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

Abstract

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 (~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.