Amelioration of growth performance, physio-metabolic responses, and antioxidant defense system in rainbow trout, Oncorhynchus mykiss, using dietary dandelion, Taraxacum officinale, flower extract

Abstract

In our study, the dietary effect of dandelion flower (DF) extract on growth performance, hemto-biochemical parameters, and transcriptomic responses of growth and antioxidant genes in rainbow trout were investigated. Accordingly, three hundred fingerlings were randomly stocked into 15 tanks and fed with different levels of DF extract (0 [control], 1, 2, 3, and 4 g/kg) for 8 weeks. The results showed the weight gain was significantly increased in 3 g/kg DF extract-supplemented group. The feed conversion ratio was significantly decreased in 3 and 4 g/kg DF extract treatments compared to the control group. The highest number of red blood cells and hematocrit level were observed in 3 g/kg DF extract treatment compared to 1 g/kg DF extract and the control group. A significant rise in the serum high-density lipoprotein, glutathione peroxidase (GPx), and catalase (CAT) was obtained in 3 g/kg DF extract. However, the levels of serum alanine and aspartate amino transaminase, and glucose were remarkably decreased at 3 g/kg DF added-group. The intestinal protease activity was significantly enhanced in the fish fed 3 g/kg DF extract compared to others. The body crude protein was also remarkably increased in the fish fed 3 g/kg DF extract. The transcriptomic responses of growth hormone, insulin-like growth factor-1, and ghrelin genes were notably up-regulated in the treated fish, especially in 3 g/kg DF extract. However, the expression of antioxidant-related genes (SOD, CAT, and GPx) was significantly decreased in DF extract-added groups. Overall, the optimal inclusion of DF extract in rainbow trout diet was ranged from 2.83 to 3.13 g/kg and 2.59 to 2.75 g/kg to improve growth performance and antioxidant status, respectively.