Effect of adding sugar beet fibre and wheat bran to a starch diet on the absorption kinetics of glucose, amino-nitrogen and volatile fatty acids in the pig.

The purpose of this study with the pig was to analyse the influence of the type of dietary fibre on quantitative kinetics of the absorption of nutrients deriving from enzymatic digestion in the small intestine and that of volatile fatty acids (VFA) deriving from microbial digestion in the hindgut influenced by the length of adaptation to the diet. Two groups of four pigs were fitted with a device for measuring absorption by simultaneous analysis of the differences in the porto-arterial concentrations of nutrients and metabolites and of the portal blood flow rate. They received successively two diets containing fish- and heat-treated potato flour, balanced in vitamins and minerals, and only differing in the type of fibre added at the inclusion level of 10%: wheat bran (S) or sugar beet fibre (P). Following an adaptation period of 30 d (C) or 5 d (A) to each of these diets, and after the last experimental meal of 800 g, the animals were subjected for 12 h to blood samplings every 30-60 min for the analysis of glucose, amino-nitrogen and volatile fatty acids (VFA) with a simultaneous recording of the portal blood flow-rate. The type of dietary fibre did not modify nutrient absorption (glucose and amino-nitrogen) but affected the amounts of VFA appearing in the portal blood. These amounts were higher (P < 0.001) after ingestion of the sugar beet fibre-rich diet (group PC + PA: 766 mmol/12 h) than after that of the wheat bran-rich diet (group SC + SA: 477 mmol/12 h). The proportion of acetic acid in the absorbed mixture rose (PC + PA 63.6% versus SC + SA 58.5%, P < 0.01) at the expense of propionic acid (PC + PA 27.4% versus SC + SA 31.0%, P < 0.01). Prolongation of the adaptation period from 5 to 30 d led to a decrease in the absorption of nutrients deriving from enzymatic digestion in the small intestine (glucose g/12 h: SA + PA 341.8 versus SC + PC 244.5, P < 0.01; amino-nitrogen g/12 h: SA + PA 29.4 versus SC + PC 21.0, P < 0.001) without any subsequent change in the absorption of the volatile fatty acids.