Integrated plasma and duodenal content metabolomics reveals metabolic mechanisms underlying residual feed intake differences in broilers.

Characterizing the cross-tissue metabolome of broilers with divergent residual feed intake (RFI) is essential to elucidate the biological basis of feed efficiency (FE). However, single-tissue studies offer limited insight into systemic metabolic crosstalk. Here, untargeted LC-MS/MS metabolomics was employed to analyze the plasma and duodenal content of high- and low-RFI broilers (n = 8/group). We identified 60 differential metabolites (P < 0.05, variable importance in projection (VIP) > 1) in plasma, which were significantly enriched in phenylalanine, tyrosine, and tryptophan biosynthesis, sphingolipid metabolism, glycerophospholipid metabolism, and glutathione metabolism pathways. In the duodenal content, 28 differential metabolites were screened, predominantly mapping to galactose metabolism as well as neurohumoral regulation and cellular network signal transduction pathways. Cross-tissue analysis revealed that Sorbitol was synchronously upregulated in both tissues, while 2-Hydroxyglutarate (2-HG) and N-α-acetyllysine were concurrently downregulated. Conversely, Dihydromyricetin (DMY) and Sphingosine-1-phosphate (S1P) were significantly upregulated in the duodenum but markedly downregulated in the plasma. Notably, S1P in sphingolipid metabolism emerged as a key metabolite bridging local duodenal immune/signaling status with systemic metabolic homeostasis. These coordinated shifts demonstrate that low-RFI broilers harbor enhanced systemic amino acid utilization, lipid partitioning, and antioxidant defenses. Overall, this integrated approach uncovers gut-systemic metabolic interplay driving broiler FE that single-tissue studies fail to capture.