Effect of Dietary Supplementation of Enteric Avian-Origin Lactobacillus casei-Fermented Soybean Meal on the Growth Performance and Intestinal Health of Broiler Chickens

The bacterial strain is key to fermentation, and the intestinal tract in livestock and poultry is a resource bank of good natural strains. The objective of this study was to evaluate the effect of soybean meal fermented using Lactobacillus casei, isolated from healthy broiler intestines with excellent organic acid production, on the intestinal health and growth performance of broilers. A total of 120 Arbor Acre male broiler chickens aged 21 days were fed until 42 days of age. These chickens were randomly divided into four groups with five replicates per group. Each replicate contained six broiler chickens. The specific groups were the control group (basal diet), the low-dose fermented soybean meal (FSBM) additive group (FSBML, basal diet + 0.2 kg/t FSBM), the middle-dose FSBM additive group (FSBMM, basal diet + 2 kg/t FSBM), and the high-dose FSBM additive group (FSBMH, basal diet + 5 kg/t FSBM). The results demonstrated a significant increase in the average daily feed intake (ADFI) and average daily gain (ADG) of the FSBMH group (p < 0.05). The FSBMH group displayed a significantly increased villus height (VH) to crypt depth (CD) ratio (VH/CD) for the duodenum (p < 0.05) and rectum (p < 0.05). The examination of the ileal mucosa showed that the FSBMH group (p < 0.05) had significantly higher levels of glutathione (GSH) activity, as well as higher relative mRNA expression of ZO-1, ZO-2, Occludin, IL-4, IL-6, MCP-1, TNF-α, IFN-α, IFN-β, and IFN-γ. However, the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were significantly lower in the FSBMH group (p < 0.05). The FSBMH group also showed higher levels of Nitriliruptoraceae and Ruminococcaceae. In conclusion, the addition of 5 kg/t FSBM to diets had an ameliorative effect on broiler growth performance and intestinal health.