不同比例复合益生菌对凡纳滨对虾生长、免疫及抗氨氮能力的影响

对从凡纳滨对虾(Litopenaeus vannamei)肠道中分离出的鲍鱼希瓦氏菌(Shewanella haliotis)、蜡样芽孢杆菌(Bacillus cereus)和双壳气单胞菌(Aeromonas bivalvium)3株有益菌株,利用正交设计得到9种复合比例,通过饲料中添加上述9种比例混合的菌体(菌数总量为109 cfu/g)饲喂凡纳滨对虾,经过28 d养殖实验,评价其对凡纳滨对虾生长、免疫指标的影响。随后,利用氯化铵调节水体氨氮浓度至26.67 mg/L,经过16 d的氨氮毒性实验,研究不同比例复合益生菌对凡纳滨对虾抗氨氮能力的影响。研究结果表明,9个复合益生菌实验组的增重率和特定生长率均显著高于对照组(P0.05),并且以3株菌菌数6︰1︰3比例效果较好;不同配比的复合益生菌能够显著提高酸性磷酸酶(ACP)、碱性磷酸酶(ALP)、总超氧化物歧化酶(T-SOD)活力(P0.05),并表现出了不同的影响效果,其中,3株菌菌数(菌数总量为109 cfu/g,下同)2︰3︰3、4︰2︰3及6︰1︰3比例对ACP活力具有显著促进作用(P0.05),3株菌菌数4:2︰3和6︰1︰3比例对ALP活力具有显著促进作用(P0.05);3株菌菌数2︰1︰1比例对T-SOD活力具有显著促进作用(P0.05);各比例的复合菌对溶菌酶活力的影响不显著(P0.05);氨氮浓度26.67 mg/L条件下,不同比例复合菌组对虾累计存活率显著高于对照组(P0.05),其中以3株菌菌数4︰3︰1和6︰3︰2比例组累计存活率较高,即抗氨氮效果较好。

Effects of different proportions of a group of compound bacteria on growth, innate immunity, and ammonia nitrogen resistance in Pacific white shrimp, Litopenaeus vannamei

Nine different proportions of a group of bacteria, including <i>Shewanella haliotis</i>, <i>Bacillus cereus</i>, and <i>Aeromonas bivalvium </i>were isolated from the gut of Pacific white shrimp, <i>Litopenaeus vannamei. </i>The shrimp were fed fodder with 10⁹cfu/g compound bacteria for 28 d using an orthogonal experimental design, and the effects on growth and innate immunity of the shrimp were assessed. Ammonia-nitrogen was adjusted to 26.67 mg/L with NH₄Cl after 16 d, and ammonia-nitrogen resistance of the shrimp was tested. The results show that shrimp growth improved after the 28 d probiotic feeding regime, compared to that of the control (<i>P</i><0.05), and the 6:1:3 proportion was better than the others. These results suggest that the compound bacteria promoted growth through secretion of nutrients and improved feed digestibility. Moreover, the positive effects of the compound bacteria on innate immunity and ammonia-nitrogen resistance of <i>L. vannamei </i>were eventually expressed as improved growth. The activities of acid phosphatase (ACP), alkaline phosphatase (ALP), and total superoxide dismutase (T-SOD) were also enhanced compared to those in the control (<i>P</i><0.05), but the effects were different. The 2:3:3, 4:2:3, and 6:1:3 proportions increased ACP activity significantly more than the others (<i>P</i><0.05), and the 4:2:3 and 6:1:3 proportions increased ALP activity significantly more than the others (<i>P</i><0.05). The 2:1:1 proportion increased T-SOD activity significantly more than the others. No changes in shrimp serum lysozyme activity were detected in any of the bacteria-tested groups compared to the control. The results that serum ACP, ALP, and T-SOD activities were enhanced compared to the control show that the different proportions of bacteria positively affected shrimp innate immunity. In addition, the 4:3:1 and 6:3:2 bacterial proportions significantly enhanced ammonia-nitrogen resistance in Pacific white shrimp (<i>P</i><0.05). These results show that the compound bacteria had positive effects on ammonia-nitrogen resistance of <i>L. vannamei </i>and suggest that ammonia-nitrogen resistance is associated with the immune system.