Abstract
The use of phytogenic feed additives has attracted increasing interest as a sustainable nutritional strategy to improve fish performance and health in aquaculture. This study evaluated the effects of dietary supplementation with thyme essential oil (TEO), mint essential oil (MEO), and their combination (TMEO) on growth performance, antioxidant status, and intestinal histomorphology in Nile tilapia (Oreochromis niloticus). A total of 224 fish (initial body weight 3.50 ± 0.20 g) were randomly allocated to four experimental groups with seven replicates per treatment and fed either a basal diet (control), a diet supplemented with 200 mg/kg TEO, 200 mg/kg MEO, or a combination of 100 mg/kg TEO and 100 mg/kg MEO for 120 days. Final body weight did not differ significantly among the groups (P > 0.05). However, cumulative weight gain was significantly higher in the MEO and TMEO groups than in the control group (P < 0.05). Dietary essential oil supplementation significantly affected antioxidant enzyme activities. Catalase (CAT) activity increased progressively across the supplemented groups, with the highest value observed in the TMEO group (P < 0.001). Glutathione peroxidase (GPx) activity was significantly higher in all supplemented groups than in the control group (P < 0.001), whereas superoxide dismutase (SOD) activity increased significantly only in the TEO and TMEO groups (P < 0.001). Histomorphological evaluation revealed increased villus length and goblet cell abundance, particularly in the TMEO group, while no villus or microvillus degeneration was observed in any treatment group. Overall, dietary supplementation with thyme and mint essential oils was associated with improvements in antioxidant status and intestinal morphology, whereas mint essential oil alone or in combination with thyme essential oil also enhanced cumulative weight gain. These findings support the potential use of thyme and mint essential oils as natural dietary supplements in Nile tilapia culture. However, further studies investigating different dietary inclusion levels, production conditions, and the underlying molecular mechanisms are needed to confirm and extend these findings.