Abstract
The current investigation evaluated the impact of the dietary addition of commercial bile acids (BAs) on growth, nutrient assimilation, immunity, antioxidant status, intestinal and hepatic histomorphometry, and gene expression of lipid metabolism in Nile tilapia (Oreochromis niloticus). In a study conducted for seventy days, 180 healthy fingerlings weighing 9 ± 0.5 g were divided into 18 hapas measuring 0.7 × 0.7 × 1.0 m. The fish were fed on six meals enriched with varied amounts of BAs: 0.0 (D1), 0.1 (D2), 0.2 (D3), 0.3 (D4), 0.4 (D5), and 0.5 (D6) g/kg diet. Nile tilapia fed the D3 diet exhibited significantly enhanced growth performance, with a specific growth rate of 1.89%/day and had the greatest feed conversion ratio (1.25), protein productive value, and energy utilization (33.28%). Fish fed the D3 exhibited significantly the highest crude protein content (64.50%). Energy content varied significantly, with D1 showing the lowest value (533.34 Kcal/100 g) and D3 the highest (604.27 Kcal/100 g). D3 improved biochemical indicators, immunological parameters, and digestive enzymes of O. niloticus. Histological analysis revealed notable liver and intestinal integrity enhancements among fish receiving BA-enriched diets, especially D3. Additionally, gene expression related to lipid metabolism in liver, peritoneal fat, and muscle tissues was upregulated in the treatment groups, especially 0.2 g/kg BAs compared to the control group. Results illustrate significant modulation of lipid metabolism gene expression parameters (Adipose triglyceride lipase; ATGL, Hormone-sensitive lipase; HSL, Peroxisome proliferator-activated receptor α; PPARα, Fatty acid synthase; FAS) by BAs treatments and were upregulated in BA-fed groups (D2-D6). Conversely, Carnitine palmitoyl transferase 1; CPT(-1)and Insulin-like growth factor(-II); Igf(-II) expression declined, particularly when the BAs dose was increased. Accordingly, dietary 0.2 g/kg BAs supplementation positively influences on physiological, biochemical parameters, and lipid metabolic of Nile tilapia, making it a promising feed additive for aquaculture.