Dietary Supplementation with Zanthoxylum armatum ‘Jiuyeqing’ Leaf Extract Affects Laying Performance, Antioxidant Status, and Hepatic Metabolomic Profiles in Laying Hens

This study evaluated the effects of dietary Zanthoxylum armatum DC. ‘Jiuyeqing’ leaf extract (ZBLE) in laying hens. A total of 1024 healthy 41-week-old Lohmann Pink layers were assigned to four treatments with eight replicates of 32 hens and fed diets containing 0, 2, 4, or 6 g ZBLE/kg for 8 weeks. The results showed that laying rate significantly increased linearly during weeks 1–4 and 1–8 (p = 0.009 and 0.005, respectively), and the 6 g/kg group had a higher laying rate than the control group (CON) over weeks 1–8 (p = 0.026). Yolk color score increased (p < 0.001), and serum immunoglobulin M concentration increased significantly (p = 0.007), whereas serum biochemical parameters remained unchanged. Serum total antioxidant capacity and total superoxide dismutase activity and hepatic total antioxidant capacity and catalase activity increased significantly, whereas serum malondialdehyde decreased. Intestinal responses were segment-specific, with increased duodenal villus height, alongside greater jejunal crypt depth and a lower jejunal villus-to-crypt ratio at 6 g/kg. Hepatic metabolomic comparison between the CON and 6 g/kg groups indicated that glycerophospholipid metabolism was the most strongly enriched pathway. Overall, 6 g ZBLE/kg produced the most favorable response among the tested levels and may serve as a plant-based feed additive for laying hens.