Regulation Mechanism Of Glucosamine On Eggshell Quality In Laying Hens

Previous studies have shown that glucosamine?GluN?can reduce the loss of bone,promote the absorption of calcium,increase the bone density of laying hens,and improve the quality of eggshell.However,the regulation mechanism of GluN on the quality of eggshell is still unclear.In view of this,the regulation mechanism of GluN on the laying performance,egg quality,serum biochemical indexes,eggshell quality and and the expression of relevant genes in uterus of caged laying hens was investigated to provide theoretical basis for the rational application of GluN in the diet of laying hens.The research is divided into two parts:Experiment 1:Effects of GluN on laying performance,serum biochemical indexes,egg quality and gene expression in laying hens during onset period.Single factor experiment design was adopted to select 600 Lohmann laying hens aged120-day with similar laying rate?50%?were randomly divided into 4 groups with 10replicates per group and 15 laying hens per replicate,a total of 150 Laying hens.Hens in each group were fed with 0%,0.2%,0.4%and 0.6%GluN diets.Pre-feeding for 7days and trial for 30 days.The results show that:?1?The ADFI of laying hens increased gradually with the increase of GluN addition,and the intake of laying hens in 0.4%and 0.6%GluN ware significantly higher than that in the control group?P?0.05?.The laying rate and egg mass of 0.6%GluN were significantly higher than other groups?P?0.05?.0.2%and 0.6%GluN significantly improved feed conversion efficiency of laying hens?P?0.05?.Adding GluN had no significant effect on the abnormal egg rate in lyaing hens during the onset period?P?0.05?.?2?GluN had no significant influence on the short-diameter,egg-shape index,ratio of yolk and yolk color in laying hens during the onset period?P?0.05?.The albumen height of0.4%⁰.6%GluN increased significantly?P?0.01?.?3?GluN had no significant effect on the strength,mass and thickness of the eggshell?P?0.05?,but 0.6%GluN highly promoted the deposition of calcium and phosphorus?P?0.01?.?4?GluN increased serum Ca?P?0.01?,decreased TRAP activity and PTH content linearly?P?0.05?,and had no significant effect on E₂,CT,il-6 and PGE₂ contents in laying hens during the onset period?P?0.05?.?5?GluN upregulated OVAL gene expression and increased OPN gene expression?P?0.01?,and 0.6%GluN upregulated OC-116 gene expression in laying hens during the onset period?P?0.01?.Experiment 2:Effects of GluN on laying performance,serum biochemical indexes,egg quality and gene expression in laying hens during peak period.Single factor experiment design was adopted to select 750 Lohmann laying hens aged180-day with similar laying rate were randomly divided into 5 groups with 10replicates per group and 15 laying hens per replicate,a total of 150 Laying hens.Hens in each group were fed with 0%,0.2%,0.4%,0.6%and 0.8%GluN diets.There were7 days and 90 days for pre-trial and trial.The results show that:?1?GluN can promote the feed intake of laying hens during peak period.ADFI of laying hens during peak period increased gradually with the extension of time,and the feed intake of0.4%GluN was significantly higher than other groups?P?0.05?.GluN had no significant effect on the laying rate in laying hens during the onset period?P?0.05?,and the egg weight increased at 60⁹0 days?P?0.05?,and the highest egg weight was 0.4%GluN group.?2?GluN had no effect on egg long-diameter,short-diameter,egg shape index,egg yolk ratio,egg yolk color,albumen height and haugh unit in laying hens during the onset period?P?0.05?,0.2%⁰.6%GluN increased the yolk weight of at 90th day?P?0.05?.?3?0.2%⁰.6%GluN significantly increased the eggshell thickness and eggshell strength at 60th and 90th day?P?0.01?,improved the eggshell ratio and eggshell mass at 90th day?P?0.01?,promote the eggshell calcium and phosphorus deposits?P?0.01?.Eggshell strength,thickness,proportion of eggshell,eggshell mass,eggshell calcium and phosphorus were decreased when GluN add up to 0.8%.?4?The regulation effects of GluN on serum calcium metabolism was gradually strengthened with the extension of time?>60 days?,showing a tendency of first increasing?decreasing?and then decreasing?increasing?with the level of GluN addition.0.6%GluN improved the serum calcium of laying hens at 60th day?P?0.05?,and 0.2%⁰.6%GluN increased the serum content at 90th day?P?0.01?,while0.8%GluN reduced the serum calcium.GluN stimulates the E₂ secretion in laying hens during peak period?P?0.01?;0.4%and 0.6%GluN significantly?P?0.05?or extremely significantly?P?0.01?inhibited the secretion of serum TRAP,TPH,il-6and PGE₂ and increased CT content at 90th day?P?0.05?.The serum TRAP,TPH,il-6 and PGE2 were increased when GluN add up to 0.8%.?5?GluN significantly?P?0.05?or extremely significantly?P?0.01?upregulated the expression of OPN and OC-116 genes when the action time was more than 60 days.02%⁰.6%GluN significantly increased the OCX-36 gene expression of uterus at 90th day?P?0.05?,and 0.6%GluN increased the OCX-32 gene expression?P?0.05?too.GluN had no effect on OVAL gene in laying hens during peak period?P?0.05?.Conclusion:?1?GluN can promote the feed intake,improve the laying rate,albumen height and haugh unit,increase the egg weight,promote the deposition of calcium and phosphorus in the eggshell,improve the serum calcium concentration,inhibit TRAP activity,and reduce PTH secretion of laying hens during onset period.?2?GluN can promote the feed intake,increase the yolk weight,eggshell mass,eggshell ratio,eggshell calcium and phosphorus mass,increase the eggshell thickness and eggshell strength,promote the E₂ and CT secretion,inhibited the TRAP activity,reduce the PTH,il-6 and PGE₂ content,and increase the serum calcium concentration of laying hens during peak period.?3?GluN up-regulated the expression of OVAL,OPN and OC-116 genes in laying hens during onset period.GluN increased the expression of OPN,OC-116,OCX-32 and OCX-36 genes in laying hens during peak period.The pathway of GluN regulating eggshell quality:GluN stimulate the secretion of E₂ and CT,inhibit the activity of the TRAP,reduce the secretion of PTH,IL-6 and PGE₂ to improve the serum calcium content,thus upregulate the expression of OPN,OC-116,OCX-32 and OCX-36 gene in uterus,increases the secretion of calcium in the eggshell gland,promote the calcium deposit of eggshell,increase the calcium content of eggshell,increase the ratio and the thickness of eggshell,and enhance the strength of eggshell finally.Under the conditions of this experiment,the appropriate addition amount of GluN was 0.6%.