Effects of Althaea officinalis supplementation on growth performance and antioxidant, stress, and immune-related gene expression in rainbow trout (Oncorhynchus mykiss)

In this study, a 42-day feeding trial was conducted to evaluate the effects of Althaea officinalis extract on growth performance, antioxidant defense, stress-associated, and immune-related gene expression in rainbow trout (Oncorhynchus mykiss) with an initial average body weight of 2.48 ± 0.01 g. Three experimental diets were formulated: a basal control diet (C) and two diets supplemented with different levels of A. officinalis extract (AO1, 1 g kg-1 and AO2, 2 g kg-1). Growth indices showed significant improvements in both A. officinalis supplemented groups compared to the C group (P < 0.05). Gene expression levels of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) were significantly elevated in the supplemented groups (P < 0.05). Additionally, the expression of stress, and immune-related genes, including interleukin-1β (IL-1β), tumour necrosis factor-alpha (TNF-α), interleukin-8 (IL-8), and heat shock protein 70 (HSP-70), was also significantly influenced by dietary inclusion of A. officinalis extract (P < 0.05). Overall, these findings provide experimental evidence that dietary inclusion of A. officinalis extract enhances antioxidant capacity, modulates stress and immune-related gene expression, and promotes healthy growth in rainbow trout. These beneficial effects may be attributed to the presence of flavonoids and phenolic compounds in A. officinalis, which are known for their antioxidant and immunomodulatory properties.