Dietary dragonhead effects on growth, immunity and antioxidant and related genes expression in zebrafish (Danio rerio)

The present study aimed to investigate the effects of the herbaceous plant, Dracocephalum kotschyi, on the im-mune response, antioxidant enzymes activity, growth performance, and related genes expression in zebrafish (Danio rerio). An in vivo trial was carried out by feeding zebrafish (initial weight of 0.47 +/- 0.04 g) with different levels of powdered D. kotschyi: 0% (C-0%, control), 1% (Dk-1%), 2% (Dk-2%) and 3% (Dk-3%) for 10 weeks. The results show that total protein (TP) and total immunoglobulin (IG), were significantly increased in both skin mucus and whole body extract (WBE). Lysozyme (LYS) activity significantly increased in the WBE of zebrafish fed with D. kotschyi integrated diets compared to the control (P < 0.05). The superoxide dismutase (SOD) of WBE was significantly (P < 0.05) enhanced by dietary D. kotschyi. Additionally, this herb brought about a significant up-regulation in immune (LYS), pro-inflammatory (IL-1 beta) from intestine, and antioxidant (SOD and CAT) genes in liver, compared to the non-supplemented group (P < 0.05). Growth hormone (GH) and insulin growth factor (IGF) genes expression were upregulated significantly in zebrafish by the addition of D. kotschyi, although body weight did not change. The best results were obtained with the 3% inclusion of powdered D. kotschyi, except for LYS and IGF expressions that were best upregulated by 2% and 3% of D. kotschyi. Our results indicate that powdered D. kotschyi (suggested dose of 3%) could potentially improve zebrafish's immune response and anti-oxidant defense.