Study On The Changes Of Calcium And Phosphorus Metabolism Related Factors Expression In Osteoporosis And Eggshell Glands Of Osteoporotic Laying Hens

Cage layer osteoporosis(CLO)is a common bone fracture disease in caged laying hens,and it is easy to occur in high-production hens.In the modern layer chicken breeding system,the incidence of the disease is the most prominent,which can reach 16-20%,causing an unpredictable loss to the global egg industry.Currently,it is believed that osteoporosis in layer hens is a disease caused by calcium and phosphorus metabolism disorders in laying hens,but the specific pathogenesis is still unclear.The calcium and phosphorus metabolism of laying hens is relatively complex,involving the duodenum,kidneys,bones and eggshell glands,among which bone degradation during egg production to meet the eggshell gland calcium secretion is closely related to the occurrence of CLO.Therefore,it is clear that the changes of calcium and phosphorus metabolism in bone and eggshell glands during CLO development are of great significance in revealing the mechanism of CLO and preventing and controlling CLO during production.In this study,216 Hyland brown laying hens(73 weeks old)were used as subjects.CLO models were prepared by feeding low-calcium diets.Blood was collected at 77 and 79 weeks of age,serum was prepared,and radioimmunoassay was used.Enzyme-linked immunosorbent assay was used to detect serum calcium and phosphorus metabolism related factor content;femoral joints and eggshell glands were collected and total RNA was extracted.Real-time fluorescence quantitative analysis was used to detect calcium and phosphorus metabolism related factors in bone and eggshell glands.The level of expression in order to reveal the pathogenesis of caged egg hens osteoporosis provides a theoretical basis for the prevention and treatment of osteoporosis in laying hens,the addition of calcium and phosphorus in feed,and the improvement of broiler breeding efficiency.Test results show:1.The content of Ca,P,25-(OH)VD3,1,25-(OH)2VD3 in serum of CLO layer hens decreased significantly,and the content of PTH and CT in serum of CLO layer hens increased significantly.2.The tibia,femur,iliac bone index and bone density of the CLO layer hens and the maximum stress and three-point bending load of the tibia were significantly reduced.3.The mRNA levels of ALP,RANKL,OPG,M-CSF and FGF23 were significantly decreased in CLO osteoblasts,and the expression of V-ATPase a3 mRNA in CLO layer hens was significantly decreased.4.The mRNA expression levels of CtsK,TRAP,SPHK1,BMP2,BMP6,and BMP7 were significantly higher in the osteoclasts of CLO hens.The expression of FGF1,FGF3,and FGF4 mRNA was significantly decreased,and the MMP-9 of CLO hens was decreased.There was no significant difference in the expression level of PDGF-bb mRNA compared with normal layer hens.5.The expression levels of CaBP-D28 K,PMCA,CA2,VDR and OPN mRNA were significantly decreased in CLO-related factors of CLO egg shell glands.The results of this experiment show that the levels of calcium,phosphorus,25-(OH)VD3 and 1,25-(OH)2VD3 in the serum of osteoporosis hens are reduced,the content of PTH and CT increases,and the biomechanical index decreases;The bone formation ability of the cells is weakened,and the bone resorption capacity of the osteoclasts is enhanced,the bone resorption is greater than the bone formation,and the calcium deposition ability of the eggshell glands is reduced.