Effects of Superground Leaves on Growth Performance and Immune Function in New Zealand Rabbits.

The rabbit industry urgently needs natural alternatives to maintain gut health. This need is growing due to the higher incidence of intestinal problems in antibiotic-free production systems. (Brazilian ginseng) is a medicinal plant rich in bioactive compounds. This study evaluated the effects of dietary inclusion of leaf powder on growth performance, immune function, and gut microbiota in New Zealand rabbits. A total of 100 New Zealand rabbits (35 days old) were randomly assigned to five groups (n = 20 each). The groups comprised a blank control group (CON), an immunosuppressed group (CTX), and three treatment groups receiving low (L), medium (M), and high (H) doses of leaf powder at 0.5%, 1%, and 2% of the basal diet, respectively. Growth performance was assessed by average daily gain (ADG). Intestinal morphology was evaluated by measuring villus height and crypt depth in the duodenum, jejunum, and ileum. Immune parameters included thymus and spleen weight, serum immunoglobulin levels, and leukocyte counts. Cecal microbiota diversity and composition were analyzed. Compared to CON, supplementation improved growth performance: the L and H groups had significantly higher ADG and a lower feed conversion ratio ( < 0.05). In intestinal histology, groups L and M had reduced crypt depth in the duodenum ( < 0.05), and group L had an increased villus height to crypt depth ratio. In the jejunum and ileum, groups L and H exhibited increased villus height and villus height to crypt depth ratio ( < 0.05), indicating an enhanced absorptive surface. In the immunosuppressed model, rabbits in all groups showed significantly increased thymus and spleen weight compared to the CTX group ( < 0.05) and demonstrated elevated serum immunoglobulins and leukocyte counts (monocytes, lymphocytes, and neutrophils) ( < 0.05). supplementation also enhanced cecal microbiota diversity and increased the abundance of beneficial bacteria. In summary, dietary leaf powder enhanced growth performance, immune organ development, and healthy gut microbiota in growing rabbits. The 0.5% supplementation level (L group) yielded the most consistent benefits. These results suggest that is a promising natural feed additive to promote rabbit health and production in antibiotic-free systems.