Transcriptomic and Metabolomic Analyses Provide Insights into the Effects of Dietary Nanoselenium on Translucent Egg Formation in Laying Hens

Abstract Eggshell translucency is a common eggshell defect characterized by water-mark-like spots visible to the naked eye under natural light, which can negatively affect consumer acceptance and the market value of eggs. Nanoselenium (Nano-Se) is a novel selenium form with the potential to improve egg quality. In this study, the translucent egg formation and the effects of nano-Se supplementation were investigated using transcriptomic and metabolomic analyses. Translucent eggs showed a higher moisture content and lower eggshell calcium content, along with a thicker and looser mammillary layer and reduced eggshell membrane crude protein and essential amino acid (EAA) contents. Dietary nano-Se reduced translucent egg formation and eggshell moisture, improved egg freshness and mammillary ultrastructure, and altered eggshell membrane amino acid profiles. Transcriptomic analysis revealed the enrichment of calcium signaling- and oxidative phosphorylation-related pathways, while metabolomic analysis highlighted alterations in amino acid biosynthesis and metabolism. Overall, dietary Nano-Se reduced translucent egg formation, accompanied by improved eggshell ultrastructure, reduced eggshell moisture accumulation, and altered eggshell membrane amino acid profiles, which were associated with changes in uterine calcium transport, antioxidant capacity, and amino acid metabolism.