Evaluation of soluble corn fiber on chemical composition and nitrogen-corrected true metabolizable energy and its effects on in vitro fermentation and in vivo responses in dogs.

Dietary fermentable fiber is known to benefit intestinal health of companion animals. Soluble corn fiber (SCF) was evaluated for its chemical composition, nitrogen-corrected true ME (TMEn) content, in vitro digestion and fermentation characteristics, and in vivo effects on nutrient digestibility, fecal fermentation end products, and modulation of the fecal microbiome of dogs. Soluble corn fiber contained 78% total dietary fiber, all present as soluble dietary fiber; 56% was low molecular weight soluble fiber (did not precipitate in 95% ethanol). The SCF also contained 26% starch and 8% resistant starch and had a TMEn value of 2.6 kcal/g. Soluble corn fiber was first subjected to in vitro hydrolytic-enzymatic digestion to determine extent of digestibility and then fermented using dog fecal inoculum, with fermentative outcomes measured at 0, 3, 6, 9, and 12 h. Hydrolytic-enzymatic digestion of SCF was only 7%. In vitro fermentation showed increased (P < 0.05) concentrations of short-chain fatty acids through 12 h, with acetate, propionate, and butyrate reaching peak concentrations of 1,803, 926, and 112 µmol/g DM, respectively. Fermentability of SCF was higher (P < 0.05) than for cellulose but lower (P < 0.05) than for pectin. In the in vivo experiment, 10 female dogs (6.4 ± 0.2 yr and 22 ± 2.1 kg) received 5 diets with graded concentrations of SCF (0, 0.5, 0.75, 1.0, or 1.25% [as-is basis]) replacing cellulose in a replicated 5 × 5 Latin square design. Dogs were first acclimated to the experimental diets for 10 d followed by 4 d of total fecal collection. Fresh fecal samples were collected to measure fecal pH and fermentation end products and permit a microbiome analysis. For microbiome analysis, extraction of DNA was followed by amplification of the V4 to V6 variable region of the 16S rRNA gene using barcoded primers. Sequences were classified into taxonomic levels using a nucleotide basic local alignment search tool (BLASTn) against a curated GreenGenes database. Few changes in nutrient digestibility or fecal fermentation end products or stool consistency were observed, and no appreciable modulation of the fecal microbiome occurred. In conclusion, SCF was fermentable in vitro, but higher dietary concentrations may be necessary to elicit potential in vivo responses.

Potato fiber as a dietary fiber source in dog foods.

Potato fiber (PF), a coproduct of potato starch manufacture, was evaluated as a potential novel fiber source in dog food. Potato fiber contained 55% total dietary fiber, 29% starch, 4% crude protein, and 2% acid-hydrolyzed fat. The PF substrate was evaluated for chemical composition, in vitro digestion and fermentation characteristics, and in vivo responses. For the in vitro hydrolytic-enzymatic digestion and fermentation experiment, raw and cooked PF substrates were first subjected to hydrolytic-enzymatic digestion to determine OM disappearance and then fermented using dog fecal inoculum. Fermentation characteristics were then measured at 0, 3, 6, 9, and 12 h. For the in vivo experiment, 10 female mixed-breed dogs (6.13±0.17 yr; 22±2.1 kg) were provided 5 diets with graded concentrations (0%, 1.5%, 3%, 4.5%, or 6%) of PF in a replicated 5×5 Latin square design. Dogs were acclimated to the test diet for 10 d, followed by 4 d of total fecal collection. Fresh fecal samples were collected to measure fecal pH and fermentation end products. In vitro digestion revealed that raw and cooked PF were 32.3% and 27.9% digested enzymatically, whereas in vitro fermentation showed that PF was fermentable through 9 h. Raw PF had greater (P<0.05) acetate, propionate, and total short-chain fatty acid (SCFA) concentrations at the 12-h time point compared with cooked PF. The in vivo experiment showed no differences in apparent total tract DM, OM, CP, acid-hydrolyzed fat, or energy digestibility of diets containing graded concentrations of PF. However, total dietary fiber digestibility exhibited a linear increase (P<0.01) with increasing PF concentrations in the diet. Overall, linear increases (P<0.01) were observed for all individual and total SCFA, with a concomitant linear decrease (P<0.01) in fecal pH with increasing dietary PF. Fecal protein catabolite concentrations were low or undetectable, with the exception of spermidine, which exhibited a linear increase with increasing concentrations of PF. These findings indicated that inclusion of PF elicited favorable fermentation characteristics without negatively affecting nutrient digestibility or stool characteristics, indicating that PF could be a functional dietary fiber source in dog foods.

Energy value of a low-digestible carbohydrate, NUTRIOSE FB, and its impact on magnesium, calcium and zinc apparent absorption and retention in healthy young men.

BACKGROUND: Long-term consumption of imbalanced diets, poor in dietary fibres, resulted in the prevalence of several nutritional pathologies. However, low digestible carbohydrates (LDC) have many beneficial effects, especially on energy intake, digestive physiology, and mineral absorption. AIM OF THE STUDY: To determine the digestive effects of a LDC, called NUTRIOSE FB, its metabolisable energy (ME) value, and its effects on mineral absorption in humans. METHODS: Ten healthy young men were fed for 31 d periods a maintenance diet supplemented with either dextrose or the LDC at a level of 100 g DM/d, in six equal doses per d according to a cross-over design. After a 20 d adaptation period, food intake was determined for 11 days using the duplicate meal method, and faeces and urine were collected for 10 d for further analyses. RESULTS: Ingestion of the LDC did not cause severe digestive disorders, except excessive gas emission, and flatulence and slight abdominal pain in some subjects for intakes above 50 g DM/d. Wet and dry stool outputs increased by 45 and 70%, respectively (P<0.02). In vitro enzymatic digestibility of the LDC was 15 (SD 1.5) %, and 9.2 (SD 8.3) % of the LDC was excreted in faeces (P<0.001). The ME value of the LDC was 14.1 (SD 2.3) kJ/g DM, that is 14 % less than the tabulated values of sucrose and starch. Its net energy value (NEV), estimated using three prediction equations, was 8.7, 8.9, and 11.4 kJ/g DM. Ingestion of the LDC significantly increased the relative apparent absorption of Mg, and Mg retention by 67% and 31 mg/d, respectively, tended to increase Ca apparent absorption (P=0.110) and Ca retention (P=0.059), but did not significantly alter Zn parameters. CONCLUSION: NUTRIOSE FB can be used as a "bulking" agent, and substituted up to 50 g/d for usual maltodextrins without causing digestive disorders in healthy subjects. It would reduce intestinal transit disorders and energy intake, and improve magnesium and calcium absorption and retention.