Effects of dietary PQQ·Na₂ level on performance and bone microstructure of aged laying hens

A total of 480 Jinghong No. 1 laying hens (400 d of age) were randomly assigned to five groups for a 7-week feeding trial: a control group and four treatment groups supplemented with 0.5, 1.0, 1.5, or 2.0 mg/kg pyrroloquinoline quinone disodium salt (PQQ·Na₂), respectively. This study evaluated the effects of dietary PQQ·Na₂ on production performance, egg quality, calcium and phosphorus metabolism, tibial microstructure, intestinal morphology, and cecal microbiota. Dietary supplementation with 0.5 mg/kg PQQ·Na₂ significantly increased laying rate, eggshell strength, and albumen height (P < 0.05). Serum alkaline phosphatase, 25-hydroxyvitamin D₃, osteocalcin, and calcium concentrations were increased, whereas calcitonin and parathyroid hormone concentrations were decreased (P < 0.05). Micro-CT analysis showed that the 0.5 mg/kg PQQ·Na₂ treatment increased tibial bone mineral density and bone volume fraction and improved trabecular microstructure, although tibial calcium and phosphorus contents were not significantly changed. In addition, 16S rRNA sequencing indicated that PQQ·Na₂ altered cecal microbial composition, including changes in the relative abundances of several dominant genera. Overall, supplementation with 0.5 mg/kg PQQ·Na₂ improved laying performance, egg quality, and bone health in aged laying hens, potentially through coordinated regulation of calcium-phosphorus metabolism, intestinal morphology, tibial microstructure, and cecal microbiota.