An in vitro method for studying digestion in the pig. 2. Comparison with in vivo ileal and faecal digestibilities

1. An in vitro method involving incubation of feed samples with buffered duodenal digesta for 12 h or with buffered ileal and faecal inocula for 48 h was compared with in vivo ileal or faecal apparent digestibilities in pigs. 2. The five diets investigated had crude protein (nitrogen x 6.25) contents from 164 to 185 g/kg, starch contents from 296 to 463 g/kg and dietary fibre contents from 176 to 347 g/kg. 3. In vitro disappearances with duodenal inocula were correlated (P less than 0.05) with in vivo ileal apparent digestibilities for crude protein, ash, starch, energy and dry matter, but not for dietary fibre. 4. In vitro disappearances with the ileal and faecal inocula were generally correlated (P less than 0.1) with in vivo faecal apparent digestibilities for dietary fibre, energy and dry matter, but not for ash or crude protein. The patterns of degradability of fibre polysaccharide residues in vitro and in vivo were also similar. 5. Results indicate that this in vitro method could be used to predict the availability of starch and crude protein for digestion in the small intestine, and the degradability of dietary fibre, and thus for comparing the nutritive value of pig feeds.