The aims of this study were to determine whether the equine distal phalanx changes in shape in response to exercise and to relate any osseous changes to those in the hoof capsule. Eighteen mature Standardbred horses were randomly divided into exercise and control groups. Exercised horses were jogged on a straight track at individual mean speeds between 4 and 8 m s− 1 for 10–45 min, 4 days per week for 16 weeks. Both groups were similarly shod and pastured on the same field. Before and after the training period, each horse had digital photographs and magnetic resonance images (MRI) made of the right forehoof. Five linear measurements of the distal phalanx were recorded from the MRI and 24 measurements of the hoof capsule were made on the digital photographs. Small but significant changes in bone width (P = 0.039) were found in the controls and in two sagittal measurements of bone length (P = 0.039, 0.001, respectively) for the exercise group. These changes were slight and did not correlate with changes in shape of the hoof capsule, suggesting that the bone acts as a stable platform for supporting the capsule and withstanding loads.

Because athletic horses become hypoxaemic and hypercapnoeic during high-intensity exercise but ponies do not, six Thoroughbred horses and five ponies performed an incremental exercise test at speeds with calculated energy requirements that were 40, 60, 80 and 115% of V˙O2max, with the objective of comparing their blood gas and ventilatory responses to exercise. Expired gas and blood samples were taken and breathing mechanics were assessed before exercise and during the last 15 s at each intensity. Maximal V˙O2 and V˙CO2 in horses were 153±5 (SEM) and 187±4 ml kg−1 min−1, respectively, while corresponding values in ponies were 92±4 and 112±7 ml kg−1 min−1. During heavy and supramaximal exercise, horses, but not ponies, became hypoxaemic and hypercapnic. There was no significant difference for V˙E kg−1 between groups during maximal exercise, but PAO2, PaO2 and PvO2 were lower and PaCO2 and [(A−a)O2D] were greater in horses than in ponies. Additionally, the horses' maximal transpulmonary pressure difference was higher and their total pulmonary resistance and ventilatory equivalent lower than in ponies. Flow-volume loops suggested that horses experienced expiratory flow limitation but that ponies did not. These results indicated that horses like Thoroughbreds appear to be expiratory flow-limited and become hypoxaemic and hypercapnic when the demand for gas exchange associated with their high V˙O2max and V˙CO2max is greater than can be met by their ventilatory system. Ponies, which are less capable athletes, could better match their ventilatory response with their metabolic capabilities and so were able to maintain PaO2 in the pre-exercise range and decrease PaCO2 to a tension that was more compatible with acid–base homeostasis.

It has been suggested that the presence of a bit reflexly increases salivation but, at the same time, interferes with the horse's ability to swallow. The objective of this study was to compare swallowing frequency in 12 horses exercising at canter while wearing a head collar, a bitless bridle, a jointed snaffle bit and a Myler correctional-ported barrel bit. Laryngeal movements were recorded videoendoscopically as the horses cantered (8 m s−1) on a high speed treadmill, with the use of side reins to flex the poll. Swallowing was stimulated artificially by infusion of sterile water at a constant rate of 5 ml min−1 through a cannula in the endoscope's biopsy port. The results showed large differences in swallowing frequency between horses. Swallowing frequency was lower for the Myler snaffle than for the other conditions (P<0.05). It is concluded that the presence of a bit does not preclude swallowing during exercise at canter with the poll in a flexed position, but certain types of bits may be associated with a reduction in swallowing frequency.

In human and animal nutrition, much interest has been focused on the potential role of dietary supplements in promoting health, athletic performance and disease mitigation. Supplements may include essential nutrients provided in amounts greater than required to prevent a deficiency state, or substances purported to have a role in metabolism or tissue function but that are not recognized as an essential nutrient. This review aims to provide the rationale and scientific evidence for use (or not) of some of the supplements marketed for use in horses, with emphasis on supplements purported to directly boost performance, such as creatine, carnitine and branched-chain amino acids. It also discusses the so-called ‘joint supplements’ (or slow-acting, disease-modifying osteoarthritis agents), such as glucosamine and chondroitin sulphate. The effects of selected feeding strategies on performance, including fat supplementation, are also examined. It is concluded that although the use of nutritional supplements is commonly alleged to boost performance or health in horses, for most, if not all, of these supplements there is little or no scientific evidence of efficacy.

This study used a randomized crossover design, with investigators blind to the treatment given, to test the hypothesis that seven commercially available electrolyte supplements would alter plasma concentrations of Na+, K+, Cl−, lactate, total protein (TP) and total carbon dioxide (tCO2) as well as plasma strong ion difference (SID) and haematocrit (HCT). Ten unfit Standardbred mares (∼450 kg, 4–9 years) completed a series of simulated race exercise tests (SRT) during which venous blood was collected at five sampling intervals (prior to receiving electrolyte treatment, prior to the SRT, immediately following exercise and at 60 and 90 min post-SRT). Plasma electrolyte and tCO2 concentrations were measured in duplicate using a Beckman EL-ISE electrolyte analyser. No difference (P>0.05) between treatments was detected at any of the five sampling intervals for plasma [Na+], [K+], [Cl−] or [tCO2]. Similarly, no significant difference was detected between treatments across each of the five sampling intervals for plasma SID, HCT or TP concentration. There were differences (P<0.05) in plasma [Na+], [K+] and [tCO2] (as well as plasma SID, HCT, and TP concentration) in the immediately post-SRT samples that were attributable to the physiological pressures associated with acute exercise. No differences (P>0.05) were detected between treatments across the pre-electrolyte and pre-SRT sampling intervals for plasma lactate concentration. There was, however, a significant time by treatment interaction during the 0, 60 and 90 min post-SRT sampling intervals for this parameter. The electrolyte supplements featured in this investigation did not affect either plasma tCO2 concentration or SID; however, this result does not rule out the potential for other supplements, especially those containing alkalinizing ingredients, to exert an effect that could push a horse towards threshold values.

The purpose of the present study was to determine the time course and magnitude of changes in extracellular and intracellular fluid volumes in relation to changes in total body water during prolonged submaximal exercise and recovery in horses. Seven horses were physically conditioned over a 2-month period and trained to trot on a treadmill. Total body water (TBW), extracellular fluid volume (ECFV) and plasma volume (PV) were measured at rest using indicator dilution techniques (D2O, thiocyanate and Evans Blue, respectively). Changes in TBW were assessed from measures of body mass, and changes in PV and ECFV were calculated from changes in plasma protein concentration. Horses exercised by trotting on a treadmill for 75–120 min incurred a 4.2% decrease in TBW. During exercise, the entire decrease in TBW (mean±standard error: 12.8±2.0 l at end of exercise) could be attributed to the decrease in ECFV (12.0±2.4 l at end of exercise), such that there was no change in intracellular fluid volume (ICFV; 0.9±2.4 l at end of exercise). PV decreased from 22.0±0.5 l at rest to 19.8±0.3 l at end of exercise and remained depressed (18–19 l) during the first 2 h of recovery. Recovery of fluid volumes after exercise was slow, and characterized by a further transient loss of ECFV (first 30 min of recovery) and a sustained increase in ICFV (between 0.5 and 3.5 h of recovery). Recovery of fluid volumes was complete by 13 h post exercise. It is concluded that prolonged submaximal exercise in horses favours net loss of fluid from the extracellular fluid compartment.

Exercise is associated with an increase in the production of oxidants that may be instrumental in the development of exertional rhabdomyolysis. We speculated that participation in a long-distance sled race would alter antioxidant capacity of dogs, in conjunction with increases in indices of rhabdomyolysis. The objective was to determine the effect of participation in a long-distance sled dog race on antioxidant capacity and plasma creatine kinase (CK) activity in sled dogs. This was a prospective, longitudinal study on a convenience sample of 57 Alaskan sled dogs participating in a 1600 km sled dog race. Blood samples were collected before racing (31 dogs) and after racing (39 dogs) for measurement of plasma vitamin E concentration; CK, aspartate aminotransferase (AST) and caeruloplasmin (CER) activity; and red-blood-cell (RBC) glutathione peroxidase (GPX) and superoxide dismutase (SOD) activity. CER and GPX activities after the race were 26% and 14% lower, respectively, than before racing whereas CK and AST were 300% and 170% greater. There was no change in plasma vitamin E concentration or RBC SOD activity. We conclude that completion of a long-distance sled dog race involving prolonged and repeated submaximal exercise results in a reduction in enzymatic antioxidant activity in the blood of sled dogs.

The present study used the physicochemical approach to characterize the changes in plasma electrolyte and acid–base states that occur in horses in response to feeding. Jugular venous blood was sampled every 0.5–2 h over a 24-h period from two groups (n = 4 and n = 5) of Standardbreds fed a mixed hay and grain ration at 8 am and 7 pm. One group of horses was studied in October, and one in December. The time course and magnitude of feeding responses differed between groups, and between the morning and evening meals. Feeding-induced changes in plasma electrolyte and acid–base variables occurred rapidly, within the first 1–3 h of meal consumption. The plasma acidosis associated with eating the meal was marked by increased plasma [H+] and decreased TCO2. The primary contributors to the increases in plasma [H+] were the decrease in the plasma concentration of strong ions ([SID]) and the pCO2. The increase in plasma total weak acid (protein) concentration ([Atot]) post-feeding had only a minor effect on the acid–base state. The feeding-induced acidosis abated 3–6 h after the meal, showing cyclical recovery of physicochemical variables that contributed to the acid–base disturbance. It is concluded that several key plasma electrolyte and acid–base parameters undergo significant, cyclical fluctuations in response to feeding in horses.

This study examined the effects of a rider on the angular momentum and angular velocity of the jumping horse, particularly during the flight phase. Sagittal plane video recordings were digitized of eight horses jumping a vertical fence (1 m high) under two conditions: Loose and Ridden. An experienced rider rode the horses during the Ridden condition. Using appropriate segmental inertial data for the horse and rider, angular momentum and angular velocity were calculated for the Loose and Ridden conditions. Estimates of the various rider effects on angular momentum and angular velocity were obtained by comparison of Loose and Ridden conditions and examination of the contributions of the horse and rider segments to the total angular momentum. The results showed that the rider's effect on angular momentum was significant but that the rider's segmental contribution to the angular momentum of the horse–rider system was minimal. Repeated-measures ANOVA revealed that the rider had a significant effect on the angular momentum and angular velocity of the horse during the flight phase (P<0.01). However, the rider did not have a significant effect on the transfer of angular momentum during the flight. We concluded that the rider's instruction has a greater influence on the horse's motion than the mechanical transfer between rider and horse.

The objective was to compare vitamin E content in the total diet of Arabian horses competing in the 80 km Research Ride 2002 to the oxidative stress and antioxidant measures throughout the race. Prior to the race, riders completed a detailed nutritional survey, which was used to calculate vitamin E intake. Blood samples, temperature and heart rate were taken the day before the race, at 27 and 48 km during the race, at race completion or elimination and 3 h after race completion. Plasma lipid hydroperoxides, α-tocopherol (TOC), creatine kinase (CK), aspartate aminotransferase (AST), albumin, red and white blood cell total glutathione and glutathione peroxidase were measured. Data were analyzed by Pearson's correlation in SAS. From the survey, it was estimated that horses consumed 2265±114 IU day−1 of vitamin E. A negative correlation was found between the vitamin E intake and CK (r = −0.23; P = 0.002), and AST (r = −0.22; P = 0.003). A positive correlation was found between the vitamin E intake and plasma TOC (r = 0.15; P = 0.005) at all sample times. This suggests that intensely exercising horses supplemented with vitamin E may not have an improved welfare and performance if they are supplemented vitamin E versus what is naturally found in forages and commercial feeds.

Classic descriptions of rib motion during ventilation include three-dimensional movements that are tied to the locomotor pattern. It is still not clear how chest wall and diaphragmatic movements contribute to ventilation. The purpose of this paper was to evaluate how gait affects local thoracic geometry in horses. Hemispherical markers were placed on the skin over the ribs and spine to calculate thoracic hemi-diameter. Ventilatory airflows were recorded using an ultrasonic flowmeter system. Airflow and kinematic data were collected synchronously at walk (1.8 m s-1), trot (4 m s-1), canter and gallop (6, 8 and 10 m s-1) on the treadmill. At walk and trot, the changes in right and left hemi-diameter were approximately symmetric. At walk, mean hemi-diameter changes were 40 mm (rib 10) and 47 mm (rib 16). At trot, they were 33 mm (rib 10) and 34 mm (rib 16). Across the three canter and gallop speeds, leading (right) side hemi-diameter change increased from 25 to 30 to 35 mm (rib 10) and from 23 to 37 to 46 mm (rib 16). The trailing (left) side hemi-diameter increased from 50 to 67 to 70 mm (rib 10) and from 36 to 48 to 54 mm (rib 16) (P≪0.01). At canter and gallop, the non-lead side of the thorax is subjected to larger amplitude changes in hemi-diameter than the lead side, which tends to be more compressed overall and demonstrates smaller amplitudes of change in diameter.

The present study used the physicochemical approach to characterize the changes in acid–base status that occur in Standardbreds after post-exercise electrolyte supplementation. Jugular venous blood was sampled from six conditioned Standardbreds on two separate occasions, at rest and for 24 h following a competitive exercise test (CET) designed to simulate the speed and endurance test of a 3-day event. After the CETs, horses were given water ad libitum and either a hypotonic commercial electrolyte solution, via nasogastric tube followed by a typical hay/grain meal, or a hay/grain meal alone. The electrolyte supplementation resulted in c. 2 mmol l− 1 decreased plasma [TCO2] during the recovery period as compared with control. The primary contributor to the decreased [TCO2] with electrolyte supplementation was a decreased strong ion difference ([SID]), as a result of the non-significant increase in plasma [Cl− ]. Additionally, electrolyte supplementation resulted in faster restoration of hydration status compared with control, as evidenced by faster recovery of plasma [protein] and total weak acid concentration ([Atot]). It is concluded that oral administration of a hypotonic electrolyte solution after prolonged moderate-intensity exercise diminishes the post-exercise alkalosis, and that recovery of hydration status is still incomplete 24 h after exercise when no electrolytes are given. Thus, supplementation with electrolytes according to estimated sweat losses may attenuate post-exercise increases in plasma [TCO2], which is of significant practical interest to the horse racing community, as a testing threshold of greater than 37 mmol l− 1 is used by many racing jurisdictions to determine whether a horse has been administered an alkalinizing agent.

The aim of this study was to identify the effect of training stage, height of the obstacle and successive number of jump on young stallions' linear jumping parameters with and without rider. Investigations were based on filming of free jumping and jumping with rider during regular stallion work on the 11-month performance test. Horses jumped through the spread obstacle (doublebarre) with constant width of 90 cm and heights of 100, 110 and 120 cm. Taking-off distance, landing distance, heights of legs above obstacle and bascule of horse silhouette were measured using manual programme for video image analysis. Almost all parameters measured with and without rider were training dependent. The only parameters not affected by training were heights of hind limbs above obstacle, which were also not affected by height of obstacle in observations of more trained horses by free jumping and less trained horses with rider. Jumping parameters were not influenced by successive number of the jump by all parameters with rider and parameters of length of the jump in free jumping. On the basis of received results, it could be concluded that evaluation of jumping skills in free jumping and jumping with rider should be based on different criteria.

Routine study of three-dimensional (3D) tarsal kinematics is hampered by errors due to the displacement of skin surface-tracking markers relative to the underlying bones. Reliable kinematics can be obtained with bone-fixed markers, but an accurate, non-invasive method would have more applications. Simultaneous kinematic data from skin-based and bone-fixed markers attached to the tibia and third metatarsus were collected from three trotting subjects. The motion of the skin-based markers was extracted relative to the underlying bone motion tracked using the bone-fixed markers. The 3D skin displacement patterns for the skin-based markers were parameterized using a truncated Fourier series model. These displacements were expressed in terms of the local coordinate system for each bone. Skin displacement artefacts were observed in all three axes of each bone segment, with the largest displacements occurring at the proximal tibia. The mean skin displacement amplitudes in the tibia were 6.7%, 3.2% and 10.5% of segment length, and for the third metatarsus were 2.6%, 1.4% and 3.8% of segment length, for the craniocaudal, mediolateral and longitudinal segment axes, respectively. Skin displacement patterns could be expressed concisely using the Fourier series model. Displacements were also consistent between subjects, which should allow them to be used as a basis for developing a correction procedure for 3D tarsal joint kinematics.

The exercise performed by Thoroughbred (TB) and Standardbred (SB) racehorses is similar. Nevertheless, warm-up regimes seem to differ between trainers of the two breeds. The aim of this study was to collect some preliminary results on warm-up strategies used by trainers of SB and TB in Sweden and the physiological response to two warm-up regimes of practical relevance. A questionnaire was answered by eight and nine SB and TB trainers, respectively, and showed that the SB trainers tended to perform longer warm-ups than TB trainers. In the exercise study, a long and a short warm-up (LWU and SWU) were designed by two trainers (SB and TB, respectively) and performed prior to an intensive exercise session. The study showed that the recovery period in the LWU trial in SBs was prolonged compared with the SWU trial and associated with increased body temperature (39.6±0.3 versus 39.1±0.1°C 15 min post-exercise), heart rate, and breathing frequency (66±10 versus 55±6 beats min−1 and 86±11 versus 56±6 breaths min−1 15 min post-exercise). In addition, the body weight loss was increased by 129% compared with the SWU. In the TB trial, the post-exercise breathing frequency was higher following SWU compared with LWU (97±7 versus 71±8 breaths min−1 15 min post-exercise), indicating increased anaerobic metabolism. Although this study involves few animals, it indicated that the LWU for TBs and the SWU for SBs was most beneficial.

Lameness manifests itself during the movement of the animal or at rest, indicating a structural or functional disturbance in one or more limbs. Videographic analyses allow the qualitative and quantitative investigation of the movement, reducing the subjectivity of evaluations. The objective was to record the alterations in the movement of the head and limbs of horses in a lame and non-lame condition. Video cameras (60 Hz) and computational methods were used. Six Purebred Arabian colts were filmed on a treadmill, at walk and at trot, before and after induction of lameness. Lameness was induced in the left forelimb utilizing a transient lameness model. Markers were placed on the zygomatic process of the temporal bone, spiny process of the sixth thoracic and first lumbar vertebrae and on the proximal phalange. Nine strides were analysed. At walk and at trot, the animals demonstrated two vertical head movements per stride, while after induction of lameness only one head movement was observed per stride, where this movement was of greater amplitude. The head was shown to be in a more elevated position when the lame limb made first contact with the treadmill belt, which was not observed in the case of the healthy limbs. Only with trotting did the lame animals manifest a prolonged duration of the stance phase for all limbs. The lame animals had a longer support time, lifted the non-lame limbs and showed a shorter stride. Videographic analyses offered details of the alterations in the movement of horses, which are important in the diagnosis of lameness.

Subjective bias by judges within the dressage phase of eventing competition is problematic if correct evaluation of horse and rider performance is to be undertaken. The present study examines dressage penalty scoring (penalty scores are awarded for completion of a pre-set series of dressage movements) within a population of novice event horses (n = 2471). Between May and June 2003, 22 novice events within the UK were analysed, and at each event up to six competitions or sections (at the same competitive level) were run. The whole population data structure was normal in distribution, Pearson's skewness 0.314 (Kolmogorov–Smirnov Z = 1.855, P>0.05 from zero) and kurtosis at 0.425. The mean score recorded for the whole population was 37.82 penalty points (standard deviation = 5.65 and standard error = 0.11). A number of effects were observed within the population. Between-events effects were observed in three of the 22 events studied (P<0.01). Of those events running three or more sections (n = 16), within-event effects were observed for 10 events as differences (P<0.01) in mean scoring patterns between sections. All events running two sections (n = 4) were observed to exhibit differences (P<0.02) in mean scores. Differences (P>0.01) between the dressage test used at events were determined using post hoc Bonferroni tests. However, these differences were not found to have a confounding effect on the between-event observations. The study indicates that additional methodologies need to be implemented to ensure that accurate and impartial evaluation of event horses is conducted.

The aim of this study was to investigate the effect of feeding frequency on total tract digestibility and plasma glucose, insulin, urea, gastrin and cortisol concentrations at rest and following exercise in seven Standardbred horses in race training. The horses were fed every 12 h (twice a day, 2TD) and every 4 h (six times a day, 6TD) for 25 days, in a cross-over design. The diet (64% grass hay, 36% concentrates on weight basis) was fed at twice the maintenance energy requirement. Blood samples were taken every hour for 24 h on day 17, total collection of urine and faeces was made on days 19–21 and an intensive exercise test was performed on day 25. Altering feeding frequency caused small variations in diurnal plasma glucose, urea, gastrin and cortisol concentrations and did not affect total tract nutrient digestibility. There was an increase in the mean diurnal plasma urea concentration on the 2TD regime and low levels of plasma insulin were observed 7 h after feeding 2TD. The response to intensive exercise on heart rate, plasma lactate and plasma glucose was similar on both treatments but the plasma insulin concentration was higher following exercise in the 2TD regime, indicating that post-exercise glucose metabolism was altered. In conclusion, this study shows that feeding athletic horses only 2TD caused metabolic signs resembling those observed during feed deprivation (low levels of plasma insulin and an increased diurnal plasma urea concentration) and an altered post-exercise glucose metabolism, but did not affect the digestive response.

The purpose of this study was to demonstrate whether acute vascular occlusion was safe and if it would result in changes to limb muscle size in horses. Six healthy, unfit Standardbred mares were used. Horses (standing at rest) wore an occlusion cuff at the most proximal position of the left forelimb. The right forelimb was used as control. An occlusion pressure of 200 mmHg was set for 5 min followed by a 2 min recovery. Three sets of occlusions were given to each horse. Muscle thickness was measured using B-mode ultrasound. The circumference of the forelimb and first phalanx was measured using a flexible tape measure. Pulsed-wave Doppler was performed on the radialis artery with a 5–10 MHz mechanical transducer at baseline and at each occlusion. Peak flow velocity (PFV) and the flow velocity integral (FVI) were measured each time. Mid-forelimb, but not first phalanx, girth was increased (P<0.05) in the occluded but not in the control leg following occlusion. Extensor and flexor muscle thickness was increased (P<0.05) in the occluded but not in the control leg. There were no changes (P>0.05) in PFV or FVI at any measurement time point. Acute vascular occlusion may be a suitable and safe model for studying muscle hypertrophy in horses.

Kinematic studies of western pleasure horses are limited and were performed before current changes in the stock breed association judging standards on the western pleasure gaits. The objective was to measure the kinematics of the jog and lope of the stock breed western pleasure horse. Reflective markers attached along palpation points of the joint centres of the left forelimb and hind limb of four stock breed western pleasure horses were tracked for five strides for each gait for each horse. Both the jog and lope were determined to be four-beat stepping gaits. During the jogging stance, the elbow (159.7 ± 6.6°), carpal (179.9 ± 1.1°), fore (227.6 ± 2.7°) and hind fetlocks (227.4 ± 6.9°), stifle (159.5 ± 6.5°) and tarsal (166.5 ± 6.5°) joints demonstrated peak extension. The same joints demonstrated during swing peak flexion with the hind fetlock joint having double peaks of flexion (195.7 ± 3.2°, 182.3 ± 2.1°). During loping stance, the elbow (153.4 ± 4.2°), carpal (179.7+0.4°), and fore (228.3 ± 9.7°, 229.8 ± 10.0°) and hind fetlock (232.1 ± 2.6°) joints of the leading limbs demonstrated peak extension with tarsal peak extension (157.0 ± 9.6°) occurring at lift-off. Peak flexion occurred during swing for the elbow (105.1 ± 3.1°), carpus (119.8 ± 6.1°), hip (83.5 ± 5.4°), stifle (129.8 ± 9.6°) and tarsus (127.5 ± 6.1°). Kinematic measurements will assist in objectively defining the stock breed western pleasure gaits.