TMT-based quantitative proteomic analysis unveils uterine fluid difference in hens producing normal and pimpled eggs

Eggshell is a crucial indicator of egg quality. Pimpled eggs (PE) a type of eggshell defect are characterized by low eggshell strength, leading to substantial financial losses. Eggshell formation occurs in the uterine fluid (UF), which contains the required ions and matrix proteins However, the underlying mechanisms of PE formation remain poorly understood. In this study, we analyzed the egg quality of PE, and normal eggs (NE) by examining the differences in UF from hens producing PE and NE (n = 6 each). This 2-wk-long assessment involved histomorphological and proteomics analyses. The results showed that NE had better eggshell quality compared to PE, and the uterus structure in PE hens was conducive to the formation of PE. Using quantitative proteomic analysis, we identified 68 differential abundance proteins (DAPs) in the UF of PE hens, including 9 key proteins related to ion transport, protein synthesis and folding, and immunity. Downregulation of CALM1 and SCNN1G proteins in PE hens might have negatively affected the calcium signaling pathway, decreasing the calcium amount in UF. Additionally, the PHB1 and TSN proteins may affect eggshell formation by regulating immune responses. Taken together, our results provide insights into the mechanism of PE production, with potential applications for enhancing eggshell quality.