Anti-Fatigue Effects of Donkey Milk and Its Polysaccharides in a Mouse Swimming Model

Exercise-induced fatigue is a physiological limitation affecting athletic performance and recovery, driven by disrupted energy metabolism, oxidative stress, and inflammation. This study investigated the anti-fatigue effects of donkey milk and its polysaccharides in BALB/c mice using an exhaustive swimming model. Mice were randomly assigned to seven groups, including a negative control group and separate dose groups receiving donkey milk (2.08, 4.16, or 8.32 mL/kg) or donkey milk polysaccharides (0.625, 1.25, or 2.5 g/kg), for 30 days. Anti-fatigue activity was subsequently evaluated based on exhaustive swimming performance and fatigue-related biochemical parameters. Donkey milk polysaccharides, mainly composed of galactose, exhibited stronger in vitro antioxidant activity than donkey milk, which may be associated with their enhanced radical scavenging capacity. Both treatments significantly prolonged exhaustive swimming time (up to 2.27-fold, p < 0.05) without affecting body weight. They improved energy metabolic status (glycogen, ATP, lipid utilization), reduced fatigue-related metabolite accumulation, enhanced antioxidant capacity, and suppressed oxidative stress and inflammatory responses, with donkey milk polysaccharides generally showing superior efficacy. The in vitro antioxidant activity was consistent with in vivo improvements in oxidative status, supporting a functional link between polysaccharide bioactivity and physiological effects. These findings suggest that donkey milk and its polysaccharides may alleviate exercise-induced fatigue through coordinated regulation of energy metabolism, oxidative stress, and inflammation, providing a mechanistic framework linking polysaccharide composition to anti-fatigue effects.