The influence of continuous and intermittent Bacillus subtilis AQUA-GROW® application on the white leg shrimp, Litopenaeus vannamei, immune-related genes

In the framework of fact, prolonged and excessive use of probiotics has been implicated in immunosuppression. The realization of immuno-stimulants frequent application impacts is the groundwork for tactical protection of shrimp culture. Therefore, changes in the gene expression of five immune attributable genes (prophenoloxidase, serine proteinase, transglutaminase, lysozyme; and superoxide dismutase) of Bacillus subtilis supplemented shrimp, Litopenaeus vannamei over a period of time (12 weeks) were assessed before and after Vibrio parahaemolyticus bacterial challenge. L vannamei of weight measured 0.78±0.08 (SE) was randomly divided into three groups. Frist group (T1) was the normalizing group (control) fed plain diet, the second group (T2) fed B. subtilis supplemented diet daily, the third group provided B. subtilis supplemented diet followed by basal diet changeably week after week. The findings before bacterial challenge manifested that proPO of (T2) expressed significantly in 1^st, 2^nd, 4^th, and 7^th weeks. In (T2) SP expressed highly in the 2^nd and 7^th week. proPO,  SP, TGase, and LYZ of (T3) presented significant up-regulation in the 7^th week. TGase of (T2) and SOD of (T3) expression levels increased significantly in 4^th and 7^th weeks. LYZ and SOD of (T2) expression levels increased significantly in the 2^nd, 4^th, 7^th weeks. In response to induced infection, proPO of (T2) and (T3) proPO, SP, and SOD expression levels were observed to respond to bacterial infection at early and late infection phases 3 and 24 (hpi). This work suggested that the transient application of B. subtilis for shrimp L. vannamei enhances the immune system, and their immune status is poised and all set against V. parahaemolyticus by rapid and early defensive responses.