Dietary licorice (Glycyrrhiza glabra) improves growth, lipid metabolism, antioxidant and immune responses, and resistance to crowding stress in common carp, Cyprinus carpio

This study aimed to investigate the effects of dietary licorice (Glycyrrhiza glabra) on growth, lipid metabolism, antioxidant and immune response, and stress resistance of common carp. The fish (12.14 ± 0.39 g) were fed diets containing 0 (control), 10 (G1), 20 (G2) and 30 (G3) g/kg licorice root powder for 60 days and then subjected to 3-hr crowding stress (40 kg/m3). The highest final weight and catalase activity and the lowest FCR and cholesterol levels were observed in fish fed diets 10-30 g/kg licorice inclusions. The highest lipase activity and the lowest LDL and triglyceride levels were recorded in G2 and G3 groups. Serum glutathione peroxidase (GPx) and complement (ACH50) activities and total immunoglobulin (Ig) levels were significantly higher and malondialdehyde levels were lower in G2 and G3 groups than the control. Serum lysozyme and ALP activities significantly increased in 10-30 g/kg licorice groups before and after stress. Crowding stress increased cortisol levels in all groups; however, its levels significantly reduced in G2 and G3 groups at 24 hr after stress. Furthermore, dietary licorice significantly decreased ALT activity in the G2 group at 8 hr after stress. These findings demonstrate the hepatoprotective, antioxidant, immunoregulative, anti-stress and growth-promoting effects of G. glabra in common carp. © 2020 John Wiley & Sons Ltd