The present study aimed to investigate the growth, disease resistance and immune function of tilapia (Oreochromis niloticus) fed diets containing Enterococcus faecalis at levels of 0 (CG), 1 × 10⁵ (EF1), 1 × 10⁶ (EF2), 1 × 10⁷ (EF3) or 1 × 10⁸ CFU/g diet (EF4) for 56 days. The results showed that the EF3 group exhibited significantly increases in the final weight, weight gain and specific growth rate and a significantly decreased feed conversion ratio compared with those obtained from the CG group. The cumulative mortality was significantly decreased in the EF2, EF3 and EF4 groups. Serum alkaline phosphatase activity and tumour necrosis factor α gene expression in the hindgut were significantly increased in the EF1, EF2 and EF3 groups, and the serum complement 3 (C3) and C4 contents were significantly increased in the EF2, EF3 and EF4 groups. The gene expression of interleukin receptor-associated kinase-4, Toll-like receptor 2 and myeloid differentiation factor 88, claudin1 and interleukin 8 were significantly upregulated in all EF groups, and the activity of diamine oxidase was significantly reduced in the EF3 and EF4 groups. The gene expression of occludin was significantly upregulated in the EF1 and EF3 groups, and that of interleukin 10 was significantly upregulated in the EF3 group. No differences in serum lysozyme, d- lactic acid or endotoxin were found among the groups. These results showed that the optimal level of dietary E. faecalis enhanced the growth performance and disease resistance, and those effects might be related to increased humoural and intestinal immunity in tilapia. The optimal supplementation level of dietary E. faecalis for tilapia was found to be 1 × 10⁷ CFU/g.

本研究旨在调查以粪便肠球菌为0（CG），1×10 ⁵（EF1），1×10 ⁶（EF2），1的粪便罗非鱼（Oreochromis niloticus）喂养的日粮的生长，抗病性和免疫功能。×10 ⁷（EF3）或1×10 ⁸ CFU / g饮食（EF4），持续56天。结果表明，与从CG组获得的结果相比，EF3组的最终体重，增重和比生长速率显着增加，饲料转化率显着降低。EF2，EF3和EF4组的累积死亡率显着降低。血清碱性磷酸酶活性与肿瘤坏死因子αEF1，EF2和EF3组后肠中的基因表达显着增加，而EF2，EF3和EF4组中血清补体3（C3）和C4含量显着增加。在所有EF组中，白介素受体相关激酶4，Toll样受体2和髓系分化因子88，claudin1和白介素8的基因表达均显着上调，而EF3和EF4组中二胺氧化酶的活性显着降低。 。在EF1和EF3组和白细胞介素10中，occludin的基因表达明显上调。在EF3组中明显上调。各组之间血清溶菌酶，d-乳酸或内毒素无差异。这些结果表明，最佳粪便大肠杆菌水平可提高其生长性能和抗病能力，这些作用可能与罗非鱼的体液和肠道免疫力提高有关。粪便中罗非鱼的最佳添加量为1×10 ⁷ CFU / g。