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120 19 -week-old Aisha laying hens were randomly divided into three groups and fed 0.58,0.44,0.30 ( containing available phosphorus (AP) 0.4,0.25,0.10) diets containing total phosphorus ( TP ) 21 weeks . Experimental period every two weeks synchronization measured serum calcium, phosphorus, alkaline phosphatase , osteocalcin , calcitonin , estrogen , bone mineral density (BMD), eggshell thickness , strength and weight was measured ; each month slaughter of chickens take tibial metatarsal histological examination ; records of egg numbers . The results show that : feeding TP : 0.58,0.44 performance of laying hens no significant differences while fed with TP : 0.30 laying , body weight, eggshell quality has dropped significantly ; different phosphorus fed group, serum calcium , blood the phosphorus no significant differences ; TP : 0.30 chicken blood osteocalcin , alkaline phosphatase , and the control group compared to significantly improve ; this experiment the test group blood estrogen no significant change . Bone histological examination revealed ; beginning of the experiment , the hens cortical bone , medullary bone is normal, seen small amount osteoclasts ; experimental mid phosphorus deficient cortical bone appears a lot of absorbing cavity , absorbing cavity trabecular visible on the surface of a large number of osteoclasts cells , and TP : 0.30 set of circumstances than TP : 0.44 . With the continuation of the experiment , the cortical bone resorption cavity area increases, the absorption chamber and the increased number of osteoclasts . Also found that the experimental late control group bone biopsy shows a large number of osteoclasts and a small amount of bone resorption cavity . Conclusion : dietary TP : 0.44 might in critical phosphorus within , does not affect the performance of laying hens , but the bones causing hidden damage .
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