Assessment of Intestinal Immunity and Permeability of Broilers on Partial Replacement Diets of Two-Stage Fermented Soybean Meal by Bacillus velezensis and Lactobacillus brevis ATCC 367

SIMPLE SUMMARY: Inflammation induced by diet, environmental factors, and stimulated innate immunity is not conducive to intestinal maintenance and remodeling. Fermented soybean meal (FSBM) by Bacillus velezensis (Bv) and Lactobacillus brevis ATCC 367 (Lb) reduces these negative factors and provides bioactive active peptides that are beneficial to intestinal repair and regulate the immune system of the intestinal tract. This study showed that two-stage FSBM regulates the immunity and tight junction in the jejunum, which are beneficial to health and performance. ABSTRACT: The effect of soybean peptides from fermented soybean meal on the intestinal immunity and tight junction of broilers was assessed. Roughly, two-stage fermented soybean meal prepared with Bv and Lb (FSBM(B+L)), which has nearly three times higher soluble peptides than soybean meal (SBM), and reduced galacto-oligosaccharide (GOS) content and allergen protein. The one-stage fermented by Bv (FSBM(B)) has the highest soluble peptides, while commercial lactic acid bacteria (FSBM(L)) has the highest Lactic acid bacteria count; these were used to compare the differences in the process. Ross308 broilers (n = 320) were divided into four groups: SBM diet and a diet replaced with 6% FSBM(B+L), FSBM(B), or FSBM(L). The growth performance was recorded during the experiment, and six birds (35-day-old) per group were euthanized. Analysis of their jejunum and ileum showed that the fermented soybean meal significantly improved the villus height in the jejunum (p < 0.05) and reduced the crypt hyperplasia. The FSBM(B) group had the highest reducing crypt depth; however, the FSBM(B+L) group had the highest villus height/crypt depth in the ileum (p < 0.05). In the jejunum, the relative mRNA of CLDN-1 and Occludin increased 2-fold in the treatments, and ZO-1 mRNA increased 1.5 times in FSBM(L) and FSBM(B+L) (p < 0.05). Furthermore, the level of NF-κB and IL-6 mRNAs in FSBM(L) increased, respectively, by 4 and 2.5 times. While FSBM(B), along with FSBM(B+L), had a 1.5-fold increase in the mRNA of IL-10, that of NF-κB increased 2-fold. FSBM(B+L) and FSBM(B) singly led to a 2- and 3-fold increase in IL-6 mRNA, respectively (p < 0.05). FSBM(B) and FSBM(B+L) can also upregulate MUC2 in the jejunum (p < 0.05). In short, using the soybean peptides from two-stage fermented soybean meal can ameliorate the negative factors of SBM and effectively regulate immune expression and intestinal repair, which will help broilers maintain intestinal integrity.