An in vitro and in vivo approach to characterise digesta from pigs fed different forms of pea flour.

In vitro models of digestion are useful tools to explore the behaviour of dietary fibre sources in gastrointestinal conditions. In order to evaluate the validity of our digestion model, digesta obtained in vivo and in vitro were characterised and the impact of cell wall integrity on protein bioaccessibility and digestibility evaluated. Six cannulated barrows [Pietrain × (Large White × Landrace)] were included in a 2x2 Latin square design where they were fed two diets identical in chemical composition but differing in nutrient bioaccessibility. Pea was given either as flour (R1, most proteins encapsulated by intact cell walls) or reconstituted flour (R2, mixture of proteins and purified, broken cell walls). Digesta were collected at the duodenal and ileal cannulas at regular interval and after slaughtering, following ingestion of either R1 or R2. The two diets were also digested in vitro using a static gastrointestinal model. The original pea ingredients as well as the digesta collected in vivo and in vitro were characterised (i.e., particle size measurement, microscopy observations and gel electrophoresis) and then compared with each other. The degradation of the pea ingredients differed greatly between the two forms of flour, where particles filled with nutrients were recovered at the latest stage of R1 intestinal digestion as observed with the particle size distribution and the microscopy images. These results were consistent with the in vivo and in vitro digestibility analysis that showed lower protein hydrolysis for R1 than R2 (about 19% difference in protein digestion regardless of the method). Overall, great similarities were found between the digesta collected in vivo and in vitro, especially regarding the particle size measurements. To summarise, a substantial proportion of the proteins contained in R1 was retained within the pea cells following gastrointestinal digestion. These encapsulated proteins reduced the amount of amino acids and small peptides available for absorption. This mechanism will have consequences on postprandial metabolism of amino acids and bacterial population based on the delivery form of the dietary fibre.