Dietary administration of Bacillus and yeast probiotics improves the growth, survival, and microbial community of juvenile whiteleg shrimp, Litopenaeus vannamei

Several microorganisms, including Bacillus and yeasts species, are widely used as aquaculture probiotics. In the present study, a mixed Bacillus sp. contained five species of B. thuringiensis BUU 001, B. megaterium BUU 002, B. polymyxa BUU 003, B. licheniformis BUU 004, and B. subtilis BUU 005, and a mixed yeast probiotics contained Debaryomyces hansenii BUU 01 and Rhodotorula sp. BUU 02. The effects of mixed microbial probiotics as a dietary supplement on growth, survival, and microbiological changes of juvenile whiteleg shrimp (Litopenaeus vannamei) were investigated. Shrimp (similar to 5.7-5.8 g) were fed a commercial diet alone (control) or with one of three probiotic supplements-freeze-dried mixture of Bacillus (FB), freeze-dried mixture of Bacillus and yeast (FBY), and freeze-dried mixture of yeast (FY)-for 90 days in simulated earthen ponds. Growth of FB-fed shrimp was significantly higher (P < 0.05) than those fed with FBY, FY, and control diets. However, survival was not significantly different (P > 0.05) among the three treated groups but was significantly higher (P < 0.05) than that of the control. Numbers of culturable heterotrophic bacteria in intestine were not significantly different (P > 0.05) among the four groups. Bacillus numbers in FB- and FBY-fed shrimp increased significantly (P < 0.05) in intestine. Yeast numbers in intestine of FBY- and FY-treated shrimp were significantly higher (P < 0.05) than those of FB-treated and control shrimp and increased significantly (P < 0.05) during the rearing period, while no yeast was observed in FB-treated and control shrimp. Numbers of Vibrio in intestine were significantly lower (P < 0.05) in the three treated groups than the control. Administration of mixed Bacillus, mixed yeasts, or Bacillus mixture in combination with mixed yeasts resulted in improved (P < 0.05) growth and survival and reduced Vibrio numbers along with an increase in beneficial probiotic abundance and a decrease in the number of potential pathogenic bacteria (V. parahaemolyticus and V. cholerae) in digestive tract of juvenile L. vannamei.