Effects of dietary supplementation with lysine-yielding Bacillus subtilis on gut morphology, cecal microflora, and intestinal immune response of Linwu ducks1

The effects of dietary supplementation with lysine-yielding Bacillus subtilis on gut morphology, cecal microflora, and expression of intestinal cytokine mRNA of Linwu ducks (a Chinese local domesticated duck) were investigated after a 63-d feeding trial. Two hundred forty 1-d-old female ducklings were randomly assigned to 1 of 4 dietary treatments, and there were 60 birds per treatment replicated 6 times with 10 birds each. The experimental diets consisted of a basal diet containing no antibiotic or growth promoters, the basal diet supplemented with 150 mg Aureomycin per kg feed, and 2 others supplemented with 5.0 × 108 and 5.0 × 1010 cfu B. subtilis/kg feed, respectively. Birds fed the diets supplemented with B. subtilis had increased (P < 0.001) villi height in the jejunum and ileum and reduced (P < 0.001) crypt depth in the jejunum compared with birds fed the control diet. Greatest (P < 0.01) villus height:crypt depth ratio was obtained with the jejunum and ileum of birds fed the diet supplemented with 5.0 × 1010 cfu B. subtilis/kg feed. Dietary supplementation with B. subtilis resulted in increased (P < 0.05) cecal counts of Megasphaera elsdenii. Greater cecal Lactobacillus counts were obtained in ducks fed the diets supplemented with Aureomycin and B. subtilis. Ducks fed the diets supplemented with B. subtilis showed suppressed (P < 0.001) expression of interleukin (IL)-1β, IL-2, and IL-10 in their jejunum. When compared with the control, the expression of interferon (IFN)-γ in the jejunum of ducks fed the diet supplemented with 5.0 × 108 cfu B. subtilis/kg feed was significantly increased (P < 0.05). Dietary supplementation with B. subtilis or Aureomycin reduced (P < 0.001) ileal expression of IL-10. When compared with the control, the expression of IL-2 and IL-8 in the ileum of ducks fed the diet supplemented with 5.0 × 1010 cfu B. subtilis/kg feed showed a significant decrease (P < 0.05). In conclusion, dietary supplementation with lysine-yielding B. subtilis improved gut morphology, increased the population of beneficial gut microflora, and stimulated increased intestinal immune response of Linwu ducks.