.5 °C on average and a palpation score reduction of 1.5 degrees on average (p = 0.005 for both measurements), without differences in any outcome measures between the groups. Furthermore, the correlation between changes in the average skin surface temperature and the average palpation scores in horses with and without KSS were negative (rho = 0.071 and r = −0.180, respectively; p > 0.05). The results of the present study are encouraging, but further studies with larger samples, a longer follow-up period and comparisons with placebo control groups are needed to draw a more valid conclusion. [ABSTRACT FROM AUTHOR]

Equine tibial fractures are relatively infrequent in racing and non‐racing sport horses, but limitations in successful treatment of tibial fractures in adult horses result in relatively high mortality compared with other musculoskeletal injuries. The aetiology of tibial fracture can be classified into two general categories: traumatic impact or fatigue failure. Tibial stress fractures, also known as fatigue fractures, are often rated as the second most common stress fracture in racing Thoroughbreds; young age, early stage in race training, and initiation of training after a period of rest are the reported risk factors. Both impact and fatigue fracture propagation are dependent on the magnitude of force applied and on the local composition/alignment of mineralised collagen in the tibial lamella. Extensive research has characterised the pattern of strain distribution and stress remodelling within the equine tibia, but in vivo measurement of load and angular moments are currently not feasible. Further research is warranted to correlate biomechanical theory of tibia fatigue fracture propagation with current histopathological data. Preventative measures for fatigue fractures aim to optimise diagnostic efficiency, reduce the interval between injury and diagnosis and modify racing and training conditions to reduce non‐specific fracture risk. Treatment options for complete tibial fractures in adult horses are limited, but with careful case selection, successful outcomes have been reported after open reduction and internal fixation. On the other hand, tibial stress fractures and minimally displaced incomplete fractures are typically treated conservatively and have good prognosis for athletic recovery. This review aims to describe the current literature regarding tibial fracture aetiology, prevalence, risk factors, fracture biomechanics, treatment, prognosis and prevention. [ABSTRACT FROM AUTHOR]

Background: High serum γ‐glutamyl‐transferase (GGT) activity syndrome in racehorses has been associated with maladaption to exercise. Investigation of affected horses before and immediately after standard exercise may provide critical insight into the syndrome's pathophysiology. Objectives: To investigate blood biomarker changes in actively competing racehorses with high GGT activity associated with an exercise challenge. Study design: Case–control study. Methods: High GGT case (age: 2–3 years) and normal GGT control (age: 2–7 years) pairs (3 Thoroughbred, 4 Standardbred pairs) at least 3 months into their training/racing season were included. Horses with a recent history of high GGT activity (≥50 IU/L) without additional biochemical evidence of liver disease were identified by veterinarians. Horses were tested again in the week prior to a planned exercise challenge to confirm persistent increases in GGT activity. Controls from the same stable with similar training/racing intensity and serum GGT activity ≤36 IU/L were matched with each case. Blood samples were obtained immediately before, 15 and 120 min after exercise. Pre‐exercise serum samples were analysed for baseline select serum chemistries, selenium and vitamin E concentrations. Cortisol concentration and markers of oxidative status were measured in serum or plasma for all time points. Individual serum bile acid and coenzyme Q10 concentrations, plasma lipid mediator (fatty acids, oxylipids, isoprostanes) concentrations and targeted metabolomics analyses were performed using liquid chromatography‐mass spectrometry. Serum viral PCR for equine hepaci‐ and parvovirus was performed in each animal. Results: Cases had higher baseline concentrations of total glutathione, taurocholic acid, cortisol and cholesterol concentrations and higher or lower concentrations of specific oxylipid and isoprostane mediators, but there were no case‐dependent changes after exercise. Main limitations: Small sample size. Conclusions: Results indicated that glutathione metabolism was altered in high GGT horses. Enhanced glutathione recycling and mild cholestasis are possible explanations for the observed differences. [ABSTRACT FROM AUTHOR]

Among the causes of lameness in horses, those of arthrogenic origin, especially synovitis, which can progress to advanced joint damages, such as osteoarthritis, are of importance in clinical practice. In this study, we aimed to evaluate the early diagnosis, treatment, and treatment outcomes of acute synovitis, which occur frequently in English and Arabian horses during the racing season. A total of 167 joints of 126 horses (39 English and 87 Arabian Thoroughbred) aged 2-4 years diagnosed with acute synovitis were evaluated using clinical, radiographic, and ultrasonographic examinations. The treatment protocol of horses consisted of cold hydrotherapy and light pressure bandage initially, followed by rest for 10 days and controlled walking only, a single dose of phenylbutazone, and intra-articular corticosteroid and hyaluronic acid injection. Although functional improvement was observed in all the horses following this treatment, subsequent relapses occurred in 22 cases. Consequently, it is important to comply with this treatment program and plan the treatment of acute synovitis in the early period. Controlled gaits, rather than absolute immobility, increase the success of treatment, especially in horses at rest. In addition, it is important to ensure that the relevant joint is not overburdened after the rest period in order to avoid relapses.

Simple Summary: The association between poor performance and respiratory disease in Thoroughbred racehorses that do not have a structural abnormality of the respiratory tract is often based on anecdotal evidence. We examined peer reviewed publications to determine if there was scientific evidence to link conditions such as inflammation of the airways, asthma, tracheal mucous, and exercise-induced pulmonary haemorrhage (EIPH) with decreased athletic performance. This is a complex field and studies have yielded conflicting results as to the impact of such conditions on performance. For example, some investigators found a significant association between poor racing performance and low-grade EIPH and mild to moderate asthma. In contrast, others have suggested that they may represent a normal response to training and the stabling environment. The key outcome of the review was that there is a dearth of studies unequivocally linking non-structural airway disease with poor performance, and there is a lack of an internationally harmonised approach to the assessment of racehorse performance. Improved investigations providing better quality evidence would facilitate comparison across studies, increase our understanding of the conditions associated with poor performance, safeguard horse welfare, and assist trainers to achieve their goals. The association between poor performance and respiratory disease in Thoroughbred racehorses that do not have a structural abnormality of the respiratory tract, is often based on anecdotal evidence. The objective of this scoping review was to examine the scientific evidence for such associations. Publications were selected based on a search of three databases (PubMed, Scopus, and CAB Direct), in English and without date restriction, followed by a screening process to exclude non-relevant papers, duplicates, and reviews. This process identified 996 publications of which 20 were analysed using the Quality in Prognosis Studies (QUIPS) tool. The results indicated that the evidence supporting the relationship between proposed diagnostic indicators and poor performance is variable. There is a need for better quality evidence. In particular, there are conflicting reports relating to the impact of equine asthma and EIPH on athletic performance. Furthermore, a lack of standardisation in the measurement of racehorse performance makes it difficult to compare findings from different studies. The industry would benefit from high-level guidance concerning the design of controlled performance studies in Thoroughbred racehorses to collect comprehensive data and facilitate targeted interventions. [ABSTRACT FROM AUTHOR]

Objective Thoroughbred horses have been bred exclusively for racing in England for a long time. Additionally, because horse racing is a global sport, a healthy leisure activity for ordinary citizens, and a high-value business, systematic racehorse breeding at the population level is a requirement for continuous industrial development. Therefore, we established genomic evaluation system (using prize money as horse racing traits) to produce spirited, agile, and strong racing horse population Methods We used phenotypic data from 25,061 Thoroughbred horses (all registered individuals in Korea) that competed in races between 1994 and 2019 at the Korea Racing Authority and constructed pedigree structures. We quantified the improvement in racehorse breeding output by year in Korea, and this aided in the establishment of a high-level horse-fill industry. Results We found that pedigree-based best linear unbiased prediction method improved the racing performance of the Thoroughbred population with high accuracy, making it possible to construct an excellent Thoroughbred racehorse population in Korea. Conclusion This study could be used to develop an efficient breeding program at the population level for Korean Thoroughbred racehorse populations as well as others.

Most catastrophic injuries in Thoroughbred racehorses involve the fetlock. There is no description of comparative imaging in Thoroughbreds entering racehorse training. The aim was to describe MRI, CT and radiographic findings in the metacarpophalangeal joint of non-lame Thoroughbred yearlings. Forty Thoroughbreds underwent low-field MRI, fan-beam CT and radiographic examinations of both metacarpophalangeal joints. Images were assessed subjectively. A hypoattenuating lesion of the sagittal ridge of the third metacarpal bone (McIII) was identified in 33/80 limbs in CT reconstructions. Cone-shaped mineralisation in the sagittal ridge was detected in MR images (n = 17) and in CT images (n = 5). Mild hyperattenuation was common in trabecular bone in the dorsomedial (36/80) and palmarolateral (25/80) metacarpal condyles in CT reconstructions. A focal lesion in the subchondral bone was seen in the proximal phalanx (n = 19) and in McIII (n = 11). Enlarged vascular channels were detected in the metacarpal condyles in 57/80 limbs and in the proximal sesamoid bones in all limbs. Signs of bone modelling are seen in yearling Thoroughbred fetlocks. Sagittal ridge lesions were common and are likely associated with osteochondrosis or other developmental osteochondral defects. Focal lesions in the subchondral bone of McIII and proximal phalanx can indicate developmental abnormalities or subtle subchondral bone injuries.

Simple Summary: In the equine diet, iron comes from both roughage and concentrate, as well as often being supplemented with the expectation that it will improve performance and health. This is commonly done in the racehorse industry. To determine iron consumption in this population of horses, a survey of 120 U.S. Thoroughbred trainers, representing 1978 Thoroughbreds from various regions of the U.S., was conducted. Racehorses were fed an average of 3900 mg of iron per day from hay and grain alone. This exceeds the recommendations put forth by the 2007 Horse NRC of 0.8 mg/kg BW or 400 mg for a 500 kg working horse. Supplements increased the daily average intake by an additional 500 mg Fe. Despite some equine nutritionists suggesting excess dietary Fe may be a contributing factor in the development of insulin resistance (IR), there was not one case of IR in any of the trainer's Thoroughbred horses. Given the excessive iron provided to the horses in this study, it is unlikely dietary iron is an independent causative factor of IR. Racehorses are often supplemented extra iron with the expectation that the iron will improve overall performance and health. A survey of 120 U.S. Thoroughbred trainers, representing 1978 Thoroughbreds from various regions of the U.S., was conducted to determine the average amount of dietary iron fed to Thoroughbred racehorses per day. Survey results indicated racehorses were fed an average of 3900 mg of iron per day from hay and grain alone. This exceeds the 0.8 mg/kg BW or 400 mg for a 500 kg working horse that the NRC 2007 recommends per day. Supplements increased the daily average intake of iron by an additional 500 mg Fe. Some equine nutritionists propose that excess dietary iron may be a causative factor in insulin resistance (IR). However, the occurrence of IR in Thoroughbred racehorses is very rare. This study did not find one confirmed veterinary diagnosis of IR in any of the surveyed trainers' Thoroughbred horses, whether racing, on a layoff, or retired. Given the iron content in these diets easily exceeds the NRC minimum daily requirements, it seems unlikely that dietary iron is an independent causative factor in IR. [ABSTRACT FROM AUTHOR]

Simple Summary: The study of non-pharmacological products that could have a beneficial action on the respiratory system of the horse may have a great impact on the welfare and performance of equine athletes. As a matter of fact, young racehorses can be affected by a mild–moderate form of equine asthma (MEA), that can reach a prevalence of 80%, and pharmacological treatments during racing days are almost always forbidden. This study aimed to evaluate the efficacy of the administration of a feed supplement, composed of several nutraceutical herbs, in the treatment of lower airway inflammation. This product was administered to seven racehorses with MEA, while five horses were used as control. After 21 days, horses treated with the supplement showed a lower degree of clinical signs and lower mucus accumulation in the trachea, compared to controls. For this reason, the supplement was shown to be effective in controlling lower airway inflammation, and its use as an adjunctive treatment for MEA may deserve to be evaluated. Mild–moderate equine asthma (MEA) is a chronic inflammatory disorder of the lower airways of the horse, characterized by tracheal mucus accumulation, cough and poor performance. The therapeutic approach is based on pharmacological treatment and environmental management. Moreover, the efficacy of the administration of antioxidant molecules has been reported. The aim of the present study was to evaluate the effect of the administration of a commercial nutraceutical supplement, composed of several herbal extracts, on lower airway inflammation in racehorses. Twelve Thoroughbreds affected by MEA were selected. All horses underwent a clinical examination with assignment of a clinical score, airway endoscopy and cytological examination of bronchoalveolar lavage fluid. In seven horses, the supplement was administered for 21 days in association with environmental changes, while in five horses only environmental changes were performed. All procedures were repeated at the end of the study. Data concerning the clinical score, the endoscopic scores and the cytology at the beginning and at the end of the study were statistically compared. Data showed a significant reduction (p < 0.0156) of the clinical score and a significant reduction (p < 0.0156) of the tracheal mucus score. The results showed the beneficial effect of the supplement on mild–moderate lower airway inflammation, probably due to its antioxidant activity. [ABSTRACT FROM AUTHOR]

Simple Summary: To achieve optimal performance and low injury occurrence in horse racing, it is important to understand hoof–surface interactions. This study measured hoof accelerations in retired Thoroughbred racehorses as they galloped over turf and artificial surfaces in four shoeing conditions (aluminium, barefoot, steel and GluShu), using hoof-mounted accelerometers. During hoof landing, accelerations were increased for hindlimbs and leading limbs and on turf compared to the artificial surface. Barefoot hooves experienced the lowest impact accelerations and contrasted most with steel. During the propulsive stage of the stride, accelerations at "foot-off" were increased for low stride times, particularly in the hindlimbs, and on the artificial track. Increased impact accelerations on turf and in shod conditions could be detrimental to health and have implications for musculoskeletal injuries, whereas increased foot-off accelerations on the artificial surface may reflect this surface returning energy to the hoof and aiding propulsion, which could confer a performance benefit. Further work is needed to relate these findings to injury risk and racing outcomes specifically, particularly in racehorses galloping at top speeds. The athletic performance and safety of racehorses is influenced by hoof–surface interactions. This intervention study assessed the effect of eight horseshoe–surface combinations on hoof acceleration patterns at impact and foot-off in 13 galloping Thoroughbred racehorses retired from racing. Aluminium, barefoot, GluShu (aluminium–rubber composite) and steel shoeing conditions were trialled on turf and artificial (Martin Collins Activ-Track) surfaces. Shod conditions were applied across all four hooves. Tri-axial accelerometers (SlamStickX, range ±500 g, sampling rate 5000 Hz) were attached to the dorsal hoof wall (x: medio-lateral, medial = positive; y: along dorsal hoof wall, proximal = positive; and z: perpendicular to hoof wall, dorsal = positive). Linear mixed models assessed whether surface, shoeing condition or stride time influenced maximum (most positive) or minimum (most negative) accelerations in x, y and z directions, using ≥40,691 strides (significance at p < 0.05). Day and horse–rider pair were included as random factors, and stride time was included as a covariate. Collective mean accelerations across x, y and z axes were 22–98 g at impact and 17–89 g at foot-off. The mean stride time was 0.48 ± 0.07 s (mean ±2 SD). Impact accelerations were larger on turf in all directions for forelimbs and hindlimbs (p ≤ 0.015), with the exception of the forelimb z-minimum, and in absolute terms, maximum values were typically double the minimum values. The surface type affected all foot-off accelerations (p ≤ 0.022), with the exception of the hindlimb x-maximum; for example, there was an average increase of 17% in z-maximum across limbs on the artificial track. The shoeing condition influenced all impact and foot-off accelerations in the forelimb and hindlimb datasets (p ≤ 0.024), with the exception of the hindlimb impact y-maximum. Barefoot hooves generally experienced the lowest accelerations. The stride time affected all impact and foot-off accelerations (p < 0.001). Identifying factors influencing hoof vibrations upon landing and hoof motion during propulsion bears implication for injury risk and racing outcomes. [ABSTRACT FROM AUTHOR]

The speed at which a racehorse can reach when its heart rate is 200 beats per minute (bpm) is called the V200. Researchers have found that racehorses who performed better at higher levels of V200 were more likely to succeed without injury. Therefore, researchers consider exercise to be the preferred method of assessment of muscle training. The THR100 represents the time it takes for the racehorse’s heart rate to decrease from the V200 and stabilize to 100 bpm at the end of the race. When the racehorse’s muscle cells switch to an aerobic mode at maximal effort, the THR100 stabilizes for a short period of time, though this stabilization can vary by horse breed and race. We examined parameters such as post-exercise V200, THR100, general blood parameters and blood lactate dynamics of Mongolian racehorses during a dressage event. Mongolian horses’ V200 averaged at around 46.2 km/h, and their THR100 averaged at around 11.8 minutes. At the beginning and end of the exercise, hematocrit (5.7%) and granulocytes (11.1%) were increased, whereas lymphocytes (9.7%) decreased. Also, blood lactate concentrations decreased steadily when measured in intervals of 0, 15, and 30 min to 16.2, 10.4, and 4.5 mmol/l, respectively. [ABSTRACT FROM AUTHOR]

The maximum galloping speeds of racehorses during a race are influenced by the functional performance of the ground ('going') amongst other factors. For turf racecourses in Britain, the ground is descriptively classified and numerically quantified on the morning of a race meeting by the clerk of the course and subsequently published to assist decision making. Importantly, this includes deciding whether a horse should or should not run. The going is also assessed and classified during the meeting by racing analysts using the normalized winning times from each race result. Differences between going assessments are regularly reported, therefore this study aimed to evaluate whether an alternative method of measuring going could better predict going measured from performances. Measurement and performance data from 25 flat and 25 jump meetings were compared using linear and nonlinear regression models. A continuous two-phase polynomial model for cushioning was found to be the best predictor of performance going for all 50 meetings (adjusted r 2 =0.819, P<0.001). As cushioning can provide a going related indicator of the forces that the horse will experience at gallop, this measurement may be useful when evaluating racecourse going. This initial model suggests that there is little performance advantage at maximal galloping speeds above a cushioning value of approximately10 kN, possibly due to changes in limb contact timings to manage limb forces limits as the ground becomes firmer. An expansion of objective measurements of going that relate to performance across a wider geographic region, if not internationally are needed to confirm this limit., Competing Interests: Declaration of competing interest None of the authors has any financial or personal relationships that could inappropriately influence or bias the content of the paper., (Copyright © 2024. Published by Elsevier Inc.)

Objective: Levamisole is a regulated substance sometimes administered to racehorses to treat equine protozoal myelitis. Metabolites include compound II, aminorex, and pemoline. Aminorex and pemoline are Horseracing Integrity and Safety Authority-banned substances. Previous studies have examined single doses of the drug. This study examined the disposition of levamisole after 7 days of dosing., Animals: 6 healthy Thoroughbred geldings., Methods: Horses were treated with 500 mg (approx 0.91 to 1 mg/kg) of compounded levamisole hydrochloride paste PO every 12 hours for a total of 13 doses over 7 days. Serum and urine samples were analyzed for levamisole and its metabolites over a 28-day period., Results: The terminal half-life of levamisole in serum was variable between horses. Following the last dose of levamisole on day 7, serum levamisole levels took 3 to 14 days (days 10 to 21) to fall below the limit of detection (LOD) in 5 of 6 horses. Serum from 1 horse remained over LOD on the last testing day (day 28). In urine, following the final dose (day 7), levamisole was below LOD on day 13 (6 days after final dose) and aminorex was below LOD on day 10 (3 days after final dose). Compound II was above LOD in 4 of 5 horses sampled on the last sampling day (day 28)., Clinical Relevance: Levamisole and its metabolites can be detected for variable lengths of time in horses, with detection lasting for days to weeks following multiple doses. This study supports the Racing Medication and Testing Consortium Advisory on levamisole, which suggests that clearance sample testing should be conducted on treated horses to verify elimination of levamisole and its metabolites.

The aim of this study was to evaluate the sprint racing performance of Quarter Horses in Brazil. Estimating genetic parameters, trends and correlations were obtained by single- and two-trait analyses using Bayesian inference (earnings to 2 years of equestrian age, best time and time class at distances of 301 m and 402 m). The data comprised a period of 38 equestrian years (1978 to 2015) with 23,482 sprint race records from 5861 animals. The heritability estimates were of low to moderate magnitude, ranging from 0.10 to 0.37 (single-trait) and from 0.15 to 0.41 (two-traits), and the repeatability was 0.31 to 0.46. The additive, residual and phenotypic correlations between earnings to 2 years of equestrian age and the other traits (best time and time class in distances 301 m and 402 m) were high (−0.95, −0.96, 0.69 and 0.92), low (−0.29, −0.37, 0.26 and 0.27) and moderate (−0.41, −0.47, 0.37 and 0.47), respectively. There is a positive genetic trend for all traits considered. However, evaluation of the last 10 equestrian years (2006 to 2015) showed negative trends (genetic loss) and trends close to zero (genetic stagnation). The design of breeding programs using the earnings trait in conjunction with other racing performance traits can enhance changes in the genetic gains as a whole in speed-racing Quarter Horses. These findings suggest that the traits studied should be included in breeding selection programs for racing Quarter Horses.

Introduction: Upper airway endoscopy of thoroughbred (TB) yearlings is commonly used in an attempt to predict laryngeal function (LF) and its impact on future race performance. The aim of this study was to determine if different grading systems and laryngeal grades were correlated with future performance. Materials and Methods: Postsale endoscopic recordings were obtained from an Australian TB yearling sale during a four‐year period from 2008 to 2011. Horses were included if they had a diagnostic postsale video endoscopic recording and raced within Australia. Recordings were graded using the Havemeyer system and subsequently recategorised according to the Lane scale and two condensed scales. Performance data were sourced from Racing Australia and comparisons were made between groups. Results: A total of 1244 horses met the inclusion criteria. There were no significant differences in sex or sales price between groups. There were no significant differences in the number of starts or wins between groups for any grading system. For the condensed Havemeyer scale, horses with intermediate LF were separated into two groups. Significant differences in earnings were found between 'normal' and 'abnormal' (P = 0.02) and 'intermediate‐low' and 'abnormal' grades (P = 0.03). There were no significant differences between horses with 'intermediate‐high' and 'abnormal' grades (P = 0.40). No significant differences were found between the two intermediate grades (P = 0.60) or between horses with normal LF and either 'intermediate‐low' or 'intermediate‐high' grades (P = 0.99). Discussion: Resting LF in Australian yearling TBs assessed using a condensed Havemeyer grading scale had some predictive value for future racing performance. This information should be considered when performing yearling endoscopic examinations. [ABSTRACT FROM AUTHOR]

Among the causes of lameness in horses, those of arthrogenic origin, especially synovitis, which can progress to advanced joint damages, such as osteoarthritis, are of importance in clinical practice. In this study, we aimed to evaluate the early diagnosis, treatment, and treatment outcomes of acute synovitis, which occur frequently in English and Arabian horses during the racing season. A total of 167 joints of 126 horses (39 English and 87 Arabian Thoroughbred) aged 2-4 years diagnosed with acute synovitis were evaluated using clinical, radiographic, and ultrasonographic examinations. The treatment protocol of horses consisted of cold hydrotherapy and light pressure bandage initially, followed by rest for 10 days and controlled walking only, a single dose of phenylbutazone, and intra-articular corticosteroid and hyaluronic acid injection. Although functional improvement was observed in all the horses following this treatment, subsequent relapses occurred in 22 cases. Consequently, it is important to comply with this treatment program and plan the treatment of acute synovitis in the early period. Controlled gaits, rather than absolute immobility, increase the success of treatment, especially in horses at rest. In addition, it is important to ensure that the relevant joint is not overburdened after the rest period in order to avoid relapses. [ABSTRACT FROM AUTHOR]

ABSTRACT: Objectives: Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae have become a cause for great concern. Although some studies have reported the prevalence of ESBL-producing bacteria and ESBL-encoding genes in horses worldwide, the genetic structure surrounding the ESBL gene has not been analysed in detail. In the present study, we isolated two ESBL-producing Escherichia coli strains from diseased racehorses in Japan and demonstrated the mechanisms underlying the acquisition of their antimicrobial resistance (AMR) genes. Methods: Two ESBL-producing E. coli strains (E148 and E189) were isolated from the heart and liver of horses with endocarditis and sepsis in 2014 and 2016, respectively, in Japan. Complete genomic sequences of the two strains were analysed using a PacBio RSII sequencer. Antimicrobial susceptibility testing was performed by the agar dilution method. Results: The two isolates possessed a chromosomal AMR gene cluster containing blaCTX-M-1 that was similar to the pEQ1 plasmid found in E. coli isolated from a racehorse in the Czech Republic. In one of the two strains, tandem duplication of the 16-kb region containing blaCTX-M-1 and a class 1 integron, which occurred via IS26-mediated recombination, increased minimum inhibitory concentrations (MICs) associated with the duplicated AMR genes. Conclusion: Chromosomal blaCTX-M-1 possibly derived from the pEQ1 or pEQ1-like plasmid was found in Japanese equine E. coli isolates. In Japanese strains, many AMR genes containing blaCTX-M-1 and the class 1 integron are highly accumulated in one region on the chromosome, and the AMR of E. coli was enhanced via the IS26-mediated duplication of the AMR gene cluster.

Simple Summary: High-intensity laser therapy (HILT) is becoming an increasingly popular form of physiotherapy for tendon injuries. This short communication paper discusses the photothermal effects of HILT on the superficial digital flexor tendon of the hindlimb in clinically healthy racehorses. A thermographic assessment of the surface temperature change in the superficial digital flexor tendon was performed before and immediately after high-intensity laser therapy. The results indicate a statistically significant increase after treatment. These findings may be helpful in determining the optimal HILT parameters needed for treating tendon injuries. The aim of the present study was to assess the photothermal effects of high-intensity laser therapy (HILT) on the superficial digital flexor tendon (SDFT) of the hindlimb in racehorses. It was conducted on 18 clinically healthy thoroughbreds that were subjected to thermographic examination to measure surface temperature changes in the SDFT. This was performed before and immediately after HILT. This revealed statistically significant differences in the temperature of the skin surface overlying the flexor tendons (p < 0.001). The surface temperature of the area examined was higher by an average of 3.5 °C after HILT, compared with the temperature measured before HILT. Our results prove that HILT has a photothermal effect in treating soft tissue. This finding can be helpful in determining the appropriate parameters for monitoring the short- and long-term effects of HILT. [ABSTRACT FROM AUTHOR]

Background: Characteristics and outcomes after surgical repair of third carpal bone (C3) slab fractures involving both radial and intermediate facets in racing Quarter Horses are unknown. Objectives: To describe the pre‐ and intraoperative characteristics of C3 slab fractures of both radial and intermediate facets in Quarter Horses and to report on the long‐term outcomes after internal fixation. Study design: Retrospective case series. Methods: Case records were collected from racehorses with C3 slab fractures between 2008 and 2020. Inclusion criteria required arthroscopic‐guided repair of C3 slab fractures involving both radial and intermediate facets in Quarter Horses. Routine C3 slab fractures (single facet), fractures in other breeds or those repaired with other techniques were excluded. Outcomes were obtained by standardised questionnaire. Data were presented as mean ± SD or as proportions with 95% confidence interval (CI). Results: Of 22 Quarter Horses with C3 slab fractures involving both radial and intermediate facets, 91% (CI 79%‐100%; n = 20) were collapsing and 91% (CI 79%‐100%; n = 20) had avulsion of the medial palmar intercarpal ligament. Articular cartilage erosion and osteochondral fracture of the radial carpal bone was observed in 91% (CI 79%‐100%; n = 20) and 41% (CI 20%‐62%; n = 9) cases respectively. At 5.5 ± 3.9 years after surgery, 86% (CI 72%‐100%; n = 19) were alive and used for breeding or retirement. Of 18 horses with follow‐up >1 year, 39% (CI 16%‐61%; n = 7) resumed some athletic activity. Main limitations: Cases were referred specifically for surgical repair and horses with fractures considered too severe for surgical intervention or euthanasia at owner request were not included. Questionnaire responses are susceptible to recall bias. Conclusions: Horses with C3 slab fractures of both radial and intermediate facets that are repaired have a favourable prognosis for retirement, breeding and potentially low‐level athletic activity. [ABSTRACT FROM AUTHOR]

Background: Exercise induced pulmonary haemorrhage (EIPH) is an important condition of horses performing high intensity exercise, with reported prevalence among racehorses of up to 95%, based on the detection of blood on tracheobronchoscopy. Previously identified risk factors include age, sex, season, race type, years spent in racing and lower airway inflammation. Objectives: To estimate the prevalence of EIPH in British National Hunt racehorses as indicated by two outcome measures: presence of tracheal blood on tracheobronchoscopy, and presence of moderate‐large (significant) proportions of haemosiderophages in tracheal wash (TW) fluid; and to identify training‐related risk factors for these indicators of EIPH. Study design: Prospective longitudinal study. Methods: Data from tracheobronchoscopy and TW cytology were analysed using univariable and multivariable mixed‐effects logistic regression. Results: 1184 observations, from 177 horses, were analysed. The prevalence of tracheal blood was 7.2% (95%CI: 5.8, 8.8) and significant haemosiderophages in TW fluid was 36% (95%CI: 33.3, 38.8). Increased time in training was significantly associated with increased odds of EIPH. For each additional year spent in training the odds of tracheal blood and presence of significant proportions haemosiderophages increased approximately 1.5‐fold (OR = 1.5; 95%CI: 1.1‐2.0; P =.005; and OR = 1.5; 95%CI: 1.3, 1.8; P <.001, respectively). Current inflammation was associated with previous haemorrhage, but not current haemorrhage. Main limitations: There are no standardised measures for quantification of TW cytological parameters for EIPH diagnosis. Few horses were examined following jumping. Recent racing dates were not included in analysis. Conclusions: Increasing time in training was a risk factor for both indicators of EIPH. Current inflammation was associated with previous haemorrhage, but not current or future haemorrhage, suggesting that haemorrhage leads to inflammation but not that inflammation leads to haemorrhage. Overall, our findings are consistent with the capillary stress failure theory of EIPH. The development of standardised measures for TW cytological diagnosis of EIPH is warranted. [ABSTRACT FROM AUTHOR]

Desmitis of the oblique distal sesamoidean ligaments (ODSL) is caused by hyperextension of the metacarpophalangeal/metatarsophalangeal joint and has been described as a significant cause of lameness in racehorses. In this study, three Thoroughbred racehorses (age range: 3-6 years) were diagnosed with desmitis of the forelimb ODSL using standing low-field magnetic resonance imaging (sMRI). Radiography and ultrasonography were inconclusive with regard to a definitive diagnosis. For all horses, the sMRI characteristics included increased signal intensity within the medial ODSL on T1-weighted gradient echo, T2-weighted fast spin echo and short tau inversion recovery fast spin echo images, which use a fat suppression technique. Effusion of the digital flexor tendon sheath was also clearly visible on sMRI. Following rest and controlled exercise for roughly 3 months, two horses successfully returned to racing within 5 months. Our findings support the use of sMRI for diagnosing ODSL injuries in Thoroughbred racehorses.

Background: High‐serum γ‐Glutamyl Transferase (GGT) activity has been associated with and thought to be a marker of maladaptation to training and possibly poor performance in racehorses, but the cause is unknown. Objectives: To investigate possible metabolic and infectious causes for the high GGT syndrome. Study design: Pilot case‐control study and nested case‐control study. Methods: The case‐control study in 2017 included 16 horses (8 cases and 8 controls with median [range] serum GGT 82 [74‐148] and 22 [19‐28] IU/L, respectively) from the same stable. In 2018, similar testing was performed in a nested case‐control study that identified 27 case (serum GGT 50 ≥ IU/L)‐control pairs from three stables for further testing. Serum liver chemistries, selenium measurements, viral PCR and metabolomics were performed. Results: No differences were found in frequency of detection of viral RNA/DNA or copy numbers for equine hepacivirus (EqHV) and parvovirus‐hepatitis (EqPV‐H) between cases and controls. Mild increases in hepatocellular injury and cholestatic markers in case vs control horses suggested a degree of liver disease in a subset of cases. Metabolomic and individual bile acid testing showed differences in cases compared with controls, including increased abundance of pyroglutamic acid and taurine‐conjugated bile acids, and reduced abundance of Vitamin B6. Selenium concentrations, although within or above the reference intervals, were also lower in case horses in both studies. Main limitations: Observational study design did not allow us to make causal inferences. Conclusions: We conclude that high GGT syndrome is likely a complex metabolic disorder and that viral hepatitis was not identified as a cause for this syndrome in this cohort of racehorses. Our results support a contribution of oxidative stress and cholestasis in its pathophysiology. [ABSTRACT FROM AUTHOR]

The reason for undertaking this study was to investigate soft tissue response to high-intensity laser therapy (HILT) by measuring changes in skin surface temperature and longissimus dorsi muscle tone in the thoracolumbar back area in Thoroughbreds with back pain and diagnosed with and without Kissing Spines Syndrome (KSS). Thoroughbreds aged 3–4 years with clinically presented back pain underwent a radiological examination (to assess a lack or presence of KSS) and longissimus dorsi muscle palpation (to assess muscle tone and pain degree). The subjects were divided into two groups, those with KSS (n = 10) and those without KSS (n = 10). A single HILT treatment on the longissimus dorsi muscle, on the left side, was performed. Thermographic examination and palpation were repeated before and after HILT to assess changes in skin surface temperature and muscle pain response. In both groups, HILT caused a significant increase in skin surface temperature of 2.5 °C on average and a palpation score reduction of 1.5 degrees on average (p = 0.005 for both measurements), without differences in any outcome measures between the groups. Furthermore, the correlation between changes in the average skin surface temperature and the average palpation scores in horses with and without KSS were negative (rho = 0.071 and r = −0.180, respectively; p > 0.05). The results of the present study are encouraging, but further studies with larger samples, a longer follow-up period and comparisons with placebo control groups are needed to draw a more valid conclusion.

The association between poor performance and respiratory disease in Thoroughbred racehorses that do not have a structural abnormality of the respiratory tract, is often based on anecdotal evidence. The objective of this scoping review was to examine the scientific evidence for such associations. Publications were selected based on a search of three databases (PubMed, Scopus, and CAB Direct), in English and without date restriction, followed by a screening process to exclude non-relevant papers, duplicates, and reviews. This process identified 996 publications of which 20 were analysed using the Quality in Prognosis Studies (QUIPS) tool. The results indicated that the evidence supporting the relationship between proposed diagnostic indicators and poor performance is variable. There is a need for better quality evidence. In particular, there are conflicting reports relating to the impact of equine asthma and EIPH on athletic performance. Furthermore, a lack of standardisation in the measurement of racehorse performance makes it difficult to compare findings from different studies. The industry would benefit from high-level guidance concerning the design of controlled performance studies in Thoroughbred racehorses to collect comprehensive data and facilitate targeted interventions.

Background: Tibial fractures cause ~3% of racehorse deaths. Pre‐existing stress fractures have been associated with multiple racing and training fractures, but not complete tibial fractures. Objectives: To describe racehorse tibial fractures and compare signalment and exercise histories of affected and control racehorses. Study design: Retrospective analysis of necropsy reports. Methods: Racehorses that had a complete tibial fracture (1990‐2018) were retrospectively reviewed. Signalment and exercise histories of affected horses were compared to 1) racehorses that died because of non‐tibial musculoskeletal injuries or 2) non‐musculoskeletal cause and 3) age, sex, event‐matched control racehorses. Tibial fracture prevalence was described relative to California racehorses that had at least one official work or race. Age, sex and limb distributions were compared between affected and control horses (Chi‐square, Fisher's Exact test). Exercise history data were reduced to counts and rates of official high speed works, races and layups (periods without an official high speed work or race >60 days). Variables were compared among groups using matched logistic regression (P ≤.05). Results: Tibial fractures in 115 horses (97% unilateral; 50% left, 47% right) occurred most commonly during training (68%) and in 2‐ to 3‐year‐old horses (73%). Fractures were predominantly comminuted (93%), diaphyseal (44%) and oblique (40%). Of 61 cases examined for callus, 64% had periosteal callus associated with fracture, most commonly in proximal (65%) and distal diaphyseal (27%) locations. Of 28 racehorses with known exercise history, 57% never raced and 36% had a layup. Affected horses had fewer official‐timed works and events (official high speed works and races), number of active days and accumulated less distance in events and works (P <.05) than control horses. Main limitations: Retrospective review of necropsy reports by multiple pathologists over 28 years. Conclusions: Tibial fractures were associated with pre‐existing stress fracture early in career. Most fractures were associated with proximolateral stress fractures. [ABSTRACT FROM AUTHOR]

Musculoskeletal injuries remain a global problem for the Thoroughbred racing industry and there is conflicting evidence regarding the effect of age on the incidence of injuries. The ideal time to commence race training is strongly debated, with limited supporting literature. There is also conflicting evidence regarding the effect of high-speed exercise on musculoskeletal injuries. There is a strong interest in developing training and management strategies to reduce the frequency of injuries. The types of musculoskeletal injuries vary between 2-year-old and older horses, with dorsal metacarpal disease the most common injury in 2-year-old horses. It is likely that risk factors for injury in 2-year-old horses are different than those for older horses. It is also likely that the risk factors may vary between types of injury. This study aimed to determine the risk factors for musculoskeletal injuries and dorsal metacarpal disease. We report the findings of a large scale, prospective observational study of 2-year-old horses in Queensland, Australia. Data were collected weekly for 56-weeks, from 26 trainers, involving 535 2-year-old Thoroughbred racehorses, 1, 258 training preparations and 7, 512-weeks of exercise data. A causal approach was used to develop our statistical models, to build on the existing literature surrounding injury risk, by incorporating the previously established causal links into our analyses. Where previous data were not available, industry experts were consulted. Survival analyses were performed using Cox proportional hazards or Weibull regression models. Analysis of musculoskeletal injuries overall revealed the hazard was reduced with increased exposure to high-speed exercise [Hazard ratio (HR) 0.89, 95% Confidence Interval (CI) 0.84, 0.94, p < 0.001], increased number of training preparations (HR 0.58, 95% CI 0.50, 0.67, p < 0.001), increased rest before the training preparation (HR 0.89, 95% CI 0.83, 0.96, p = 0.003) and increased dam parity (HR 0.86, 95% CI 0.77, 0.97, p = 0.01). The hazard of injury was increased with increasing age that training commenced (HR 1.13, 95% CI 1.06, 1.19, p < 0.001). Analyses were then repeated with the outcome of interest dorsal metacarpal disease. Factors that were protective against dorsal metacarpal disease and musculoskeletal injuries overall included: increased total cumulative distance (HR 0.89, 95% CI 0.82, 0.97, p = 0.001) and total cumulative days exercised as a gallop (HR 0.96, 95% CI 0.92, 0.99, p = 0.03), the number of the training preparations (HR 0.43, 95% CI 0.30, 0.61, p < 0.001). The age that training commenced was harmful for both dorsal metacarpal disease (HR 1.17, 95% CI 1.07, 1.28, p < 0.001 and overall musculoskeletal injuries.). The use of non-ridden training modalities was protective for dorsal metacarpal disease (HR 0.89, 95% CI 0.81, 0.97, p = 0.008), but not musculoskeletal injuries overall. The male sex increased the hazard of DMD compared to females (HR 2.58, 95% CI 1.20, 5.56, p = 0.02), but not MSI overall. In summary, the hazard of musculoskeletal injury is greatest for 2-year-old horses that are born from uniparous mares, commence training at a later age, are in their first training preparation, have undertaken little high-speed exercise or had limited rest before their training preparation. The hazard of dorsal metacarpal disease is greatest for 2-year-old horses that are males, commence training at a later age, are in their first training preparation, have undertaken little high-speed exercise or had limited use of non-ridden training modalities. Close monitoring of these high-risk horses during their training program could substantially reduce the impact of MSI. Furthermore, an understanding of how training methodologies affect the hazard of MSI facilitates modification of training programs to mitigate the risk impact of injury. The strengths of this study include a large sample size, a well-defined study protocol and direct trainer interviews. The main limitation is the inherent susceptibility to survival bias.

Mild–moderate equine asthma (MEA) is a chronic inflammatory disorder of the lower airways of the horse, characterized by tracheal mucus accumulation, cough and poor performance. The therapeutic approach is based on pharmacological treatment and environmental management. Moreover, the efficacy of the administration of antioxidant molecules has been reported. The aim of the present study was to evaluate the effect of the administration of a commercial nutraceutical supplement, composed of several herbal extracts, on lower airway inflammation in racehorses. Twelve Thoroughbreds affected by MEA were selected. All horses underwent a clinical examination with assignment of a clinical score, airway endoscopy and cytological examination of bronchoalveolar lavage fluid. In seven horses, the supplement was administered for 21 days in association with environmental changes, while in five horses only environmental changes were performed. All procedures were repeated at the end of the study. Data concerning the clinical score, the endoscopic scores and the cytology at the beginning and at the end of the study were statistically compared. Data showed a significant reduction (p < 0.0156) of the clinical score and a significant reduction (p < 0.0156) of the tracheal mucus score. The results showed the beneficial effect of the supplement on mild–moderate lower airway inflammation, probably due to its antioxidant activity.

Racehorses are often supplemented extra iron with the expectation that the iron will improve overall performance and health. A survey of 120 U.S. Thoroughbred trainers, representing 1978 Thoroughbreds from various regions of the U.S., was conducted to determine the average amount of dietary iron fed to Thoroughbred racehorses per day. Survey results indicated racehorses were fed an average of 3900 mg of iron per day from hay and grain alone. This exceeds the 0.8 mg/kg BW or 400 mg for a 500 kg working horse that the NRC 2007 recommends per day. Supplements increased the daily average intake of iron by an additional 500 mg Fe. Some equine nutritionists propose that excess dietary iron may be a causative factor in insulin resistance (IR). However, the occurrence of IR in Thoroughbred racehorses is very rare. This study did not find one confirmed veterinary diagnosis of IR in any of the surveyed trainers’ Thoroughbred horses, whether racing, on a layoff, or retired. Given the iron content in these diets easily exceeds the NRC minimum daily requirements, it seems unlikely that dietary iron is an independent causative factor in IR.

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]

Abstract Background High prevalence of musculoskeletal disorders in racehorses and its impact on horse welfare and racing economics call for improved measures of injury diagnosis and prevention. Serum biomarkers of bone and cartilage metabolism have previously shown promise in prediction of musculoskeletal injuries in horses. This study aimed to re-evaluate usability of the predictive serum biomarkers identified in North American Thoroughbred racehorses in a geographically distinct group of Polish Thoroughbreds. Results Serum concentrations of bone and cartilage biomarkers: osteocalcin, c-terminal telopeptide of type I collagen, total glycosaminoglycans (GAG), chondroitin sulfate epitope and c-propeptide of type II procollagen (CPII) were evaluated in the beginning and the next 3 months of one racing season in a cohort of twenty-six 2-year-old Polish racehorses. Exit criteria were diagnosis of musculoskeletal injury, leading to > 5 days off training (n = 8), or completion of 3 study months with no training interruptions (n = 18). Normalized results and matching archival data from 35 2-year-old North American racehorses was used for logistic regression analysis to identify universal predictors of injury. Mean GAG and CPII levels were lower in injured group comparing to control, which is consistent with previous findings in racehorses. These biomarkers were also identified as predictors of injury in the mixed population model. Population origin had no significant effect on predictive value of evaluated biomarkers (Wald test p = 0.137). Decreased osteocalcin and increased c-terminal telopeptide of type I collagen levels in injured horses comparing to controls were specific for Polish population and signalized disruption in bone turnover homeostasis. Conclusions Changes in serum GAG and CPII in racehorses at risk of injury appear to be similar across distinct populations while dynamics of serum bone marker is more population-specific.