Optimizing Calcium and Phosphorus Nutrition in Laying Hens: A Meta-Analysis of Egg Production, Eggshell, and Bone Responses

This meta-analysis was conducted to evaluate the effects of dietary calcium (Ca) and non-phytate phosphorus (NPP) on production performance, eggshell quality, and bone characteristics in laying hens. The objective was to assess the effects of dietary Ca and NPP on egg production, egg weight, eggshell quality, and bone-related traits, and to examine dose–response relationships across hen ages. A systematic literature search following PRISMA guidelines identified controlled experimental studies published between 2000 and 2026. A total of 196 records were initially identified, of which data from 38 eligible studies, comprising 145 treatment observations, were extracted and analyzed using multilevel random-effects and meta-regression models. The results demonstrated that both Ca and NPP significantly influenced most production, eggshell, and bone traits, with egg production responding most strongly to dietary mineral levels, whereas egg weight was comparatively less sensitive. The Ca × NPP interaction significantly affected most outcomes, including egg production, egg weight, shell strength, bone ash, and bone weight, indicating that responses to one mineral depend on the dietary level of the other. Favorable performance was generally observed at Ca levels of 3.5–4.0% and NPP levels of 0.20–0.30%. Shell thickness was primarily driven by Ca, while shell strength was influenced by both Ca and NPP. Bone-related traits depended strongly on NPP, and the Ca × NPP interaction suggests that Ca and NPP should be considered jointly rather than in isolation. Meta-regression results confirmed significant effects of Ca, NPP, age, and their interaction across most outcomes, while heterogeneity was extremely high (I² = 99.8–100.0%), indicating variability among studies. Study-level moderators, including genetic strain, housing system, and diet type, significantly improved model fit, indicating that mineral responses vary across production systems and management conditions. Publication bias assessment showed trait-specific patterns but did not affect the overall robustness of the findings. Overall, this study emphasizes that balanced mineral nutrition, rather than excessive supplementation, is essential for optimizing laying hen performance and sustainability. Precision feeding strategies targeting optimal Ca and NPP levels can improve efficiency while reducing environmental impacts associated with phosphorus excretion.