Dietary inclusion of curry plant (Helichrysum italicum) extract in rainbow trout (Oncorhynchus mykiss) culture: Growth performance and gene expression related to digestion, antioxidant, and immune responses

In this study, a 60-day trial was conducted to determine the effects of curry plant (Helichrysum italicum) extract in the diet of rainbow trout (Oncorhynchus mykiss) with an initial average live weight of 15.84 ± 0.05 g on growth performance and gene expressions associated with digestion, antioxidant capacity, and immune response. Four experimental diets were formulated as a basal diet (Control; C) and diets supplemented with varying levels of curry plant extract (CP05; 0.5 g kg⁻¹, CP1; 1 g kg⁻¹, and CP2; 2 g kg⁻¹). Growth indices showed significant increases in all curry plant extract groups compared to the C group (p < 0.05). Similarly, higher levels of trypsin, lipase, and amylase expressions were observed in the curry plant extract groups compared to the C group (p < 0.05). The superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) gene expression levels were elevated in the CP extract groups (p < 0.05). The expression levels of interleukin-1β (IL-1β), tumor necrosis factor (TNF-α), and interleukin-8 (IL-8) were also influenced by the incorporation of CP extract into the diet, showing significant changes (p < 0.05). In conclusion, this study experimentally demonstrates that supplementing the diet of rainbow trout with CP extract can positively influence healthy growth parameters.