# Effects of Grazing in a Low Deciduous Forest on Rumen Microbiota and Volatile Fatty Acid Production in Lambs

## TL;DR

Grazing in a low deciduous forest changes lamb rumen microbes, potentially improving digestion by boosting beneficial bacteria and volatile fatty acid production.

## Contribution

The study identifies specific bacterial genera linked to improved rumen function and volatile fatty acid production in lambs grazing natural vegetation.

## Key findings

- Grazing lambs showed a 23% decrease in ruminal butyrate concentration.
- Grazing increased microbial diversity and abundance of fiber-digesting bacteria in the rumen.
- Eight bacterial genera were identified as biomarkers for increased volatile fatty acid production.

## Abstract

This study investigated how grazing in a natural low deciduous forest (LDF) affects the rumen microbiome of growing lambs and how these changes relate to their digestion. Grazing led to important changes in the rumen microbial community, increasing the diversity and abundance of certain bacteria known to digest fibrous plant material. These microbial changes were associated with a ~23% reduction in butyrate levels in grazing lambs. In addition, specific bacterial functions involved in nutrient metabolism were more active in grazing lambs. Eight bacterial genera were identified as potential biomarkers of increased volatile fatty acid (VFA) production. These results suggest that allowing lambs to graze on natural vegetation may improve their digestive efficiency by enhancing beneficial microbial communities in the rumen.

The aim of the present study was to evaluate the effect of grazing the low deciduous forest (LDF) vegetation on the diversity of the rumen microbiome in growing lambs and its relationship with volatile fatty acid (VFA) profiles. After a 35-day indoor acclimatization (stabilization period), the lambs were assigned to two groups: housed (CG, n = 4) and grazing (EG, n = 4). The grazing lambs had a 14-day habituation period in the LDF (4 h/day) and a further 30 grazing days when fodder intake was observed. Ruminal samples were collected at the end of the stabilization, on day 14 post-stabilization (14DPS), and on day 44 post-stabilization (44DPS). The ruminal butyrate concentration showed a progressive decrease of approximately 23% over the time (p = 0.0130). The qualitative composition (p = 0.001) and relative proportions of bacteria (p = 0.004) in EG-44DPS exhibited a greater diversity, with 107 total genera and 19 unique, significant abundances in 13 genera with a higher presence of Bacteroidales_RF16_group, Lachnospiraceae_ND3007_group, and WCHB1-41. Moreover, significant functional profiles are associated with key metabolic pathways in bacteria and are interconnected by the need to generate energy and biosynthetic precursors and to manage available nitrogen and carbon. Finally, eight bacterial genera were identified as biomarkers correlated with the increase in VFA in EG-44DPS.