| In recent years, the diseases in prawn aquaculture are frequent, that hinder the healthy development of aquaculture. After antibiotic was banned, people urgently need effective technology to enhance the shrimp immunity so as to enhance the premunition prawn. Probiotics can improve cultivation environment, promote shrimp growth and enhance prawn immunity, so they are widely used in shrimp aquaculture. The study on screening two potential probiotic bacteria included Bacillus, sp (BZ5 strain) and Vibrio alginolyticus (VZ5 strain), explores their security and effect of their growth, immune related enzyme activities of Litopenaeus vannamei and disease resistance, in order to provide the theoretical basis and technology support for the application of probiotics in shrimp aquaculture. In this study, the main research contents include:1 by hemolysis test, drug sensitive test, injection and immersion experiment, we explore safety problems for shrimp and culture environment; 2 Bacillus, sp (BZ5 strain) and Vibrio alginolyticm (VZ5 strain) soaking with different concentration in the aquaculture water affect shrimp growth, digestive enzyme activity, immune related enzyme activity and disease resistance; 3 In comparison of injection method, Bacillus, sp (BZ5 strain) and Vibrio alginolyticus (VZ5 strain) soaking with different concentration in the aquaculture water affect shrimp growth, digestive enzyme activity, immune related enzyme activity and disease resistance, so we find the optimum concentration; 4 In comparison of immersion method, Bacillus, sp (BZ5 strain) and Vibrio alginolyticus (VZ5 strain) soaking with different concentration in the aquaculture water affect shrimp growth, digestive enzyme activity, immune related enzyme activities and the ability of anti-WSSV.In this study, the main results are as follows.1. By hemolysis test, drug sensitive test, Bacillus, sp (BZ5 strain) and Vibrio alginolyticus (VZ5 strain) can’t casue hemolysis phenomenon; BZ5 strain is highly sensitive to cefalexin. cefazolin. cefradine and other 14 kinds of antibiotics, and VZ5 strain is highly sensitive to neomycin, erythromycin and other four kinds of antibiotics, is moderately sensitive to piperacillin, cephalexin, cefazolin and other 8 antibiotics, so the two probiotic are safe that used by the aquaculture environment; It finds that BZ5 strain and VZ5 strain by infection and immersion have no apparent toxic effect upon Litopenaeus vannamei in the concentration of 106cfu/mL.2. By soaking of different concentrations of Bacillus, sp (BZ5 strain) and Vibrio alginolyticus (VZ5 strain),it is found that:(1) the survival and growth rate of Litopenaeus vannamei increased significantly in VZ5 strain of 104 cfu/mL, and the final weight and survival rate increased by 70.45% and 19.23% respectively than the control group reaching (9.00g±0.36g) and (86.11%±6.80%) respectively. VZ5 strain with a concentration of 104cfu/mL can promote the growth of shrimp, which increased 26.70% than the control group and shrimp final weight reached (6.69g±0.21g). VZ5 strain with a concentration of 108cfu/mL could improve the survival rate of shrimp (91.67%±9.13%), compared with the control group increased 26.93%.;(2) The activities of trypsin and amylase in all groups are significantly higher than the control group (P<0.05) as a whole. Overall, the effects of BZ5 strain with a concentration of 106cfu/mL and VZ5 strain with a concentration of 106cfu/mL in the water that add L. vannamei digestive enzyme activities are obvious;(3) The activities of SOD, POD, atimicrobial enzymes and PO in all groups are significantly higher than the control group (P<0.05) as a whole. Overall, the effects of BZ5 strain with a concentration of 106cfu/mL and VZ5 strain with a concentration of 106cfu/mL in the water that promote immune-related enzymes activities are obvious; (4) Attacked by WSSV, lethal time of 50%(LT50) in BZ5104cru/mL group, VZ5106cfu/mL group, VZ5 108cfu/mL group are longer by 29.49%,15.39%,1.28% respectively than the control group, while the cumulative mortality in BZ5106cfu/mL group at the time of 168h is 45.45%. Experimental results show that BZ5 strain with a concentration of 106cfu/mL and VZ5 strain with a concentration of 106cfu/mL in the water can promote the ability of anti-WSSV.3. By infected and immersed the same concentration of BZ5 strain and VZ5 strain to Litopenaeus vannamei, it is found:(1) The activities of trypsin,amylase and lipase in alginolyiicus group and Bacillus group are significantly higher than the control group (P<0.05) as a whole, what’s more, the activities of trypsin,amylase and lipase in BZ5 strain are higher than the BZ5 strain as a whole;(2) The activities of SOD, POD, atimicrobial enzymes and PO in BZ5 strain and VZ5 strain are significantly higher than the control group (P<0.05) as a whole, what’s more, the activities of SOD, POD, atimicrobial enzymes and PO in BZ5 strain are higher than the BZ5 strain as a whole;(3) Attacked by WSSV, the length of lethal time of 50%(LT50):V. harveyi group<control group<alginolyticus group<Bacillus group. In the infected experiment the lethal time of 50%(LT50) in alginolyticus Group and Bacillus group are longer by 27.38% and 21.43% respectively than the blank group.In the immersed experiment, the lethal time of 50%(LT50) in alginolyticus Group and Bacillus group are longer by 24.73% and 8.60% respectively than the blank group.Experimental results show that BZ5 strain and VZ5 strain infected to Litopenaeus vannamei can promote digestive enzyme activities, immune-related enzymes activities and the ability of anti-WSSV. Experimental results show that BZ5 strain with a concentration of 10 cfu/mL immersed to Litopenaeus vannamei in the water can promote digestive enzyme activities, immune-related enzymes activities and the ability of anti-WSSV. |
PDF Full Text Request