LAUSR

The tea polyphenol (TP) can improve the egg albumen quality in laying hens; however, our understanding of the molecular mechanisms and proteomic changes in the egg albumen remains limited. A total of 720 layers (35-wk-old) were allocated into 5 treatments with TP and were added at 0 (control), 200 (TP200), 400 (TP400), 600 (TP600), and 800 (TP800) mg/kg. It showed that 400 mg/kg TP increases albumen height and Haugh unit (quadratic effect, P < 0.01), while 400 mg/kg TP decreases gel strength, hardness, gumminess, and chewiness value in a quadratic manner (P = 0.01). Eggs from TP400-fed layers had highest reducing power and oxygen radical absorbance capacity, and lowest albumen malondialdehyde content (quadratic effect, P < 0.05). Through Tandem Mass Tag-based quantitative proteomics analysis, 258 proteins were identified and 31 differentially accumulated proteins in egg white affected by 400 mg/kg TP compared to control group, with 19 proteins upregulated and 12 proteins downregulated. A total of 11 binding proteins (A0A1D5PZE3, F1NTQ2, Q7SX63, F1NRV5, P24802, A0A1L1RM02, E1BTX1, A0A1L1RMF4, A0A1D5P1N3, A0A1L1RML6, A0A1L1RQF3), 9 immune response proteins (P10184, R4GI90, P01875, Q6IV20, Q64EU6, P02701, P08110, P0CB50, A0A1D5PQ63), and 3 cell redox homeostasis proteins (P0CB50, P20136, Q8JG64) were changed in albumen of laying hens fed TP400. The differentially expressed proteins mainly involved in pyruvate metabolism, cysteine and methionine metabolism, glutathione metabolism, glycolysis, and protein processing in endoplasmic reticulum pathway. The result gathered in this study suggested that the improving mechanism of TP on albumen quality may act through regulating binding mediation, immune function, and antioxidant activity-related proteins.