The beneficial effects of Bacillus subtilis C-3102 and Saccharomyces cerevisiae type 1 were tested in red sea bream (Pagrus major) feeds. A basal diet (control) and two other diets were prepared by supplementation with B. subtilis C-3102 (PB) or S. cerevisiae type 1 (PY). After 60 days, both probiotic-supplemented groups exhibited significant enhancement in growth performance, the protein efficiency ratio (PER), and digestive enzyme secretion (protease and amylase) compared to the control group (P<0.05). The anterior, middle, and posterior parts of the intestines exhibited significantly increased values of intestinal fold height (hF), enterocyte height (hE), and microvillus height (hMV) in fish fed PB- or PY-supplemented diets (P<0.05). Serum peroxidase, anti-protease, and bactericidal activities were enhanced significantly in both probiotic-treated groups compared to the control group (P<0.05). Serum and mucus lysozyme activities improved significantly in the PB group compared to the control group (P<0.05). Catalase activity was also significantly decreased in both probiotic groups, with relatively lower activity observed in the PY group (P<0.05). Both probiotic groups showed considerably increased tolerance to freshwater exposure (P<0.05). In conclusion, B. subtilis C-3102 and S. cerevisiae type 1 can be used as functional probiotics to enhance the growth performance, digestion capacity, gut morphology, immune response, and stress resistance of the red sea bream with relatively higher efficiency by B. subtilis C-3102.
