Higher Lipid Peroxidation Indices in Horses Eliminated from Endurance Race Because of Synchronous Diaphragmatic Flutter (Thumps)

Abstract

Eighteen racing horses from a total of 85 horses that participated in a long-distance (120-km) race were used for this study. The 18 horses that were used comprised nine horses that were eliminated from the race at the 90-km checkpoint because of synchronous diaphragmatic flutter (SDF). Another nine horses that passed the 90-km checkpoint were randomly selected and served as a control group (CT). Horses were sampled at three different times (t₀, t_end, t_2weeks). Plasma sodium (Na⁺), potassium (K⁺), and chloride (Cl⁻) concentrations were decreased at the end of the race to insignificant levels. A significant reduction (P ≤ .05) was observed in the ionized calcium (Ca⁺⁺). Lipid peroxide (LPO) and malondialdehyde (MDA) concentrations in plasma were higher compared with values obtained before the start of the race. In SDF-eliminated horses, these parameters were higher than in the control horses. Glutathione peroxidase (GSH-Px) activity was significantly lower at the end of the race, whereas creatine phosphokinase (CPK) was similarly increased fourfold in both groups. A significant increase in lactate concentration was seen in both groups; however, this parameter was significantly higher in the SDF-eliminated horses than in the control group. Statistical significance (P < .01) was observed between LPO and MDA levels and the Ca⁺⁺ concentration in the SDF group at the three sampling points. This study established elevated lipid peroxidation product level as one component of the biochemical characteristics of SDF. The low level of Ca⁺⁺ in plasma of horses was associated with high levels of lipid peroxidation indexes.

Keywords: Peroxidation, Horses, SDF, Ionized calcium, Antioxidants