Effect of dietary curry plant (Helichrysum italicum) on growth performance, non-specific immunity, digestion and antioxidant enzyme activities in rainbow trout (Oncorhynchus mykiss)

In this study, a 60-day experiment was conducted to evaluate the effects of curry plant (Helichrysum italicum) extract on the growth performance and gene expressions related to digestion, antioxidant capacity, and immune response in rainbow trout (Oncorhynchus mykiss) with an initial average live weight of 15.84±0.05 g. Four experimental diets were designed: a basal diet (Control) and diets supplemented with different levels of curry plant extract (AO05; 0.5 g/kg, AO1; 1 g/kg, and AO2; 2 g/kg). The parameters for final body weight (FW), weight gain (WG), daily weight gain (DWG), specific growth rate (SGR), protein efficiency ratio (PER), and feed conversion ratio (FCR) showed significant improvements in all groups supplemented with curry plant extract compared to the control group (p<0.05). Growth performance indicators, including FW, WG, DWG, SGR, and PER, displayed a nonlinear, quadratic increase with higher dietary levels of curry plant extract. Similarly, FCR values improved quadratically with increasing CP extract doses. Additionally, elevated expressions of digestive enzymes were observed in the curry plant extract groups compared to the control group. Significant differences in gene expressions of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), were also found between the curry plant extract and control groups (p<0.05). Furthermore, the expression levels of immune-related genes, such as interleukin-1β (IL-1β), tumor necrosis factor (TNF-α), and interleukin-8 (IL-8), were significantly altered by the inclusion of curry plant extract in the diet (p<0.05). In conclusion, this study provides experimental evidence that supplementing the diet of rainbow trout with curry plant extract can positively affect healthy growth parameters.