The recovery of inulin, a naturally occurring 8(2 + 1)-fructan isolated from Jerusalem artichoke (Helianthus tuberosus L.), in the small intestine of man was studied in ileostomy subjects. The ileostomists were given a low-dietary-fibre diet based on white wheat bread and virtually free of inulin, and the same diet with the addition of 10 g and 30 g inulin product respectively, and the recovery and mean transit time (MTT) of inulin were estimated by tracking inulin in ileal effluent. The recovery of inulin was approximately 87 % at both ingestion levels. MTT was 4.9 (SE 0-6) h at an intake of 10 g inulin product decreasing to 3.4 (SE 0.3) h at an intake of 30 g inulin product. A significant change in the fructose:glucose ratio of inulin from ingestion (4.1) to recovery in ileal effluent (4.5-4.7) and a lower recovery of the glucose residue than of the fructose residue of inulin indicate that the low-molecularweight inulins are more sensitive to hydrolysis than the high-molecular-weight fragments. The loss of inulio during passage through the small intestine is presumably due to hydrolysis by either acids or enzymes and to microbial degradation by the microflora permanently colonizing the distal small intestine. The concentrations of lactic acid (LA) and short-chain fatty acids (SCFA) in frequently collected ileal effluents on the control day were approximately 6 mmol/l and approximately 55 mmol/l respectively. During periods with inulin ingestion the concentration of LA increased to 18-26 mmol/l (P < 0.052), while the concentration of SCFA ran converse and decreased to 18-32 mmol/l (P < 0,023).The osmotic loads (68 and 204 mosmol/l) associated with the ingestion of inulin product caused minor malabsorption of low-molecular-weight sugars.

Polymeric carbohydrates, starch and nonstarch polysaccharides (NSP), quantitatively represent the largest portion of the diets for pigs and are, therefore, the largest energy contributor. The 2 types of polysaccharides, however, have different fates and functions in the gastrointestinal tract and lead to different metabolites upon digestion. Pancreatic and mucosal enzymes in the small intestine break down the majority of starch, whereas NSP primarily are degraded by the microflora in the large intestine. Starch degradation leads to the release of glucose, which is absorbed by an active absorption process that triggers the release of insulin from the pancreas, whereas the fermentation of NSP to short-chain fatty acids (SCFA; i.e., acetate, propionate, and butyrate) occurs at a slower and more constant rate and with SCFA being absorbed by passive diffusion. Type and amounts of polymeric carbohydrates influence growth and development through different mechanisms. First, the proportion of starch to NSP plays an important role for the content of available energy (i.e., DE, ME, and NE); available energy relative to protein is crucial for performance and carcass quality. Second, the proportion of starch to NSP will influence rate and type of metabolites (i.e., glucose vs. SCFA) deriving from carbohydrate assimilation. Third and finally, the type of starch (i.e., types A, B, and C) and soluble NSP will influence the release of insulin, the hormone that facilitates nutrient uptake by tissues, organs, and cells, and thus plays a critically essential role in protein synthesis and muscle growth, as well as lipid synthesis and adipose tissue growth. In conclusion, polymeric carbohydrates influence growth and development through events in the gut and direct and indirect effects of different metabolites deriving from carbohydrate assimilation.

No abstract

, fax +45 89 99 13 78, email KnudErik. BachKnudsen@agrsci.dk As there is a risk of developing antibiotic resistance, a number of commonly-used antimicrobial growth promoters have been banned in the EU member states. This decision has put new emphasis on using the diet to control enteric bacterial infections of pigs. Dietary carbohydrates constitute a major proportion of diets for pigs, and the carbohydrate fraction has a diverse composition, with different properties in the gastrointestinal tract, some of which are of importance to gut health. Findings from different studies indicate that dietary carbohydrate composition influences the expression of swine dysentery and infection with nematode worms after experimental challenge with Brachyspira hyodesenteriae and Oesophagostumum dentatum respectively. In both cases the type, amount and physico-chemical properties of the carbohydrates entering the large intestine played an important role in the infection, and emerging data suggest a synergism between different porcine pathogens. There is also increasing evidence that the feed structure, which relates to the type of plant material in the diet and the way it is processed, can be used to reduce Salmonella prevalence at the herd level. However, it should be stressed that using the diet to manage gut health is not straightforward, since the expression of a pathogen in many cases requires the presence of other components of the commensal biota.

The objective was to study the cause of variation in digestibility of mixed linked β(1-3;1-4)-D-glucan (β-glucan) in the small intestine of growing pigs. The β-glucan is an important cell wall [dietary fiber (DF)] component of the endosperm of barley (Hordeum vulgare) and oats (Avena sativa). The digestibility of β-glucan in the small intestine from both cereals is among the highest of all DF components, but in 1 study with oat-based diets it was lower (P < 0.001) than in other studies. In this study, whey protein containing lactose was used as protein supplement. Lactose is slowly digestible in the small intestine. To investigate if lactose might cause the lower digestibility of β-glucan in the study with whey protein, the lactose in diets was analyzed together with lactose and organic acids (lactic acids and short-chain fatty acids) in digesta samples from the small intestine (the small intestine was by length divided in 3 equal segments: SI(1), SI(2), and SI(3)) and ileal digesta. Diets containing lactose were based on oat goats, oat flour, and oat bran (12 to 38 g lactose/kg DM) whereas the reference diets were based on rolled oats, rolled oats and oat bran, wheat (Triticum aestivum) flour with added oat bran, and wheat flour with added β-glucan (0 to 1 g lactose/kg DM). Lactose was identified in digesta up to SI(2) but disappeared in digesta from SI(3) and ileum. Digestibility of β-glucan did not differ among diets up to SI(3) (18% average) whereas digestibility in ileum was 64% in diets without lactose and 27% in diets containing lactose (P < 0.001). The β-glucan was virtually completely digested in the cecum (96% average) in all diets. The concentration of organic acids did not differ between diets either in SI(3), ileum, or cecum. In conclusion, slowly digestible lactose was the most likely cause of the reduced digestibility of β-glucan in oat diets containing lactose.