Dernekbasi, SevalKaradayi, Bahadir Tunahan2026-04-252026-04-2520250920-17421573-5168https://doi.org/10.1007/s10695-025-01610-yhttps://hdl.handle.net/11486/8195This study investigated the effects of substituting Tenebrio molitor larvae meal (TM) for fishmeal at varying inclusion levels (0%-TM0, 50%-TM50, 75%-TM75 and 100%-TM100) on growth performance, digestive enzyme activities, and antioxidant responses in Nile tilapia (Oreochromis niloticus). Four different isonitrogenous and isolipidic experimental diets were formulated and fed to the fish for 12 weeks. The highest growth performance was observed in the TM75 group, while polynomial regression analysis indicated an optimal replacement level around 66%. TM inclusion significantly modulated the activities of digestive enzymes amylase, lipase, pepsin, and trypsin. Antioxidant enzymes including catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) showed increased activity in TM-fed groups, particularly at moderate inclusion levels. However, elevated levels of lipid peroxidation (LPO) in the TM75 and TM100 groups indicated a threshold beyond which oxidative stress may arise despite enhanced antioxidant defense. These results suggest that TM meal can be a promising alternative protein source in tilapia diets when used at optimized inclusion levels, supporting both physiological performance and oxidative balance. The findings contribute to sustainable aquafeed strategies by identifying the biological and functional limits of insect meal use in freshwater fish.eninfo:eu-repo/semantics/closedAccessNile tilapia (Oreochromis niloticus)Tenebrio molitorSustainable aquafeedInsect mealAlternative protein sourceDigestive enzymesAntioxidant activityArticle51610.1007/s10695-025-01610-y412888332-s2.0-105022870322Q1WOS:001622596300001Q2