Abstract:Current shrimp farming industries face difficulties associated with disease outbreak caused by pathogens on shrimp larva. The application of probiotics may provide a solution to problems associated with disease. We used Pseudoalteromonas sp. strain KL-3 2010, which has antagonism against acute hepatopancreatic necrosis disease-causing Vibrio parahaemolyticus (VPAHPND) and extracellular protease activity, and Exiguobacterium sp. strain KL-C2 2014, which has extracellular protease activity, as probiotics in a feeding test of Litopenaeus vannamei to investigate their effects on the growth and survival of shrimp. These two bacterial strains had no pathogenicity to L. vannamei in an immersion challenge at 108 CFU/ml. Weak positive signals for white spot syndrome (WSSV), VPAHPND, and Enterocytozoon hepatopenaei (EHP) were detected in the population of shrimp juveniles used in this study. L. vannamei was fed for 60 days with Pseudoalteromonas sp. KL-3 2010-supplemented diets (P group), Exiguobacterium sp. KL-C2 2014-supplemented diets (E group), alternation of the two diets (PE group), and normal diets (C group), respectively. Compared with the control group, the survival rate of the P group significantly improved (by 213%±43%; P<0.01), the average growth rate of E group significantly increased (by 105.5%±28.1%; P<0.05), and the survival rate and average growth rate of the PE group simultaneously improved (by 184%±52%; P<0.05 and by 70.6%±32.8%, respectively). Feeding with Pseudoalteromonas sp. KL-3 2010 and Exiguobacterium sp. KL-C2 2014 diets significantly affected the species of dominant microflora colonizing the shrimp gut, but these added probiotic bacterial strains were not detected in the re-isolated and cultivated dominant bacteria colonies. The addition with these probiotics to diets significantly increased some serum immune indexes, such as superoxide dismutase. The study showed that diets supplemented with the above probiotics may provide a practical approach for disease prevention and growth promotion in shrimp farming, even for shrimp positive for multiple pathogens.
