本试验旨在研究不同钙水平饲粮添加维生素D₃对产蛋后期蛋鸡生产性能、蛋品质、胫骨质量和血浆钙磷代谢的影响。采用3×3因子设计，即3个钙水平（3.0%、3.5%和4.0%）和3个维生素D₃添加水平（0、2 500和5 000 IU/kg）。选取60周龄罗曼粉壳蛋鸡810只，随机分为9个组，每组6个重复，每个重复15只鸡。试验采用玉米-豆粕型饲粮，试验预试期1周，正试期6周。结果表明：1）与未添加维生素D₃组相比，添加维生素D₃组蛋鸡平均日采食量和产蛋率极显著升高（P<0.01），料蛋比、破蛋率和软壳蛋率极显著降低（P<0.01）。随着饲粮钙水平和维生素D₃添加水平的不断提高，鸡蛋的平均蛋重增加，脏蛋率减少，但差异不显著（P>0.05）。2）与未添加维生素D₃组相比，添加维生素D₃组蛋壳强度、蛋壳重和蛋壳比重极显著升高（P<0.01），蛋壳厚度显著提高（P<0.05），蛋黄重显著降低（P<0.05）。随着饲粮钙水平的升高，蛋壳强度呈现升高的趋势，但未达到显著水平（P>0.05）。3）不同钙水平饲粮添加维生素D₃对蛋鸡胫骨强度有极显著影响（P<0.01）；与未添加维生素D₃组相比，添加维生素D₃组胫骨强度极显著升高（P<0.01）；随着饲粮钙水平的升高，胫骨钙含量有升高的趋势，但差异不显著（P>0.05），而饲粮钙水平为4.0%时，胫骨强度显著高于饲粮钙水平为3.0%和3.5%时（P<0.05）。4）与未添加维生素D₃组相比，添加维生素D₃组蛋鸡血浆碱性磷酸酶活性极显著降低（P<0.01），血浆钙和磷含量极显著升高（P<0.01）；随着饲粮钙水平的升高，血浆钙和磷含量没有显著变化（P>0.05），与3.0%钙组相比，4.0%钙组血浆碱性磷酸酶显著降低（P<0.05）。结果显示，产蛋后期适当提高饲粮钙水平有利于蛋鸡生产性能，但维生素D₃缺乏会降低生产性能，甚至引起停产；饲粮添加2 500 IU/kg维生素D₃既能满足产蛋后期蛋鸡对维生素D₃的需求，同时又不造成资源的浪费，节约成本。

This experiment was to study the effects of different calcium level diets supplemented with vitamin D₃ on performance, egg quality, tibia quality and plasma calcium and phosphorus metabolism of laying hens in late laying period. A 3×3 factorial design was adopted in this experiment to design 3 calcium levels (3.0%, 3.5% and 4.0%)and 3 vitamin D₃ supplemental levels (0, 2 500 and 5 000 IU/kg). Eight hundred and ten 60-week-old healthy Lohmann laying hens were randomly assigned to 9 groups with 6 replicates per group and 15 hens per replicate. The corn-soybean meal diet was used in this experiment. The pre-trial period was 1 week and the official trial period was 6 weeks. The results showed as follows:1) compared with the group without adding vitamin D₃, the average daily feed intake and laying rate of hens in the vitamin D₃ supplemental group were extremely significantly increased (P<0.01), and the ratio of feed to egg, break egg rate and soft shell egg rate were extremely significantly decreased (P<0.01). With the increasing of dietary calcium level and vitamin D₃ supplemental level, the average weight of egg was increased, and the rate of dirty egg was decreased, but the difference was not significant (P>0.05). 2) Compared with the group without adding vitamin D₃, the eggshell strength, eggshell weight and eggshell proportion in the vitamin D₃ supplemental group were extremely significantly increased (P<0.01), the eggshell thickness was significantly increased (P<0.05), and the yolk weight was significantly reduced (P<0.05). With the increasing of dietary calcium level, the eggshell strength showed an increasing trend, but it was not significant (P<0.05). 3) Effects of different calcium level diets supplemented with vitamin D₃ on tibia strength were extremely significant (P<0.01). Compared with the group without adding vitamin D₃, the tibia strength in the vitamin D₃ supplemental group was extremely significantly increased (P<0.01). With the increasing of dietary calcium level, the calcium content in the tibia showed an increasing trend, but it was not significant (P<0.05). When the dietary calcium level was 4.0%, the tibia strength was significantly higher than that when the dietary calcium levels were 3.0% and 3.5% (P<0.05). 4) Compared with the group without adding vitamin D₃, the plasma alkaline phosphatase activity of hens in the vitamin D₃ supplemental group was extremely significantly decreased (P<0.01), and the contents of plasma calcium and phosphorus were extremely significantly increased (P<0.01). With the increasing of dietary calcium level, there was no significant change in the contents of plasma calcium and phosphorus (P>0.05). Compared with the 3.0% calcium group, the plasma alkaline phosphatase activity in the 4.0% calcium group was significantly decreased (P<0.05). In conclusion, appropriately increasing dietary calcium level is beneficial to the performance of laying hens in late laying period, but deficiency of vitamin D₃ reduces performance, even causes production shutdown. Supplementation of 2 500 IU/kg vitamin D₃ level can meet the requirement of vitamin D₃ in the later stage of laying hens without causing waste of resources and saving cost.