National Hunt Research Articles

Subclinical ultrasonographic abnormalities of the suspensory ligament branches in National Hunt racehorses.

Suspensory ligament branch (SLB) desmopathy is a common cause of lameness and an important cause of lost training in the Thoroughbred racing industry. Studies have assessed the impact of insertional injuries of the SLB on the careers of flat racehorses and established the prevalence of subclinical ultrasonographic SLB abnormalities in this population, but little work has investigated SLB injury in National Hunt (NH) racehorses. To investigate the prevalence of subclinical ultrasonographic SLB abnormalities in NH racehorses with no clinical signs or history of SLB injury and to establish the cross-sectional area (CSA) of SLBs in this population. Cross-sectional study using data collected from horses on an NH yard. Ultrasonographic examination of forelimb SLBs in 62 horses on a single NH yard was performed. Images were graded according to a previously reported system. CSA measurements were obtained from transverse images. Nineteen of 62 horses had at least one SLB with grade 2 ultrasonographic abnormalities. Grade 2 ultrasonographic abnormalities occurred more frequently in the medial than the lateral SLB (P = 0.05). The medial SLB insertional CSA was significantly larger (P<0.001) than that of the lateral SLB. Length of time on the yard (and therefore available veterinary history) is variable in this population. One in three NH racehorses without history or clinical signs of SLB injury had at least one SLB with a grade 2 ultrasonographic abnormality. The medial branch was over-represented. The medial SLB insertional CSA is larger than the lateral and thus comparison with the corresponding branch in the contralateral limb is recommended to avoid misdiagnosis of medial SLB enlargement.

Subclinical Ultrasonographic Abnormalities of the Suspensory Ligament Branches in National Hunt Racehorses

Subclinical Ultrasonographic Abnormalities of the Suspensory Ligament Branches in National Hunt Racehorses

Comparison of treatment outcomes for superficial digital flexor tendonitis in National Hunt racehorses

Superficial digital flexor (SDF) tendonitis is a common injury in Thoroughbred racehorses. Injuries require prolonged rehabilitation, with unpredictable outcomes and a high incidence of re-injury. This observational case–control study aimed to compare race outcomes after commonly advocated treatments for tendon healing. Clinical and racing records were evaluated for 127 National Hunt racehorses treated between 2007 and 2011 for an SDF tendon injury. Two age- and sex-matched control horses were selected for each case horse to analyse the effect on post-injury racing outcomes of pre-injury data, lesion severity and treatment group [controlled exercise alone, bar firing, intralesional platelet-rich plasma (PRP), tendon splitting, tendon splitting combined with bar firing]. Control horses raced more often than case horses, with higher maximum racing post rating (RPRmax) and longer racing distances. Pre-injury racing performance was not associated with treatment group. Rate of return to racing was not associated with lesion severity or treatment group. Number of races, total distance raced post-injury and RPRmax were not associated with lesion severity or treatment group. Controlled exercise alone offered similar post-injury racing outcomes in National Hunt racehorses with SDF tendonitis to the other treatment options examined. Bar firing, either alone or in conjunction with tendon splitting, provided no additional benefit in rate of return to racing and race performance.

Winning margins in British Thoroughbred racehorses

In human sporting events the difference between finishing first and second is often less than 1%. For each sporting discipline it is important to know how large an enhancement of performance needs to be before it makes a difference to the medal winning prospects of that athlete. In contrast to the known winning margins in many human sporting disciplines, the winning margins in horse racing are unknown. The winning margins for group 1, 2 and 3 flat and national hunt races over a 5 year period were calculated. For flat races 3 categories were included: (1) flat races of 6 furlongs; (2) 1 mile; or (3) 1 mile 4 furlongs1. For national hunt 2 categories were included: (1) hurdle races over 2 miles; or (2) chase races over 3 miles. Race times from a total of 416 races were included (275 flat races and 141 national hunt races). Overall the percentage difference between first place and second place was only 0.32%, the difference between coming first and third was 0.75% and between first and fourth was 1.15%. Overall, the winning margins between first place and second place were closer for flat races than for national hunt races. When a 1% improvement was applied to the fourth placed horse this would result in the winning time in 76% of flat races and 50% of national hunt races. This study shows the very small margins between winning and placing in horseracing. These results are similar to those of elite human sporting disciplines. This suggests that training strategies and veterinary interventions that result in a small percentage improvement in performance may translate to a meaningful difference in terms of winning/placing.

Musculoskeletal Health, Kidney and Liver Function in Retired Jockeys.

The long-term implications of making-weight daily on musculoskeletal health and functioning of the kidney and liver remain unknown. This study aimed to investigate musculoskeletal health and kidney and liver function in a group of retired jockeys. 28 retired male jockeys (age 50-70 years) provided fasting blood samples for markers of bone metabolism and kidney and liver function. A dual-energy x-ray absorptiometry (DXA) scan was performed for the assessment of bone mineral density (BMD). Established reference ranges were used for interpretation of results. Comparisons were made between retired jockeys based on the professional racing licence held: Flat, National Hunt or Dual. Mean whole-body osteopenia was reported, with no differences between groups. Bone markers, micronutrients, electrolytes and associated hormones, and markers for kidney and liver function were within clinical normative ranges. No differences existed between groups. Results indicate the retired jockeys in this study do not demonstrate compromised bone health or kidney and liver function. However, the retired jockeys may not have undergone chronic weight cycling in the extreme manner evident in present-day jockeys, indicating the next generation of jockeys may face more of a problem. Jockeys should be tracked longitudinally throughout their racing career and beyond.

Falls in Swedish hurdle and steeplechase racing and the condition of the track surface

Falls in National Hunt races is a tragic part of the sport. The present study focuses on the relation between racing track conditions and the number of falls in Swedish jump racing. The assumption was that more horses fell on heavy or soft going than on good or firm going. Results from all jump races at Täby Racecourse (1992-2001) were recorded. Parameters registered were: type and number of races, racing surface and condition, total time to finish the race, number of starting horses and number of falls. In this period 212 races, corresponding to 1,556 horse starts, were registered. Falls were registered in 42 races and in total 61 horses fell. The fall frequency on horse level was significantly higher in steeplechases than in hurdle races (odds ratio =3.69; 95% confidence interval (CI) = 1.99-6.85). For the steeplechases recorded in this study, significantly more falls were seen in long distance races (&gt;4,000 m) on soft to heavy going (odds ratio = 5.20; 95% CI = 1.48-18.26), whereas no significant trends were observed due to total time to finish the race, number of starting horses, temperature, and calendar year. For the hurdle chases recorded, no significant associations between fall-frequency and the recorded explanatory variables were found. The fact that significantly more horses fell in long-distance steeplechases on soft to heavy going, makes surface condition important to consider in order to improve race safety. Among the 195 horse starts in long-distance steeplechases in this study 7 (2-11) falls could have been prevented by cancelling races on soft to heavy surfaces.

Erratum: Williams et al (2013) A preliminary evaluation of surface electromyography as a tool to measure muscle fatigue in the National Hunt racehorse

Erratum: Williams et al (2013) A preliminary evaluation of surface electromyography as a tool to measure muscle fatigue in the National Hunt racehorse

Comments on the dilemma in the March issue:‘Looking a store horse in the mouth’

The dilemma in the March issue concerned a well-bred, four-year-old, National Hunt filly, to be vetted before the premier sales (In Practice, March 2014, volume 36, pages 158-156). The horse...

Accuracy of distal limb fracture diagnosis at British racecourses 1999–2005

Accurate diagnosis of racing injuries can be difficult. The objectives of this study were to describe the postmortem (PM) defined distribution of fatal distal limb fractures (DLF) affecting Thoroughbreds racing...

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

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

A preliminary evaluation of surface electromyography as a tool to measure muscle fatigue in the National Hunt racehorse

Background: Within equestrian sports, training is commonly based on historic and anecdotal good practice. Telemetric surface electromyography (sEMG) systems facilitate assessment of muscle recruitment including mean motor unit action potential (mM-UAP). Mean EMG frequency (mEMGF) provides an objective measure of fitness levels while a shift in the median EMG frequency (MeEMGF) over time can illustrate fatigue. Aim: This study aimed to investigate if sEMG could be used in the field to evaluate muscle activity of the Gluteus superficialis in a cohort of National Hunt racehorses during one canter interval training session. Method: Sensors were secured bilaterally to horses' Gluteal superficialis prior to exercise and data were collected over a standardised 10 metre interval. A repeated measure ANOVA assessed differences in mEMGF between runs across the cohort and between runs for individual horses. A Pearson's correlation identified if mEMGF was related to perceived fitness level as assessed by the trainer. mEMGF and MeEMGF for individual horses were plotted over time (0.25 second intervals) to assess fitness and fatigue. Results: Individual horses exhibited a wide variety of mMUAP values. No differences were found between runs for the overall cohort (p&gt;0.05) however significant differences were found between runs within some individual horses (p&lt;0.01). No relationship between fitness level and mEMGF was found (p&gt;0.05), mEMGF varied throughout runs and MeEMGF for most horses remained consistent indicative of a lack of fatigue. Conclusion: The results suggest that this technology exhibits potential to be used to aid analysis of efficacy of training programmes for individual horses.

Polymorphisms in TNC and COL5A1 genes are associated with risk of superficial digital flexor tendinopathy in National Hunt Thoroughbred racehorses

To explore whether genetic susceptibility is a potential risk factor for superficial digital flexor (SDF) tendinopathy in Thoroughbred (TB) racehorses. To identify informative single nucleotide polymorphisms (SNPs) that capture genetic diversity across a range of candidate genes and to investigate, in a case-control study, their association with SDF tendinopathy in UK National Hunt TB racehorses in training. Case-control candidate gene association study. This study used in silico gene assembly and DNA sequencing to screen candidate genes for SNPs. Seven candidate genes were selected using a hypothesis-driven approach: tenascin-C (TNC), collagen, type 1, α 1 (COL1A1), collagen, type 5, α 1 (COL5A1), matrix metalloproteinase type 3 (MMP3), matrix metalloproteinase type 13 (MMP13), fibromodulin (FMOD) and cartilage oligomeric matrix protein (COMP). The SNPs were validated in DNA isolated from 48 TB racehorses and used to genotype 270 racehorses with SDF tendinopathy and 270 yard-matched controls. Genotyping of cases and controls was performed using SNaPshot™. Racehorses heterozygous for the TNC BIEC2-696469 polymorphism were less likely to have SDF tendinopathy than racehorses homozygous for the wild-type allele (odds ratio [OR] 0.56, 95% confidence interval [CI] 0.36-0.85, P = 0.01). This finding remained significant after adjustment for age and racing background (OR 0.57, 95% CI 0.36-0.92, P = 0.03). Racehorses homozygous for the novel COL5A1 COL5A1_01 variant allele were nearly 3 times more likely to have SDF tendinopathy than those homozygous for the wild-type allele (OR 2.82, 95% CI 1.25-6.35, P = 0.01); this association remained significant after adjustment for age and racing background (OR 2.77, 95% CI 1.18-6.53, P = 0.03). Results suggest that sequence variants in TNC and COL5A1 genes are associated with SDF tendinopathy in TB racehorses. In future genetic markers may be used to identify horses at risk of SDF tendinopathy.

The Effect of Injection Needle Gauge Size on the Viability of Equine Mesenchymal Stem Cells

AimsPerformance horses are at high risk of injury to the superficial digital flexor tendon (SDFT). Studies have shown that autologous mesenchymal stem cells (MSCs) injected into SDFT lesions subsequently result in a significant reduction of re‐injury in National Hunt racehorses; however, recent studies show that only 25% of implanted MSCs survive 24 h post injection. The reason for this loss is unclear but may relate to cell quiescence or injection‐related mortality. We hypothesised that cell viability and mortality is increased with needle gauge.MethodsEquine MSCs cultured in vitro were resuspended to a final suspension density of 5 x 105 cells/ml to mimic that used for implantation in clinic. The cell suspension was injected through a 19 gauge, 21 gauge (current practice in clinic) or 23 gauge needle. Mesenchymal stem cells viability and mortality was analysed over a 24 h period post injection using alamarBlue® and Annexin V (apoptosis) assays, respectively.ResultsThere was a 25% reduction in viability (P&lt;0.01) and mortality (P&lt;0.01) compared with noninjected MSCs over the 24 h period post injection. All needle gauges also induced a decrease in cell metabolic activity immediately post injection but with recovery by 2 h post injection. Furthermore, 21 gauge and 23 gauge needles increased early apoptotic cells immediately post injection, whereas the 19 gauge needle showed a delayed increase in apoptosis until 2 h post injection.ConclusionsThe delayed apoptosis may correlate with a subpopulation of quiescent cells subsequently becoming apoptotic. The proportion of early and late apoptotic MSCs, while significant, does not account for the total cell loss reported after intra‐lesional injection.Practical significanceNeedle gauge selection has significant implications for the survival of MSC intra‐lesional injections but it may not be the sole factor implicated in post injection cell mortality. We therefore recommend a minimum diameter of 19 gauge should be used for implantation.Ethical animal researchStem cell lines were obtained from bone marrow with approval of the Institutional Ethical Committee and under UK Home Office licence. Sources of funding: Funded by the Medical Research Council and The Royal Veterinary College. Competing interests: None.

Infectious risk factors and clinical indicators for tracheal mucus inBritishNationalHunt racehorses

Many studies of respiratory disease in racehorses have focused on a combination of increased tracheal mucus and airway neutrophilia. Examination of each component separately should provide further insight into this condition. To identify infectious risk factors for endoscopically visible tracheal mucus in National Hunt racehorses. A 2 year prospective longitudinal study. Monthly quantitative bacteriological examinations of tracheal wash samples and viral serological examinations were conducted. Risk factors for 'small amounts of mucus' (mucus score = 1/3) and 'increased mucus' (score ≥2/3) were identified. There were increased odds of small amounts of mucus when both Streptococcus zooepidemicus and nonhaemolytic streptococci (NHS) were isolated (odds ratio [OR] 2.6; 95% confidence interval [CI] 1.5-4.6; P<0.001) but not when either species was isolated in the absence of the other. Increased odds of increased mucus were associated with the isolation of either S. zooepidemicus (OR 5.6; 95% CI 1.2-25.9; P = 0.03) or NHS (OR 3.7; 95% CI 1.2-11.6; P = 0.02), with an increased effect when both were isolated together (OR 12.5; 95% CI 3.7-41.6; P<0.001). Approximately 6-fold increased odds of small amounts of mucus were associated with the first 3 months in training (OR 6.3; 95% CI 2.0-19.4; P<0.001) and 3-fold increased odds of increased mucus associated with the first 6 months in training (OR 2.9; 95% CI 1.3-6.4; P = 0.01). Coughing at exercise and increased serous nasal discharge were specific but insensitive indicators of increased mucus. Associations with S. zooepidemicus corroborate previous research, but an independent effect of NHS has not previously been reported. The possibility that there are individual pathogenic species within this group should be considered. Further work is required to identify S. zooepidemicus subtypes and NHS species associated with disease. Closer monitoring of the respiratory health of horses entering training for the first time is likely to be valuable.

A longitudinal study of respiratory infections in British National Hunt racehorses

Lower airway inflammation is a much investigated multifactorial problem in racehorses in training (Burrell 1985, Wood and others 1993, Burrell and others 1994, Burrell and others 1996, Chapman and others...

Beating the odds: using epidemiology to pick the Cheltenham Gold Cup winner

Aim: To date epidemiology has been widely utilised to analyse disease and identify risk factors associated with injury. This study aimed to establish if epidemiology has the potential to be employed as a predictive model of National Hunt racing performance. Objectives: The purpose of the present study was to apply the principles of epidemiology to predict factors that impact on individual performance in the Cheltenham Gold Cup and to strengthen the potential of epidemiology as a valid methodology for predicting racehorse performance. Methods Relevant factors related to racehorse performance were identified and collated via the Racingpost website for horses that had run in the Cheltenham Gold Cup from 1995 to 2010. Subsequent univariate and multivariable single-level and mixed effects logistic regression models were developed using winning the Cheltenham Gold Cup as the dependent variable. Results The chance of a horse winning the Cheltenham Gold Cup is increased by 1.09 times for each extra 10 percentage point increase in the percentage of starts at Cheltenham that resulted in a win. Horses that had been ridden by only one or two jockeys throughout their career were 40 times more likely to win than horses that had been ridden by three or more jockeys. Conclusions National Hunt racehorses that have one or two consistent jockeys throughout their racing career and have a higher course runs to win ratio at Cheltenham are predicted to perform superiorly to their peers who do not. Potential relevance: Epidemiology appears to be a valid tool for predicting variables that can increase the probability of superior performance for specific events and has potential to be utilised in other equine sporting fields.

Markers of Bone Health, Renal Function, Liver Function, Anthropometry and Perception of Mood: A Comparison between Flat and National Hunt Jockeys

Given the requirement of professional jockeys to make-weight daily, we tested the hypothesis that Flat and National Hunt (Jump) jockeys would display compromised health markers (bone health, vitamin D, liver and kidney function and mood) compared with established clinical norms, with Flat jockeys affected the greater. Daily energy intake was lower in Flat compared with Jump jockeys (6.11±1.25 vs. 7.47±0.83 MJ.day - 1, P=0.01) whereas there was no difference in urine osmolality (811±198 vs. 678±317 mOsmol x kg(-1) respectively, P=0.13). Serum total 25(OH)D was insufficient in Flat and Jump jockeys (37.6±28 vs. 35.1±14 nmol x L(-1) respectively although there was no difference between groups (P=0.79). Markers of bone metabolism (Plasma β-carboxy-terminal cross-linked teleopeptide (CTX) and Intact Parathyroid Hormone (PTH) and liver and kidney function were within clinical normative ranges although CTX and PTH were higher than average. Abnormal mood profiles were observed in both groups although significantly poorer in the Flat jockeys (P=0.01). We conclude that the current practices of jockeys to make-weight may have detrimental effects upon their health with Flat jockeys affected more so than Jump jockeys. Future studies should investigate the effects of improved dietary practices on the mental and physical health of Flat and Jump jockeys.

Toward new understandings of human–animal relationships in sport: a study of Australian jumps racing

The importance of studying human–animal relationships and animal subjectivity is increasingly recognised by social and cultural geographers, particularly in agricultural pursuits. Little research, however, has been undertaken on animals in sport, resulting in a limited understanding of the perceptions and treatment of animals in society. To address this concern, we interrogate print media coverage of the construction and positioning of horses and humans in the controversial activity of jumps racing (National Hunt) in Australia between February 2008 and December 2009. We highlight the importance of seemingly contradictory human–animal relationships involving close frequent contact of some jumps racing advocates in contrast to the distanced, mediated relationships of jumps racing opponents. This paper highlights how the particular activity of jumps racing generates specific human–animal relationships and emphasises the need to reflect on the attitudes that shape and constrain human–animal relationships in varying contexts, including how these attitudes are mediated and the potential consequences for humans and other animals. These findings form the basis for a suggested research agenda that recognises the importance and articulation of proximity and mediation in human–animal relationships, particularly those focused on activities labelled ‘sport’.

An Alternative Dietary Strategy to Make Weight While Improving Mood, Decreasing Body Fat, and Not Dehydrating: A Case Study of a Professional Jockey

Professional jockeys are unique among weight-making athletes, as they are often required to make weight daily and, in many cases, all year-round. Common methods employed by jockeys include dehydration, severe calorie restriction, and sporadic eating, all of which have adverse health effects. In contrast, this article outlines a structured diet and exercise plan, employed by a 22-yr-old professional National Hunt jockey in an attempt to reduce weight from 70.3 to 62.6 kg, that does not rely on any of the aforementioned techniques. Before the intervention, the client's typical daily energy intake was 8.2 MJ (42% carbohydrate [CHO], 36% fat, 22% protein) consumed in 2 meals only. During the 9-wk intervention, daily energy intake was approximately equivalent to resting metabolic rate, which the athlete consumed as 6 meals per day (7.6 MJ, 46% CHO, 19% fat, 36% protein). This change in frequency and composition of energy intake combined with structured exercise resulted in a total body-mass loss of 8 kg, corresponding to reductions in body fat from 14.5% to 9%. No form of intentional dehydration occurred throughout this period, and mean urine osmolality was 285 mOsm/kg (SD 115 mOsm/kg). In addition, positive changes in mood scores (BRUMS scale) also occurred. The client was now able to ride light for the first time in his career without dehydrating, thereby challenging the cultural practices inherent in the sport.

Weight regulation and bone mass: a comparison between professional jockeys, elite amateur boxers, and age, gender and BMI matched controls

The aim of this study was to compare bone mass between two groups of jockeys (flat: n=14; national hunt: n=16); boxers (n=14) and age, gender and BMI matched controls (n=14). All subjects underwent dual energy X-ray absorptiometry (DXA) scanning for assessment of bone mass, with measurements made of the total body, vertebra L2-4 and femoral neck. Body composition and the relative contribution of fat and lean mass were extrapolated from the results. Data were analysed in accordance with differences in body composition, in particular, height, lean mass, fat mass and age. Both jockey groups were shown to display lower bone mass than either the boxers or control group at a number of sites including total body bone mineral density (BMD) (1.019±0.06 and 1.17±1.05 vs. 1.26±0.01 and 1.26±0.06gcm(-2) for flat, national hunt, boxer and control, respectively), total body bone mineral content (BMC) less head, L2-4 BMD and femoral neck BMD and BMC (p<0.05). Regression analysis revealed that lean mass and height were the primary predictors of total body BMC, although additional group-specific influences were present which reduced bone mass in the flat jockey group and enhanced it in the boxers (R (2)=0.814). Reduced bone mass in jockeys may be a consequence of reduced energy availability in response to chronic weight restriction and could have particular implications for these athletes in light of the high risk nature of the sport. In contrast, the high intensity, high impact training associated with boxing may have conveyed an osteogenic stimulus on these athletes.