# Host genomic regulation of ileal Bradyrhizobium abundance modulates eating speed and fat metabolism in birds: a causal mechanism study

## TL;DR

This study shows how host genes and gut bacteria like Bradyrhizobium influence eating speed and fat levels in chickens, offering new ways to improve poultry health.

## Contribution

The study identifies Bradyrhizobium as a causal gut microbe linking eating behavior and fat metabolism through host genetic factors.

## Key findings

- Higher Bradyrhizobium abundance reduces abdominal fat and inflammation in chickens.
- Host genetic variants at RECK influence Bradyrhizobium abundance and eating behavior.
- A feedback loop exists where fat deposition increases eating speed, which worsens fat accumulation.

## Abstract

Eating speed is a key eating behavior trait that influences energy intake and fat deposition, yet its regulation by host genetics and gut microbiota remains poorly understood in birds.

We systematically investigated the interplay among host genetics, gut microbiota, eating speed, and fat deposition in chickens. Phenotypic analyses revealed a positive association between eating speed and abdominal fat, and Mendelian randomization (MR) analysis identified a bidirectional feedback loop in which fat deposition promotes faster eating, which in turn exacerbates fat accumulation. Microbiome and MR analyses highlighted the ileal genus Bradyrhizobium as a causal regulator of both eating speed and fat deposition, with higher abundance reducing abdominal fat, triglyceride levels, and inflammatory markers. Microbiome genome-wide association studies (mGWAS) further identified host genetic variants and candidate genes, including convergent signals at RECK, influencing Bradyrhizobium abundance. Mediation analyses indicated that Bradyrhizobium modulates eating speed partially through its effects on abdominal fat, emphasizing a host-microbe-behavior feedback axis.

Our findings reveal a complex interplay among host genetics, gut microbes, and eating behavior, providing mechanistic insights and potential targets for precision interventions to optimize growth and metabolic health in poultry.

The online version contains supplementary material available at 10.1186/s40104-026-01369-z.