SELENIUM-RICH CARDAMINE HUPINGSHANENSIS ON GROWTH, BIOCHEMICAL INDICES, SELENIUM METABOLISM, ANTIOXIDANT CAPACITIES AND INNATE IMMUNITIES IN JUVENILE BLACK CARP (MYLOPHARYNGODON PICEUS)

In order to investigate the effects of different levels of dietary selenium-rich Cardamine hupingshanensis on the growth performance, physiological and biochemical parameters, selenium metabolism, antioxidant capacities and innate immunities in black carp (Mylopharyngodon piceus), 360 juvenile black carps with initial body weight of (5.51±0.02) g were randomly divided into four groups, and each group had 3 replicates. Four levels of selenium-rich C. hupingshanensis (0, 0.5, 1.0 and 2.0 g/kg) (selenium levels 0.04, 0.43, 0.75 and 1.57 mg/kg) were added and made four isonitrogenous and isoenergetic diets. The culture period was conducted for 60 days. The results showed that adequate selenium-rich C. hupingshanensis (0.5 and 1.0 g/kg) could significantly increase the weight gain rate (WGR) and specific growth rate (SGR), while significantly decrease the feed conversion ratio (FCR), comparing with the control group and the excessive group (2.0 g/kg) (P<0.05). In the fish body composition, the crude protein levels were significantly increased in fish fed with 1.0 g/kg selenium-rich C. hupingshanensis, and then decreased at 2.0 g/kg selenium-rich C. hupingshanensis. Adequate supplemental level of selenium-rich C. hupingshanensis (0.5 and 1.0 g/kg) could significantly increase the serum albumin (ALB), triglycerides (TG) and total cholesterol (TCH), while decrease serum glucose (GLU) levels. Higher activities of superoxide dismutase (SOD), the catalase (CAT) and glutathione peroxidase (GSH-PX), levels of total antioxidant capacities (T-AOC), and the glutathione (GSH) (P<0.05) were shown in the liver of fish fed adequate supplemental level of selenium-rich C. hupingshanensis. Meanwhile, adequate supplemental level of selenium-rich C. hupingshanensis could significantly increase expression level of nuclear factor-erythroid-2-related factor 2 (Nrf2), Mn-superoxide dismutase (Mn-SOD), catalase (CAT), glutathione peroxidase 1 (GPX1) and glutathione peroxidase 4 (GPX4), while decrease the expression level of Kelch-like-ECH-associated protein 1 (Keap1) in the fish liver (P<0.05). In addition, adequate supplemental level of selenium-rich C. hupingshanensis significantly increase expression level of selenium-metabolic proteins, including selenocysteine lyase (SCLY), selenide, water dikinase 1 (SPS1), 15kDa selenoprotein (SEP15), selenoprotein T2 (SEPT2), selenoprotein H (SEPH), selenoprotein P (SEPP) in the liver of juvenile black carp compared with the control group (P<0.05). Furthermore, the expression level of innate immune defense molecules, including liver-expressed antimicrobial peptide 2 (Leap2), hepcidin (HEPC), lysozyme (LYS) and complement 3 (C3) were significantly up-regulated by adequate supplemental level of selenium-rich C. hupingshanensis (P<0.05). In conclusion, these results suggest that the adequate dietary supplemental level of selenium-rich C. hupingshanensis could significantly increase growth performances, promote the selenium metabolism, improve antioxidant capacities and enhance innate immunities in black carp.