Effect of prolonged submaximal exercise on serum oxidative stress biomarkers (d-ROMs, MDA, BAP) and oxidative stress index in endurance horses

Background: Oxidative stress (OS) associated with an intense exercise may have a negative influence on equine health. The aim of this study was to determine the effects of endurance races on oxidative and antioxidative status of horses by evaluating changes in reactive oxygen metabolites (d-ROMs), malondialdehyde (MDA), biological antioxidant potential (BAP) and oxidative stress index (OSI) values. The study was carried out on 53 race starts (28 individual horses) competing at different endurance races according to distance (40 and 80 km) and difficulty (easy and demanding). Blood samples were taken before and after the race. Results: Compared to levels of OS serum biomarkers before the race, an increase in values of d-ROMs (P < 0.01), MDA (P < 0.01), and BAP (P < 0.001), and a decrease in OSI (P < 0.001) have been noted after the race. Contrary to other measured biomarkers, BAP did not show significant individual effects of horses. Horses competing at shorter races have shown a significant change in d-ROMs (P = 0.002), BAP (P < 0.001) and OSI (P = 0.004), whereas those competing at longer races in MDA (P = 0.002), BAP (P < 0.001) and OSI (P < 0.001) post-race values. Endurance racing induced changes in values of d-ROMs, BAP and OSI during both easy and demanding races. Conclusions: Changes in all measured OS biomarkers indicate that prolonged aerobic exercise during endurance race could contribute to the imbalance between oxidants and antioxidants in horses, mainly characterised by a pronounced antioxidant response. Biological antioxidant potential was found to be the most reliable biomarker of OS in endurance horses in the present study.