Effects Of Different Calcium Levels Diet Supplemented With Vitamin D3 On Performance,Egg Quality,Calcium Metabolism Of Laying Hens In Late Laying Period

This experiment was divided into two phasesto investigate the effects of different calcium levels diet supplemented with vitamin D₃on performance,egg quality,calcium metabolism of laying hens on the 60-66 weeks in the first stage,and the effects of adding 2500IU/kg vitamin D₃on performance,egg quality and calcium metabolism of the 67-72 weeks laying hens in vitamin D₃deficiency diets.Phase 1:To study the effects of different calcium levels diet supplemented with vitamin D₃on performance,egg quality,calcium metabolism of laying hens in late laying period.A 3×3 factorial design was adopted with 3 calcium levels（3.0%,3.5%,4.0%）and 3 vitamin D₃levels（0IU/kg,2500IU/kg,5000IU/kg）.Eight hundred and ten 60-week-old healthy Lohmann laying hens were randomly assigned to 9groups with 6 replicates per group and 15 hens per replicate.The experiment lasted for 6 weeks.Experimental laying hens were fed corn-soybean meal.The results showed:（1）The addition of vitamin D₃group was significantly higher than that of group 0on the average intake and egg production rate（P<0.01）.There was a significant decrease in the feed conversion,the ratio of broken egg and soft shell（P<0.01）.With the increase of calcium level and vitamin D₃level,the average egg weight increased（P>0.05）,and the rate of dirty eggs decreased（P>0.05）,but the difference was not significant.（2）Adding vitamin D₃group was significantly higher in eggshell strength,eggshellweight and eggshell proportion than group 0（P<0.01）.The thickness of eggshell was significantly increased（P<0.05）.Adding vitamin D₃group significantly reduced the yolk weight（P<0.05）.With the increase of calcium content,the strength of eggshell showed an increasing trend（P>0.05）.（3）The addition of 4%calcium significantly reduced alkaline phosphatase（P<0.05）.With the increase of calcium content,the content of calcium,phosphorus and calcitonin did not change significantly（P>0.05）.The addition of vitamin D3group significantly reduced alkaline phosphatase（P<0.01）.（4）4%calcium group showed a significant decrease in the uterine carbonic anhydrase activityand jejunal calcium binding protein（P<0.01）.There was a significant increase in uterine calcium binding protein（P<0.01）.With the increase of calcium level,liver calcium binding protein significantly decreased（P<0.05）.The low calcium diet resulted in the decrease of the calcium atpase activity in the cavities,the calcium atpase activities in the uterus and liver were increased,and the effect was very significant（P<0.01）.The 5000IU/kg vitamin D₃group showed a significant increase in liver calcium binding protein,the activities of uterine calcium atpase and carbonic anhydrase（P<0.01）.When vitamin D₃deficiency,the carbonic anhydrase activity in jejunal was the lowest value,and the difference was significant（P<0.01）.With the addition of vitamin D₃,the uterine calcium binding protein and liver calcium atpase activity was significantly increased（P<0.01）.（5）The calcium content of eggshell increased significantly with the increase of calcium level（P<0.05）,but there was no effect on the phosphorus content of the eggshell（P>0.05）.The vitamin D₃group was significantly higher than the 0 vitamin D₃group（P<0.01）,but there was no effect on the phosphorus content of the eggshell（P>0.05）.（6）Adding vitamin D₃group was significant higher in tibial strength than 0vitamin D₃group（P<0.01）.With the increase of calcium level,the tibia calcium content increased,but the difference was not significant（P>0.05）,while the calcium content was 4%,which significantly increased the tibial strength（P<0.05）.Phase 2:A total of 252 67-week-old healthy Lohmann laying hens were randomly assigned to 3 groups（3.0%Ca+2500 IU/kg VD₃,3.5%Ca+2500IU/kg VD₃,4.0%Ca+2500 IU/kg VD₃）with 6 replicates per group and 14 hens per replicate.The experiment lasted for 6 weeks.The results showed:（1）Supplementation of 2500IU/kg VD₃did not affect the average intake,feed to egg ratio,egg production rate,soft shell egg rate,dirty egg rate,and broken egg rate（P>0.05）.However,the average egg weight was significantly reduced when birds fed 3%calcium diet（P<0.05）.With the increase of the calcium level,the feed to egg ratio and the dirty egg rate decreased and the egg production rate increased（P>0.05）.（2）Supplementation of 2500IU/kg VD₃did not affect the eggshell strength,yolk color,eggshell weight,protein height,egg yolk weight,Harvard unit,and eggshell proportion（P>0.05）.However,there was a significant effect on eggshell thickness（P<0.05）.With the increase of calcium content,the thickness of eggshell was significantly increased（P<0.05）.（3）Adding 2500IU/kg vitamin D₃was significantly unaffected serum calcium,blood phosphorus,alkaline phosphatase,and calcium metabolism hormone（P>0.05）.（4）The addition of 2500IU/kg vitamin D₃had a significant effect on the jejunal carbonic anhydrase activity,the calcium binding protein,the uterine calcium atpase activity,and the calcium atpase activity in the liver（P<0.05）.There was no significant effect on calcium binding protein and hepatic calcium combined protein（P>0.05）。3%calcium diet resulted in a significant decrease in the activity of the jejunum carbonic anhydrase and calcium atpase,calcium binding protein in jejunum,and calcium atpase activity in liver（P<0.05）.With the increase of calcium level,the calcium atpase activity in uterus increased significantly（P<0.01）.（5）Adding 2500IU/kg vitamin D₃had no significant effect on phosphorus content of egg shell（P>0.05）.The calcium content of eggshell was significantly affected（P<0.01）.3%calcium diet group significantly decreased in calciumcontent of eggshell（P<0.01）。（6）Adding 2500IU/kg vitamin D₃had no significant effects on tibia strength and tibia phosphorus content（P>0.05）.The calcium content of tibia（P<0.01）was significantly increased by 3.5%calcium and 4%calcium group.In conclusion,Vitamin D₃deficiency has a negative effect on the production performance of laying hens,and even caused the production of egg-laying hens to stop production.Supplementation of 2500IU/kg vitamin D₃can restore the egg yield,egg rate and intake.In the later stage of laying hens,it is better to improve the calcium level of the eggs and to improve the health and egg quality of laying hens.The 2500IU/kg vitamin D₃level can meet the requirement of vitamin D₃in the later stage of laying hens,without causing waste of resources and saving cost.