Influence of dietary supplementation of herb extracts on volatile sulfur production in pig large intestine.

Volatile sulfur compounds (VS) are generated in the large intestine by the bacterial metabolism of sulfate and sulfur amino acids. VS are potentially harmful to the host. The effect of dietary supplementation of herb extracts on volatile sulfur production in the large intestine of pig was evaluated in this study. The extracts Perilla frutescens (Soyou), Mentha piperita (Peppermint), and Ajuga decumbens (Kiransou) were fed to pigs equipped with a permanent cannula at the cecum. Cecal digesta were sampled and analyzed for ammonia and short-chain fatty acids (SCFA). Sampled digesta were incubated anaerobically either with or without L-methionine for 24 h to estimate volatile sulfur production in vivo. L-Methionine was supplemented to enhance methanethiol (MeSH) production. At the end of the incubation, head space concentrations of volatile sulfur compounds such as hydrogen sulfide (H2S), MeSH, and dimethyl sulfide (DMS) were determined by flame-photometric gaschromatography after the addition of 6 N HCl. Sampled digesta were also subjected to the most probable number estimations for sulfate-reducing bacteria (SRB), sulfide producer from L-methionine, and MeSH producers from L-methionine. All three herb extracts significantly decreased H2S (p<0.05), MeSH (p<0.05), and ammonia (p<0.05) production, but SCFA production was not affected (p>0.05). The number of volatile sulfur-producing bacteria did not vary among groups by the dietary supplementation of these herb extracts. Serial solvent extraction was done on these herb extracts to specify the active fractions that reduce volatile sulfur production. n-Butanol fraction of all three extracts significantly reduced volatile sulfur production in vitro.