Integration of ileum cannulated pigs and in vitro fermentation to quantifythe effect of diet composition on the amount of short-chain fatty acids available from fermentation in the large intestine

Using cannulated pigs and a standardised in vitro fermentation system the e ffect of diet and non-starch polysaccharides (NSP) on the amount of energy available from microbial fermentation in the large intestine could be predi cted. The available energy was calculated from the amounts of short-chain f atty acids (SCFA) produced. Three diets were investigated: a low fibre diet based essentially on wheat flour (56 g NSP kg(-1) feed) and two high fibre diets with added oat bran (93 g NSP kg(-1) feed) or wheat bran (102 g NSP kg(-1) feed). Colonic fermentation was estimated by in vitro fermentation o f freeze-dried ileal effluent collected from cannulated pigs. The in vitro fermentation method was optimised to use 10 g ileum content litre(-1) incub ated at pH 6.0 in a fermenter containing faecal slurry consisting of anaero bic mineral salts medium and 50 g litre(-1) faeces from pigs fed the same d iets as the cannulated pigs. The results demonstrate that it is very import ant to compensate for the faecal SCFA contribution when calculating the amo unt of SCFA produced from ileal digesta during in vitro fermentation. The a mount of NSP digested in vitro was compared with data obtained from in vivo studies and there was a good agreement between in vivo and in vitro data. We concluded that the integrated in vivo-in vitro method is a valuable tech nique to estimate the effect of diet and NSP on the amount of SCFA produced in the large intestine and when fed the three diets the microbial fermenta tion in the large intestine provided between 2.4-6.4% of the total availabl e energy. (C) 1999 Society of Chemical Industry.