Sustained strenuous exercise has been shown to produce gastrointestinal disease in athletic species, but the causative factors remain unknown. Since exercise results in oxidative stress and hypercortisolaemia, we tested the hypothesis that oxidative and physiological stress cause gastrointestinal disease in racing Alaskan sled dogs. Dogs from three racing teams were examined before (pre) and immediately after (post) completing a 1770-km sled dog race in approximately 11 days. Serum cortisol and isoprostane concentrations were compared with markers of gastrointestinal barrier integrity and endoscopic evidence of gastric ulceration. Gastric barrier integrity was assessed by measuring the urinary recovery of sucrose and intestinal barrier integrity was assessed using the urinary recovery ratio of lactulose to rhamnose (L/R), administered together by orogastric gavage. Exercise produced a significant increase in median serum cortisol (pre: 1040, 717–2946 pg ml−1 (range); post: 8072, 2228–29 571 pg ml−1; P<0.0001) and L/R recovery ratio (pre: 0.110, 0.060–0.270; post: 0.165, 0.080–0.240; P=0.009) but not isoprostane (pre: 1007, 656–2305 pg ml−1; post: 1164, 23–4710 pg ml−1; P=0.194) concentration. The increased serum cortisol concentration was not correlated with a change in L/R recovery ratio or urine sucrose concentration. Dogs with abnormal gastric endoscopy results (61% of finishers) had higher serum cortisol concentrations than dogs with normal endoscopy results (P=0.0007). We have demonstrated concurrent hypercortisolaemia and gastrointestinal barrier dysfunction with no correlation of the two. Thus, our data do not provide support for the hypothesis that increased serum cortisol concentration causes exercise-induced gastrointestinal disease.

Five male ponies (3–6 years, 208±11 kg) were used to examine the haemodynamic effects of resistance exercise. The experiment consisted of a 30 min catheterization period and a 15 min equilibration period followed by the test. Initially, the ponies stood quietly on a treadmill for collection of 5 min of baseline data. They then walked at 1.9 m s−1 for 1 min sets while carrying 0 kg, 67 kg or 134 kg of weight loaded on the saddle area. Weights were applied in a randomized order using a chain hoist and sling. The ponies rested unloaded for 2 min between sets and all cardiovascular parameters returned to baseline before beginning the next set. Haemodynamic measurements (heart rate (HR), carotid artery systolic (SP), diastolic (DP), pulse (PP) and mean pressure (MAP), right atrial pressure (RAP), right ventricular pressure (RVP) and right ventricular maximum rate of pressure rise (dP/dtmax)) were recorded continuously and data collected during the last 18 s of each set were averaged and analysed. HR increased (P<0.05) with unloaded exercise (201%) and with increases in load (252 and 271% at 67 and 134 kg, respectively). RAP increased (P<0.05) with exercise, with differences (P<0.05) between the response to the 0 kg (66%), 67 kg (121%) and 134 kg (138%) loads. RVP increased (P<0.05) incrementally with load during exercise (58, 110 and 136%, respectively), with differences (P<0.05) between 0 versus 67 kg and 67 versus 134 kg. Right ventricular dP/dtmax increased (P<0.05) incrementally and showed differences (P<0.05) between loads (131, 191 and 252% at 0, 67 and 134 kg, respectively). There were increases (P<0.05) in MAP (20%), SP (20%) and DP (27) with exercise, but no difference (P>0.05) between the response to 67 versus 134 kg load (43 and 51%; 40 and 46%; 49 and 62, respectively). Pulse pressure did not change (P>0.05) from baseline values. These data suggest that resistance exercise in the form of weight carried increases intraventricular pressure through a significant increase in both cardiac pre-load and after-load.

Parathyroid hormone (PTH) has been shown to have anabolic and catabolic effects on the skeleton, and in young racing horses the anabolic effects of PTH on bone might be of great importance in reducing the risk of skeletal injury during race training. The aim of this pilot study was to elucidate the effects of intermittent exogenous application of human parathyroid fragment (hPTH 1-37) on calcium homeostasis and bone turnover in resting horses. Five horses were used in this study. Horses were treated subcutaneously with hPTH (hPTH 1-37, 0.5 μg kg−1 BW) daily at 600 h over a period of 28 days. A foregoing control trial was conducted under the identical test protocol without hPTH application. Blood samples were taken at defined times for the control and hPTH treatment to analyze ionized Ca (Ca++, AVL), total Ca (AAS), inorganic Pi (flame photometry), intact PTH (RIA), osteocalcin (ELISA) and ICTP (carboxyterminal telopeptide of type-I collagen, RIA). Eight hours after hPTH application, blood ionized Ca++ (days 1 and 28) and plasma Pi (days 1–28) increased significantly in comparison to the control. At day 1, 8 h after hPTH application, the decrease in intact plasma PTH was more pronounced after hPTH treatment than in the control, and plasma PTH levels were higher after treatment at day 14 (16 h post-injection, P<0.05), day 18 (16 h post-injection, ns) and day 24 (0 h post-injection). There were no treatment-related differences in total plasma Ca and bone markers. Intermittent PTH administration in healthy horses affected Ca and P homeostasis as well as endogenous PTH secretion, but bone turnover was not affected during the treatment period of 28 days.

The objective of this study was to determine the relationship between insulin sensitivity and aerobic capacity and serum adipocytokine (leptin, adiponectin) concentrations in 14 mature, unconditioned Standardbred horses (eight mares, six geldings). Each horse underwent a euglycaemic–hyperinsulinaemic clamp (EHC) and a frequently sampled intravenous glucose tolerance test (FSIGT) for assessment of insulin sensitivity. Aerobic capacity was determined by measurement of the peak rate of oxygen uptake (V˙O2peak) during an incremental exercise test (IET). Serum leptin and adiponectin concentrations were measured in baseline samples obtained before tests of insulin sensitivity. Mean body weight, condition score, V˙O2peak and run time during the IET did not differ between the sex groups. However, minimal model analysis of the FSIGT showed that insulin sensitivity (SI, ×10−4 l mU−1 min−1) was higher (P = 0.002) in geldings (4.21±0.78) than in mares (2.43±0.95), while the acute insulin response to glucose (AIRg) and glucose utilization independent of insulin (SG) were significantly higher in mares. Similarly, glucose uptake (M) per unit of serum insulin (I) during the EHC (M/I ratio) tended (P = 0.08) to be higher in geldings than in mares (×10−2 mg kg−1 min−1 per μU ml−1: 2.41±0.64 vs. 1.80±0.51). There was no significant relationship between V˙O2peak and measures of insulin sensitivity. Stepwise multiple linear regression modelling determined that sex (65%) and leptin concentrations (13.7%) accounted for 78.7% of the variance in SI, while 46% of the variance in M/I could be attributed to sex. It was concluded that aerobic capacity is not an important determinant of insulin-mediated glucose disposal in mature, untrained Standardbred horses. Further studies are needed to examine the influence of gender on insulin sensitivity in horses.

Despite the increasing use of lasers in the rehabilitation of horses, the biophysical action of the laser is not clearly defined. The purpose of this study was to determine the effect of a defocused CO2 laser on the temperature of the skin, subcutis and fetlock joint in standing and anaesthetized horses. A cross-over design comprising 10 standing horses was used. Consecutive irradiation (91 J cm−2) was applied to each of the three aspects of the front fetlock joint of these animals. In 12 anaesthetized horses (eight laser-treated and four control), irradiation (137 J cm−1) was applied to the dorsal side of the joint. In the standing group, skin temperature increased on average by 5.3°C to 34.8±1.5° (P<0.05) and the subcutis temperature increased by 5.7°C to a mean temperature of 36.0±0.9°C during laser treatment. There was no difference in joint temperature between laser-treated and control horses. Similar results were obtained in anaesthetized horses. Treatment with a defocused CO2 laser caused a significant increase in the temperature of the skin and subcutis, but not in the joint cavity. Further studies are needed to investigate if the increase in temperature influences perfusion and modulation of pain, as a result of defocused CO2 laser treatment.

The objective was to describe and compare the positions of different types of bits within the horse's oral cavity. Eight horses were fitted with a bridle and six bits [jointed snaffle ( JS), Boucher, KK Ultra, Myler snaffle (MylerS), Myler ported barrel (MylerPB), Myler correctional-ported barrel (MylerCPB)]. Lateral radiographs and custom software were used to measure the position and orientation of the bits relative to the horse's palate and second premolar teeth without rein tension and with 25±5 N bilateral rein tension. The results showed differences in the position of the bits within the horse's oral cavity and in their movements in response to rein tension. Without rein tension, single-jointed bits were further from the premolar teeth ( JS 32.2±10.6 mm; Boucher 33.9±10.8 mm) than the Myler bits (MylerS 20.2±9.7 mm; MylerPB 12.8±6.7 mm; MylerCPB 14.6±4.3 mm). Single-jointed bits moved closer to the premolars when tension was applied to the reins (JS 20.8±6.3 mm; Boucher 19.7±6.8 mm). The cannons of the Boucher were more elevated than those of the other bits. The cannon angulation decreased significantly from 38.7±13.7 deg. to 21.6±6.9 deg. for JS and from 43.1±10.1 deg. to 27.8±10.1 deg. for the Boucher when tension was applied to the reins. The Myler bits showed minimal change in position in response to the application of rein tension.

The aim of this study was to determine which oxidant–antioxidant blood markers are of interest for a field exercise test (ET) performed on a racetrack. Healthy Standardbred horses (S: n = 12) and healthy eventing horses (E: n=12) were investigated. Exercise was monitored by measuring velocity (V), heart rate (HR), and plasma lactate (LA). Whilst maximal LA did not differ (11.8±0.88 mmol l−1), maximal V (S: 12.3±0.17 m s−1versus E: 11.1±0.24 m s−1, P<0.05) and final HR (S: 222±1 versus E: 203±8 beats min−1, P<0.05) were significantly different between groups. Venous blood was collected at rest (R) prior to ET and the following oxidant–antioxidant markers were determined: uric acid (UA), ascorbic acid (AA), α-tocopherol (Vit E), vitamin A (Vit A), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione (reduced: GSH and oxidized: GSSG), glutathione redox ratio (GRR), copper (Cu), zinc (Zn) and selenium (Se), oxidized proteins (Protox), lipid peroxides (Pool), antioxidant capacity of water-soluble components (ACW) and antioxidant capacity of lipid-soluble components (ACL). The following markers were further determined 15 min (E15) after the ET: UA, ACW, AA, GSH, Protox, Pool, ACL. Standardbreds had significantly higher concentrations of ACW, GSH, ACL and Protox, whilst Se, Zn and SOD were significantly lower than in eventing horses. Exercise induced a significant increase in ACW and UA. GSH decreased in eventing horses and Pool significantly decreased in both horse groups. This study describes a field ET of high intensity for Standardbred and eventing horses, which could be performed by all animals tested. By sampling blood at rest and at E15, changes of the hydrophilic antioxidant defence were partially assessed, whereas no interpretable changes of the lipophilic antioxidants and of oxidation markers (Protox, Pool) could be detected.

The present study used the physicochemical approach to characterize the changes in acid–base status that occur in Standardbred racehorses during recovery from high-intensity exercise. Jugular venous blood was sampled from nine Standardbreds in racing condition, at rest and for 2 h following a high-intensity training workout. Plasma [H+] increased from 39.1±1.0 neq l−1 at rest to 44.8±2.7 neq l−1 at 1 min of recovery. A decreased strong ion difference ([SID]) was the primary contributor to the increased [H+] immediately at the end of exercise, while increased plasma weak ion concentration ([Atot]) was a minor contributor to the acidosis. A decreased partial pressure of carbon dioxide (PCO2) at 1 min of recovery had a slight alkalinizing effect. The decreased [SID] at 1 min of recovery was a result of a 15.1±3.1 meq l−1 increase in [lactate−], as [Na+] and [K+] were also increased by 6.5±0.7 and 1.14±0.06 meq l−1, respectively, at 1 min of recovery. It is concluded that high-intensity exercise and recovery is associated with significant changes in acid–base balance, and that full recovery of many parameters that determine acid–base status requires 60–120 min.

A pilot study was performed using a strain gauge transducer intercalated between the bit and the left rein to measure rein tension dynamically during riding. The strain patterns consisted of a series of spikes with frequencies corresponding to two per stride in walk and trot and one per stride in canter. The highest tension recorded in each gait was 43 N at walk, 51 N at trot and 104 N in canter. Based on the results of this study, it is recommended that the methodology should be adapted so that both reins are instrumented simultaneously, data are transmitted telemetrically to eliminate the need for a tether connecting the horse to the computer, and kinematic data are synchronized with the rein tension recordings.

The aim of the present study was to quantify the inter-day reliability of force platform data from horses at the trot. The subjects were ten horses judged to be sound on the basis of clinical evaluation and similarity of ground reaction force peaks of left and right limbs. The same handler trotted horses in hand for four consecutive days over a force platform at their natural and comfortable velocity between 2.70 and 3.60 m s−1. For each horse, velocity was controlled in a range of±0.15 m s−1. Five contacts per limb were recorded on each day. Custom-written code in MATLAB was used to smooth the data and time-normalize to 101 data points. The agreement boundary was used to determine the reliability of seven force variables. Stance duration, peak vertical force and vertical impulse were the most reliable variables (<10% variability in the mean), while peak braking and propulsive forces and impulses had larger variation across the three days (>20% variability in the mean). Variables with low variability may require fewer animals, trials and days to obtain accurate data while maintaining adequate statistical power. These results may act both as a reference when studying variability in lame horses and as a guide for planning future equine kinetic studies.

The aim of this study was to examine the influence of an experienced rider and a novice rider on the stride kinematics of experienced riding horses. SVHS video recordings (50 Hz) were made of ten experienced riding horses jumping a 1.05 m-high vertical fence. The horses were randomly assigned to jump the fence under two experimental conditions: ridden by an experienced rider and ridden by a novice rider. Three trials for each ridden condition were analysed, and the effects of the rider type on four kinematic variables were examined using a repeated measures ANOVA. No significant differences were found between the riders for velocity and stride length during the approach, or for the take-off and landing distances from the fence. The results suggest that the rider's body position and body movement had no effect on the horse's jumping kinematics as measured in this study, and that each horse jumped the fence in its own manner, regardless of what the rider was doing. This is contrary to the current belief that a horse's jumping technique is strongly influenced by the rider. These findings have relevance for both horses and riders, in that if an experienced horse does not respond to a rider's instructions as expected, then the implications for training of the horse and the rider are considerable.

Repeated strenuous exercise while breathing cold air is believed to induce chronic airway inflammation and hyperreactivity, a condition referred to in humans as ‘ski asthma’. However, the time course of development and resolution of ski asthma is unknown. We have previously shown that multi-day aerobic exercise induces airway inflammation and hyperreactivity in racing sled dogs. In the present study, a similar group of subjects was examined at multiple times during training to test the hypothesis that ski asthma spontaneously resolves during seasonal detraining, but is re-induced during training in the cold weather. At the beginning of training, bronchoalveolar lavage fluid (BALF) from detrained elite sled dogs (n = 16) had higher concentrations of lymphocytes (median 53.63 vs. 8.30 cells μl−1) and neutrophils (median 23.03 vs. 1.10 cells μl−1) compared with normal laboratory dogs (n = 5). However, there was no significant effect of training on BALF nucleated cell concentrations from exercised sled dogs (n = 11) compared with sedentary sled dogs (n = 8). In contrast to our hypothesis, our data support the contention that cold weather exercise-induced airway inflammation can persist through seasonal detraining, but that routine training does not cause significant worsening of the condition.