Effects of dietary Bacillus velezensis fermented soybean hull supplementation on antioxidant capacity, suppressing pro-inflammatory, and modulating microbiota composition in broilers

Abstract

This study aimed to ferment soybean hulls (SBH) with Bacillus velezensis and evaluate their effects on broiler diets, specifically focusing on intestinal antioxidant capacity, immune modulation, and microbiota composition. The animal trial involved 400 one-day-old Arbor Acres broilers, randomly assigned to a control group (basic diet, Control) and groups receiving 5 % and 10 % unfermented soybean hulls (5 % USBH, 10 % USBH) and 5 % and 10 % fermented soybean hulls (5 % FSBH_B, 10 % FSBH_B) as replacements for the basic diet. Each group contained 80 birds, divided into four pens with 20 birds per pen, and the trial lasted for 35 days. In the jejunum, the 5 % FSBH_B group tended to suppress pro-inflammatory gene expression, while the 10 % FSBH_B group tended to enhance antioxidant gene expression. In terms of jejunum protein levels, the 10 % FSBH_B group exhibited significantly lower (P < 0.05) TNF-α protein levels compared to the control and other treatment groups. Furthermore, intestinal microbiota analysis showed that ileum and cecum microbial counts in the 10 % USBH and 10 % FSBH_B groups were higher than those in the control group. Species richness indices also revealed that both the 10 % USBH and 10 % FSBH_B groups were significantly higher (P < 0.05) than the control group. In conclusion, soybean hulls fermented with Bacillus velezensis improved intestinal antioxidant capacity, suppressed pro-inflammatory gene expression, and modulated microbiota composition in broilers, with the 10 % FSBH_B group demonstrating the most pronounced effects.

Keywords: Bacillus velezensis; Broilers; Fermented soybean hull; Intestinal microbiota.

Fig. 1

Effect of dietary substitution with different levels of fermented soybean hull on jejunum's relative mRNA expression of genes related to Nrf2 (A), SOD-1 (B), CAT (C), GSH-Px (D), and HO-1 (E) of 35d-old broilers. ^{a, b} Different letters are significantly different (P < 0.05), each value represent mean of 4 replicates. Error bars represent the SD of the mean.

Fig. 2

Effect of dietary substitution with different levels of fermented soybean hull on jejunum's relative mRNA expression of genes related to NF-κB (A), iNOS (B), and TNF-α (C) of 35d-old broilers. ^a-c Different letters are significantly different (P < 0.05), each value represent mean of 4 replicates. Error bars represent the SD of the mean.

Fig. 3

Effect of dietary substitution with different levels of fermented soybean hull on jejunum's relative mRNA expression of genes related to Muc 2 (A), ZO-1 (B), and Occludin (C) of 35d-old broilers. ^{a, b} Different letters are significantly different (P < 0.05), each value represent mean of 4 replicates. Error bars represent the SD of the mean.

Fig. 4

Effect of dietary substitution with different levels of fermented soybean hull on jejunum's relative mRNA expression of genes related to PepT-1 of 35d-old broilers. ^{a, b} Different letters are significantly different (P < 0.05), each value represent mean of 4 replicates. Error bars represent the SD of the mean.

Fig. 5

Venn diagram for microbiota of broilers in ileum (A) and cecum (B). Ctrl: basal diet; U10: partially replaced control with 10 % of unfermented soybean hull; F10: partially replaced control with 10 % of fermented soybean hull by Bacillus velezensis.

Fig. 6.1

Alpha diversity indices of the bacterial community in the ileum of broilers. (A) Shannon index, (B) Simpson index, (C) Menhinick's richness index, and (D) Margalef's richness index. Significance was assessed by Kruskal-Wallis. Ctrl: basal diet; U10: partially replaced control with 10 % of unfermented soybean hull; F10: partially replaced control with 10 % of fermented soybean hull by Bacillus velezensis.

Fig. 6.2

Alpha diversity indices of the bacterial community in the cecum of broilers. (A) Shannon index, (B) Simpson index, (C) Menhinick's richness index, and (D) Margalef's richness index. Significance was assessed by Kruskal-Wallis. Ctrl: basal diet; U10: partially replaced control with 10 % of unfermented soybean hull; F10: partially replaced control with 10 % of fermented soybean hull by Bacillus velezensis.

Fig. 7.1

Beta diversity indices of the bacterial community in the ileum of broilers. (A) PCoA analysis, and (B) PERMANOVA. Ctrl: basal diet; U10: partially replaced control with 10 % of unfermented soybean hull; F10: partially replaced control with 10 % of fermented soybean hull by Bacillus velezensis. F: measure R²: the degree to which different groupings explain the variation in the samples, defined as the ratio of group variance to total variance. The adjusted p-value being less than 0.05 indicates high reliability of this test.

Fig. 7.2

Beta diversity indices of the bacterial community in the cecum of broilers. (A) PCoA analysis, and (B) PERMANOVA. Ctrl: basal diet; U10: partially replaced control with 10 % of unfermented soybean hull; F10: partially replaced control with 10 % of fermented soybean hull by Bacillus velezensis. F: measure R²: the degree to which different groupings explain the variation in the samples, defined as the ratio of group variance to total variance. The adjusted p-value being less than 0.05 indicates high reliability of this test.

Fig. 8

100 % stacked bar chart of the top 10 with the highest relative abundance in ileum under (A) phylum, (B) class, (C) order, (D) family, (E) genus and (F) species. Ctrl: basal diet; U10: partially replaced control with 10 % of unfermented soybean hull; F10: partially replaced control with 10 % of fermented soybean hull by Bacillus velezensis.

Fig. 9

100 % stacked bar chart of the top 10 with the highest relative abundance in cecum under (A) phylum, (B) class, (C) order, (D) family, (E) genus and (F) species. Ctrl: basal diet; U10: partially replaced control with 10 % of unfermented soybean hull; F10: partially replaced control with 10 % of fermented soybean hull by Bacillus velezensis.