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Physical effort is one of the key aspects of keeping horses in good condition. The condition of the animal is reflected by multiple blood parameters. The newly discovered cytokine–apelin can pose one of them, however, so far, has not been studied in the horse population. Apelin is produced by adipocytes and myocytes and plays an important role in the energy metabolism of the body through the influence, for example, on the process of adipogenesis and lipolysis. The aim of this study was to investigate if physical effort of various intensity affects the plasma concentration of apelin in horses. The study involved 20 purebred Arabian horses divided into two groups. The first group included 10 race horses, aged 3 years, and second group included 10 horses aged from 6 to 12 years, used in endurance rides. Blood samples were collected from each horse at rest and after exercise. The concentrations of apelin, lactic acid, cortisol, uric acid (UA), triacylglycerols, total plasma protein, and glucose were determined in plasma samples. Race training sessions induced significant decreases in plasma apelin concentrations (P <.05). In endurance horses, significant correlations were found only between exercise-induced changes of apelin and cortisol (r = 0.55) and apelin and UA (r = 0.67) concentrations. In conclusion, the concentration of apelin in equine plasma decreases in response to short-time exercise unlike endurance exercise. Blood plasma apelin concentration determined at rest is lower in long-time regularly trained horses than in the ones at the beginning of their training process. • Apelin plays an important role in energy metabolism. • Changes in plasma apelin level in exercised horses were studied for the first time. • Plasma apelin concentration decreased after race training session. • In endurance horses, changes in plasma apelin and cortisol levels were correlated. [ABSTRACT FROM AUTHOR]

Intensive exercise results in the increased blood concentration of the acute phase proteins in horses competing in some sport disciplines. In this study, the blood level of serum amyloid A (SAA) was analyzed in Thoroughbred racehorses during 5 days after completion of the race. Samples were collected from 25 healthy Thoroughbred horses beginning with 4 hours after the race and repeated daily up to the fifth day after the race. Serum amyloid A analysis was performed using commercial enzyme-linked immunosorbent assay kit, and the results were presented as median, interquartile range (IQR), and range. Data were analyzed using Friedman's nonparametric analysis of variance. The acute phase response (APR) was reflected by an increased SAA level after the race, reaching significantly higher concentrations on days 1 ( P < .001) and 2 ( P = .005) and falling below the level of the first sample on day 5 ( P = .006). The median peak concentration observed on day 1 after the race was 3.84 mg/L (IQR, 2.32 to 8.86). Racing induces minute changes in SAA concentration typical for the exercise-induced APR; however, the significance of this reaction in the context of horse health and fitness remains unclear. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: Acute phase proteins (APP) have been described as useful for assessing health in human and animal patients, as they closely reflect the acute phase reaction (APR). In humans and dogs a reaction analogous to APR has also been described after prolonged or strenuous exercise. The aim of this study was to determine, if similar reactions occur in endurance horses after limited and long distance rides. Seventeen horses that successfully completed various distance competitions were tested. Routine haematological and biochemical tests were performed and the concentrations of serum amyloid A (SAA), C-reactive protein (CRP) and haptoglobin were measured. Typical endurance exercise-induced haematological and biochemical changes were observed in all horses, regardless the distance. After long distance rides, the level of SAA markedly increased, but CRP and haptoglobin concentrations remained unchanged. After limited distance rides no changes in the levels of APPs were noted. Exercise-induced APR in horses occurred only after prolonged, strenuous exertion, and differed from APR in inflammation in that only SAA concentration was increased. [Copyright &y& Elsevier]