Abstract: The rapid development of large-scale layer farming has positioned China as the world’s largest producer and consumer of eggs,with the layer industry playing a pivotal role in its livestock sector.Phosphorus,an indispensable core nutrient in the diets of laying hens,is critical for maintaining physiological functions,promoting bone development,and ensuring eggshell quality.However,phosphorus in poultry diets primarily exists in the form of phytate and its salts.Due to the endogenous phytase deficiency in poultry,the biological availability of phosphorus is severely limited by the anti-nutritional effects of phytate.Concurrently,challenges such as phosphorus resource scarcity,rising feed costs,suboptimal production efficiency,and inadequate manure management have intensified.Therefore,eliminating the anti-nutritional characteristics of phytic acid,improving the digestibility and utilization rate of feed,and reducing the addition of inorganic phosphorus are critical for the sustainable development of the layer chicken industry.Exogenous addition of phytase to diets can hydrolyze phytic acid and phytates,reducing phosphorus excretion from livestock and poultry and decreasing reliance on mineral phosphorus sources.Although the application of phytase in conventional diets is relatively widespread,systematic research on its use in low-phosphorus diets for layers and the development of corresponding application protocols remain insufficient.The author summarizes the nutritional role of phosphorus in layers and examines the effects of phytase in low-phosphorus diets on performance,egg quality,gut health,and skeletal health,it further explores the extra-phosphoric effects of phytase and the factors influencing its application in low-phosphorus diets,aiming to provide theoretical foundations and practical guidance for the effective use of phytase in layer feed.

Key words: low-phosphorus diets; phytase; laying hens; phytate phosphorus; extra-phosphoric effect