Abstract
This study aimed to assess the impacts of licorice (Glycyrrhiza glabra) on the growth performance, carcass traits, intestinal microbiota, liver and kidney functions, immunity, oxidative status, and lipid profile of Japanese quails. A total of 200 one-week-old unsexed Japanese quails with an average initial body weight of 26.24 ± 0.2 g were randomly distributed into 5 equal groups of 40 birds and further subdivided into 5 replicates. The first (control) group was fed a diet without any licorice, while licorice powder was added at levels of 250, 500, 750, and 1000 mg per kg diet in the second, third, fourth, and fifth groups, respectively. At the age of 3 wk, the group of quail fed on a diet supplemented with 750 and 1000 mg licorice/kg of diet gained the highest body weight (BW) and daily body weight (DBW), while attaining the lowest feed conversion ratio (FCR) compared to other groups. Meanwhile, groups fed diets with licorice at levels of 0 and 250 mg/kg showed the highest feed intake. After the 5-wk feeding trial, the highest BW and DBW values, and the lowest FCR were recorded in the group fed with 750 mg licorice/kg diet. The different treatments produced no significant differences (P > 0.05) in quail carcass characteristics, including percentages of carcass, liver, gizzard, heart, giblets, and dressing. The blood of the group fed a 750 mg licorice diet had higher contents of total protein and GLOB, while its contents of A/G%, lactate dehydrogenase (LDH), total cholesterol, triglyceride (TG), and low density lipoprotein (LDL) were lower. Apart from the high level of licorice (1000 mg/kg), the MDA level was linearly and quadratically (P = 0.0413 and 0.001) decreased with different licorice groups, while superoxide dismutase (SOD), total antioxidant capacity (TAC), immunoglobulin G (IgG), and M (IgM) were quadratically increased when compared to the control group. Licorice supplementation resulted in marked reductions in the number of total bacteria, coliforms, E. coli, and Salmonella, compared to those in the control. In conclusion, the inclusion of licorice at levels of 750 and 1000 mg/kg into the diet of Japanese quail enhances the animal's performance, immunity, antioxidant capacity, and maintains a healthy gut microbiota.