Similar In Vitro Ileal Fermentation Outcomes Validate the Use of a Pig Ileal Inoculum in an In Vitro Fermentation Assay for the Adult Human.

BACKGROUND

An in vivo/in vitro ileal fermentation assay using growing pigs has shown important fermentability and organic acid production. This assay could be used to study human foods but needs validation.

OBJECTIVES

To validate using a pig inoculum for studying human ileal fermentation by comparing the in vitro fermentation of fibre substrates using ileal inocula prepared from growing pigs or human ileostomates.

METHODS

Ten pigs (19 ± 4.5 kg bodyweight, mean ± standard deviation) received a diet containing human foods. After 2 wk, ileal digesta were collected 5 h postmeal. Five recruited human ileostomates incorporated the same human foods into their diet for a week before consuming 2 meals similar to the pigs' diet. Ileal effluents were then collected from 2 to 6 h postmeal. The porcine ileal digesta and human ileal effluents were used for microbial analysis and in vitro fermentation of arabinogalactan, fructooligosaccharides, and pectin.

RESULTS

The in vitro organic matter fermentability of arabinogalactan, fructooligosaccharides, and pectin was similar (P > 0.05) between the pig and human ileal inocula (34 ± 2.13% on mean). Regardless of substrates, the propionic and lactic acid production was similar between humans and pigs (P > 0.05). Ninety percent of the ileal bacterial genera were found in similar (P > 0.05) numbers in pigs and human ileostomates, which accords with the similar (P > 0.05) Shannon diversity index and predicted metabolic activity. However, some of the most abundant genera were different between species, such as Granulicatella which had 83-fold greater (P ≤ 0.05) numbers in human ileostomates, and Lactobacillus had 272-fold greater (P ≤ 0.05) numbers in pigs.

CONCLUSIONS

The in vitro ileal fermentation patterns were similar across species despite some ileal microbial compositional differences, suggesting that the growing pig could be used as a model to provide an ileal inoculum for studying ileal fermentation in adult humans. This trial was registered at the Australian New Zealand Clinical Trials registry as ACTRN12622000813785.