# Genome-centric investigation of bile acid metabolizing microbiota of dairy cows and associated diet-induced functional implications

## TL;DR

This study explores how gut microbes in dairy cows process bile acids and how diet affects these processes, offering insights for improving cow health.

## Contribution

The first genome-centric analysis of bile acid metabolism in dairy cows using metagenomics and metabolomics.

## Key findings

- 372 high-quality MAGs were identified involved in bile acid metabolism in dairy cow intestines.
- BSH homologs were grouped into 12 clusters with distinct evolutionary and ecological traits.
- Firmicutes bacterium CAG-110 was linked to changes in bile acid levels and intestinal inflammation after dietary shifts.

## Abstract

Although the importance of bile acid (BA)-related microbial strains and enzymes is increasingly recognized for monogastric animals, a lack of knowledge about BA metabolism in dairy cows limits functional applications aimed at the targeted modulation of microbe–host interactions for animal production and health. In the present study, 108 content samples from six intestinal regions of dairy cows were used for shotgun metagenomic sequencing. Overall, 372 high-quality metagenome-assembled genomes (MAGs) were involved in BA deconjugation, oxidation, and dehydroxylation pathways. Furthermore, the BA-metabolizing microbiome predominately occurred in the large intestine, resulting in the accumulation of secondary unconjugated BAs. Comparative genomic analysis revealed that the bile salt hydrolase (BSH)-carrying microbial populations managed with the selective environment of the dairy cow intestine by adopting numerous host mucin glycan-degrading abilities. A sequence similarity network analysis classified 439 BSH homologs into 12 clusters and identified different clusters with diverse evolution, taxonomy, signal peptides, and ecological niches. Our omics data further revealed that the strains of Firmicutes bacterium CAG-110 processed the increased abundance of BSHs from Cluster 1, coinciding with the changes in the colon cholic acid concentration after grain introduction, and were intricately related to intestinal inflammation. This study is the first to use a genome-centric approach and whole intestine-targeted metabolomics to reveal microbial BA metabolism and its diet-induced functional implications in dairy cows. These findings provide insight into the manipulation of intestinal microorganisms for improving host health.