Abstract

Egg weight (EW) is a key trait in both breeding and production for poultry. Although Zi geese demonstrate good egg-laying performance, they have relatively low EW. Identifying candidate genes and pathways associated with EW in geese is essential for enhancing genetic progress. In this study, 260 female Zi geese at 30 weeks of age were monitored individually for egg number (EN) and EW. Thirty geese, showing no significant differences in body weight and EN but significant variation in EW (P < 0.05), were selected and divided into a high egg weight (HEW) group (n = 15) and a low egg weight (LEW) group (n = 15). Egg quality traits were evaluated for both groups. From each group, six geese were randomly selected for serum biochemical profiling and untargeted metabolomics; four of these were further analyzed for transcriptomic data from the liver, ovary, and oviduct magnum. The results showed significant differences in albumen weight, yolk weight, and shell weight between HEW and LEW (P < 0.01). Serum biochemical analysis revealed higher levels of total cholesterol, triglycerides, estradiol, very low-density lipoprotein, and vitellogenin in the HEW group (P < 0.05). Transcriptomic analysis identified 278 differentially expressed genes (DEGs) in the liver, primarily enriched in antigen processing and presentation pathways, with ACACB, FDFT1, and HSPA2 highlighted as candidate genes. In the ovary, 18 DEGs were identified, with RBP1 as the key gene. In the oviduct magnum, 1,605 DEGs were enriched in protein processing in the endoplasmic reticulum, with HSPA8, HSP90AA1, and ST3GAL4 identified as candidate genes. Serum metabolomics revealed metabolites associated with EW, including cholesterol sulfate, l-tryptophan, indoxyl sulfate, and LysoPC(20:5(5Z,8Z,11Z,14Z,17Z)/0:0).