Oregano essential oil-driven rumen microbiome metabolism potentially regulates intramuscular fatty acid profile in Holstein bulls through liver lipid metabolism

Abstract
Background
While oregano essential oil (OEO) has been used as a feed additive in ruminant production and shown to positively influence meat quality, its effects on the rumen microbiota and host liver metabolism, and the potential mechanisms linking these to intramuscular fatty acid deposition remain poorly understood. This study applied a multi-omics approach, including metagenomics, metabolomics, and transcriptomics, to investigate how dietary OEO influences key ruminal microbes and metabolites, as well as hepatic genes and metabolites associated with fatty acid metabolism in Holstein bulls.
Results
Twelve Holstein bulls were randomly assigned to two dietary treatments: a basal diet (CON) and a basal diet supplemented with OEO. OEO supplementation significantly increased the content of total polyunsaturated fatty acids, linoleic acid and α-linolenic acid in muscle (P < 0.05). Metagenomic analysis revealed that OEO increased the abundance of the phylum Bacteroidetes and the genus Prevotella in the rumen. Ruminal metabolomics further identified differential lipid metabolites, primarily fatty acyls and glycerophospholipids, enriched in α-linolenic acid and linoleic acid metabolism pathways. In the liver, OEO similarly elevated levels of fatty acyl and glycerophospholipid metabolites. liver transcriptome profiling identified 12 differentially expressed genes related to lipid metabolism. Importantly, correlation analyses demonstrated significant relationships among intramuscular fatty acids, rumen bacteria, differential metabolites, and lipid-related genes.
Conclusion
Our findings indicate that dietary OEO modulates the rumen microbiota—particularly by enriching Prevotella—and drives changes in lipid metabolites that likely regulate host liver lipid metabolism. These shifts contribute to improved intramuscular unsaturated fatty acid content. This study provides systematic insights into the microbiome–host interaction underlying OEO-induced enhancements of beef fatty acid profiles.