# Higher Dietary Fibre Increases the Faecal Microbiome Diversity of Golden Lion Tamarins (Leontopithecus rosalia)

## TL;DR

Increasing dietary fiber in the diet of golden lion tamarins improves gut health by boosting microbiome diversity and promoting beneficial bacteria.

## Contribution

This study shows that higher dietary fiber leads to a healthier gut microbiome in golden lion tamarins through increased diversity and beneficial bacterial shifts.

## Key findings

- Dietary fiber increase led to a significant rise in gut microbiome diversity.
- The butyrate-producing genus Eisenbergiella emerged after the dietary change.
- The harmful bacterial group Desulfobacterota decreased significantly with higher fiber intake.

## Abstract

The bacteria living in the gut help animals extract energy from their food, synthesise nutrients, and support the proper functioning of the immune system. Gastrointestinal problems are common in Callitrichidae, making it important to understand the factors that influence their gut microbial communities. In this study, we used 16S rRNA gene sequencing to evaluate the faecal microbiome of zoo-housed golden lion tamarins (Leontopithecus rosalia). We observed significant compositional changes in the microbiota following an increase in dietary fibre. Notably, a beneficial genus of bacteria called Eisenbergiella emerged after the dietary intervention. This bacterium produces butyrate, a short-chain fatty acid that supports gut health and enhances the host ability to harvest energy from food. Following an increase in dietary fibre, the abundance of Desulfobacterota, a bacterial group associated with harmful inflammation, was reduced, suggesting an improvement in gut health. Additionally, the increase in dietary fibre led to a significant rise in bacterial diversity, which is generally considered a positive indicator of gut health.

Gut microbiota influences host energetics, metabolic rate, and overall health. Optimising the diet, such as by increasing dietary fibre, is a key strategy for promoting a healthy microbiome and improving host energy balance. In this study, we compared the faecal microbiome of five zoo-housed golden lion tamarins (Leontopithecus rosalia) before and after a dietary fibre increase using 16S rRNA gene sequencing. Prevotella, the most abundant genus, declined significantly (FDR-corrected p < 0.05) following the introduction of a higher-fibre diet. The dietary change also significantly altered the overall gut microbial composition, including the emergence of Eisenbergiella (FDR-adjusted p < 0.05), a butyrate-producing genus whose relative abundance increased from 0% to 0.005% (FDR-adjusted p < 0.05). Given the role of Eisenbergiella in butyrate synthesis, this shift may enhance host energy metabolism and microbial interactions. Additionally, both alpha and beta diversity increased significantly (p < 0.05) after the dietary fibre intervention. A significant reduction in Desulfobacterota (FDR-adjusted p < 0.05) following dietary fibre enrichment was observed, suggesting a shift away from microbial groups that may be associated with pathogenicity or pro-inflammatory effects. Collectively, these changes represent a positive shift in the microbiome, supporting improved host energetics and metabolic health.