Effects Of Dietary Calcium And Vitamin D₃ Levels On Laying Performance、egg Quality And Calcium Metabolism In Xiushui Yellow Black Bone Chicken During The Laying Stage

In order to systemically investigate the effects of dietary calcium and vitamin vitamin D₃ levels on laying performance,egg quality and calcium metabolism in Xiushui yellow black bone chicken during the initial egg laying stage.The 3×4 factorial experimental design was adopted with 3 levels of Ca（3.0%,3.4%,3.8%）and 4 levels of vitamin D₃（800 IU/kg,2200 IU/kg,3600 IU/kg,5000IU/kg）in the corn-soybean meal.A total of 240 layers has been randomly divided to 12 treatments with 20 layers per treatment,each treatment consisted of 20 replicates of 1layer each.Egg production、egg quality and calcium metabolism were investigated.（1）Dietary calcium levels（3.0%,3.4% and 3.8%）and vitamin D₃ levels（800,2200,3600 and 5000 IU/kg）had no significant effect on the laying performance of Xiushui yellow black bone chicken.（2）The egg laying rate and the Hastelloy unit reached the maximum when calcium was included at 3.8%;the heaviest egg and the highest Hastelloy unit were obtained when vitamin D₃ was added at a level of 3600 IU/kg.（3）Layers fed a diet with calcium at level of 3.0% had lower serum BGP than layers fed diet with calcium at level of 3.4% and 3.8%,respectively;layers fed a diet with vitamin D₃ at level of 5000 IU/kg had the higher serum PTH,CT and CaBP compared with layers fed diet with vitamin D₃ at level of 800,2200 and 3600 IU/kg,respectively.（4）layers had the highest calcium content of tibia when fed a diet with vitamin D₃ at 3600 IU/kg.The content of phosphorus inlayers had the highest phosphorus level in tibia when fed diet with calcium at levels of 3.0% and 3.4% combined with vitamin D₃ at levels of 3600IU/kg and 5000 IU / kg（P <0.05）.（5）The interaction between dietary calcium and vitamin D₃ significantly affected the expression of CaBP-D28 k mRNA in duodenum and eggshells（P <0.05）.layers had the highest mRNA expression of Ca BP-D28 k in duodenum and egg shell gland respectively when fed a diet with 3.8% calcium and3600IU/kg vitamin D₃.In conclusion,the recommended dietary Ca or vitamin D₃ for Xiushui yellow black bone chicken were 3.8% and 6000 IU/kg,respectively.