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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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Hada, T., Ohmura, H., Mukai, K., Eto, D., Takahashi, T., & Hiraga, A. (2006). Utilisation of the time constant calculated from heart rate recovery after exercise for evaluation of autonomic activity in horses. Equine Vet J Suppl, (36), 141–145.
Abstract: REASONS FOR PERFORMING STUDY: Heart rate (HR) recovery immediately after exercise is controlled by autonomic functions and the time constant (T) calculated from HR recovery is thought to be an index of parasympathetic activity in man. OBJECTIVES: To investigate whether it is possible to evaluate autonomic function using the time constant in horses. METHODS: Five Thoroughbred horses were subjected to a standard exercise test. Following pre-medication with saline, atropine and/or propranolol, the horses ran for 2.5 min at a speed of 8 m/sec at a 10% incline and T was calculated from HR after the exercise. Secondly, 7 Thoroughbred horses were then trained for 11 weeks and T and maximal oxygen uptake (VO2max) measured at intervals of 1 or 2 weeks. In 6 horses, T with atropine pre-medication was also measured before and after the whole training period. Furthermore, the HR variability at rest was evaluated by power spectral analysis at intervals of 3 or 4 weeks. RESULTS: Time constant was increased by atropine and/or propranolol pre-medication, decreased with the progress of training and inversely correlated with VO2max during training (r = 0.43, P<0.005). Parasympathetic blockade significantly decreased T only after and not before, the training; however, T was lower in post training than in pretraining, irrespective of parasympathetic blockade. On the other hand, parasympathetic activity at rest was attenuated and sympathetic activity became predominant following the training. CONCLUSION: Heart rate recovery is affected by sympathetic withdrawal and parasympathetic reactivation in horses and suggests that physical training hastened HR recovery by improving the parasympathetic function after exercise with aerobic capacity. However, the effects of other factors need to be considered because the training effect appeared on T even under parasympathetic blockade. The parasympathetic activity at rest is in contrast to that after exercise, suggesting that T does not reflect parasympathetic activity at rest. POTENTIAL RELEVANCE: If demonstrated how HR recovery is controlled after exercise, its analysis will be important in the evaluation of physical fitness in horses.
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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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Groesel, M., Zsoldos, R. R., Kotschwar, A., Gfoehler, M., & Peham, C. (2010). A preliminary model study of the equine back including activity of longissimus dorsi muscle. Equine Veterinary Journal, 42, 401–406.
Abstract: Reasons for performing study: Identifying the underlying problem of equine back pain and diseases of the spine are significant problems in veterinary orthopaedics. A study to validate a preliminary biomechanical model of the equine back based on CT images including longissimus dorsi (LD) muscle is therefore important. Objectives: Validation of the back model by comparing the shortening of LD muscles in the model with integrated EMG (IEMG) at stance during induced lateral flexion of the spine. Methods:Longissimus dorsi muscle activity at stance has been used for validation. EMG electrodes were placed laterally at the level of T12, T16 and L3. Reflective markers have been attached on top of the spinous processes T5, T12, T16, L1 and the sacral bone (OS1, OS2) for motion tracking analysis. A virtual model of the equine's back (T1–S5) was built with inclusion of a simplified LD muscle by 2 separate contours left and right of the spine, starting at tuber coxae laterally and attaching to the spinous process T5 medially. Shortening of LD during induced lateral flexion caused by the kinematic data (input) was compared to the 3 EMG signals (T12, T16 and L3) on the active side via correlation. Results: Pearson correlation coefficient between IEMG and shortening length of LD in the model was (mean ± s.d.) 0.95 ± 0.07 for the left side and 0.91 ± 0.07 for the right side of LD. Conclusions: Activity of the LD muscles is mainly responsible for stabilisation of the vertebral column with isometric muscle contraction against dynamic forces in walk and trot. This validation requires muscle shortening in the back, like induced lateral flexion at stance. The length of the shortening muscle model and the IEMG show a linear relationship. These findings will help to model the LD for forward simulations, e.g. from force to motion.
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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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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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Cottin, F., Barrey, E., Lopes, P., & Billat, V. (2006). Effect of repeated exercise and recovery on heart rate variability in elite trotting horses during high intensity interval training. Equine Vet J Suppl, (36), 204–209.
Abstract: REASONS FOR PERFORMING STUDY: Interval training is a commonly used training method for trotting horses. In addition, trainers are provided with efficient and inexpensive heart rate monitor devices for the management of training. HYPOTHESIS: Since the high frequency (HF) frequency peak (fHF) of heart rate variability (HRV) corresponds to the breathing frequency in combination with stride frequency during trotting, it is hypothesised that modifications of breathing and stride frequencies induced by repeated exercise could be detected from fHF. METHODS: RR interval time series of 7 trotting horses were recorded during an interval training session. Interval training was made up of 5 successive 800 m high-velocity trotting runs (H1, H2...H5) separated by 1 min recovery bouts at low speed (R1, R2...R5). Fast Fourier transform (FFT) and Poincare plot analysis techniques were applied to RR series. RESULTS: Repeated exercise had significant effects on HRV components during interval training. Despite constant trotting velocities during high-speed and recovery, repetition induced a decrease in mean RR interval (H1: 295 +/- 19 vs. H5: 283 +/- 15 msec, P<0.05) and in the root mean square of successive differences in RR series (RMSSD; H1: 6.31 +/- 1.28 vs. H5: 5.31 +/- 1.31 msec, P<0.05). Furthermore, high-speed and recovery repetitions induced an increase in fHF (H1: 1.37 +/- 0.35 vs. H5: 1.62 +/- 0.40 Hz and R1: 0.22 +/- 0.02 vs. R4: 0.64 +/- 0.38 Hz, P<0.05). Hence, recovery induced a decrease in the s.d. of the successive RR series (SDRR; R3: 10.5 +/- 3.96 vs. R5: 6.17 +/- 2.65 msecs, P>0.05) and in the long term index of Poincare plot (SD2; R1: 43.29 +/- 28.90 vs. R5: 18.19 +/- 9.35 msecs, P<0.05). CONCLUSIONS: The observed increase in fHF during the interval training could be induced by alterations of the coupling between breathing and stride frequency linked to the emergence of fatigue. The decrease in SD2 and SDRR during successive recovery bouts could be linked with a deterioration of the recovery pattern. POTENTIAL RELEVANCE: HRV can provide breathing frequency data of Standardbreds during training without any respiratory device. Furthermore, HRV could provide useful makers of the emergence of fatigue states during training.
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Cayado, P., Munoz-Escassi, B., Dominguez, C., Manley, W., Olabarri, B., Sanchez de la Muela, M., et al. (2006). Hormone response to training and competition in athletic horses. Equine Vet J Suppl, (36), 274–278.
Abstract: REASONS FOR PERFORMING STUDY: It is recognised that the amount of psychological stress that an animal encounters determines the degree of response of the hypothalamic-pituitary-adrenal (HPA) axis. In human athletes, the added emotive stress of competition is an important element in the adrenal response. The aim of this study was to examine the effect of show-jumping as well as dressage on stress levels by comparing horses' stress response at a horse show compared to their familiar home. METHODS: Fifty-one horses involved in competition were used. EDTA blood samples were collected before exercise, upon arrived to the schooling area (control), and k over a jump or dressage course. After sampling, plasma was separated and stored at -80 degrees C until determinations of cortisol and ACTH were performed. Fourteen healthy horses not involved in competition were used as control group. RESULTS: Competition induced a significant increase in cortisol and ACTH responses in both, jumping and dressage horses and this effect was more apparent in dressage horses. When horses were most experienced, cortisol and ACTH responses were much lower. CONCLUSION: This study shows that competition elicits a classic physiological stress response in horses and that different training programmes induce different responses. It suggests that horses involved in competition can provide a good model to study the exercise-induced stress response.
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Stull, C. L., Spier, S. J., Aldridge, B. M., Blanchard, M., & Stott, J. L. (2004). Immunological response to long-term transport stress in mature horses and effects of adaptogenic dietary supplementation as an immunomodulator. Equine Veterinary Journal, 36(7), 583–589.
Abstract: Reasons for performing study: Little information exists on the immunological effects of transport or the use of supplements to minimise transport stress. Objectives: To establish baseline ranges and evaluate immunophenotypic and functional changes associated with transport and a nutritional ‘adaptogen’ supplement. Methods: Horses received either supplement (n = 10) or placebos (n = 9) during the 30 day study. After 28 days in stalls, 12 horses (6 supplement; 6 placebo) were transported for 24 h, then unloaded and recovered. Venous blood samples were collected on Days 1, 14 and 28 to establish baselines, and on Days 28, 29 and 30 to examine changes during transport and recovery. Results: Transport prompted elevations (P<0.05) in cortisol concentration, neutrophil count and white blood cell counts, while lymphocyte subpopulation counts (CD3+, CD4+, CD8+, CD21+) decreased (P<0.05). Normal phenotypic lymphocyte profiles returned within 24 h of recovery. Supplement effects on immunophenotype (CD21+ and CD8+) were observed in stabled horses (P<0.05), but not in transported horses. Conclusions: These results provide insights into the immunological mechanisms associated with long-term transport. Potential relevance: The existence of a small window of immunological uncertainty follows long-term transportation, enhancing the potential risk of infectious disease in susceptible individuals.
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Weishaupt, M. A., Wiestner, T., von Peinen, K., Waldern, N., Roepstorff, L., van Weeren, R., et al. (2006). Effect of head and neck position on vertical ground reaction forces and interlimb coordination in the dressage horse ridden at walk and trot on a treadmill. Equine Vet J Suppl, (36), 387–392.
Abstract: REASONS FOR PERFORMING STUDY: Little is known in quantitative terms about the influence of different head-neck positions (HNPs) on the loading pattern of the locomotor apparatus. Therefore it is difficult to predict whether a specific riding technique is beneficial for the horse or if it may increase the risk for injury. OBJECTIVE: To improve the understanding of forelimb-hindlimb balance and its underlying temporal changes in relation to different head and neck positions. METHODS: Vertical ground reaction force and time parameters of each limb were measured in 7 high level dressage horses while being ridden at walk and trot on an instrumented treadmill in 6 predetermined HNPs: HNP1 – free, unrestrained with loose reins; HNP2 – neck raised, bridge of the nose in front of the vertical; HNP3 – neck raised, bridge of the nose behind the vertical; HNP4 – neck lowered and flexed, bridge of the nose considerably behind the vertical; HNP5 – neck extremely elevated and bridge of the nose considerably in front of the vertical; HNP6 – neck and head extended forward and downward. Positions were judged by a qualified dressage judge. HNPs were assessed by comparing the data to a velocity-matched reference HNP (HNP2). Differences were tested using paired t test or Wilcoxon signed rank test (P<0.05). RESULTS: At the walk, stride duration and overreach distance increased in HNP1, but decreased in HNP3 and HNP5. Stride impulse was shifted to the forehand in HNP1 and HNP6, but shifted to the hindquarters in HNP5. At the trot, stride duration increased in HNP4 and HNP5. Overreach distance was shorter in HNP4. Stride impulse shifted to the hindquarters in HNP5. In HNP1 peak forces decreased in the forelimbs; in HNP5 peak forces increased in fore- and hindlimbs. CONCLUSIONS: HNP5 had the biggest impact on limb timing and load distribution and behaved inversely to HNP1 and HNP6. Shortening of forelimb stance duration in HNP5 increased peak forces although the percentage of stride impulse carried by the forelimbs decreased. POTENTIAL RELEVANCE: An extremely high HNP affects functionality much more than an extremely low neck.
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