PSX-A-18 - Late-Breaking: Oxidative stress biomarkers in blood plasma of moderately exercised horses

Oxidative stress by physical stressors negatively impacts the performance of equine athletes. The present study was aimed to determine oxidative biomarkers in blood plasma of exercising horses. Stock-type horses were subject to a standardized moderate intensity exercise protocol following NRC guidelines 3 times per wk for 8 wk. Blood plasma was collected in wk 1, 2, 7, and 8 immediately before and 0, 30, 60, and 90 min after exercise and analyzed for total antioxidant capacity (TAC), thiobarbituric acid reactive substance (TBARS), glutathione peroxidase activity (GPx), and superoxide dismutase activity (SOD). Data were analyzed as repeated measures with wk, d, time, and their interactions as fixed effects. The TAC on d 2 (0.40 mM trolox) were 7.5% greater than that on d 3 (P = 0.013). There were wk × d × time interactions for SOD, TBARS, and GPx (P < 0.001). The TBARS remained at d-1 wk-1 pre-exercise baseline (2.70 µM malondialdehyde) for most collection times within wk 1, 7, and 8 (P ≥ 0.058); however, TBARS increased by 0.24 to 0.41 µM on d 2 of wk 2 post-exercise (P < 0.001) and remained similarly elevated on d 3 pre- and immediately post-exercise (P < 0.001). The GPx similarly remained at baseline (172.57 µM/min; P ≥ 0.621) but increased by 48.18 to 83.36 µM/min at most collection times on d 1 and 2 of wk 2 (P ≤ 0.023). The SOD remained at baseline (167.21 µM/min; P ≥ 0.055) until increasing by 11.28 to 15.61 µM/min at 30 min post-exercise on d 1, wk 1 and at most collection times on d 3, wk 8 (P ≤ 0.043). The current study indicates the time-dependent nature of oxidative stress in relation to persistent stressors such as exercise.