In the present study, the effects of β-glucan administration in water on growth performance and blood status (hematological indexes, immunological and biochemical parameters) were evaluated in Nile tilapia fingerlings (Oreochromis niloticus) under hypoxia-induced stress. In parallel, effect of this prebiotic (beta-glucan) was evaluated on gut microbiota diversity (16S rRNA gene) under normal oxygenation condition. Three treatments were implemented according to beta-glucan water supplementation: 0 (control), 0.1 and 0.3 mg L⁻¹. Blood was collected before hypoxic challenge (BHC) and 9 h after hypoxic challenge (AHC). No significant differences were observed according to growh performance parameters. A significant increase in erythrocyte number and decrease in mean corpuscular volume (P < 0.05) were identified in control group when were under hypoxia. The plasma glucose level was higher in the 0.3 group than in the 0.1 group BHC; however, for all groups, the glucose level increased markedly AHC, and then receded seven days AHC (7AHC, P < 0.05). Total protein, serum lysozyme, plasma lactate, triglyceride, and cholesterol concentrations did not differ between groups. Comparison of the two β-glucan concentrations indicated that the 0.3 mg L⁻¹ concentration promoted an increase in lymphocyte count. The 0.1 group showed the highest survival rate 7 days after hypoxia. Metagenomic analysis revealed a greater number of operational taxonomic units (OTUs) in the 0.1 and 0.3 groups. The Chao richness value was higher in the 0.1 group than in the control group (P < 0.05), with a greater abundance observed for members of the Vibrionaceae family. It is concluded that the concentration of 0.1 mg L⁻¹ was able to increase tolerance to hypoxia, increasing the survival rate and regulating glucose levels. The concentration of 0.3 mg L⁻¹ modulated hematological responses under stress and increased the lymphocyte count before hypoxic challenge.

在本研究中，在缺氧诱导的胁迫下，对尼罗罗非鱼鱼种（Oreochromis niloticus）评估了水中添加β-葡聚糖对生长性能和血液状态（血液学指标，免疫学和生化指标）的影响。同时，在正常充氧条件下评估了该益生元（β-葡聚糖）对肠道菌群多样性（16S rRNA基因）的作用。根据β-葡聚糖水补充剂实施了三种处理：0（对照），0.1和0.3mg L ^-1。在低氧激发（BHC）之前和低氧激发（AHC）之后9小时收集血液。根据生长性能参数未观察到显着差异。红细胞数量显着增加，平均红细胞体积减少（ 缺氧时在对照组中P <0.05）。0.3组的血浆葡萄糖水平高于0.1组的BHC。但是，对于所有组，血糖水平均显着升高，然后下降至7天（7AHC，P  <0.05）。两组之间的总蛋白，血清溶菌酶，血浆乳酸，甘油三酸酯和胆固醇浓度无差异。两种β-葡聚糖浓度的比较表明0.3mg L ^-1浓度促进淋巴细胞计数的增加。0.1组在缺氧7天后显示出最高的存活率。元基因组学分析显示，在0.1和0.3组中有更多的操作分类单位（OTU）。0.1组的Chao丰富度值高于对照组（P  <0.05），弧菌科成员的丰度更高。结论是：0.1 mg L ^-1的浓度能够增加对缺氧的耐受性，提高存活率并调节葡萄糖水平。0.3 mg L ^-1的浓度可调节应激状态下的血液学反应，并在缺氧攻击前增加淋巴细胞计数。