Bacteria and bacteriophage consortia modulate cecal SCFA production and host metabolism to enhance feed efficiency in ducks

Background: The gut microbiota critically influences poultry health, nutrition, feed efficiency (FE), and overall productivity. However, the relationship between gut microbes, including bacteria and bacteriophages, and FE in ducks remains underexplored. To address this, we integrated cecal 16S amplicon, metagenome, microbiota derived short-chain fatty acids (SCFAs) profiling, liver transcriptome, and serum metabolome data to illustrate the contribution of gut microbiome (bacteria and viruses) to duck FE. Results: We reconstructed viral genomes and prokaryotic metagenome-assembled genomes (MAGs), annotated their genes using comprehensive databases. Prokaryotic hosts of viruses were also predicted to understand virus-host dynamics within the gut ecosystem. Our results revealed that high-FE ducks have higher concentration of propionate and butyrate in cecum compared with low-FE ducks. The metagenome sequencing revealed distinct cecal microbiota profiles between two groups, with increased relative abundance of representative SCFA producers, especially Paraprevotella sp905215575 and Bacteroides sp944322345 , and enhanced SCFA-biosynthesis pathways in high-FE ducks. Virome genome assembly identified two bacteriophages encoding auxiliary metabolic genes (AMGs) involved in pyruvate metabolism, enhancing nutrient availability for host bacteria to produce SCFAs (e.g., temperate phage-encoded pyruvate phosphate dikinase) or exploiting host central metabolic pathways for viral replication (e.g., lytic phage-encoded formate C-acetyltransferase). Furthermore, these representative SCFA-producing bacteria and bacteriophage consortia were associated with serum metabolites (including L-histidine and 4-hydroxydecanedioylcarnitine) linked to duck FE. Conclusion: Collectively, these findings provide novel insights into the gut microbial factors regulating FE in ducks, offering potential strategies to optimize poultry nutrition and productivity.