Abstract:[Objective] To investigate the effect of supplementing a probiotic mixture (Bacillus licheniformis, B. subtilis, and Clostridium butyricum) in drinking water on the meat quality of broilers and explore the underlying mechanism. [Methods] A total of 360 1-day-old white feather broilers were randomly selected and assigned to control (CON, normal drinking water), low-dose probiotic (LG, drinking water supplemented with 0.2% probiotic mixture), and high-dose probiotic (HG, drinking water supplemented with 0.4% probiotic mixture) groups. The experiment lasted for 42 days. [Results] Compared with the CON group, the LG and HG groups showed increased average body weight on days 7, 35, and 42. The HG groups increased average daily gain during days 21-28, 28-35, and 35-42, while the LG groups increased average daily gain during days 35-42. LG and HG significantly increased the chest muscle redness at the time points of 45 min, 24 h, and 48 h and the chest muscle yellowness at the time point of 24 h, decreased the brightness at 24 h and 48 h and the dripping and cooking loss at 48 h. The HG group had higher content of crude protein and crude fat in chest muscle than the CON group and no significant difference compared with the LG group. Both LG and HG groups reduced the ash content of chest muscle. The addition of the probiotic mixture significantly increased total antioxidant capacity (T-AOC), while the levels of total-superoxide dismutase (T-SOD) and catalase (CAT) had an increasing trend. The expression levels of CAT, SOD-1, Keap1, and Nrf2 were significantly up-regulated, and the HG group had higher expression levels of SOD-2 and HO-1 than the LG group. The concentrations of acetic acid, propionic acid, butyric acid, and valeric acid in cecum on days 21 and 42 significantly increased in LG and HG groups. [Conclusion] The probiotic mixture enhanced the growth performance and meat quality of broilers by increasing the levels of antioxidant activity and short-chain fatty acids, and the HG group outperformed the LG group.