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

Calcium and phosphorus are two kinds of mineral elements in poultry,which are the main components of the skeleton.They have various nutritional and physiological functions,and regulate many physiological and biochemical metabolic processes.Except for the aboved physiological function,calcium and phosphorus also is the constituent of eggshell in the laying hens.Under physiological conditions,calcium and phosphorus were absorbed in duodenum through transcellular transport and paracellular transport way,then flow to the organs and tissues.In kidney,calcium and phosphorus are reabsorbed after glomerular filtration and then participate the formation of bones and shells,et al.,while unreabsorbed calcium and phosphorus were excreted by the way of urine.In the laying period,laying hens bone will be resorpted to provide calcium need of eggshell formation when the dietary calcium can not content the needs of lay eggs.But the persistent bone resorption can cause calcium-phosphorus metabolism disorder,then has negative effects on production performance,such as the decline of egg production and eggshell quality,and ultimately leads to osteoporosis.Although the productivity of laying hens has been greatly improved in modern poultry industry,calcium-phosphorus metabolism disorder in egg production period is significantly increased,and causes great damage to poultry industry.In present study,we detected the expression levels of calcium-phosphorus metabolism related factors in blood,duodenum and kidney of different laying period hens and discuss the change rules of these factors.The aim is to provide theoretical foundation for dietary calcium-phosphorus scientific addition,eggshell quality elevation and osteoporosis prevention.The layers of prophase laying period(23 weeks),peak period(43 weeks)and later laying period(72 weeks)were selected randomly as experimental object,and 12 for each period.The contents of calcium(Ca)and phosphorus(P)in serum were measured by colormetric method;The levels of parathyroid hormone(PTH),calcitonin(CT),25-(OH)VD3 and 1.25-(OH)2VD3 in serum were detected by RIA.The total RNA was extracted from duodenum and kidney and detected the expression levels of calcium-phosphorus metabolism related factors(TRPV5,TRPV6,CaBP-D28k,PMCA1b,NCX1,VDR,NaPi-IIb,NaPi-IIa,Klotho,FGFRl,FGFR3,FGFR4,PTHR1,Cyp24a1)using Real Time RT-PCR.The results show that:1.The levels of Ca,CT,25-(OH)VD3,1,25-(OH)2VD3 in the serum of peak period are significantly higher than in prophase laying period(p<0.05);The contents of CT,1,25-(OH)2VD3 in peak laying period are significantly higher than in late laying period(p<0.05);The contents of Ca,25-(OH)VD3,CT in late laying period are significantly higher than in prophase laying period(p<0.05);The contents of 1,25-(OH)2VD3 in late laying period was significantly lower than prophase laying period(p<0.05).2.The expression levels of TRPV5 and TRPV6 mRNA were not detected in duodenum or jejunum;The expression levels of CaBP-D28k,PMCAlb,VDR mRNA in peak laying period were significantly higher than in prophase laying period(p<0.05),and the levels of NCX1,NaPi-IIb mRNA expression were significantly lower than prophase laying period(p<0.05);The expression levels of PMCAlb mRNA was in peak laying period were significantly higher than in late laying period(p<0.05),and CaBP-D28k,VDR mRNA expression were significantly lower than in late laying period(p<0.05);The expression levels of CaBP-D28k,VDR mRNA in ate laying period were significantly higher than in prophase laying period(p<0.05),and NCX1,NaPi-IIb mRNA expression were significantly lower than in prophase laying period(p<0.05).3.In kidney,the expression levels of CaBP-D28k,PMCAlb,FGFR1,FGFR3,FGFR4 mRNA were significantly higher in peak laying period than in prophase laying period(p<0.05)and Cyp24al mRNA expression was significantly lower than in prophase laying period(p<0.05);The expression levels of PMCAlb,FGFR3,FGFR4,Cyp24al mRNA were significantly higher in peak laying period than in late laying period(p<0.05);The expression levels of CaBP-D28k,FGFR1 mRNA were significantly higher in late laying period than in prophase laying period(p<0.05),TRPV5.Cyp24al mRNA expression were significantly lower than in prophase laying period(p<0.05).The present results demonstrated that the content of serum calcium and its related metabolism factors were increased in peak laying period and late laying period,the content of phosphorus was stable.The expression levels of calcium absorption related factors are up regulated in duodenum and kidney,the phosphorus absorption factors expression levels were down regulated in duodenum,and there were no significant changes of phosphorus absorption factors expression levels in kidney.The results indicated that the calcium demand is increased in peak laying period and late laying period,which mainly dues to the enhancement of calcium absorption ability in duodenum and in kidney,and the increase of bone resorption,and the stabilization of phosphorus is mainly due to the decrease of absorption in duodenum and the resorption of bone.