bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metabolic responses to submaximal field exercise tests and relationships with racing performance in pacing Standardbreds
Authors: DAVIE A. J. , PRIDDLE T. L. , EVANS D. L. 
Published: June 2010

SummaryThis study was undertaken to invesigate the application of submaximal field tests in assessment of performance. A submaximal field exercise test consisting of 2 bouts of pacing for 1600 m, with 5 min rest or walking between runs was performed on Standardbred racehorses at 2 training centres (A and B). Performance indices were compiled for each horse: number of race starts, number of race wins, number of race placings (1, 2 or 3), and lifetime earnings. Regression analysis was conducted to describe the relationship between plasma lactate concentrations and speed for tests one, 2 and pooled results. Using the regression equation, observed (measured) minus expected (predicted) (O‐E) lactate concentrations for tests were calculated and plotted against performance indices to determine their relationship. For stables A and B the association between lactate and velocity for the 2 runs was best described by the exponential equations: y = 0.0014e07306x(r2= 0.54, P<0.001) and y = 0.002e06812x(r2= 0.42, P<0.001), respectively, where y is lactate concentration (mmol/l) and x is speed (m/s). For the pooled results for heat 1 and heat 2 for stables A and B the relationship between lactate and velocity was best described by an exponential equation y = 0.0016e07117x(r2= 0.47, P<0.001). This study found no relationship between (O‐E) and performance indices (number of race wins, number of race placings, lifetime earnings and average /start) at stables A or B for test run 1, 2 or pooled lactates. At stable A, there was a significant association between VLa4and log lifetime earnings (r = 0.51, P = 0.053) and log average /start (r = 0.54, P = 0.036). There were no significant correlations at stable B. In conclusion a 2‐step determination method of VLa4is a possible means for studying limits to performance in pacing Standardbred racehorses.
Antioxidant status and muscle cell leakage during endurance exercise
Authors: HARGREAVES B. J. , KRONFELD D. S. , WALDRON J. N. , LOPES M. A. , GAY L. S. , SAKER K. E. , COOPER W. L. , SKLAN D. J. , HARRIS P. A. 
Published: June 2010

SummaryAntioxidant status of 35 endurance horses was studied during an 80 (OD80) or 160 km (OD160) race. Packed cell volume (PCV), total plasma protein (TPP), plasma ascorbic acid (VIT C), plasma α‐tocopherol (VIT E) and erythrocyte glutathione (GSH) concentrations, erythrocyte glutathione peroxidase (GPX), plasma aspartate aminotransferase (AST) and plasma creatine kinase (CK) activities were measured at 0, 40, 80 km and 60 min of recovery (REC) at OD80, and 0, 64, 106, 142, 160 km and REC at OD160. In both races, no changes were found in plasma VIT E concentration, but VIT C and GSH concentrations decreased (P<0.05), and mean GPX, AST and CK activities increased from 0 km (P<0.05). Indices of muscle cell leakage (plasma AST and CK) were correlated (r = 0.36 to 0.67; P<0.03) with indices of antioxidant status (VIT C, GSH and GPX). Associations between increased muscle leakage and decreased antioxidant status may, in part, reflect oxidative stress and suggest the testing of antioxidant supplements in endurance horses to improve performance and welfare.
Physiological responses of young Thoroughbreds during their first year of race training
Authors: OHMURA H. , HIRAGA A. , MATSUI A. , AIDA H. , INOUE Y. , ASAI A. , JONES J. H. 
Published: June 2010

SummaryYearling horses are typically trained for more than a year before they begin racing; therefore, we questioned how relevant analyses of the initial responses to training are compared to physiological responses that occur over a year of training, and whether young horses with no history of training would respond the same as older horses that had been trained previously. We hypothesised that changes in O2transport over the last months of a year of training would be different than at the beginning. We trained 5 yearling Thoroughbreds and evaluated metabolism, O2transport and echocardiograms. Measurements were made before breaking (T1), after 6 months of training (T2) and following an additional 4 months of training (T3). We compared 5 trained horses (TR) with 5 untrained (UT) sex‐, size‐ and age‐matched yearlings kept at pasture and in boxes. Satellite telemetry indicated UT moved less total daily distance than TR during winter and more during summer, but UT walked for 80% of their distance, TR only 25%. The UT increased body mass (Mb) after T1 by 13% and were significantly heavier and fatter than TR. Specific aerobic capacity (V̇O2max/Mb) increased by 16% in both groups at T2, but by T3 was not different from T1 in UT, but was higher in TR (19%>T1, 15%>UT). In TR, specific cardiac output (Q/Mb) increased by 13% at T2, and specific stroke volume (Vs/Mb) were larger at T2 and T3 than T1 and UT at the same times both by physiological (15–16%) and echocardiographical (22–23%) estimates. Increased Vswas a primary correlate of the sustained increase in V̇O2max/Mbin TR. The large increases in Vsand V̇O2maxhad occurred by T2 and changed only slightly by T3.
Effect of training on age‐related changes in plasma insulin and glucose
Authors: MALINOWSKI K. , BETROS C. L. , FLORA L. , KEARNS C. F. , McKEEVER K. H. 
Published: June 2010

SummaryThe purpose of the study was to determine whether 12 weeks of exercise training would affect plasma glucose and plasma insulin concentrations in young and older Standardbred mares. Eighteen healthy, unfit mares representing 3 age groups were used: young (Y = 6.8 ± 0.4 years; n = 6), middleaged (MA = 15.2 ± 0.4; n = 6), and old (O = 27.0 ± 0.2; n = 6). Pre‐ and post‐training incremental exercise tests (GXT) were performed to measure plasma glucose and insulin concentration from immediately after, until 120 min postexercise. Training consisted of exercise 3 days/week (weeks 1–8) and 4 days/week (weeks 9–12) at a submaximal intensity (∼60% of pretraining HRmax) for ∼30 min/day. Old mares had lower levels of glucose after the GXT when compared to Y and MA mares (P<0.05). There was also a time‐by‐age interaction (P = 0.003) in that, at 120 min post‐GXT, glucose levels had not returned to pre‐exercise values. Plasma glucose concentrations, in response to acute exercise, were not altered by training for any age group (P>0.05). Prior to exercise training, O mares had higher plasma insulin compared to Y and MA mares at 120 min postexercise (P<0.05), and insulin was also elevated in O mares compared to all other time points at 120 min post‐GXT (P<0.05). Training resulted in increased plasma insulin concentrations at 120 min post‐GXT in all age groups (P<0.05). In conclusion, age affected glucose and insulin responses to acute exercise prior to and after 12 weeks of exercise training. With regards to insulin, 12 weeks of exercise training resulted in a postexercise rebound hyperinsulinaemia, which may be related to an increased need for glycogen repletion in the muscle. These factors are important in considering the ability of an older horse to tolerate exercise.
Relationship between markers of blood oxidant status and physiological variables in healthy and heaves‐affected horses after exercise
Authors: KIRSCHVINK N. , ART T. , DE MOFFARTS B. , SMITH N. , MARLIN D. , ROBERTS C. , LEKEUX P. 
Published: June 2010

SummaryExercise‐induced oxidative stress is investigated as a potential performance‐limiting factor in human sports medicine. Therefore, the present study aimed to assess whether physiological variables that change with exercise intensity were correlated with blood oxidant markers in healthy and heaves‐affected horses. Seven healthy horses, 8 heaves‐affected in remission and 7 heaves‐affected in crisis performed a standardised exercise test (SET) of stepwise increasing intensity. Variables monitored during exercise were heart rate (HR), venous plasma lactate (LA), packed cell volume (PCV) and arterial oxygen tension (PaO2). Oxidant markers (uric acid [UA], 8‐iso‐PGF2αand reduced [GSH] and oxidised glutathione [GSSG]) were analysed in venous peripheral blood sampled at rest (R), at peak‐exercise intensity (Emax), 15 (E15) and 60 (E60) min after SET. There was a significant effect of heaves on oxidant markers and, therefore, correlation analyses between physiological variables and oxidant markers were performed separately per horse group. In healthy horses, UA analysed at Emax was positively correlated with LA. Furthermore, GSH analysed at Emaxand E15was positively correlated with PaO2. In healthy and heaves‐affected horses in remission, GSH and GSSG determined at Emaxwere negatively correlated with HR. There was no significant correlation between 8‐iso‐PGF2αand physiological variables. In conclusion, a correlation between the physiological response to exercise and some oxidant markers exists in healthy horses. However, in heaves‐affected horses the blood oxidant status is probably more dependant on airway disease than on exercise. Future studies should be undertaken to assess whether antioxidant supplementation might positively influence the oxidant‐antiodidant balance in exercising horses.
Equine endurance exercise alters serum branched‐chain amino acid and alanine concentrations
Authors: TROTTIER N. L. , NIELSEN B. D. , LANG K. J. , KU P. K. , SCHOTT H. C. 
Published: June 2010

SummarySix 2‐year‐old Arabian horses were used to determine whether 60 km prolonged endurance exercise (approximately 4 h) alters amino acid concentrations in serum and muscle, and the time required for serum amino acid concentrations to return to basal resting values. Blood and muscle samples were collected throughout exercise and during a 3 day recovery period. Isoleucine concentration in muscle tended to increase and leucine and valine did not change due to exercise. Serum alanine concentrations did not increase immediately after exercise, but increased at 24, 48 and 72 h postexercise. Serum isoleucine, leucine, and valine concentrations decreased after exercise and time required to reach pre‐exercising concentrations was 48 h. In conclusion, endurance exercise in the horse decreases serum isoleucine, leucine, and valine concentrations, and increases serum alanine concentration. The decrease in serum branchedchain amino acid concentrations did not correspond to a measurable increase in total muscle branched‐chain amino acid concentrations.
Maintenance of bodyweight during a multiple‐day chuckwagon race meet
Authors: WARREN L. K. , WHELEN A. 
Published: June 2010

SummaryThe gruelling race schedules maintained by horses competing in chuckwagon racing raises concern for the horses' ability to recover quickly and continue to perform at a high level. The amount of bodyweight lost and the time required for recovery of this weight loss have been used to assess the level of stress imposed on horses competing in various multiple‐day events. In this study, bodyweights were obtained from 40 Thoroughbred geldings (mean ± s.e.; bodyweight 521.5 ± 4.4 kg) before and after racing during a 5 day chuckwagon race meet. Body condition score (BCS) was determined on the first and last day of competition. Comparisons were based on the number of consecutive days the horse raced. Average bodyweight loss (P = 0.039) from each race was 3.5 ± 0.3 kg (0.7% of initial bodyweight) and was not affected by the number of days the horse raced. The largest bodyweight deficit (P = 0.005) occurred within the 24 h period after their first race (5.3 ± 0.5 kg; 1.0% of initial bodyweight). Horses racing on 2–5 consecutive days retained a 4.8 ± 0.3 kg deficit (P = 0.01), which was maintained throughout the remainder of the race meet. Horses began and ended the race meet with a BCS of 4.9 ± 0.2 and 4.7 ± 0.2, respectively (using the 1 to 9 BCS system). Although chuckwagon horses compete in a strenuous event on several consecutive days, they appear to be managed well and have the ability to maintain their bodyweight despite the physical and psychological demands of frequent racing.
Benefits of moderate training to the nonspecific immune response of colts
Authors: ESCRIBANO B. M. , AGÜERA E. I. , VIVO R. , SANTISTEBAN R. , CASTEJÓN F. M. , RUBIO M. D. 
Published: June 2010

SummaryThe aim of this work was to assess whether progressive training caused an improvement in the nonspecific immune response of colts because several unusual infections are due to defects inherent in the neutrophilic function among which respiratory diseases are a major defect in the performance of athletes taking part in professional sports activities. A group of 7 Anglo‐Arabian colts belonging to the Army was selected. These animals carry out training programmes for their participation in National Jumping Competitions. During a submaximal exercise test (heart rate 150 beats/min and lactate levels maintained at aerobic‐anaerobic threshold of 3 mmol/l), they were compared with 5 colts of the same breed, just beginning training exercises. Immediately after the test, the nonspecific immune capacity of neutrophilic polymorphonuclear cells was valued by adherence, chemotaxis, ingestion and digestion of foreign substances tests. The results showed significant differences between trained and nontrained animals for the adherence and foreign particle digestion tests and, beginning with a greater adherence in untrained animals, a superior effectiveness was achieved in the immune function in trained colts, whose digestive capactiy was increased with respect to the untrained ones. It was, therefore, concluded that moderate training and exercise improves and reinforces the response of the nonspecific immune system against future infections in the organisms.
Effect of exercise on plasma ferritin concentrations: implications for the measurement of iron status
Authors: HYYPPÄ S. , HÖYHTYÄ M. , NEVALAINEN M. , PÖSÖ A. R. 
Published: June 2010

SummaryIron is of key importance for aerobic metabolism, and natural feeds of the horse are fairly rich sources of iron. Accordingly, the known incidence of iron deficiency anaemia is apparently rare in performance horses; despite this, iron deficiency in performance horses continues to be of concern to trainers and veterinarians. Effects of exercise on plasma ferritin concentrations were therefore studied in Standardbreds, Finnhorses and half‐bred riding horses. Blood samples were taken after a moderate exercise test on a racetrack, a competition exercise test on a treadmill and a race. Even moderate exercise caused an increase in plasma ferritin concentration, with the increase being greater as the intensity and duration of exercise increased. Return to the basal level was slower after maximal‐intensity exercise than after moderate exercise. In conclusion, although ferritin is a useful marker of low iron stores, samples should be taken only after at least 2 days rest following strenuous exercise.
Effect of glucosamine on interleukin‐1‐conditioned articular cartilage
Authors: FENTON J. I. , CHLEBEK‐BROWN K. A. , CARON J. P. , ORTH M. W. 
Published: June 2010

SummaryGlucosamine inhibits recombinant human interleukin‐1 stimulated cartilage degradation in equine cartilage explants. Recently, recombinant equine interleukin‐1 has been cloned and purified. Therefore, the objective of this study was to characterise the effects of glucosamine on indices of cartilage degradation in recombinant equine IL‐1β‐stimulated equine articular cartilage explants. Cartilage discs were harvested from the weight‐bearing region of the articular surface of the antebrachiocarpal and middle carpal joints of horses (age 2–8 years) and cultured under standard conditions. Explants were exposed to recombinant equine interleukin‐1β (reIL‐1β) on Days 1–4 in the presence or absence of glucosamine (0.25, 2.5 or 25 mg/ml), with appropriate controls. Nitric oxide, prostaglandin E2, sulphated proteoglycan, stromelysin and gelatinase/collagenase activity released into conditioned media and total tissue proteoglycan content were measured as indicators of cartilage catabolism. Glucosamine inhibited cartilage catabolic responses in a dose dependent manner that was statistically significant at a dose of 0.25 mg/ml for stromelysin activity and 2.5 mg/ml for collagenase/gelatinase activity. At 25 mg/ml glucosamine also prevented IL‐1β‐induced increases in nitric oxide production, prostaglandin E2and proteoglycan release to media. Glucosamine prevents equine articular cartilage degradation experimentally induced by reIL‐1±in vitro.These data provide further support for the use of glucosamine in treatment or prevention of cartilage loss in athletic horses.
Correlation of cartilage oligomeric matrix protein (COMP) levels in equine tendon with mechanical properties: a proposed role for COMP in determining function‐specific mechanical characteristics of locomotor tendons
Authors: SMITH R. K. W. , GERARD M. , DOWLING B. , DART A. J. , BIRCH H. L. , GOODSHIP A. E. 
Published: June 2010

SummaryOver‐strain injury of the superficial digital flexor tendon (SDFT) is a common injury in the horse. Tendon appears to adapt to loads placed on it during development, but fatigue damage accumulates after skeletal maturity, which is inadequately repaired and predisposes to clinical tendinitis. In any population of horses, there is a wide variation in SDFT mechanical properties. A noncollagenous protein, cartilage oligomeric matrix protein (COMP), is particularly abundant during growth in the equine SDFT and has been proposed to have an organisational role in the formation of collagenous matrices. This study aimed to determine whether COMP levels were correlated to mechanical properties at skeletal maturity. Tendons from 2 groups of 12 horses were analysed:Group 1horses with restricted age, 2 years ± 2 months, showed a significant correlation between both ultimate tensile stress modulus of elasticity and stiffness and COMP, whileGroup 2mature horses with varying age did not, because of age‐ and exercise‐induced loss of COMP. These data supports the hypothesis that COMP is an important mediator in the growth of tendon. This data would suggest that the identification of low COMP levels in tendon during growth would indicate horses prone to tendon injury and methods of promoting COMP synthesis during growth would potentially improve tendon quality and reduce the risk of subsequent tendinitis.
Effects of mild forelimb lameness on exercise performance
Authors: PARENTE E. J. , RUSSAU A. L. , BIRKS E. K. 
Published: June 2010

SummaryMild lameness is considered a performance‐limiting problem that may escape detection until it worsens, and is considered the primary reason for reduced racing performance. The kinematics changes associated with a lame horse at the trot have been demonstrated previously, but the metabolic cost of these alterations in their gait have not been demonstrated. Six fit Thoroughbred horses with an established V̇O2maxparticipated in 4 trials using a randomised cross‐over design study, separated by 10–14 days. The horses were tested with one of 4 trial conditions: lead forelimb lameness (LL); off‐lead forelimb lameness (OL); bilateral forelimb lameness (BL) or no lameness (NL). Lameness was induced by sole pressure from a modified shoe that resulted in a consistent slight head nod at a trot in a straight line while jogging in hand. Lameness was adjusted to provide a lameness that would be quantified as a 1–2/5 on the grading system recommended by the AAEP. Each trial consisted of 4 different levels of exercise intensity at speeds equivalent to 30, 60, 80 and 110% of an individual's speed required to elicit V̇O2max. Stride parameters, oxygen consumption (V̇O2), carbon dioxide production (VCO2), electrolytes, plasma lactate, glucose and PCV/TP were measured prior to exercise, at each exercise level and after exercise. A multiway ANOVA with repeated measures was utilised to examine possible effects of individual horse, lameness, and exercise intensity on measured parameters. Significance was set at α = 0.05.For horses exercising at the maximum intensity, V̇O2was significantly lower for both of the single‐leg lamenesses (LL or OL) when compared to NL or BL (mean ± s.e. 165.6 ± 2.5, 164.7 ± 3.0, 175.8 ± 2.4 and 170.9 ± 2.1 ml O2/min/kg bwt, respectively). Blood lactate concentrations were not significantly different among the treatment groups. However, lactate accumulation rates computed as the change with time in lactate concentration at the highest exercise intensity were significantly higher for LL and OL than for NL and BL (7.8 ± 0.3, 8.3 ± 0.2, 4.1 ± 0.2 and 4.7 ± 0.3 mmol/min, respectively). Exercise intensity had significant effects on all of the measured parameters, but there were no other significant differences due to treatment. These results suggest that metabolic energy transduction is affected by even mild unilateral forelimb lamenesses.
Exercise‐induced tendon hypertrophy: cross‐sectional area changes during growth are influenced by exercise
Authors: KASASHIMA Y. , SMITH R. K. W. , BIRCH H. L. , TAKAHASHI T. , KUSANO K. , GOODSHIP A. E. 
Published: June 2010

SummaryMost skeletal tissues are thought to adapt to the mechanical environment they experience. While this has been demonstrated for muscle and bone, previous studies in the mature horse have failed to demonstrate adaptation in the superficial digital flexor tendon (SDFT), which suffers a high frequency of injury. This study tested the hypothesis that imposed exercise during growth would result in an increase in SDFT cross‐sectional area (CSA). Fourteen Thoroughbred foals were divided into 2 sex‐matched groups. A control group received 4 h pasture exercise and an exercise group had the same amount of pasture exercise with an additional short period of treadmill exercise daily from age 2–15 months. Activity at pasture was assessed objectively using a visual system. There was no significant difference in pasture activity between groups, although males were more active than females. The exercise programme resulted in a significantly larger tendon CSA in the exercise group at several, but not all, timepoints, which may be attributed to levels of variance. However, there was a significantly greater rate of increase in tendon CSA as a function of time in the exercised compared to the control group. This is the first evidence to suggest that tendon development can be modulated by exercise during growth in the horse, potentially increasing the ability of tendon to withstand the rigours of later athletic activity.
Myosin heavy chain‐based fibre types in red cell hyper‐ and normovolaemic Standardbred trotters
Authors: KARLSTRÖM K. , ESSÉN‐GUSTAVSSON B. 
Published: June 2010

SummaryAn assumed link between red cell hypervolaemia, an excessive amount of training and impaired performance of hypervolaemic horses has led to a theory that the muscle fibres could be affected. Myosin heavy chain (MHC)‐based fibre type composition in gluteus medius muscle of red blood cell normo‐ (NV) and hypervolaemic (HV) Standardbred trotters was evaluated using immunohistochemistry. Muscle biopsies were obtained from 13 NV and 16 HV horses. Serial transverse sections were cut and reacted with antibodies against different isoforms of the myosin heavy chains MHCI, MHCIIA and MHCIIX. Sections were also stained for myofibrillar ATPase pH 4,6 to identify types I, IIA and IIB, and NADH tetrazolium reductase to evaluate the oxidative capacity. The results show that types I and IIA fibres corresponded between staining methods, whereas IIB fibres in the ATPase stains were more numerous than pure MHCIIX fibres from immunohistochemistry. Many fibres identified histochemically as type IIB fibres contained both MHC isoforms IIA and IIX (MHCIIAX). Most fibres had a high oxidative capacity, but among the fibres within a section, the lowest was seen subjectively in pure MHCIIX fibres. Immunohistochemical stains make it possible to detect differences in fibre type composition that are not observed with myosin ATPase stainings, as it was found that HV horses had a lower percentage of MHCIIX fibres than NV horses. Immunohistochemical methods are, therefore, valuable for use in further research and clinical studies concerning muscle adaptations.