Polysaccharides derived from Astragalus membranaceus and Glycyrrhiza uralensis improve growth performance of broilers by enhancing intestinal health and modulating gut microbiota

Abstract

This study was conducted to investigate the effects of dietary supplementation of polysaccharides derived from Astragalus membranaceus and Glycyrrhiza uralensis on growth performance, intestinal health, and gut microbiota composition in broilers. A total of 480 one-day-old male Arbor Acres broilers were randomly divided into 4 treatments with 6 replicates comprising 20 broilers each. Treatments included: basal diet without antibiotics (CON); basal diet supplemented with 500 mg/kg terramycin calcium (ANT); basal diet supplemented with 300 mg/kg Astragalus membranaceus polysaccharides (APS); and basal diet supplemented with 150 mg/kg Glycyrrhiza uralensis polysaccharides (GPS). The results showed that ANT, AP,S and GPS supplementation significantly increased average daily gain (ADG) and decreased feed conversion ratio (FCR) of broilers from 1 to 42 d of age. At 42 d, serum immunoglobulin A (IgA), immunoglobulin M (IgM) and immunoglobulin G (IgG) levels of the APS and GPS group were notably higher than those of the CON group, while serum levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) as well as diamine oxidase (DAO) activity in the APS and GPS group were obviously decreased. Moreover, diets supplemented with APS and GPS could significantly increase villus height (VH) and the ratio of villus height to crypt depth (VH/CD) and remarkably upregulated occludin, claudin-1 and mucin-2 (MUC2) mRNA expression in duodenum, jejunum, and ileum of broilers. In addition, 16S rRNA gene sequencing revealed that APS and GPS supplementation altered cecal microbial diversity and composition in broilers. Higher Shannon index was observed in the APS and GPS group compared with the CON group, while GPS supplementation could also increase Chao1 index and Observed species. The result of Principal coordinate analysis (PCoA) showed that microbial community in the CON, ANT, APS, and GPS group clustered separately. Notably, both APS and GPS supplementation significantly decreased the abundance of Bacteroidetes, Bacteroides, Faecalibacterium, Desulfovibrio, and Butyricicoccus, while increased the abundance of Firmicutes, Prevotella, Parabacteroides, Ruminococcus, and Alistipes. The correlation analysis showed that the changes in cecal microbial composition induced by dietary APS and GPS supplementation were closely associated with the alteration of the phenotype of broilers including ADG, FCR, TNF-α, IL-1β, IL-6, IgA, IgG, DAO, Occludin, Claudin-1, ZO-1, and MUC2. In conclusion, polysaccharides derived from Astragalus membranaceus and Glycyrrhiza uralensis could improve growth performance of broilers by enhancing intestinal health and modulating gut microbiota.

Keywords: Glycyrrhiza uralensis; astragalus membranaceus; broiler; intestine health; polysaccharides.

Figure 1

Effects of ANT, APS, and GPS on serum diamine oxidase (DAO) (A) and D-lactic acid (D-LA) (B) level in broilers. Data are means ± SEM, n = 6. Means with different letters indicate significant difference (P < 0.05). Abbreviations: ANT, basal diet supplemented with 500 mg/kg terramycin calcium; APS, basal diet supplemented with 300 mg/kg Astragalus membranaceus polysaccharides; CON, control group with basal diet; GPS, basal diet supplemented with 150 mg/kg Glycyrrhiza uralensis polysaccharides.

Figure 2

Effects of ANT, APS, and GPS on mRNA expression of occludin (A), claudin-1 (B), zonula occludens-1(ZO-1) (C), and mucin-2(MUC2)(D) in small intestine. Data are means ± SEM, n = 6. Means with different letters indicate significant difference (P < 0.05). Abbreviations: ANT, basal diet supplemented with 500 mg/kg terramycin calcium; APS, basal diet supplemented with 300 mg/kg Astragalus membranaceus polysaccharides; CON, control group with basal diet; GPS, basal diet supplemented with 150 mg/kg Glycyrrhiza uralensis polysaccharides.

Figure 3

Principal coordinate analysis (PCoA) of the cecal microbiota based on Weighted UniFrac distance (n = 4). The scatterplot of the PCoA scores shows four different clusters. Abbreviations: ANT, basal diet supplemented with 500 mg/kg terramycin calcium; APS, basal diet supplemented with 300 mg/kg Astragalus membranaceus polysaccharides; CON, control group with basal diet; GPS, basal diet supplemented with 150 mg/kg Glycyrrhiza uralensis polysaccharides.

Figure 4

Effects of ANT, APS, and GPS on microbial composition in the cecum of broilers. (A) Relative abundance of cecal microbiota at the phylum level. (B) The proportion of Firmicutes to Bacteroidetes. (C) Relative abundance of cecal microbiota at the genus level. (D) Relative abundance difference analysis of cecal bacterial species at the genus level. Abbreviations: ANT, basal diet supplemented with 500 mg/kg terramycin calcium; APS, basal diet supplemented with 300 mg/kg Astragalus membranaceus polysaccharides; CON, control group with basal diet; GPS, basal diet supplemented with 150 mg/kg Glycyrrhiza uralensis polysaccharides.

Figure 5

Linear discriminant analysis (LDA) effect size (LEfSe) analysis of cecal microbiota. LDA scores generated for the differentially abundant microbiota (LDA > 2, P < 0.05). Abbreviations: ANT, basal diet supplemented with 500 mg/kg terramycin calcium; APS, basal diet supplemented with 300 mg/kg Astragalus membranaceus polysaccharides; CON, control group with basal diet; GPS, basal diet supplemented with 150 mg/kg Glycyrrhiza uralensis polysaccharides.

Figure 6

Correlation between the differential cecal microbial community of genera and the phenotype of broilers by Spearman correlation analysis. Asterisks indicate significant correlations (* P ≤ 0.05, ** P ≤ 0.01.). Blue indicates a positive correlation, while red indicates a negative correlation. The deeper color means the greater correlation. VH, Occludin, Claudin-1, ZO-1, and MUC2 are the jejunal values. Abbreviations: ADG, average daily gain; DAO, diamine oxidase; FCR, feed conversion ratio; IL-1β, interleukin-1β; IL-6, interleukin-6; IgA, immunoglobulin A; IgM, immunoglobulin M; IgG, immunoglobulin G; MUC-2, mucin-2; VH, villus height; TNF-α, tumor necrosis factor-α; ZO-1, zonula occludens-1.