Integrated Transcriptomic and Metabolomic Profiling Reveals Candidate Genes and Metabolites Associated with Abdominal Fat Deposition in Pekin Ducks

Abdominal fat deposition is an important economic trait in meat ducks, but the molecular mechanisms underlying individual variation in abdominal fat rate remain unclear. In this study, abdominal fat traits were measured in 316 male Pekin ducks, from which six ducks with high abdominal fat rates and six ducks with low abdominal fat rates were selected for transcriptomic and metabolomic analyses of abdominal adipose tissue. Considerable individual variation in abdominal fat rate was observed in the population, providing a phenotypic basis for divergent group selection. Transcriptomic analysis identified 549 differentially expressed genes, including 181 upregulated and 368 downregulated genes in the LF group relative to the HF group. Functional enrichment analysis revealed that these genes were mainly involved in lipid metabolism, fatty acid metabolism, glycerolipid and glycerophospholipid metabolism, triglyceride metabolism, cholesterol metabolism, lipid transport, and the PI3K-Akt signaling pathway. Among the representative candidate genes, FASN, AGPAT1, ELOVL4, PEMT, PLTP, LCAT, LIPA, and LIPG were upregulated, whereas FABP5 and FABP6 were downregulated in the HF group relative to the LF group. Metabolomic analysis detected 222 differential metabolic features. The putatively annotated metabolites among these features were mainly associated with cholesterol metabolism, primary and secondary bile acid biosynthesis, bile secretion, steroid biosynthesis, alpha-linolenic acid metabolism, PPAR signaling, and adipocytokine signaling pathways. Integrated transcriptomic and metabolomic analysis further highlighted potential gene–metabolite modules related to lipid synthesis/remodeling, cholesterol–bile acid metabolism, and lipid signaling. Overall, these findings provide an exploratory molecular framework for subsequent validation of abdominal fat deposition in Pekin ducks. The proposed candidate genes and putatively annotated metabolites require validation in independent duck populations and further functional studies.