Effect of restricted feeding regimes on growth, lipid metabolism and stress related genes in Nile tilapia (Oreochromis niloticus, Linnaeus 1758) cultured in a biofloc-aquaponic basil (Ocimum basilicum) system

Abstract The objective of this study was to evaluate the productive performance and expression levels of growth-related (IGF1 , mTOR), lipid metabolism-related (FAS ), and oxidative stress-related (hsp70) genes in Nile tilapia ( Oreochromis niloticus ) subjected to different feed restriction regimes in a biofloc-aquaponics system. The experiment included a restriction phase of 84 days with different feeding schedules (Control: daily; T1: 5 days of feeding/2 days of restriction; T2: 3 days of feeding/4 days of restriction; T3: 1 day of feeding/6 days of restriction), followed by a 28-day refeeding period. T1 showed the highest weight gain, and Specific Growth Rate (SGR), indicating complete compensatory growth. More severe restrictions resulted in lower Feed Conversion Ratio (FCR) values. Short-term restrictions did not significantly alter IGF1, mTOR, or hsp70 expression; however, long-term restrictions resulted in a marked downregulation of mTOR and an upregulation of hsp70 in treatments T2 and T3. Notably, FAS expression appeared responsive to moderate restriction. In basil plants ( Ocimum basilicum ), no significant differences were found in biometric variables or total phenolic content among treatments. Overall, the results indicate that moderate feed restriction can be applied in integrated biofloc–aquaponic systems without compromising fish survival or plant performance, while inducing distinct metabolic and physiological responses in Nile tilapia.