Synergistic transcriptomic and metabolomic analyses in Zi geese ovaries with different clutch lengths

The clutch is defined as consecutive days of oviposition. Clutch length is an index that reflects ovulation persistence, and is highly correlated with egg production in birds. To identify the genetic markers associated with clutch length in geese, two consecutive experiments were conducted. In the first experiment, 200 Zi geese were selected, all 230 days old, were selected from the same batch and raised individually in the same environment. Data of egg-laying and clutch traits were recorded. After the laying period, three geese with the longest clutch lengths were selected to form the length clutch group (LCG) and three geese with the shortest clutch lengths were formed the short clutch group (SCG). In the second experiment, the ovaries of six geese were collected for transcriptomic and metabolomic analyses. The results showed that large clutch length (LCL) and average clutch length (ACL) were positively correlated with egg number (EN) (P < 0.01; r = 0.63 and 0.60, respectively). Large clutch number (LCN) was significantly correlated with the peak egg number (PEN) (r = 0.58, P < 0.01) and EN (r = 0.60, P < 0.01). EN, LCN, LCL, and ACL showed significant differences (P < 0.01) between the two clutch length groups. Transcriptomic analysis identified 424 differentially expressed genes (DEGs). Functional enrichment analysis revealed that these DEGs were mainly involved in neuroactive ligand-receptor interactions, ovarian steroidogenesis, and calcium signaling pathways. Further, AVPR1A, FGF14, and LHCGR were predicted as the key genes regulating LCL. Metabolomic analysis identified 349 differential metabolites (DMs) in both the positive and negative ion modes. Pyruvate, isocitric acid, D/L‑serine, 3-phospho-d-glycerate, succinate, glycine, and glutamic acid were identified as the key metabolites mainly enriched in the signaling pathways of the TCA cycle. Integration of transcriptomic and metabolomic data revealed critical gene-metabolite pairs, including ACSL4-phosphoenolpyruvate, implicated in LCL regulation. In summary, this study provides new insights into the genes and molecular markers affecting LCL in Zi geese.