20-day and 60-day feeding trials were conducted respectively on healthy Penaeus vannamei PL10 (n=3500, triplicate) and PL25 (n=350, triplicate) to evaluate the effects on growth and health parameters of a marine probiotic consortium (MPC) made of four marine Bacillus strains encapsulated in algae, used as dietary supplement.
At the end of the 60-day trial, the treatment with MPC at 1% significantly increased final body weight, weight gain, specific growth rate, feed conversion ratio of White Shrimp P. vannamei (P < 0.05). MPC also significantly enhanced the mRNA expressions of digestive genes in hepatopancreas, such as Trypsin, α-Amylase, Triacylglycerol lipase and Chymotrypsin BII; of immune-related genes, such as proPO, crustin gene in hepatopancreas and Dual Oxidase, mucin-like peritrophin, Penaeidin-3α in intestine genes (P < 0.05). Diets supplemented with MPC also decreased the occurrence of total Vibrio spp. count in shrimp’s hepatopancreas under normal conditions. Under challenge conditions, MPC at 5% significantly increased disease resistance of shrimp larvae against V. parahaemolyticus (VpAHPND) (P < 0.05).
The results of high-throughput sequencing showed a significant improvement in White Shrimps digestive tract bacterial communities with probiotic supplementation. Moreover, the MPC enhances the hepatopancreas gene pathway related to metabolisms of endocrine system, immune system and digestive system. In addition, the beneficial effects observed in intestine gene pathway are mainly related to translation, transport catabolism, and signal transduction.
In conclusion, this study demonstrated the ability of the marine Bacillus spp. consortium encapsulated in algae to improve White Shrimp growth performance, digestive tract and immune status and disease resistance during both larval and grow-out phases.