bluuebunny/crossref_metadata_2025 huggingface dataset:
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

Sixteen 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

We 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

The 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

We 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

In 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

To 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

The 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

Many 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.
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

This 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

Antioxidant 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

Yearling 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

The 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

Exercise‐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

Six 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

The 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

The 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

Iron 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

Glucosamine 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

Over‐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

Mild 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

Most 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

An 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.
Effect of conformational aspects on the movement of the equine back
Authors: JOHNSTON C. , HOLM K. , FABER M. , ERICHSEN C. , EKSELL P. , DREVEMO S.
Published: June 2010

The relationship between structure and function is important in the judgement of the horse. Twenty sound riding horses walked and trotted on a treadmill. The movement of the backs of each of the horses was measured using a commercially available movement analysis system. Morphometric, spatiotemporal and kinematic information were correlated to investigate the effect of conformation on movement. Taller and heavier horses seem to have longer thoracic and lumbar backs, and are wider at the pelvis. Horses with longer strides extended and flexed their backs in the caudal saddle region to a greater extent at the walk, but not the trot. Horses with greater angle of L5 tend to extend and flex this region of the back more. At the walk and trot, a long thoracic back results in greater lumbar lateral bending. A negative relationship was found between the curvature of mid‐thoracic back and the amount of lateral bending of L1 and L3 and axial rotation of the pelvis at the trot. There are clear relationships between back conformation and movement that may be important to the orthopaedic health of the horse. Further understanding of the relationships between conformation, movement and injury may provide an objective basis for the evaluation of future performance and soundness.
Relationship between velocity and temporal variables of the flat shod running walk
Authors: NICODEMUS M. C. , HOLT K. M. , SWARTZ K.
Published: June 2010

The running walk of the Tennessee Walking Horse is often described as a faster variation of the walk, indicating the importance of velocity on the mechanics of the gait. Variations in gait variables create difficulties in clearly identifying the normal and abnormal running walk in a clinical evaluation. The objectives of this study were, therefore, to describe the flat shod running walk and to determine the relationship between velocity and the running walk. From frame‐by‐frame analysis of 60 Hz film, temporal variables were averaged for 6 strides from 6 horses performing an ‘easy’ (slow) and ‘strong’ (fast) running walk during a flat shod, easy‐rider Tennessee Walking Horse show class. The running walk at both velocities was a 4‐beat, symmetrical stepping gait with a lateral footfall sequence and lateral couplets. The velocity ranged from mean ± s.d. 2.66 ± 0.34 to 3.80 ± 0.18 m/s. For both velocities (slow, fast), hind stance as a percentage of stride duration (58 ± 3%, 56 ± 2%) was significantly longer than fore (51 ± 5%, 48 ± 1%); diagonal advanced placement (29 ± 2%, 37 ± 4%) and lift‐off (35 ± 5%, 39 ± 2%) were significantly longer than lateral (advanced placement: 22 ± 2%, 12 ± 3%; lift‐off: 18 ± 4%, 10 ± 2); and lateral bipedal support (50 ± 9%, 67 ± 7%) was significantly longer than diagonal (27 ± 6%, 16 ± 4%). Strong correlations were found between velocity and diagonal advanced placement (0.640), lateral lift‐off (‐0.924) and diagonal (‐0.648) and lateral (0.904) bipedal support. Understanding the running walk and the gait variations due to velocity may be important to both the performance and soundness of the Tennessee Walking Horse.
The effect of reins on kinetic variables of locomotion
Authors: BIAU S. , COUVE O. , LEMAIRE S. , BARREY E.
Published: June 2010

The equestrian literature and reports of experienced riders indicated that attitude of a horse's head and neck is related to the equine locomotion characteristics. The purpose of this study was to quantify the effects of 3 types of reins on locomotion at walk and trot. Eight saddle horses were tested in an automatic walker without reins, with rubber bands, Chambons and Back lift1, using the same procedure. The rubber bands closed the head‐neck angle, whereas the Chambons and the Back lift opened it. The gait characteristics were measured with the Equimetrix2 gait analysis system. Two accelerometric devices were fixed on the sternum and sacrum to measure the kinetic characteristics of the fore‐ and hindlimbs at walk and trot. Analysis of variance was used to test the effects of reins on the fore‐ and hindlimbs. All 3 types of reins significantly (P<0.05) modified walk and trot, with increased forelimb propulsion at the trot (P<0.05). Chambons increased the dorsoventral activity of the hindlimbs at the trot and hindlimb propulsion at the walk (P<0.05). Back lift increased forelimb dorsoventral activity both at the trot and walk (P<0.05). It was concluded that the Chambons increased the activity of the hindlimbs while Back lift increased that of the forelimbs.

The use of reins modified the head placement and the fore‐and hindlimbs activity. The specific effect of each type of rein can be used for training, rehabilitation or management of locomotor's injury.
A radiographic technique to assess the longitudinal balance in front hooves
Authors: TACCHIO G. , DAVIES H. M. S. , MORGANTE M. , BERNARDINI D.
Published: June 2010

The aim of this study was to validate a radiographic technique to measure objectively the longitudinal hoof balance in the horse. Ten left third phalanges (P3) obtained from front hooves and 19 left front hooves were used in order to assess the reliability of the radiographic technique and to identify any effect of rotation or alignment of specimens or distance between the X‐ray machine and the radiographic cassette, in measuring P3s structures and balance related parameters. A rotational support was made to hold specimens in order to standardise some of the conditions of X‐raying. The main axis of the frog was used as a marker for the sagittal plane of P3. Results showed that single radiographic measurements could have wide limits of agreement with actual measurements of the hoof (gold standard values). In order to limit errors we suggest the use of a combination instead of single parameters to assess balance. Rotation of the hoof is also to be controlled when a measurement of angles is needed. The radiographic technique used in this study can be used to objecticely measure balance parameters considered important in order to assess hoof balance.
EIPH: postrace endoscopic evaluation of Standardbreds and Thoroughbreds
Authors: BIRKS E. K. , SHULER K. M. , SOMA L. R. , MARTIN B. B. , MARCONATO L. , DEL PIERO F. , TELEIS D. C. , SCHAR D. , HESSINGER A. E. , UBOH C. E.
Published: June 2010

The incidence and severity of exercise‐induced pulmonary haemorrhage (EIPH) in the 2 most commonly raced horse breeds, Thoroughbreds (TB) and Standardbreds (STD), were studied, with particular interest in the possible influence of frusemide (F) and/or the breed (or running gait) on EIPH. The appearance of blood within the trachea was semi‐quantified using a published 5‐point system, with zero assigned when no blood was observed, and numbers 1–4 assigned with increasing amounts of blood. Considering each endoscopic examination as a separate event, approximately 75% of the postrace endoscopic examinations had blood‐scores of 1, 2, 3, or 4, regardless of breed or F administration. For horses examined twice, the chances of finding blood‐scores of 1 or greater in either of the examinations increased to approximately 95%. All horses examined 3 or more times had endoscopic blood‐scores of 1 or greater following one or more races, again, irrespective of the breed or F administration. Mean ± s.e. ‘blood scores’ were 1.5 ± 0.1 and 1.8 ± 0.2 for TB, and 1.4 ± 0.2 and 1.2 ± 0.1 for STD racing with and without prerace F, respectively. Therefore, there was no apparent effect of breed (or possibly racing gait) on EIPH, and no differences in the incidence or severity of EIPH were observed between horses with or without prerace frusemide administration.
Effect of dorsal displacement of the soft palate on ventilation and airflow during high‐intensity exercise
Authors: FRANKLIN S. H. , NAYLOR J. R. J. , LANE J. G.
Published: June 2010

Dorsal displacement of the soft palate (DDSP) is one of the most common obstructive conditions of the upper respiratory tract in the racehorse. The present study was conducted to determine the effects of intermittent dorsal displacement of the soft palate (DDSP) on ventilation and respiratory airflow during high intensity exercise. Videoendoscopic recordings were made of the nasopharynx and larynx simultaneously with measurements of airflow and respiratory gas exchange, during high‐speed treadmill exercise in 9 horses with confirmed intermittent DDSP admitted for clinical investigation of poor racing performance.

In all horses, DDSP resulted in a reduction in minute ventilation (VE) (P<0.001), associated with a decrease in tidal volume (VT) (P<0.01) with no change in breathing frequency (f) and a reduction in oxygen consumption (V̇O2) (P<0.01). Further, DDSP resulted in reduction of expiratory flow parameters, including peak expiratory flow (PEF), EF50, EF25and EF12.5(P< 0.01), with no alteration of inspiratory flow. These results confirm that naturally‐occurring intermittent DDSP creates a flow‐limiting expiratory obstruction. The associated impairment of athletic performance is probably caused, at least in part, by the accompanying decrease of oxygen uptake.