In vitro effects of inulin and soya bean oligosaccharide on skatole production and the intestinal microbiota in broilers

The experiment was conducted to investigate the in vitro effects of inulin and soya bean oligosaccharide (SBO) on the metabolism of L‐tryptophan (L‐try) to skatole production, and the intestinal microbiota in broilers. Treatments were as follows: caecal microbiota control (Cc), Cc + inulin, Cc + SBO, rectal microbiota control (Rc), Rc + inulin and Rc + SBO. Microbial suspensions were anaerobically incubated at 38°C for 24 hr. The results showed that concentrations of skatole and acetic acid were significantly lower in caecal microbiota fermentation broth (MFB) than those in rectal MFB (p < .05). Addition of inulin or SBO significantly decreased the concentrations of indole and skatole and rate of L‐try degradation (p < .05). Inulin groups had lower indole than SBO groups (p < .05). PCR‐DGGE analysis revealed that addition of inulin or SBO decreased the microbiota richness (p < .05), but no significant differences in Shannon index (p > .05). Four distinct bands were detected in inulin and SBO groups, which were related to two of Bacteroides, one of Firmicutes and Bifidobacteria. Six bands were detected only in control groups, which represented uncultured Rikenellaceae, Roseburia, Escherichia/Shigella dysenteriae, Bacteroides uniformis (T), Parabacteroides distasonis and Enterobacter aerogenes. Populations of Lactobacilli, Bifidobacteria and total bacteria in inulin groups were higher than those in control groups (p < .05). For SBO groups, only population of total bacteria increased (p < .05). However, there were no significant differences in Escherichia coli population among treatments (p > .05). These results suggest that reduced concentrations of skatole and indole in the presence of inulin and SBO may be caused by decrease in L‐try degradation rate, which were caused by change in microbial ecosystem and pH value. Uncultured B. uniformis (T) and E. aerogenes may be responsible for degradation of L‐try to skatole.