bluuebunny/crossref_metadata_2025 huggingface dataset:
Maximum oxygen transport and utilisation before and after splenectomy
Authors: WAGNEFT P. , ERICKSON B. K. , KUBO K. , HIRAGA A. , KAI M. , YAMAYA Y. , RICHARDSON R. , SEAMAN JULIE
Published: June 2010

A major factor contributing to the athletic ability of the horse is exercise induced splenic contraction that augments both circulating blood volume (by about 12 litres) and haemoglobin concentration [Hb] (by a factor of 1.5–2). We examined separately the consequences of 1) splenectomy and 2) subsequent transfusion of blood at the lower post splenectomy [Hb] on pulmonary and muscle O2transport and pulmonary haemodynamics, to elucidate the separate influences of blood volume and [Hb] augmentation on these processes. We studied 6 Thoroughbreds (bwt 472 kg), (3 splenectomised, 3 controls). Splenectomy reduced V̇O2maxby 31 ± 3% (s.e.); transfusion of 11.7 litres whole blood at 42% haematocrit restored V̇O2maxto 94 ± 7% of original values. Splenectomy reduced maximal cardiac output by 15 ± 6%; transfusion increased it to 106 ± 10% of pre‐splenectomy values. The combination of splenectomy and transfusion reduced PaCO2by 14 ± 0.5 Torr, increased PaO2by 17 ± 0.4 Torr and arterial saturation by 5 ± 3% at V̇O2max. Splenectomy reduced maximal pulmonary artery pressure from 90.4 ± 1.4 to 42.4 ± 4.8 Torr; transfusion partially restored this to 71.5 ± 5.5 mmHg, despite the lower haematocrit. Splenectomy reduced muscle O2diffusional conductance (DO2) in direct proportion to the reduced maximal [Hb] while transfusion only slightly increased DO2. On the other hand, DO2was poorly related to changes in cardiac output.

Although based on a small number of horses, this study suggests that 1) increased [Hb] from splenic contraction is not essential for achieving V̇O2max; a normal circulating blood volume at a moderate [Hb] is sufficient, 2) [Hb] plays an important role in overall muscle O2diffusional conductance and also affects pulmonary artery pressure and 3) splenectomy produced substantial hyperventilation (in relation to V̇O2), permitting eucapnia and increased arterial oxygenation at V̇O2max. This was still observed after transfusion despite restoration of exercise capacity and V̇O2max.
Regional differences in pulmonary artery endothelial function: a role in the site of EIPH?
Authors: PELLETIER N. , ROBINSON N. E. , KAISER L. , DERKSEN F. J.
Published: June 2010

Exercise induced pulmonary haemorrhage (EIPH) is thought to result from capillary stress failure associated with high pulmonary vascular pressures during heavy exercise. One possible mechanism for the caudodorsal distribution of haemorrhage is preferential distribution of blood flow to affected regions due to regional differences in pulmonary vascular regulation. Endothelial cells (EC) are known controllers of vascular smooth muscle tone and could play a role in regional distribution of blood flow. The present study investigated relaxation responses to the endothelium‐dependent and independent vasodilators, methacholine (MCh) and nitroglycerin (NTG) in pulmonary arteries from the caudodorsal (top) and cranioventral (bottom) regions of the lung. Pulmonary arteries (7 mm diameter) from 6 horses were isolated from top and bottom regions of the lung and vessels with and without endothelium were mounted in 15 ml tissue baths. Vessels were pre‐contracted with norepinephrine (10−6M) and changes in isometric tension in response to MCh (10−6M) and NTG (10−6M) were compared. MCh consistently relaxed, and never contracted, endothelium‐intact top vessels. In top vessels, relaxation was abolished by removal of EC, suggesting an obligatory role of EC in MCh relaxation. However, in bottom vessels, a small transient relaxation was followed by a profound contraction, enhanced by EC removal. Relaxation to NTG was similar in all vessels. Therefore, in response to MCh, top vessels relax in an endothelium‐dependent manner, while bottom vessels contract. Similar regional differences in endothelium dependent flow mediated vasodilation may result in higher blood flow to the caudodorsal regions of the lung and hence be responsible in part for the location of EIPH.
Reproducibility of a standardised exercise test for Standardbred trotters under field conditions
Authors: DUBREUCQ C. , CHATARD J.C. , COUROUCE A. , AUVINET B.
Published: June 2010

The reproducibility of a standardised exercise test was evaluated in 2 conditions with 2 groups of Standardbred horses: 1) the first condition was a test and a re‐test performed with a 1 week interval by 11 trotters on their usual training track (2) the second condition was a test and a re‐test performed with another group of 8 horses on 2 different tracks with a 9 day interval, in order to assess the influence of changing the place of the test. The test was composed of 3 steps, conducted at an increasing speed. The duration of each step was 3 min with a 1 min rest between 2 steps at a walking pace. The speed level used for each step depended on the age and fitness of the horses. Mathematic treatment of the collected data, speed, heart rate and venous blood lactate measured after each step, allowed the estimation of 5 fitness parameters: V200, V4, V2, HR2and HR4. The Spearman rank correlation coefficients calculated for these indicators between the 2 tests measured during the experiment (1) and the experiment (2) were higher than 0.79 (P < 0.05) for V200, V4, V2and HR2.

The standardised exercise test proposed in the present work, was demonstrated to be reliable in field conditions for Standardbred horses.
Selected echocardiographic parameters and right sided pressures of the mule
Authors: TUCKER R. L. , WICKLER S. J. , LONDON C. , WYLE A. , GABBARD M.
Published: June 2010

Although there are references to mules having an innate ability to withstand higher work loads than horses, there are relatively few physiological studies that substantiate these statements. The purpose of this study was to establish baseline information on cardiac dimensions and right sided pressures of the normal mule using echocardiography and cardiac catheterisation. Selected cardiac dimensions of 10 adult non‐sedated mules were measured with 2‐D real time and M‐mode echocardiography. This was followed by catheterisation of the pulmonary artery, right ventricle and right atrium for measurement of pressures. End‐diastolic left ventricular lumen diameter, interventricular septum thickness, left ventricular free wall thickness and aortic root diameter measured mean ± s.d. 11.1 ± 1.5 cm, 2.8 ± 0.3 cm, 3.3 ± 0.3 cm and 7.0 ± 0.9 cm, respectively and the end‐systolic diameter for the left ventricular lumen measured 6.7 ± 1.3 cm yielding a fractional shortening of mean ± s.d. 40.4 ± 5.7%. Right atrial mean pressure, right ventricular peak systolic pressure and pulmonary arterial mean ± s.d. pressure measured 6.28 ± 1.6 mmHg, 55.3 ± 7.3 mmHg and 31.4 ± 5.4 mmHg, respectively. Although data collected from this study were limited to 10 normal animals, no significant difference in cardiac dimensions or right sided pressures were found compared to reported values in horses of similar size.
Sensory nerve fibres and receptors in equine distal forelimbs and their potential roles in locomotion
Authors: BOWKER R. M. , LINDER K. , SONEA I. M. , GUIDA L. A.
Published: June 2010

Sensory innervation of the equine distal forelimb was examined using several different anatomical techniques with each revealing a different morphological component of the sensory apparatus in the foot. Electron microscopic examination of the medial palmar nerve (N.digitalis communis II) revealed predominantly unmyelinated nerve fibres with a ratio of unmyelinated/ myelinated nerves at the level of the metacarpophalangeal joint of 3.67:1. Sensory peptides (substance P, neurokinin A, calcitonin gene‐related peptide and peptide histidine isoleucine) were observed immunocytochemically to innervate much of the equine foot, including the dermis of the dorsal wall and sole, the suspensory ligaments (ligamenta sesamoidea collateralia) (CSL) and the distal sesamoidean impar ligament (ligamentum sesamoideum distale impar), the synovial cavities and bones. These sensory peptides were usually associated with the adventia of the arterial vessels rather than the muscularis layer in contrast to neuropeptide Y. None or only scant immunoreactivity was present in the venules and capillary beds. Lamellated corpuscles in the loose connective tissues proximal to CSL appeared to be innervated by myelinated nerves. These different morphological components of sensory nerves innervating the equine digit suggest that these nerves are functionally complex in that during neurotransmission they have effects both within the spinal cord and within the peripheral tissues.
Electromyographic activity of the hindlimb muscles during the walk, trot and canter
Authors: TOKURIKI M. , AOKI O.
Published: June 2010

Thetensor fasciae lataeand the middle part of thebiceps femoriswere investigated electromyographically and kinematically in 4 Thoroughbred horses with or without a rider during the walk, trot and canter. EMG activity of thetensor fasciae lataebegan in the middle of the stance phase and ceased in the early period of the swing phase during the walk and trot in horses with or without a rider. During the canter, the onset and termination of muscle activity began earlier than during symmetrical locomotion. Its EMG activity had a higher amplitude during the stance phase than during the swing phase. These results indicate that thetensor fasciae lataemay act as an extensor or stabiliser of the stifle joint during locomotion. During the walk, EMG activity of the middle part of thebiceps femoriswas silent or weak. During the trot and canter, the muscle had a high amplitude of EMG activity and was active from the middle of the swing phase to the early or middle period of the stance phase in horses with or without a rider. This part of the muscle may work as an extensor of the hip joint during locomotion.
Temporal stride patterns in horses with experimentally induced fore‐ or hindlimb lameness
Authors: BUCHNEFP H. H. F. , SAVELBERG H. H. C. M. , SCHAMHARDT H. C. , BARNEVELD A.
Published: June 2010

In a kinematic study of equine lameness, temporal stride variables were investigated for their significance as diagnostic indicators and as a means of compensation for lameness. Kinematics of 11 clinically sound Dutch Warmblood horses were recorded while walking (1.6 m/s) and trotting (3.5 m/s) on a treadmill. A transient lameness model, provoking pain on the hoof sole, was used to induce 3degreesof fore‐ and hindlimb lameness. Intra‐ and interlimb stride variables as well as left‐to‐right symmetry were analysed using a 2 way analysis of variance (significance level: P<0.05). At the walk, stride duration was not affected by fore‐ or hindlimb lameness, while intra‐ and interlimb timing showed minor changes. At the trot, the stride duration in forelimb lameness decreased by 3.1% and relative stance duration of all limbs became longer (5.3% in forelimbs, 1.5% and 3.2% in hindlimbs). The diagonal advanced placement of the forelimbs increased and the duration of the suspension phase following the lame diagonal decreased by 61%. Left‐to‐right symmetry decreased for the suspension phase and contralateral advanced placement, while the stance durations remained symmetrical. In hindlimb lameness the stride duration at the trot decreased by 3.7% and the stance duration of the sound hind limb increased by 2.7%. Diagonal advanced placement, suspension phase and symmetry variables remained unaffected. It was concluded that compensation for lameness by changing temporal stride patterns is more pronounced in fore than in hindlimb lameness. The maintenance of symmetry in most stride variables in mild lamenesses limits their value as lameness indicators.
Kinematic analysis of successful and unsuccessful attempts to clear a water jump
Authors: CLAYTON HILARY M. , COLBORNE G. ROBERT , BURNS THERESA E.
Published: June 2010

Video recordings (60 Hz) of horses jumping a 4.5 m wide water jump were made during the team show jumping competition at the 1992 Olympic Games. The tapes were digitised and the results were analysed using the Ariel Performance Analysis System software and Statistical Packages for the Social Sciences. Eighteen horses were studied: 12 that cleared the water jump (Group 1) and 6 that failed to clear the width of the jump (Group 2). Four variables that influence the horizontal distance jumped were measured: horizontal velocity, vertical velocity, height of the centre of gravity (CG) at lift off and height of the CG at landing. The angle of projection was computed from the horizontal and vertical velocities. The angle of projection (Group 1: 15.2° ± 2.2°,Group 2: 12.2° ± 1.8°, F=0.010) and the vertical velocity of the CG (Group 1: 2.03 ± 0.22 m/s,Group 2: 1.56 ± 0.24 m/s, F=0.001) were significantly different between the 2 groups. There were no differences in the height of the CG at lift off (Group 1: 1.36 ± 0.08 m,Group 2: 1.40 ± 0.05 m), the height of the CG at landing (Group 1: 1.35 ± 0.12 m,Group 2: 1.30 ± 0.11 m) or the horizontal velocity of the CG (Group 1: 7.59 ± 0.60 m/s,Group 2: 7.48 ± 0.11 m/s). It was concluded that, to be a successful water jumper, the horse must generate a large vertical velocity during the take off.
Relative increase in areas of muscle fibre types in horses during growth
Authors: GUNN H. M.
Published: June 2010

The relative growth of muscle fibre types as distinguished by the myosin ATPase reaction at pH 9.5 in m. semitendinosus, m. diaphragma and m. pectoralis transversus of growing Thoroughbreds and other horses ranging in age from perinatal life to adulthood was investigated.

The growth rate of the area of myosin ATPase high‐reacting fibres in m. semitendinosus of both types of horse and in m. pectoralis transversus of Thoroughbreds was greater than that of low reacting fibres. Myosin ATPase low reacting fibres increased in area faster than high reacting fibres in the diaphragm of both types of horse and m. pectoralis transversus of other horses. These differential growth rates result in myosin ATPase high reacting fibres being larger than myosin ATPase low reacting fibres in m. semitendinosus and m. pectoralis transversus in adults of both types however, low‐reacting fibres are larger than high reacting fibres in m. diaphragma of adults of both types. These results suggest that the greater relative muscle mass of the proximal limbs of Thoroughbreds and associated greater mean fibre area associated are with relatively faster growing high reacting fibres in their muscles than those of other horses.
Slow myosin heavy chain content of muscles measured by ELISA
Authors: VALETTE J. P. , BARREY E. , JOUGLIN MAGGY
Published: June 2010

Equine type I muscle fibres were characterised in 14 muscles by enzyme‐linked immunosorbent assay (ELISA) with a monoclonal antibody specific for slow myosin heavy chains (MHC I). Slices of vastus lateralis, rectus femoris, biceps femoris, semitendinosus, semimembranosus, gluteus medius, gluteus superficialis, cutaneus trunci, masseter, triceps brachii, biceps brachii, deüoideus and diaphragm were obtained from a one‐year‐old Standardbred. For each muscle, 4 samples per slices were excised at different sites and 2 contiguous sub‐samples were immediately frozen in liquid nitrogen and stored at –80 °C until analysed. Muscle proteins were specifically extracted and analysed by ELISA. The MHC I content varied widely in the different muscles from cutaneus trunci (9%) to masseter (69%). A 3‐way analysis of variance showed that the MHC I content was different between muscles (P < 0.001) and within the sites studied (P < 0.01). The 2 contiguous sub‐samples were not different from each other (P > 0.05). It is concluded that the ELISA method allowed the accurate measurement of a wide range of MHC I in equine muscles. This technique is less time consuming than histological techniques and offers new applications for muscle fibre typing.
Blood hydrogen ion and lactate concentrations during strenuous exercise in the horse
Authors: KRONFELD D. S. , FERRANTE PAMELA L. , TAYLOR LYNN E. , CUSTALOW S. ELIZABETH
Published: June 2010

Exceptional findings in horses, such as metabolic alkalosis during exercise and an apparent absence of a distinct lactate threshold, led us to apply Stewart's acid‐base system and to develop a new statistical model for investigating lactate threshold. The lactate threshold was clearly demonstrated by an incremental exercise test using up to 14 steps. Lactate threshold was increased by training and by fat adaptation (prolonged interval training and a 10% corn oil diet). Fat adaptation appears to facilitate the metabolic regulation of glycolysis, sparing glucose and glycogen at work of low intensity, but promoting lactate production when power is needed for high intensity exercise. The blood lactate response to exercise was enhanced by fat adaptation and by oral supplementation of sodium bicarbonate. The synergistic effect of the combination suggested that inclusion of fat may enhance the advantage of a diet with a high cation‐anion balance. The lower CO2production of fat‐adapted horses could be of benefit under hot and humid conditions, especially in horses with reduced pulmonary function.

During repeated sprints, central venous [H+] increased (acidosis) but arterial [H+] decreased (alkalosis). These changes were consistent with concurrent changes in venous and arterial PCO2but not [SID]. Arterial PO2remained constant. These findings suggest that increasing ventilation to maintain arterial PO2incidentally reduced PCO2, hence arterial [H+]. In terms of homeostatic priorities, regulation of respiration took precedence over regulation of acid‐base status.
Sweat composition: comparison of collection methods and effects of exercise intensity
Authors: McCUTCHEON LAURA J. , GEOR R. J. , HARE MARTHA J. , KINGSTON JANENE K. , STAEMPFLI H. R.
Published: June 2010

The objectives of this study were to compare sweat collection techniques and determine effect of low and high intensity exercise on the composition and osmolality of equine sweat in exercise trained Thoroughbred horses. Sweat collection sites included the neck and thorax, bilaterally and behind the girth ventrally. Sweat was collected in cotton gauze, either exposed to the air or contained within a plastic pouch, from sealed pouches, with or without application of vaseline to the skin, and as it dripped off the skin behind the girth (free catch). There were differences in the ionic composition of sweat collected by different techniques during and after low (50% V̇O2max) and after high (90% V̇O2max) intensity exercise. These changes were most consistent where collection technique minimised evaporative losses. With regard to collection method, ionic concentrations and osmolality were lowest in samples obtained from sealed pouches without vaseline on the skin. In samples obtained from cotton gauze and by free catch, osmolality, [Na] and [Cl] were significantly increased when compared with sweat collected from sealed pouches. In samples collected from sealed pouches during low intensity exercise, osmolality increased 11%, [Na] and [Cl] increased 26% and 9%, respectively and [K] decreased 14%. Osmolality and the concentrations of these ions did not change during recovery. In contrast, osmolality increased by 12% in the first 5 min following high intensity exercise. After both intensities of exercise, there was a significant decrease in the concentration of protein in sweat collected by all methods. Results indicate that collection technique had a marked effect on composition of sweat as demonstrated by increased osmolality and increased concentrations of Na and Cl in sweat collected in cotton gauze and by free catch.
Weight loss, water loss and cation balance during the endurance test of a 3‐day event
Authors: ANDREWS F. M. , RALSTON SARAH L. , WILLIAMSON LISA H. , MAYKUTH PATRICIA L. , WHITE SUSAN L. , PROVENZA MELANIE
Published: June 2010

Bodyweights (BW) of 39 horses, competing in a 3‐day event, were measured the evening before the endurance test (BW1), afterphase D(BW2) and the next morning before stadium jumping (BW3). Plasma sodium concentration [Na1] was measured the evening before and afterphase Cof the endurance test [Na2]. Total body water (TBW1) was calculated using the formula (BW1 (kg) × 0.66 l/kg) and water loss (WL) was calculated as [(BW1– BWx) X 0.9]. Cation balance (CB), the exchangeable cation concentration, was calculated using the formula [(TBW1(1) X Na1) ‐ (TBW2(1)] X Na2). The decrease in BW and TBW averaged 17.4 ± 1.0 kg and 15.6 ± 0.8 litres respectively (mean ± s.e.m.) during the endurance test and remained decreased 9.2 ± 1.0 kg (BW) and 8.3 ± 1.0 litres (TBW) for 18 to 24 h after competition. Plasma sodium concentration afterphase Cof the endurance test (141.2 ± 0.3 mmol/l) was greater than resting values (138.8 ± 0.2 mmol/l), resulting in a net decrease in CB (‐1601.1 ± 171.7 mmol). Significant water and electrolyte losses occur in horses competing in the endurance test of a 3‐day event and these fluid losses persist for 18–24 h after this phase of competition.
Effects of sodium bicarbonate on acid‐base status and exercise capacity
Authors: LLOYD D. R. , ROSE R. J.
Published: June 2010

The first experiment examined the effects of 0.5 g/kg bwt and 1.0 g/kg bwt doses of sodium bicarbonate in 2 litres of water, administered by nasogastric tube, on venous blood bicarbonate concentration [HCO3−] in 12 Thoroughbred horses. The mean ± s.e. increase in [HCO3−] was 7.6 ± 0.4 mmol/l after the 0.5 g/kg dose and 10.1 ± 0.3 mmol/l after 1.0 g/kg. In a second experiment, the performance effects of sodium bicarbonate (1.0 g/kg bwt) and associated post exercise venous [HCO3−] were examined in horses given a high speed exercise test. Seven Thoroughbred horses received sodium bicarbonate (1.0 g/kg bwt) and venous [HCO3−] was measured after intense exercise (115% V̇O2max) on a treadmill. Blood bicarbonate concentrations were significantly higher in the treated horses for 3 h after exercise. The administration of sodium bicarbonate did not affect the run time to fatigue. We concluded that sodium bicarbonate (0.5 and 1.0 g/kg bwt) produced significant metabolic alkalosis, which persisted for up to 20 h after bicarbonate administration; and that post race sampling may allow detection of horses that have received sodium bicarbonate.
The long term effects of feeding fat to 2‐year‐old Thoroughbreds in training
Authors: PAGAN J. D. , BURGER I. , JACKSON S. G.
Published: June 2010

A study to evaluate the long term effects of feeding a fat supplemented diet during medium intensity, aerobic training was conducted over 7 months using 12, 2‐year‐old Thoroughbreds. The control group (n=6) was fed grass hay and a fortified sweet feed (CON) and the other group (FAT)(n=6) received hay, sweet feed, a supplement pellet and 400 ml of soybean oil that supplied about 12% of the DE intake of the FAT group. After 2, 4 and 7 months, the horses performed 2 standardised exercise tests (SETs) on a high speed treadmill. The first test (STEP) consisted of sequential steps of 800 m at speeds of about 4, 8, 9, 10 and 11 m/s. V200and VLA4increased with training, but were not different between treatment groups. During the last STEP, insulin was higher post feeding in the CON horses. Blood glucose was lower at the end of the STEP in CON horses. The second test (SET30) consisted of 30 min of trotting at about 4 m/s. Cortisol was elevated during exercise in the CON horses during the last SET30. T4was unaffected by diet or exercise. Consuming a fat supplemented diet altered the insulin response after feeding and this may have prevented a fall in blood glucose during strenuous exercise. Feeding a fat supplemented diet to 2‐year‐old. Thoroughbreds during training did not change red or white blood cell numbers or liver function as measured by serum levels of AST, γGT and SDH. Fat supplemented diets can be fed safely for extended periods of time to horses in training.
Glucose infusion increases maximal duration of prolonged treadmill exercise in Standardbred horses
Authors: FARRIS J. W. , HINCHCLIFF K. W. , McKEEVER K. H. , LAMB D. R.
Published: June 2010

The main purpose of this study was to describe the effect of glucose infusion on selected physiological variables and on the duration of treadmill exercise to fatigue. Six, 3–4 year old, clinically normal, Standardbred fillies were used in a randomised and balanced crossover design. The treatments were either an infusion of glucose (an initial bolus followed by an infusion rate adjusted during exercise to maintain glucose at approximately 9.0 mmol/l) or an infusion of a similar volume of normal saline. Saline was also infused during the first 30 min of recovery in both treatments. Treadmill speed and grade were 6.0 m/s and 2°. All horses underwent an exercise and dietary control period for 3 days prior to each treatment. A period of 7–10 days separated the treatments. Treadmill exercise duration was prolonged with glucose (89.8 min ± 15.4 s.e.m.) compared to saline (78.7 ± 12.4 min) (P<0.05). Plasma glucose concentrations were similar at rest and increased (P<0.05) above resting concentrations throughout exercise beginning at 15 min and 35 min for the glucose and saline trials, respectively. By 15 min of exercise, glucose concentrations were 8.72 ± 0.22 and 5.78 ± 0.28 mmol/l (P<0.05) for the glucose and the saline trials, respectively. Changes in haematocrit, plasma lactate, plasma total solids, plasma electrolytes, heart rate, core temperature, body weight and body water loss were similar for both treatments. An explanation for the glucose‐induced prolongation of exercise could be the availability of additional substrate during exercise.
Effect of time of feeding on metabolic response to exercise
Authors: LAWRENCE L. M. , HINTZ H. F. , SODERHOLM L. V. , WILLIAMS JANICE , ROBERTS A. M.
Published: June 2010

Four mature horses (3 Standardbreds and 1 Thoroughbred) were used in a 4 × 4 Latin square design experiment to investigate the effect of time of concentrate feeding prior to exercise on the metabolic response to exercise. Horses were fasted overnight and then given no feed (fasted) or 1 kg corn grain 1, 3 or 5 h before exercise. Exercise consisted of a warm‐up (1600 m at 6.0 m/s) and walk (800 m) followed by a high intensity phase (400 m at increasing speed and 1600 m at 11 m/s; 2% grade). During exercise, plasma glucose decreased in horses fed 1 or 3 h before exercise (P<0.05), but increased in horses fasted before exercise (P<0.05). Plasma insulin declined (P<0.05) during exercise in horses fed 1 or 3 h before exercise but did not change in horses that were fasted or fed 5 h before exercise. For all treatments, peak plasma free fatty acids (FFA) occurred during the walk phase and FFA decreased (P<0.05) during the last 2000 m (11 m/s; 2% grade). At the onset of exercise and during much of the exercise test, plasma FFA were highest in horses that were fasted for 16 h before exercise. Plasma lactate increased during the exercise test but was not affected by treatment (P>0.05). These data indicate that time of feeding prior to exercise can affect metabolic responses of horses to exercise, which could ultimately alter performance. In addition, researchers should consider that time of feeding may affect the interpretation of data from experiments examining the effects of diet and/or training on exercising horses.
Influence of nutritional status on metabolic responses to exercise in donkeys
Authors: MUELLER PAMELA J. , RAWSON R. E. , VAN SOEST P. J. , HINTZ H. F.
Published: June 2010

The metabolic consequences of submaximal exercise following long term nutritional deprivation were investigated in 6 donkeys. Animals were fed all roughage diets, either adequate (Timothy hay: H) or deficient in energy and protein (wheat straw: S) in a crossover design. After 8–10 weeks of dietary adaptation, responses to 60 min of moderate intensity draft loading exercise were compared. Jugular blood was sampled at rest and during exercise for glucose, lactate and free fatty acids (FFA) concentrations, haematocrit, Cortisol and insulin levels. Heart rate (HR) was monitored electronically. Resting lactate concentration was higher in animals fed hay (H) than in animals fed straw (S); only in S animals, however, did post exercise lactate concentration (1.55 ± 0.9 mmol/l) exceed pre‐exercise lactate concentration (0.6 ± 0.1 mmol/l). Hypoglycemia occurred in all animals in early exercise but was more pronounced in S animals. Straw‐fed animals had higher FFA concentrations at rest than H animals (mean ± s.e. 433 ± 71 vs. 102 ± 9 μmol/l). Plasma FFA concentrations declined precipitously in S animals at the onset of exercise, thereafter FFA increased over resting concentrations in both diets. Cortisol concentrations were higher at all times in H animals and increased during exercise regardless of diet. Insulin was lower in S animals and decreased during exercise in both diet groups. Resting HR was lower in S than in H animals (mean ± s.e. 34 ± 2 vs. 45 ± 2 beats/min). Exercising HR was greater in S animals. These data suggest that long term undernutrition in donkeys leads to decreased carbohydrate reserves, diminished maximal aerobic capacity and endocrine alterations. Work difficulty and stress level may increase, with possible negative implications for animal health and endurance.
Effects of phenylbutazone and frusemide on urinary excretory responses to high intensity exercise
Authors: II H. C. SCHOTT , RAGLE C. A. , BAYLY W. M.
Published: June 2010

To determine whether phenylbutazone or frusemide administration exacerbates the urinary excretory responses to high intensity exercise, 6 fully conditioned Thoroughbred mares were subjected to treadmill exercise at =120% of the V̇O2maxafter 4 treatments: 1) 4.4 mg/kg phenylbutazone i.v. 24 h prior to exercise (B); 2) 1.0 mg/kg frusemide i.v. 4 h prior to exercise (F); 3) 4.4 mg/kg phenylbutazone i.v. 24 h prior to exercise and 1.0 mg/kg frusemide i.v. 4 h prior to exercise (BF) and 4) placebo at both pre‐exercise times (C). Urine was collected for 4.5 h before exercise, during exercise and for 2 h after exercise.

Urine flow (UF) and urinary sodium excretion (UNAex) increased and urine osmolality (Uosm) decreased following frusemide administration (F and BF only). UF decreased (B and C only) during exercise and subsequently increased from a pre‐exercise value of 4.3 ± 0.4 (s.e.) ml/min (n=24) to 8.4 ± 4.1, 15.0 ± 3.6, 10.3 ± 4.2 and 9.5 ± 1.6 ml/min between 25 and 40 min following exercise for B, F, BF and C, respectively. This finding was only significant for F. Similarly, UNAexincreased from a pre‐exercise value of 0.05 ± 0.02 mEq/min (n=24) to 0.53 ± 0.34, 0.68 ± 0.30, 0.61 ± 0.38 and 0.67 ± 0.25 mEq/min between 25 and 40 min following exercise for B, F, BF and C, respectively. This finding was significant for B and F but not for BF or C. Uosmdecreased following exercise in all treatment groups.

Considerable within and between treatment variation in the urinary excretory responses to high intensity exercise was observed and precluded finding differences between treatment groups. To investigate this variation further, values for UF and UNAexbetween 25 and 40 min post exercise (period of greatest post exercise diuresis and natriuresis) were compared with peak plasma lactate concentration. Positive linear correlations were found for UF (r=0.65) and for UNAex(r=0.65). Thus, the magnitude of the diuresis and natriuresis which follows high intensity exercise in horses is related, in part, to work effort, as measured by plasma lactate concentration.
Exercise performance indices in normal and anabolic steroid treated trotters
Authors: HYYPPÄ S. , RÄSÄNEN L. A. , PERSSON S. G. B. , PÖSÖ A. REETA
Published: June 2010

Six adult Finnhorse trotters performed a standardised exercise test (SET) on a treadmill and a 4000 m maximal exercise test (MET) on a racetrack before, immediately and 13 weeks after a 14 week treatment with nandrolone laurate. Six other trotters served as controls. All horses were trained during the whole experiment. Blood lactate concentration, V200 VLa4 and red cell volume (CV) were determined in connection to the SET and blood lactate concentration, heart rate and performance time in the MET. All horses significantly improved their performance in the MET, but no differences were observed between the 2 groups. Nandrolone treatment caused a significant (P<0.05) increase in the CV and in the percentage of the oxidative type IIA fibres in the middle gluteal muscle. During the experiment V200 and VLa4 did not change (P>0.05) in either of the groups. The results indicate that CV was the only variable that predicted performance during the last 1000 m of the maximal test, whereas indicators of aerobic capacity, like V200 and VLa4, were of minor value. In the control group, the increase in the blood lactate concentration in the SET correlated positively with the total performance time (r=635; P<0.01) and the time of the last 1000 m (r=0.727; P<0.001) in the MET, but no correlation was found in the nandrolone group. The differences between the control and nandrolone groups suggest that both aerobic and anaerobic energy production in muscle are affected by nandrolone treatment.
Effect of dexamethasone on serum osteocalcin and metacarpal mineral content in horses
Authors: GEOR R. , WALSER MARY , KLASSEN JOAN , PIELA SUZANNE , KING VICKY , MURPHY M.
Published: June 2010

The objectives of this study were to determine the effect of 1) dexamethasone (DEX) on serum osteocalcin concentration (OC) in untrained and trained horses and 2) DEX, administered weekly, on serum OC and metacarpal bone mineral content in horses during training. Inexperiment 1, the baseline concentrations of OC and endogenous Cortisol (COR) were determined every 2 h during a 24 h period. Inexperiment 2, DEX (0.2 mg/kg bwt i.v.) was administered before and after 6 weeks of exercise training. Inexperiment 3, horses received either 0.2 mg/kg bwt i.v. DEX (n=5) or saline (n=5) i.v. on a weekly basis for 8 weeks, with the horses exercising 5 times per week. Metacarpal mineral content was measured weekly on each forelimb by photon absorptiometry. Inexperiment 1, serum COR concentration fluctuated between mean (± s.e.) 82 ± 4 (0800 h) and 22 ± 2 (2000 h) ng/ml, but significant variations in serum OC were not detected. Inexperiment 2, serum OC was decreased between 6 and 36 h after DEX treatment both pre‐ and post training. Inexperiment 3, serum OC was not different at any sampling time during any 7 day period after saline administration. In contrast, each week after DEX, serum OC was decreased between 6 and 48 h. However, differences in serum OC (P=0.055) and bone mineral content (P=0.055) between treatment and control groups were not detected over the 8‐week period. It was concluded that dexamethasone administered weekly to horses in exercise training altered the pattern of serum osteocalcin, but there was no change in metacarpal bone mineral content.
Urinary Cortisol excretion in the resting and exercising horse
Authors: TOUTAIN P. L. , LASSOURD V. , POPOT M. A. , LAROUTE V. , ALVINERIE M. , BONNAIRE Y.
Published: June 2010

The aim of this study was to document the 24 h urinary Cortisol concentrations during a rest day and a day that included prolonged exercise. The influence of exercise on disposition (plasma, urine) of a dose of Cortisol (1 mg/kg) was also assessed. Six adult saddle horses were used. In one experiment, urinary Cortisol elimination rates were measured during rest and prolonged exercise (56 km, 12 km/h) corresponding to about 50% of the V̇O2max. In another experiment, horses received, according to a crossover design, an intravenous (i.v.) bolus administration of Cortisol (1 mg/kg) either at rest or during the same prolonged exercise.

The urine Cortisol concentration was lower than 100 ng/ml in the control resting horse. It was increased by exercise but the maximal concentration was lower than 300 ng/ml and returned to control values by 10 h after the end of exercise. After 1 mg/kg Cortisol i.v. Cortisol clearance was decreased by exercise (552 ± 143 vs. 452 ± 59 ml/kg/h, mean ± s.d.), but the difference was not significant The peaks of urinary Cortisol ranged from 760 to 21,967 ng/ml and occurred 0.8 to 6.9 h after Cortisol administration depending on the time of the first urination after administration. The return to values below 100 ng/ml was observed after 21 h in all horses. The 1000 ng/ml threshold for Cortisol control in urine after i.v. Cortisol (1 mg/kg) is specific (conservative) but of low sensitivity.
Heart rate and lactate concentration during two different cross country events
Authors: WHITE SUSAN L. , WILLIAMSON LISA H. , MAYKUTH PATRICIA , COLE S. , ANDREWS F.
Published: June 2010

The exercise intensity of horses competing in the cross country phase of an advanced horse trial (Group 1; n=17) and an advanced 3‐day combined training event (Group 2; n=7) over a similar course on the same day was investigated. Environmental conditions during the trial were cool. Heart rates were continuously recorded at 5 s intervals by a heart rate monitor. Mean ± s.d. heart rates for Group 1 and Group 2 were 167.7 ± 24.0 beats/min and 171.4 ± 19.2 beats/min, respectively, (P>0.05). Plasma lactate concentrations were determined at rest, within 60 s post exercise and 10 min post exercise. Mean lactate concentrations were highest immediately post exercise (Group 1=15.18 ± 5.79 mmol/l; Group 2=19.10 ± 4.22 mmol/l) and had declined significantly in 10 min (Group 1=11.15 ± 6.56 mmol/l; Group 2=16.06 ± 6.11 mmol/l). Lactate concentrations were not significantly different between groups at each time period. We concluded that the work effort for the cross country phase was not different between advanced horse trial and 3‐day competitions for horses competing under similar conditions during non stressful environmental conditions.
Pulmonary capillary pressure in horses undergoing alteration of pleural pressure by imposition of various upper airway resistive loads
Authors: DUCHARME N. G. , HACKETT R. P. , GLEED R. D. , AINSWORTH D. M. , ERB H. N. , MITCHELL L. M. , SODERHOLM L. V.
Published: June 2010

We hypothesised that changes in pleural pressure induced by resistive breathing would affect transmural pulmonary artery, pulmonary capillary, and pulmonary wedge pressures. Seven horses were assigned to exercise with each of 4 upper respiratory resistive loads in random order at intervals of at least 2 days: 1) control — no added resistive loads; 2) inspiratory resistive load (Iobst) — left laryngeal hemiplegia; 3) expiratory resistive load (Eobst) — one‐way valve in the right nostril; and 4) combined inspiratory and expiratory resistive loads (CIEobst) — left nostril occlusion. On each occasion, the horses performed an incremental exercise protocol consisting of exercise episodes of 3 min duration at 75, 90, and 100% of maximal heart rate (HRmax). Pulmonary artery and oesophageal pressures were recorded continuously. Subsequent analysis was carried out on the pulmonary arterial pressure signal with the oesophageal pressure signal subtracted, hence the pulmonary vascular pressures in this paper approximate transmural pressures. Pulmonary vascular pressures, heart rate, and arterial blood gas tensions were measured at each level of exercise. Pulmonary capillary and pulmonary wedge pressures were determined from the pulmonary artery waveform after dynamic occlusion of a branch of the pulmonary artery.

During exercise, peak expiratory oesophageal pressure was more positive in horses with Eobstand CIEobst(adjusted means=43, and 39 mmHg, respectively) compared with control (adjusted mean=23 mmHg) (P = 0.0001). Peak inspiratory oesophageal pressure was more negative in horses at exercise with Iobstand CIEobst(adjusted means=‐42 and ‐39 mmHg, respectively) compared with control (adjusted mean=‐26 mmHg)(P = 0.0012). Eobstwas associated with an increase in mean oesophageal pressure while Iobstwas associated with a decrease in mean oesophageal pressure. There were significant increases in mean pulmonary artery pressure in horses with CIEobst(adjusted means = 82 mmHg) and in pulmonary wedge pressure in horses with CIEobstand Iobst(adjusted means=51, and 55 mmHg, respectively) when compared to control (73 and 42 mmHg, respectively) (P = 0.0001). Pulmonary capillary pressure was significantly increased in horses with CIEobstor Iobst(adjusted means=61 mmHg, 63 mmHg, respectively) when compared to control (adjusted mean=50 mmHg)(P = 0.0001). At maximal exercise intensity with inspiratory obstruction, the mean oesophageal (pleural) pressure was ‐17 mmHg while the mean pulmonary capillary pressure was 77 mmHg. The latter exceeds the reported 75 mmHg threshold for capillary failure in horses. We conclude that inspiratory resistive breathing can lead to a significant increase in transmural pulmonary capillary pressure which may contribute to loss of capillary integrity and rupture.
Influence of girth strap tensions on athletic performance of racehorses
Authors: BOWERS J. R. , SLOCOMBE R. F.
Published: June 2010

Eight horses were exercised at speeds to produce 80% of maximal heart rates, on 4 occasions using a randomised block design, and girthed at tensions of approximately 5, 10, 15 or 20 kg using a standard canvas girth attached to a racing saddle. Tension was recorded continuously using an in‐line load cell connected to a physiograph. Horses ran until fatigued on a treadmill inclined at 10% slope. Tensions were measured at peak inhalation (T/inh) and exhalation (T/exh), recorded at rest (rest) and during exercise (ex). Data were analysed by ANOVA and, in addition, least squares linear regression was performed to determine the relationship between distance travelled, time to fatigue and the recorded maximum tensions at inhalation and minimum tensions at exhalation. For T/inhrest, every increase in girth tension by 1 kg was associated with a reduction in distance to fatigue by 98.3 ± 28.6 m and a corresponding reduction in run times of 0.24 ± 0.07 min (P = 0.01).

Results for T/exhrestwere similar, with a reduction of mean ± s.e. 81.3 ± 26.9m and 0.20 ± 0.07 min per 1 kg increase in tension (P = 0.02). The mean distances to fatigue for the T/exhrestof 5, 10, 15 and 20 kg were 6624, 5812, 5268 and 5405 m respectively. These data indicate that distances to fatigue are similar once T/exhrestequals or exceeds 10 kg. Based on this study, resting girth tensions less than 10 kg are optimal for performance, but from our survey data, tensions exceeding this tension are typical for Thoroughbred racing in Victoria.
The effects of training on ventilation and blood gases in exercising Thoroughbreds
Authors: ROBERTS C. A. , MARLIN D. J. , LEKEUX P.
Published: June 2010

The effects of training on ventilation and blood gases during exercise were investigated in 6 clinically normal, detrained Thoroughbred horses. They underwent a 16 week training programme similar to the type frequently used for Thoroughbred racehorses in Great Britain. Standardised treadmill exercise tests (2 min canter at 8 and 10 m/s [C8 and C10] and 2 min gallop at 12 m/s [G12], on a level surface) were performed prior to and after 16 weeks of training. Respiratory flow rates were measured using ultrasound flow transducers. Blood samples were drawn from a transverse facial artery and the right atrium. Minute ventilation, respiratory frequency and tidal volume were not significantly altered by training. Peak inspiratory flow rate was lower following training at 8 and 10 m/s, but not at 12 m/s. Arterial oxygen tension was decreased during trot and canter following training. Blood lactate concentration post G12 decreased following training (10.5 ± 2.2 mmol/l vs. 7.7 ± 2.2 mmol/l; P<.05). The increase in the degree of exercise‐induced arterial hypoxaemia following training may reflect a lack of pulmonary adaptation to training in the face of improved cardiovascular and muscular function.
Functional and compositional changes in pulmonary surfactant in response to exercise
Authors: MORRISON KIRSTEN E. , SLOCOMBE R. F. , McKANE S. A. , DARGAVILLE P. A.
Published: June 2010

Pulmonary surfactant from bronchoalveolar lavages was obtained from 2 groups of horses. A control group consisting of 6 healthy racehorses that were paddock‐rested and lavaged weekly for 6 consecutive weeks were compared with an experimental group of 10 healthy racehorses, lavaged weekly the same period, consisting of a 5 week incremental‐intensity treadmill training programme and one week post training paddock rest. Phospholipid content of lavage fluid was determined indirectly by phosphorus assay, and surfactant functional activity was determined by bubble surfactometry. Total cell counts and differential cell percentages of lavage fluid were adjusted to reflect the dilution of alveolar epithelial lining fluid (ELF) using the lavage/serum urea ratio, and data were analysed per volume of ELF. There was no change in phospholipid content for either group, but some horses had consistently greater amounts than did others, ranging from 17.2–64.4 μg/μl. From the exercised group ELF had both increased nucleated cell numbers due to increased macrophage numbers, and increased numbers of erythrocytes. Surface tension increased significantly over the exercise protocol, but not in controls. Functional activity of surfactant varied between horses, independent of phospholipid content, with average values for individuals ranging 10.5–29.5 mN/m. We conclude that exercise of sufficient intensity to induce intrapulmonary haemorrhage also leads to functional decreases in surfactant activity, without affecting phospholipid content. This study also indicates that functional differences in surfactant exist between horses and may be a risk factor for development of exercise‐induced pulmonary haemorrhage.
Effect of exercise and COPD crisis on isoprostane concentration in plasma and bronchoalveolar lavage fluid in horses
Authors: KIRSCHVINK NATHALIE , ART TATIANA , SMITH NICOLA , LEKEUX P.
Published: June 2010

To test whether isoprostanes could be used as markers of oxidative stress in horses, their concentration was determined in plasma and in pulmonary epithelial lining fluid (PELF) in 3 models of oxidative stress: (1) strenuous exercise, (2) acute COPD crisis and (3) exercise combined with COPD crisis. Four horses were investigated twice, once in crisis and once in remission. The animals underwent a standardised treadmill exercise test. Isoprostane assessment was performed in plasma and bronchoalveolar lavage fluid 24 h before and 1 h after exercise and in plasma also immediately after exercise. Exercise in remission induced a significant increase of isoprostanes in plasma and in PELF. In horses in crisis, the isoprostane concentrations did not increase in plasma, while they did increase in PELF. Lastly, exercise in crisis increased plasma levels of isoprostanes, but did not change PELF isoprostanes. In conclusion, 1) isoprostanes are increased by systemic oxidative stress induced by strenuous exercise in COPD horses in remission either in PELF or in plasma; 2) only PELF and not plasma isoprostanes are increased by pulmonary oxidative stress induced by COPD crisis and 3) unexpectedly, exercise in crisis increased plasma but not PELF isoprostanes.