Dietary Pieris japonica Leaf Powder Enhances Hepatic Antioxidant Capacity, Modulates Cecal Microbiota, and Improves Eggshell Thickness in Laying Hens

Oxidative stress and intestinal health are critical factors that are closely linked to the production performance and physiological status of laying hens. This work assessed how dietary incorporation of Pieris japonica leaf powder (PJP) shapes egg quality attributes, hepatic antioxidant defence, gut tissue morphology, and cecal microbial community profiles in layers. A total of 360 healthy 56-week-old Hy-Line Brown layers were randomly assigned to four treatments, each containing six replicate pens housing 15 birds apiece. Animals received basal feeds containing 0.00% (control), 0.05%, 0.10%, or 0.20% PJP throughout the 10-week experimental run that including a 2-week adaptation period. Relative to the control group, diets with 0.05% PJP significantly increased eggshell thickness (p < 0.05). Hepatic total antioxidant capacity (T-AOC), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) were significantly elevated in PJP-supplemented groups (p < 0.05). The 0.10% PJP addition improved duodenal villus-height-to-crypt-depth ratio (V/C). Regarding cecal microbiota, 0.10% PJP reduced the Simpson index while elevating Collinsella relative abundance (p < 0.05). Noticeably, the 0.20% supplementation exerted adverse effects on egg-related indices. Correlation analysis indicated that cecal microbiota was closely associated with hepatic antioxidant indices and eggshell-related indicators. In summary, dietary PJP inclusion may improve the eggshell thickness of eggs from laying hens by enhancing host antioxidant defense, reshaping the composition of cecal microbial communities. It was reported that 0.10% PJP supplementation yielded the most favorable comprehensive responses under the conditions adopted within this trial.