bluuebunny/crossref_metadata_2025 huggingface dataset:
Transient respiration locomotion decoupling in galloping Thoroughbreds
Authors: JOLLY SANDRA , ART TATIANA , LEKEUX P.
Published: June 2010

The compulsory respiration locomotion coupling may sometimes be broken in healthy galloping horses, leading to a ‘big respiratory cycle’ (BRC). This work is aimed at describing the ventilatory pattern of the BRC and at studying the influence of the individual horse, gallop speed and training. Eleven healthy Thoroughbred horses were studied during a 9 week period of incremental training intensity. Instantaneous respiratory airflow, tidal volume, respiratory rate and the O2and CO2fraction in inspired and expired gases were continuously obtained on a breath‐by‐breath basis during 4 standardised treadmill exercise tests (SET) performed at 3 week intervals. The inspiratory airflow of the BRC had a bi‐ or triphasic shape and its inspiratory time was 1.5‐fold longer than that of a normal breath. The expiratory flow was monophasic and lasted 2.5‐fold longer than the normal breath. The inspiratory, but not the expiratory peak flows, remained unchanged during the BRC. The inspiratory volume was 2.0‐to 1.5‐fold higher than normal, according to the gallop speed. Each BRC was followed by a ‘readjustment cycle’ (RC), which allowed the recovery of normal respiration locomotion coupling. The sum of BRC + RC times always equalled the time for 3 normal respiratory cycles. The sum of the inspiratory volumes of BRC and RC was significantly higher than the sum of their expiratory volumes. There was a highly significant effect of horse and of training on the frequency of BRC. Lastly, during the BRC and at least the 4 following respiratory cycles, the end‐tidal O2and CO2fractions were significantly lower and higher respectively. It was hypothesised that this respiratory manoeuvre could result from a negative feedback mechanism providing, at least, transiently either a readjustment of the end expiratory lung volume or an improvement of the pulmonary gas exchange.
Plasma, red cell and whole blood lactate concentrations during prolonged treadmill exercise at Vla4
Authors: PERSSON S. G. B. , ESSÉN‐GUSTAVSSON BIRGITTA , FUNKQUIST P. , ROMERO L. BLANCO
Published: June 2010

The purposes of this study were to test whether a relatively steady state with respect to the blood lactate pool can prevail during a prolonged exercise test (PET) at Vla4, to study the kinetics of the flux of lactate between plasma and cells in relation to lactate concentration [LA] and haematocrit and to test the interrelationships between plasma [PLA], whole blood [BLA] and erythrocyte lactate [ELA]. The study used 7 Standardbred trotters. In the PET they ran at their respective pre‐established Vla4 for 12 min. Before, every 2 min during and 0, 2, 5, 10 and 15 min after exercise, [PLA] and [BLA] as well as packed cell volume (PCV) were determined. [ELA] was calculated from [PLA], [BLA] and PCV. Heart rate was monitored continuously and remained at a relatively steady state of approximately 200 beats/min throughout the PET.

Lactate concentrations increased exponentially during PET, [PLA] more rapidly than [BLA] and [ELA]. The diverging curves during exercise and converging declining curves after exercise suggested a delay in attainment of an equilibrium between plasma and cells. The close relationship between [PLA] and [BLA] (r = 0.98) allows derivations from regression equations. As the [LA] accumulation over time is exponential, it is likely that the increase during the first 2 min at any speed up to that causing a [BLA] of 4 mmol/l is marginal and insignificant and a submaximal incremental exercise test using 2 min step intervals could still be used for determination of Vla4.
Changes in haemostasis in endurance horses: detection by highly sensitive ELISA‐tests
Authors: MONREAL L. , ANGLES ANNA M. , MONREAL M. , ESPADA YVONNE , MONASTERIO J.
Published: June 2010

Exercise induced variations in coagulation and fibrinolytic activities were evaluated in 25 endurance horses competing in a 80 km ride. Venous blood samples were collected before exercise, after 40 km and 30 min after 80 km. Haematological parameters, fibrinogen, clotting times (aPTT and PT) and the main inhibitors (AT‐III and α2‐antiplasmin) activities were determined. Furthermore, we assessed thrombin‐antithrombin complexes (TAT) as a marker of coagulation activity; and fibrinogen degradation products (FgDP) and fibrin degradation products D‐dimers (FbDP) as markers of fibrinolytic activity using immunoenzymatic tests. Significant changes in all haemostatic parameters were found after endurance exercise. A significant (P < 0.001) increase of TAT values was found when comparing pre‐race (mean ± s.d. 2.28 ± 0.9), at 40 km (3.45 ± 1.2) and 30 min after 80 km (4.0 ± 1.9 ng/ml). Values of FgDP before, at 40 km and after 80 km showed a significant (P < 0.0001) decrease (mean ± s.d. 445.0 ± 144.4, 210.0 ± 111.1 and 177.7 ± 77.2 ng/ml) and the values of FbDP showed a slight but significant (P < 0.001) increase (mean ± s.d. 875.4 ± 230.9, 1062.0 ± 310.0 and 737.2 ± 305.3 ng/ml). These changes confirm a hypercoagulable state, a marked hypofibrinogenolysis and a slight hyperfibrinolysis during endurance exercise. No significant differences were found between the results from horses that finished (n / 19) and those eliminated because of fatigue (n = 6).
Factors that influence vertical velocity during take off over a water jump
Authors: COLBORNE G. R. , CLAYTON HILARY M. , LANOVAZ J.
Published: June 2010

Horses competing in the team competition at the 1992 Olympic games were videotaped as they attempted to jump a 4.5 m wide water jump. The video images were digitised to provide kinematic and centre of gravity (CG) data from 18 horses: 12 horses that cleared the water jump (Group 1) and 6 horses that failed to clear the tape on the landing side (Group 2). Univariate ANOVA revealed significant between‐group differences in horizontal distance jumped (Group 1: 5.79 m ± 0.37, Group 2: 5.03 m ± 0.34; F=0.001), inclination of the trunk segment to the horizontal at lift off of the leading hindlimb (Group 1: 21.4° ± 2.5, Group 2: 16.9° ± 4.1; F=0.011) and horizontal distance of the leading hind hoof from the horse's CG at lift off (Group 1:1.11 m ± 0.12, Group 2: 1.30 m ± 0.06; F=0.004). Pearson correlation coefficients revealed that 3 variables were highly correlated with vertical velocity at lift off: distance of the leading hind hoof from the CG at impact (r=‐0.53, P<0.05) and lift off (r=‐0.76, P<0.001) and trunk angle at lift off (r=0.70, P<0.001). Distance of the leading hind hoof from the CG at lift off and trunk angle at lift off were also significantly correlated with horizontal distance jumped (r=‐0.56, P<0.01; r/0.67, P<0.01 respectively). Stepwise multiple linear regression with vertical velocity as the dependent variable selected 3 of the 7 investigated independent variables: trunk angle, distance of the leading hindlimb from CG at lift off and distance of the leading hind hoof from the approach side of the water (r2=0.799). The position of the hindlimbs through their take off phase relative to the CG of the horse and the trunk angle at lift off are important variables in the take off over a water jump.
Kinematics of induced reversible hind and fore hoof lamenesses in horses at the trot
Authors: DEUEL N. R. , SCHAMHARDT H. C. , MERKENS H. W.
Published: June 2010

This study determined differences in hoof motion patterns of the trot between mild fore hoof lameness, mild hind hoof lameness and sound control conditions. Six sound Dutch Warmblood mares were shod with 4 steel shoes to which were welded 2 nuts inside the medial and lateral branches of the 2 right shoes. Into each nut was seated a vertical bolt which could be adjusted to alter pressure upon the hoof sole, producing transitory lamenesses of variable magnitude. Treatments were a sound control condition; a mild fore hoof lameness; a mild hind hoof lameness and another sound control following either lameness treatment. Videotapes (60 Hz) were taken from a camera aimed perpendicularly to the line of horse motion, with a metrestick taped as a reference distance. Horses were hand led at the trot for 6 trials under each treatment. A split‐plot in time model was used in an analysis of covariance, allowing treatment comparisons on an equivalent‐velocity basis. Velocities averaged 3.413 ± 0.027 m/s (mean ± s.e.); stride lengths 2.172 ± 0.017 m and stride durations 0.638 ± 0.004 s. Horses slowed and shortened their strides during lameness treatments without changing stride duration. Changes in the motion patterns of all 4 hooves occurred during fore and hind hoof lamenesses, reflecting a redistribution of weightbearing onto the 3 sound limbs. Several hoof kinematic variables measured in this study differed between mild hind and fore lamenesses but fewer variables differentiated mild lamenesses from sound conditions. The information gained from this study will be important in developing objective image‐based equine lameness diagnostic techniques.
Gait evaluation of race trotters using an accelerometric device
Authors: BARREY E. , AUVINET B. , COUROUCÉ ANNE
Published: June 2010

Some basic stride characteristics of race trotters were measured by means of an accelerometric device during a locomotor test in order to find stride parameters, predictive for race performance. Twenty‐four horses of various racing abilities were tested on the same flat racetrack. They were allocated to 3 groups according to their performance indices. The locomotor test consisted of 3 stages at increasing speeds and the third stage was performed at maximum individual speed. Basic stride variables were extracted from the acceleration data using specific procedures including built‐in functions of a data analysis programme. Some significant relationships were found between stride characteristics measured at maximum individual speed and race performances obtained during the year. The maximum speed and stride length were positively correlated (r=0.60 and 0.45, P<0.05) with the performance index. The maximum stride frequency was negatively correlated with the best time (r/‐0.46, P<0.05). The maximum speed, stride frequency, contribution of stride frequency to the speed and stride length were greater in the high performance group than in the other groups (P<0.05). The symmetry and regularity of the trot were not significantly related to the performance. A good performer should have a high maximum speed which is mainly produced by a high stride frequency greater than 2.40 strides/s. The accelerometric device was efficient for testing trotters and could be used to predict potential performance.
Muscle and blood metabolic responses to intense exercise during acute hypoxia and hyperoxia
Authors: ESSÉN‐GUSTAVSSON BIRGITTA , NYMAN G. , WAGNER P. D.
Published: June 2010

Three horses performed exercise on a treadmill under normoxic conditions (F1O2–0.21) and during exposure to acute hypoxia (F1O2–0.17) and hyperoxia (F1O2–0.35) achieved by addition of nitrogen and oxygen to inspired air by means by an open flow system. The gases were added after the horses had walked and trotted at 2 submaximal speeds (2 and 4 m/s for 7–15 min). Thereafter, the treadmill speed was increased in 3 steps to attain near maximal oxygen uptake within 5–8 min (8–10.5 m/s for normoxia and hyperoxia and 7–10 m/s for hypoxia). Heart rate and oxygen uptake were recorded continuously. By use of indwelling catheters in the pulmonary and carotid arteries, blood samples were drawn at rest and immediately after exercise. Muscle biopsies (m.gluteus) were taken before and immediately after exercise. In all horses, at the end of exercise, heart rates were lower and oxygen uptake, arterial and venous PO2, haemoglobin saturation and oxygen content were higher following hyperoxia than following hypoxia. At the end of exercise, all horses had lower concentrations of lactate, ammonia and potassium in plasma and lower lactate in muscle after hyperoxia than after hypoxia and normoxia. Concentrations of ATP were higher and of G‐6‐P lower after hyperoxia than after normoxia. Significant correlations were observed between post exercise concentrations of lactate and ammonia (r=0.80) and between lactate and potassium (r=0.96) in plasma. There was also a correlation between muscle and plasma lactate (r=0.92). Post exercise ATP concentrations were correlated with IMP (r=0.85), ammonia (r=0.94) and potassium (r=0.84) concentrations in plasma. The results indicate that acute hypoxia and hyperoxia during intense exercise influence the production and/or removal of lactate.
Lactate response to maximal exercise on the track: relation to muscle characteristics and kinematic variables
Authors: RONÉUS N. , ESSÉN‐GUSTAVSSON BIRGITTA , JOHNSTON C. , DREVEMO S. , PERSSON S.
Published: June 2010

Fourteen 2‐year‐old Standardbred trotters, born, raised and trained at the same establishment performed maximal exercise on a track over a distance of 1000 m. Blood samples for plasma lactate (PLA) analyses were obtained from the jugular vein immediately after exercise. Muscle biopsies from m. gluteus medius were taken and analysed for fibre type composition (I, IIA, IIB) and enzyme activities representing oxidative (citrate synthase (CS), 3‐OH‐ acyl‐CoA dehydrogenase (HAD)) and glycolytic (lactate dehydrogenase (LDH)) capacity. Stance time (ST), stride length (SL) and velocity were determined from high speed films (250 frames/s). Simple linear regression analysis was used to describe relationships between lactate response, muscle characteristics and basic kinematic variables. Significant positive correlations were found between PLA/IIB and negative correlations between ST/IIB, SL/PLA, ST/PLA. No relationships were observed between CS, LDH or HAD and PLA, IIB or the kinematic parameters. The results indicate that young Standardbred trotters with a low percentage of type IIB fibres perform maximal trotting with a low lactate production and long stride length and stance time.
ATP content of single muscle fibres of gluteus medius sampled at rest
Authors: HARRIS D. B. , HARRIS R. C.
Published: June 2010

ATP distribution at rest was studied in 11 Thoroughbred horses, 8 of which had been admitted for clinical post mortem examination. A biopsy of the middle gluteal muscle was obtained from 6 horses immediately after death, following which a larger piece was taken by dissection from the same area. From the other 2 horses, only cut sections were obtained. The risk of damage to fibres dissected from the inner portion of the cut samples was considered less than for fibres from biopsies. From a separate 3 standing horses, a single biopsy of the middle gluteal muscle was taken at rest. Following freeze‐drying, single fibres were dissected, weighed and analysed for ATP by luminometry. Fibre type was determined by staining for myosin ATPase. Variance in ATP content due to weighing error (se), analytical precision (sp) and the variability in content within a fibre (SDf) were determined in 16 fibres. Total variance (SDt) in ATP content was estimated both for cut sections and biopsies. Data were analysed by ANOVA using an hierarchical model to estimate the specific variance within (s̀wf) and between (s̀bf) fibres. ATP distribution was the same in cut sections and biopsy samples. The mean content of all fibres at rest was 20.14 mmol/kg dm. Values for se, sp, SDf and SDt were 0.49, 0.61, 1.61 and, 3.38 (cut sections) 4.28 (biopsies) mmol/kg dm, respectively; s̀wf was 1.53 mmol/kg and s̀bf 2.91 and 3.92 mmol/kg dm in cut sections and biopsy samples, respectively. ATP contents did not differ between fibre types. We conclude that most of the variance observed in measurements of single fibre ATP contents is due to variance between and within fibres rather than to the imprecision of the procedures used.
Capillaries of muscle in red cell hypervolaemic versus normovolaemic Standardbred horses
Authors: KARLSTRÖM KRISHNA , ESSÉN‐GUSTAVSSON BIRGITTA , PERSSON S. G. B.
Published: June 2010

Capillary supply in the gluteus medius of red cell hypervolaemic and normovolaemic horses was investigated. Muscle biopsies were taken from 2 groups of 4–9‐year‐old stallions: 10 normovolaemic (NV, CV/bwt=78.1 ml/kg) and 10 hypervolaemic (HV, CV/bwt=112.6 ml/kg). The muscle biopsies were analysed for fibre type composition, fibre areas, capillary supply and enzyme activities. There were no differences between groups for fibre type composition, fibre areas or enzyme activities. Hypervolaemic horses were found to have a significantly lower capillary density (HV: 587 ± 62; NV: 661 ± 57 cap mm−2), capillarisation in relation to mean fibre area (HV: 1.59 ± 0.19, NV: 1.77 ± 0.16 μnr2 10−3) and especially capillarisation of type I fibres (HV: 1.87 ± 0.24; NV: 2.15 ± 0.26 μm−2 10−3). The lower capillarisation of hypervolaemic horses could be one factor affecting their racing performance.
Isolating equine sarcoplasmic reticulum: its function during high intensity repeated sprints
Authors: WILSON J. A. , KRONFELD D. S. , GAY L. , WILSON T. M.
Published: June 2010

A method has been developed for isolating equine sarcoplasmic reticulum (SR) and measuring calcium uptake by modifying methods previously established in rat and rabbit muscle tissue. Excisional biopsies were used to obtain muscle samples from the gluteal muscles of 10 Quarter Horses. Sarcoplasmic reticulum vesicles were isolated through homogenisation and differential centrifugation. Calcium uptake into the vesicles was monitored spectrophotometrically using a calcium probe, antipyrylazo III. An enzyme linked optical assay was employed to assess Mg++ ‐stimulated, Ca++ ‐stimulated and total ATPase activity in the isolated SR vesicles. The present results provide a system for obtaining SR microsomes and measuring calcium uptake in the isolated vesicles in a relatively short period of time. High intensity sprinting decreased calcium uptake and Ca‐ATPase activity of SR vesicles in horses.
Frusemide
Authors: HINCHCLIFF K. W. , McKEEVER K. H.
Published: June 2010

Frusemide is administered to large numbers of North American racehorses because of its putative prophylactic effect on exercise induced pulmonary haemorrhage (EIPH). Two issues central to the use of frusemide in performance horses remain to be resolved: 1) Does frusemide reduce the incidence or severity of EIPH? and 2) does frusemide alter athletic performance or the capacity for muscular work, separate from any effect on EIPH? These issues are discussed, as is the reasoning that EIPH is, at least in part, a consequence of exertion induced high vascular transmural pressures and that reduction of these pressures by frusemide is the mechanism by which frusemide reduces the incidence or severity of EIPH. It is concluded that, on balance, it appears unlikely that frusemide reduces the incidence of EIPH, although it may reduce the severity of haemorrhage. The evidence that frusemide is ergogenic is evaluated and a potential mechanism for an effect of frusemide on athletic capacity, the frusemide induced reduction in body weight, is discussed.
Interrelationships between fluid, electrolyte and acid‐base balance during maximal exercise
Authors: CARLSON G. P.
Published: June 2010

Exercise at maximal intensity results in marked, but transient alterations in plasma electrolyte concentration and acid‐base balance. Compartmental fluid shifts contribute to the increased haematocrit, plasma protein and electrolyte concentrations. Elevations in plasma sodium and potassium concentrations relative to chloride tend to ameliorate the impact of lactate accumulation on anion‐cation balance. Lactate accumulation is associated with the development of a profound metabolic acidosis, but there are physiologically important differences between the mixed venous and arterial acid‐base values. Arterial blood is characterised by a moderate hypoxaemia, marked acidosis, modest increase in the partial pressure of carbon dioxide (PCO2) and a marked decrease in bicarbonate. Mixed venous blood pH is lower than arterial and is associated with a profound increase in PCO2 with a slight increase in bicarbonate. It is estimated that over 70% of the CO2 produced during maximal exercise is transported as bicarbonate in the venous circulation. This is largely a function of the carbonic anhydrase‐dependent chloride shift in which erythrocytes participate in CO2 transport from the tissues to the lungs. The chloride shift is responsible for the mixed venous‐arterial differences in plasma chloride concentration. The compartmental fluid shifts as well as the alterations in plasma electrolyte concentration and acid‐base balance are part of the integrated physiological response to the energy generating metabolic events associated with maximal exercise.
Respiratory adjustments in unacclimatised horses exercised under hot, humid conditions
Authors: ART TATIANA , LEKEUX P.
Published: June 2010

The purpose of this study was to investigate the effect of a hot and humid environment on the pattern of breathing and the gas exchange in heavily exercising horses. Five healthy fit Standardbred horses were investigated twice at 8 day intervals, once in temperate conditions (TC) (ambient temperature: 15°C; relative humidity: 55%) and once in hot and humid conditions (HHC) (ambient temperature: 30°C; relative humidity: 75%). The standardised treadmill exercise test consisted of 8 min warm‐up and 8 min exercise (1 min at 1.7, 4, 7, 8, 9 and 10 m/s and 2 min at 4 m/s with a 6% slope). Running in HHC induced a significant decrease in peak expired minute volume (V̇E), oxygen uptake (V̇O2), V̇CO2and oxygen pulse, while RQ remained unchanged and PACO2increased. The changes in skin temperature (ST), i.e. the difference between ST at rest and at 10 m/s, was dramatically higher in HHC. The test induced changes, i.e. the differences between the values before and after the test, in Cortisol, β‐endorphins and plasma lactate (LA) values after the test were significantly higher. This study showed that performing a strenuous exercise in hot, humid conditions in unacclimatised horses induced a reduction of the aerobic capacity, i.e. decrease of the V̇O2and increase of LA production. A relative hypoventilation could be partly responsible for this observation, but all the steps of the oxygen transport from the pulmonary ventilation to the muscle metabolism could also potentially be impaired in such conditions.
Ion and water losses from body fluids during a 163 km endurance ride
Authors: LINDINGER M. I. , ECKER GAYLE L.
Published: June 2010

This study calculated extracellular fluid (ECF) and intracellular fluid (ICF) water losses and ECF ion losses from 39 endurance trained horses during a 163 km ride. Jugular venous blood samples and body mass (BM) were obtained pre‐ride, at 32, 80 and 163 km of the ride and at 1 h of recovery. Blood was immediately analysed for haematocrit, plasma [Na+], [Cl−], [K+], ionised [Ca++] and total solids. ECF water losses were calculated from changes in plasma total solids assuming equilibrium between plasma and remaining ECF. ECF ion losses were calculated from changes in plasma ion concentrations and ECF volume (ECFV). Results were analysed with respect to speed (GroupA, 14.7 ± 1.0 km/h, n = 12;Group B, 11.2 ± 1.0 km/h, n = 11;Group C, did not finish, n = 16) and whether or not horses were pre‐loaded with electrolytes before the ride. The majority of ECF water losses occurred by 32 km: ECFV decreased by 5.4 ± 1.7 litres in A andBand by 7.8 ± 1.6 litres inC.At 80 km, there were no further losses inAandB, while inCECFV had decreased by 10.4 ± 1.9 litres. However, total body water and therefore ICFV, decreased progressively until the finish and were only partially restored after 1 h recovery. Most ECF ion losses also occurred within the first 32 km, with losses greater inC(P < 0.05) and β (P < 0.1) than in A (Na+5.9 ± 2.1%, K+24 ± 4%, Cl−8.4 ± 1.7%, Ca++13 ± 2%). Only at 32 km did the preloaded horses (n = 21) show reduced losses of Na+, K+and Cl−. In conclusion, the majority of ECF ion and water losses occurred early in the ride (by 32 km); net loss of TBW and ICFV continued until 80 km; better performing horses (A) were able to maintain ECF ion and water balance during the ride; and in most horses fluid and ion supplementation was effectively inadequate to replace all lost water and ions.
Arterial and mixed venous acid‐base status and strong ion difference during repeated sprints
Authors: TAYLOR LYNN E. , FERRANTE PAMELA L. , WILSON JUDITH A. , KRONFELD D. S.
Published: June 2010

Seven horses performed six, 1 min sprints separated by 4 min intervals at a walk, followed by a 30 min recovery period. To evaluate changes in blood gases and strong ions, blood samples were taken from the carotid artery (A) and the right heart (mixed venous, V) at rest, after a submaximal warm‐up, during the last 15 s of sprints 5 and 6 and at 5 and 30 min of recovery. At both arterial and venous sites, plasma [H+], PCO2, PO2, albumin ([Alb]), strong ion concentrations ([Na+], [K+], [Cl−]), blood lactate ([Lac]) and haemoglobin concentrations ([Hb]) were measured. Strong ion difference ([SID]), bicarbonate concentration ([HCO3−]) and total weak acid ([Atot]) were calculated. Between sites (A vs. V) there were differences in [H+], PCO2, PO2, [HCO3−], [Cl−], [SID], [Na+], [K+] and [Lac−]. Arterial PO2remained constant during exercise, was increased at 5 min recovery and returned to the resting level by 30 min recovery. The PvO2decreased during exercise before returning to resting levels at 5 min of recovery. During exercise, [Cl−] increased at A and decreased at V, which is consistent with the chloride shift. The [H+], PCO2and [HCO3−] decreased at A and increased at V. During exercise, [Na+], [K+] and [Lac] increased at both sites, with [Na+]V, [K+]Vand [Lac−]Aincreasing to a greater extent. Plasma [SID]Adecreased due to a greater increase in [Lac−]Acompared to other strong ions and [SID]Vincreased due to increased [Na+]Vand [K+]Vand decreased [Cl−]V. Plasma [Alb] and blood [Hb] increased with exercise, with no site differences. Plasma [H+] increased at V and decreased at A before returning to pre‐exercise values at 30 min recovery. These changes reflected the patterns of change in PCO2, but not [SID]. In turn, the decrease in PaCO2was probably associated with hyperventilation that maintained the PaO2at a constant level during repeated sprints. Results show that SID, [Atot] and PCO2have different effects on plasma [H+] and [HCO3−] at sites A and V and that the chloride shift is evident in the exercising horse.
Effect of a diet containing supplementary fat on the capacity for high intensity exercise
Authors: EATON M. D. , HODGSON D. R. , EVANS D. L. , BRYDEN W. L. , ROSE R. J.
Published: June 2010

This study investigated the effects of increased fat consumption on aerobic and anaerobic performance. Eight Thoroughbred horses that had undergone a 9 week, 6 days/week conditioning programme were randomly divided into 2 groups,Group F(5 horses) andGroup C(3 horses). For 2 weeks before the study all horses consumed a standard diet (2% fat) fed as 2 equal portions. Horses then undertook an incremental treadmill exercise test (+10% slope); 3 min at 4 m/s, 2 min at 6 m/s and 1 min at 8 m/s. Speed was then increased by 1 m/s every 60 s until fatigue. Maximal accumulated oxygen deficit (MAOD) was determined 72 h later. Horses inGroup Fwere then fed a diet containing 12% of the digestible energy in the form of fat (390 ml corn oil), a diet that was isocaloric with the control diet. Horses inGroup Ccontinued to receive the standard diet. All horses continued training (3600 m/day, at speeds up to 10 m/s, 6 days/week). After 4 weeks, the exercise tests were repeated. Prior to fat supplementation, V̄O2maxwas mean ± s.e. 145 ± 5.3 and 148.0 ± 6.0 ml/kg/min, time to fatigue during the MAOD test was mean ± s.e. 84.2 ± 18.4 and 85.0 ± 14.8 s, mean ± s.e. peak plasma [lactate] was 24.8 ± 3.1 and 23.5 ± 1.7 5 mmol/l and MAOD was 56.5 ± 5.3 and 68.1 ± 4.7 mlO2eq/kg forGroups FandCrespectively. The V̄O2maxand run time to fatigue in the incremental exercise test did not change in either group following fat supplementation. Run time (mean ± s.e. 97.2 ± 17.8 s), MAOD (65.5 ± 6.2 mlO2eq/kg) and peak plasma [lactate] (29.5 ± 2.6 mmol/l) increased during the MAOD test inGroup Fbut remained unchanged inGroup C.Resting muscle [glycogen] depletion during the MAOD test was not altered by the dietary manipulation. Provision of an increased proportion of the diet in the form of fat increased high intensity exercise capacity and the MAOD during intense treadmill exercise.
Effect of grain type and vitamin supplementation on performance of exercising horses
Authors: McMENIMAN N. P. , THORNTON J. R. , DOWSETT K. F.
Published: June 2010

Effects of multivitamin supplementation and type of grain on exercise capability and behaviour was determined in 2 groups of 4 Australian stockhorses. Initially the horses were fed diets containing chopped oaten and lucerne hay and either rolled oats grain or cracked maize. The grains were fed on an isoenergetic basis and contributed 60% of the digestible energy content of the diets. After an 8 week training programme the horses were subjected to 2 standard exercise tests (SET) 2 weeks apart. Each SET was followed, 3 days later, by a run to exhaustion (RTE) at a speed equivalent to 110% of the VO2maxrecorded during the previous SET. Both diets were then fortified with a complete vitamin mix (except for ascorbic acid and choline) that: supplied vitamins at a level that equalled or exceeded NRC (1989) recommendations. After 2 weeks of supplementation the SETs and RTEs were repeated. Neither grain type nor vitamin supplementation had any significant effect on liveweight, VO2max, VLA4or total run time to exhaustion. Vitamin supplementation reduced maximum heart rate (mean ± s.e. 227.8 vs. 233.2 ± 1.86 beats/min) and maximum plasma lactate concentrations (11.1 vs. 14.2 ± 0.67 mmol/l) during the SETS. Grain type had no effect on any of the horses' behavioural characteristics. Under the conditions of our experiment neither grain type nor vitamin supplementation affected the performance capability of the horses.
Blood gas, plasma lactate and bronchoalveolar lavage cytology analyses in racehorses with respiratory disease
Authors: COUËTIL L. L. , DENICOLA D. B.
Published: June 2010

The purpose of this study was to evaluate the relationship between bronchoalveolar lavage (BAL) cytology, arterial blood gases and plasma lactate concentration during a standardised treadmill test (STT) in racehorses with small‐airway inflammation (SAI), or exercise‐induced pulmonary haemorrhage (EIPH).

Sixteen Thoroughbred and 20 Standardbred actively racing racehorses, were divided into a control group (n=10), EIPH group (n=13) and SAI group (n = 13). Each STT consisted of a 2 min trot at 4 m/s followed by 5 × 1 min, incremental speed steps (6, 8, 10, 11 and 12 m/s) at 10% incline for Thoroughbred and 5% for Standardbred horses, followed by a 15 min recovery period. Blood was collected via a transverse facial artery catheter at the end of each step.

Total nucleated cell count of bronchoalveolar lavage fluid (BALF) collected from horses with EIPH was significantly higher than controls. Neutrophil count and percentage in BALF collected pre‐STT from horses with SAI were significantly higher than controls. Horses with EIPH or SAI exhibited a more severe exercise‐induced arterial hypoxaemia than control horses during the first 4 steps of the STT (P<.001). Poorly performing horses were more severely hypercapnic than control horses during the STT recovery period (P<.05). Five and 15 min post exercise, horses with SAI and EIPH had higher blood lactate and lower blood bicarbonate concentrations than control horses (P<.05).

The results of this study suggest that lung ventilation‐perfusion mismatch may be more severe in horses with respiratory disease. BALF of horses with SAI and EIPH was characterised by neutrophilic and lymphocytic inflammation, respectively. Very few parameters were significantly different between groups of good and poor performers.
Effects of frusemide on pulmonary capillary pressure in horses exercising on a treadmill
Authors: GLEED R. D. , DUCHARME N. G. , HACKETT R. P. , HAKIM T. S. , ERB H. N. , MITCHELL L M. , SODERHOLM L V.
Published: June 2010

We hypothesised that frusemide would decrease pulmonary capillary pressure in horses during strenuous exercise. Seven horses were tested after receiving saline or frusemide (2 mg/kg bwt) in random order with an interval of at least one week. Measurements were made with the horses standing, exercising at 75, 90 and 100% HRmax(maximal heart rate), and then walking 2 min after cessation of 100% HRmax. The exercise tests lasted for ˜3 min with an interval of walking between them. Pulmonary artery and oesophageal pressures were recorded continuously and subsequent analysis of the pulmonary artery pressure signal was carried out after subtraction of the oesophageal pressure signal. Pulmonary arterial pressure, pulmonary capillary pressure, pulmonary artery wedge pressure, breathing rate, heart rate and arterial blood gas tensions were recorded at each level of exercise. Pulmonary arterial wedge and pulmonary capillary pressures were determined from the pulmonary arterial waveform after dynamic occlusion of a branch of the pulmonary artery. The resulting decay in pressure was submitted to exponential curve fitting and the amplitude on this curve at the moment of occlusion was recorded as pulmonary capillary pressure. When adjusted for horse and exercise intensity, horses receiving frusemide had lower pulmonary capillary and wedge pressures (adjusted least‐squares means=36 mmHg and 28 mmHg, respectively) when compared with control values (adjusted least‐squares means=41 mmHg (P=0.042) and 35 mmHg (P = 0.002), respectively). Pulmonary arterial pressure, breathing rate, heart rate and arterial blood gas tensions did not differ between treatments at any exercise intensity.

We conclude that frusemide reduces pulmonary capillary and wedge pressures. This is compatible with reduced transcapillary filtration and, therefore, reduced accumulation of lung water at exercise. It may also account for the putative protective effect of frusemide against exercise‐induced pulmonary haemorrhage.
Sequential changes in bronchoalveolar cytology after autologous blood inoculation
Authors: McKANE S. A. , SLOCOMBE R. F.
Published: June 2010

Six horses, free of recent exercise‐induced pulmonary haemorrhage (EIPH), each had 8 bronchial segments inoculated with 40 ml of autologous blood lavaged on Days 3, 5, 7, 10, 14 and 21 after inoculation. The bronchoalveolar lavage (BAL) fluid samples were analysed, and total leucocyte counts and differential cell percentages determined. Statistical analysis of the differences between the 8 post inoculation and 1 pre‐inoculation (control) lavage sites demonstrated an early neutrophilic response, rising from <5% of alveolar leucocytes to 10% by 24–48 h post inoculation. As this response waned, macrophage numbers increased and persisted at mildly elevated levels for the remainder of the experiment. Small numbers of erythrophagocytes were observed prior to 3 days post inoculation, but their numbers increased 10‐fold by Day 10. In the first 3 days, blood was observed endoscopically streaming from inoculated lung regions, suggesting that mucociliary clearance is a major mechanism of early erythrocyte clearance. However, both free and phagocytosed whole erythrocytes were recovered in lavages 14 days after inoculation with small numbers of erythrocytes still present at 21 days. We conclude that intrapulmonary blood provokes a mild, but prolonged inflammatory reaction and that the removal of alveolar haemorrhage is dependent on a combination of mucociliary clearance and phagocytic mechanisms. Erythrophagocytosis is slow to commence and the removal of blood prolonged, suggesting that horses in fast work, sufficient to induce EIPH, are unlikely to recover fully if intervals between strenuous work are less than 14 days.
Relationship between running speed, isoenzymes of serum creatine kinase and lactate dehydrogenase and left ventricular function in stallions
Authors: RUECA F. , CONTI M. B. , PORCIELLO F. , SPATERNA A. , ANTOGNONI M. T. , MANGILI V. , FRUGANTI G. , AVELLINI G.
Published: June 2010

The purpose of this study was to assess the possible relationship between maximal running speed, serum isoenzyme patterns of creatine kinase (CK) and lactate dehydrogenase (LDH) and echocardiographic indices of left ventricular function. A group of 15 healthy, 3‐year‐old Maremmano stallions were given a 100 day training programme. At the end of this the animals carried out a maximum speed test and were divided into 2 groups (A and B) according to whether or not they had attained a speed of 15 m/s. Venous blood samples were taken from each horse before exercise (T0), 2 min (T1) and 24 h (T2) after exercise. Total serum activity of CK and LDH was measured and their isoenzyme distribution pattern determined. The day before the speed test echocardiographic examination was carried out at rest to assess the left ventricular function by calculating telediastolic, telesystolic and stroke volume, ejection fraction and stroke index. Statistically significant differences were found for the CK isoenzyme pattern at T2, where Group A showed an increase in the MM fraction (P=0.003) and a decrease in the MB fraction (P = 0.014). These changes were thought to be linked to an increased membrane leakage due to exercise and not to muscle fibre disruption because the CK and LDH total activities remained within the normal range. In Group A there was also greater left ventricular telediastolic volume (P=0.044) and length (P=0.033) at rest as well as a greater stroke index (P = 0.032). We concluded that the evaluation of CK pattern after exercise and of echocardiographic left ventricular function indices at rest made it possible to select for the fastest horses (Group A).
Cardiac responses to training in 2‐year‐old Thoroughbreds: an echocardiographic study
Authors: YOUNG LESLEY E.
Published: June 2010

Guided M‐mode echocardiography was performed in seven 2‐year‐old Thoroughbreds before commencement of commercial flat‐race training, and 18 weeks later, when all horses were either racing regularly (5 horses), or at racing fitness (2 horses). M‐mode echocardiography was performed using a 2.5 MHz annular phased array ultrasound transducer and a Vingmed 800 Supervision echocardiograph. Images were obtained from the right hemithorax; a short axis view of the left ventricle (LV) at the level of the chordae tendinae was used to position the M‐mode cursor. The following variables were measured: left ventricular (LV) internal diameter in diastole (LVIDd) and systole (LVIDs) and interventricular septal (IVS) and left ventricular free wall thickness (LVFW) in systole and diastole. The following variables were also calculated: LV fractional shortening (%FS), LV ejection fraction (EF), LV relative and mean wall thickness and muscle mass. Values before and after training were compared using a paired Student's t test.

Training resulted in significant reductions in %FS and EF. Left ventricular internal diameter increased from 11.38 (s.d=0.58) cm before training to 12.16 (s.d. = 0.7) cm after training (P<.001). Calculated left ventricular mass also increased significantly (mean increase of 33% P<.001). Bodyweight was unchanged in the present study. Relative wall thickness was significantly increased in all horses, suggesting that eccentric cardiac hypertrophy occurs in response to commercial flat‐race training. The mean post training value for relative wall thickness of 0.45 (s.d.=0.05) for the horses in the present study is similar to that of human athletes in power/endurance disciplines.
Sedation and antisedation as tools in equine lameness examination
Authors: BUCHNER H. H. F. , KüBBER P. , ZOHMANN E. , PEHAM CH.
Published: June 2010

A kinematic study was performed to establish the locomotion pattern of horses under detomidine sedation and the effects of antagonisation for possible use during lameness examinations in uncooperative horses. The kinematics of 17 Warmblood horses (9 sound, 8 lame with chronic forelimb lameness) were recorded on 2 days using a high‐speed video system while trotting (3.9 m/s) on a treadmill. On each day a control measurement was carried out prior to sedation with detomidine (10 μg/kg bwt) and repeated recordings at 15, 25, 35, 45 and 60 min after sedation. On the second day, sedation was antagonised using atipamezole (100 μg/kg bwt) after the 15 min recording.

Head height and pulse rate documented the level of sedation. The head dropped from mean 1.23 m (s.d. 0.13) to 0.50 m (0.26) following sedation to reach again 1.06 m (0.19) after 60 min. Antagonisation reversed the height significantly at the 25 min recording to 1.06 m (0.11). Walking and trotting were possible in all sedated horses in response to voice commands only. Forelimb lameness symmetry parameter (Head Acceleration Asymmetry: HAAS) in 8 lame horses did not change significantly due to sedation. Stride length increased significantly from mean 2.53 m (0.18) to 2.66 m (0.20) 15 min after sedation and reversed to 2.56 (0.17) m after antagonisation. Stride and stance durations changed accordingly. In conclusion, sedation did not change the degree of lameness, but did alter the general locomotion pattern. Antagonisation diminished most of these effects, but small differences to the unsedated pattern remained.
The kinematics of loading and fatigue in the Standardbred trotter
Authors: JOHNSTON C. , GOTTLIEB‐VEDI MARIANNE , DREVEMO S. , ROEPSTORFF L.
Published: June 2010

The Standardbred trotter must pull a considerable load when racing and, consequently, draught loading is a common method of training in the Standardbred and the effects of loading and fatigue due to loading on the locomotor pattern was the purpose of this investigation. Four mature healthy Standardbred horses trotted with and without a horizontal‐pulling loading of 34 kg until the horses were no longer willing to keep pace with the treadmill despite encouragement. Heart rate was monitored every min using a bipolar electrocardiogram. The kinematics for 5 consecutive strides were filmed. Horses exercised on the treadmill for 7–10 mins. The mean heart rate was 206 beats/min at the end of the exercise. Due to draught loading, the horses reduced significantly the time of the stance phase in both the fore‐ and hindlimb. Three of the 4 horses reduced their stride lengths as the result of increased loading. The general movement pattern of the horses remained similar. More dramatic changes in the movement pattern were observed because of fatigue. The limbs of the horse were significantly more compressed as the result of greater joint excursion during the stance phase. Furthermore, the length of stride was significantly increased as the result of fatigue. The results show that both loading and fatigue change the locomotor pattern of the Standardbred trotter. Although the horizontal loading was. considerable, the horse maintained similar joint movement with increases in stride frequency. During fatigue the horse seems to be unable to maintain stride frequency, probably due to a compromised power capacity of the muscles. The increase in joint excursion due to fatigue may have an important influence on certain types of injury to the locomotor system of the racehorse.
Muscular and metabolic responses to moderate‐intensity short‐term training
Authors: GEOF R. J. , McCUTCHEON L JILL , SHEN HUA
Published: June 2010

The objectives of this study were to determine the effects of 10 consecutive days of moderate‐intensity training on 1) the muscular metabolic response to exercise at 100% of the pre‐training maximum rate of oxygen consumption (V̇o2max); and 2) mitochondrial enzyme markers (citrate synthase, CS; succinate dehydrogenase, SDH; 3‐hydroxy‐acyl‐CoA dehydrogenase, HAD) of oxidative capacity in middle gluteal muscle. Six mature, unfit Thoroughbred horses completed both incremental (for determination of V̇o2max) and high‐intensity exercise protocols before (HI1) and after (HI2) training. Training consisted of 10 consecutive days of running at 55% V̇o2maxfor 60 min per day (13–14 km/day). For the HI, horses completed a 10 min warm‐up, followed by exercise at 100% of pre‐training V̇o2max(mean speed 9.8 m/s) until fatigue. Training resulted in an 8.9% increase in V̇o2max(Pre: 142 ± 4 ml/kg bwt/min; Post: 155 ± 4 ml/kg bwt/min) and a 24% increase in run time to fatigue during HI. Whereas V̇o2during HI was not altered by training, peak values for V̇co2and R were significantly lower following training. Compared to HI1, there was a 45% reduction in the net rate of muscle glycogenosis during HI2. Peak (end exercise) values for plasma and muscle lactate concentrations decreased by 22 and 23%, respectively, after training. Training also attenuated the exercise‐associated increase in plasma norepinephrine, but there was no effect on plasma epinephrine concentrations. Maximal activities of CS, SDH, and HAD were unaltered by training. We conclude that 10 days of moderate‐intensity exercise results in decreases in muscle glycogenosis and anaerobic metabolism during high‐intensity exercise at the same absolute workload. Furthermore, development of measurable increases in mitochondrial oxidative potential may not be required for expression of these metabolic adaptations in early training.
Partition of plasma hydrogen ion concentration changes during repeated sprints
Authors: KRONFELD D. S. , FERRANTE P. L. , TAYLOR LYN E. , TIEGS W.
Published: June 2010

Increases in blood [H+] and lactic acid [La−] attend fatigue. We applied Stewart's physiological model of acid‐base status and simple regressions to assess the importance of independent variables and [La−] on [H+] during repeated sprints. Eight well‐conditioned Arabians performed 9 sprints. Plasma from jugular vein samples was analysed for pH, Pco2, Na+, K+and Cl−. Plasma [La−] was calculated from blood [La−], plasma [H+] from pH, SID from Na+, K+, Cl−and La−, Atotfrom pH, Pco2and SID.

Peaks for SID, Pco2and [H+] were reached at sprint 1, ‐2 and ‐3, respectively. At sprint 3, the 5.7 nmol/l peak in [H+] was partitioned into 2.3, 2.7 and 0.7 nmol/l for Atot, Pco2and SID, respectively. From sprint 3 to sprint 9, increases in Atotand decreases in SID tended to increase [H+] but were counteracted by a steady decrease in Pco2that determined the progressive decrease in [H+]. Therefore Pco2was the dominant determinant of [H+] during 9 repeated sprints, and the expected major effect of [La−] was moderated in the SID by opposing increases in [Na+] and [K+]. In the work‐adapted phase (sprints 3–9), decreasing [H+] was correlated positively with Pco2(r = 0.997, P<.001) but negatively with La−(r = ‐0.986, P<.001). Respiration was therefore completely compensating for the effects of metabolism on [H+]. During the transition from rest to sprint 3 (peak plasma [H+]), increasing [H+] was highly correlated (r=0.99, P = 0.011) with [La−] but no other variable. The empirical and physiological analyses were consistent with one another during the work‐adapted phase, but emphasis was placed on [La−] by the regression analysis, in contrast to Pco2by the Stewart analysis, during the rest‐work transition.