Relation between in vitro microbial fermentations and in vivo performance in pigs selected for their residual feed intake

TL;DR

This study links specific gut microbiota metabolic pathways and fermentation profiles to feed efficiency in pigs, revealing differences between high and low residual feed intake animals and suggesting microbiota influence on fat metabolism.

Contribution

It uncovers the association between microbiota fermentation pathways and feed efficiency, highlighting microbial contributions to fat metabolism in pigs with different residual feed intake levels.

Findings

LRFI pigs produce more acetate and propionate from insoluble dietary fibre.

Propionate production correlates with backfat thickness in LRFI pigs.

Microbial composition differs significantly between HRFI and LRFI pigs.

Abstract

Bioinformatic analysis of microbiota revealed that certain metabolic pathways are associated with low- and high- residual feed intake (HRFI and LRFI), such as the amino-acid biosynthesis pathway and the tRNA-aminoacyl synthesis pathway. The latter is associated with increased propionate production. Yet, in vitro fermentation-profile analyses revealed that LRFI pigs, from the most efficient genetic line, produced more acetate (+15%) and propionate (+56%) from the insoluble fraction (IF) containing the insoluble dietary fibre recovered after simulation of upper gastrointestinal digestion. Valerate was also more frequently abundant in LRFI pigs (P < 0.01). 16S sequencing analysis of the microbes responsible for fermentation suggested that propionate obtained from the fraction of feed that is indigestible by the host is produced mainly by Prevotella and Lactobacillus. This production was strongly correlated with backfat thickness in LRFI pigs (Spearman's correlation = 0.80), while a moderate correlation existed between butyrate production and feed efficiency in HRFI pigs (Spearman's correlation = 0.44). These results revealed that propionate production is related to fat metabolism, suggesting that GPR43 receptor activation by propionate could play a physiological role in adipose cells in RFI-pigs. These observations highlight significant functional differences between the microbiota of HRFI and LRFI pigs, as well as variability within more efficient pigs that could be exploited to improve performance.