Many fiber ingredients are used by the pet food industry; however, little data are available regarding the fermentation characteristics of alternative fibers currently being used. The objectives of this study were to determine organic matter disappearance (OMD) and postbiotic production from various fruit and vegetable fiber sources using an in vitro dog fecal inoculum model. Apple pomace (AP), blueberry pomace (BP), cranberry pomace (CP), tomato pomace (TP), and pea fiber (PF) were used as experimental treatments. Inoculum was prepared using freshly voided feces under anaerobic conditions. Predigested fibers were inoculated and incubated for 1, 3, 6, and 12 h at 39 °C. Short-chain fatty acids (SCFA), branched-chain fatty acids (BCFA), total volatile fatty acids (VFA), and OMD were determined for each fiber source and time point in triplicate. After 12 h of incubation, OMD was similar (P > 0.05; average of 18.5%) among treatments. Proportionally, acetate was greater for BP and AP (P < 0.05; average of 80.1%) than for the other treatments (68.3% to 71.2%). Molar proportions of propionate was greatest (P < 0.05) for CP (26.8%) compared to the remaining treatments (13.6 to 20.7%). Butyrate was proportionally greater for PF (7.7%; P < 0.05) than for BP and CP (average of 4.8%) and was lowest for AP (3.8%); however, TP was not different from PF (P > 0.05; average of 7.25%). Total VFA concentration was highest for AP (P < 0.05) followed by TP (1.17 and 0.75 mmol*g-1 of substrate, respectively). Both BP and PF were similar (average of 0.48 mmol*g-1 of substrate) and lower than for TP, with CP having the lowest VFA concentration (0.21 mmol*g-1 of substrate) among all treatments. Additionally, when comparing molar concentrations, AP and TP (average of 0.0476 mmol*g-1 of substrate) had greater butyrate concentrations than did PF (0.0344 mmol*g-1 of substrate). The AP, BP, and TP treatments had both linear and quadratic relationships (Table 7; P < 0.05) for acetate, propionate, and butyrate concentrations across time. CP only demonstrated a linear relationship for propionate (P < 0.05), whereas acetate and butyrate had quadratic relationships with time. PF only demonstrated quadratic relationships between acetate, propionate, and butyrate concentrations and time (P < 0.05). Overall, the fiber substrates evaluated were marginally to moderately fermentable when incubated for up to 12 h with canine fecal inoculum.
Keywords: companion animals; fermentation; fruit; pomace; short-chain fatty acids; volatile fatty acids.
Fibers fermented in the gut result in the production of short-chain fatty acids (SCFA) acetate, propionate, and butyrate. These postbiotic compounds, particularly butyrate, play an important role in colonic and host health. Fibers not degraded by the microbiota aid in stool formation and promote laxation. Many fiber ingredients are used in pet diets; however, data regarding the fermentation characteristics of alternative fiber ingredients are scarce. In this work, substrate degradation and postbiotic analysis were evaluated for apple pomace (AP), blueberry pomace (BP), cranberry pomace (CP), pea fiber (PF), and tomato pomace (TP) incubated for 1, 3, 6, and 12 h at 39 °C using canine fecal inoculum. After 12 h, substrate degradation was not different among treatments due to high variability. AP had the highest concentration of total SCFA, followed by TP, BP, PF, and CP. The molar proportion of acetate was greatest for AP and BP. CP had the highest molar proportion of propionate. PF had greater molar proportions of butyrate than did AP, BP, and CP, but had similar molar proportions as TP. Additionally, the molar concentrations of butyrate were greatest for AP and TP. Overall, fiber substrates were marginally to moderately fermentable when incubated for up to 12 h with canine fecal inoculum.
© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science.