Role of a non-steroidal aromatase inhibitor on growth performance, body composition, reproductive and serum biochemical indices, and intestinal histomorphology in hybrid red tilapia (Oreochromis spp.).

Non-steroidal aromatase inhibitors like tamoxifen citrate are commonly used in aquaculture for sex reversal, yet their broader impacts on fish growth, body composition, serum biochemistry, and gut histomorphology remain underexplored. This study evaluated the effects of tamoxifen citrate on hybrid red tilapia fry growth, reproductive traits, haematological parameters, biochemical profiles, and reproductive hormone levels.A total of 260 swim-up fry (mean weight 0.06 ± 0.04 g) were randomly assigned to four dietary treatments: TA0 (0 mg/kg), TA1 (200 mg/kg), TA2 (400 mg/kg), and TA3 (600 mg/kg), with three replicates of 25 fish each. Fish were fed these diets for 60 days, followed by a 90-day recovery phase in outdoor hapas. The results showed that the male percentage increased significantly with tamoxifen inclusion, reaching 96.83% at 600 mg/kg (P < 0.05). Oestrogen levels decreased, while 11-ketotestosterone increased proportionally with tamoxifen dosage (P < 0.05). Higher tamoxifen inclusion (600 mg/kg) worsened feed conversion ratio (FCR), feed conversion efficiency (FCE), and protein efficiency ratio (PER) during the treatment phase but improved these parameters during recovery, alongside enhanced weight gain and specific growth rate (SGR) (P < 0.05). Higher tamoxifen doses increased hepatosomatic (HSI), viscerosomatic (VSI), and stomach indices while reducing gonadosomatic index (GSI) (P < 0.05). Elevated dosages reduced protein and lipid content but increased moisture levels (P < 0.05). Haemoglobin, MCV, MCH, and MCHC were higher at 200-400 mg tamoxifen/kg, while haematocrit declined with higher dosages (P < 0.05). Elevated tamoxifen levels increased AST, ALT, and globulin but decreased ALP, albumin, and cholesterol (P < 0.05). Moderate tamoxifen dosages (200-400 mg/kg) are recommended for sustainable sex reversal in hybrid red tilapia, minimising physiological and histological disruptions. High dosages (> 400 mg/kg) should be avoided due to haematological stress and immune suppression. Further studies are necessary to assess long-term ecological impacts and aquatic biodiversity.