Original ResearchHigher Lipid Peroxidation Indices in Horses Eliminated from Endurance Race Because of Synchronous Diaphragmatic Flutter (Thumps)
Introduction
Synchronous diaphragmatic flutter (SDF) is a disease of horses characterized by increased neuromuscular irritability, causing hypersensitivity of the phrenic nerve. Electrical activity occurring when the heart beats stimulates the phrenic nerve, which passes over the heart, resulting in a contraction of the diaphragm with each beat of the heart.1 This condition is manifested clinically as sudden bilateral or unilateral movement of the flanks of the horse at the same frequency as the heart rate. Sometimes the rhythmic movement also occurs in hind legs.1 A loss of calcium ions (Ca++) in the blood serum is the cause of SDF.1, 2
High work intensity can increase heat production 40-fold to 60-fold over basal metabolism.3 The major pathway for heat loss in the horse is sweating. The volume of heat loss and sweating depends on the work expended, which is increased by distance. A horse may lose 20 to 40 L fluid in long distance races.4 This fluid loss is accompanied by an obligatory loss of minerals and electrolytes. Loss of Na+, K+, and Cl− ions because of excessive sweating reduces the thirst response and leads to further dehydration. Sweating also results in excessive Ca++ loss; the dehydrated horse begins to show clinical signs of Ca++ deficiency, such as muscle twitching and spasms.5 It is reported that, in normal healthy horses, excessive dehydration or excessive work may result in a lack of energy, causing loss of function of the Ca++ pump.1
A number of studies have reported that exhaustive endurance races induce accelerated generation of reactive oxygen species (ROS). ROS result in lipid peroxidation, which induces adverse effects on the health status and performance of horses.6, 7, 8
Studies suggest that both lipid peroxidation and Ca++ are important contributors to cell damage caused by physical injury or ischemia. This may act synergistically to damage biologic membranes.9, 10 The possible interaction between those two factors has not, until recently, been addressed. It is known that, shortly after the onset of ischemia or physical injury, the extracelluler Ca++ concentration falls dramatically, resulting in intracellular Ca++ accumulation.11, 12 Intracellular Ca++ mobilization increases free Ca++ concentration in the cytoplasm, causing activation of some Ca++-dependent membrane phospholipases. Phospholipase A2 breaks down phosphatidylinositols at the site of membrane cyclooxygenase localization, resulting in release of arachidonic acid that enables cyclooxygenase activation. Hence, cyclooxygenase itself is not Ca++ dependent, but any increase of intracellular free Ca++ is critical for its activation.13, 14
Cells can tolerate mild oxidative stress and often respond by raising their levels of antioxidant defenses. However, severe oxidative stress and free radicals produce serious disturbances in cellular structure and metabolism.15 The intracellular levels of calcium ions are very low; they transiently increase in response to several factors producing important metabolic changes.16 Oxidative stress can damage the protein that keeps intracellular Ca++ low, causing an increase in the level of Ca++. If the Ca++ level rises too high, it can activate enzymes that may damage the DNA and cleave structural proteins within the cell.17
The aim of this study was to assess the possible relationship between low plasma calcium level and elevation in lipid peroxidation products (lipid peroxide [LPO] and malondialdehyde [MDA]) and the intrinsic antioxidant enzyme glutathione peroxidase (GSH-Px) in horses suffering from SDF during a long distance endurance ride.
Section snippets
Description of Endurance Race
The Wadi-Rum endurance race is held yearly in early October, with an ambient temperature ranging from 15°C to 25°C and relative humidity ranging from 30% to 32% (Jordanian Department of Meteorology). Participating horses were fed a diet consisting of barley, oat, corn, and hay. Water was provided ad libitum. Owners were allowed to provide supplemental feed and salts to their horses. Information on supplementation of horse diets with antioxidant compounds, such as vitamin E or selenium, was not
Results
Erythrocyte counts, leukocyte counts, and hematocrit and hemoglobin values of horses at the end of the race were significantly increased (P < 0.05) when compared with pre-race values. These values returned to their normal physiologic levels within 23 weeks after the end of the race (Table 1).
There were no significant differences detected among the two groups at any sampling time for sodium, potassium, and chloride concentration (Table 1). These parameters decreased in both control and
Discussion
During a prolonged endurance ride, a horse can lose 25 to 50 liters of fluid. This causes hemoconcentration and severe reduction in muscular capacity. It also results in losing ions such as Na+, K+, Ca++, and Cl−, causing some degree of neuromuscular irritability.1, 2 Evidence of hemoconcentration, including the changes in hemoglobin, packed-cell volume, and red blood cells observed in this study were obviously attributable to significant changes in plasma volume as a result of dehydration and
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Cited by (15)
Evaluation of Biological Indicators of Fatigue and Muscle Damage in Arabian Horses After Race
2019, Journal of Equine Veterinary ScienceCitation Excerpt :It has been shown that in untrained horses, exercise increases lipid peroxidation [21,22]. Al-Qudah et al showed that the lipid peroxidation before the race was significantly lower than that after the race [23]. The highest concentration of MDA in the study was recorded 24 hours after the race, which is consistent with the results of Jagrič Munih et al, Avellini et al, and Chiaradia et al [21,24,25].
Veterinary aspects of training and racing endurance horses
2013, Equine Sports Medicine and Surgery: Second EditionEffect of age and performance on physical, hematological, and biochemical parameters in endurance horses
2013, Journal of Equine Veterinary ScienceCitation Excerpt :Tissue remodeling can also occur in endurance competitions, and this is indicated by changes in plasma fibrinogen, urea, proteins, and creatine kinase (CK) [17]. Endurance horses require calcium for muscle contractions, and low plasma levels of calcium during strenuous endurance rides can lead to metabolic problems and failures, including synchronous diaphragmatic flutter [15,18]. However, hypercalcemia may increase the frequency of thumps during endurance competitions [16,18].
Pre and post -exercise variation of blood parameters on performance endurance horses: a first race study from Algeria
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