Fédération Equestre Internationale (FEI) has described equine endurance racing as the second largest discipline in the world, above which is only show jumping. The Žemaitukai is an ancient indigenous Lithuanian horse breed known since the 6th or 7th century. The Arabian horse breed is one of the oldest human-developed horse breeds in the world. Compared with other race horse breeds, the muscle tissue of Arabian horses is characterized by significant differences in structure—a predominance of oxidative fiber type I is observed in Arabians, making them the prevailing breed in endurance racing. The Arabian horses are recognized as the leading breed in endurance competitions. Speed, pace, and total time in the race strategy have been extensively studied in human sports, and in contrast, this strategy appears to have been virtually ignored in equestrian sport, despite the potential for contributing to performance optimization. In relation to speed and total time in the race, there are limited data on postrace physical, biochemical, and blood gas parameters of endurance horses. Thus, this study was carried out to investigate the effects of speed on the blood parameters of the Arabian and Žemaitukai horses during an endurance race. Blood samples were taken before and immediately after the exercise. Biochemical and blood gas indicators were analyzed. The study showed significant increases in mean blood gasometrical indicators, such as partial carbon dioxide pressure (8.09–15.18%, p < 0.001); base excess in the extracellular fluid (14.01%, p < 0.001 in the Arabian horses and 172.01% in the Žemaitukai breed, p = 0.006); decreases of the blood electrolyte ionized calcium (4.38–8.72%, p < 0.001) and the hematocrit and hemoglobin values (20.05–20.12%, p < 0.001 in the Arabian horses and 6.22–6.23% in the Žemaitukai breed, p = 0.003–0.004); and decreases in the base excess in the blood values (29.24–39.38%, p < 0.001) and lactate (13.45–31.97%, p < 0.001) in the blood of both breeds in the post-competition horses. Significant increases after competition were determined for the values of creatinine (21.34–30.82%, p = 0.001–0.004), total bilirubin (50.84–56.24%, PH < 0.001), and albumin (2.63–4.48%, p = 0.048–0.001) for both breeds. For the faster Arabian horse breed, recovering after racing took half the time that the local Žemaitukai breed did.

Climatic variations directly affect the animals, changing their physiology. Several factors such as species, breed, sex, age, nutrition, diseases, physiological stage, and seasonal variations can affect the pattern of haematological values. Quantitative and morphological changes in blood cells are associated with higher temperatures and humidity. Sixty-seven sheep (3 years old, not pregnant, clinically healthy) were used in the study to determine the effect of the temperature-humidity index (THI) and breed on morphological blood indices and β-hydroxybutyrate (BHB). The sheep were divided into groups by the breed (4 breeds) and the THI (2 classes). The blood samples from each animal were collected monthly. Significant differences between the values of leukocytes (WBC), neutrophils (NEU), erythrocytes (RBC), haemoglobin (HGB), haematocrit (HCT), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), lymphocytes (LYM), monocytes (MON) and platelet count (PLT) in THI groups were observed. In THI 1, the mean values of MCHC (5.68%, P < 0.05), MCH (0.52%), and HCT (4.90%, P < 0.05) were higher compared to those in THI 2. Multivariate test showed a significant effect of breed on NEU ( P < 0.05), RBC ( P < 0.05), HGB ( P < 0.05) and MCHC ( P < 0.05). The concentration of BHB in group THI 2 was by 12.9% higher ( P < 0.05), compared to group THI 1. A significant effect of the breed ( P < 0.05) and THI class ( P < 0.05) on BHB was determined, whereas the impact of breed interaction with the THI was found to be non-significant. The observations reported in this study suggest that the response to temperature is dependent on animal breed. It was found that both morphological blood indices and BHB were affected by the temperature-humidity index.

The Lithuanian Žemaitukai horse breed is one of the oldest in Europe. Currently, there is a lack of information about the effect of endurance competition on blood indices and acid–base balance in the Žemaitukai horses. The aim of this study was to evaluate the effect of endurance exercise on the acid–base balance and electrolyte indicators of the Žemaitukai horses in an official endurance competition. In total, 48 horses of the Žemaitukai breed competed in endurance competitions over the same distance (60 km). Samples were taken before and immediately after the exercise. The following indicators were analysed: the hydrogen potential (pH), partial carbon dioxide pressure (pCO ₂ ), partial oxygen pressure (pO ₂ ), base excess in blood (BE), base excess in the extracellular fluid [BE (ecf)], cHCO ₃ (bicarbonate), cSO ₂ (oxygen saturation), tCO ₂ (blood total carbon dioxide), haematocrit (HCT), haemoglobin concentration (cHgb), sodium (Na), potassium (K), calcium (Ca), chlorides (Cl), and lactate (Lac). Increase in pH showed adaptation of the horse metabolism to exercise. Blood changes were caused by the development of dehydration and metabolic alkalosis. According to Lac results, all horses were fit and tolerated well physical activity. The exercise did not significantly affect the demand for minerals. Based on the results obtained, it can be stated that horses of the Žemaitukai breed are suitable for endurance competing.

The study was conducted on 30 clinically healthy Arabian horses and 28 Žemaitukai horses that competed in endurance race over the same distance (40 km). Blood samples were taken before and immediately after the exercise. The environmental conditions during the competitions varied, with a mean temperature of 22.5 °C and a mean relative humidity of 73.20%. The Žemaitukai horses showed lower haematological values and increased muscle catabolism after exercise. Arabian horses have higher aerobic capacity compared to the Žemaitukai horses which probably contributes to their superior low- to moderate-intensity exercise performance. Serum activity of muscle enzymes suggested that the muscle tissue of the Arabian horses has higher tolerance for exercise-induced muscle catabolism and lower muscle catabolism than that of muscle tissue of the Žemaitukai horses. Further studies need to be carried out to identify the diferences in muscle tissue of both breeds.

The aim of this study was to find whether the magnitude of changes in blood before and after horse endurance competitions was the same at the beginning and the end of the season and if the studied indices could be useful in assessing the impact of such changes on the length of the endurance racing season. The study was conducted on 36 clinically healthy horses. Blood samples were taken during 60-km endurance competitions in 2014, three times in total. The study revealed an increase of lymphocytes (× 1.89-2.05; P < 0.001), red blood cell count (× 1.11-1.12; P < 0.001), and a decrease in the mean corpuscular haemoglobin concentration (× 1.20-1.27; P < 0.001), red cell distribution width (× 1.11; P < 0.01), platelet concentrations (× 1.33-1.40; P < 0.05), when compared at the beginning and in the end of the horse endurance racing season. During the entire season, haematocrit values significantly increased after the race but were at their lowest in the mid-season period. The results proved a significant increase in the white blood cell and granulocyte counts following the finish of a 60-km endurance race, when comparing the values at the beginning and in the end of the horse endurance racing season, and a significant reduction in lymphocytes when comparing the values at the beginning (35.7%) and at the end (29.7%) of the season. The endurance competition season highly influences haematology indices in horses' blood, however, to determine the season's impact on the results of the race, additional studies must be conducted.