Microbiota and metabolome responses in the cecum and serum of broiler chickens fed with plant essential oils or virginiamycin

Abstract

This study investigated the cecal microbiota and serum metabolite profile of chickens fed with plant essential oils (PEO) or virginiamycin (VIRG) using high-throughput 16S rRNA gene sequencing and untargeted metabolomics approach. The main aim of this work was to explore the biochemical mechanisms involved in the improved growth performance of antibiotics and their alternatives in animal production. The results showed that both PEO and VIRG treatment significantly increased the relative abundance of phyla Bacteroidetes and decreased the abundance of phyla Firmicutes and genus of Lactobacillus in cecal microbiota of chickens. Compared to the control group (CT group), the relative abundance of genus of Alistipes, unclassified Rikenellaceae, Roseburia, and Anaeroplasma was enriched in the PEO group; that of genus Bacteroides, Lachnospiraceae, and unclassified Enterobacteriaceae was enriched in the cecal microbiota of the VIRG group. Untargeted metabolomics analyses revealed that the PEO treatment modified 102 metabolites and 3 KEGG pathways (primary bile acid biosynthesis and phenylalanine metabolism) in the cecal microbiota, and 81 metabolites and relevant KEGG pathways (fructose and mannose metabolism, biosynthesis of unsaturated fatty acids, and linoleic acid.) in the serum of the chicken. Compared to the CT group, VIRG treatment group differed 217 metabolites and 10 KEGG pathways in cecal contents and 142 metabolites and 7 KEGG pathways in serum of chickens. Pearson's correlation analysis showed that phyla Bacteroidetes and genus of Bacteroides, Alistipes, and unclassified Rikenellaceae (in the VIRG and PE group) were positively correlated with many lipid metabolites. However, phyla Firmicutes and genera Lactobacillus (higher in the CT group) were negatively correlated with the lipid and thymine metabolism, and positively correlated with hydroxyisocaproic acid, cytosine, and taurine. This study shows that dietary supplementation with PEO and VIRG altered the composition and metabolism profile of the cecal microbiota, modified the serum metabolism profile.

Figure 1

Differences in bacterial community diversity, richness, and structures in the cecum of broiler chickens fed without or with PEO or VIRG. (A) Community diversity and richness among CT, PEO, and VIRG group. (B) Principal components analysis (PCA) of the bacterial community structure among CT, PEO, and VIRG group. Each symbol represents each gut microbiota. Red symbols represented CT group, blue symbols represented PEO group, and brown symbols represented VIRG group. CT: the basal diet; PEO: the basal diet supplemented with plant extracts; VIRG: the basal diet supplemented with virginiamycin. PLS-DA score plots showed significantly separated clusters between CT, PEO, and VIRG group.

Figure 2

Changes of microbial composition in the cecum of broiler chickens fed without or with PEO or VIRG. Microbial composition at the phylum level (A) and genus level (B) each bar represents the relative abundance of each bacterial taxa of chicken. Bacterial taxa significantly differentiated between CT, PEO group, and VIRG group (C) and was identified by linear discriminant analysis coupled with effect size (LEfSe) using the default parameters. CT: the basal diet; PEO: the basal diet supplemented with plant extracts; VIRG: the basal diet supplemented with virginiamycin.

Figure 3

Significantly differential metabolites in the cecum and serum of broiler chickens fed without or with PEO or VIRG. Differential metabolites on PEO vs. CT in the cecum (A), VIRG vs. CT and VIRG in the cecum (B); differential metabolites on PEO vs. CT in the serum (C), VIRG vs. CT and VIRG in the serum (D). Metabolites accountable for class discrimination with VIP > 1 and P < 0.05 were listed. CT: the basal diet; PEO: the basal diet supplemented with plant extracts; VIRG: the basal diet supplemented with virginiamycin.

Figure 4

Correlation between microbiota and metabolites in the cecum (A) and serum (B) of broiler chickens fed without or with dietary PEO or VIRG. 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). CT: the basal diet; PEO: the basal diet supplemented with plant extracts; VIRG: the basal diet supplemented with virginiamycin.

Figure 5

Gas chromatography-mass spectrometry total ion chromatogram of PEO. Peaks are representative of the mass of the compounds present in PEO: Cinnamical dehyde (RT = 33.6, Area = 78.3%), Isophorone (RT = 22.9, Area = 4.23%).