title: Influence of the amount of dietary fiber on the available energy from hindgut fermentation in growing pigs: use of cannulated pigs and in vitro fermentation.
abstract: Available energy from hindgut fermentation to pigs fed various amounts of dietary fiber was investigated using an in vivo-in vitro methodology. Six growing pigs fitted with a simple T-shaped cannula at the terminal ileum, and following a Latin-square design, were fed 3 diets differing in the content of non-starch polysaccharides (NSP): a low fiber diet (LFD, 77 g/kg of DM), a standard fiber diet (SFD, 160 g/kg of DM), and a high fiber diet (HFD, 240 g/kg of DM). After adaptation to the diet for 10 d, samples from feces and ileum were collected and analyzed for DM, energy, NSP, and chromic oxide; feces were also analyzed for short chain fatty acids (SCFA). Freeze-dried ileal samples (10 g/L) were fermented in vitro in a fecal slurry consisting of an anaerobic mineral salt medium and feces (50 g/L) from cannulated pigs fed the same diets. Available energy was calculated from the amount of SCFA produced in vitro after 48 h of incubation. Nonstarch polysaccharide content in the fermented material was measured to assess the in vitro degradation of this fraction. Increasing dietary NSP from 77 to 240 g/kg of feed DM increased (P < 0.001) ileal flow from 199 to 468 g/kg of feed, leading to a reduction in the energy digested at the terminal ileum, from 15 to 11 MJ/kg of feed DM and an increment in energy digested in the hindgut, from 1.6 to 3.5 MJ/kg of feed DM. Total in vitro production of SCFA/kg of feed DM was dependent on the amount of ileal substrate available for fermentation; that is, increased concentrations of NSP in the diet led to an increase in the SCFA that may be available to the animal (P < 0.001). The molar ratio of SCFA produced in vitro was affected by diet; the high fiber diet showed the greatest (P = 0.004) proportion of acetic acid, and the low fiber diet showed a tendency (P = 0.081) to an increased butyric acid proportion compared with the other 2 diets. Net disappearance of NSP during fermentation in vivo and in vitro were compared and showed a close relationship (P < 0.001, slope = 0.906, r = 0.960). In our experimental conditions, available energy as SCFA to the animal from hindgut fermentation increased with the concentration of dietary NSP (P < 0.001) and provided between 7.1 and 17.6% of the total available energy.
authors.affiliation: Department of Animal and Food Science, Facultat de Veterinària, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain. montserrat.anguita@uab.es
authors.forename: M
authors.initials: M
authors.lastname: Anguita
authors.forename: N
authors.initials: N
authors.lastname: Canibe
authors.forename: J F
authors.initials: JF
authors.lastname: Pérez
authors.forename: B B
authors.initials: BB
authors.lastname: Jensen
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002404:Catheterization / Q000662:veterinary; D015169:Colony Count, Microbial / Q000662:veterinary; D004032:Diet / Q000662:veterinary; D004043:Dietary Fiber / Q000008:administration & dosage* / Q000378:metabolism*; D005232:Fatty Acids, Volatile / Q000096:biosynthesis; D005243:Feces / Q000737:chemistry / Q000382:microbiology; D005285:Fermentation / Q000187:drug effects / Q000502:physiology*; D005766:Gastrointestinal Contents / Q000737:chemistry / Q000187:drug effects / Q000382:microbiology; D008297:Male; D008954:Models, Biological; D011134:Polysaccharides / Q000032:analysis / Q000378:metabolism; D013552:Swine / Q000378:metabolism*
chemical_list: D004043:Dietary Fiber; D005232:Fatty Acids, Volatile; D011134:Polysaccharides