Effects of dietaryLactobacillus plantarumin different treatments on growth performance and immune gene expression of white shrimpLitopenaeus vannameiunder normal condition and stress of acute low salinity
A 45-day feeding trial followed by an acute stress test of low salinity was done to evaluate effects of Lactobacillus plantarum on growth performance and anti-stress capability of white shrimp (Litopenaeus vannamei). Shrimp were randomly allocated in 15 tanks (100 shrimp per tank) and divided into 5 treatments with 3 replicates. Triplicate tanks were fed with a control diet or diets containing different treatments of L. plantarum (fermentation supernatant (FS), live bacteria (LB), dead bacteria (DB) and cell-free extract (CE) of L. plantarum) as treatment groups. Growth performance including weight gain (WGR), feed conversion ratio (FCR) and specific growth rate (SGR) were determined after feeding 45 days. Anti-stress capacity was evaluated by determining the gene expression of ProPO, SOD and Lys in gut of shrimp at the end of feeding trial and again at 96 h post-stress test. Results indicated that supplementation of L. plantarum into diet had significantly improved growth performance of L. vannamei. On the other hand, L. plantarum supplementation had no significant effects on the gene expression of SOD and Lys in gut of shrimp cultured under normal condition for 45 days. Supplementation of L. plantarum had increased survivability of L. vannamei having higher survival rates compared to the control group. However, statistical analysis showed no significant difference between the control group and treatments. Compared with the control group, supplementation of L. plantarum significantly improved the resistance of L. vannamei against the stress of acute low salinity, as indicated by higher survival rate as well as higher transcript levels of ProPo, SOD and Lys gene. Our findings suggested that L. plantarum, especially cell-free extract of L. plantarum has improved the anti-stress capacity of L. vannamei and could serve as a potential feed additive that helps shrimp to overcome environmental stresses.