Dietary supplementation with the hexane fraction of Ulva fasciata extract improves growth performance, immune responses, and antioxidant status in Nile tilapia (Oreochromis niloticus).

This study aimed to evaluate the effects of dietary supplementation with the hexane fraction of Ulva fasciata extract (UH) on growth performance, immune responses, and antioxidant status in Nile tilapia (Oreochromis niloticus). Nile tilapia fingerlings (initial weight 3.13 ± 0.03 g) were fed diets supplemented with 0, 50, 100, or 150 mg kg⁻1 UH for 60 days. The findings demonstrated that dietary supplementation with the hexane fraction of Ulva fasciata extract (UH150, UH100, and UH50) significantly increased final weight gain, specific growth rate, and improved feed conversion ratio compared to UH0 (control diet). According to the intestinal villi histomorphometric evaluation, fish that received UH exhibited improvements in villi length, goblet cell numbers, and intervillous spaces, particularly in UH100 (p < 0.05). However, UH150 demonstrated the most significant improvements in villi width. The highest WBC counts, phagocytic activity, lysozyme activity, superoxide dismutase and catalase activity-alongside normal ranges for hematological and biochemical parameters-were detected in fish that received 100 mgkg-1 UH. The Ulva hexane fraction extract meals at 50, 100, and 150 mg kg-1 triggered upregulation of growth hormone receptor (GHr), insulin-like growth factor (IGF-1), myostatin (MSTN), tumor necrosis factor alpha (TNF-α), heat shock protein 70 (HSP 70), fatty acid synthase (FAS), and lipoprotein lipase (LPL) with the best results being stated in UH150. In conclusion, UH dietary inclusion improved growth performance, feed utilization efficiency, and immune-physiological response of Nile tilapia.