In vitro fermentation of structural carbohydrate-rich feeds using faecal inoculum from pigs

Seven feeds were tested in vitro using faecal inoculum from pigs. Sugar beet pulp, wheat bran, soybean hulls, grapecake, glutamic beet pulp, citrus by-product and fructo-oligo- saccharides (FOS) were fermented for 96 h. Cumulative gas production was measured as indicator of the fermentation kinetics. At the end of incubation organic matter disappearance and fermentation end-products (short-chain fatty acids and NH3) were also measured. The gas production profiles were fitted with a multi- phasic model. Significant differences were detected between grapecake and FOS: the very low gas production for the first one was probably due to the high lignin and tannins contents of this by-product, while the higher organic matter cumulative gas volume (OMCV) and organic matter disappearance (OMD) values for FOS were due to the high soluble fibre proportion. Soybean hulls and citrus by-product, showed similar values of degradability and gas production and were characterised by different fermentation profiles. Grapecake showed the lower fermentation, while citrus by-product was characterized high gas and short-chain fatty acids production. These characteristics could be particularly useful to optimize the caecum-colon fermentation in order to obtain a high butyrate acid production.