Proteomic analysis of egg white proteins under different crude protein levels in laying hens' diets.

Abstract

Background: Dietary crude protein levels (DCPLs) have been shown to influence the quality of egg albumen, but the molecular implications of different DCPLs on the protein profile of albumen remain unclear. This study aimed to investigate the proteomic changes in the albumen of eggs from laying hens fed a corn-soybean meal-based diet with two different DCPLs (14.5% or 17.5%) to uncover the subtle proteomic variation in response to fluctuation of DCPLs.

Results: The egg weight and albumen quality of the DCPL_14.5 group were lower than those of the DCPL_17.5 group (P < 0.05). Proteomic analysis using two-dimensional electrophoresis and matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry identified 22 protein spots from seven different protein families with significant changes in abundance (P < 0.05). Sixteen proteins, including ovalbumin, ovotransferrin, ovomucoid, and ovoinhibitor precursor, were present at low levels in DCPL_14.5, and most of them had higher molecular weights than theoretical. The abundance of clusterin, ovoglobulin, and lipocalins increased; this may therefore be responsible for the decrease in albumen height and protein content in DCPL_14.5.

Conclusion: DCPL_14.5 diet downregulated 16 functional proteins such as ovalbumin and ovotransferrin and upregulated six regulatory factors such as clustered protein, resulting in a decrease in egg weight, albumen height, and protein content. The shifted molecular weight of ovalbumin implied ovalbumin polymer or modification, which would worsen egg white quality. © 2025 Society of Chemical Industry.