Effects of dietary supplementation of Silphium perfoliatum on growth performance, antioxidant capacity and lipid metabolism of juvenile Megalobrama amblycephala

In order to avoid competition between aquatic animals and humans, seeking new feed raw materials has become an important direction for the healthy development of aquaculture. Silphium perfoliatum, also known as rosin, has the advantage of “not competing with grain for land”. This study is conducted to investigate the effects of dietary S. perfoliatum (SP) supplementation on the growth performance, antioxidant capacity and lipid metabolism of juvenile Megalobrama amblycephala. Four experimental diets were formulated containing 0% (control group), 2%, 4% and 6% S. perfoliatum (SP). Two hundred and forty healthy M. amblycephala juveniles (3.85±0.50 g) were randomly fed one of the four experimental diets in triplicates (20 fish per tank) for 8 weeks. After the 8-week feeding trial, the growth performance, muscle composition, plasma biochemical indicators, hepatic and intestinal antioxidant capability, and gene expressions related to lipid metabolism were measured. The results showed the following. Compared to the control group, the weight gain rate (WGR) and specific growth rate (SGR) were significantly lower in the 4% and 6% SP supplementary groups (P<0.05). In the 6% group, the final body weight (FBW) was significantly lower than that of the control group (P<0.05), while the feed coefficient ratio (FCR) was significantly higher (P<0.05). As to the antioxidant capability, the levels of catalase (CAT) and superoxide dismutase (SOD) in the intestine were significantly higher in SP supplementary groups compared to the control group (P<0.05). In terms of fat deposition and lipid metabolism, fat contents in the muscle of the 4% and 6% SP supplementary groups were significantly higher than that in the control group (P<0.05). The intestinal lipase activity was significantly lower in the 4% and 6% SP supplementary groups compared to the control group (P<0.05). The contents of plasma triglycerides (TG), cholesterol (TC), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) in the 6% SP supplementation group were significantly higher than those in the control group (P<0.05). Meanwhile, the gene expressions of hepatic fas and srebp1c, relating to lipid synthesis, were significantly activated in the 4% and 6% SP supplementary groups (P<0.05). The gene expressions of hepatic lpl, cpt1a and pparβ, relating to lipolysis metabolism, were significantly inhibited in the 6% SP supplementary group (P<0.05). At the end of the 8-week feeding trial, a challenge test of intraperitoneal injecting 50% CCl₄ solution was performed. It was found that the cumulative mortality rate of the 2% SP supplementary group was lower than that of the control group at 96 h post-injection. Further analysis of hepatic antioxidant capacity at 24 h post-injection revealed that the hepatic SOD activity of the 2% SP supplementary group was significantly higher than that of the control group (P<0.05). In general, the supplementation of 2% S. perfoliatum in diet showed no negative effect on the growth and feed utilization of juvenile M. amblycephala, but improved the intestinal antioxidant capacity. 4% and 6% dietary supplementation levels of S. perfoliatum inhibited the growth and resulted in fat deposition in the muscle. All the results of this study provide a reference for further application of S. perfoliatum in aquatic feed.