Adding a polyphenol-rich fiber bundle to food impacts the gastrointestinal microbiome and metabolome in dogs

Introduction

Pet foods fortified with fermentable fibers are often indicated for dogs with gastrointestinal conditions to improve gut health through the production of beneficial post-biotics by the pet's microbiome.

Methods

To evaluate the therapeutic underpinnings of pre-biotic fiber enrichment, we compared the fecal microbiome, the fecal metabolome, and the serum metabolome of 39 adult dogs with well-managed chronic gastroenteritis/enteritis (CGE) and healthy matched controls. The foods tested included a test food (TF1) containing a novel pre-biotic fiber bundle, a control food (CF) lacking the fiber bundle, and a commercially available therapeutic food (TF2) indicated for managing fiber-responsive conditions. In this crossover study, all dogs consumed CF for a 4-week wash-in period, were randomized to either TF1 or TF2 and fed for 4 weeks, were fed CF for a 4-week washout period, and then received the other test food for 4 weeks.

Results

Meaningful differences were not observed between the healthy and CGE dogs in response to the pre-biotic fiber bundle relative to CF. Both TF1 and TF2 improved stool scores compared to CF. TF1-fed dogs showed reduced body weight and fecal ash content compared to either CF or TF2, while stools of TF2-fed dogs showed higher pH and lower moisture content vs. TF1. TF1 consumption also resulted in unique fecal and systemic metabolic signatures compared to CF and TF2. TF1-fed dogs showed suppressed signals of fecal bacterial putrefactive metabolism compared to either CF or TF2 and increased saccharolytic signatures compared to TF2. A functional analysis of fecal tryptophan metabolism indicated reductions in fecal kynurenine and indole pathway metabolites with TF1. Among the three foods, TF1 uniquely increased fecal polyphenols and the resulting post-biotics. Compared to CF, consumption of TF1 largely reduced fecal levels of endocannabinoid-like metabolites and sphingolipids while increasing both fecal and circulating polyunsaturated fatty acid profiles, suggesting that TF1 may have modulated gastrointestinal inflammation and motility. Stools of TF1-fed dogs showed reductions in phospholipid profiles, suggesting fiber-dependent changes to colonic mucosal structure.

Discussion

These findings indicate that the use of a specific pre-biotic fiber bundle may be beneficial in healthy dogs and in dogs with CGE.

Microbiome function underpins the efficacy of a fiber-supplemented dietary intervention in dogs with chronic large bowel diarrhea

Background

Chronic large bowel diarrhea is a common occurrence in pet dogs. While nutritional intervention is considered the primary therapy, the metabolic and gut microfloral effects of fiber and polyphenol-enriched therapeutic foods are poorly understood.

Methods

This prospective clinical study enrolled 31 adult dogs from private veterinary practices with chronic, active large bowel diarrhea. Enrolled dogs received a complete and balanced dry therapeutic food containing a proprietary fiber bundle for 56 days. Metagenomic and metabolomic profiling were performed on fecal samples at Days 1, 2, 3, 14, 28, and 56; metabolomic analysis was conducted on serum samples taken at Days 1, 2, 3, 28, and 56.

Results

The dietary intervention improved clinical signs and had a clear effect on the gut microfloral metabolic output of canines with chronic diarrhea, shifting gut metabolism from a predominantly proteolytic to saccharolytic fermentative state. Microbial metabolism of tryptophan to beneficial indole postbiotics and the conversion of plant-derived phenolics into bioavailable postbiotics were observed. The intervention altered the endocannabinoid, polyunsaturated fatty acid, and sphingolipid profiles, suggesting a modulation in gastrointestinal inflammation. Changes in membrane phospholipid and collagen signatures were indicative of improved gut function and possible alleviation of the pathophysiology related to chronic diarrhea.

Conclusions

In dogs with chronic diarrhea, feeding specific dietary fibers increased gut saccharolysis and bioavailable phenolic and indole-related compounds, while suppressing putrefaction. These changes were associated with improved markers of gut inflammation and stool quality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03315-3.

Varying Protein Levels Influence Metabolomics and the Gut Microbiome in Healthy Adult Dogs

The optimal ranges of protein for healthy adult dogs are not known. This study evaluated the impact of long-term consumption of foods containing low, medium, and high levels of protein on serum, urine, and fecal metabolites, and gut microbiome in beagles. Following maintenance on a prefeed food for 14 days, dogs (15 neutered males, 15 spayed females, aged 2–9 years, mean initial weight 11.3 kg) consumed the low (18.99%, dry matter basis), medium (25.34%), or high (45.77%) protein foods, each for 90 days, in a William’s Latin Square Design sequence. In serum and/or urine, metabolites associated with inflammation (9,10-dihydroxyoctadecanoic acid (DiHOME)), 12,13-DiHOME) and kidney dysfunction (urea, 5-hydroxyindole sulfate, 7-hydroxyindole sulfate, p-cresol sulfate) increased with higher protein levels in food, while one-carbon pathway metabolites (betaine, dimethylglycine, sarcosine) decreased. Fecal pH increased with protein consumed, and levels of beneficial indoles and short-chain fatty acids decreased while branched-chain fatty acids increased. Beta diversity of the fecal microbiome was significantly different, with increased abundances of proteolytic bacteria with higher protein food. Feeding dogs a high amount of protein leads to a shift to proteolytic gut bacteria, higher fecal pH, and is associated with increased levels of metabolites linked with inflammation and kidney dysfunction.

Specialized Dietary Fibers Alter Microbiome Composition & Promote Fermentative Metabolism in the Lower Gastrointestinal Tract of Healthy Adult Cats (P20-045-19)

Objectives

The feline gastrointestinal (GI) microbiome is capable of fermenting fibers. We evaluated specialized dietary plant fibers on feline GI microbiome composition & metabolism.

Methods

46 healthy adult cats were fed control food (CF) for 4 wks & test food (TF) for 8 wks (CF: 4129 kcal/kg, 1.6 g total dietary fiber, TDF; 0.7 g soluble fiber, SF; & 0.9 g insoluble fiber, INSF, per 100 kcal; TF: 4010 kcal/kg, 3.2 g TDF, 0.3 g SF, 2.9 g INSF per 100 kcal). All foods were complete balanced dry products & met 2017 AAFCO maintenance guidelines. CF fiber sources: cracked pearled barley, corn, dried beet pulp, fructooligosaccharides (FOS) & psyllium seed husk; TF: corn, ground pecan shells, cracked pearled barley, whole grain oats, dried beet pulp, pea fiber, flaxseed, dried citrus pulp, pumpkin, cranberry pomace, FOS & psyllium seed husk. Feces were collected after 4 wks of CF & after 4 & 8 wks of TF, cleaned of litter, homogenized, & frozen at −70C within 1 hour of defecation. Cats had free access to water, natural daylight & enrichment from toys, other cats & people. The study was reviewed & approved by the Institutional Animal Care & Use Committee, Hill's Pet Nutrition, Inc. Fecal microbiome 16 s rRNA sequencing was performed using Illumina MiSeq & processed by Mothur. Predicted microbial functions were determined by PICRUSt & analyzed using PERMANOVA. The copy number corrected OTU counts were analyzed using negative binomial mixed models. Fecal short chain fatty acids (SCFA) were analyzed using liquid-liquid extraction & gas chromatography with flame ionization detection. Results significant at P < 0.05 are reported.

Results

At 4 & 8 wks, TF significantly increased acetic & propionic acids, decreased isobutyric, 2-methylbutyric, & isovaleric acids. The genera Peptococcus, Succinivibrio & Enterococcus were significantly decreased vs. CF at 4 & 8 wks while Blautia, Bacteroides, & Turicibacter were significantly increased vs. CF at 4 & 8 wks. Predicted microbial functions representing arginine, benzoate, butyrate, phenylalanine, propionate, tryptophan & tyrosine metabolic pathways were significantly different from CF at 4 wks.

Conclusions

TF shifts feline GI microbiome composition & metabolism toward saccharolytic fermentation & decreases putrefactive metabolites, characteristics which may benefit feline GI health.

Funding Sources

This study was funded by Hill's Pet Nutrition, Inc.

Select Dietary Fibers Alter GI Microbiome Composition & Promote Fermentative Metabolism in the Lower Gastrointestinal Tract of Healthy Adult Dogs (P20-044-19)

Objectives

The canine gastrointestinal (GI) microbiome is capable of fermenting fibers. We evaluated select dietary plant fibers on canine GI microbiome composition & metabolism.

Methods

39 adult dogs were fed a control food (CF) for 4 weeks, then fed a test food (TF) for 4 weeks. (CF: 3411 kcals/kg, 2.2 g total dietary fiber, TDF; 0.5 g soluble fiber, SF; 1.7 g insoluble fiber, INSF per 100 kcal; TF: 3273 kcal/kg, 5.0 g TDF, 0.8 g SF, 4.2 g INSF per 100 kcal). Foods were complete & balanced dry foods & met 2017 AAFCO nutritional guidelines. CF fiber sources: cracked pearled barley, whole corn, whole grain oats, cellulose; TF: cracked pearled barley, whole corn, whole grain oats, ground pecan shells, cellulose, flaxseed, dried beet pulp, dried citrus pulp, pressed cranberries, dried pumpkin, psyllium seed husks, & ginger root. Feces were collected after 4 weeks of feeding CF and TF, homogenized, & frozen at −80C within 1 hour of defecation. Fecal microbiome 16 s rRNA sequencing was performed using Illumina MiSeq and processed through Mothur. Predicted microbial functions were determined by PICRUSt and analyzed using PERMANOVA. Count-normalized data were CLR transformed & analyzed using negative binomial mixed models. Fecal short chain fatty acids (SCFA) were analyzed using liquid-liquid extraction & gas chromatography with flame ionization detection. Results significant at P < 0.05 are reported. The study was reviewed & approved by the Institutional Animal Care & Use Committee, Hill's Pet Nutrition, Inc. Dogs had access to clean fresh water at all times.

Results

TF significantly increased fecal acetic acid, decreased putrefactive metabolites such as isobutyric, 2-methylbutyric, & isovaleric acids. The acetate-& lactate-producing genera Bacteroides and Faecalibacterium were significantly increased while Streptococus and Enterococcus were significantly decreased vs CF. Predicted microbial functions representing butyrate, phenylalanine & tyrosine metabolic pathways were significantly different from CF.

Conclusions

TF shifts canine GI microbiome composition and metabolism toward saccharolytic fermentation & decreases putrefactive metabolites, characteristics which provide beneficial impacts to canine GI health.

Funding Sources

This study was funded by Hill's Pet Nutrition, Inc.