摘要An experiment was conducted to investigate the optimal dietary calcium(Ca)levels in Jing Tint 6 layer chicks fed different sources of zinc(Zn).A total of 1440 day-old birds with similar body weight(38±0.5 g)were selected and divided into 10 groups with 6 replicates per group,each containing 24 chicks.The experimental period lasted from hatch to d 14.Diets were formulated to contain 2 sources of Zn:organic Zn(80 mg/kg Zn as hydroxy methionine Zn,HMZn)and inorganic Zn(80 mg/kg Zn as Zn sulfate).For each Zn source,5 diets were formulated with Ca levels of 0.80％,0.90％,1.03％,1.10％,and 1.20％,respectively.The results showed that dietary Ca significantly increased the average daily gain(ADG)(P＜0.001).In addition,ADG was enhanced by the supplementation of organic Zn compared to diets containing inorganic Zn(P=0.009).Tibia length was significantly increased by the interaction of Ca and Zn(P=0.038).Serum Ca and P levels were significantly higher in the group supplemented with organic Zn compared to the group fed inorganic Zn(P＜0.05).The apparent total tract retention co-efficients(ATTRC)of Ca increased quadratically with the increase of Ca level(P＜0.001).The excreta Ca levels decreased in the group supplemented with organic Zn compared to the group fed inorganic Zn(P＜0.001).The optimal dietary Ca levels were estimated as 0.90％,0.86％and 0.96％for birds fed organic Zn and 0.91％,0.92％and 1.06％for birds fed inorganic Zn using non-linear models based on the criteria of ADG,tibial length,and ATTRC of Ca,respectively.In conclusion,supplementing with organic Zn enhanced the growth performance of birds and reduced their calcium requirements from hatch to d 14.