bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasma aldosterone concentration and renal sodium excretion are altered during the first days of training
Authors: MCKEEVER K. H. , SCALI R. , GEISER S. , KEARNS C. F. 
Published: June 2010

SummaryThe purpose of the present study was to determine whether the training‐induced hypervolemic response seen in the horse is associated with aldosterone‐mediated renal mechanisms affecting sodium conservation during the first days of training. Five healthy, Standardbred mares (weight 450–500 kg, age 4–8 years) that were unfit, but accustomed to running on the treadmill, were used to test the hypothesis that repeated submaximal exercise would alter plasma aldosterone (ALDO) concentration and renal excretion of electrolytes in horses within the first 3 days of training. The experiment consisted of a 2 week housing equilibration period followed by a 1 week control period and a 3 day exercise training period (30 min/day at 60% V̇O2max). During control, ALDO and renal fluid and electrolyte losses were measured for 24 h on 3 separate days. Renal function (urine volume [UV], 24 h excretion of Na+, K+and CI‐ [UNA+V, UK+V, UClV], clearance of Na+[CNa+], K+[CK+] and Cl−[CCl‐], creatinine [CCr], osmotic substances [Cosm], and solute‐free water [FWC], and the fractional excretion of Na+, K+and Cl−) and ALDO were measured for an additional 3 consecutive days during the training period. There were no differences (P>0.05) in any variable during the control period. Plasma volume increased (+18.7%, P<0.05) after 3 days of training. During training, there were no significant changes in plasma osmolality, electrolyte concentrations or CCr. Training caused decreases (P<0.05) in UV (‐30%), UNA+V (‐73%), UK+V, (‐55%) and UCl‐V (‐70%). Training also caused decreases (P<0.05) in Cosm(‐30%), through decreases in CNa+(‐60%), CK+(‐60%), and CCl‐(‐66%). Interestingly, FWC increased (+30%, P<0.05), whereas, there were significant decreases in the fractional excretion of Na+(‐59%), K+(‐48%) and Cl−(‐60%). Training caused substantial elevations in both pre‐exercise (967%, P<0.05) and postexercise (+3013%, P<0.05) plasma ALDO concentrations suggesting an increase in both basal levels and the responsiveness to acute exercise. Together, these observations suggest that mechanisms affecting tubular conservation of electrolytes contribute to the early response to training. However, it is also concluded that renal mechanisms appear to be only part of the mechanism for conserving sodium and water intake as well as training‐induced changes in gastrointestinal mechanisms affecting electrolyte and water balance.
Metabolic and osmoregulatory function at low and high (3800 m) altitude
Authors: GREENE H. M. , COGGER E. A. , MILTENBERGER T. L. , KOCH A. K. , BRAY R. E. , WICKLER S. J. 
Published: June 2010

SummaryAltitude evokes physiological adjustments that include not only respiratory and cardiovascular properties, but also metabolic function, renal and endocrine responses. The purpose of the present study was designed to expand our understanding of the physiological process involved with acclimatisation to high altitude in equids. The study examined temporal effects on metabolic and osmoregulatory function in horses (n = 6) at rest and postexercise at 3800 m. Animals were studied at 225 m (Pb = 743 mmHg) and during a 10 day stay at altitude (Pb = 487 mmHg). Rest samples were taken 90 min postprandial at 0830 h and immediately after the gallop phase of a standard exercise test. Changes in glucose, insulin, cortisol, thyroxine, sodium, potassium, chloride and total protein were assessed at both altitudes. Exercise stimulated increases in cortisol, thyroxine, potassium, and chloride; while the concentrations of glucose, insulin, sodium and total protein (regardless of altitude) decreased. Acute (Day 2) altitude exposure (following transport stress) produced significant increases in glucose, cortisol, thyroxine, chloride and protein at rest and exercise. All variables (except cortisol) appeared to stabilise by Day 4 of altitude exposure.Observations from these data (coupled with haematological and blood gases data) indicate that equids acutely acclimate within 2–3 days to this altitude.
Evaluation of the i‐STAT hand‐held chemical analyser during treadmill and endurance exercise
Authors: SILVERMAN S. C. , BIRKS E. K. 
Published: June 2010

SummaryThis study examined the accuracy and precision of a ***hand‐held, chemical analyser, i‐STAT, in measuring selected blood constituents which may be of use in the diagnosis and management of metabolic disorders found in exercising horses. Venous blood samples were taken from 3 Thoroughbred geldings, fit and trained to exercise on a treadmill, both before and after exercise at a speed sufficient to elicit V̇O2max. The samples were analysed both with the i‐STAT and with in‐house analysers to compare the values of pH, partial pressure of oxygen (PO2), partial pressure of carbon dioxide (PCO2), bicarbonate (HCO3), lactate and base excess (BE). The i‐STAT demonstrated acceptable accuracy and precision for determination of pH, PO2and PCO2, and lactate. We concluded that these parameters could be reliably evaluated by the i‐STAT.The i‐STAT was further evaluated at veterinary checkpoints during a 60 and 100 mile endurance ride. Because a built‐in thermostat prevents function when the temperature of the analyser is outside the optimum range (16–30°C), it was necessary to insulate the i‐STAT from extreme ambient temperatures. As this portion of the study was conducted in warm temperatures, the appropriate insulation was to maintain the i‐STAT in an ice‐cooled container except during actual blood analyses. Further investigation into the feasibility of using hand‐held chemical analysers at the veterinary checkpoints during endurance rides is recommended.
Carbonic anhydrase activity and sweat gland morphology in trained and untrained Standardbred trotters
Authors: LARSDOTTER S. , HOLM L. , DAHLBORN K. , JANSSON A. , JOSEFSSON M. , RIDDERSTRÅLE Y. 
Published: June 2010

SummarySweat gland morphology and carbonic anhydrase (CA) distribution was studied after exercise in trained and untrained horses using a histochemical technique and light microscopic image analysis. Three trained and 3 untrained Standardbred trotters performed an exercise test (20 min trot at 6 m/s with 5 min walk at 1.8 m/s in the beginning and end) on a high‐speed treadmill at 35°C. Skin biopsies were taken before exercise and after trot. The fluid loss after exercise was 10, 12 and 12 g/kg bwt in the untrained horses and 4, 6 and 11 g/kg in the trained. Trained horses had a larger cell area than untrained after exercise, which might be related to an increase in secretory capacity. The area of the cell occupied by CA was independent of training status, but increased with exercise in both groups. The CA activity was higher in untrained animals and increased after exercise in both groups. The change in CA during exercise might be a response to an increasing demand for HCO3‐ secretion during sweat formation. Therefore, the sweat gland undergoes morphological changes due to stimuli such as heat, exercise and training, but species differences are evident. To our knowledge, no one has previously studied the influence of training on the morphology of the equine sweat gland.
Age‐related changes and inheritance of lactate transport activity in red blood cells
Authors: VÄIHKÖNEN L. K. , OJALA M. , PÖSÖ A.R. 
Published: June 2010

SummaryIn red blood cell membranes, the activity of the main lactate carrier, H+‐monocarboxylate co‐transporter (MCT), varies interindividually and its distribution is bimodal. To show the repeatability of MCT activity, 2 to 5 blood samples were taken, at an interval of approximately 1 year, from 51 Standardbred horses, age 2 weeks‐8 years, for a total of 128 observations. The horses could be divided into low (LT) and high (HT) lactate transport activity groups. Age significantly affected (P<0.05) MCT activity such that activity was highest in foals, reached a nadir at 2–3 years, and tended to increase again thereafter. Interindividual variation was not sufficiently high to allow a horse to switch from the LT‐group to the HT‐group, orvice versa.When MCT activity from 4 sires, 15 dams and their 52 offspring was analysed, the data showed that MCT activity is heritable and supported the hypothesis that low MCT activity was caused by a recessive allele in a single autosomal locus. Because MCT activity affects RBC lactate concentrations, the phenomenon may be physiologically significant.
Effects of oral electrolyte supplementation on endurance horses competing in 80 km rides
Authors: SAMPIERI F. , SCHOTT H. C. , HINCHCLIFF K. W. , GEOR R. J. , JOSE‐CUNILLERAS E. 
Published: June 2010

SummaryReasons for performing study:There is no evidence that use of oral electrolyte pastes enhances performance in competing endurance horses.Objective:To ascertain whether oral administration of a high dose (HD) of sodium chloride (NaCl) and potassium chloride (KCl) to endurance horses would differentially increase water intake, attenuate bodyweight (bwt) loss and improve performance when compared to a low dose (LD).Methods:A randomised, blinded, crossover study was conducted on 8 horses participating in two 80 km rides (same course, 28 days apart). Thirty minutes before and at 40 km of the first ride 4, horses received orally 0.2 g NaCl/kg bwt and 0.07 g KCl/kg bwt. The other 4 received 0.07 g NaCl/kg bwt and 0.02 g KCl/kg bwt. Horses received the alternate treatment in the second ride. Data were analysed with 2‐way ANOVA for repeated measures (P<0.05).Results:Estimated water intake was significantly greater with HD both at the 40 km mark and as total water intake; however, differences in bwt loss and speed between HD and LD were not found. Treatment significantly affected serum Na+, Cl−, HCO3, pH and water intake, but not serum K+or bwt. Serum Na+and Cl−were significantly higher at 80 km when horses received HD, but no differences were found in early recovery. Venous HCO3and pH were significantly lower throughout the ride and in early recovery when horses received HD.Conclusions and potential relevance:Other than enhancing water intake, supplementing endurance horses with high doses of NaCl and KCl did not provide any detectable competitive advantage in 80 km rides. Further, the elevated serum electrolyte concentrations induced with HD might not be appropriate for endurance horses.
Endurance exercise is associated with increased plasma cardiac troponin I in horses
Authors: HOLBROOK T. C. , BIRKS E. K. , SLEEPER M. M. , DURANDO M. 
Published: June 2010

SummaryReason for performing study: Information is lacking regarding the influence of long distance exercise on the systemic concentration of cardiac troponin I (cTnl) in horses.Objectives: To determine if the concentration of cTnl in horses competing in 80 and 160 km endurance races increases with exercise duration and if cTnl concentrations can be correlated with performance data.Methods: Blood samples for the measurement of cTnl and 3 min electrocardiogram recordings were obtained from horses prior to, during and after completion of 80 and 160 km endurance races at 3 ride sites during the 2004 and 2005 American Endurance Ride Conference competition seasons.Results: Full data sets were obtained from 100 of the 118 horses. Endurance exercise was associated with a significant increase in cTnl over baseline in both distance groups. Failure to finish competition (poor performance) was also associated with an increased cTnl concentration over baseline at the time of elimination when data from both distances were combined. Other than one horse that developed paroxysmal atrial fibrillation, no arrhythmias were noted on the 3 minute ECG recordings that were obtained after endurance exercise in either distance group.Conclusions: Systemic concentrations of cTnl increase in endurance horses competing in both 80 and 160 km distances. Although final cTnl concentrations were significantly increased over their baseline values in horses that failed to finish competition, the degree of increase was not greater than the increase over baseline seen in the horses that successfully completed competition. The clinical significance of increased cTnl in exercising horses could not be ascertained from the results of this study.Potential relevance: These data indicate that cardiac stress may occur in horses associated with endurance exercise. Future studies utilising echocardiograpy to assess cardiac function in horses with increased cTnl are warranted.
Thyroid hormone responses to endurance exercise
Authors: GRAVES E. A. , II H. C. SCHOTT , MARTENIUK J. V. , REFSAL K. R. , NACHREINER R. F. 
Published: June 2010

SummaryReasons for performing study:Limited information exists about changes in circulating thyroid hormone concentrations during prolonged endurance exercise in horses.Objective:To examine the effects of prolonged exercise on serum iodothyronine concentrations in horses performing endurance exercise of varying distances.Methods:Serum concentrations of iodothyronines were measured in horses before and after completion of 40, 56, 80 and 160 km endurance rides (Study 1); daily during a 5 day, 424 km endurance ride (Study 2); and before and for 72 h after completion of a treadmill exercise test simulating a 60 km endurance ride (Study 3).Results:In Study 1, 40 and 56 km of endurance exercise had little effect on serum iodothyronine concentrations with the exception of a 10% decrease (P<0.05) in free thyroxine (FT4) concentration after the 56 km ride. In contrast, total thyroxine (T4), total triiodothyronine (T3), FT4and free triiodothyronine (FT3) concentrations all decreased (P<0.05) after successful completion of 80 and 160 km rides, with decreases ranging from 13–31% and 47–54% for distances of 80 and 160 km, respectively. Further, pre‐ride T4concentration was lower (P<0.05) and FT3concentration was higher (P<0.05) in horses competing 160 km as compared to horses competing over shorter distances. In Study 2, serum concentrations of T4, T3and reverse triiodothyronine (rT3) progressively decreased (P<0.05) over the course of the multi‐day ride. In Study 3, the greatest decrease (P<0.05) in all iodothyronines was observed at 12 h of recovery, ranging from 25% for FT4to 53% for FT3, but all thyroid hormone concentrations had returned to the pre‐exercise values by 24 h of recovery.Conclusion:Endurance exercise results in transient decreases in serum iodothyronine concentrations.Potential relevance:These data are important to consider when thyroid gland function is assessed by measurement of serum iodothyronine concentrations in endurance horses.
Gene expression profiling in blood cells of endurance horses completing competition or disqualified due to metabolic disorder
Authors: BARREY E. , MUCHER E. , ROBERT C. , AMIOT F. , GIDROL X. 
Published: June 2010

SummaryReasons for performing study:Genomics using cDNA microarrays could provide useful information about physiological adaptations and metabolic disorders in endurance horses.Objectives:In order to show that genes are modulated in leucocytes in relationship with performance and clinical status of the horses, gene expression in leucocytes, haematological and biochemical parameters were compared between successful and disqualified endurance horses.Methods:Blood samples were collected at rest (T0) and just after a 140–160 km endurance race (T1) in 2 groups of horses: 10 continuing successful (S) and 10 disqualified horses stopped at a vet‐gate for metabolic disorders (D). Total RNA was extracted from the blood cells (leucocytes), checked for purity, amplified and hybridised using mouse cDNA microarrays including 15,264 unique genes. Differential gene expressions were studied by hybridisation of each sample T1 vs. a control sample collected at T0 (pool of 20 sound horses).Results:Some significant differences were observed in the haematology and biochemistry of the 2 groups (Svs.D). InGroup D, rhadomyolysis was confirmed with CK 13,124 u/***l and AST 1242 u/***l. The list of 726 (including 603 annotated genes) significant genes was filtered according to a high P‐value cut‐off (P<0.00001). Among them, 130 were up‐regulated (expression ratio>1.5) and 288 were down‐regulated (<1/1.5). Analysis of variance revealed 62 genes differentially expressed (P<0.05) inGroups DandS.The expression levels of 28 and 50 genes were significantly correlated (r>0.75) with CK and AST level inGroup D, respectively. The gene ontology classification showed that more genes were up‐regulated inSthan in theD.More genes were down‐regulated in the disqualified horses.Conclusions:Long exercise induced many significant gene modulations in leucocytes. Some genes were expressed in relationship with the clinical phenotype observed inGroup D:rhabdomyolysis and haemolysis.Potential relevance:Some of these genes could be candidates to explain poor performance or pathologies. Further association studies with a greater number of genes should be conducted.
Trot asymmetry in relation to physical performance and metabolism in equine endurance rides
Authors: MUÑOZ A. , CUESTA I. , RIBER C. , GATA J. , TRIGO P. , CASTEJÓN F. M. 
Published: June 2010

SummaryReason for performing study:Trot is a symmetric gait and asymmetry might appear or increase during endurance rides due to lameness, pain or excessive fatigue.Hypothesis:To assess whether trot asymmetry increases during endurance competitions, whether it is possible to discriminate between horses with different performance and also its possible relationship with metabolism.Methods:Fifty‐eight horses were filmed at trot during the lameness examinations in the vet‐gates, before the competition (BCO), and afterphases I(at 29 km),2(at 59 km) and3(at the end of the ride, at 80 km) and stride duration (SD) measured in all 4 limbs. A locomotion symmetry index (LSI) was calculated by comparing SD in the diagonal pairs of limbs. In all the cases, the longer diagonal pair SD was compared to the shorter. Horses were classified as symmetric (SyH) when LSI was lower than mean + 2s.d. and asymmetric (ASyH) when LSI was higher than mean + 2s.d. of the data obtained in BCO. Venous samples were withdrawn in the vet‐gates and PCV, WBC, creatinine, TPP, uric acid, CK, AST, LDH, Na, K and Cl were measured. Horses were divided into different performance groups: successful (SH), lame (LH) and metabolic (MH), and according to ride velocity, the SH group was also divided into faster finishers (FF) and slower finishers (SF).Results:The percentages of SyH were high (>80%) and very similar between the different performance groups. LSI became more asymmetrical in the vet‐gates, especially in the LH and MH groups. LSI presented negative correlations with the velocities during the rides and in the vet‐gates and CK. The ASyH had higher velocities during the rides and plasma CK and lower velocities during the vet‐gates and plasma uric acid concentrations.Conclusions:Although trot asymmetry increases during endurance events, LSI calculated comparing SD in the two diagonal pair of limbs did not allow the differentiation of horses with different performance.
Stride parameters and hindlimb length in horses fatigued on a treadmill and at an endurance ride
Authors: WICKLER S. J. , GREENE H. M. , EGAN K. , ASTUDILLO A. , DUTTO D. J. , HOYT D. F. 
Published: June 2010

SummaryReason for performing study:The relationship between fatigue and stride and/or muscle stiffness requires further study.Objective:To measure stride parameters in horses undergoing fatigue associated with running at submaximal speeds both on a treadmill and in an endurance ride.Hypothesis:Stride frequencies and estimates of hindlimb stiffness would be decreased in fatigued horses.Methods:Horses were fatigued using 2 paradigms: run to exhaustion at a treadmill (4.5 m/sec, 6% incline) and finishing an 80 km endurance ride. Videos were digitised before and after fatigue and analysed for stride parameters: hind limb length, stride frequency, time of contact, step length, duty factor and stride length.Results:In fatigued horses, stride durations were 5% longer (P=0.007) resulting in lower stride frequencies (P=0.016) and longer stride lengths (P = 0.006). The time of contacts (tc) for stance phase were not different (P = 0.108) nor was duty factor (tc/stride period, P = 0.457). Step length (speed x tc) and hindlimb lengths were also not different (P=0.104, P=0.8). For endurance horses, stride data for nonfatigued horses were consistent with data extrapolated to 4.5 m/sec from nonfatigued horses on the treadmill. Endurance horses slowed (P = 0.002) during the race from 4.55 to 4.03 m/sec and stride lengths were shorter. Despite a slower speed, other stride parameters were unchanged. Hindlimb length was shorter in fatigued horses.Conclusion:Horses fatigued on a treadmill and during the natural course of an endurance ride responded differently, biomechanically. On the treadmill, where speed is constrained, stride frequencies decreased and stride lengths increased. During one endurance ride, stride frequencies were the same, although speeds were substantially reduced. Limb length was shorter in fatigued endurance horses. It remains to be determined if these changes in mechanics are advantageous or disadvantageous in terms of energetics or injury. Further examination of endurance rides is also warranted.
Measurements of fitness in Thoroughbred racehorses using field studies of heart rate and velocity with a global positioning system
Authors: VERMEULEN A. D. , EVANS D. L. 
Published: June 2010

SummaryReasons for performing study:Field based studies of changes in fitness are difficult to conduct in galloping Thoroughbreds. Measurements of heart rate (HR) and real time velocity with a global positioning system (GPS) could provide a method for routine field studies of fitness.Objective:To investigate measurements of fitness in the field without using multiple, standardised steps of increasing velocity in the exercise test.Methods:Twelve healthy 3‐ to 5‐year‐old Thoroughbreds were used in the study of reliability, and twelve 2‐year‐old Thoroughbreds in the investigation of the effect of training. Five second averages of velocity and HR were recorded during a typical fast exercise training session, using a GPS and Polar HR monitor. A standardised exercise test protocol was not used. Regression analyses using trot and gallop data were used to calculate velocities at HR of 200 beats/min (V200), and at maximal HR (VHRmax). Data were collected on consecutive ‘fast’ day training sessions to assess the reliability of measurements. The effect of training was investigated with fitness tests in weeks 2 and 6 of ‘fast’ training. Absolute and relative differences were calculated to evaluate reliability, and pairedttests were used to detect an effect of training.Results:VHRmax, V200and HRmaxwere reliable measurements of fitness, with mean differences of 2% or less. Reliability of VHRmaxwas not dependent on VHRmax. VHRmaxand V200both increased significantly with training (P<0.01), but there was no effect of training on HRmax. There were no significant changes in the slope or intercept of the regression equations after training.Conclusions:Velocity and HR measurements during field gallop exercise provided reliable measures of fitness which enabled a measurement of the response to training.Potential relevance:This approach offers a simple, noninvasive method for monitoring adaptations to training in the field.