The Effect of Different Physical Exercise on Plasma Leptin,Cortisol, and Some Energetic Parameters Concentrations in Purebred Arabian Horses

Leptin is a hormone that coordinates food intake, energy expenditure, and metabolic rate; it is, however, unknown how exercise influences plasma leptin concentration in horses. The aim of the study was to evaluate the exercise-induced changes in plasma leptin concentration in purebred Arabian horses competing in races and endurance rides. A total number of 26 horses (12 purebred Arabian racehorses aged 3–5 years and 14 endurance horses aged 7–14 years) were studied during performing routine physical exercise. From each horse, blood samples were collected at rest and immediately after the exercise session. Concentrations of plasma leptin, cortisol, lactic acid, uric acid, triacylglycerols, glycerol and free fatty acids were determined. Exercise-induced increase in cortisol and free fatty acid values were higher in endurance horses than in racehorses. Neither endurance nor race exercises influenced the plasma leptin concentration. Further research is needed to elucidate the effects of different types of exercise on leptin synthesis and secretion in horses.     

Changes in salivary and plasma cortisol levels in Purebred Arabian horses during race training session

Physical activity and stress both cause an increase in cortisol release ratio. The aim of this study was to evaluate the use of saliva samples for the determination of cortisol concentrations indicating the work‐load level in horses during race training. Twelve Purebred Arabian horses aged 3–5 years were studied during the routine training session. After the warm‐up, the horses galloped on the 800 m sand track at a speed of 12.8 m/s. Three saliva samples, and three blood samples were collected from each horse. Both types of samples were taken at rest, immediately after return from the track and after 30 min restitution. The concentrations of blood lactic acid (LA), and cortisol in saliva and plasma samples were measured and analyzed. Blood LA, plasma and salivary cortisol levels increased significantly after exercise (P < 0.05). Salivary cortisol concentration determined 30 min after the exercise correlated significantly with plasma cortisol level obtained immediately after exercise (P < 0.05) as well as measured 30 min after the end of exercise (P < 0.05). The determination of cortisol concentration in saliva samples taken from racehorses 30 min after the end of exercise can be recommended to use in field conditions to estimate the work‐load in racehorses.     

Transendoscopic contact neodymium:yttrium aluminum garnet laser correction of epiglottic entrapment in standing horses

Fifty-seven Standardbred and 44 Thoroughbred racehorses and 1 Thoroughbred polo mare with primary clinical signs of exercise intolerance or respiratory tract noise or combined exercise intolerance and respiratory tract noise were referred for laser correction of epiglottic entrapment. Significantly (P less than 0.001) more Standardbred than Thoroughbred racehorses were affected, compared with the observed hospital population during the same period. At referral, 14 horses did not have evident epiglottic entrapment and were returned to exercise without development of entrapment after treatment, which consisted of 1 week of rest and administration of anti-inflammatory medication. In 88 standing horses under sedation and topical anesthesia, epiglottic entrapment was corrected transendoscopically by use of a contact neodymium:yttrium aluminum garnet laser. In these 88 horses, 98% of entrapments were persistent, 92% were thick, 97% were wide, and 45% were ulcerated. Thirty-one percent of the horses had endoscopic evidence of epiglottic hypoplasia, and 8% had deviated epiglottic axis. Complete correction was achieved in 97% of the horses, Persistent dorsal displacement of the soft palate in 1 horse and severe epiglottic hypoplasia with thick, chronic entrapping membranes in 2 horses precluded successful transendoscopic correction with the horses in standing position. Most horses were treated on an outpatient basis, and all were able to be returned to exercise after 7 to 14 days of rest and treatment with anti-inflammatory medication. Entrapment recurred in 4 horses (5%), 3 of which had hypoplastic epiglottis. Dorsal displacement of the soft palate developed after surgery in 9 horses (10%) and continued in 4 horses (5%) that had displaced soft palate before surgery. All these horses had epiglottic hypoplasia. Laser correction of epiglottic entrapment in standing horses was safe, well tolerated, and effective. Laser surgery was an alternative to conventional surgery, and eliminated the need for general anesthesia and laryngotomy. It also reduced convalescence and postoperative complications.     

Is There an Ideal Rest Interval Between Races During Vaquejada in Which It Would Be Possible to Associate Best Performance and Welfare?

Vaquejada is an important Brazilian equine discipline. Understanding physiological adaptations of these athletes is crucial to improve properly performance, guaranteeing welfare. The objective of this study was to evaluate the influence of three vaquejada simulation tests (VST) on physiological parameters of horses and standardize a possible rest interval between races. Ten clinically healthy Quarter horses, 8.9 ± 4.3 year-old and 441.3 ± 25.0 kg, executed three VST, 5 days apart from each other. Vaquejada simulation tests consisted of two horses, a puller, and a helper, running with a bull on a soft sand track in which they must put the bull down. On M1, they ran three times with a 5-min rest between races; on M2, with a 10-min rest; and M3, with a 15-min rest. Clinical evaluation and blood sampling were made in all VST, before (T0), immediately after first run (T1), second run (T2), third run (T3) and at 30 minutes (T4), and 4 hours (T5) of recovery. Variables were statistically analyzed with a bifactorial comparison (P < .05). Exercise increased heart rate (HR), respiratory rate, body temperature (BT), lactate, triglycerides, packed cell volume, RBC, and hemoglobin concentration, with higher values in pull horses due to a more intense exercise. With 15-min of rest interval, helper horses showed lower values of glucose, aspartate aminotransferase, creatine kinase, BT, and higher values of triglycerides, also working at the same speed and distance with a lower HRmax and HRmed. Pull and helper horses had shown modifications of biomarkers. Furthermore, 15-min rest interval between races improved performance of helper horses as they used properly energy sources and cardiovascular function, respecting precepts of welfare.     

Serum concentration of surfactant protein D in horses with lower airway inflammation

Reasons for performing study: Surfactant protein D (SP‐D), mainly synthesised by alveolar type II cells and nonciliated bronchiolar cells, is one important component of innate pulmonary immunity. In man, circulating concentrations of SP‐D are routinely used as biomarkers for pulmonary injury. To date, serum SP‐D levels have only been investigated in horses in an experimental model of bacterial airway infection. Objectives: To compare serum SP‐D concentrations at rest and after exercise in horses with and without inflammatory airway disease (IAD). Methods: Venous blood samples were collected from 42 Standardbred racehorses at rest and 60 min after performing a standardised treadmill exercise test. Tracheal wash and bronchoalveolar lavage fluid (BALF) samples were collected after exercise. Based on BALF cytology, 22 horses were defined as IAD‐affected and 20 classified as controls. Serum SP‐D concentrations were assessed using a commercially available ELISA kit and statistically compared between groups of horses and sampling times. Results: Serum concentrations of SP‐D in IAD‐affected horses were significantly higher than those of control horses, both at rest and after exercise. Within the IAD‐affected group, no significant correlation was found between serum SP‐D concentrations and BALF cytology. Within each group of horses (IAD and control), no significant influence of exercise was found on serum SP‐D levels. Conclusions: This is the first study determining serum SP‐D concentrations in a noninfectious, naturally occurring form of lower airway inflammation in horses. The results highlight that IAD is associated with a detectable, though moderate, increase of circulating SP‐D levels. Potential relevance: Serum concentration of surfactant protein D could represent a potentially valuable and readily accessible blood biomarker of equine lower airway inflammation.     

Comparison of the effects of fructose and glucose supplementation on metabolic responses in resting and exercising horses

The aim of this study was to compare the effects of two different carbohydrate sources (fructose and glucose) on the metabolic responses in resting and exercising horses. The following regimes were fed in randomized order to five trained horses at rest and immediately before or during exercise. The resting regime comprised 0.6 kg grass meal pellets (control) or 0.6 kg grass meal pellets supplemented with either 50% glucose or 50% fructose. The exercise regime comprised 0.3 kg grass meal (control) or 0.6 kg grass meal pellets supplemented with either 50% glucose or 50% fructose fed immediately before or during simulated endurance exercise on a treadmill (30 km, total running time 120 min; 15 min rest after 60 min running time). Blood samples were collected for the analysis of glucose, insulin, free fatty acids (FFA) and lactate. In resting horses, glucose supplementation resulted in a significantly higher glycaemic and insulinaemic response than the control or fructose feedings (treatment P < 0.05). Plasma glucose levels were significantly higher after glucose supplementation given before or during exercise. Similar plasma glucose concentrations were observed after fructose was fed before exercise, whereas fructose supplementation during exercise resulted in a lower glycaemic response than glucose feeding (P < 0.05). Plasma insulin, FFA and lactate levels showed exercise-related changes (time P < 0.05), but treatment did not effect these results. Plasma glucose concentrations were elevated during the simulated endurance exercise after glucose feeding, and no counter-regulation by insulin occurred. The higher glycaemic response might be beneficial as exogenous glucose can be used as an energetic substrate during prolonged exercise. Fructose exhibited no clear advantages in comparison with glucose as a carbohydrate source for exercising horses.     

Resting concentrations of cardiac troponin I in fit horses and effect of racing

ObjectivesTo determine normal resting values for cardiac troponin I (cTnI) in healthy Standardbred, Thoroughbred and Warmblood horses and investigate if racing has an influence on cTnI concentrations.BackgroundMeasuring cTnI concentrations in plasma is the gold standard for detecting myocardial injury in humans. Cardiac troponin I is highly conserved between species and has gained interest as a marker for cardiac injury in horses. Increased levels of cTnI have been reported in association with endurance and short-term strenuous exercise on a treadmill in horses. However, the effect of true racing conditions has not yet been reported.Animals, materials and methodsBlood samples for analysis of cTnI concentrations in plasma were collected from 67 Standardbred racehorses, 34 Thoroughbred racehorses and 35 Warmblood dressage horses at rest. Blood samples were also collected prior to and after racing in 22 Standardbred racehorses and 6 Thoroughbred racehorses.ResultsAll horses except one had resting plasma cTnI concentrations <0.022 μg/L. Mild increases in cTnI concentrations were seen in some horses 1–2 h after the race (1/17 Standardbreds and 2/6 Thoroughbreds) as well as 10–14 h after the race (4/21 Standardbreds and 1/6 Thoroughbreds).ConclusionsResting cTnI concentrations in horses are low but mildly elevated cTnI concentrations may be detected in some horses 1–14 h after racing. These findings could be of importance when evaluating horses with suspected cardiac disease that recently have performed hard exercise.     

Alterations of fluid and electrolyte balance in thoroughbred racehorses following strenuous exercise during training.

Alterations of acid-base status, and fluid and electrolyte balance subsequent to exercise in Thoroughbred racehorses in North America have not been well-characterized. Des-cribed here are the results of an observational study conducted to characterize changes in fluid and electrolytes following strenuous exercise of 16 Thoroughbreds under routine training conditions. Changes following strenuous exercise were determined for the following variables: serum concentrations of sodium (Na), potassium (K), chloride (Cl) and protein; pH of blood; osmolality of plasma and urine; body weight; and, fractional urinary excretion (FE) of Na, K and Cl. The following changes occurred during exercise: increased concentration of Na in blood; increased FE of Na; decreased concentration of Cl in blood; decreased FE of Cl; increased urinary and plasmal osmolality; weight-loss; decreased pH of blood; and, increased concentration of lactic acid. The concurrent decreased concentration of chloride in plasma and acidemia in these horses differed from the hypochloremic, metabolic alkalosis previously described among endurance horses. Acidemia was attributed to production of lactic acid by anaerobic glycolysis.     

Pharmacokinetics of detomidine administered to horses at rest and after maximal exercise

Reason for performing study: Increased doses of detomidine are required to produce sedation in horses after maximal exercise compared to calm or resting horses. Objectives: To determine if the pharmacokinetics of detomidine in Thoroughbred horses are different when the drug is given during recuperation from a brief period of maximal exercise compared to administration at rest. Methods: Six Thoroughbred horses were preconditioned by exercising them on a treadmill. Each horse ran a simulated race at a treadmill speed that caused it to exercise at 120% of its maximal oxygen consumption. One minute after the end of exercise, horses were treated with detomidine. Each horse was treated with the same dose of detomidine on a second occasion a minimum of 14 days later while standing in a stocks. Samples of heparinised blood were obtained at various time points on both occasions. Plasma detomidine concentrations were determined by liquid chromatographymass spectrometry. The plasma concentration vs. time data were analysed by nonlinear regression analysis. Results: Median back‐extrapolated time zero plasma concentration was significantly lower and median plasma half‐life and median mean residence time were significantly longer when detomidine was administered after exercise compared to administration at rest. Median volume of distribution was significantly higher after exercise but median plasma clearance was not different between the 2 administrations. Conclusions and potential relevance: Detomidine i.v. is more widely distributed when administered to horses immediately after exercise compared to administration at rest resulting in lower peak plasma concentrations and a slower rate of elimination. The dose requirement to produce an equivalent effect may be higher in horses after exercise than in resting horses and less frequent subsequent doses may be required to produce a sustained effect.     

Relationship of plasma lactate production to cortisol release following completion of different types of sporting events in horses

Fifty-eight healthy horses were studied during five sporting events of various intensities and durations, namely show-jumping (n=6), cross-country in a three-day event (n=30), trotting races (n=7), galloping reces (n=7) and endurance rides (n=8). Venous blood samples were collected at rest and immediately after exercise and analysed for plasma cortisol (CORT) and lactate (LA) levels. The experimental procedure was the same throughout the investigation so as to permit a reliable comparison between the five types of exercise. The type of event significantly affected both the resting (p0.05) and the postexercise (p0.01) plasma CORT. The degree of exercise-induced hypercortisolaemia was related to both the intensity and the duration of exercise for all five sporting events, but the endurance ride induced the most and show-jumping the least serious post-exercise CORT changes. LA production was much more closely related to the intensity of the exercise than was CORT. It is concluded that simultaneous measurements of plasma CORT and LA levels may be useful to discriminate between different types of exercise, adjust training programmes, and improve our comprehension of the physiology of sport horses at exercise.Abbreviations CORT cortisol - E/R exercise to rest ratio - EDTA ethylenediaminetetraacetic acid - HR heart rate - LA lactate     

Prolonged suppression of the innate immune system in the horse following an 80 km endurance race

REASONS FOR PERFORMING STUDY: An increased susceptibility to bacterial and viral infections of the respiratory tract, which results in a loss of performance, has been reported in racehorses. Much research has focused on the influence of high-intensity exercise of a short duration on immune system function in horses, but scant attention has been given to prolonged endurance exercise as an immune modulator. OBJECTIVES: The objective of this study was to evaluate the effect of an 80 km endurance race on the monocyte and neutrophil oxidative burst, serum cortisol, glutamine and plasma glucose concentrations in 8 endurance-trained horses (mean +/- s.d. age 9.4 +/- 2.2 years). METHODS: Blood samples were drawn from the horses prior to and following an 80 km ride. RESULTS: Mean time for completion of the 80 km race was 306 +/- 40 mins. Immediately post race mean serum cortisol concentration, blood monocyte and neutrophil counts were higher and blood lymphocyte counts and plasma glucose concentration were lower compared with prerace values (P < 0.05). Neutrophil and monocyte oxidative burst activity decreased following the race and had not regained prerace values after 3 days of rest (P < 0.05). CONCLUSIONS: The present study indicates that long duration exercise in horses has a negative impact on the function of the innate immune system that lasts several days post race. Precise mechanisms instigating the fall in innate immune system function are unclear and multifactorial, but may be attributed, at least in part, to a high serum cortisol response during very prolonged exercise. POTENTIAL CLINICAL RELEVANCE: A prolonged bout of exercise results in a long-term suppression of the innate immune system function in horses which may, in part, account for the observed increase of infectious episodes in horses during training.     

Acid-base values of standardbred horses recovering from strenuous exercise.

Blood gases, lactic acid concentrations, and pH were measured in arterial and mixed venous blood in moderately conditioned Standardbred horses after a standardized exercise load of 1.6 km in 2 minutes, 40 seconds. Samples were obtained at rest, immediately after exercise, and at 3, 6, 15, 30, and 60 minutes after exercise. Arterial oxygen tension and mixed venous oxygen tension increased after exercise, reaching peak values at 6 minutes. Arterial oxygen tension returned to the resting (preexercise) value by 15 minutes, and mixed venous oxygen tension by 30 minutes. Arterial carbon dioxide tension decreased immediately after exercise, reaching its lowest value at 6 minutes, and returned to resting value by 30 minutes. Mixed venous carbon dioxide tension reached its highest value immediately after exercise, then decreased to less than the resting value, reaching its lowest value by 15 minutes, and returned to normal by 60 minutes. Lactic acid concentration increased immediately after exercise, reaching its highest value at 6 minutes, and returned toward normal by 60 minutes. Arterial pH decreased immediately after exercise, reaching its lowest value at 6 minutes, and returned to normal by 60 minutes. Mixed venous pH reached its lowest value immediately after exercise, then began to increase, and returned to normal by 60 minutes. The decrease in mixed venous pH was more pronounced than that in arterial blood since, in addition to the increase in lartic acid, there was a considerable increase in mixed venous carbon dioxide tension.     

Exercised-induced pulmonary hemorrhage in polo and racing horses

Philippine polo and racing horses were examined for exercise-induced pulmonary hemorrhage after their competitive exercise. Exercise-induced pulmonary hemorrhage occurred in 11.1% of the polo horses and 64% of the racing horses. None of the horses had blood at the nostrils.     

Hemostatic studies in racing standardbred horses with exercise-induced pulmonary hemorrhage. Hemostatic parameters at rest and after moderate exercise.

The purpose of this study was to determine whether a defect in hemostasis might be a factor in the etiology of exercise-induced pulmonary hemorrhage (EIPH). Hemostatic parameters were evaluated in 22 EIPH-positive and ten EIPH-negative racing horses while in a rested state. Nineteen EIPH-positive and ten EIPH-negative horses were further evaluated just before and immediately after a 15 min exercise period on a 260 m oval track. When EIPH-positive and EIPH-negative horses were compared at rest, there was no significant difference in any of the coagulation and fibrinolytic parameters studied. There was however, a significant difference in platelet function as assessed by aggregometry. The platelets from affected horses were significantly less responsive than those from nonaffected horses when exposed in vitro to the platelet agonists adenosine diphosphate, collagen and platelet activating factor. Exercise tended to increase the packed cell volume and factor VIII/von Willebrand factor and to decrease platelet aggregation responses to low concentrations of adenosine diphosphate. These effects of exercise however were quantitatively similar in both EIPH-positive and EIPH-negative horses. Reduced platelet function may therefore be a contributing factor in the bleeding characteristic of horses with EIPH.     

Changes in serum muscle enzyme levels associated with training schedules and stage of the oestrous cycle in Thoroughbred racehorses

Blood samples were collected twice weekly over a nine month period from 24 Thoroughbred racehorses in training at Newmarket to study the effects of daily training schedules and stage of oestrous cycle on serum enzyme levels and clinical signs of equine exertional myopathy. The sampling period extended from November to July and was performed between 16:00 h and 18:00 h so as to be at least 6 h after exercise. Serum creatine kinase, aspartate aminotransferase and plasma progestogen concentrations were measured. All horses were subjected to a similar traditional training programme. The study demonstrated marked fluctuations in serum muscle enzyme concentrations which were more pronounced in two-year-old fillies than three-year-old fillies and colts. There was no correlation, however, with the stage of oestrous cycle. It was concluded that some degree of muscle cell damage, which results in a variable increase in serum creatine kinase levels, occurs in all horses following light exercise after a rest day. Traditional flat race training may not be ideal in this respect and it is suggested that, for horses with an observed tendency towards exertional myopathy, more consistent and longer periods of less strenuous exercise may be advantageous.     

蒙古马不同耐力运动水平的血浆代谢组特征研究

旨在应用核磁共振(¹H-NMR)技术研究蒙古马耐力训练前后血浆代谢组变化特征。本研究选取6匹去势蒙古马：年龄(5.33±0.82)岁、体高(136.83±0.75) cm、体长(143.33±2.58) cm、胸围(157.17±2.04) cm、管围(18.45±0.27) cm，进行15及30 km步法为快步的耐力运动训练，采集其训练前后共计24份血液样本。采用氢质子共振频率600.13 MHz的Bruker AV III核磁共振谱仪测定血浆代谢物谱图信息。通过R语言偏最小二乘判别(PLS-DA)程序包及SPSS 20.0软件一维方差分析检验，鉴别组间代谢模式及差异代谢标志物。结果表明，在蒙古马15和30 km两次运动前后血浆代谢物中共发现47种差异代谢物，其中15 km运动前后鉴定出21个差异代谢物，运动后发现乙醇、甘露糖下降，葡萄糖、乙酰乙酸、丙酮酸、乳酸、肌酐、甘油、缬氨酸、丙氨酸、亮氨酸、酪氨酸、苯丙氨酸、苏氨酸、异丁酸、蛋氨酸、2-羟基异丁酸、O-乙酰肉碱、3-羟基异丁酸、3-甲基-2-氧代戊酸、3-羟基异戊酸升高。30 km运动前后鉴定出10个差异代谢物，运动后发现乙醇、葡萄糖、赖氨酸、甘氨酸、脯氨酸、谷氨酰胺、τ-甲基组氨酸、缬氨酸下降，甲醇、肌酸升高。对15 与30 km运动后进行比较发现，丙氨酸、柠檬酸、乙酸、赖氨酸、丙二酸、丙酮、2-羟基异戊酸、2-羟基异丁酸、泛酸、甜菜碱、异丁酸下降，乳酸、二甲基砜、丙酮酸、N-苯乙酰甘氨酸、马尿酸盐、甲醇、3-羟基异戊酸升高。在蒙古马15和30 km两次运动前后血浆代谢物中共发现47种差异代谢物，且两次运动前后的差异代谢物类别存在明显不同。蒙古马30 km负荷以脂肪酸有氧代谢为主方式供能，而15 km负荷以糖酵解无氧代谢为主的方式供能，酮体代谢是能量供应模式转换的过渡性阶段。本研究结果为我国耐力型运动马的训练及选育工作提供了理论依据。     

Effects of cooldown methods and durations on equine physiological traits following high-intensity exercise

This study was initiated to investigate the physiologic effects of cooldown methods and durations on recovery following high-intensity exercise (3000 m, 10 m/s) of 25 Jeju crossbred horses. Heart rate (HR) was measured and blood samples were collected for glucose, blood lactate concentration, packed cell volume (PCV), total protein (TP), and hemoglobin (Hb) analysis. The cooldown methods employed involved walk rest (WR) or trot rest (TR), and the durations compared were 15, 30, and 60 min. A passive rest group (PR) was used as a control. According to the analysis, HR decreased after a 15 min rest in all groups, showing a faster recovery in the active rest groups, WR and TR, than in the PR group after 30 min (P < 0.05). In the case of glucose, the decrease was faster in the WR15 group then the WR30 group suggesting that active rest is more effective in controlling this parameter (P < 0.05). As for lactate, TR15 showed a 75% decrease which was a significantly positive effect. There were no differences in PCV between the groups. Horses in the PR group showed faster recovery for TP and Hb than those in the active rest groups (P < 0.05), while lactate removal was faster in active rest groups than in the PR group, suggesting that the cooldown process plays an important role in recovery. This study showed that the cooldown method and duration employed after high-intensity exercise of horses makes a difference with regard to their physiologic status. Also, 15 min rest after exercise appears to be the most significant period in terms of duration. In conclusion, active rest was necessary for rapid recovery and a 15 to 30 min cooldown walk or trot was beneficial to the horses in which physical fatigue had accumulated. In particular, the active exercise method of trotting was found to be more effective than walking to remove lactate. In addition, the cooldown duration is expected to be more effective when adjusted according to the individual training state of the horse.     

Physical, Hematological, and Biochemical Responses to Acute Intense Exercise in Polo Horses

The aim of this study was to evaluate the response of physical, hematological, and biochemical parameters after acute intense exercise in polo horses playing in an outdoor international competition. The game consisted of four periods (chukkas) and each period consisted a playing time of 7 minutes. Two matches were played everyday for a week. A total of 12 horses were examined. Each “high-goal” polo horse played one chukka a day for 4 days. Horses were clinically examined the day before the games started and then daily during the 4 days of their participation in the games. During these days, physical examination was performed and blood sample was collected at rest (T0), immediately (T1) after exercise, and after 30 minutes of exercise (T2). Blood samples were analyzed for total cell counts and for determination of creatine kinase, lactate dehydrogenase (LDH), aspartate aminotransferase, lactate, total proteins, calcium, magnesium, phosphorus , and cortisol. Data were evaluated using two-way analysis of variance. Exercise caused significant dehydration (P < .01), mucous membranes congestion, increased heart rate (P < .001), and capillary refill time (P < .001). It also caused increased value of the following parameters: hematocrit (P < .001), red blood cells (P < .001), hemoglobin (P < .001), white blood cells (P < .05), lymphocyte (P < .001), total proteins (P < .001), creatine kinase (P < .05), LDH (P < .01), lactate (P < .001), and cortisol (P < .01), and a decrease in the platelet count (P < .001), calcium (P < .01), phosphorus (P < .001), and magnesium (P < .001). All parameters returned within or near the reference range by 30 minutes postexercise. On the basis of these observations, data were considered indicative of a good response to an acute intense exercise. Moreover statistical results obtained were typical of a mixed aerobic/anaerobic metabolic pathway that is prevailing in this sport.     

Heart rate, blood biochemistry and performance of horses competing in a 100 km endurance ride

To determine whether a clinical examination was adequate to assess the fitness of horses in an endurance ride, and to characterise the relationship between a clinical assessment of the horse's fitness and its blood biochemistry, 23 horses were monitored before, during and after an 87 to 100 km endurance ride. Blood samples were taken before the ride, at three checkpoints on the ride, immediately after the ride and one day later for the determination of packed cell volume, total protein, lactate, glucose, non-esterified fatty acids, creatine phosphokinase, aspartate aminotransferase and plasma electrolytes. Heart rate measurements appeared to be a reliable indicator of the metabolic status of endurance horses suggesting that veterinary examinations according to the official Fédération Equestre Internationale rules are adequate to protect the health and welfare of horses competing in endurance races.     

Salivary Cortisol Concentration in Exercised Thoroughbred Horses

Both physical activity and stress result in an increase in plasma cortisol level. The measurement of cortisol in plasma requires taking blood samples, which is stressful itself. Therefore, the aim of this study was to evaluate the use of saliva sampling for the determination of cortisol concentrations, indicating the intensity of exercise in horses during race training. Twelve Thoroughbred horses aged 2-3 years were examined during their speed training sessions. The horses galloped on the 1,200-m sand track at a speed of 14.4-15.3 m/s. Three saliva samples and three blood samples were collected from each horse. Both types of samples were taken when the horse was at rest, immediately after returning from the track and 30 minutes after the end of exercise. Blood lactic acid (LA) concentration was determined using the enzymatic cuvette test. The concentrations of cortisol in saliva and plasma samples were measured by enzyme immunoassay methods. Statistically significant correlations were found between salivary cortisol level determined 30 minutes after the end of exercise and blood LA concentration obtained immediately after exercise (P = .003) and between salivary and plasma cortisol levels measured 30 minutes after the end of training session (P = .015). The measurement of cortisol concentration in saliva samples taken from race horses 30 minutes after the end of exercise can be recommended for use in practice under field conditions to estimate the level of relative intensity of exercise in race horses.