Abstract: To investigate the effects of dietary lactic acid bacteria on the growth, meat quality, flavor compounds and antioxidant capacity of Sunit sheep, 24 lambs were equally allocated into two groups, which were fed a basic diet alone or supplemented with lactic acid bacteria (LAB). The growth performance of lambs, and the numbers of lactic acid bacteria and Escherichia coli in the intestine were evaluated. Following slaughter, Longissimus dorsi muscles were taken to measure meat quality, volatile flavor substances, antioxidant capacity and the expression of antioxidant enzymes genes. The results showed that the number of LAB in the intestinal tract of the LAB supplementation group was significantly higher than that in the control group (P < 0.05), while the number of E. coli was significantly lower than that in the control group (P < 0.05). The addition of LAB increased the average daily mass gain of Sunit sheep (P < 0.05). Shear force, b* value and pH24 h in the LAB group were significantly lower than those in the control group (P < 0.05), while there was no statistical difference in pH45 min or cooked meat rate between the two groups (P > 0.05). LAB could affect the composition and relative contents of flavor compounds in Sunit lamb meat. The relative contents of the major lipid oxidation products octanal, nonanal, decanal, 1-pentanol, 1-hexanol, and 1-heptanol were significantly lower in the LAB group than in the control group (P < 0.05), which indicates that LAB can inhibit excessive lipid oxidation in muscle tissue and impart a well-balance meat flavor. Compared with control group, adding lactic acid bacteria to the diet imparted orange-like, onion-like, rosy and mushroom-like flavors. Catalase (CAT) activity and total antioxidant capacity (T-AOC) in the LAB group were significantly higher than those in the control group (P < 0.05), and the activity of glutathione peroxidase (GPx) was higher than that in the control group without statistical significance (P > 0.05). According to the analysis of antioxidant enzyme gene expression, the expression levels of CAT and GPx genes were significantly higher than those in the control group (P < 0.05), proving that the addition of LAB to the diet could improve the antioxidant capacity of lamb meat. In summary, the dietary addition of LAB can improve the intestinal microbiota in Sunit lambs and meat flavor, and enhance growth performance, meat quality and antioxidant capacity.

Key words: lactic acid bacteria; Sunit sheep; growth; meat quality; volatile flavor substances; antioxidant capacity