Effect of Dietary Supplementation with Vitamin E and Selenium in Thoroughbred Horses on the Concentration of F2-isoprostanes in the Blood Plasma as a Marker of Lipid Peroxidation

The objective of this study was to assess the effect of vitamin E and selenium (Se) supplementation on the plasma levels of F2-isoprostanes as a marker of oxidative stress in horses in their training period. Twelve healthy 3-year-old English thoroughbred horses were divided into two groups: control (n = 6) and experimental (n = 6). Feeding rations were adapted to a moderate workload. The horses of the experimental group received supplements of DL-α-tocopheryl acetate E (2 250 mg/day/horse) and of sodium selenite (0.5 mg/day/horse). The plasma concentrations of both antioxidants and F2-isoprostanes were monitored on days 0, 44 and 70. After 70 days of supplementation, the concentrations of selenium in the experimental group were significantly higher (P -1 vs. 98.70 ± 10.88 μg l -1), as well as to the control group (day 0: 101.78 ± 11.06 μg l -1, day 70: 108.18 ± 7.77 μg l -1). In the horses of the experimental group, plasma α-tocopherol levels significantly increased from the 44th day of supplementation compared to the beginning of the study as well to the control group (5.23 ± 0.52 mg l -1 vs. 2.45 ± 0.25 mg l -1 or 3.46 ± 0.34 mg l -1, respectively). The plasma concentration of F2-isoprostanes tended to be lower in the experimental group at the end than at the beginning of monitoring (156.8 ± 12.89 pg l -1 vs. 170.3 ± 60.8 pg l -1), although the control group showed the opposite trend (181.2 ± 15.67 pg l -1 vs. 137.0 ± 47.05 pg l -1). Nevertheless, none of these differences were significant because of the large variability of the individual values. It can be stated that supplementation of the diet used with selenium and vitamin E caused a non-significant decrease of F2-isoprostane concentration in the blood plasma only, and a significant increase of plasma concentrations of these antioxidants. The variation of isoprostane levels probably reflected rather the individual responses of the horses' organisms to the training workload