Comparison of intestinal contents from different regions of the equine gastrointestinal tract as inocula for use in an in vitro gas production technique

The aim of the experiment reported here was to compare equine faeces with inocula obtained from equine caecum, ventral colon and dorsal colon for use in the in vitro gas production technique. Freeze-dried grass (FDG), high-temperature dried grass (HDG) and unmolassed sugar beet pulp (BP) were incubated with either caecal fluid (C), dosal colonic fluid (D), ventral colonic fluid (V) or faeces (F) as the source of inoculum. Substrate/inocula combinations were fermented using an in vitro gas production (GP) technique. Mathematical analysis of cumulative gas production curves revealed an interaction (P<0.001) between inocula and substrate for all of the in vitro parameters measured. However, similar extents of gas production were seen for inocula obtained from caecal fluid and faeces across all substrates, with lower values obtained from bottles incubated with colonic fluid. Thus, results indicate that faeces are a suitable alternative to caecal fluid; however, it would appear that they are less effective in modelling fermentation in the colon. Consequently, further work is required to determine the use of faeces as an alternative to caecal and colonic fluid and to further investigate inocula/substrate interactions.