A Systematic Review and Meta-Analysis of the Effects of Available Phosphorus Levels and Phytase on Bone Parameters in Laying Hens: Influence of Dose, Enzyme Origin, and Nutritional Reduction

This study aimed to evaluate, through a meta-analysis, the effects of available phosphorus levels and phytase supplementation on the bone quality of laying hens. The methodology consisted of a systematic review and quantitative integration of data from nine scientific articles published between 2019 and 2025, analyzing statistical contrasts among diets with adequate phosphorus levels (positive control), deficient diets (negative control), and diets supplemented with the enzyme phytase. The main results showed that the reduction of available phosphorus, particularly at levels above 0.2%, significantly compromised skeletal integrity, reducing bone strength by an average of 1.33 kgf and ash content by 2.16%. Although phytase supplementation promoted a significant recovery in strength (average gain of 1.94 kgf) and mineralization (1.41%) compared to the deficient group, it was not able to fully restore bone parameters to the levels of the positive control under conditions of severe mineral restriction. Additionally, the enzyme’s efficacy remained sta-ble regardless of its origin (bacterial or fungal) or the evaluated dosage (up to 1000 FTU/kg), while individual calcium and phosphorus contents in bone did not show uniform reduc-tions due to strong homeostatic regulation in the birds. It is concluded that phytase is a key tool for mitigating mineral deficiency; however, its ability to match the bone integrity of non-challenged birds is limited by the magnitude of dietary phosphorus restriction.