bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pulmonary capillary pressure in horses undergoing alteration of pleural pressure by imposition of various upper airway resistive loads
Authors: DUCHARME N. G. , HACKETT R. P. , GLEED R. D. , AINSWORTH D. M. , ERB H. N. , MITCHELL L. M. , SODERHOLM L. V. 
Published: June 2010

SummaryWe hypothesised that changes in pleural pressure induced by resistive breathing would affect transmural pulmonary artery, pulmonary capillary, and pulmonary wedge pressures. Seven horses were assigned to exercise with each of 4 upper respiratory resistive loads in random order at intervals of at least 2 days: 1) control — no added resistive loads; 2) inspiratory resistive load (Iobst) — left laryngeal hemiplegia; 3) expiratory resistive load (Eobst) — one‐way valve in the right nostril; and 4) combined inspiratory and expiratory resistive loads (CIEobst) — left nostril occlusion. On each occasion, the horses performed an incremental exercise protocol consisting of exercise episodes of 3 min duration at 75, 90, and 100% of maximal heart rate (HRmax). Pulmonary artery and oesophageal pressures were recorded continuously. Subsequent analysis was carried out on the pulmonary arterial pressure signal with the oesophageal pressure signal subtracted, hence the pulmonary vascular pressures in this paper approximate transmural pressures. Pulmonary vascular pressures, heart rate, and arterial blood gas tensions were measured at each level of exercise. Pulmonary capillary and pulmonary wedge pressures were determined from the pulmonary artery waveform after dynamic occlusion of a branch of the pulmonary artery.During exercise, peak expiratory oesophageal pressure was more positive in horses with Eobstand CIEobst(adjusted means=43, and 39 mmHg, respectively) compared with control (adjusted mean=23 mmHg) (P = 0.0001). Peak inspiratory oesophageal pressure was more negative in horses at exercise with Iobstand CIEobst(adjusted means=‐42 and ‐39 mmHg, respectively) compared with control (adjusted mean=‐26 mmHg)(P = 0.0012). Eobstwas associated with an increase in mean oesophageal pressure while Iobstwas associated with a decrease in mean oesophageal pressure. There were significant increases in mean pulmonary artery pressure in horses with CIEobst(adjusted means = 82 mmHg) and in pulmonary wedge pressure in horses with CIEobstand Iobst(adjusted means=51, and 55 mmHg, respectively) when compared to control (73 and 42 mmHg, respectively) (P = 0.0001). Pulmonary capillary pressure was significantly increased in horses with CIEobstor Iobst(adjusted means=61 mmHg, 63 mmHg, respectively) when compared to control (adjusted mean=50 mmHg)(P = 0.0001). At maximal exercise intensity with inspiratory obstruction, the mean oesophageal (pleural) pressure was ‐17 mmHg while the mean pulmonary capillary pressure was 77 mmHg. The latter exceeds the reported 75 mmHg threshold for capillary failure in horses. We conclude that inspiratory resistive breathing can lead to a significant increase in transmural pulmonary capillary pressure which may contribute to loss of capillary integrity and rupture.
Influence of girth strap tensions on athletic performance of racehorses
Authors: BOWERS J. R. , SLOCOMBE R. F. 
Published: June 2010

SummaryEight horses were exercised at speeds to produce 80% of maximal heart rates, on 4 occasions using a randomised block design, and girthed at tensions of approximately 5, 10, 15 or 20 kg using a standard canvas girth attached to a racing saddle. Tension was recorded continuously using an in‐line load cell connected to a physiograph. Horses ran until fatigued on a treadmill inclined at 10% slope. Tensions were measured at peak inhalation (T/inh) and exhalation (T/exh), recorded at rest (rest) and during exercise (ex). Data were analysed by ANOVA and, in addition, least squares linear regression was performed to determine the relationship between distance travelled, time to fatigue and the recorded maximum tensions at inhalation and minimum tensions at exhalation. For T/inhrest, every increase in girth tension by 1 kg was associated with a reduction in distance to fatigue by 98.3 ± 28.6 m and a corresponding reduction in run times of 0.24 ± 0.07 min (P = 0.01).Results for T/exhrestwere similar, with a reduction of mean ± s.e. 81.3 ± 26.9m and 0.20 ± 0.07 min per 1 kg increase in tension (P = 0.02). The mean distances to fatigue for the T/exhrestof 5, 10, 15 and 20 kg were 6624, 5812, 5268 and 5405 m respectively. These data indicate that distances to fatigue are similar once T/exhrestequals or exceeds 10 kg. Based on this study, resting girth tensions less than 10 kg are optimal for performance, but from our survey data, tensions exceeding this tension are typical for Thoroughbred racing in Victoria.
The effects of training on ventilation and blood gases in exercising Thoroughbreds
Authors: ROBERTS C. A. , MARLIN D. J. , LEKEUX P. 
Published: June 2010

SummaryThe effects of training on ventilation and blood gases during exercise were investigated in 6 clinically normal, detrained Thoroughbred horses. They underwent a 16 week training programme similar to the type frequently used for Thoroughbred racehorses in Great Britain. Standardised treadmill exercise tests (2 min canter at 8 and 10 m/s [C8 and C10] and 2 min gallop at 12 m/s [G12], on a level surface) were performed prior to and after 16 weeks of training. Respiratory flow rates were measured using ultrasound flow transducers. Blood samples were drawn from a transverse facial artery and the right atrium. Minute ventilation, respiratory frequency and tidal volume were not significantly altered by training. Peak inspiratory flow rate was lower following training at 8 and 10 m/s, but not at 12 m/s. Arterial oxygen tension was decreased during trot and canter following training. Blood lactate concentration post G12 decreased following training (10.5 ± 2.2 mmol/l vs. 7.7 ± 2.2 mmol/l; P<.05). The increase in the degree of exercise‐induced arterial hypoxaemia following training may reflect a lack of pulmonary adaptation to training in the face of improved cardiovascular and muscular function.
Functional and compositional changes in pulmonary surfactant in response to exercise
Authors: MORRISON KIRSTEN E. , SLOCOMBE R. F. , McKANE S. A. , DARGAVILLE P. A. 
Published: June 2010

SummaryPulmonary surfactant from bronchoalveolar lavages was obtained from 2 groups of horses. A control group consisting of 6 healthy racehorses that were paddock‐rested and lavaged weekly for 6 consecutive weeks were compared with an experimental group of 10 healthy racehorses, lavaged weekly the same period, consisting of a 5 week incremental‐intensity treadmill training programme and one week post training paddock rest. Phospholipid content of lavage fluid was determined indirectly by phosphorus assay, and surfactant functional activity was determined by bubble surfactometry. Total cell counts and differential cell percentages of lavage fluid were adjusted to reflect the dilution of alveolar epithelial lining fluid (ELF) using the lavage/serum urea ratio, and data were analysed per volume of ELF. There was no change in phospholipid content for either group, but some horses had consistently greater amounts than did others, ranging from 17.2–64.4 μg/μl. From the exercised group ELF had both increased nucleated cell numbers due to increased macrophage numbers, and increased numbers of erythrocytes. Surface tension increased significantly over the exercise protocol, but not in controls. Functional activity of surfactant varied between horses, independent of phospholipid content, with average values for individuals ranging 10.5–29.5 mN/m. We conclude that exercise of sufficient intensity to induce intrapulmonary haemorrhage also leads to functional decreases in surfactant activity, without affecting phospholipid content. This study also indicates that functional differences in surfactant exist between horses and may be a risk factor for development of exercise‐induced pulmonary haemorrhage.
Effect of exercise and COPD crisis on isoprostane concentration in plasma and bronchoalveolar lavage fluid in horses
Authors: KIRSCHVINK NATHALIE , ART TATIANA , SMITH NICOLA , LEKEUX P. 
Published: June 2010

SummaryTo test whether isoprostanes could be used as markers of oxidative stress in horses, their concentration was determined in plasma and in pulmonary epithelial lining fluid (PELF) in 3 models of oxidative stress: (1) strenuous exercise, (2) acute COPD crisis and (3) exercise combined with COPD crisis. Four horses were investigated twice, once in crisis and once in remission. The animals underwent a standardised treadmill exercise test. Isoprostane assessment was performed in plasma and bronchoalveolar lavage fluid 24 h before and 1 h after exercise and in plasma also immediately after exercise. Exercise in remission induced a significant increase of isoprostanes in plasma and in PELF. In horses in crisis, the isoprostane concentrations did not increase in plasma, while they did increase in PELF. Lastly, exercise in crisis increased plasma levels of isoprostanes, but did not change PELF isoprostanes. In conclusion, 1) isoprostanes are increased by systemic oxidative stress induced by strenuous exercise in COPD horses in remission either in PELF or in plasma; 2) only PELF and not plasma isoprostanes are increased by pulmonary oxidative stress induced by COPD crisis and 3) unexpectedly, exercise in crisis increased plasma but not PELF isoprostanes.
Gas exchange during exercise in Standardbred trotters with mild bronchiolitis
Authors: NYMAN GÖREL , BJÖRK MADELEINE , FUNKQUIST PIA 
Published: June 2010

SummaryTo 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

SummaryWe 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

SummaryBecause 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

SummaryGround 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

SummaryThe 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

SummaryThe 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

SummaryAn 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.