Effect Of Hy.d On Calcium And Phosphorus Metabolism And Eggshell Quality In FLHS Layers

Fatty liver hemorrhage syndrome?FLHS?in layers is one of the three major nutritional and metabolic diseases in modern layer production,causing serious economic losses to the breeding industry.When FLHS occurs,it is accompanied by symptoms such as easy to fracture,producing thin and soft shell eggs,and decreased egg production rate,which indicating that calcium and phosphorus metabolism is disordered.1,25-?OH?₂D₃,the key factor regulating calcium and phosphorus metabolism,generates in kidney from cholecalciferol?Hy.D?that hydroxylated through VD₃in liver.Previous studies have proved that chronic liver disease would induced bone metabolism disorder with serum 1,25-?OH?₂VD₃ level significantly reduced when chronic liver disease occurs,while Hy.D supplement could improve bone metabolism.The effect of Hy.D on calcium and phosphorus metabolism and eggshell quality in FLHS laying hens is still unclear.In this experiment,216 26-week-old commercial Hy-line brown laying hens were divided into 6 groups:blank control group,FLHS model group,Hy.D low-dose intervention group,Hy.D medium-dose intervention group,Hy.D high-dose intervention group and Hy.D control group.Animals were fed high-energy low-protein diets for 24 weeks to induce FLHS models.Blood was collected to prepare serum,then chemiluminescence,reflex immunoassay and enzyme-linked immunocompetitive method were used to detect the contents of calcium and phosphorus metabolism-related factors.The complete femur,tibia and humerus were collected for biomechanical analysis.Eggs were used to detect eggshell quality.Liver,duodenum,kidney,femoral joints and eggshell glands were extracted total RNA,and real-time fluorescence quantitative method was used to detect the expression of calcium and phosphorus metabolism related factors.The aim was to reveal effects of Hy.D on the calcium and phosphorus metabolism of FLHS layers,the results will provide a theoretical basis for the application of Hy.D to prevent and treat calcium and phosphorus metabolism disorders caused by FLHS in layers.The results showed:1.After Hy.D intervention,serum Ca,P,PTH,1,25-?OH?₂VD₃,ALP and OPN contents were significantly increased in FLHS layers,while CT,TRAP and BGP contents were obviously decreased.2.After Hy.D intervention,femur,tibia,humerus bone index and bone mineral density,tibia three-point bending load,maximum stress and bone ash were significantly increased in FLHS layers.3.After Hy.D intervention,egg shell thickness,egg shell strength,egg shell weight and egg shell specific gravity were significantly increased in FLHS layers.4.After Hy.D intervention,the expression levels of VDR,Ca BP-D28k and NCX m RNA duodenum were significantly decreased in the FLHS laying hens,and the expression levels of PMCA and Na Pi-?b in the duodenum and CYP2R and VDR genes were significantly increased in the liver.5.After Hy.D intervention,the expression of PTHR,PMCA,FGFR1,FGFR3,FGFR4,FGF23 and Klotho m RNA kidney were decreased significantly in the FLHS layers,while the expression of Cyp24a1,TRPV5,NCX and Na Pi-?a m RNA increased significantly.6.After Hy.D intervention,bone RANKL,OPG,V-ATPase,VDR and M-CSF m RNA expression increased significantly in FLHS layers,while SPHK1,BMP2,BMP6,BMP7 and Ctsk m RNA expression decreased significantly.7.After Hy.D intervention,the expression of CA2,Ca BP-D28k,OPN and VDR m RNA eggshell glands were significantly increased in FLHS layers.The results of this experiment show that Hy.D intervention can significantly increase the blood calcium and phosphorus content,bone biological characteristics and eggshell quality of FLHS layers.The mechanism is the same as that of Hy.D in improving duodenal calcium absorption,renal calcium and phosphorus reabsorption and strengthening Bone remodeling is related to the ability of eggshell glands to secrete calcium.