Study Of Bony And Uterine Calcium-phosphorus Metabolism Related Factors Expression Levels In Different Laying Periods Hens

In modern intensive poultry farming system,osteoporosis of laying hens,a common skeletal metabolic disease which threatens the health and production performance,has caused serious economical loss to laying hens.The imbalance of bone formation and resorption induced by large demand for eggshell formation was accepted as the main reason of osteoporosis.In this study,we detected the tibial morphological characteristics,bone and uterus calcium-phosphorus metabolism related factors and eggshell quality changes in different laying stages,and discuss the correlation between bony and uterine calcium-phosphorus metabolism related factors expression and bone morphology and eggshell quality.The aim is to provide a theoretical foundation for calcium and phosphorus addition and osteoporosis prevention in laying hens.The layers of laying period?23 weeks?,peak period?43 weeks?and later laying period?72 weeks?were selected randomly as experimental object,and 12 for each group.The serum contents of calcium?Ca?and phosphorus?P?were measured by colormctric method,and the activity of' alkaline phosphatase?ALP?and tartrate-resistant acid phosphatase?TRAP?in serum were measured by colonnetric method.The levels of parathyroid hormone?kPTH?.calcitonin?CT?,25-hydroxyvitamin D₃?25-?OH?₂VD₃?,1,25-dihydroxy vitamin D₃?1,25-?OH?₂VD₃?,estradiol?E₂?and osteocalcin?BGP?in serum were detected by RIA.Enzyme-linked immunoassay was used to detect the content of procollagen type 1 carboxy-terminal peptide?PICP?in serum.The right tibia was collected and the microstructure of the bone was detected by micro-CT,and the osteoclast changes were observed by trap staining.The expression levels of bony calcium-phosphorus metabolism related factors?ALP,SPHK1,BMP2,BMP6,BMP7,PDGF-bb,TRAP,V-ATPase a3,RANKL,OPG,M-CSF,Cts K,MMP-9,FGF23,FGFR1,FGFR3,FGFR4?and uterine calcium deposition related f-actors?CaBP-D28k,VDR,PMCA,CA2,OPN?were detected using real time RT-PCR.At the same time,eggshell qualities were measured with conventional methods for 12 eggs of three laying periods.The results show that:1.The levels of Ca,CT,25-?OH?₂VD₃,1.25-?OH?₂VD₃ and TRAP in serum of peak period were significantly higher than in prophase laying period:OPN content was significantly lower than in prophase laying period.The contents of CT,1,25-?OH?₂VD₃,E₂,BGP and ALP in serum of peak period were significantly higher than in late laying period;PICP content was significantly lower than in late laying period.The contents of Ca,25-?OH?2VD3,PICP and TRAP in serum of late laying period were significantly higher than in prophase laying period;The contents of 1,25-?OH?₂VD₃,E₂,OPN and ALP were significantly lower than in prophase laying period.2.In prophase laying period,the tibia,cortical bone structure was dense,trabecular bone filled the entire bone marrow cavity,osteoclasts less.In the peak period of laying,the number of trabecular bone plummeted,medullary bone increased,the formation of smaller bone marrow cavity,the number of osteoclasts increased.In late laying period,the tibial cortical bone appears to absorb the cavity,medullary bone reduction,bone marrow cavity increased,the number of osteoclasts decreased.3.In the joints of the bone,the expression levels of FGFR3 and PDGFB mRNA in peak laying period were significantly higher than in prophase laying period,and ALP,RANKL,OPG,M-CSF,Cts K,TRAP,BMP6 and BMP7 mRNA expression were significantly lower than those of prophase laying period.The expression levels of FGF23?V-ATPase a3?FCGFR1?FGFR4 ?PDGFB mRNA were in peak laying period were significantly higher than in late laying period,and M-CSF?Cts K ? BMP6 mRNA expression were significantly lower than those of late laying perod.The expression levels of ALP?RANKL?OPG?FGFR3?Cts K?TRAP?FGFR1 ? FGFR4 mRNA in laying period were significantly higher than in prophase laying period,and FGF23 ? V-ATPase a3 mRNA expression were significantly lower than those of prophase laying period.4.In the womb,the expression levels of CaBP-D28k and VDR mRNA in peak laying period were significantly higher than in prophase laying period,and PMCA and OPN mRNA expression were significantly lower than those of prophase laying period.The expression levels of CaBP-D28k?PMCA?CA2 and VDR mRNA were in peak laying period were significantly higher than in late laying period.The expression levels of PMCA and OPN mRNA in laying period were significantly lower than in prophase laying period.5.Egg weight and egg shape index in peak laying period were significantly higher than in prophase laying pcriod.Egg shell thickness,egg shell strength and egg shell ratio in peak laying period were significantly higher than in late laying period.Egg shell thickness,egg shell strength and egg shell ratio in laying period were significantly lower than in prophase laying period,and egg weight and egg shape index were significantly than in prophase laying period.The results of this study demonstrated that the level of serum phosphorus in the whole laying period was stable,the serum calcium content was increasing,and qualities of bone and eggshell were reduced,which may be attributed to bone absorption elevation and uterine calcium deposition capacity reduction.