Effects of Zanthoxylum bungeanum Leaves on Production Performance, Egg Quality, Antioxidant Status, and Gut Health in Laying Hens

<i>Zanthoxylum bungeanum</i> leaves (ZBL) are a phytogenic feed resource, but their energy value and functional effects in laying hens are not well defined. Two experiments were conducted. In Exp. 1, 96 healthy 38-week-old Roman Pink laying hens were allotted to either a control diet or a diet containing 5% ZBL (eight replicates, six hens per replicate) to determine apparent metabolizable energy (AME) using an indicator method (7 d adaptation, 3 d collection). The AME and nitrogen-corrected AME of ZBL were 5.46 and 5.33 MJ/kg, respectively. In Exp. 2, 832 healthy 41-week-old hens were randomly assigned to diets supplemented with 0, 1%, 2%, or 3% ZBL (8 replicates, 26 hens per replicate) for 8 weeks after 1 week adaptation. Dietary ZBL at 1% to 3% did not affect production performance (<i>p</i> > 0.05), but increased albumen height linearly (<i>p</i> < 0.05) and improved yolk color at 2% and 3% (<i>p</i> < 0.05). ZBL increased serum albumin (<i>p</i> < 0.05) with a linear tendency (<i>p</i> = 0.065), and elevated serum IgA and IgM linearly (<i>p</i> < 0.05). Serum total antioxidant capacity and total superoxide dismutase were increased (<i>p</i> < 0.05) with significant linear and quadratic responses (<i>p</i> < 0.05), while serum malondialdehyde was reduced (<i>p</i> < 0.05). In the liver, 3% ZBL increased total antioxidant capacity (<i>p</i> < 0.05), hepatic catalase activity was decreased in all ZBL groups (<i>p</i> < 0.05), and hepatic malondialdehyde was reduced (<i>p</i> < 0.05). Cecal acetate increased linearly (<i>p</i> < 0.05), and propionate and butyrate increased with both linear and quadratic dose responses (<i>p</i> < 0.05). ZBL improved small intestinal morphology, especially duodenal villus height (<i>p</i> < 0.05). Gut microbiota was remodeled, with a marked reduction in <i>norank_o__WCHB1-41</i> and increases in <i>Ruminococcus</i>, <i>Pseudoflavonifractor</i>, and several <i>Coriobacteriales</i> and <i>Erysipelatoclostridiaceae</i> taxa. Overall, ZBL provides usable energy and, at 2-3% inclusion, enhances egg quality, antioxidant status, humoral immunity, short-chain-fatty-acid production, and intestinal health without compromising laying performance.