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Parkin, T. D. H., Clegg, P. D., French, N. P., Proudman, C. J., Riggs, C. M., Singer, E. R., et al. (2004). Horse-level risk factors for fatal distal limb fracture in racing Thoroughbreds in the UK. Equine Vet J, 36(6), 513–519.
Abstract: REASONS FOR PERFORMING STUDY: Fractures below the level of the radius or tibia (distal limb fractures) are the most common cause of equine fatality on UK racecourses; however, little is known about their epidemiology or aetiology. Identification of risk factors could enable intervention strategies to be designed to reduce the number of fatalities. OBJECTIVES: To identify horse-level risk factors for fatal distal limb fracture in Thoroughbreds on UK racecourses. METHODS: A case-control study design was used. Fractures in case horses were confirmed by post mortem examination and 3 matched uninjured controls were selected from the race in which the case horse was running. One hundred and nine cases were included and information was collected about previous racing history, horse characteristics and training schedules. Conditional logistic regression was used to identify the relationship between a number of independent variables and the likelihood of fracture. RESULTS: Horses doing no gallop work during training and those in their first year of racing were at significantly increased risk of fracture on the racecourse. Case horses were also more likely to have trained on a sand gallop, i.e. a gallop described by trainers as being primarily composed of sand. CONCLUSIONS: Modifications to training schedules, specifically within the first year of racing, may have a large impact on the risk of fatal distal limb fracture on the racecourse. Horses should do some gallop work in training and our results suggest that the minimum distance galloped should be between 805-2012 m (4-10 furlongs)/week. POTENTIAL RELEVANCE: The information from this study can be used to alter training schedules in an attempt to reduce the incidence of fatal distal limb fracture in Thoroughbred racehorses. Training should include some gallop work, and further studies, recording the exact level of work, will help to identify an optimum range of training speeds and distances which will reduce the liklihood of catastrophic fracture on the racecourse.
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Johnston, C., Holm, K. R., Erichsen, C., Eksell, P., & Drevemo, S. (2004). Kinematic evaluation of the back in fully functioning riding horses. Equine Vet J, 36(6), 495–498.
Abstract: REASONS FOR PERFORMING STUDY: Clinical history and examination are important features in diagnosis of equine back dysfunction. However, interpretation is subjective and therefore may vary substantially. OBJECTIVES: To establish a clinical tool to objectively evaluate the function of the equine back, in the form of a database on the kinematics of the back at the walk and trot in fully functioning riding horses. METHODS: Thirty-three fully functioning riding horses walked and trotted on a treadmill. Morphometrics and kinematics were tested for correlations to age, height, weight and stride length, and differences between gender (geldings and mares) and use (dressage and showjumping). RESULTS: A database for range of movement and symmetry of movement for extension and flexion, lateral bending, lateral excursion and axial rotation was presented. Symmetry values were very high for all variables. Significant differences were observed in use and gender. Age was negatively correlated to extension and flexion of the thoracolumbar junction. CONCLUSIONS: Interrelationships between use, gender and age to conformation and movement were established. POTENTIAL RELEVANCE: The database provides a basis for objective reference for diagnosis, therapy and rehabilitation of clinical cases of back dysfunction.
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Gerber, V., Robinson, N. E., Luethi, S., Marti, E., Wampfler, B., & Straub, R. (2003). Airway inflammation and mucus in two age groups of asymptomatic well-performing sport horses. Equine Vet J, 35(5), 491–495.
Abstract: REASONS FOR PERFORMING STUDY: Horses housed in conventional stable environments are exposed to high dust loads. Long-term exposure to inhaled dust may lead to subclinical airway disease. HYPOTHESES: Airway inflammation and mucus accumulation are 1) common in asymptomatic well-performing sport horses, 2) increased in older compared to younger individuals and 3) correlated. METHODS: Mucus quantity and quality (endoscopic scoring) and BALF differential cytology were assessed in 13 younger horses (mean age 5 years) and 13 older horses (mean age 15 years), which had no historical or clinical evidence of lower airway disease, were performing well and were housed permanently in a conventional stable environment. RESULTS: 1) Airway inflammation and/or mucus accumulation were very common. All sport horses showed evidence of subclinical inflammatory airway disease (IAD). 2) Older horses, having been exposed for 10 more years to a conventional stable environment, did not show increased subclinical airway inflammation or mucus accumulation. The only differences between the age groups were increased BALF total and lymphocyte cell counts in the younger horses. 3) Mucus quantity and quality scores were not significantly correlated with each other or with BALF neutrophil percentages and absolute numbers. CONCLUSIONS: Although clinically healthy and performing well, all of the examined horses housed in a conventional stable environment showed evidence of IAD. The degree of IAD was not increased in older horses that had not developed clinical signs. POTENTIAL RELEVANCE: The effect of subclinical degrees of IAD on performance in dressage and show jumping should be investigated further to better understand the clinical significance of IAD in sport horses.
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Peeters, M., Sulon, J., Beckers, J. - F., Ledoux, D., & Vandenheede, M. (2011). Comparison between blood serum and salivary cortisol concentrations in horses using an adrenocorticotropic hormone challenge. Equine Veterinary Journal, 43(4), 487–493.
Abstract: Reasons for performing study: In horses, serum cortisol concentration is considered to provide an indirect measurement of stress. However, it includes both free and bound fractions. The sampling method is also invasive and often stressful. This is not the case for salivary cortisol, which is collected using a more welfare-friendly method and represents a part of the free cortisol fraction, which is the biologically active form. Objectives: To compare salivary and serum cortisol assays in horses, in a wide range of concentrations, using an adrenocorticotropic hormone (ACTH) stimulation test, in order to validate salivary cortisol for stress assessment in horse. Methods: In 5 horses, blood samples were drawn using an i.v. catheter. Saliva samples were taken using swabs. Cortisol was assayed by radioimmunoassay. All data were treated with a regression method, which pools and analyses data from multiple subjects for linear analysis. Results: Mean ± s.d. cortisol concentrations measured at rest were 188.81 ± 51.46 nmol/l in serum and 1.19 ± 0.54 nmol/l in saliva. They started increasing immediately after ACTH injection and peaks were reached after 96 ± 16.7 min in serum (356.98 ± 55.29 nmol/l) and after 124 ± 8.9 min in saliva (21.79 ± 7.74 nmol/l, P<0.05). Discharge percentages were also different (225% in serum and 2150% in saliva, P<0.05). Correlation between serum and salivary cortisol concentrations showed an adjusted r2= 0.80 (P<0.001). The strong link between serum and salivary cortisol concentrations was also estimated by a regression analysis. Conclusions: The reliability of both RIAs and regression found between serum and salivary cortisol concentrations permits the validation of saliva-sampling as a noninvasive technique for cortisol level assessment in horses.
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Senior, J. M., Pinchbeck, G. L., Allister, R., Dugdale, A. H. A., Clark, L., Clutton, R. E., et al. (2006). Post anaesthetic colic in horses: a preventable complication? Equine Vet J, 38(5), 479–484.
Abstract: REASONS FOR PERFORMING STUDY: There is little information on the prevalence of, and risk factors associated with, post anaesthetic colic (PAC) in horses undergoing nonabdominal operations. OBJECTIVES: To undertake the first prospective study of prevalence of PAC and identify risk factors in its development in nonabdominal procedures. METHODS: A multicentre prospective case-control study was conducted, on every horse undergoing anaesthesia for a nonabdominal procedure between April 2004 and June 2005. Colic cases were defined as any horse with recognised signs of abdominal pain within 72 h of general anaesthesia that could not be attributed to any concurrent disease. Five control horses per case were selected randomly from the study population at all hospitals. Multivariable logistic regression analysis was used to examine the relationship between predictor variables and the risk of developing PAC. RESULTS: The estimated mean prevalence of PAC in the study population was 5.2% (95% CI, 2.8, 8.0). However, the prevalence of colic varied between each centre. The most commonly diagnosed cause of colic was impaction. Multivariable analyses showed that the centre involved and the type of surgery performed were associated with an increased risk of PAC. Preoperative food deprivation and the use of opioid drugs were confounding factors. CONCLUSIONS: Prevalence of PAC varied significantly between the 4 hospitals studied; there may be hospital-related covariates that account for this. The type of surgery performed influenced the risk of PAC. POTENTIAL RELEVANCE: Identifying the risk factors for PAC is a prerequisite for its prevention. This study indicates horses at increased risk of PAC that might benefit from a more critical evaluation of post anaesthetic gastrointestinal function and/or the provision of preventative measures. Further investigation is required to explain the variation in prevalence of PAC between centres.
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Robert, C., Valette, J. P., & Denoix, J. M. (2006). Correlation between routine radiographic findings and early racing career in French trotters. Equine Vet J Suppl, (36), 473–478.
Abstract: REASONS FOR PERFORMING STUDY: The relationship between the presence of radiological abnormalities and subsequent racing performance is controversial. However, as training is expensive and time consuming, it would save time and money to identify subjects with osteo-articular lesions not compatible with a normal racing career on the basis of routine radiographic screenings at yearling age. OBJECTIVES: To evaluate the impact of osteo-articular lesions on racing ability in French Trotters and identify radiographic changes associated with failure in 'qualification', in order to provide objective criteria for selection of horses based on their osteo-articular status. HYPOTHESIS: The influence of radiographic findings (RF) on racing ability depends on their nature, location, clinical relevance and number. METHODS: The limbs of 202 French Trotters were radiographed just before they started training. All the RF were graded according to a standardised protocol depending on their severity. The success in 'qualification' (first race in career of French Trotters) was the criteria used to assess racing ability. Breeders and trainers were questioned about the causes for horses not racing. RESULTS: Overall 113 (55.9%) horses qualified. Osteoarticular lesions were directly responsible for nonqualification in 31% of the horses. Subjects with more than one abnormal RF, with abnormal RF on the fore-, hind-fetlock or proximal tarsus were less likely to qualify. Dorsal modelling in the front fetlock and osteochondrosis of the lateral trochlear ridge of the femur also significantly reduced the qualification rate. CONCLUSIONS: Most RF are compatible with beginning a racing career, but severe RF or multiple abnormal RF significantly compromise future racing career. POTENTIAL RELEVANCE: This study supports the use of routine radiographic programmes for detection of osteoarticular lesions in yearlings. A synthetic radiographic score, based on both the severity and the number of lesions, could be useful for breeders and trainers as complementary information to select their horses.
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Robert, C., Valette, J. P., & Denoix, J. M. (2001). The effects of treadmill inclination and speed on the activity of three trunk muscles in the trotting horse. Equine Vet J, 33(5), 466–472.
Abstract: The purpose of this study was to evaluate the effects of speed and slope on the activity of trunk muscles. The electromyographic (EMG) activity of the splenius (Sp), longissimus dorsi (LD) and rectus abdominis (RA) muscles was recorded with surface electrodes during treadmill locomotion at trot for different combinations of speed (3.5 to 6 m/s) and slope (0 to 6%). Raw EMG signals were processed to determine activity duration, onset and end and integrated EMG (IEMG). For the 3 muscles investigated, onset and end of activity were obtained earlier in the stride cycle when speed increased. A longer duration of activity for the LD, a shorter duration for the RA and an unchanged duration for the Sp were also observed. The IEMG of the latter was poorly affected by speed, whereas it increased linearly with speed for the 2 other muscles. When treadmill inclination changed from 0 to 6%, EMG activity of the LD and RA began and ended later; a longer activity duration was noted. Temporal parameters for Sp did not change with slope. A significant and progressive increase in the IEMG of the 3 muscles was observed with increasing slope. This evaluation of the activity of trunk muscles provides objective data for the use of speed or slope in training programmes.
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Albright, J. D., Mohammed, H. O., Heleski, C. R., Wickens, C. L., & Houpt, K. A. (2009). Crib-biting in US horses: Breed predispositions and owner perceptions of aetiology. Equine Veterinary Journal, 41(5), 455–458.
Abstract: Reasons for performing study: Crib-biting is an equine stereotypy that may result in diseases such as colic. Certain breeds and management factors have been associated.
Objectives: To determine: breed prevalence of crib-biting in US horses; the likelihood that one horse learns to crib-bite from another; and owner perceptions of causal factors.
Methods: An initial postal survey queried the number and breed of crib-biting horses and if a horse began after being exposed to a horse with this habit. In a follow-up survey, a volunteer subset of owners was asked the number of affected and nonaffected horses of each breed and the extent of conspecific contact. The likelihood of crib-biting given breed and extent of contact was quantified using odds ratio (OR) and significance of the association was assessed using the Chi-squared test.
Results: Overall prevalence was 4.4%. Thoroughbreds were the breed most affected (13.3%). Approximately half of owners believed environmental factors predominantly cause the condition (54.4%) and crib-biting is learned by observation (48.8%). However, only 1.0% of horses became affected after being exposed to a crib-biter. The majority (86%) of horses was turned out in the same pasture with other horses and extent of contact with conspecifics was not statistically related to risk.
Conclusion: This is the first study to report breed prevalence for crib-biting in US horses. Thoroughbreds were the breed more likely to be affected. More owners believed either environmental conditions were a predominant cause or a combination of genetic and environmental factors contributes to the behaviour. Only a small number of horses reportedly began to crib-bite after being exposed to an affected individual, but approximately half of owners considered it to be a learned behaviour; most owners did not isolate affected horses.
Potential relevance: Genetic predisposition, not just intensive management conditions and surroundings, may be a factor in the high crib-biting prevalence in some breeds, and warrants further investigation. Little evidence exists to suggest horses learn the behaviour from other horses, and isolation may cause unnecessary stress.
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Bystrom, A., Roepstorff, L., & Johnston, C. (2006). Effects of draw reins on limb kinematics. Equine Vet J Suppl, (36), 452–456.
Abstract: REASONS FOR PERFORMING STUDY: No data exist on the GRF-kinematics relation due to changes caused by equestrian interventions. HYPOTHESIS: Through the judicious use of draw reins the rider can influence the kinematics of the horse to meet stated goals of dressage training. Relating the results to previously published kinetic data of the same experiment implies a possible relationship between kinetics and kinematics. METHODS: The kinematics of 8 sound Swedish Warmblood horses were measured whilst the horses were being ridden with and without draw reins. Three conditions were evaluated: 1) draw reins only (DR), 2) combination of draw reins and normal reins (NR+DR) and 3) normal reins only (NR). RESULTS: Head and neck angles were significantly decreased by the draw rein but 4-5 times more so for DR when with NR+DR. The forelimb position at hoof lift-off was significantly more caudal with DR. In the hind limb the hip joint extended more quickly and the hock joint flexed more with NR+DR than with NR. Compared to DR the hip joint angular pattern was not significantly different, but the pelvis was more horizontal. CONCLUSION: Riding with a draw rein can have significant influence on the kinematics of the horse. Some of the observed changes can be coupled to changes in kinetics. The hock joint angle seems to be a fairly reliable indicator of load on the hind limb and the angle of femur appears important for hind limb propulsion, when considered in conjunction with the orientation of the pelvis. POTENTIAL RELEVANCE: These findings are important for riders and trainers, as kinematic changes are what trainers observe. It is thereby important to ascertain which kinematic changes are consistently coupled to changes in kinetics in order for trainers to be able to judge correctly the success of intended goals. Further studies are warranted to validate and confirm suggested relationships between kinetics and kinematics.
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Gomez Alvarez, C. B., Rhodin, M., Bobber, M. F., Meyer, H., Weishaupt, M. A., Johnston, C., et al. (2006). The effect of head and neck position on the thoracolumbar kinematics in the unridden horse. Equine Vet J Suppl, (36), 445–451.
Abstract: REASONS FOR PERFORMING STUDY: In many equestrian activities a specific position of head and/or neck is required that is dissimilar to the natural position. There is controversy about the effects of these positions on locomotion pattern, but few quantitative data are available. OBJECTIVES: To quantify the effects of 5 different head and neck positions on thoracolumbar kinematics of the horse. METHODS: Kinematics of 7 high level dressage horses were measured walking and trotting on an instrumented treadmill with the head and neck in the following positions: HNP2 = neck raised, bridge of the nose in front of the vertical; HNP3 = as HNP2 with bridge of the nose behind the vertical; HNP4 = head and neck lowered, nose behind the vertical; HNP5 = head and neck in extreme high position; HNP6 = head and neck forward and downward. HNP1 was a speed-matched control (head and neck unrestrained). RESULTS: The head and neck positions affected only the flexion-extension motion. The positions in which the neck was extended (HNP2, 3, 5) increased extension in the anterior thoracic region, but increased flexion in the posterior thoracic and lumbar region. For HNP4 the pattern was the opposite. Positions 2, 3 and 5 reduced the flexion-extension range of motion (ROM) while HNP4 increased it. HNP5 was the only position that negatively affected intravertebral pattern symmetry and reduced hindlimb protraction. The stride length was significantly reduced at walk in positions 2, 3, 4 and 5. CONCLUSIONS: There is a significant influence of head/neck position on back kinematics. Elevated head and neck induce extension in the thoracic region and flexion in the lumbar region; besides reducing the sagittal range of motion. Lowered head and neck produces the opposite. A very high position of the head and neck seems to disturb normal kinematics. POTENTIAL RELEVANCE: This study provides quantitative data on the effect of head/neck positions on thoracolumbar motion and may help in discussions on the ethical acceptability of some training methods.
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