Gene expression signatures mediate phosphorus source effects on egg production and bone strength in late‐lay hens

BACKGROUND This study explores how varying dietary phosphorus levels, particularly through dicalcium phosphate (DCP) and tricalcium phosphate (TCP), influence egg production performance and bone quality in aging laying hens, along with tibia bone gene expression. A total of 576 laying hens were randomly assigned to a 2 × 4 factorial design (two phosphorus sources × four levels), with six replicates per treatment (12 hens each). Hens were housed under controlled environmental conditions. The study employed two‐way analysis of variance to analyze 18 parameters related to production, egg quality, serum biochemistry, and bone traits, with post hoc Tukey tests for multiple comparisons. Egg and bone parameters were analyzed separately. Pearson's correlation assessed relationships while controlling for phosphorus level and hen age. RESULTS Hens fed TCP had higher egg production and improved feed conversion ratio compared to DCP. Serum inorganic phosphorus was higher in DCP‐fed hens. TCP also enhanced bone quality, with greater bone breaking strength, bone mineral density, and bone mineral content (BMC). Gene expression analysis revealed upregulated osteogenic markers ( OPG and RANKL ; P < 0.05) in TCP, while DCP elevated FGF23 expression (6.88). RANKL showed significant correlation with production traits: 43% with egg production ( P < 0.001) and 32.1% with feed conversion ( P < 0.01). These findings highlight that TCP supports bone health and calcium regulation, whereas DCP promotes bone resorption, ultimately reducing production longevity. CONCLUSION TCP boosts productivity and bone health in aging hens by upregulating OPG/RANKL signaling, optimizing bone remodeling. Future studies should investigate long‐term gene expression changes and alternative pathways.