Metabolic Profiles of Finishing and Nonfinishing Horses in Uruguayan Raid Competitions

The Raid Hípico Uruguayo (RHU) is the oldest equestrian endurance sport in Uruguay. A high percentage of horses fail to complete RHU rides. Therefore, the aim of this study was to investigate whether weather conditions (comfort index [CI]), horse experience, and ride distance affect horse performance (finishing ride [FR] or nonfinishing ride [NFR]) in the RHU. An additional objective was to determine whether finishing the ride affects the hematological and biochemical parameters of the horses. This study involved 17 RHU rides over distances of 60-90 km and 284 horses. Blood samples were taken before and after the competition or upon withdrawal (retired or eliminated). The nonfinishing group consisted of 169 horses. Horse performance was associated with CI (P < 0.05), but not with ride distance (P = 0.33). Horse experience tended to be associated with finishing the ride (P = 0.09). Hematocrit, creatine kinase activity, urea, and uric acid concentrations were greater in FR than in NFR horses (P < 0.05) and all parameters were affected by the time of sampling (P < 0.001), being higher in the postride sample. Weather conditions significantly affected horse performance during RHU competitions, whereas ride distance showed no effect. We observed changes in hematological and biochemical parameters regardless of the horse's performance. Most changes seemed to be caused by a decrease in blood volume, an increase in energy expenditure, and muscle damage that were not the result of metabolic disease but were related to a physiological response to the intensity and duration of exercise.