bluuebunny/crossref_metadata_2025 huggingface dataset:
Uric acid responses to endurance racing and relationships with performance, plasma biochemistry and metabolic alterations
Authors: CASTEJÓN F. , TRIGO P. , MUÑOZ A. , RIBER C.
Published: June 2010

Reasons for performing study: There is limited understanding of the uric acid response to endurance races.

Objectives: To demonstrate uric acid increments and its relationship to diverse biochemical and performance parameters, in horses subjected to a prolonged effort, with and without presentation of metabolic alterations.

Methods: Blood samples were taken from horses the day before, and 5–10 mins after, successfully finishing a 121 km (Assay 1, n = 24) or 164 km endurance race (Assay 2, n = 17), and from 19 animals eliminated by metabolic disorders during several endurance races (Assay 3). Plasma was obtained and determinations of CK, AST, LDH, AP, uric acid (UA), creatinine (Cr), urea, lactate (La) and plasma proteins (PP) carried out. Sex, age, time in competition, average speed and total recovery time were also recorded. Assays 1 and 2 were arithmetically subdivided into 3 groups each in order to categorise time in competition, average speed and total recovery time. Changes among the groups were evaluated with ANOVA and Fisher's PLSD test. Student's paired t test was used to assess pre‐ and post exercise differences. A value of P0.05 was considered significantly different. Pearson correlation coefficient was used to assess the relationship between all the variables and UA increases.

Results: Average speed of the sampled horses was significantly higher in Assay 1 compared to Assay 2. However, there were no significant differences in plasma biochemistry values between both groups. The fastest horses showed significantly higher UA levels, compared with the slowest (Assays 1 and 2) and medium horses (Assay 1). The animals with alterations in metabolism had significantly higher UA, CK and PP compared with those that adequately concluded the race. There were significant correlations between UA and CK in Assays 1, 2, and 3 and between UA and PP in Assays 1 and 3.

Conclusions: UA rises in horses after a prolonged effort, this increase being higher in animals with metabolic commitment, and in the fastest horses. This increase has a direct correlation with CK.

Potential relevance: UA could be useful in the assessment of metabolic response during endurance exercise.
Heart rate responses during acclimation of horses to water treadmill exercise
Authors: NANKERVIS K. J. , WILLIAMS R. J.
Published: June 2010

Reasons for performing study:The use of water treadmill exercise in horses is popular, although little is known about the physiological responses to this form of exercise. No information exists regarding the time taken to acclimate to water treadmill exercise compared to that of high‐speed treadmill exercise, for both physiological and biomechanical parameters.

Objective:To determine heart rate responses during acclimation to water treadmill exercise with and without sedation on first time exposure.

Methods:All horses were exercised on a water treadmill at the walk for 15 min once a day for 4 days. Fourteen horses (mean ± s.d. age 9 ± 3.2 years) were assigned randomly toGroup A(sedated) andGroup B(nonsedated). Group A were given 20–30 μg/kg bwt romifidine within 10–15 min prior to the start of the first acclimating run. Acclimation was determined by the time taken to reach a threshold heart rate value.

Results:Group A and B reached threshold heart rate values by the 6th minute of the 4th run (72.8 beats/min) and the 6th min of the 3rd run (78.7 beats/min), respectively. No significant difference was found (P>0.05) betweenGroup AandBin the time taken to reach threshold heart rate values. Acclimation to water treadmill exercise requires a minimum of 2 times 15 min nonsedated acclimating runs. Sedation can be used to prevent horses panicking during the first exposure but thereafter does not affect the time taken to acclimate.

Potential relevance:Previous experience of water treadmill exercise should be taken into consideration prior to collecting physiological and biomechanical data. Further studies detailing the physiological and biomechanical responses are required prior to making recommendations for the incorporation of this mode of exercise into rehabilitation programmes.
Measurements of right ventricular internal dimensions and their relationships to severity of tricuspid valve regurgitation in National Hunt Thoroughbreds
Authors: HELWEGEN M. M. G. H. J. , YOUNG L. E. , ROGERS K. , WOOD J. L. N.
Published: June 2010

Reasons for performing study:The effect of tricuspid valve regurgitation (TR) in right ventricular (RV) chamber size has not been reported.

Methods:An echocardiographic and auscultation study was conducted on 394 race‐fit National Hunt Thoroughbreds (TBs) in 4 training yards. Auscultation was performed on each horse and audible murmurs of TR graded using a 1–6 scale. Echocardiography was also performed and standard, 2‐dimensional (2D), short (SA) and long axis (LA) images of the RV obtained from a right parasternal location. An m‐mode image was recorded from an SA view of the RV just below the level of the tricuspid valve. Colour flow Doppler (CFD) echocardiography was used to interrogate the tricuspid valve and right atrium. If retrograde flow was visible, representative recordings were also acquired. Severity of TR by CFD was graded using a subjective 1–9 scale. Measurements of RV chamber size in systole and diastole were made from archived 2D, LA, SA and m‐mode images by a single observer unaware of the auscultation and CFD findings. To determine day‐to‐day repeatability of RV measurements from each imaging plane and of TR by CFD, 5 horses were examined on 5 consecutive days using an identical echocardiographic protocol. Images from 30 horses in the original dataset were also measured on a second occasion to determine the intra‐observer repeatability.

Results:There were significant positive correlations between the severity of TR by CFD and RV internal diameter from each image plane. In contrast, there were no significant associations between grade of TR by auscultation and any RV dimension. Data also showed that only RV measurements derived from M‐mode images have acceptable intra‐observer repeatability and similarly the M‐mode measurements had the best overall day‐to‐day repeatability.

Conclusions and clinical relevance:Data showed that TR assessed by CFD was positively associated with the diastolic and systolic dimensions of the RV, but failed to demonstrate a positive association between the presence of a murmur of TR and RV chamber size. M‐mode and 2D echocardiography provided moderately reliable and repeatable methods for obtaining measurements of RV internal dimensions. M‐mode images provide the most reliable and repeatable measurements, particularly for less experienced operators.
Effects of a specific endothelin‐1Aantagonist on exercise‐induced pulmonary haemorrhage (EIPH) in Thoroughbred horses
Authors: PADILLA D. J. , EPP T. S. , McDONOUGH P. , MARLIN D. J. , ERICKSON H. H. , POOLE D. C.
Published: June 2010

Reasons for performing study:During high intensity exercise, the very high pulmonary artery pressure (Ppa) experienced by Thoroughbred horses is considered a major factor in the aetiology of exercise‐induced pulmonary haemorrhage (EIPH). Recently, endothelin‐1 (ET‐1), a potent vasoconstrictive hormone, has been found to increase Ppa in horses at rest via binding to its ET‐1Areceptor subtype. In addition, plasma concentrations of ET‐1 are increased in horses during and after high intensity exercise.

Hypothesis:If ET‐1 increases Ppa during exercise in the horse, administration of a specific ET‐1Aantagonist would decrease Ppa and therefore EIPH.

Methods:Saline (CON) or an ET‐1Areceptor antagonist, TBC3214 (3 mg/kg bwt i.v.; ANTAG) was administered to horses 1 h prior to maximal incremental exercise on a highspeed treadmill. Gas exchange measurements were made breath‐by‐breath and blood samples collected during each 1 min stage to determine blood gases, acid‐base status and cardiac output. EIPH was determined via bronchoalveolar lavage (BAL) ˜30 min after exercise.

Results:The time to fatigue, gas exchange and cardiovascular responses were not different between groups (P>0.05). Resting and peak Ppa did not differ significantly between treatments. Most importantly, ANTAG did not decrease EIPH.

Conclusions:These results do not support a deterministic role for ET‐1 in the increased Ppa and therefore EIPH, during maximal exercise in the equine athlete.

Potential relevance:Treatment with an ET‐1Areceptor antagonist does not appear to be a viable therapeutic intervention in the prevention of EIPH.
Synthesis of proglycogen and macroglycogen in skeletal muscle of Standardbred trotters after intermittent exercise
Authors: BRÖJER J. , HOLM S. , JONASSON R. , HEDENSTRÖM U. , ESSÉN‐GUSTAVSSON B.
Published: June 2010

Reasons for performing study: The degradation of glycogen and its two forms, proglycogen (PG) and macroglycogen (MG) has been studied in horses performing different types of exercise, but no information is available about the resynthesis of PG and MG after exercise.

Objectives: To determine the resynthesis of PG and MG in skeletal muscle after intermittent uphill exercise.

Methods: At a training camp 9 well‐trained Standardbred trotters performed a training session comprising a warm‐up period, 7 repeated 500 m bouts of exercise on an uphill slope and a recovery period. Muscle biopsies (m. gluteus medius) for analysis of PG, MG, glucose and glucose‐6‐phosphate were taken at rest, at the end of exercise and 1, 4, 8, 24, 48 and 72 h post exercise. Blood samples for analysis of glucose, lactate and insulin were collected before exercise, immediately after the last bout of exercise and then as for the muscle biopsies.

Results: The MG and PG concentration pre‐exercise was 311 ± 47 and 305 ± 55 mmol/kg dwt respectively. The exercise caused a decrease in PG (Δ 63 ± 26 mmol/kg dwt) and MG (Δ 136 ± 68 mmol/kg dwt). Immediately after the last sprint plasma glucose and lactate increased compared to values pre‐exercise. During the first hour post exercise there was a further decrease in MG in 7 out of 9 horses. The rate of glycogen resynthesis during 1–24 h was higher for MG than for PG. The rate of muscle glycogen resynthesis thereafter was slower and did not differ between MG and PG up to 72 h.

Conclusion: After repeated bouts of exercise on a slope, resynthesis of glycogen is a slow process and the resynthesis of proglycogen differs from that of macroglycogen. The fraction most depleted during exercise (MG) had no resynthesis during the first hour of recovery but then had the highest rate of resynthesis during the remainder of the first 24 h period.

Potential relevance: If the time between exercise sessions during training is too short the recovery period will be inadequate for complete restoration of muscle glycogen.
Recruitment pattern of muscle fibre type during flat and sloped treadmill running in Thoroughbred horses
Authors: ETO D. , YAMANO S. , HIRAGA A. , MIYATA H.
Published: June 2010

Reasons for performing the study:There is little information about the muscle fibre recruitment pattern during sloped and flat track running in Thoroughbred horses.

Objectives:To examine the glycogen depletion pattern of each muscle fibre type during running on a flat and sloped treadmill.

Methods:Thirteen Thoroughbred horses (3–9 years old) were used. They were initially subjected to incremental exercise tests on a treadmill at 10 and 0% inclines in each horse to determine running speed at 90 and 60% VO2max. Needle biopsy samples were obtained from the middle gluteal muscle immediately after the running at 90% VO2maxfor 4 min and 60% VO2maxfor 12 min on 10% and 0% inclines treadmill. Four muscle fibre types (Types I, IIA, IIA/IIX, andIIX) were immunohistochemically identified, and optical density of Periodic Acid Schiff staining (OD‐PAS) in each fibre type and the glycogen content of the muscle sample were determined by quantitative histochemical and biochemical procedures.

Results:The changes in OD‐PAS showed that the recruitment of all fibre types were identical after each exercise bout, i.e., 4 min running at 90% VO2max(8.4–9.4 m/sec on 10%, 13.9–14.1 m/sec on 0%), and 12 min running at 60% VO2max(5.4–6.0 m/sec on 10%, 7.9–11.2 m/sec on 0%). No significant differences were found in the recruitment patterns of each muscle fibre type between 10 and 0% inclined exercise bouts at the same exercise intensity.

Conclusions:The recruitment pattern of muscle fibre type is mainly determined by exercise intensity (%VO2max) and duration, but not by running speed.

Potential relevance:The results of this study indicate the possibility that up‐hill running results in the same training effect as faster running on a flat track.
Energetic cost of locomotion on different equine treadmills
Authors: JONES J. H. , OHMURA H. , STANLEY S. D. , HIRAGA A.
Published: June 2010

Reason for performing study:Human athletes run faster and experience fewer injuries when running on surfaces with a stiffness ‘tuned’ to their bodies. We questioned if the same might be true for horses, and if so, would running on surfaces of different stiffness cause a measurable change in the amount of energy required to move at a given speed?

Hypothesis:Different brands of commercial treadmills have pans of unequal stiffness, and this difference would result in different metabolic power requirements to locomote at a given speed.

Methods:We tested for differences in stiffness between a Mustang 2200 and a Säto I commercial treadmill by incrementally loading each treadmill near the centre of the pan with fixed weights and measuring the displacement of the pan as weights were added or removed from the pan. We trained six 3‐year‐old Thoroughbreds to run on the 2 treadmills. After 4 months the horses ran with reproducible specific maximum rates of O2consumption (VO2max/kg bwt, 2.62 ± 0.23 (s.d.) mlO2STPD/sec/kg) at 14.2 ± 0.7 (s.d.) m/sec. They were alternately run on the 2 treadmills at identical grade (0.40 ± 0.02%) and speeds (1.83 (walk), 4.0 (trot) and 8.0 (canter) m/sec, all ± 0.03 m/sec) while wearing an open‐flow mask for measurement of VO2.

Results:The Mustang treadmill was over 6 times stiffer than the Säto. The VO2/kg bwt increased by approximately 4‐fold over the range of speeds studied on both treadmills. Oxygen consumption was significantly lower at all speeds for the Mustang treadmill compared to the Säto. The fractional difference in energy cost decreased by a factor of 6 with increasing speed, although absolute difference in cost was relatively constant.

Conclusions:We suggest it costs less energy for horses to walk, trot or canter on a stiffer treadmill than on a more compliant treadmill, at least within the ranges of stiffness evaluated.

Potential relevance:It may be possible to define a substrate stiffness ‘tuned’ to a horse's body enabling maximal energetic economy when running. The differences between treadmills allows more accurate comparisons between physiological studies conducted on treadmills of different stiffness, and might help to identify an ideal track stiffness to reduce locomotor injuries in equine athletes.
Method for quantifying net anaerobic power in exercising horses
Authors: OHMURA H. , HIRAGA A. , JONES J. H.
Published: June 2010

Reason for performing study:There is no good method for measuring net anaerobic power in exercising horses to allow accurate estimates of total metabolic power.

Hypothesis:The increase in VO2maxwhen breathing hyperoxic (HO) gas should be accompanied by a stoichiometrically equal (in terms of ATP turnover, i.e. energy equivalents) decrease in plasma lactate accumulation rate (Mlactate).

Methods:Six 3‐year‐old Thoroughbreds were trained on an equine treadmill wearing a semi‐open flow mask for measurement of VO2. After 4 months the horses ran with reproducible specific VO2max(VO2max/kg bwt). The mask design allowed mixing of O2or N2with the inward bias flow of gas so that inspired O2concentration of the horse could be controlled. While the horse breathed either HO (25.1% O2), normoxic (NO, 21% O2) or hypoxic (LO, 19.5% O2) gas, it ran at a speed sufficient to elicit VO2maxin NO while jugular venous blood was drawn at 15 sec intervals over a period of 2 min to determineMlactate.

Results:VO2max/kg bwt was not significantly different between LO and NO conditions, and LO data could not be used in the comparison. The VO2max/kg bwt increased from 2.59 ± 0.24 (s.d.) to 2.86 ± 0.24 mlO2(STPD)/sec/kg in NO and HO, respectively, whileMlactatedecreased from 11.5 ± 4.2 to 9.0 ± 3.9 mmol/min as VO2increased.

Conclusions:The ratio of ΔMlactateto Δ VO2max/kg bwt suggests thatMlactateof approx 11.1 ± 6.7 mmol/min is associated with net anaerobic power approximately equivalent to 1.0 mlO2(STPD)/sec/kg of aerobic power (20.1 W/kg−1). The high variability in VO2max/kg bwt observed in data from some runs, particularly in LO, suggests that caution must be used when comparing data from the same horse during different runs.

Potential relevance:This study provides a tool for estimating net anaerobic power and, more accurately, evaluating total metabolic power of horses exercising at or above their aerobic capacities.
A pattern recognition approach for the quantification of horse and rider interactions
Authors: SCHÖLLHORN W. I. , PEHAM C. , LICKA T. , SCHEIDL M.
Published: June 2010

Reasons for performing study: Interactions of various systems were investigated in several studies of dynamic systems, but the interactions between horse and rider have not yet been documented. These interactions include the rider's ability to control the horse, adapt to the horse and maintain both participants' body position. An optimum interaction is also adapted to the individual nature of the horse.

Objective: To identify rider‐horse interactions by means of artificial neural nets analysing the time‐continuous pattern.

Methods: Fourteen horses were measured trotting on hand, and ridden at working trot with a professional and a recreational rider using a 3D high speed video system (120 Hz)1. Angles were calculated after low pass filtering (5–20 Hz). Horse movements were described by 2D angles, angular velocities, and angular accelerations of variables of the right body side: hind and front fetlock, head, back and the summation angle of carpus, elbow, and shoulder, the summation angle of hock, stifle, and hip. Distances between the trajectories of the feature vectors in an N = 11 times 11 Kohonen map were determined and analysed by means of a cluster analysis.

Results: Depending on the variables included, both rider specific as well as horse specific movement patterns could be identified. The time courses of the head angle indicate a movement pattern mainly dominated by the rider, whereas the time courses of variables of the hind fetlock and hock in most cases did not show differences between the conditions with, and without, rider. The skill of the professional rider could be documented with a higher adaptation to the horse's movement pattern.

Conclusion and potential relevance: The presented time course oriented approach provides a sensitive tool in order to quantify the interaction of rider and horse.
Association of type of sport and performance level with anatomical site of orthopaedic injury diagnosis
Authors: MURRAY R. C. , DYSON S. J. , TRANQUILLE C. , ADAMS V.
Published: June 2010

Reason for performing study:Although anecdotal reports of increased orthopaedic injury risk in equine sports exist, there is little scientific evidence to support this.

Objectives:To test whether horses undertaking a single competitive sport have increased risk of specific injuries compared to those used for general purpose riding (GP); and whether injury type varies with sport category and performance level.

Methods:Data from 1069 records of horses undergoing orthopaedic evaluation (1998–2003) and meeting inclusion criteria were reviewed. Sport category (GP, showjumping, dressage, eventing, racing), level (nonelite or elite) and diagnosis were recorded. Effects of sport category and level on probability of a specific diagnosis were assessed using chisquared tests. Logistic regression was used to determine which competitive sports and levels increased risk of injury compared with GP.

Results:Overall there was a significant effect of sport category and level on diagnosis (P<0.0001). There was significant difference between anatomical site injured and sport category (P<0.0001); a high risk of forelimb superficial digital flexor tendon injury in elite eventing (P<0.0001) and elite showjumping (P=0.02); distal deep digital flexor tendon (DDFT) injury in elite showjumping (P=0.002); and hindlimb suspensory ligament injury in elite (P<0.0001) and nonelite (P=0.001) dressage. There was a low risk of tarsal injury in elite eventing (P=0.01) and proximal DDFT injury in dressage (P = 0.01).

Conclusions:Horses competing in different sports are predisposed to specific injuries; particular sports may increase the risk of injury at certain anatomical sites; and the type and site of injury may reflect the type and level of performance.

Potential relevance:These findings could guide clinicians in the diagnosis of sport related injuries.
Abnormal radiographic findings in 865 French Standardbred trotters and their relationship to racing performance
Authors: COUROUCÉ‐MALBLANC A. , LELEU C. , BOUCHILLOUX M. , GEFFROY O.
Published: June 2010

Reason for performing study:Developmental orthopaedic lesions are commonly found in French Standardbred horses. One of the main questions asked by trainers, owners and veterinarians is what impact these lesions have on the racing career and racing performances of horses.

Objectives:To study the prevalence and distribution of developmental orthopaedic lesions in young French Standardbred trotters and to relate them to racing performance.

Methods:Feet, fetlock, tarsus and stifle regions were radiographed in 865 two‐year‐old French Standardbred trotters. Abnormal radiographic findings (ARF) were evaluated for 12 anatomical sites identified in these areas, and a severity index given. Performance criteria were: success in qualification for racing, maximal and mean index of trot (ITR), an annual index calculated on the basis of the logarithm of earnings per starts, total earnings at 5 years, placed races compared to starts and longevity of the racing career. Analysis of variance were calculated to study the relationships between racing performance and the number of ARF or the severity index.

Results:A total of 363 horses (42.0%) showed ARF. Prevalence of ARF was 18.3% in the plantar aspect of the hind fetlock and 10.6% in the proximal tarsus. Among the total population, 833 horses were considered for performance evaluation, 478 of them were qualified for racing. The number of ARF significantly affected racing longevity. However, the number of ARF did not affect performance categories according to maximal ITR. Concerning distribution of ARF, the number of plantar lesions in the fetlock significantly affected mean ITR. The index of severity did not provide more information for prognosis than the number of ARF.

Conclusion:Longevity is the only criteria affected by ARF. When evaluating different sites, only the plantar fetlock region showed a significant relationship with mean ITR.

Potential relevance:Number of ARF and radiographic score (RS) affect mean ITR and longevity but do not affect maximal ITR. A horse with a good racing ability will be a good performer but might have a racing career shortened because of orthopaedic problems in relation to developmental orthopaedic lesions.
Raising heels of hind hooves changes the equine coffin, fetlock and hock joint angle: a kinematic evaluation on the treadmill at walk and trot
Authors: PEHAM C. , GIRTLER D. , KICKER C. , LICKA T.
Published: June 2010

Reasons for performing study: Raised heels are commonly recommended for various equine orthopaedic conditions. However, the simultaneous effect of raised heels on the different joint angles of the equine hindlimb throughout the motion cycle has not been previously evaluated.

Objective: To document the simultaneous effect of raised heels on the joint angles of the equine hindlimb coffin, fetlock and hock joints.

Methods: Eight sound, adult, Warmblood horses were evaluated barefoot and with a heel wedge of 8 or 16°, walking and trotting on a horizontal treadmill. Markers placed on the dorsal and cranial aspect of the hindlimb were traced using a 3D high speed video system and joint angles calculated.

Results: The effects of raising the hindlimb heels by 8 or 16° on the angles of the hindlimb during the stance phase are a reduction of the plantar combined coffin joint and pastern joint angle, a reduction of maximum extension in the fetlock joint, and an increase in maximum hock flexion. The relation between angles did not change significantly during the course of the stance phase in the three measurement situations, with only small differences in time of occurrence of each joint angle maxima and minima.

Conclusions: Raising the heels of hind hooves increases flexion of the coffin and hock joints during the stance phases of walk and trot, and a doubling of the angle of the raised heels also doubles the effect on the joint angles investigated. Raised heels reduce the maximum extension of the fetlock joint during the the stance phase at walk and trot.

Potential relevance: This study provides evidence for the therapeutic use of raised shoes with heels in horses with pain on maximum hock extension, e.g. spavin.
Exercise‐induced pulmonary haemorrhage during submaximal exercise
Authors: EPP T. S. , McDONOUGH P. , PADILLA D. J. , GENTILE J. M. , EDWARDS K. L. , ERICKSON H. H. , POOLE D. C.
Published: June 2010

Reasons for performing study:Maximally exercising horses achieve mean pulmonary artery pressures (Ppamean) that exceed the minimum threshold (75 mmHg) estimated for pulmonary capillary rupture and exercise‐induced pulmonary haemorrhage (EIPH). EIPH is not expected to occur during moderate submaximal exercise (i.e. 40–60% VO2max) since Ppameanremains well below this threshold.

Hypothesis:Prolonged submaximal exercise (trotting) would precipitate locomotory respiratory uncoupling and cause EIPH. This would be present as a result of the most negative intrapleural pressures (as estimated by the minimum oesophageal pressure; Pœsmin) occurring simultaneously with the most positive Ppa (Ppapeak) to produce estimated maximal pulmonary artery transmural pressures (PATMPmax) that surpass the EIPH threshold.

Methods:Five Thoroughbred horses trotted to fatigue (˜25 min) at 5 m/sec on a 10% incline. Ventilation (VE), Pœs, and Ppa were measured at 5 min intervals, and bronchoalveolar lavage (BAL) red blood cells (RBCs) were quantified 45 min post exercise.

Results:BAL revealed an increased EIPH (rest: 2.0 ± 1 times 105, exercise: 17 ± 10 times 105RBCs/ml BALF; P<0.05), despite the highest Ppameanreaching only mean ± s.e. 55 ± 3 mmHg, while VE, tidal volume and Pœsminapproached 70–80% of the values achieved at maximal running speeds (10% incline: 12–13 m/sec) by these same horses. The resulting PATMPmaxwas well above the level considered causative of EIPH.

Conclusions:The finding of significant EIPH during submaximal exercise broadens the spectrum of performance horses susceptible to EIPH and supports studies that suggest that extravascular factors are of primary importance in the aetiology of EIPH.

Potential relevance:Consideration of strategies such as the equine nasal strip for reducing negative extravascular pressures is warranted even for exercise at moderate intensities.
Effects of chronic acetazolamide administration on fluid flux from the pulmonary vasculature at rest and during exercise in horses
Authors: VENGUST M. , STAEMPFLI H. , VIEL L. , HEIGENHAUSER G.
Published: June 2010

Reasons for performing study:Horses develop high pulmonary pressures during exercise, which force fluid out of pulmonary capillaries. Specific airway diseases in horses, especially those associated with hypoxaemia, hypercapnoea and acidosis may influence pulmonary haemodynamics and pulmonary interstitial fluid equilibrium.

Objectives:This study was designed to determine fluid flux (JV‐Al/min) across the lung in exercising horses treated chronically with acetazolamide.

Methods:Six horses were exercised on a treadmill until fatigue without (Con) and with chronic carbonic anhydrase (CA) inhibition (AczTr) and associated hypercapnoea and acidosis. Carbonic anhydrase inhibition was achieved with administration of acetazolamide (Acz). Arterial and mixed venous blood were sampled, and V̇CO2and V̇O2measured. Blood volume changes across the lung (ΔBV%) were calculated from changes in plasma protein, haemoglobin and packed cell volume (PCV). Cardiac output (Q̇) was calculated using Fick principle.JV‐Aacross the alveolar‐capillary barrier was then quantified based on Q̇ and ΔBV. Variables were analysed using 2‐way repeated‐measures ANOVA (P<0.05). A significant F ratio was further analysed using Tukeypost hocanalysis.

Results:Treatment had a significant effect onJV‐A(P = 0.002). At rest there was noJV‐Ain Con (0.63 ± 0.6 l/min) and AczTr (0.84 ± 0.3 l/min). During exercise Con fluid moved from the pulmonary circulation into the pulmonary interstitium (mean ± s.e.JV‐A9.4 ± 2.4 l/min). This was different from AczTr (mean ± s.e.JV‐A1.8 ± 1.9 l/min), where no transvascular fluxes from pulmonary circulation were present during exercise (P = 0.008).

Conclusions:Chronic Acz treatment with associated hypercapnoea and acidosis affectsJV‐Ain lungs of exercising horses. Lung fluid dynamics adapted to hypercapnoea and acidosis with reduction of fluid flow from the pulmonary circulation.

Potential relevance: The current data provide comprehensive evidence ofin vivofluid homeostasis in lungs of exercising horses without and with CA inhibition.
Prevalence of inflammatory airway disease in National Hunt horses referred for investigation of poor athletic performance
Authors: ALLEN K. J. , TREMAINE W. H. , FRANKLIN S. H.
Published: June 2010

Reasons for performing study: Inflammatory airway disease (IAD) is thought to be an important cause of poor performance in young Thoroughbred racehorses. However, little study has been made of IAD in older National Hunt (NH) horses.

Objectives: To determine the prevalence of IAD in NH racehorses referred for investigation of poor athletic performance and identify some of the risk factors that may be associated with IAD in this group of horses.

Methods: Tracheal mucus was graded, and tracheal wash (TW) and bronchoalveolar lavage (BAL) performed after treadmill exercise in 91 NH horses referred to the University of Bristol. Comparisons were made between the different methods for diagnosing IAD and potential risk factors investigated.

Results:Tracheal mucus was observed in 68% and lower airway inflammation identified in 70% of horses. There was poor agreement between TW and BAL techniques for a diagnosis of IAD. The prevalence of increased proportions of neutrophils in TW was 40% compared with 59% in BAL. There was a significant association between presence of tracheal mucus and increased neutrophils in TW but not between tracheal mucus and BAL cytology. No significant association between IAD and age, EIPH or URT obstruction was observed.

Conclusions: Inflammatory airway disease was a common finding in NH horses referred for investigation of poor performance. In contrast to studies in younger, flat racehorses the prevalence of disease did not decrease with increasing age.

Potential relevance: Horses of all ages presented for investigation of poor performance require a thorough clinical investigation of the lower airways. The collection of both TW and BAL samples is indicated in order to confirm a diagnosis of IAD.
Factors influencing variation in locomotor‐respiratory coupling in Standardbred Trotters in the field
Authors: COTREL C. , LELEU C. , COUROUCE‐MALBLANC A.
Published: June 2010

Reasons for performing study:A close relationship between limb and respiratory rhythms has been shown in clinically healthy galloping horses due to mechanical constraints in the thoracic region. This synchronisation leads to a 1/1 ratio between stride frequency (SF) and respiratory frequency (RF) during galloping. Very little is known about locomotor‐respiratory coupling (LRC) during fast trot.

Objectives:To investigate stride and respiratory rates during a standardised exercise test on the track in Standardbred Trotters.

Methods:Forty‐four French trotters age 2–10 years performed a standardised exercise test consisting of three 3 min steps at constant speeds. Speed (V) of exercise varied between 500 and 750 m/min. Variables measured during exercise: SF, heart rate, RF using a microphone between the nostrils, blood lactate concentration. Physiological variables V4and V200were calculated and race performance index recorded.

Results:There was no age‐related difference in RF or in LRC. Two LRC strategies were found: around 1/1 ratio and 3/2 ratio between SF and RF, respectively. A relationship between SF/RF ratio and physiological parameters showed a higher LRC in good performers because of a lower RF during submaximal and maximal exercise.

Conclusion:RF is significantly lower and LRC significantly higher in good compared to poor performers.

Potential relevance:Investigation is required to ensure that the breathing techniques of trotters may be used in the selection process of racehorses.
Effects of dietary energy source and physical conditioning on insulin sensitivity and glucose tolerance in Standardbred horses
Authors: PRATT S. E. , GEOR R. J. , McCUTCHEON L. J.
Published: June 2010

Reasons for performing study: There is evidence that adaptation to diets rich in nonstructural carbohydrates (NSC) contributes to the development of insulin resistance in horses. To date, however, no study in horses has examined the effects of physical conditioning on diet‐associated alterations in insulin sensitivity and glucose tolerance.

Objectives:To examine the effects of adaptation to concentrate feeds rich in NSC or fat on insulin sensitivity and glucose tolerance in horses, both in the sedentary state and after a subsequent period of physical conditioning.

Methods: Fourteen mature Standardbred horses underwent both a euglycaemic‐hyperinsulinaemic clamp (EHC) and oral glucose tolerance test (OGTT) after each of the following phases:Baseline‐ fed only forage cubes for 3 weeks;Diet‐ horses were randomly assigned to receive either a high NSC (S) concentrate or a high fat concentrate (F) with forage cubes for 6 weeks; andDiet x Exercise‐ horses remained on the assigned ration and underwent a 7 week period of physical conditioning. An incremental exercise test was performed before, and after, theDiet x Exercisephase for measurement of the peak rate of oxygen consumption (V̇O2peak).

Results:In both diet groups, there was an approximately 10% increase in mean V̇O2peakafter physical conditioning. The mean rate of glucose disposal (M) per unit of serum insulin (I) during the EHC [M/I ratio] in S horses was 30% lower (P<0.05) in theDietphase when compared toBaseline, but not different fromBaselineafter physical conditioning. The S diet also resulted in a greater (P<0.05) OGTT insulin response (area under the insulin vs. time curve, AUCINS) in bothDietandDiet x Exercisephases when compared toBaseline. In F, insulin sensitivity (mean M/I ratio) and glucose tolerance were unchanged during the study.

Conclusions and potential relevance:Feeding a diet rich in NSC for 6 weeks resulted in decreased insulin sensitivity and impaired glucose tolerance. Physical conditioning lessened the effects of the high NSC diet on insulin sensitivity, as evidenced by the return to baseline M/I, but did not mitigate the impaired glucose tolerance. Decreased insulin sensitivity has been implicated in the development of obesity and laminitis in horses and the present findings provide support for avoidance of concentrates with high NSC in the dietary management of horses at risk for the development of these conditions.
Interval exercise alters feed intake as well as leptin and ghrelin concentrations in Standardbred mares
Authors: GORDON M. E. , McKEEVER K. H. , BOKMAN S. , BETROS C. L. , MANSO‐FILHO H. , LIBURT N. , STRELTSOVA J.
Published: June 2010

Reasons for performing study: Horses in training tend to become inappetant; however, the mechanism responsible for this training‐induced inappetance is not known.

Hypothesis: Training and/or ulcers alter the feed intake (FI) and hormonal and/or biochemical (active ghrelin, leptin, glucose, insulin and cortisol) responses to acute high intensity exercise.

Methods: Eight Standardbred mares underwent 3 interval exercise tests (IET) and 3 parallel control tests (CON) before (IET1) and after 8 weeks of training (IET2) and after treatment for gastric ulcers (IET3). Plasma samples were taken before (0 min), during (last 10 sec of velocities eliciting 40, 100 and 20% VO2max), and after (30 min, 60 min, 24 h) exercise (EX) or CON tests for RIA and colorimetric measurement of the concentrations of the above parameters. Samples were also collected before and after feeding. Horses were trained at a work intensity of 70% HRmaxfor 30 min/day, 5 days per week with FI measured daily.

Results:There were no changes (P>0.05) in any variable during the parallel control trials. However, there was a mismatch between FI and digestible energy (DE) requirements (P<0.05) with EX horses not meeting their DE requirements during the post training IETs. During all IETs, ghrelin, glucose and cortisol increased (P<0.05) during EX. Leptin only increased (P<0.05) during EX in the post training IETs. Insulin remained low during EX, but increased (P<0.05) post EX.

Conclusion: High intensity exercise appeared to be associated with decreases in FI and alterations of leptin and ghrelin.

Potential relevance: More research is needed to determine if there is a relationship between alterations of these hormones and changes in FI in horses that lose weight while in training.
Oral vitamin E supplementation on oxidative stress, vitamin and antioxidant status in intensely exercised horses
Authors: WILLIAMS C. A. , CARLUCCI S. A.
Published: June 2010

Reasons for performing study: Vitamin E is the most commonly supplemented antioxidant in horses; however, previous research is not conclusive as to the recommended level for exercising horses.

Objective: To evaluate the effects of 3 levels of vitamin E supplementation on oxidative stress and vitamin/antioxidant status in intensely exercised horses to determine the optimal level of vitamin E supplementation.

Methods: Twelve unfit Standardbreds were divided into 3 groups, supplemented orally with 0 (CON), 5000 (MOD), or 10,000 (HI) iu/day of DL‐α‐tocopheryl acetate. The 3 times 3 Latin square design consisted of three 4 week supplementation periods with 4 week wash out periods between. After each period, horses underwent a treadmill interval exercise test. Blood samples were collected and heart rate (HR) measured before, during and after exercise. Data were analysed using ANOVA with repeated measures in SAS.

Results: The CON group had lower HR throughout the test compared to the MOD and HI groups (P<0.05). There was an increase in plasma retinol (RET), β‐carotene (BC), red blood cell total glutathione and glutathione peroxidase with exercise (P<0.05), but all groups returned to baseline after 24 h. Plasma α‐tocopherol (TOC) increased from baseline with exercise (P<0.0001) in all groups; treatment differences were observed at 24 h (P<0.05). The HI and CON groups had lower BC compared to the MOD group (P = 0.05).

Conclusions: Horses supplemented with vitamin E, at nearly 10‐times the 1989 NRC recommended level, did not experience lower oxidative stress compared to control horses. Additionally, lower plasma BC levels observed in the HI group, which may indicate that vitamin E has an inhibitory effect on BC metabolism.

Potential relevance: Supplementation above control levels is not more beneficial to oxidative stress and antioxidant status in intensely exercising horses; indeed, levels 10 times in excess may be detrimental to BC and should be avoided.
CD3+ and BLA.36+ cells do not occur in the epidermis and adnexal epithelia of normal equine skin
Authors: TRANCHINA M. M. , SCOTT D. W. , McDONOUGH S. P.
Published: June 2010

A small population of resident T lymphocytes is present in the healthy human and murine epidermis. However, resident epidermal lymphocytes have not been reported in normal skin of the horse. Skin biopsy specimens from the normal skin of 27 horses were examined histologically and immunohistochemically for the presence of lymphocytes, CD3+ cells and BLA.36+ cells in epidermis and adnexal epithelia. All examinations were negative. It appears that lymphocytes occur rarely, if at all, in the epidermis and adnexal epithelia of normal horse skin. Hence, the presence of lymphocytes in these structures should be considered abnormal.
Distinctive properties of CXC chemokine receptor 4‐expressing Cajal–Retzius cells versus GABAergic interneurons of the postnatal hippocampus
Authors: Marchionni Ivan , Takács Virág T. , Nunzi Maria Grazia , Mugnaini Enrico , Miller Richard J. , Maccaferri Gianmaria
Published: June 2010

The CXC chemokine receptor 4 (CXCR4) for the chemokine (C‐X‐C motif) ligand 12/stromal cell‐derived factor‐1 α (CXCL12/SDF‐1 α) is highly expressed in the postnatal CA1 stratum lacunosum‐moleculare. However, both the network events triggered by SDF‐1 α in this microcircuit and the cellular targets of this chemokine remain virtually unexplored. Here, we have studied SDF‐1 α‐mediated neuromodulation of the stratum lacunosum‐moleculare by directly comparing the properties of CXCR4‐expressing Cajal–Retzius cells vs. CXCR4‐non‐expressing interneurons, and by recording the electrophysiological effects caused by application of SDF‐1 α on either cell type. We demonstrate that SDF‐1 α dramatically reduces spontaneous firing in Cajal–Retzius cells via hyerpolarization, and that cessation of firing is prevented by the CXCR4‐specific antagonist AMD3100. In contrast, no effects on the excitability of interneurons of the same layer were observed following exposure to the chemokine. We also provide evidence that, despite the expression of functional glutamate receptors, Cajal–Retzius cells are integrated in the synaptic network of the stratum lacunosum‐moleculare via excitatory GABAergic input. Furthermore, we show that the axons of Cajal–Retzius cells target specifically the stratum lacunosum‐moleculare and the dentate gyrus, but lack postsynaptic specializations opposite to their axonal varicosities. These results, taken together with our observation that SDF‐1 α reduces evoked field responses at the entorhinal cortex–CA1 synapse, suggest that Cajal–Retzius cells produce a diffuse output that may impact information processing of stratum lacunosum‐moleculare. We propose that pathological alterations of local levels of SDF‐1 α or CXCR4 expression may affect the functions of an important hippocampal microcircuit.
Error-Controlled Model Reduction in Flexible Multibody Dynamics
Authors: Fehr Jörg , Eberhard Peter
Published: June 2010

One important issue for the simulation of flexible multibody systems is the quality controlled reduction in the flexible bodies degrees of freedom. In this work, the procedure is based on knowledge about the error induced by model reduction. For modal reduction, no error bound is available. For Gramian matrix based reduction methods, analytical error bounds can be developed. However, due to numerical reasons, the dominant eigenvectors of the Gramian matrix have to be approximated. Within this paper, two different methods are presented for this purpose. For moment matching methods, the development of a priori error bounds is still an active field of research. In this paper, an error estimator based on a new second order adaptive global Arnoldi algorithm is introduced and further assists the user in the reduction process. We evaluate and compare those methods by reducing the flexible degrees of freedom of a rack used for active vibration damping of a scanning tunneling microscope.
Optimal Control Strategies for Robust Certification
Authors: Leyendecker Sigrid , Lucas Leonard J. , Owhadi Houman , Ortiz Michael
Published: June 2010

We present an optimal control methodology, which we refer to as concentration-of-measure optimal control (COMOC), that seeks to minimize a concentration-of-measure upper bound on the probability of failure of a system. The systems under consideration are characterized by a single performance measure that depends on random inputs through a known response function. For these systems, concentration-of-measure upper bound on the probability of failure of a system can be formulated in terms of the mean performance measure and a system diameter that measures the uncertainty in the operation of the system. COMOC then seeks to determine the optimal controls that maximize the confidence in the safe operation of the system, defined as the ratio of the design margin, which is measured by the difference between the mean performance and the design threshold, to the system uncertainty, which is measured by the system diameter. This strategy has been assessed in the case of a robot-arm maneuver for which the performance measure of interest is assumed to be the placement accuracy of the arm tip. The ability of COMOC to significantly increase the design confidence in that particular example of application is demonstrated.
Stochastic Modeling in Multibody Dynamics: Aerodynamic Loads on Ground Vehicles
Authors: Wetzel Christian , Proppe Carsten
Published: June 2010

The influence of wind loads on the driving behavior of ground vehicles is an important economical, safety, and comfort issue. The crosswind performance is of great interest, as violent lateral winds can cause major accidents or will at least make the driver and the passengers feel very uncomfortable and insecure. In this paper, a sampling based methodology for the analysis of stochastic ground vehicle systems is presented. Starting from the well known Monte Carlo method more sophisticated reliability methods with higher efficiency are introduced and their advantages and drawbacks are critically reviewed. Furthermore, probabilistic sensitivity analyses are presented, which can be used to quantify the importance of the random variables on the response of the vehicle system. The influence of the parameters of the probability density functions is investigated by means of a novel response surface method. The mentioned approach is applied to a nonlinear road vehicle model under strong crosswind excitation for which the failure probabilities and the sensitivities are computed.
Variational Integrators and Energy-Momentum Schemes for Flexible Multibody Dynamics
Authors: Betsch Peter , Hesch Christian , Sänger Nicolas , Uhlar Stefan
Published: June 2010

This work contains a comparison between variational integrators and energy-momentum schemes for flexible multibody dynamics. In this connection, a specific “rotationless” formulation of flexible multibody dynamics is employed. Flexible components such as continuum bodies and geometrically exact beams and shells are discretized in space by using nonlinear finite element methods. The motion of the resulting discrete systems are governed by a uniform set of differential-algebraic equations (DAEs). This makes possible the application and comparison of previously developed structure-preserving methods for the numerical integration of the DAEs. In particular, we apply a specific variational integrator and an energy-momentum scheme. The performance of both integrators is assessed in the context of three representative numerical examples.