Multiple-strain probiotics appear to be more effective in improving the growth performance and health status of white shrimp, Litopenaeus vannamei, than single probiotic strains.

The probiotic efficiencies of the mixed probiotics containing Lactobacillus pentosus BD6, Lac. fermentum LW2, Bacillus subtilis E20, and Saccharomyces cerevisiae P13 for shrimp growth and health status improvement were better than those when using single probiotics. The probiotic mixture at a level of 108 colony-forming units (cfu) (kg diet)-1 and the diets containing BD6 and E20 at 109 cfu (kg diet)-1 significantly improved the growth and health status of shrimp, whereas the diets containing P13 or LW2 did not significantly affect the growth of shrimp. No significant difference in the carcass composition was recorded among the control and treatments. After 56 days of feeding, shrimp fed the diet containing the probiotic mixture (107∼109 cfu (kg diet)-1) had higher survival after injection with the V. alginolyticus, but 109 cfu (kg diet)-1 of single probiotics (except for S. cerevisiae P13) had to be administered to improve shrimp survival. The better disease resistance of shrimp in groups fed the probiotic mixture might have been due to increased phenoloxidase activity, respiratory bursts, and lysozyme activity of hemocytes. Therefore, we considered that the probiotic mixture could adequately provide probiotic efficiency for white shrimp, and a diet containing 108 cfu (kg diet)-1 probiotic mixture is recommended.