| The performance and egg quality will decrease markedly with the age in the laying hens.Therefore,increasing both the performance and egg quality could have significant positive economic implications.Vitamin E is a natural antioxidant with many biological functions,but little is known about the bioavailability of vitamin E applied in laying hens during the late laying period.The aim of this study was to investigate the effects of natural vitamin E on performance,egg quality,and antioxidant function of laying hens during late laying period in order to provide a theoretical basis and technical reference for the application of natural vitamin E in laying hens.The study includes three trials and the results are presented as follows:The first trial was conducted to investigate the effects of natural vitamin E on the production performance,serum biochemical indices,and digestive enzymes activities of laying hens during late laying period.A total of 270 66-week-old Hyline-Brown hens were randomly assigned to 3 groups,and each group had 6 replicates of 15 birds each.The birds were fed a basal diet(control group),and the basal diet supplemented with 100 mg/kg and 200 mg/kg natural vitamin E for 42 d,respectively.Compared with the control group,the supplementation of 100 and 200 mg/kg natural vitamin E in the diet increased the egg production by 4.13%and 3.01%,respectively(P<0.05),and decreased the concentration of low density lipoprotein cholesterol(LDL-C)in serum of laying hens(P<0.05).The addition of natural vitamin E in the diet increased the content of vitamin E in the liver(P<0.05).Compared with the 100 mg/kg natural vitamin E inclusion group,200 mg/kg natural vitamin E significantly increased the content of vitamin E in the serum(P<0.05).The natural vitamin E supplementation increased the activities of jejunal lipase and pancreatic trypsin(P<0.05).Moreover,the supplementation of natural vitamin E increased the relative length of j ejunum(P<0.05).The second trial was conducted to investigate the effects of natural vitamin E on immunity and antioxidant abilities of laying hens during the late laying period.The trial design and materials were the same as those in the first trial.The results showed that there were no significant differences in concentrations of serum immunoglobulin A(IgA),immunoglobulin G(IgG),and immunoglobulin M(IgM),and jejunal secretory immunoglobulin A(SIgA),IgG,and IgM content among groups(P>0.05).Dietary natural vitamin E supplementation increased the superoxide dismutase(SOD)activity in the serum,catalase(CAT)activity in the jejunal mucosa,and glutathione peroxidase(GSH-Px)activity in jejunal mucosa and liver(P<0.05),and decreased the malondialdehyde(MDA)content in the serum and liver(P<0.05).Moreover,dietary supplementation with natural vitamin E increased the mRNA expression of nuclear factor-erythroid 2-related factor-2(Nrf2),copper/zinc superoxide dismutase(Cu/Zn-SOD)and glutathione peroxidase 1(GSH-Px1)(P<0.05).The third trial was conducted to investigate the effects of dietary supplementation with natural vitamin E on egg quality with different storage time of laying hens during the late laying period.The trial design and materials were the same as those in the first trial.The results showed that dietary supplementation with natural vitamin E significantly increased the albumen height,haugh unit and shell thickness at 21 d(P<0.05).Compared with control group,the eggs of the 200 mg/kg natural vitamin E group had a higher protein height after 14-day of storage(P<0.05).The diet supplemented with natural vitamin E had no effects on the weight loss rate of eggs at different stage times(P>0.05).However,natural vitamin E addition significantly increased the glutathione(GSH)level and reduced the MDA content of egg yolk(P<0.05).In conclusion,the results indicated that dietary natural vitamin E inclusion increased egg production to some extent,increased egg quality,serum and liver vitamin E deposition and antioxidant capacity of laying hens during the late laying period.Moreover,under the conditions of this study,the 200 mg/kg natural vitamin E inclusion in the diet was pronounced than of the addition of 100 mg/kg natural vitamin E in improving the egg quality and antioxidant capacity in laying hens. |
