bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of low‐ and moderate‐intensity training on metabolic responses to exercise in Thoroughbreds
Authors: EATON M. D. , HODGSON D. R. , EVANS D. L. , ROSE R. J. 
Published: June 2010

SummaryThis experiment was undertaken to determine whether there were differences in cardiorespiratory, haematological and muscular responses in horses trained at either low or moderate intensities. Ten Thoroughbred horses previously rested in paddocks for 4 months were trained 5 days/week for 9 weeks. Horses were allocated randomly into fast or slow groups and exercised the same distance each day. Training distances were 1600 m in Weeks 0 and 1 up to 4000 m in Week 9. The fast group were trained at an intensity inducing a post training blood lactate of 4–8 mmol/l. This intensity was determined for each horse each week. The slow group trained at half the speed of the fast group (blood lactate <2 mmol/l). Horses performed a standardised exercise test prior to (Week 0) and on Weeks 1, 2, 3, 4, 7 and 9 of training. HR, V̇O2, V̇CO2and blood lactate concentration were recorded during the last 15 s of each step. Blood samples were collected at the end of each test for determination of red cell and plasma volume. Muscle biopsies were collected from the middle gluteal muscle before training and after 4 and 9 weeks training.Training intensity had few effects on the majority of variables measured and results for both groups are combined unless otherwise stated. Bodyweight was unaffected by training. Economy of locomotion decreased from 12.0 ± 0.4 ml/kg bwt/m prior to training to 13.8 ± 0.6 ml/kg bwt/m at the end of training in the fast group. Run time to fatigue was not affected by training intensity. V̇O2maxincreased from 120.3 ± 4.8 to 144.7 ± 3.5 ml/kg bwt/min with a significant correlation between run time and V̇O2max. Peak HR was 221.4 ± 2.5 beats/min prior to training and 226.5 ± 1.7 beats/min after the first 4 weeks of training. V200and VLa4increased in response to training. Similarly, VLa4increased from 7.0 ± 0.5 to 9.2 ± 0.2 m/s with VLa4correlated to V̇O2max. Plasma volume decreased from 29.1 ± 1.7 to 25.8 ± 0.9 ***1 during the last 3 weeks of training. Blood volume, red cell volume and/or red cell volume/kg were unaffected by intensity or duration of training. The activity of CS in muscle increased in the first 5 weeks of training whereas HAD activity was not affected by intensity or duration of training.
Exertional rhabdomyolysis in Quarter Horses and Thoroughbreds: one syndrome, multiple aetiologies
Authors: VALBERG STEPHANIE J. , MICKELSON J. R. , GALLANT ESTHER M. , MACLEAY JENNIFER M. , LENTZ LINNEA , DE LA CORTE F. 
Published: June 2010

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

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

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

SummaryOur aim was to investigate plasma catecholamine responses to so‐called ‘doping’ drugs and exercise in Thoroughbreds. Plasma adrenaline (Ad) and noradrenaline (NA) were determined after the administration of caffeine and promazine hydrochloride (PRZ) using a high performance liquid chromatographic method. Caffeine or PRZ was administered i.m. to Thoroughbreds and its effects on plasma catecholamines at rest and during exercise were compared with the saline control. The treadmill exercise was performed 1 h after administration. A dose of 5.0 mg/kg bwt caffeine was found to significantly increase both plasma Ad and NA levels but this was not the case for the 2.5 mg/kg bwt dose and their peak levels at 1.5 h were about 3 and 2.5 times as compared with the control values at 1.5 h (Ad: mean ± s.e. 21.2 ± 2.8 pg/ml, NA: 55.5 ± 4.1 pg/ml), respectively. Both 1.0 and 1.5 mg/kg bwt PRZ doses reduced the plasma Ad to below the detection limit (10 pg/ml) and significantly reduced the plasma NA. The 2.5 mg/kg bwt caffeine dose significantly increased plasma Ad and NA during exercise and approximately doubled their maximal values as compared with the saline control (Ad: mean ± s.e. 12.328 ± 4.733 ng/ml, NA: 9.997 ± 4.146 ng/ml). The 1.5 mg/kg bwt PRZ dose decreased the plasma Ad during exercise but the effect was not significant. On the other hand, PRZ significantly increased the plasma N A as compared with the saline control. In conclusion, the present study demonstrates that the plasma catecholamine responses to caffeine and PRZ were modified by exercise. It is probable that the modification may be related to exercise‐induced activation of the sympathetico‐adrenal axis.
Comparison of bone mineral content and biochemical markers of bone metabolism in stall‐ vs. pasture‐reared horses
Authors: HOEKSTRA KARI E. , NIELSEN B. D. , ORTH M. W. , ROSENSTEIN DIANA S. , II H. C. SCHOTT , SHELLE J. E. 
Published: June 2010

SummarySixteen Arabian yearlings were assigned randomly to 2 groups, confined to stall and pastured, to investigate the effects of confinement vs. pasture‐rearing on bone mineral content and biochemical markers of bone metabolism over a 140 day period. Following an 84 day pretraining period, 6 horses from each group were selected randomly to complete a 56 day training period. Serum osteocalcin concentrations were determined from blood samples collected every 14 days. Urinary deoxypyridinoline concentrations and mineral content of the third metacarpus, as determined by lateral and medial radiographic bone aluminum equivalency (RBAE), were determined every 28 days from 24 h urine samples and radiographs of the left forelimb, respectively. In comparison with starting values, lateral RBAE was lower in the confined horses at Day 28 and remained lower throughout most of the project, while pastured horses had increasing lateral RBAE. Horses kept in stalls had lower medial RBAE at Day 28 than pasture‐reared horses. Medial RBAE tended to remain lower in confined horses than in pastured horses throughout most of the project The onset of training failed to negate the loss of mineral. Serum osteocalcin concentrations were lower and urinary deoxypyridinoline concentrations were higher in the confined horses at Days 14 and 28, respectively, compared with the pastured horses, and subsequently returned to baseline. These results suggest that housing yearling/2‐year‐old horses in stalls may be associated with a loss of bone mineral content in comparison with horses maintained on pasture.
Fragility of red cells during exercise is affected by blood pH and temperature
Authors: HANZAWA K. , KAI M. , HIRAGA A. , WATANABE S. 
Published: June 2010

SummaryWe examined the relationship in horses between osmotic fragility of erythrocytes (OFE) measured as the red cell haemolysis rates (HLR) in 0.56% NaCl and certain physiological characters. Animals were exercised on a treadmill: warmed up at 30% V̇O2max for 5 min or at 105% V̇O2max for 1 min, given an exercise test at 80 or 105% V̇O2max until fatigued, and then cooled down. The pH and temperature of the blood had a significant correlation for the HLR: r = 0.93 and 0.92 (P<.01) on arterial and mixed venous blood, respectively. In multiple regression analysis, heart rate and packed cell volume showed lower coefficients for the HLR. The present study suggested that, in exercising horses, 1) the increase of blood flow and release of erythrocytes from the spleen into the circulation have little effect on changes of OFE; 2) the decrease of blood pH promotes OFE; 3) the increase of the pH causes osmotic resistance in the cells and 4) an increase of blood temperature during exercise is associated with the decrease in the OFE.
Racing performance in red blood cell hypervolemic Standardbred trotters
Authors: PERSSON S. G. B. , ÖSTERBERG IRÉNE 
Published: June 2010

SummaryThe association between red blood cell hypervolemia (RCHV) and racing performance was examined in 116 Standardbred trotters referred to the clinic during a 5 year period with histories of impaired racing performance. Red cell hypervolaemia was the only significant abnormality detected in a thorough clinical examination, cell volumes ranging 116–178% of the predicted normal values. They were also compared with the performance traits of the contemporary Swedish Standardbred trotter population (n = 58,058). The performance traits were based on earnings per year and start, best annual racing time, % placings 1 to 3, and calculated individual performance indices (PI) published in the Annual Statistics for Swedish Trotting. These parameters were transformed to approach normal distributions.The results indicated that horses developing RCHV tended to have been superior athletes initially compared to the contemporary population average. After 3 to 4 years of racing (at mean age ± s.d. 5.5 ± 1.5 years) their racing performance declined rapidly during the year of diagnosis of RCHV. Therefore, both earning and placing traits were reduced and best racing time increased. Further, the PI, well above the population average prior to diagnosis, was reduced significantly. During the 3 year period following diagnosis, a slight improvement in racing performance was noted although it was not restored to previous racing form. It was concluded that RCHV in the Standardbred trotter may denote the end of a successful racing career.
Haematological and biochemical responses to training and overtraining
Authors: TYLER‐McGOWAN CATHERINE M. , GOLLAND LORRAINE C. , EVANS D. L. , HODGSON D. R. , ROSE R. J. 
Published: June 2010

SummaryWe sought a physiological marker of overtraining in horses, using commonly practised field and laboratory tests to allow early prediction and treatment of the syndrome. Thirteen Standardbred horses were trained as follows: phase 1 (endurance, 7 weeks), phase 2 (high intensity, 9 weeks) and phase 3 (overload, 18 weeks). In phase 3 the horses were divided into 2 groups: overload training (OLT) and control (C). The OLT group exercised at greater intensities, frequencies and durations than the C group. Overtraining occurred after 31 weeks and was defined as a significant decrease in treadmill run time to fatigue (RT) in response to a standardised exercise test (SET). Variables measured included: feed intake, bodyweight (BWT), resting haematology and plasma biochemistry and treadmill SETs to measure RT. The OLT group had a decrease in BWT after week 28 (P<.05) without a reduction in feed intake and a reduction in RT during the SET after 31 weeks. Signs persisted after 2 weeks of a reduced training load confirming overtraining. Haematology and biochemistry failed to detect any markers of overtraining. Although no physiological markers of overtraining were identified, empirical observations revealed that the behaviour of horses in the OLT group was different from those in the C group during the period of overtraining. This study reflects that a model of overtraining has been developed based on measurement of a reduction in performance; however, there were no consistent changes in haematology or serum biochemical values in association with the decrement in performance capacity.
Training‐induced alterations in glucose metabolism during moderate‐intensity exercise
Authors: GEOR R. J. , MCCUTCHEON L. J. , HINCHCLIFF K. W. , SAMS R. A. 
Published: June 2010

SummaryIn several species, physical conditioning (training) provokes a large shift in substrate utilisation during submaximal exercise. Few studies in horses have quantitatively examined these effects. Therefore, the effects of exercise training on plasma glucose kinetics during submaximal exercise were examined in 7 horses (5 Thoroughbred, 2 Standardbred; age 3–9 years) that had been paddock‐rested for at least 6 months. Two days after determination of maximum aerobic capacity (V̇O2max), horses ran on a treadmill (4° incline) at 55% of V̇O2max(UT) for 60 min or until fatigue and then completed 6 weeks of moderate‐intensity training on a treadmill (5 days/week). Following training and a second V̇O2maxtest, the horses completed exercise trials at the same absolute (ABS) and relative (REL) workload in random order, with at least 3 days between tests. After training, V̇O2maxhad increased (P<0.05) by 14.9% (mean ± s.e. pretraining 118.4 ± 7.4 ml/kg bwt/min; post‐training 136.1 ± 7.8 ml/kg bwt/min). Mean exercise duration was longer (P<0.05) in the ABS trial (57 ± 1.9 min) than in the UT (46 ± 3.9 min) and REL (49 ± 4.6 min) trials. Plasma glucose concentration increased during exercise, and was lower (P<0.05) in ABS than in UT and REL at the end of exercise. Mean glucose rate of appearance (Ra) and disappearance (Rd) were 22 and 21% lower (P<0.05), respectively, in ABS than in UT, but mean glucose Raand Rddid not differ between the UT and REL trials. Exercise‐induced changes in glucagon, epinephrine and norepinephrine were blunted (P<0.05) in ABS, but not REL, when compared to UT. It is concluded that 6 weeks of moderate‐intensity training results in a decrease in glucose flux during submaximal exercise at the same absolute, but not relative, workload. The training‐induced decrease in glucose flux may, in part, be due to altered plasma concentrations of the major glucoregulatory hormones.
Speed associated with plasma pH, oxygen content, total protein and urea in an 80 km race
Authors: HOFFMAN R. M. , HESS T. M. , WILLIAMS C. A. , KRONFELD D. S. , GRIEWE‐CRANDELL K. M. , WALDRON J. E. , GRAHAM‐THIERS P. M. , GAY L. S. , SPLAN R. K. , SAKER K. E. , HARRIS P. A. 
Published: June 2010

SummaryTo test the hypothesis that endurance performance may be related quantitatively to changes in blood, we measured selected blood variables then determined their reference ranges and associations with speed during an 80 km race. The plan had 46 horses in a 2 times 2 factorial design testing a potassium‐free electrolyte mix and a vitamin supplement. Blood samples were collected before the race, at 21, 37, 56 and 80 km, and 20 min after finishing, for assay of haematocrit, plasma pH, pO2, pCO2, [Na+], [K+], [Ca++], [Mg++], [Cl−], lactate, glucose, urea, cortisol, α‐tocopherol, ascorbate, creatine kinase, aspartate amino transferase, lipid hydroperoxides, total protein, albumin and creatinine, and erythrocyte glutathione and glutathione peroxidase. Data from 34 finishers were analysed statistically. Reference ranges for resting and running horses were wide and overlapping and, therefore, limiting with respect to evaluation of individual horses. Speed correlations were most repeatable, with variables reflecting blood oxygen transport (enabling exercise), acidity and electrolytes (limiting exercise) and total protein (enabling then, perhaps, limiting). Stepwise regressions also included plasma urea concentration (limiting). The association of speed with less plasma acidity and urea suggests the potential for fat adaptation and protein restriction in endurance horses, as found previously in Arabians performing repeated sprints. Conditioning horses fed fat‐fortified and protein‐restricted diets may not only improve performance but also avoid grain‐associated disorders.
Effect of molassed sugar beet pulp on nutrient utilisation and metabolic parameters during exercise
Authors: KARLSSON C. PALMGREN , JANSSON A. , ESSÉN‐GUSTAVSSON B. , LINDBERG J.‐E. 
Published: June 2010

SummaryThe aim of this study was to investigate the effect of partly replacing oats with molassed sugar beet pulp in a traditional hay/oat diet on nutrient utilisation and metabolic parameters in exercising horses. In a change‐over experiment, 4 Standardbred geldings were fed a hay and oat‐based diet (Oat diet) and a hay and oat‐based diet where oats was partially replaced with molassed sugar beet pulp (MSBP diet). Each experimental period was 21 days during which total collection of faeces and urine was made and an exercise test (ET) performed. The crude fat digestibility was lower on the MSBP diet (P<0.05), while there were no differences in digestibility of other nutrients and energy and in the urinary excretion of nitrogen and energy. At rest plasma insulin were lower (P<0.05) 60 and 90 min postprandially on the MSBP diet, while no differences were found in plasma glucose and insulin between the diets during the ET. The peak plasma and muscle lactate values were lower (P<0.05) on the MSBP diet and the content of muscle glycogen was higher (P<0.05) after the ET on the MSBP diet. In conclusion, the metabolic response differed between diets giving a lower lactate response and a higher glycogen content in muscle after exercise on the MSBP diet. This suggests that the dietary carbohydrate composition may influence the rate of glycogenolysis with lactate production and support the hypothesis that MSBP can replace oats in a hay based diet without impairing nutrient utilisation and metabolic response in exercising horses.
Postprandial glucose and insulin responses to a postexercise grain meal
Authors: LAWRENCE A. C. St. , LAWRENCE L. M. , COLEMAN R. J. 
Published: June 2010

SummaryMany studies have examined the effect of pre‐exercise feeding on glucose and insulin responses of horses. The objective of this study was to determine whether exercise performed one hour prior to a meal would attenuate the glucose and insulin responses to a meal. Data collected from 8 mature geldings in a 2 period crossover design experiment were used to determine the postprandial glucose and insulin responses to a meal of oats offered 1 h postexercise. During each period, 4 horses received a test meal following a 14 h fast (NoEx) or a 14 h fast and exercise bout (PostEx) that consisted of 48 min walking and trotting. Blood samples were collected before and at 30 min intervals for 5 h after the meal was offered. Glucose and insulin concentrations were similar between treatments at all time points (P>0.15). Postprandial glucose and insulin concentrations increased at similar rates in both groups from 0 to 90 min. Peak glucose and insulin concentrations and area under the response curves were similar between treatment groups. Glucose:insulin was not different between treatment groups at any time point before or after the meal (P>0.17). Overall, the 48 min of light work performed 1 h before a meal did not affect glucose or insulin responses to the meal. A one hour interval after mild exercise appears to be sufficient to allow normal glucose metabolism of a grain meal.