Antioxidant trace elements in serum of draft horses with acute and chronic lower airway disease.

The aim of the present study was to evaluate the oxidative stress level and antioxidant trace elements status associated with lower airway disease in draft horses. For this purpose, venous blood samples were obtained from draft horses exhibiting signs of lower respiratory tract disorders (n = 83) and from control group (n = 20). Serum trace elements including selenium (Se), copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) were assayed. Serum malondialdehyde (MDA) and low-density lipoprotein (LDL) levels as well as plasma hydrogen peroxides (H₂O₂) concentration and activity of plasma glutathione reductase (GR), glutathione-S-transferase (GST) and catalase (CAT) were measured. There was a significant (p < 0.05) decrease of Se, Cu, Zn, and Fe in diseased horses compared with healthy ones, but the Cu/Zn ratio and Mn were increased (p < 0.05). Se was significantly (p < 0.05) decreased in chronically affected horses compared with acute cases, but Mn was increased (p < 0.05). There was an increase of MDA, LDL, and H₂O₂ levels and GR activity in diseased cases compared with healthy horses. However, there was a significant (p < 0.05) decrease of GST and CAT activity. MDA and LDL levels were increased (p < 0.05) in horses with chronic respiratory disease compared to acute cases, but CAT activity was decreased (p < 0.05). In horses with acute lower airway disease, there was a negative correlation between GR and H₂O₂ (r = -0.458), and LDL and CAT (r = -0.816). However, in chronic disease, a negative correlation was recorded between Se and MDA (r = -0.590). The results of the present study indicate that oxidative stress, with alteration of antioxidant trace element levels, is a feature of respiratory disease in draft horses.