REASONS FOR PERFORMING STUDY: Interest in establishing oxidant/ antioxidant profiles in competition horses is increasing. Earlier studies performed in horses have mainly been performed under laboratory conditions using a treadmill and it is not known to what extent laboratory results of oxidant/antioxidant studies might be transposed to field conditions. OBJECTIVE: To compare the impact on the blood oxidant/ antioxidant status of a standardised exercise test including a run up to fatigue performed on a treadmill (TM) and on a racetrack (RT) in healthy and trained Standardbred horses. MATERIAL AND METHODS: During TM and RT tests the following blood antioxidant markers were analysed in jugular venous blood at rest and 15 mins (E15) after an intense bout of exercise: uric acid (UA), ascorbic acid (AA), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione (reduced: GSH and oxidised: GSSG), glutathione redox ratio (GRR) and protein thiol (PSH). Running time to fatigue (RTF), velocity during the last exercise stage (Vmax), final heart rate (HRfinal) and venous lactic acid (LA) were also recorded. RESULTS: Vmax was significantly (P<0.05) higher during the RT, whereas LA was significantly lower. HRfinal and RTF did not differ significantly between TM and RT. Exercise induced a significant increase (R vs. E15) of UA and AA in both tests, whereas GSH and PSH decreased significantly. GPx, SOD, GSSG and GRR remained unchanged. Differences between TM and RT were significant at E15 for UA, AA and PSH. CONCLUSIONS: Comparison of oxidant/antioxidant profiles from laboratory and field studies are difficult to standardise and should be interpreted with caution. POTENTIAL RELEVANCE: For the same RTF and final HR, the TM induced stronger changes in blood lactate and in blood oxidant/antioxidant balance than did RT.
REASONS FOR PERFORMING STUDY: Interest in establishing oxidant/ antioxidant profiles in competition horses is increasing. Earlier studies performed in horses have mainly been performed under laboratory conditions using a treadmill and it is not known to what extent laboratory results of oxidant/antioxidant studies might be transposed to field conditions. OBJECTIVE: To compare the impact on the blood oxidant/ antioxidant status of a standardised exercise test including a run up to fatigue performed on a treadmill (TM) and on a racetrack (RT) in healthy and trained Standardbred horses. MATERIAL AND METHODS: During TM and RT tests the following blood antioxidant markers were analysed in jugular venous blood at rest and 15 mins (E15) after an intense bout of exercise: uric acid (UA), ascorbic acid (AA), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione (reduced: GSH and oxidised: GSSG), glutathione redox ratio (GRR) and protein thiol (PSH). Running time to fatigue (RTF), velocity during the last exercise stage (Vmax), final heart rate (HRfinal) and venous lactic acid (LA) were also recorded. RESULTS: Vmax was significantly (P<0.05) higher during the RT, whereas LA was significantly lower. HRfinal and RTF did not differ significantly between TM and RT. Exercise induced a significant increase (R vs. E15) of UA and AA in both tests, whereas GSH and PSH decreased significantly. GPx, SOD, GSSG and GRR remained unchanged. Differences between TM and RT were significant at E15 for UA, AA and PSH. CONCLUSIONS: Comparison of oxidant/antioxidant profiles from laboratory and field studies are difficult to standardise and should be interpreted with caution. POTENTIAL RELEVANCE: For the same RTF and final HR, the TM induced stronger changes in blood lactate and in blood oxidant/antioxidant balance than did RT.