Fruit and vegetable fiber fermentation by gut microflora from canines.

Abstract

The objective of this study was to assess fermentability by canine gut microflora to include shortchain fatty acid (SCFA) production, organic matter (OM) disappearance, and gas production of vegetable and fruit fiber sources compared to fiber standards (psyllium, citrus pectin, and Solka Floc). Fiber sources included apple pomace, carrot pomace, flaxseed, fruit blend (mixture of peach, almond, nectarine, and plum), grape pomace, pea hulls, pistachio, and tomato pomace. Substrates were fermented in vitro for 4, 12, and 24 h with fecal flora obtained from three healthy dogs. Citrus pectin had the highest OM disappearance, SCFA production, and gas production at all times of fermentation; psyllium was intermediate and Solka Floc was lowest. A wide variation in fermentability was noted among the vegetable and fruit fiber sources. Apple pomace, carrot pomace, and flaxseed had the greatest fermentability as assessed by OM disappearance. Pea hulls and tomato pomace had intermediate OM disappearances, and fruit blend, grape pomace, and pistachio were poorly fermented. Carrot pomace produced the largest amounts of gas and SCFA. Apple pomace produced high concentrations of gas but intermediate concentrations of SCFA. Pea hulls and tomato pomace produced intermediate concentrations of gas and SCFA, whereas flaxseed, fruit blend, grape pomace, and pistachio produced low amounts of these fermentation products. For all substrates collectively, OM disappearance was highly correlated with both gas production (r2 = 0.782 and 0.723 for 12- and 24-h values, respectively) and SCFA production (r2 = 0.737 and 0.738 for 12- and 24-h values, respectively). In general, OM disappearance, gas production, and SCFA production were related to the insoluble:soluble fiber ratio in the samples; as the insoluble:soluble ratio decreased (increased soluble fiber), the OM disappearance, gas production, and SCFA production increased.

Chemical Composition, in Vitro Fermentation Characteristics, and in Vivo Digestibility Responses by Dogs to Select Corn Fibers

“…Average SCFA production for NCF was 467.1, for HCF, 527.5, and for HECF, 352.4 µmol/g of DM. These values are similar to those for xanthan gum (500 µmol/g of OM) (28). Total SCFA production was higher in some samples with lower SDF concentrations, which can seem contradictory.…”

The Interplay Between Fiber and the Intestinal Microbiome in the Inflammatory Response

“…In rodent studies that used a purified diet and demonstrated anti-inflammatory effects of fermentable fibers, the ratio of fermentable fiber to cellulose was mostly 1:1 or 2:1, with equal intake of two types of fiber or twice as much fermentable fibers. Although fermentability and solubility are two different approaches used to classify fibers, fermentable fibers are usually soluble, whereas insoluble fibers such as cellulose usually have poor fermentability (18). In the United States across a wide range of total fiber intake, the intake ratio of soluble to insoluble fiber was reported to be w1:2-1:3 (62,63), falling short of the intake of fermentable fiber used in the animal studies.…”

“…Although carbohydrates in general are an important source of energy for intestinal microflora (12,13), various fibers show different fermentation potentials (14)(15)(16)(17). Overall, cellulose (b-glucan) in the standard rodent diets showed poor fermentability (17,18), whereas similarly glucose-based resistant starch is readily fermentable (17). Fructose fibers of varying polymer size are fermented at different rates (16,19).…”

Alternative Dietary Fiber Sources in Companion Animal Nutrition

“…Chemical composition and fermentative characteristics of several fruit pomaces were studied using a canine in vitro model [17]. Total dietary fiber concentration varied among the different pomace sources; apple pomace had the greatest TDF concentration (79%), whereas grape pomace had the lowest (55%), tomato pomace and fruit blend (mixture of peach, almond, nectarine and plum) had intermediate values, 57% and 65%, respectively.…”

“…In general, fruit fibers with a greater insoluble:soluble fiber ratio had lower gas production and SCFA production after 12 or 24 h of in vitro fermentation. After 24 h of fermentation, apple pomace had a greater total SCFA concentration (2.1 mmol/g) in contrast to grape pomace, which had the lowest concentration (0.83 mmol/g) [17]. Sunvold et al [12] evaluated in vitro fermentation characteristics of several dietary fiber sources, including citrus pulp and citrus pectin, using fecal inoculum from cats, dogs, horses, pigs, humans and cattle.…”