The effects of a non-steroid aromatase inhibitor on hybrid red tilapia masculinization, growth, reproductive hormone profile, and economic efficiency in aquaculture

Abstract

With the expansion of global aquaculture, innovative technologies such as using non-steroidal aromatase inhibitors (AIs) are increasingly being adopted as alternatives to traditional steroid hormones, like methyltestosterone, for masculinization. Prominent AIs, including tamoxifen citrate, letrozole, fadrozole, and exemestane, are widely applied in aquaculture for the masculinization of species such as Nile tilapia, European sea bass, and Japanese medaka. However, concerns persist regarding their residual effects on fish and potential impacts on wild populations and aquatic ecosystems. This study evaluates the effects of tamoxifen citrate inclusion on masculinization, growth performance, survival, histopathology, and economic efficiency in hybrid red tilapia. In total, 260 fry with average weight (0.064 ± 0.012 g) were equally assigned to four treatments with different tamoxifen inclusion levels: TMCA0 (control), TMLA1 (0.2 g/kg feed), TMMA2 (0.4 g/kg feed), and TMHA3 (0.6 g/kg feed), each with three replicates in a completely randomized design. The experiment consisted of two phases: a 60-day treatment phase with tamoxifen-enriched diets, followed by a 90-day recovery phase in outdoor hapas. Fry survival rates were significantly higher in all tamoxifen-treated groups compared to the control, though differences among treatments were not significant (P > 0.05). The 0.4 g tamoxifen/kg feed treatment showed the highest masculinization and growth hormone (GH) levels (P < 0.05). Estradiol hormone decreased with an increase in tamoxifen dosage, while 11-ketotestosterone increased significantly (P < 0.05). During phase 1, no significant differences in specific growth rate (SGR) were observed (P > 0.05). While in phase 2, fish fed 0.4 g and 0.6 g tamoxifen/kg showed significantly higher SGRs (P < 0.0001) compared to the control. The gonadosomatic index (GSI) was significantly higher in control and low tamoxifen fed fishes (0.2 g tamoxifen/kg feed) (P < 0.05). Pathological effects, including ovarian nuclear fragmentation in female and testicular interstitial cell hypertrophy in male, were observed in high tamoxifen fed treatments. Higher tamoxifen levels significantly increased fish yield and profitability, as indicated by improved economic conversion ratio (ECR) and economic profit index (EPI) (P < 0.05), despite higher feed costs during recovery. The study highlights tamoxifen’s significant effects on growth, survival, gonadal index, and histomorphology, recommending 0.2–0.4 g tamoxifen/kg feed to balance masculinization, growth, and health for sustainable aquaculture practices.