# Dietary Fiber Regulation of Gut Microbiota and Bile Acid Metabolism in Animals: Implications for Animal Nutrition

## TL;DR

This review explores how dietary fiber affects gut bacteria and bile acid metabolism in animals, highlighting differences between ruminants and non-ruminants for better livestock management.

## Contribution

The paper provides a comprehensive review of the bidirectional interactions between dietary fiber, gut microbiota, and bile acid metabolism in animals.

## Key findings

- Dietary fiber influences gut microbiota and bile acid metabolism differently in ruminant and non-ruminant animals.
- Short-chain fatty acids produced by fiber fermentation affect bile acid metabolism through microbial processes.
- Inappropriate dietary fiber supplementation can negatively impact gastrointestinal function and health.

## Abstract

Dietary fiber plays a crucial role in animal nutrition and gut health, and its digestion and metabolic pathways differ fundamentally between non-ruminant and ruminant animals. This review summarizes the interactions among dietary fiber, gut microbiota, and bile acids in both non-ruminant and ruminant animals, which vary depending on fiber type, source, and dosage. By highlighting these interactions, this review provides foundational information for livestock management, helping farmers and caretakers use dietary fiber more effectively. It also offers preliminary insights into the mechanisms of the dietary fiber–microbiota–bile acid axis, which can guide future research and improve animal health and productivity.

Dietary fiber (DF) is a fundamental component of animal nutrition and has been widely studied for its nutritional and physiological functions in animals. While existing studies mainly focus on the independent effects of DF on gut microbiota or bile acids (BAs), the mechanisms underlying their interactions remain poorly understood. DF interacts closely with gut microbiota, promoting the production of beneficial metabolites such as short-chain fatty acids, which subsequently influence BA metabolism through microbial deconjugation and dehydroxylation processes, generating free and secondary BA essential for host health. Together, the gut microbiota and BA play key roles in mediating the effects of DF on intestinal and systemic physiology via the gut–liver axis. Although DF contributes to energy supply, nutrient digestion, and regulation of gut microbiota and BA metabolism, its physiological effects vary depending on fiber source, type, chemical composition, inclusion level, and animal species. Ruminant and non-ruminant animals differ in their capacity to utilize DF, with extensive fermentation occurring in the rumen of ruminants, whereas fermentation in non-ruminants mainly occurs in the hindgut and is more limited. Consequently, inappropriate DF supplementation may impair gastrointestinal function and overall physiological status. This review summarizes the diverse effects of different DF types in animals and critically examines the complex and bidirectional interactions among DF, gut microbiota, and BA metabolism, highlighting knowledge gaps that require further investigation to optimize DF application in animal nutrition.