In vitro fermentation characteristics of agricultural products and coproducts and its effect on the large intestinal microbiota of swine

Abstract Text: Dietary fibers and resistant starches are fermented in the gastrointestinal tract (GIT) and alter the microbial community. Specific microbes in the GIT are found to promote host health, the microbial population is also dependent on the type of fermentation substrates available in the GIT. Alternative feedstuffs are explored and evaluated to  contribute in reducing feed costs of swine. These feedstuffs are typically rich in fiber and/or resistant starches which may provide prebiotic effects for the pigs. Six alternative feedstuffs were evaluated for their fermentation characteristics and effect on the microbiota of the large intestine of swine using an in vitro model. Three fibrous (macadamia nut cake, MNC; barley brewers grain, BBG; wheat millrun, WMR) and three starchy (Okinawan sweet potato, OSP; yam, and taro) feedstuffs along with inulin and blank as a positive and negative control, respectively were used in this study. After 2 step enzymatic digestion assay, residues were fermented using fresh pig feces as microbial inoculum and gas production were recorded periodically. The residue after 72 hours of microbial fermentation was used for genomic DNA isolation. The V3 region of the 16S rDNA of the genome was amplified using bacterial primers and the product used to generate banding profiles via temperature gradient gel electrophoresis (TGGE). The unique profile created by each sample was analyzed, and compared to determine similarities between samples. The fibrous feedstuffs (MNC, BBG and WMR) were most closely related to each other, and to inulin, indicating they may cause a health-promoting shift in the microbial community as inulin. The starchy feedstuffs (OSP, yam and taro) also showed similarities to each other, but were less related to inulin, with the exception of OSP, which had a similar profile to inulin. The MNC was least similar to the starchy feedstuffs. Total gas production of OSP (298), inulin (291) and taro (276) were significantly higher (P < 0.01) than MNC (87) and BBG (75 ml/g sample). In conclusion, some of the alternative feedstuffs tested may exert comparable prebiotic effects to inulin, thus may be included in swine diets to favorably impact the GIT microbiota.

Keywords:  coproducts, fermentation, gut microbiota