Effects of Licorice Stem and Leaf Forage on Growth and Physiology of Hotan Sheep

This study explored the impact of licorice stem and leaf forage in the diet of meat sheep on their growth performance, physiological parameters, immunity, and gut microbiota. Conducted in the Hotan region of Xinjiang, the experiment involved 40 healthy local Hotan sheep (5-6 months old) that were randomly assigned to four groups, with both corn stalks and corn grain partially substituted at varying levels (30%, 40%, and 50%) by licorice stems and leaves for 80 days. Daily feed intake and refusal were recorded to assess feeding behavior and efficiency, while body weight was measured every 20 days to monitor growth performance. On day 80, blood samples were collected via venipuncture for biochemical and immune function analysis, followed by slaughter to obtain meat samples for quality assessment. Results showed that dietary licorice supplementation significantly improved growth performance. Sheep in the 40% replacement group had the highest final body weight and average daily gain (<i>p</i> < 0.05), indicating better feed efficiency. These findings suggest that replacing corn stalks and grain with licorice stems and leaves at a 40% ratio can significantly improve growth performance. Biochemical results showed improved protein metabolism and lipid profiles, with increased TP and ALB and decreased TC and TG levels. Immune indicators, including IgG, IgM, IgA, and IL-6, were also elevated in licorice-fed groups. In summary, licorice stems and leaves demonstrated clear nutritional and immunological benefits, especially at the 40% inclusion level. Gut microbiota analysis showed that licorice stems and leaves increased the relative abundance of Firmicutes while reducing Bacteroidota. At the genus level, UCG_005 and Bacteroides increased with higher licorice concentrations, whereas Treponema decreased. Pearson correlation analysis indicated that UCG_005 was positively correlated with TP, ALB, IgM, and IL-6 and negatively correlated with TG and TNF-α. These findings suggest that using licorice stems and leaves as a replacement for both corn stalks and corn grain modulates gut microbiota composition and is closely associated with immune and biochemical responses in sheep.