Physiological and health responses of common carp to dietary licorice leaf powder

Manipulating nutrition is crucial for optimizing fish growth, health, and overall performance in aquaculture. The use of natural additives in fish diets has attracted increasing attention due to their potential to enhance physiological traits and immune responses. This study aimed to evaluate the impacts of licorice leaf powder (Glycyrrhiza glabra) on the performance, physiological traits, and health indices of common carp (Cyprinus carpio). A total of 100 fish with a typical body weight of 80.43 ± 0.2 g were randomly assigned to 4 groups of 25 fish. A 3-week adaptation period on the control diet preceded the actual feeding trial. The fish were randomly divided into four groups: control (G1), diet without licorice leaf powder, licorice leaf powder 2.5% (G2), licorice leaf powder 5% (G3), and licorice leaf powder 7.5% (G4). After 60 days of feeding practice, the effect of licorice leaf powder was assessed, in which it had a significant effect on the overall physiological status; feed conversion ratio, heart, spleen, and gill somatic indexes, and weight without viscera index (in G4, p < 0.05). Additionally, it has a significant impact on blood parameters at G3 and G4. Furthermore, the results showed that blood glucose (cholesterol and triglycerides) increased significantly in G3 (G4). This study recommends that the inclusion of 5% licorice leaf powder in fish diets has a beneficial impact on blood parameters and overall health. The importance of this study is to document the physiological changes of common carp and the impact of licorice extract on improving common carp performance. These findings can serve as a basis for future investigations into aquatic organisms.