Abstract:In this culture experiments of Litopenaeus vannamei, we explore the effect of compound probiotics on the ability of L. vannamei to resist Vibrio parahaemolyticus infection at different experimental stages. One strain of Bacillus licheniformis (BL-9), one B. subtilis (BS-12), and one Pseudoalteromonas flavipulchra (CDM8) were selected to make up a compound of probiotics at the same concentration (107 CFU/ml). The effect of compound probiotics on the V. parahaemolyticus infection of L. vannamei was observed by adding the compound probiotics to the culture water of the L. vannamei. The experiment took place over 30 d, including a temporary period (7 d), a probiotics immersion period (15 d), and a V. parahaemolyticus infection period (10 d). The experiment results showed that the addition of compound probiotics in the culture water could significantly increase the total number of bacteria culture in the water and the intestinal tract of L. vannamei (P<0.05). The cumulative survival rate of shrimp in the experimental group was (73.33±6.83)% at the end of the infection periodwhich was significantly higher than that of the positive control group (25.33±15.43)%. The disease-resistant-related gene: heat shock protein 70 (Hsp70), β-1,3-glucan binding protein-lipoprotein (βGBP-HDL), lipopolysaccharide-β-1, 3-glucan binding protein(LGBP), crustin, and immune related enzymes catalase (CAT), was up-regulated by different degrees in the probiotics immersion phase. And all the genes up-regulated extensively during the V. parahaemolyticus infection stage, but expressed at different levels. The results suggested that the compound probiotics with BL-9, BS-12, and CDM8 in water could improve the ability of shrimp to resist V. parahaemolyticus infection. The increase of disease resistance of L. vannamei may be related to the colonization of probiotics in the intestinal tract, and the expression level of disease resistance related genes and catalase activity in L. vannamei. It is hoped that the results of this study can provide a reference for the application of compound probiotics in the cultivation of L. vannamei.
