Many classes of antioxidant dietary compounds have been suggested to present health benefits for athletic horses and there is evidence that consumption of these products leads to a reduction of the expression of different oxidative stress biomarkers. In athletic horses, various antioxidant supplementation trials have provided evidence that exercise-induced disturbances could be partially prevented. McMeniman and Hintz (1992) studied the oral vitamin E supplementation in polo ponies and demonstrated a negative correlation between blood vitamin E concentration and some markers of lipid peroxidation. Avellini et al. (1999) also investigated the influence of vitamin E and selenium supplementation in racehorses and described an increase of antioxidant capacity. The influence of vitamin C supplementation has been studied in Thoroughbreds (White et al. 2001) and endurance horses (Williams et al. 2004a). White et al. (2001) found that vitamin C supplementation could prevent exercise-induced increase of some markers of lipid peroxidation and could maintain the plasma antioxidant capacity. On the other hand, Williams et al. (2004a) observed no treatment effect on muscle enzymes and markers of oxidative stress. Williams et al. (2004b) studied the effect of a supplementation with lipoic acid in endurance horses. The authors reported an increase of antioxidant status in supplemented horses. Those finding were confirmed by Kinnunen et al. (2005) in Standardbred trotters. Finally, in a field study, De Moffarts et al. (2005) investigated the effect of a mixture of vitamins and trace elements on 40 Thoroughbreds during a 3 month period. The authors concluded that oral antioxidant supplementation could improve the hydrophilic, lipophilic and enzymatic antioxidant blood capacity.
The major role of antioxidants is to inactivate or to transform oxidants, which can be transformed by antioxidant enzymes into less reactive forms or which can react with antioxidant molecules that are chemically stable. With catalase and gluthation-peroxidase (GPX), superoxide dismutase (SOD) is one of the most important antioxidant enzymes. Superoxide dismutase is an endogenously produced metalloenzyme present in every aerobic cell. It catalyses the dismutation of superoxide (O2·−) into oxygen and hydrogen peroxide.
In a specific variety of cantaloupe melon (Cucumis melo L), it was demonstrated that correlations exist between the maintenance of cellular integrity (i.e. a delayed senescence) and a particularly high level of SOD activity (Lacan and Baccou 1998). Following this finding, an encapsulated extract of this specific variety of cantaloupe melon has been developed and the effect of oral administration of this cantaloupe melon extract (CME) rich in SOD activity was studied in different experimental models. Vouldoukis et al. (2004a) confirmed the antioxidant and anti-inflammatory properties of CME in vitro, by measuring the effects of CME on redox status and production of pro- and anti-inflammatory cytokines by peritoneal macrophages. The anti-inflammatory properties of CME were principally related to its capacity to induce the production of anti-inflammatory cytokines by peritoneal macrophages. They also confirmed these properties by in vivo experimentation with a CME oral supplementation of mice. Moreover, it was demonstrated that an oral supplementation in CME could increase the resistance of red blood cells to oxidative stress-induced haemolysis in mice (Vouldoukis et al. 2004b). Muth et al. (2004) concluded to the efficacy of an orally effective SOD on hyperbaric oxygen-related cell damage. Naito et al. (2005) showed that a gastroprotected form of SOD could reduce the diabetes-induced renal oxidative stress in mice. The antioxidative effect of pumpkin seed protein isolate was also demonstrated in CCL4-induced acute liver injury in low-protein fed rats (Nkosi et al. 2006). Finally, Kick et al. (2007) concluded that oral CME may be a therapeutic option to reduce oxidative cell injury with a model of induced ischaemia/reperfusion (aortic cross-clamping) injury in pigs.
So far, no data are available on the influence of supplementation with CME selected for its high SOD activity on antioxidant equilibrium in athletic horses. The aim of this study was to evaluate the effects of a 60 day oral supplementation with a CME on muscular and antioxidant balance variables in a population of trotter horses in training.