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

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 (FSBMB+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 (FSBMB) has the highest soluble peptides, while commercial lactic acid bacteria (FSBML) 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% FSBMB+L, FSBMB, or FSBML. 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 FSBMB group had the highest reducing crypt depth; however, the FSBMB+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 FSBML and FSBMB+L (p < 0.05). Furthermore, the level of NF-κB and IL-6 mRNAs in FSBML increased, respectively, by 4 and 2.5 times. While FSBMB, along with FSBMB+L, had a 1.5-fold increase in the mRNA of IL-10, that of NF-κB increased 2-fold. FSBMB+L and FSBMB singly led to a 2- and 3-fold increase in IL-6 mRNA, respectively (p < 0.05). FSBMB and FSBMB+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.