Regulation of Egg Quality by Methionine Selenium: Physicochemical and Structural Characteristics of EggShell, Egg Yolk, and Egg White

Selenium is an essential trace element in the body, and supplementing it in production can improve egg quality. Sixty healthy 48-week-old Hy-Line Brown laying hens were randomly assigned to two groups. In this study, the effects of dietary selenomethionine (SeMet) supplementation on the multi-dimensional characteristics of eggshell, egg white, and egg yolk were investigated, including their mechanical properties, mineral distribution, amino acid composition, microstructure, secondary structure, fatty acid composition, and lipidomic profiles. The results showed that compared with the control group (C-group), the air chamber height and egg shape index of the SeMet group (Se-group) were decreased by 21.51% and 1.54%, respectively, after 42 days of feeding. The Haugh units, eggshell strength, and eggshell color of the Se-group were increased by 10.21%, 29.24%, and 31.26%, respectively. This work leverages advanced analytical techniques for systematic sample characterization, including Fourier-transform infrared (FTIR) spectroscopy, cryogenic scanning electron microscopy (Cryo-SEM), and high-resolution tandem mass spectrometry-based lipidomics. Adding SeMet can increase the essential amino acid content and the total content of saturated and unsaturated fatty acids in egg yolk and egg white, thereby maintaining excellent protein patterns and reducing lipid hydrolysis in egg yolk. However, the addition of SeMet did not significantly affect the protein secondary structure or microstructure of egg yolk and egg white.