| Improving the quality of egg shell has always been a hot issue in the poultry industry.Due to the disorder of calcium metabolism in the body,the incidence of osteoporosis in cage layer chickens is high,the quality of eggshell is poor,and the breaking rate of eggs can reach 5%-10%under the modern culture mode.Therefore,the quality of egg shell has become an important factor affecting the benefit of poultry industry.So we designed this test,added 25-(OH)D3,vitamin C,and 4,7-dihydroxyisoflavones into the basic diet of laying hens,to study the production performance,eggshell quality,antioxidant capacity and calcium metabolism of laying hens.Investigating the biological mechanism caused by 25-(OH)D3,vitamin C and 4,7-dihydroxyisoflavone,which could provide a foundation for poultry industryIn this study,0 μg/kg,10 μg/kg,or 20 μg/kg 25-(OH)D3,0 mg/kg,50 mg/kg or 100 mg/kg vitamin C,and 0 mg/kg,5 mg/kg or 10 mg/kg 4,7-dihydroxyisoflavone were added to the basal diet,respectively,using a three-factor,three-level orthogonal test(L9(3 4)).In this experiment,972 50-week-old Jingfen layer hens were randomly divided into 9 treatment groups,with 6 replicates in each treatment group and 18 chickens in each repeat.Except one week for pre-feeding,the trial last six weeks.The main research results are as follows:1 Production performance and egg qualityThe addition of different levels of 25-(OH)D3,vitamin C and 4,7-dihydroxyisoflavone had no significant effect on the feed intake,egg-shaped index,height of the protein,color of the yolk and the Hahn’s unit(P>0.05).Adding 5mg/kg 4,7-dihydroxyisoflavone to the basal diet significantly increased egg production after the 4th week(P<0.05).Add 50mg/kg VC,5mg/kg 4,7-dihydroxyisoflavone,layer production rate is the highest,but the level of VC should not be too high,when the addition amount reached 100mg/kg,production rate will be reduced.The average egg weight increased with the addition of 25-(OH)D3,and increased significantly with the addition of 20 μg/kg(P<0.05)2 Eggshell qualityAdding different levels of 25-(OH)D3,vitamin C and 4,7-dihydroxyisoflavone significantly increased eggshell strength and thickness(P<0.05).Eggshell mastoid height was significantly affected by 25-(OH)D3(P<0.05).According to the analysis results of the main effect on eggshell strength,the optimal combination of these three substances is 20 μg/kg 25-(OH)D3,50 mg/kg vitamin C and 5 mg/kg 4,7-dihydroxyisoflavone3 Oxidation performanceThe addition of different levels of 25-(OH)D3 had no significant effect on antioxidant indexes such as T-AOC,CAT,SOD,GSH-Px.(P>0.05).The serum MDA level increased with the addition of 25-(OH)D3,when the addition amount reached 20μg/kg,MDA concentration increased significantly(P<0.05).Adding different levels of vitamin C significantly increased CAT level(P<0.05)and significantly decreased MDA concentration(P<0.05).Compared with without vitamin C,SOD level was significantly increased when the added level was 50mg/kg(P<0.05).The addition of 4,7-dihydroxyisoflavones at different concentrations significantly increased the levels of CAT and GSH-Px(P<0.05),and significantly reduced the levels of MDA(P<0.05).The results showed that adding vitamin C and 4,7-dihydroxyisoflavone in different concentrations could improve the antioxidant level of the body4 Calcium transport and depositionAdding 20 μg/kg 25-(OH)D3,50 mg/kg vitamin C and different levels of 4,7-dihydroxyisoflavones significantly increased the serum level of 1,25-(OH)2D3(P<0.05).With the increase addition of 4,7-dihydroxyisoflavone,the content of estradiol in serum increased significantly(P<0.05).Adding 20 μg/kg 25-(OH)D3 significantly increased the content of calcium in eggshell(P<0.05),but had no effect on calcium and phosphorus deposition in tibia(P>0.05).The addition of 50 mg/kg vitamin C and 5 mg/kg 4,7-dihydroxyisoflavone significantly increased the content of calcium in tibia(P<0.05),but had no effect on calcium and phosphorus deposition in eggshell(P>0.05).It was suggested that 25-(OH)D3 could increase calcium deposition in the egg shell in the uterus,while vitamin C and 4,7-dihydroxyisoflavone could increase calcium deposition in the tibia5 Calcium metabolism-related genesAdding 20μg/kg 25-(OH)D3 significantly increased the expression levels of CaBP-D28k and VDR in duodenum,as well as CaBP-D28k and 1α hydroxylase in kidney(P<0.05).The addition of 50 mg/kg vitamin C significantly increased the expression of CaBP-D28k in duodenum and 1α hydroxylase in kidney(P<0.05).The addition of 4,7-dihydroxyisoflavone had no effect on calcium-transport-related genes in duodenum and kidney(P>0.05).When the addition amount of 4,7-dihydroxyisoflavone was 5 mg/kg,the expression levels of ER and CA2 genes in uterus were significantly increased(P<0.05),but with the increase of the addition amount,the expression levels of ER and CA2 were significantly decreased(P<0.05).The results showed that 25-(OH)D3 promoted calcium ion deposition in uterus by increasing calcium absorption in uterus and kidney.Vitamin C can enhance the calcium absorption of duodenum by increasing the content of 1α hydroxylase in the kidney.4,7-dihydroxy isoflavones promote the production of enzymes related to the formation of calcium carbonate crystals in the uterus by increasing estrogen levels in the bodyIn summary,the following conclusions can be drawn from this experiment(1)Adding 20 μg/kg 25-(OH)D3 can improve average egg weight,adding 5 mg/kg 4,7-dihydroxyisoflavone can increased egg production.(2)Adding 20 μg/kg 25-(OH)D3,50 mg/kg vitamin C and 5 mg/kg 4,7-dihydroxyisoflavone can improve the production performance and eggshell quality of laying hens.(3)Adding vitamin C and 4,7-dihydroxyisoflavone can improve the antioxidant capacity of the body.(4)25-(OH)D3 affects the quality of the eggshell by promoting calcium absorption in the duodenum and the kidney;vitamin C promotes the expression of 1 hydroxylase in the kidney to promote the expression of CaBP-D28k in the duodenum and the deposition of calcium ions in the tibia;4,7-dihydroxyisoflavone promotes the synthesis of calcium carbonate crystals in the uterus and the deposition of calcium ions in the tibia by improving the estrogen level. |
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