Effect Of Calcium Metabolism On Eggshell Quality In Caged Laying Hens

The calcium metabolism of the laying hens is the key of the study in the modern commercial production, nutritional regulation of calcium metabolism is the focus of the study. In order to better use of calcium metabolism and provide theoretical support to guarantee the healthy and production of laying hens, this study explores the effect of calcium metabolism on osteoporosis and eggshell quality of laying hens through five experiments.Exp.1, Effect of the alkaline diet(0.3% NaHCO3) on production performance and calcium metabolism of laying hens. Two hundred and forty Hy-line variety brown laying hens(25-W old) were randomly subjected to one of the following two groups for 50 weeks: the content of NaHCO3 in the diet was 0 and 0.3% respectively. The results showed that laying hens feeding with the alkaline diet for long-term increase the expression of the CaBPD28 K in duodenum during the initial period(P<0.05), which is relevant to the improved calcium absorption and increased shell thickness(P<0.05). Compared with the control group, long-term feeding with the alkaline diet have no significantly effect on egg weight and laying performance(P>0.05), but significantly decreased the egg weight and Daily egg production and Daily feed intake(P<0.05). There was no significant effect on the expression of the CaBPD28 K in duodenum and kidney and eggshell thickness and eggshell hardness during the late period(P>0.05).Exp.2, Effect of the alkaline diet(0.3% NaHCO3) on production performance and calcium metabolism of laying hens during the initial period. Two hundred and forty Hyline variety brown laying hens(25-W old) were randomly subjected to one of the following two groups for 20 weeks: the content of NaHCO3 in the diet was 0 and 0.3% respectively. The results showed that laying hens feeding with the alkaline diet for 20 weeks increase the expression of the CaBP-D28 K in duodenum during the initial period(P<0.05), which is relevant to the improved calcium absorption and increased shell thickness(P<0.05). Compared with the control group, 20 weeks feeding with the alkaline diet have no significantly effect on weight and laying performance and daily egg production(P>0.05), but significantly decreased the egg weight and feed egg ratio(P<0.05). The metabolic test show that the alkaline diet increase the expression of the CaBP-D28 K in duodenum during the initial period(P<0.05), which is consistent with experimental 1.Exp.3, Relationship between the eggshell quality and calcium metabolismon of the caged laying hens. We conducted a study on produce of the dark spots egg of Nongda No.3 and the sharpei egg of Hy-line variety brown laying hens. The results showed that there are individual differences on dark spots egg of Nongda No.3 variety laying hens and a negative correlation between egg weight and egg dark spots. Compared with the control group, the expression of the CaBP-D28 K and PMCA in the shell gland was decrease in Nongda No.3 variety laying hens with dark spots egg(P<0.05), which was lead to the reduction of calcium eggshell(P<0.05). That is the reason for the dark spots egg. Feeding with the mortierella cultures diet have significantly increased the expression of the CaBP-D28 K and PMCA in the shell gland and the eggshell thickness and decreased the grade of the dark sports egg in 10 days(P<0.05). The high expression of the CaBP-D28 K and PMCA in the shell gland lead to the disorder of calcium deposition and the more eggshell calcium(P<0.05), which is the main reason of the sharpei egg of Hy-line variety brown laying hens.Exp.4, Assessment of the osteoporosis of cage layer. Two hundred Hy-line variety brown laying hens(25-W old) were randomly subjected to be studied. The correlation between the bone quality(tibia, femur and keel) and the eggshell quality(eggshell thickness, eggshell hardness and eggshell proportion) was studied. The results showed that there is a positive correlation in weight, length and diameter between tibia and femur, the positive correlation between the length of femur and the eggshell weight(P<0.05), the negative correlation between the keel shape and the eggshell hardness, which means that the larger eggshell hardness may lead to the smaller keel shape(P<0.05). Reaction layers of bone quality by eggshell quality indicators, which rough estimate of the situation of osteoporosis of the laying hens.Exp.5, Effect of different levels of vitamin D on production performance and eggshell thickness of laying hens during the initial period. Three hundred and sixty Hy-line variety brown laying hens(23-W old) were randomly subjected to one of the following three groups for 20 weeks: the levels of vitamin D in the diet was 3200IU/kg, 6400IU/kg and 9600IU/kg respectively. The results showed that laying hens feeding with the 6400IU/kg vitamin D increase the eggshell thickness in the fifth week and the tenth week(P<0.05). Compared with the 3200IU/kg vitamin D group, 20 weeks feeding with the 6400IU/kg and 9600IU/kg vitamin D diet have no significantly effect on the laying rate, daily feed intake, egg weight and daily egg production(P>0.05). Immunization can reduce the thickness of eggshell and Vitamin D can mitigate this effect(P<0.05). Vitamin D can enhance the effect of immunization and significantly increase the antibody titer of the H9 and ND(P<0.05). The 9600IU/kg Vitamin D significantly increase the eggshell hardness during the seven days after the immunization(P<0.05).In conclusion, long-term feeding with the alkaline diet(0.3% NaHCO3) can increase the expression of the CaBP-D28 K in duodenum during the initial period, which is relevant to the improved calcium absorption and increased shell thickness, but there was no significant effect on the expression of the CaBP-D28 K in duodenum and kidney and eggshell thickness and eggshell hardness during the late period. We understand the detailed regulation of calcium metabolism with the regulation of protein for further study. Though the study of calcium metabolism, we successfully solved the problem on the produce of the dark spots egg of Nongda No.3 and the sharpei egg of Hy-line variety brown laying hens. Feeding with Cordyceps Xinkang diet have significantly increased the expression of the CaBP-D28 K and PMCA in the shell gland and the eggshell thickness and decreased the grade of the dark sports egg. The high expression of the CaBP-D28 K and PMCA in the shell gland lead to the disorder of calcium deposition and the more eggshell calcium, which is the main reason of the sharpei egg of Hy-line variety brown laying hens. Though the study of calcium metabolism, reaction layers of bone quality by eggshell quality indicators, which rough estimate of the situation of osteoporosis of the laying hens. Immunization can reduce the thickness of eggshell and Vitamin D can mitigate this effect. Vitamin D can enhance the effect of immunization and significantly increase the antibody titer of the H9 and ND.