Effect Of Methionine Hydroxy Analog Chelated Zinc On Production Performance,Immune Function,Mineral Deposit And Metabolism Of Hens At Late Laying Stage

The experiment was conduct to evaluate the effects of methionine hydroxyl analog chelated zinc on production performance,egg quality,eggshell quality,immune function,anti-oxidant capacity,mineral deposit,the activity of Zn-contenting enzymes,as well as the expression level of metallothionein of laying hens in the late stage,which aimed at provide reference for methionine hydroxyl analog chelated zinc optimum dosage in hens production.Exp.1 Effects of methionine hydroxyl analog chelated zinc on production performance of laying hensA total of 960 layers?Hy-Line Grey,57-wk-old?were randomly divided into 4 groups according to body weight and laying egg rate,with 8 replicates per treatment,and each group had 8 replicates of 30 hens.All birds were fed a basal diet?Zn:35.08 mg/kg?without extra zinc for 2 weeks.During the ensuing 14 wk,four levels of Zn?ZnSO₄:80 mg/kg;MHA-Zn:20,40,80 mg/kg?were added to the diet.The results showed that:?1?No significant difference were found in laying rate,average egg weight,average daily feed intake and feed/egg ratio?P>0.05?.?2?Neither sources nor level of zinc affect eggshell index,albumen height,yolk color,yolk/albumen and haugh unit?P>0.05?.?3?Dietary supplementary with40 or 80 MHA-Zn significantly improved eggshell quality,including promote eggshell thickness,eggshell strength,eggshell weight percent,eggshell density and decreased broken egg rate?P<0.05?.?4?With the adding of MHA-Zn,the tibia strength was increasing and added 40 or 80 MHA-Zn could improve tibia strength at the age of 66 to 72.Exp.2 Effects of methionine hydroxyl analog chelated zinc on immune function and anti-oxidant capacity of laying hensExperiment design of Exp.2 is the same with Exp.1 The results showed that:?1?There were no significant difference in IgG,IgM and antibody titer of ND between these four treatments?P>0.05?,while dietary supplementary with 40 mg/kg MHA-Zn significantly increased antibody titer of H₅?P<0.05?;?2?Compared with inorganic zinc,MHA-Zn could improve anti-oxidant capacity,including increased the activity of Cu/Zn-SOD and T-AOC in serum and liver,decreased the content of MDA?P<0.05?.Exp.3 Effects of methionine hydroxyl analog chelated zinc on trace elements deposit of laying hensExperiment design of Exp.3 is the same with Exp.1 The results showed that:?1?Both sources and level of zinc significantly affected Zn and Ca content of tibia?P<0.05?;dietary supplementary with 40 or 80 mg/kg MHA-Zn significantly improved Zn content of yolk in the late laying stage?P<0.05?,while no significant difference were found in Zn and Cu content of albumen and Cu content of yolk?P>0.05?;no significantly different were found in Cu content of liver,but,the Zn content of liver increased with the increasing of Zn level.?2?Both sources and level of zinc significantly affected the activity of CA of liver?P<0.05?,the activity of AKP increased with the zinc level increasing,and dietary supplementary with 80mg/kg ZnSO₄ and MHA-Zn got the highest activity.?3?Dietary supplementary with 40 or 80MHA-Zn significantly promote the expression of MT in liver,while dietary supplementary with 20 mg/kg MHA-Zn decreased the expression significantly?P<0.05?.Conclusions:?1?Dietary supplementation with 40 or 80 mg/kg MHA-Zn can significantly improve eggshell quality,as increasing eggshell thickness,eggshell strength,eggshell weight percentage and eggshell density,while decrease broken egg rate.A lower dosage of MHA-Zn have no impact on laying performance.?2?Dietary supplementation with 40 or 80 mg/kg MHA-Zn can significantly improve the antibody titer of H₅,and can delay the decreasing level of ND,Ig M and Ig G.Besides,organic zinc can improve the content of Cu/Zn-SOD,T-AOC of tibia and serum,while decreased the content of MDA of serum.?3?Dietary supplementation with 40 mg/kg MHA-Zn can promote the Ca and Zn deposit of tibia and liver,as well as Zn content of yolk and liver,while decrease the Zn content of munure.Zinc methionine,as an additive for reducing organic trace elements,has obvious advantages over inorganic zinc in improving egg quality and tibia quality,enhancing immune function and reducing excretion of zinc in feces.This may be related to the increase of CA,AKP content and the expression of MT-mRNA in the liver of laying hens.