The primary goal of this trial was to examine how Paulownia leaf extract (PLE) dietary supplementation affected performance, feed utilization and efficiency, redox status, immunological responses, intestinal microbial content, and disease resistance of Oreochromis niloticus. Nile tilapia fry (0.52 ± 0.19 g) were fed four formulated diets enriched with graded amounts of PLE at 0.0, 0.25, 0.5, and 1 g kg−1 diet, respectively, for 60 days. At the end of the feeding trial, fish were intraperitoneal injected with Aeromonas hydrophila then the survival percentage was recorded daily and calculated mortality rate in all treated groups for 14 days. The performance findings showed that enriched tilapia diets with modest levels of PLE (0.25 or 0.5 g kg−1) substantially enhanced performance, consumed feed, feed efficiency, and feed utilization parameters compared to the control and other treatment groups, whereas the total serum protein and globulin concentrations were significantly (P < 0.001) higher in the fish provided a small quantity of PLE (2.5 g kg-1 diet) than in the control group. Compared to other treatment groups, all estimated liver enzymes and kidney function indicators improved significantly (P < 0.001) at PLE0.5, followed by PLE2.5, whereas the digestive enzymes’ activity increased significantly (P < 0.001) with increasing PLE level up to 0.5 g/kg diet compared to the un-supplemented group. In the same context, enriched tilapia diets with 0.5 g PLE/kg significantly (P < 0.001) boosted redox status and innate immune parameters as compared to other groups. Furthermore, increased PL inclusion levels in tilapia diets significantly (P < 0.05) increased crude protein and ash contents while decreasing fat levels in fish flesh. Moreover, fortified tilapia diets with high PLE levels significantly enhanced the survival percentage and diminished the development of all gram-negative intestinal microbial content. Finally, the results strongly recommend enriched tilapia diets with 0.25 or 0.5 g /Kg for promoting performance and health status.
