Dietary probiotic Bacillus OJ and isomaltooligosaccharides influence the intestine microbial populations, immune responses and resistance to white spot syndrome virus in shrimp (Litopenaeus vannamei)

In order to reveal the potential of Bacillus OJ (PB) as probiotic and the synergistic effects of PB and isomaltooligosaccharides on intestine microbial populations, immune responses and disease resistance of shrimp (Litopenaeus vannamei), a 28-day feeding experiment was conducted in shrimp by feeding PB at doses of 0, 108, and 1010 CFU/g feed with or without 0.2% isomaltooligosaccharides in shrimp diets. After a 14-day feeding experimental period, six shrimp per tank were sampled for bacterial quantification and immunity determination. Then all the shrimp left were challenged by white spot syndrome virus. Results showed that, with the increasing doses of PB in diets, shrimp survivals and immune parameters generally increased whereas the counts of total viable bacteria and Vibrio decreased. Shrimp fed with PB at dose of 1010 CFU/g of feed produced significantly higher survivals and immune parameters than the control groups. Although the effect of 0.2% isomaltooligosaccharides alone was negligible, 0.2% isomaltooligosaccharides in combination with 108 CFU/g feed PB produced significantly positive synergistic effects on shrimp immune responses and disease resistance. While the doses of PB increased to 1010 CFU/g feed, the synergistic effects significantly decreased. Then, our results confirm the potential of PB as dietary probiotic and the synergistic effects of PB and isomaltooligosaccharides in shrimp.