Influence of Dietary Glycyrrhetinic Acid Combined with Different Levels of Lipid on Growth, Body Composition, and Cortisol of Juvenile Channel Catfish, Ictalurus punctatus

Glycyrrhetinic acid (GA), the main active constituent of Glycyrrhiza glabra roots, is extensively used as food additives and herbal medicines. This study was carried out to evaluate the effects of different dietary levels of GA on growth and body composition of channel catfish (average weight, 1.10 ± 0.02 g). Eight diets were formulated to contain two levels of lipid (6.0 and 8.0%), and four levels of GA (0, 0.3, 0.6, and 0.9 g/kg). The experiments lasted for 60 d. Results showed that weight gain tended to decrease as dietary GA levels increased ( P > 0.05) with the lowest found in fish fed 0.9 g/kg dietary GA ( P < 0.05). Feed intake increased significantly as dietary GA concentrations increased up to 0.6 g/kg ( P < 0.05) and viscera/body ratio, condition factor, hepatosomatic index, and intraperitoneal fat ratio decreased significantly as GA concentration increased ( P < 0.05). Lipid content of whole body, viscera, and liver decreased significantly ( P < 0.01) as dietary GA increased, whereas moisture content showed an opposite trend. The cortisol in fish fed 0.3 and 0.6 g/kg GA was not significantly higher than that of fish without GA supplementation, but glucose in the former two groups was higher ( P < 0.05). Results of this study indicate 0.3 and 0.6 g/kg GA had a positive influence in reducing body lipid and IFR deposition in channel catfish without significant side effects on growth. The beneficial effect may be due to extending endogenous cortisol half‐life and increasing the duration of action.