Effects Of Tea Polyphenols On Performance And Egg Albumen Quality In Laying Hens

The purpose of this paper was to investigate the effects of different levels of tea polyphenols(TP)on laying performance,egg quality,egg gelling properties,albumen proteomics and smooth muscle movement of the oviduct magnum in laying hens.Screening the appropriate addition level of TP on laying hens and providing a theoretical basis for the application of TP in laying hen production.A total of seven hundred and twenty 35-week-old Lohmann laying hens were divided into 5 groups with 6 replicates per group and 24 hens per replicate.Control group was fed with basal diet,while the other 4 groups were fed 200,400,600 and 800mg/kg TP based on the basal diet,respectively.The test lasted for 8 weeks.The results showed that:(1)At the 4th week,the addition of TP significantly increased the egg weight(P<0.05);egg albumen height(P<0.05)and the Haugh unit(P<0.01)were significantly increased,With the TP addition increasing,the egg weight,albumen height and Haugh unit showed a quadratic curve trend(P<0.01).(2)Gel strength,hardness,adhesiveness and chewiness were significantly decreased after adding TP in diet(P<0.05),and showed a quadratic curve trend with the increase of TP addition level(P<0.05).Adding 200,400,and 600mg/kg TP,the egg albumen showed porous,loose,irregular and reticular structure.(3)TP supplementation significantly decreased the concentration of copper and manganese in egg albumen(P<0.05).There was no significant difference of zinc and iron concentration.(4)A total of 258 proteins were identified and 31 differentially accumulated proteins in egg white affected by 400 mg/kg TP,with 19 proteins up-regulated and 12 proteins down-regulated.11 binding proteins,9 immune response proteins and 3 cell redox homeostasis protein were changed in albumen of laying hens fed 400 mg/kg TP.The differentially expressed proteins mainly involved in pyruvate metabolism and cysteine and methionine metabolism,glutathione metabolism,glycolysis,and protein processing in endoplasmic reticulum pathway.(5)The addition of TP had a significant effect on the ratio of the area of acinar lumen to the total area of acinar in the oviduct magnum(P<0.01).The addition of TP had no significant effect on serum calcium of laying hens,but significantly increased the activity of myosin light chain kinase in the oviduct magnum.In summary,the addition of tea polyphenols to laying hens could increase egg weight,albumen height and Haugh units,reduce egg gelling strength,hardness,adhesiveness and chewiness.It also decreased the content of copper and manganese in albumen.After the addition of tea polyphenols,the egg white gel structure turn into the network structure with loose porous and irregular.The addition of 400 mg/kg tea polyphenols resulted in up-regulation of 19 proteins in the egg white and down-regulation of 12 proteins.The addition of tea polyphenols(400 mg/kg)has an improved effect on egg white quality.