bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas exchange during exercise in Standardbred trotters with mild bronchiolitis
Authors: NYMAN GÖREL , BJÖRK MADELEINE , FUNKQUIST PIA
Published: June 2010

To investigate the gas exchange response during exercise in horses with mild bronchiolitis (MB), we studied 7 Standardbred trotters. In order to determine pulmonary gas exchange and red cell volume in relation to bodyweight (CV/BW), submaximal graded exercise tests were performed. V̇o2was monitored from an open bias flow system without valves. Heart rate, respiratory rate and mean pulmonary and systemic artery pressures were measured. Cardiac output and alveolar ventilation were calculated. Arterial and mixed venous blood were drawn for blood gas analysis and pH measurements. Pulmonary gas exchange was assessed by conventional blood gas variables, and the ventilation‐perfusion distribution was estimated using the multiple inert gas elimination technique. The dispersion of perfusion and ventilation distribution and the difference between measured arterial oxygen tension and that predicted on the basis of the amount of ventilation‐perfusion mismatching and shunt were determined in order to reflect diffusion limitation. The results were compared, using analysis of variance, with data from an earlier study on healthy Standardbred trotters (LH) during a similar exercise test No differences in pulmonary gas exchange were obtained between LH and MB. However, CV/BW, pulmonary artery mean pressure (PAP) and systemic arterial mean pressure (SAP) were significantly higher in MB than in LH. Lactate concentration, arteriovenous oxygen content differences [C(a‐v)o2] and pH were significantly lower in MB horses than in LH. We conclude that Standardbred trotters with mild subclinical bronchiolitis can achieve an adequate gas exchange compared to healthy Standardbred trotters, during a graded exercise test; however, the significantly increased CV/BW in MB horses may be a compensatory mechanism for hypoxaemia during maximal work.
Pre‐ and post exercise echocardiography in horses performing treadmill exercise in cool and hot/humid conditions
Authors: MARR CELIA M. , BRIGHT JAN M. , MARLIN D. J. , HARRIS PAT A. , ROBERTS C. A.
Published: June 2010

We hypothesised that exercise in a hot and humid environment would affect echocardiography; indices of cardiac dimensions and funtion more than exercise in a cool envirmonment. M‐mode echocardiograms were obtained in 5 clinically normal horses before, and at 0, 10, 30 and 60 min after a treadmill exercise test. The test was performed in a controlled environment at 20°C/40% relative humidity (RH) and again at 30°C/80% RH. All the horses completed the exercise test in cool conditions, but only one horse completed the exercise test in the hot/humid environment. The relaxation time index (RTI) correlated significantly and inversely with heart rate (HR). Heart rate was increased and RTI was decreased immediately after exercise in cool conditions. HR recovery appeared to be prolonged following exercise in hot/humid conditions. Post exercise RTI was significantly decreased in hot/humid environment. In hot/humid conditions, the left ventricular internal dimensions measured in diastole and systole (LVIDd, LVIDs) were reduced following exercise and continued to fall throughout the 60 min after exercise. The left ventricular fractional shortening (FS%) was lower than resting levels immediately after exercise in hot/humid conditions. Significant decreases were found in LVIDs and LVIDd, which may reflect a reduction in preload arising from dehydration or re‐distribution of blood throughout the recoveryperiod following exercise in the hot/humid environment. It was concluded that echocardiography was a useful tool in assessing cardiac responses to exercise in different climates.
Effects of phlebotomy and autologous blood transfusion on oxygen transport in the racehorse
Authors: KNIGHT P. K. , RAY SHIRLEY P. , ROSE R. J.
Published: June 2010

Because the haemoglobin concentration [Hb] during exercise may be at the upper limit of blood viscosity for effective oxygen delivery, we hypothesised that administration of blood would not further enhance oxygen delivery or exercise capacity. Six Thoroughbred geldings were used in 5 incremental treadmill exercise tests over a period of 4 weeks. The first test was performed 6 days prior to phlebotomy, which involved the removal of 20 ml/kg bwt of venous blood. Exercise tests were performed at 1, 8 and 15 days after blood removal. Six days after the 15 day post phlebotomy exercise test, blood from each horse was reinfused and the final test performed 24 h after blood reinfusion. During the 3 weeks following blood collection, the blood, collected into acid citrate dextrose, was stored at 3°C. Each exercise test involved measurements of arterial and mixed venous blood gases, plasma lactate concentrations, heart rate and V̇o2 using an open flow system. Cardiac output was measured by direct Fick. The removal and reinfusion of blood had significant effects on packed cell volume (PCV) with the lowest PCV value during exercise of 0.57 ± 0.04 l/l being recorded in the second post phlebotomy test and the highest value of 0.67 ± 0.04 l/l found after blood reinfusion. There were no significant effects of phlebotomy or blood reinfusion on arterial blood gas values. However, arteriovenous oxygen content difference was significantly altered by phlebotomy and reinfusion. The maximal values during the 3 tests following phlebotomy were significantly lower (P<.05) by about 7% than those before phlebotomy and after blood reinfusion, mirroring the alterations in [Hb]. There was no significant effect of phlebotomy or blood reinfusion on heart rate but stroke volume was significantly higher (P<.01) during the 3 post phlebotomy tests than for the control or blood reinfusion tests. There was no significant effect of phlebotomy or blood reinfusion on either the submaximal or maximal values for V̇o2. No significant effect of blood removal or reinfusion was found on the treadmill run time to fatigue. We concluded that haemodynamic adjustments following phlebotomy or blood reinfusion maintained oxygen delivery during exercise. No detrimental effects on exercise capacity were found from phlebotomy nor beneficial effects from autologous blood transfusion. However, it should be noted that the extent of change induced in [Hb] was relatively small and with the number of horses in the study, the experimental power was not great.
The effects of a rider's mass on ground reaction forces and fetlock kinematics at the trot
Authors: CLAYTON HILARY M. , LANOVAZ J. L. , SCHAMHARDT H. C. , VAN WESSUM R.
Published: June 2010

Ground reaction force (GRF) measurements are often normalised to body mass to facilitate inter‐individual comparisons. The objective of this study was to explore the effect of a rider on the GRFs and fetlock joint kinematics of trotting horses. The subjects were 5 dressage‐trained horses and 3 experienced dressage riders. Ground reaction force measurements and sagittal view videotapes were recorded as the horses trotted at the same velocity in hand (3.49 ± 0.52 m/s) and with a rider (3.49 ± 0.46 m/s). Data were time‐normalised to stance duration. Ground reaction force measurements were expressed in absolute terms and normalised to the system mass (horse or horse plus rider). All the horses showed changes in the same direction when comparing the ridden condition with the in‐hand condition. There was an increase in the absolute peak vertical GRFs of the fore‐ and hindlimbs with a rider. However, the mass‐normalised peak vertical GRFs were lower for the ridden condition, with the peak occurring later in the forelimbs and earlier in the hindlimbs compared with the in‐hand condition. Maximal fetlock angle and its time of occurrence were similar for the 2 conditions, but the fore fetlock joint was more extended during the later part of the stance phase in ridden horses. The presence of a rider appeared to affect the GRFs and fetlock joint kinematics differently in the fore‐ and hindlimbs, and the ridden horse did not seem to be equivalent to a proportionately larger horse. This should be considered when normalising for body mass in studies comparing horses in hand and ridden horses.
Forelimb kinematics and net joint moments during the swing phase of the trot
Authors: LANOVAZ J. L. , CLAYTON HILARY M. , COLBORNE G. R. , SCHAMHARDT H. C.
Published: June 2010

The purpose of this study was to calculate net moments of force at the joints of the forelimb during the swing phase of the stride. An optoelectronic system was used to measure segmental kinematics for 3 strides in 5 sound, Warmblood horses trotting at a mean velocity ± s.d. of 3.03 ± 0.16 m/s. A link segment model was used to determine the net moments of force about the joints of the left forelimb. The model combined kinematic data with morphometric data describing the inertial parameters of the limb segments of warmblood horses, and incorporated correction factors for skin displacement. At each joint the net moment of force was on the cranial/dorsal side during the early swing phase and on the caudal/palmar side during the later swing phase. The transition (time of zero moment) occurred between 35–52% of the swing phase. The peak magnitude of the net joint moments decreased progressively in a proximal to distal direction. Published electromyographic (EMG) data correlated well with the timing of muscular activity required to generate the calculated net joint moments. The moments in the proximal limb are indicative of muscular activity accelerating the limb forward during the first 30–40% of the swing phase, then decelerating the forward swing of the upper limb segments. The net joint moments at all of the joints except the elbow work to slow the motion of the joints. The net joint moment about the elbow actively flex and then extend the joint The low net joint moments at the distal joints during the first half of swing are consistent with their motion being primarily a result of inertial forces. Flexor muscle activity during the last half of swing indicate active control in preparation for ground contact.
A comparison between the trot of pony and horse foals to characterise equine locomotion at young age
Authors: BACK W. , SCHAMHARDT H. C. , VAN WEEREN P. R. , BARNEVELD A.
Published: June 2010

The trot at 3 m/s of 24 Shetland foals (‘ponies’) and 24 Dutch Warmblood foals (‘horses’) was recorded at age 4 months on a treadmill using a modified CODA‐3 apparatus to characterise equine locomotion at young age. Locomotor variables of the ponies were qualitatively and, after scaling, quantitatively compared with those of horses.

Ponies made shorter strides than horses, evidenced by a shorter stance and swing duration, although their relative stance durations were similar. Neither linear nor dynamic scaling procedures could completely compensate for differences in height at the withers comparing ponies and horses. The patterns of the joint angle‐time curves were similar. Ponies had a larger range of pro‐ and retraction, with a more protracted forelimb and a more retracted hindlimb, therefore demonstrating a more extended trot The horses trotted with more extended elbow, stifle and tarsal joints and a more flexed hip joint, which is in accordance with the conformation for the Warmblood. The ponies moved with a stiffer trot in contrast to the more supple trot of the horses, which showed a larger maximal fetlock extension during the stance phase.

In conclusion, ponies and horses move qualitatively similarly at age 4 months, but characteristic breed differences in conformation and gait quality can already be detected. Scaling methods to compensate for differences in height at the withers cannot be applied when animals move at the same velocity.
In vitro transmission and attenuation of impact vibrations in the distal forelimb
Authors: WILLEMEN M. A. , JACOBS M. W. H. , SCHAMHARDT H. C.
Published: June 2010

An in vitro model was developed and validated in vivo to quantify the attenuation of impact vibrations, transmitted through the lower equine forelimb and to assess the effects of horseshoeing on this attenuation. The transsected forelimbs of 13 horses were equipped with custom‐made hollow bone screws in the 4 distal bones, on each of which a tri‐axial accelerometer could be mounted. The limbs were then preloaded while the impact was simulated by dropping a weight on the steel plate on which the hoof was resting. At the hoof wall, the distal, middle and proximal phalanx and at the metacarpal bone, the shock waves resulting from this impact were quantified. To assess the damping effects of shoeing, measurements were performed with unshod hooves, hooves shod with a normal flat shoe and hooves shod with an equisoft pad and a silicone packing between hoof and pad.

The in vitro model was validated by performing in vivo measurements using one horse, and subjecting the limb of this horse to the same in vitro measurements after death. Approximately 67% of the damping of impact vibrations took place at the interface between the hoof wall and the distal phalanx. The attenuation of impact vibrations at the distal and proximal interphalangeal joints was considerably less (both 6%), while at the metacarpophalangeal joint 9% of the amplitude of that at the hoof wall was absorbed, leaving approximately 13% of the initial amplitude at the hoof wall detectable at the metacarpus. Compared to unshod hooves the amplitude at the hoof wall is 15% higher in shod hooves. No differences could be observed between shoe types. At the level of the first phalanx and metacarpus the difference between shod and unshod vanished; it was therefore concluded that, although shoeing might influence the amplitude of impact vibrations at the hoof wall, the effect of shoeing on the amplitude at the level of the metacarpophalangeal joint is minimal.
Temporal changes in the trot between the first and third horse inspections at a CCI*** 3‐day event
Authors: ROGERS C. W. , DAVIES A. S. , PFEIFFER D. U. , DAVIE P. S.
Published: June 2010

Kinematic parameters were measured from horses competing in a CCI*** 3‐day event The horses were filmed during the first and third horse inspection. This provided a repeat sample on 16 horses. The horses were filmed using a panning lateral S‐VHS video camera (50 Hz). Spatial measurements were taken for mean ± s.d. 5.66 ± 0.92 strides for the first inspection and 5.05 ± 1.27 for the third inspection. Within the calibration zone, data of the horses accelerating and obtaining a constant velocity were collected. The horses trotted with a higher mean velocity during the third inspection (0.26 ± 0.05 m/s, P<.001). During the third inspection the horses trotted with a shorter stride length (0.193 ± 0.03 m., P<.001) and stride duration (31 ± 42 m/s, P<.001). The third inspection was characterised by a decrease in retraction percentage for both the forelimbs (3.69 ± 2.39%, P<.001) and the hindlimbs (2.48 ± 2.16%, P<.001). However, no significant difference was found between the 2 inspections for other temporal parameters when measured as a percentage of stride. It is proposed that the event horses trot with a decreased stride length and duration during the third horse inspection but maintain a consistent temporal relationship.
Effects of flunixin on movement and performance of Standardbred trotters on the track
Authors: KALLINGS P. , JOHNSTON C. , DREVEMO S.
Published: June 2010

An often discussed and controversial issue is the effect of nonsteroidal anti‐inflammatory drugs (NSAIDs) on performance. The purpose of this study was to investigate the effect of the NSAID flunixin on the movement pattern and performance capacity of Standardbred trotters using a standardised track model. Five adult Standardbred horses in training trotted at 2 occasions with a 2 week interval on the same oval dirt track. Before each occasion the horses were either injected with flunixin meglumine (Finadyne) or normal saline solution i.m. 4 h before the performance test (double blind crossover study). The kinematics for 5 consecutive strides were filmed. There was no significant difference in maximal speed between the saline and flunixin treatment sessions. Significant changes in the movement pattern were observed as an effect of the flunixin treatment The horses maintained the same stride duration while significantly decreasing stance time and increasing swing time in the forelimbs. The horses' range of limb angle decreased significantly. Heart rates were monitored and plasma lactate and flunixin concentrations were measured. No significant differences were found in heart rate and plasma lactate. The results indicate that flunixin had a significant effect on locomotor pattern while it did not effect metabolic response in these horses (considered to represent a normal race track population). The overall effect on performance in racing horses may therefore be related to the anti‐inflammatory and analgesic properties of NSAIDs by masking pain and lameness.
The effect of shoeing on kinetics and kinematics during the stance phase
Authors: ROEPSTORFF L. , JOHNSTON C. , DREVEMO S.
Published: June 2010

The increasing range of of horseshoes and hoofpads makes it important to be able to evaluate their influence on performance and stress in the locomotor apparatus. The aim of this study was to describe the changes in ground reaction forces and locomotion pattern during the stance phase due to the application of a standard iron shoe. Six Swedish Warmblood horses were evaluated kinetically and kinematically before and after they were shod with an 8 mm iron shoe. Data were used to calculate ground reaction forces in the vertical and cranio‐caudal directions, point of application of the force, hoof segment angle and hoof joint, pastern joint, fetlock, carpal and tarsal angles. Finally joint angular velocity and landing velocity of the hoof were calculated.

During the initial phase of the stance or the concussion phase, the horses altered the conditions of the limb, as reflected by hoof‐landing velocities. Concussion‐dampening mechanisms of the distal limb subsequently were altered. In the nonshod condition, the coffin and fetlock joints rotated more rapidly in the forelimb and less rapidly in the hindlimb, while earlier proximal off‐loading by the carpus and tarsus resulted in a decrease in initial horizontal loading at the hoof.

It was concluded that horses accustomed to standard iron shoes demonstrate slight but significant differences in the movement and loading of the distal limb due to shoeing. Though the main differences were related to the concussion phase of the stance, even mid‐stance loading and roll‐over were altered. The study provides a basis for further investigation of the effect of various farriery techniques on the hoof and movement of the horse.
Heritability of percentage of fast myosin heavy chains in skeletal muscles and relationship with performance
Authors: BARREY E. , VALETTE J. P. , JOUGLIN M. , BLOUIN C. , LANGLOIS B.
Published: June 2010

The purpose of this study was to determine the percentage of fast myosin heavy chains (fast MHCs = MHC 2A+2B) in 2 propelling muscles to estimate the heritability and to identify any relationship with performance. The gluteus medius and the biceps femoris muscles were biopsied in 100 related French Anglo‐Arabian horses. The percentages of slow and fast myosin heavy chains were measured using an ELISA technique. The heritability (s.e.) of the fast MHCs percentage was estimated at 13% (0.1) using a restricted maximum likelihood resolution of a mixed animal model. There were significant (P<.05) correlations between the performance level and the fast MHCs percentage of the gluteus medius and biceps femoris muscles: 0.47 and 0.34 respectively. An analysis of variance revealed a significant (P<.05) effect of performance level in gallop racing and show jumping on the fast MHCs percentage of the gluteus medius muscle. The good performers in gallop racing (75.5>69.6% fast MHCs) and show jumping (74.1>67.8% fast MHCs) had a higher percentage of fast MHCs in the gluteus medius than poor performers (P<.05). This muscular analysis could be one of the interesting physiological traits to measure for early selection of gallop racing and show jumping horses.
Exercise that induces substantial muscle glycogen depletion impairs subsequent anaerobic capacity
Authors: LACOMBE VÉRONIQUE , HINCHCLIFF K. W. , GEOR R. J. , LAUDERDALE M. A.
Published: June 2010

The purpose of this study was to develop a model of muscle glycogen depletion and to study the effect of this model on aerobic and anaerobic capacity of horses. The maximal rate of oxygen consumption (V̇o2max), maximal accumulated oxygen deficit (MAOD), muscle glycogen concentration and blood lactate concentration of 6 fit Standardbred horses were measured on 3 occasions 7 days apart (Trials 1, 2and3). BetweenTrials 2and3, strenuous exercise intended to deplete muscle glycogen was performed by exercising horses on the treadmill on 3 consecutive days. Strenuous exercise resulted in reduction of muscle glycogen concentration by at least 55% (from mean ± s.e. 155.1 ± 5.6 mmol/kg, wet weight, beforeTrial 2to 55.4 ± 5.5 mmol/kg beforeTrial 3;P<.05). V̇o2maxwas similar inTrials 2and3(140.4 ± 5.4 ml O2/kg bwt and 141.8 ml ± 6.2 ml O2/kg, respectively). Run time to fatigue during a single high‐speed exercise test (253.9 ± 33.3 s and 153.8 ± 16.4 s., P<.05), accumulated oxygen deficit (95 ± 13.2 ml O2/kg and 35 ± 13.9 ml O2/kg, P<.05) and blood lactate concentration at the end of the sprint (17 ± 1.2 mmol/l and 10.5 ± 1.1 mmol/l, P<.05) were less duringTrial 3thanTrial 2.These data suggested that repeated strenuous exercise that causes muscle glycogen depletion results in impairment of anaerobic, but not aerobic, metabolism.
Metabolic and hormonal changes after exercise in relation to muscle glycogen concentrations
Authors: PÖSÖ A. REETA , HYYPPä S.
Published: June 2010

To test whether, in horses, the concentration of muscle glycogen can be influenced by increasing the uptake of glucose into the muscle cells or by providing a gluconeogenic precursor, 9 trained half‐bred riding horses performed on a treadmill a 1.5 h competition exercise test (CET). Each horse performed CET 3 times and 30 min after CET, each was given one of the following solutions: isotonic glucose‐electrolyte (GE) solution, GE supplemented with 50 g leucine (GEL) to increase insulin secretion, or GE supplemented with 200 ml propionic acid (GEP), a gluconeogenic precursor. Administration of GE solutions caused no increase in plasma glucose concentration. The highest concentration of insulin was measured after GEL, but also in the GE group the concentration of insulin increased. GEP completely inhibited the increase in insulin concentration. Concentration of glucagon was increased 6 and 22.5 h after CET. None of the post exercise treatments influenced significantly the glycogen content at 22.5 h after CET. This indicates that neither i) elevation of insulin concentration to increase muscle‐uptake of glucose, nor ii) increase in the availability of a glucose precursor, propionic acid, was able to increase accumulation of glycogen in the middle gluteal muscle.
Incremental treadmill exercise until onset of fatigue and its relationship to metabolic response and locomotion pattern
Authors: SCHUBACK KATARINA , ESSÉN‐GUSTAVSSON BIRGITTA , PERSSON S. G. B.
Published: June 2010

The aim was to study metabolic response and locomotion pattern in Standardbred trotters during incremental treadmill exercise performed by increasing speed by 1 m/s in 1 min steps (start 7 m/s) until the onset of fatigue. The test protocol included determination of oxygen uptake, heart rate (HR), stride length (SL) and stride frequency (SF). Venous blood samples were collected at rest, at the end of each exercise step and after 30 min of recovery. Muscle biopsies were taken at rest and post exercise and muscle temperature was measured after exercise. As horses fatigued at different speed steps (9–11 m/s), variation was seen in running time (180–300 s), oxygen uptake (109–170 ml/kg bwt min), HR (200–225 beats/min), SL (4.4–5.7 m) and SF (116–130 strides/min) at the last speed step. Increased mean plasma lactate concentration (20.5 mmol/l) was seen at onset of fatigue and increased mean uric acid concentration after 30 min of recovery (112.8 μmol/l). After exercise, a decrease was seen in muscle ATP (7.1 mmol/kg d.w.), creatine phosphate (43.9 mmol/kg d.w.) and glycogen (160 mmol/kg d.w.), and an increase was seen in ADP (0.3 mmol/kg d.w.), AMP (0.18 mmol/kg d.w.), IMP (5.8 mmol/kg d.w.) and lactate (100.8 mmol/kg d.w.). At onset of fatigue, muscle temperature varied from 39.9–41.4°C. Running time correlated with SL (r=0.86), with an increase in IMP (r=0.79) and AMP (r=0.70) post exercise and with plasma uric acid concentration (r=0.74) at 30 min of recovery. SF correlated negatively with the increase in ADP after exercise (r = 0.85). The results of this study indicate that running time during incremental treadmill exercise until the onset of fatigue is related to locomotion pattern and to a marked degree of anaerobic metabolism, especially adenine nucleotide degradation.
Standardisation of muscular biopsy ofgluteus mediusin French trotters
Authors: VALETTE J. P. , BARREY E. , JOUGLIN MAGGY , COUROUCE ANNE , AUVINET B. , FLAUX B.
Published: June 2010

Morphometric measurements were taken from 41 French trotters of various ages and both sexes. Biopsy location was determined for the dorsal compartment as being one‐third of the distance from thetuber sacraleto thetuber coxaeand for the ventral compartment as being one‐third of the distance from thetuber coxaeto the caudal Cd1‐Cd2 intervertebral joint. Ten horses were biopsied at these 2 sites at a sampling depth equal to half the total depth of the compartment as measured by ultrasonography. The percentage of slow and fast myosin heavy chain fibres was measured by using an immunoenzymatic method. The depth of the dorsal and ventral compartments of thegluteus mediuswas significantly greater in males than in females. The depth of the ventral compartment was greater in the case of a straight hip than of a wide hip and was greater in young horses than in older horses. The ventral and the dorsal compartments were composed in the mid‐portion of 81.3 and 75.6% of fast myosin heavy chains, respectively. It was concluded that the locations and sampling depths in thegluteus mediuscould be standardised in French trotters by taking into account anatomical references, sex, age and width of the hip.
Sweating and skin temperature responses of normal and anhidrotic horses to intravenous adrenaline
Authors: MARLIN D. J. , SCHROTER R. C. , SCOTT CAROLINE M. , WHITE SUSAN , NYROP KAREN A. , MAYKUTH PATRICIA L. , HARRIS PAT A.
Published: June 2010

Anhidrosis has been recognised for over half a century, but despite some excellent epidemiological studies, there has been little progress in understanding the aetiology of the condition. Using a modified ventilated capsule, we obtained dynamic, quantitative data on sweating responses in anhidrotic horses and normal sweating controls from the same environment. Ten horses with current seasonal anhidrosis and 10 matched normal sweating controls were selected. Each horse was given two 10 min infusions of 1 and 2 μg/kg/min adrenaline, separated by at least 6 h. Sweating responses and skin temperatures on the neck and gluteal region were measured. Plasma and sweat for analysis of total protein and electrolytes and plasma for analysis of adrenaline were collected. Anhidrotic horses produced significantly less sweat, had lower initial and peak sweat rates and a greater neck:gluteal ratio for sweat production. Plasma adrenaline at rest or at the time of peak sweating rate was not different between groups. In nearly three‐quarters of the anhidrotic horses, the shape of the sweat rate against time curve was different compared to controls. Volume of sweat produced was significantly correlated with skin temperature on the neck of controls and anhidrotic horses and on the gluteal region of controls, but not anhidrotic horses. Plasma total protein and electrolyte concentrations were not different between groups. There were significant differences in sweat electrolyte concentrations between controls and anhidrotic horses. These differences were reduced when sweat electrolytes were expressed per g of total protein, and no differences existed when expressed as g/m2. This study has provided insight into the response of anhidrotic horses to β2 adrenergic stimulation and may be a useful technique to investigate this condition.
Frusemide and weight carriage alter the acid:base responses of horses to incremental and to brief intense exertion
Authors: HINCHCLIFF K. W. , McKEEVER K. H.
Published: June 2010

We speculated that frusemide would attenuate the acidosis associated with intense exertion, and that weight carriage would mitigate this effect. Therefore, in each of 2 experiments we measured pulmonary artery and systemic arterial blood pH, Pco2, Po2and pulmonary artery temperature in 9 horses during exertion on a treadmill after each of 3 treatments. The treatments were: 1) injection of saline solution (C), 2) injection of frusemide (1 mg/kg bwt, i.v. 4 h before running) (FU) and 3) injection of frusemide (F) as for FU and the horses carried weight equal to that lost in the 4 h after frusemide administration (FL). InExperiment 1the horses performed an incremental exercise test of 90 s at each of 4, 7 and 9 m/s (4° incline). InExperiment 2, the horses ran on a treadmill inclined at 4° for 3 min at 3 m/s, at approximately 120% V̇o2maxfor 2 min, and 3 m/s for 5 min. Blood samples for measurement of blood pH, Pco2and Po2were collected into heparinised glass syringes. Values were adjusted for changes in pulmonary artery blood temperature. Data were analysed using a 2 way repeated measures ANOVA. There was a consistent pattern in both experiments characterised by a mild alkalosis or mitigated acidosis, compared to C, at rest and during exercise and recovery after FU (P<.05). Weight carriage blunted or inhibited the effect of frusemide during exercise and recovery. Inexperiment 2, at the end of the sprint, FU treatment resulted in a less severe acidosis than did C or FL: mixed venous pH for C, FU, and FL at the end of the sprint were 6.93, 6.98 and 6.93, respectively (P interaction=0.038), mixed venous base excess was ‐12.4, ‐9.91, and ‐11.8 mmol/l, respectively, and arterial base excess of ‐14.4, ‐12.7 and ‐14.1 mmol/l (P interaction = 0.006) respectively. These effects persisted into recovery. A similar pattern of responses occurred during the incremental exercise test, with weight carriage offsetting the alkalinising effect of frusemide. We conclude that frusemide attenuates the acidosis of intense exertion and that carriage of weight prevents this effect.
Effect of feeding Thoroughbred horses a high unsaturated or saturated vegetable oil supplemented diet for 6 months following a 10 month fat acclimation
Authors: HARRIS PAT A. , PAGAN J. D. , CRANDELL KATHLEEN G. , DAVIDSON NELL
Published: June 2010

This study looked at the effect of feeding diets supplemented with either a predominantly saturated or unsaturated vegetable oil over a prolonged period to exercising horses.

Eight Thoroughbred horses were assigned to 2 diet treatments and for 10 months were fed Timothy hay and oats, together with a fortified sweet feed supplemented with either a predominantly unsaturated (Un) or a saturated (S) vegetable oil so that ˜19% DE (Digestible Energy) came from dietary fat and ˜12% from either the Un or S source (AC). An increased amount of Un or S fortified sweet feed, replacing the oats, was then fed for a further 6 months (HF) so that ˜27% DE came from fat and ˜20% from the Un or S vegetable oil. Standardised incremental treadmill exercise (8–12 m/s) tests (STEP) and duplicate oral glucose tolerance tests (TOL) were carried out after 3, 6 and 9 months of the AC diet and after 3 and 6 months on the HF diet. There was no significant effect of dietary treatment or when the tests were undertaken (time) on the insulin or lactate responses to the STEP tests. Overall there was a significant (P<.05) effect of time and treatment on the glucose response, but there was no difference between treatments at the first and last tests or between the results for these tests or between the endAC and endHF tests. No significant effect of treatment or time was seen on the TOL glucose response (% change from Time ‘0’) although there was a trend for the glucose concentrations to be lower and the insulin responses higher (nonsignificant) in the S treatment group. No significant effect of treatment on haematological parameters, monitored monthly, was found. Total protein and gamma glutamyl transferase remained within the normal range throughout. There was a significant effect of treatment (P<.05) on cholesterol and triglycerides with higher concentrations in the S group from the first (1 month) sample. Linoleic acid was the main fatty acid in all the 4 plasma lipid classes with slightly, but significant (P<.05), higher concentrations in Un for the cholesterol ester and phospholipid classes. There was no effect of time. Overall, the total resting plasma fatty acid content was significantly higher (P<.05) with S at the sample points (endAC and endHF). No adverse effects of feeding either diet on apparent coat condition or hoof appearance were seen apart from an apparent increase in the grease score. Many of the parameters assessed showed significant improvements with time (P<.05). In conclusion, no apparent adverse effects of feeding a diet supplemented with either an unsaturated or saturated vegetable oil for 6 months at ˜20% DE after 10 months at ˜12% DE were identified and there were no apparent disadvantages of feeding a saturated vegetable oil supplemented diet compared with an unsaturated one.
Phytate and phosphorus movements in the digestive tract of horses
Authors: MATSUI T. , MURAKAMI Y. , YANO H. , FUJIKAWA H. , OSAWA T. , ASAI Y.
Published: June 2010

This experiment was conducted to study phytate degradation and the effect of dietary phytate level on phosphorus absorption in the gastrointestinal tract of horses. Six Thoroughbred horses were fed diets containing low‐phytate diet or high‐phytate diet for 5 days. The diets were supplemented with Cr2O3 as an unabsorbable marker. The horses were killed 3 h after the last feeding and digesta in some segments of the intestine were collected. In both dietary' groups, the daily passage of phytate phosphorus was decreased in the upper small intestine and in the lower large intestine. The daily passage of phytate phosphorus in the lower large intestine did not differ between these groups. Although the passage of total phosphorus increased in the upper small intestine and in the upper large intestine of both groups, its passage decreased in the lower large intestine. These results suggest that phytate phosphorus is degraded in the upper small intestine and in the lower large intestine of both groups. Phosphorus is suggested to be mainly absorbed in the lower large intestine. Therefore, phytate phosphorus is considered to be easily absorbed in horses because the major site of phosphorus is the lower large intestine where most of phytate is already degraded.
The effect of diet composition and feeding state on the response to exercise in feed‐restricted horses
Authors: POWELL DEBRA , LAWRENCE L. M. , BREWSTER‐BARNES TAMMY , FITZGERALD B. , WARREN LORI K. , ROKURODA S. , PARKER A. , CRUM A.
Published: June 2010

Eight Thoroughbred horses were used to determine the effects of long‐term calorie restriction and diet composition on serum T4and T3concentrations and metabolic responses with exercise. Horses were randomly assigned to 2 treatment groups (n = 4):Group 1, horses were fed a calorie‐restricted diet designed to have 70% of the calories from the roughage source (RHR);Group 2, horses were fed a calorie‐restricted diet designed to have 70% of the calories from the concentrate source (RHC). Horses then completed 2 step‐wise exercise tests; one following a 12 h fast and one 2 h after a meal of 2 kg of a grain mix. Glucose concentrations declined (P<.01) in fed horses on the RHR diet but did not change in fed horses on the RHC diet Fasted horses receiving the RHR diet had a more rapid increase in glucose concentration during exercise compared to fasted horses receiving the RHC diet (P<.01) as well as the highest glucose concentration at fatigue (P<.05). Insulin concentrations were higher (P<.05) at fatigue in fed horses on the RHR diet Fasted horses receiving the RHR diet had higher (P<.01) pre‐exercise FFA concentrations and a more rapid decline (P<.01) in FFA during exercise. Serum T3concentrations increased (P<.01) in response to exercise within all treatments. The differences in thyroid hormone, glucose and FFA responses to exercise suggest that calorie source may be important in the hormonal regulation and energy metabolism of horses consuming calorie deficient diets.
Effects of low‐ and moderate‐intensity training on metabolic responses to exercise in Thoroughbreds
Authors: EATON M. D. , HODGSON D. R. , EVANS D. L. , ROSE R. J.
Published: June 2010

This experiment was undertaken to determine whether there were differences in cardiorespiratory, haematological and muscular responses in horses trained at either low or moderate intensities. Ten Thoroughbred horses previously rested in paddocks for 4 months were trained 5 days/week for 9 weeks. Horses were allocated randomly into fast or slow groups and exercised the same distance each day. Training distances were 1600 m in Weeks 0 and 1 up to 4000 m in Week 9. The fast group were trained at an intensity inducing a post training blood lactate of 4–8 mmol/l. This intensity was determined for each horse each week. The slow group trained at half the speed of the fast group (blood lactate <2 mmol/l). Horses performed a standardised exercise test prior to (Week 0) and on Weeks 1, 2, 3, 4, 7 and 9 of training. HR, V̇O2, V̇CO2and blood lactate concentration were recorded during the last 15 s of each step. Blood samples were collected at the end of each test for determination of red cell and plasma volume. Muscle biopsies were collected from the middle gluteal muscle before training and after 4 and 9 weeks training.

Training intensity had few effects on the majority of variables measured and results for both groups are combined unless otherwise stated. Bodyweight was unaffected by training. Economy of locomotion decreased from 12.0 ± 0.4 ml/kg bwt/m prior to training to 13.8 ± 0.6 ml/kg bwt/m at the end of training in the fast group. Run time to fatigue was not affected by training intensity. V̇O2maxincreased from 120.3 ± 4.8 to 144.7 ± 3.5 ml/kg bwt/min with a significant correlation between run time and V̇O2max. Peak HR was 221.4 ± 2.5 beats/min prior to training and 226.5 ± 1.7 beats/min after the first 4 weeks of training. V200and VLa4increased in response to training. Similarly, VLa4increased from 7.0 ± 0.5 to 9.2 ± 0.2 m/s with VLa4correlated to V̇O2max. Plasma volume decreased from 29.1 ± 1.7 to 25.8 ± 0.9 ***1 during the last 3 weeks of training. Blood volume, red cell volume and/or red cell volume/kg were unaffected by intensity or duration of training. The activity of CS in muscle increased in the first 5 weeks of training whereas HAD activity was not affected by intensity or duration of training.
Exertional rhabdomyolysis in Quarter Horses and Thoroughbreds: one syndrome, multiple aetiologies
Authors: VALBERG STEPHANIE J. , MICKELSON J. R. , GALLANT ESTHER M. , MACLEAY JENNIFER M. , LENTZ LINNEA , DE LA CORTE F.
Published: June 2010

The purpose of this study was to determine if chronic exertional rhabdomyolysis (ER) in Quarter Horses and Thoroughbreds represents one or several distinct myopathies. Eighteen Quarter Horses and 18 Thoroughbreds with ER were selected from cases presented to the Veterinary Hospital on the basis of a history of ER, assessment of muscle histopathology, and serum CK activity before and 4 h post exercise. In addition, 2 of 3 of the following parameters were evaluated: muscle glycogen concentrations, thyroid hormones (T3, T4), fractional excretion (FE) of sodium, potassium and chloride. The CK response to training, the metabolic response to a near maximal standardised exercise test (SET), blood glucose concentrations after an i.v. glucose challenge and a skeletal musclein vitrocaffeine contracture test were performed on 5 of the Quarter Horses, selected because of polysaccharide storage myopathy (PSSM), and 5 of the Thoroughbreds. Serum T3 and T4 were all within normal limits. Low FE of sodium and potassium were seen in <20% of Quarter Horses and Thoroughbreds. Four hours post exercise, CK was increased in 77% of Quarter Horses and 72% of Thoroughbreds with ER. Muscle glycogen concentrations in Quarter Horses with ER were significantly higher than in normal Quarter Horses and Thoroughbreds with ER. No Thoroughbreds, but 15/18 Quarter Horses with ER had abnormal polysaccharide accumulation in muscle biopsies consistent with a diagnosis of PSSM. PSSM Quarter Horses had higher CK activity during training than Thoroughbreds and higher glycogen utilisation with the SET. PSSM Quarter Horses also had significantly enhanced glucose clearance compared to normal Quarter Horses and Thoroughbreds with ER. Thoroughbreds with ER had significantly lower thresholds for caffeine‐induced contracture than normal horses and PSSM Quarter Horses. It was concluded that there are multiple causes for exertional rhabdomyolysis. In Quarter Horses, rhabdomyolysis is commonly due to a glycogen storage disorder, PSSM, and is readily expressed in untrained horses. In Thoroughbreds, ER is commonly due to an underlying abnormality of muscle contraction. Rhabdomyolysis in Thoroughbreds, however, is only expressed intermittently when key stressors are present.
Plasma ammonia and lactate responses using incremental and constant speed exercise tests
Authors: HARRIS R. C. , HARRIS D. B. , DUNNETT M. , HARRIS PAT A. , FALLOWFIELD J. , NAYLOR J. R. J.
Published: June 2010

Plasma NH3, formed during intense exercise, results principally from the deamination of AMP in muscle. Its formation during exercise may be influenced both by the pool of fibres recruited and by changes in the intracellular environment affecting ADP homeostasis. This study compared incremental and constant speed exercise as possible protocols for the investigation of plasma NH3accumulation with intense exercise. Six trained Thoroughbred horses, one of which had recently been operated on for recurrent laryngeal neuropathy, undertook a step‐wise treadmill test with 1 min incremental steps of 6, 8, 10, 11 and 12 m/s (7.5% incline). Two and 4 weeks later horses performed a constant‐speed, maximum‐exercise tolerance test at 115% V̇O2max(7.5% incline). Blood samples from the jugular vein were drawn at 20 s intervals in all 3 tests, for plasma NH3and lactate. There were marked differences between and within horses in their time dependant lactate and NH3responses to exercise. Three of the 6 horses studied showed a distinct threshold for onset of plasma NH3accumulation with incremental exercise. Distinct thresholds for the onset of NH3accumulation were apparent also in 5 of the 6 horses during exercise at constant rate. The present study demonstrates clearly the practicality of measuring NH3concentration curves, even during a short incremental step test which has the advantage that other measures relating to cardiovascular and respiratory functions can be measured simultaneously.
Endocrine response to exercise in young and old horses
Authors: McKEEVER K. H. , MALINOWSKI KARYN
Published: June 2010

Six young (mean + s.e., 5.3 ± 0.8 years, 445 ± 13 kg bwt) and 6 old (22.0 ± 0.4 years, 473 ± 18 kg bwt) Standardbred and Thoroughbred mares were used to test the hypothesis that age would alter the endocrine response to exercise. All of the mares were unconditioned but accustomed to the laboratory, to standing quietly and running on a treadmill, and to the standardised incremental exercise test (SET) used in the experiment. Two weeks prior to the experiment, each horse underwent a SET to determine maximal oxygen uptake (V̇O2max) and the speeds to be used in the actual experiment. A second graded exercise test (GXT) was performed without instrumentation for the measurement of plasma renin activity (PRA) and the plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin (AVP), aldosterone (ALDO), and endothelin‐1 (ET‐1). Blood samples (30 ml) were collected at rest and at the end of each one minute step of the exercise test. Plasma concentrations of hormones were measured using radioimmunoassay kits. There were no differences (P>0.05) between old vs. young mares for resting PRA (2.2 ± 0.3 vs. 1.5 ± 0.3 ng/ml/h), or the plasma concentrations of ANP (10.0 ± 0.9 vs. 10.7 ± 0.6 pg/ml); AVP (0.7 + 0.7 vs. 1.4 ± 0.4 pg/ml); ALDO (39.2 ± 10.3 vs. 22.7 ± 4.6 pg/ml); or ET‐1 (0.23 ± 0.04 vs. 0.18 ± 0.03 pg/ml). Exercise significantly increased PRA and the concentrations of ANP, AVP, and ALDO in both groups of horses; however, ET‐1 was not altered (P>0.05) by exercise in either group. There were differences (P<.05) between means obtained from the old and young groups for PRA (5.4 ± 0.6 vs. 3.9 ± 0.8 ng/ml/h and the concentrations of ANP (14.5 ± 2.3 vs. 26.5 ± 9.0 pg/ml), AVP (13.6 ± 0.3 vs. 26.1 ± 13.9 pg/ml, and ALDO (76.8 ± 22.0 vs. 41.5 ± 4.9 pg/ml) measured in samples obtained at the speed eliciting V̇O2max. These data suggest that older horses have an age‐altered endocrine response to exercise.
Effects of caffeine and promazine hydrochloride on plasma catecholamines in Thoroughbreds at rest and during treadmill exercise
Authors: KUROSAWA M. , NAGATA S. , TAKEDA F. , MIMA K. , HIRAGA A. , KAI M. , TAYA K.
Published: June 2010

Our aim was to investigate plasma catecholamine responses to so‐called ‘doping’ drugs and exercise in Thoroughbreds. Plasma adrenaline (Ad) and noradrenaline (NA) were determined after the administration of caffeine and promazine hydrochloride (PRZ) using a high performance liquid chromatographic method. Caffeine or PRZ was administered i.m. to Thoroughbreds and its effects on plasma catecholamines at rest and during exercise were compared with the saline control. The treadmill exercise was performed 1 h after administration. A dose of 5.0 mg/kg bwt caffeine was found to significantly increase both plasma Ad and NA levels but this was not the case for the 2.5 mg/kg bwt dose and their peak levels at 1.5 h were about 3 and 2.5 times as compared with the control values at 1.5 h (Ad: mean ± s.e. 21.2 ± 2.8 pg/ml, NA: 55.5 ± 4.1 pg/ml), respectively. Both 1.0 and 1.5 mg/kg bwt PRZ doses reduced the plasma Ad to below the detection limit (10 pg/ml) and significantly reduced the plasma NA. The 2.5 mg/kg bwt caffeine dose significantly increased plasma Ad and NA during exercise and approximately doubled their maximal values as compared with the saline control (Ad: mean ± s.e. 12.328 ± 4.733 ng/ml, NA: 9.997 ± 4.146 ng/ml). The 1.5 mg/kg bwt PRZ dose decreased the plasma Ad during exercise but the effect was not significant. On the other hand, PRZ significantly increased the plasma N A as compared with the saline control. In conclusion, the present study demonstrates that the plasma catecholamine responses to caffeine and PRZ were modified by exercise. It is probable that the modification may be related to exercise‐induced activation of the sympathetico‐adrenal axis.