Intestinal Microbiome-Metabolome Responses to Essential Oils in Piglets

Abstract

This study investigated the effects of dietary essential oils (EOs) on intestinal microbial composition and metabolic profiles in weaned piglets. The piglets were fed the same basal diet supplemented with EOs (EO) or without EOs (Con) in the current study. The results showed that the body weight gain was significantly increased, while the diarrhea incidence was significantly reduced in the EO group. In addition, EOs could modify the intestinal microbial composition of weaned piglets. The relative abundances of some beneficial bacterial species such as Bacilli, Lactobacillales, Streptococcaceae, and Veillonellaceae were significantly increased in the EO group. Metabolomics analysis indicated that protein biosynthesis, amino acid metabolism, and lipid metabolism were enriched in the EO group. And correlation analysis demonstrated that some gut bacterial genera were highly correlated with altered gut microbiota-related metabolites. Taken together, this study indicated that dietary EOs not only altered microbial composition and function but modulated the microbial metabolic profiles in the colon, which might help us understand EOs' beneficial effects on intestinal health of weaned piglets.

Keywords: colon; essential oils; metabolic profiles; microbiota; weaned piglets.

FIGURE 1

Differences in bacterial community diversity, richness, and structures in the colon of weaned piglets fed with or without dietary EO. (A) Community diversity and richness between Con and EO group. (B) Principal components analysis (PCA) of bacterial community structure between Con and EO group. Each symbol represented each gut microbiota. Green symbols represented Con group and brown symbols represented EO group. Con: the basal diet; EO: the basal diet supplemented with essential oils.

FIGURE 2

Changes of microbial composition in the colon of weaned piglets fed with or without dietary EO. Microbial composition at the phylum level (A) and genus level (B) each bar represented the average relative abundance of each bacterial taxon within a group. (C) Cladogram and LDA value distribution histogram. Bacterial taxa significantly differentiated between Con and EO group identified by linear discriminant analysis coupled with effect size (LEfSe) using the default parameters. (D) Difference of the relative abundances of Lactobacillus, Enterobacteriaceae, Ruminococcus, Butyrivibrio, and Megasphaera between Con and EO group. Con: the basal diet; EO: the basal diet supplemented with essential oils.

FIGURE 3

Microbial function prediction in the colon of weaned piglets fed with or without dietary EO. The second level (A) and third level (B) of KEGG pathway were showed in the extended error bar. The P -values were shown at right. Con: the basal diet; EO: the basal diet supplemented with essential oils.

FIGURE 4

3D-PCA score map, OPLS-DA score plots, and hierarchical clustering heat map derived from the GC-TOF/MS metabolic profiles in the colon of weaned piglets fed with or without dietary EO. (A) 3D-PCA score map showed the distribution of origin data. (B) OPLS-DA score plots showed significantly separated clusters between EO and Con group. Black represented Con group and red represented EO group. (C) Hierarchical clustering heat map constructed using molecular features with 1-fold changes (P < 0.05) showed a consistent clustering pattern within individual groups. Con: the basal diet; EO: the basal diet supplemented with essential oils.

FIGURE 5

Significantly differential metabolites in the colon of weaned piglets fed with or without dietary EO. Metabolites accountable for class discrimination with VIP > 1 and P < 0.05 were listed. Con: the basal diet; EO: the basal diet supplemented with essential oils.

FIGURE 6

Metabolic pathway enrichment analysis. Overview of metabolites that were enriched in the colon of weaned piglets fed with or without dietary EO. Con: the basal diet; EO: the basal diet supplemented with essential oils.

FIGURE 7

Correlation between microbiota and metabolites in the colon of weaned piglets fed with or without dietary EO. The color was according to the Spearman correlation coefficient distribution. Red represented significant positive correlation (P < 0.05), blue represented significantly negative correlation (P < 0.05), and white represented that the correlation was not significant (P > 0.05). Con: the basal diet; EO: the basal diet supplemented with essential oils.