AUTHOR=Han Yunsheng , Xu Xin , Wang Jiaxin , Cai Hongying , Li Daojie , Zhang Hongwei , Yang Peilong , Meng Kun 

TITLE=Dietary Bacillus licheniformis shapes the foregut microbiota, improving nutrient digestibility and intestinal health in broiler chickens

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1113072

DOI=10.3389/fmicb.2023.1113072

ISSN=1664-302X

ABSTRACT=<p><italic>Bacillus licheniformis</italic> is considered a potential alternative to antibiotic growth promoters of animal growth and health. However, the effects of <italic>Bacillus licheniformis</italic> on the foregut and hindgut microbiota, and their relationships with nutrient digestion and health, in broiler chickens remain unclear. In this study, we aimed to identify the effects of <italic>Bacillus licheniformis</italic> BCG on intestinal digestion and absorption, tight junctions, inflammation, and the fore- and hind-gut microbiota. We randomly assigned 240 1-day-old male AA broilers into three treatment groups: CT (basal diet), BCG1 (basal diet + 1.0 × 10<sup>8</sup> CFU/kg <italic>B. licheniformis</italic> BCG), and BCG2 (basal diet + 1.0 × 10<sup>9</sup> CFU/kg <italic>B. licheniformis</italic> BCG). On day 42, the jejunal and ileal chyme and mucosa were subjected to analysis of digestive enzyme activity, nutrient transporters, tight junctions, and signaling molecules associated with inflammation. The ileal and cecal chyme were subjected to microbiota analysis. Compared with the CT group, the <italic>B. licheniformis</italic> BCG group showed significantly greater jejunal and ileal α-amylase, maltase, and sucrase activity; moreover, the α-amylase activity in the BCG2 group was higher than that in the BCG1 group (<italic>P</italic> &lt; 0.05). The transcript abundance of FABP-1 and FATP-1 in the BCG2 group was significantly greater than that in the CT and BCG1 groups, and the GLUT-2 and LAT-1 relative mRNA levels were greater in the BCG2 group than the CT group (<italic>P</italic> &lt; 0.05). Dietary <italic>B. licheniformis</italic> BCG resulted in significantly higher ileal occludin, and lower IL-8 and TLR-4 mRNA levels than observed in the CT group (<italic>P</italic> &lt; 0.05). <italic>B. licheniformis</italic> BCG supplementation significantly decreased bacterial community richness and diversity in the ileum (<italic>P</italic> &lt; 0.05). Dietary <italic>B. licheniformis</italic> BCG shaped the ileac microbiota by increasing the prevalence of <italic>f_Sphingomonadaceae, Sphingomonas</italic>, and <italic>Limosilactobacillus</italic>, and contributed to nutrient digestion and absorption; moreover, it enhanced the intestinal barrier by increasing the prevalence of <italic>f_Lactobacillaceae, Lactobacillus</italic>, and <italic>Limosilactobacillus</italic>. Dietary <italic>B. licheniformis</italic> BCG decreased microbial community diversity by diminishing <italic>Desulfovibrio, Alistipes, Campylobacter, Vibrio, Streptococcus</italic>, and <italic>Escherichia coli</italic>-Shigella levels, and down-regulating inflammatory associated molecule expression. Therefore, dietary <italic>B. licheniformis</italic> BCG contributed to digestion and absorption of nutrients, enhanced the intestinal physical barrier, and decreased intestinal inflammation in broilers by decreasing microbial diversity and optimizing the microbiota structure.</p>