Effects of supplementation with <i>Bacillus subtilis</i> peptide on growth performance, intestinal barrier and caecal microbiota metabolism in broilers

This study assessed Bacillus subtilis (B. subtilis) peptide as broiler feed additives. A total of 240 one-day-old male broilers were assigned to four groups (six replicates of 10 broilers) for 42 days. The control group was administered a basic diet, whereas the treatment groups got the basal food augmented with B. subtilis peptide at doses of 100, 200, or 300 mg/kg (low, medium, or high dose). The growth performance, intestinal mucosal morphology, immunity, and microbiota were measured. Results confirmed that the average feed intake of broilers in low-dose B. subtilis peptide group was increased at 1 ∼ 42 days old, compared to the control group (p < 0.05). And dietary supplementation with low-dose B. subtilis demonstrated an improving trend in average daily gain and a reduction in feed-to-weight ratio of broilers during the 22 to 42–day period. All doses elevated the concentrations of acetic, propionic, butyric, valeric and 2–methylbutyric acid in the caecum (p < 0.05). In terms of intestinal health, high-dose B. subtilis peptide upregulated ileal and jejunal Claudin-1 and Occludin-1 mRNA levels. At the phylum level, low-dose treatment significantly increased Cyanobacteria abundance (p < 0.05). At the genus level of community composition, all B. subtilis peptide treatments reduced the abundance of Bacteroides in broiler caecal contents. Furthermore, high-dose B. subtilis peptide significantly decreased caecal Lactobacillus abundance (p < 0.05). In conclusion, the addition of B. subtilis peptide to the diet might help to improve and maintain the intestinal barrier while modulate the metabolism of intestinal flora.