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Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, Texas A&M University, Texas A&M College of Veterinary Medicine & Biomedical Sciences, 4474 TAMU, College Station, TX 77843-4474, USA
Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, Texas A&M University, Texas A&M College of Veterinary Medicine & Biomedical Sciences, 4474 TAMU, College Station, TX 77843-4474, USA
The gut microbiome is a functional organ, and dietary substrates are converted by different intestinal bacteria to metabolically active compounds that influence the host.
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Butyrate, for example, can be produced from either fiber or protein, suggesting that both increased fiber and increased protein in the diet may bring similar benefits and have the largest impact on the intestinal microbiome and metabolome composition.
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Although fiber and protein content appear to be main influencers of microbiome composition in both dogs and cats, the ideal fiber and protein intake to promote a healthy microbiome needs to be determined.
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Diet-induced changes in the microbiome of healthy dogs are less marked compared with microbiome changes associated with disease.
Background
The gut microbiome is composed of bacteria, archaea, viruses, and eukaryotic organisms that reside in the gastrointestinal (GI) tract. The bacterial component is the largest and provides essential digestive functions, such as fermentation of fibers. The gut microbiome also contributes to host metabolism, protects against pathogens, and educates the immune system. Expanding knowledge of microbiome functions has revealed several remote connections leading to the coinage of terms such as the gut-brain axis, gut-skin axis, and others.
Many diseases, systemic or localized, are associated with dysbiosis. Gut dysbiosis is defined as changes in the composition of the gut microbiome that impact its function.
and the differentiation of intestinal helper T (Th) cell precursors. Intestinal inflammation also can be triggered by gut dysbiosis in different diseases through bile acid dysmetabolism,
Longitudinal assessment of microbial dysbiosis, fecal unconjugated bile acid concentrations, and disease activity in dogs with steroid-responsive chronic inflammatory enteropathy.
Comparison of intestinal expression of the apical sodium-dependent bile acid transporter between dogs with and without chronic inflammatory enteropathy.
and many others, both in dogs and in humans. However, caution should be taken when interpreting those findings, as a causation effect is yet to be proven, and the dysbiosis may be a symptom of the disease process rather than its cause.
The gut microbiome is responsive to nutrients. Changes in bacterial taxa often require large changes in dietary macronutrients; but alterations in bacterial-derived metabolites and, therefore, microbiota function may already occur due to the addition of micronutrients, and this is an emerging area of current microbiome research. Some bacterial species ferment different types of fiber and carbohydrates, and others are strongly proteolytic. Therefore, changes in the diet that affect the availability of such substrates in the gut will result in alterations of the microbiome and metabolome. Due to its resilience, dietary-induced changes in microbiome composition are maintained only by long-term maintenance of a specific diet. A good example is a study
in which healthy dogs were fed diets containing only purified amino acids and easily digestible starch for 32 weeks. At the end of the trial, dogs returned to the control diet, and microbiome composition quickly returned to baseline.
This has a significant evolutionary advantage, because if only a single species performed an essential function, any aggression to the microbiome (such as antibiotic treatment) affecting that species would deprive the host of that function. Therefore, multiple species are necessary for microbiome resilience, and higher species richness is considered an indicator of a healthy microbiome.
The GI tract regions are colonized with different bacterial populations. The composition varies according to luminal conditions, with a predominance of oxygen-tolerating bacteria in the small, and an abundance of strict anaerobes in the large intestine.
Because sampling from the proximal intestine is difficult, most clinical studies focus on fecal microbiota, and the abundance of most relevant bacterial species for gut health in dogs can be reliably measured in feces.
When analyzing the microbiome along the GI tract of cats, samples clustered by individual cat rather than by site of collection, indicating that fecal samples are also representative of the cat microbiome.
Microbiological culture is useful for the subset of bacteria that are culturable, but molecular methods have largely replaced culture due to their ability to capture nonculturable bacteria.
Molecular methods, such as 16S ribosomal RNA (rRNA) gene sequencing and DNA shotgun sequencing, aim to measure the diversity of species present in the sample. That is accomplished by either amplifying and sequencing a fragment of a conserved region of the 16S rRNA gene, or by sequencing all available DNA in the sample (shotgun sequencing). Shotgun sequencing has the advantage of going beyond bacterial identification by also sequencing functional genes; however, it requires larger amounts of DNA from the sample, and is more expensive. Quantitative polymerase chain reaction (qPCR) is a quick, affordable, and reproducible method to quantify specific taxa that have been identified as clinically relevant.
Most studies focus on 16S rRNA gene sequencing, which generates phylogenetical data, and methods for sequencing and data analysis are in constant evolution.
Indeed, this is one disadvantage of these methods: different sequencing and/or data analysis methods may generate differences in the results, which prevents the development of reference intervals. When reviewing the literature, a wide variation in percentages of specific bacterial taxa can be seen, making comparisons between studies difficult.
Another limitation of most microbiome studies is that investigators typically compare the effects of environmental factors (eg, diet, storage, antibiotic treatment, breed influences, geography) with a control group or with its own baseline within the study, and often with a small sample size. Therefore, when changes (eg, due to diets) are observed, it is difficult to extrapolate the magnitude of these changes, and how they compare against a normal microbiota in a large reference population. Because of its high reproducibility, qPCR allows the development of reference intervals for specific taxa. One example is the canine fecal dysbiosis index (DI), a qPCR-based assay that quantifies 7 bacterial taxa, which are then combined into one single number.
Reference intervals for this assay have been established based on 120 healthy dogs from different countries and fed different commercial diets (https://tx.ag/DysbiosisGI). The DI can be used as a marker for normal microbiota, and is useful to track changes in microbiota over time in response to therapy in dogs.
The reference intervals for the 7 bacteria allow for comparison of effect sizes between studies, and whether changes in the microbiota fall within or outside the normal range (Fig. 1).
Fig. 1The canine qPCR-based fecal DI (A) and key bacterial taxa Faecalibacterium (B) and Fusobacterium (C), both butyrate producers through different pathways (from carbohydrate and protein/amino acids, respectively), for different diet types, in comparison with chronic enteropathy
The gray areas indicate reference intervals, which allow comparison across studies and to a large reference population. Dots in red indicate dogs that also had a low abundance of C hiranonis, a beneficial bacterium that converts primary to secondary bile acids in the canine intestine. Dogs with chronic enteropathy and healthy dogs receiving metronidazole have a dysbiosis that is, associated with decreased Faecalibacterium, Fusobacterium, and C hiranonis. Lack of the latter results in abnormal bile acid metabolism. In contrast, dogs fed a raw food diet,
high in protein and fat, and low in fiber, have an increased fecal DI mostly driven due to low Faecalibacterium and increased E coli (not shown). The vegetable protein
fed for 60 and 42 days, respectively, have similar macronutrient composition to commercial adult dog diets, despite the uniqueness of some ingredients. Accordingly, the fecal DI, and abundances of Faecalibacterium and Fusobacterium remained within normal reference intervals.
Key bacterial species are consistently present in fecal samples of healthy dogs, indicating the presence of a core fecal bacterial community. Table 1 shows some of the most relevant bacterial taxa in fecal samples of dogs. The fecal microbiome of healthy dogs is co-dominated by 3 phyla: Firmicutes, Bacteroidetes, and Fusobacterium.
many of which are SCFA producers, such as Faecalibacterium. Bacteroidetes is another abundant phylum in fecal samples from dogs, including Prevotella and Bacteroides, which are highly variable in abundance between dogs.
The genus Fusobacterium is typically associated with health in dogs. This is in contrast to people, in which Fusobacterium nucleatum is a pathogen associated with colorectal cancer.
Therefore, in dogs Fusobacteria may be a therapeutic target for specific food ingredients that can increase their abundance.
Proteobacteria and Actinobacteria are also commonly identified and are typically colonizers of the small intestine, and in physiologic conditions will present in smaller numbers in fecal samples. For example, members of the family Enterobacteriaceae (eg, Escherichia coli) are facultative anaerobes, which allows them to take advantage of the oxygen available in the small intestine. Although part of the normal microbiome in small numbers, an increase of Enterobacteriaceae in fecal samples is a hallmark of dysbiosis
Molecular assessment of the fecal microbiota in healthy cats and dogs before and during supplementation with fructo-oligosaccharides (FOS) and inulin using high-throughput 454-pyrosequencing.
followed by smaller percentages of Proteobacteria, Actinobacteria, Bacteroidetes, and Fusobacteria. One study compared the fecal microbiome of dogs and cats fed species-appropriate commercial diets, and found that cats had a larger number of species than dogs,
hinting at a higher diversity; however, more studies are needed to confirm that finding.
Although changes in microbiome composition can be important, they do not reflect changes in microbiome function. Recent studies are going beyond describing “Who is there?” and investigate the more pressing question of “What are they doing?” The study of bacterial metabolites through fecal metabolomics has revealed some major pathways regulated by bacteria, such as SCFA production, bile acid deconjugation and dehydroxylation, production of neurotransmitters such as serotonin and gamma-aminobutyric acid (GABA), and anti-inflammatory compounds such as indoles. Diet can influence bacterial metabolites, which can remotely affect organs such as the brain, skin, or muscle.
Effects of diets on microbiota in dogs
Most microbiome studies in dogs have evaluated effects of extruded diets, which represent up to 95% of the dog food market. Extruded diets typically include a high carbohydrate load, but high-protein low-carbohydrate alternatives are available. Also increasingly popular are raw diets, frozen or freeze-dried, which are typically meat based and include low carbohydrate percentages. A small but increasing percentage of owners feed homemade diets, either raw or cooked.
Studies have shown that gut microbiome profiles in different species reflect their diet composition, especially when large macronutrient differences such as carnivore versus herbivore diets are considered.
In omnivore species, including humans, the short-term consumption of diets composed entirely of animal or plant products is enough to alter the microbial community structure and overwhelm interindividual differences in microbial gene expression.
In humans, the consumption of an animal-based diet increased the dietary intake of fat and protein, and decreased fiber intake to nearly zero. Such changes led to an increase in the abundance of bile-tolerant microorganisms and decreases the levels of Firmicutes, which includes species known to metabolize dietary plant polysaccharides.
For the canine gut microbiome, the ingredients seem to be less important than the overall macronutrient content. One study found that an extruded diet prepared exclusively with plant sources of protein did not significantly alter the microbiome of dogs when compared with a traditional (mixed animal and plant) extruded diet with similar macronutrient content.
Major shifts in macronutrient composition were tested in a study in healthy dogs, which included 4 dry prescription diets formulated for weight loss, for renal disease, to be low-fat, or anallergenic.
The weight loss diet had the most drastic changes in macronutrients (higher protein and fiber) and resulted in the largest shift in microbiome composition. Increased protein content was associated with increased Fusobacteria. The abundance of SCFA producers Bacteroides, Prevotella, and Faecalibacterium was significantly increased in dogs fed the weight loss diet, and Faecalibacterium was increased in the low-fat diet. The weight-loss (28.1% fiber) and low-fat (8.6% fiber) diets both included soluble and insoluble fiber (beet pulp, fructooligosaccharide [FOS], and psyllium), and the increase in those genera is likely related to increased fiber content and different fiber types.
Different fibers have been studied for their prebiotic properties, and induce specific changes in the microbiome (Table 2). Most fibers act by enriching fiber-fermenting SCFA-producing Firmicutes.
Fecal microbial communities of healthy adult dogs fed raw meat-based diets with or without inulin or yeast cell wall extracts as assessed by 454 pyrosequencing.
Fecal microbial communities of healthy adult dogs fed raw meat-based diets with or without inulin or yeast cell wall extracts as assessed by 454 pyrosequencing.
Fecal microbial communities of healthy adult dogs fed raw meat-based diets with or without inulin or yeast cell wall extracts as assessed by 454 pyrosequencing.
Fecal microbial communities of healthy adult dogs fed raw meat-based diets with or without inulin or yeast cell wall extracts as assessed by 454 pyrosequencing.
have evaluated the impact of meat-based raw diets on the gut microbiome of healthy dogs. Meat-based raw diets are typically very different in macronutrient content compared with control diets, with higher protein and lower carbohydrate and fiber. Dogs fed raw diets showed overall decreases in Firmicutes
indicating a decrease in carbohydrate fermentation due to decreased intake. Proteobacteria, Fusobacteria, and protein-associated genera increased in abundance.
Although Clostridiaceae can be associated with GI disease, it has been suggested that their increase when protein-rich diets are fed to dogs may not be detrimental to their health,
but are rather associated with protein digestion. In addition, Clostridiaceae were also found to positively correlate with protein digestibility and firmer fecal scores, and negatively correlate with fecal protein content (ie, more Clostridiaceae results in less undigested protein in feces) and less fecal output.
Longitudinal assessment of microbial dysbiosis, fecal unconjugated bile acid concentrations, and disease activity in dogs with steroid-responsive chronic inflammatory enteropathy.
reported normal BA metabolism in healthy dogs fed bones and raw foods (BARF) diets, with no significant difference from kibble-fed controls (see Fig. 1). BA metabolism is an important pathway not only for lipid digestion, but also for regulation of intestinal inflammation, and is commonly altered in chronic gastrointestinal diseases.
Longitudinal assessment of microbial dysbiosis, fecal unconjugated bile acid concentrations, and disease activity in dogs with steroid-responsive chronic inflammatory enteropathy.
Comparison of intestinal expression of the apical sodium-dependent bile acid transporter between dogs with and without chronic inflammatory enteropathy.
Bifidobacterium, Lactobacillus, and Faecalibacterium are considered beneficial in omnivores, and the effect of diet on their abundances is often investigated.
Their benefit is due to their role in carbohydrate fermentation resulting in butyrate. The role of butyrate, an SCFA, in intestinal health is undisputed, as butyrate is the preferred energy source for colonocytes.
However, butyrate can be found in fecal samples of all mammals regardless of their food sources. Therefore, in mammals that consume little to no carbohydrates, alternative pathways for butyrate production must be present. In a study comparing high-fat with high-starch diets in dogs, acetate, butyrate, and propionate levels were not different between dogs fed either diet, indicating that the production of SCFA in dogs is not exclusively dependent on carbohydrate content.
found that the addition of minced meat to a dry food diet actually led to a small increase in fecal butyrate and isovalerate.
A recent study has highlighted that in carnivores, Clostridiaceae, and in particular C perfringens, are associated with the butyrate kinase butyrate-synthesis pathway, which allows the production of butyrate from protein.
which was more abundant in a group of dogs fed meat-based raw diets for more than 1 year, suggesting an adaptation of the microbiome to the long-term diet.
Changes in feeding habits promoted the differentiation of the composition and function of gut microbiotas between domestic dogs (Canis lupus familiaris) and gray wolves (Canis lupus).
Those findings bring into question whether bacteria that specialize in carbohydrate fermentation bring the same benefits described in omnivores to the carnivore GI tract.
It is possible that in carnivores the butyrate production may be at least partially accomplished by other bacterial species such as members of the Clostridiaceae and Fusobacteriaceae families, which could be the reason for their increase in dogs fed raw diets.
Another bacteria-derived metabolite that can be affected by diet is GABA, a neurotransmitter, and its precursor gamma-hydroxybutyric acid (GHB).
and it is possible that the high fat and low carbohydrate content of BARF diets trigger similar changes. Both GABA and GHB are quickly absorbed from the GI tract when administered orally,
The connection between the gut and the brain has been studied in many diseases, in dogs and other species, and ketogenic diets have been shown to be beneficial for dogs with neurologic diseases.
Efficacy of medium chain triglyceride oil dietary supplementation in reducing seizure frequency in dogs with idiopathic epilepsy without cluster seizures: a non-blinded, prospective clinical trial.
have shown that ketogenic diets impact microbiome composition, which may be one of the mechanisms by which they reduce seizure frequency.
Effects of diets on microbiota in cats
High-protein/low-carbohydrate diets (HPLC), both extruded and raw, have been studied in cats compared with traditional moderate protein extruded diets. In cats, canned diets are an additional higher protein alternative, which is commonly fed alone or in combination with extruded diets. The use of moist foods in cats is supported by research indicating that their consumption leads to increased water intake,
have evaluated the microbiome of kittens weaned onto HPLC extruded diets compared with kittens weaned onto medium protein/medium carbohydrate (MP/MC) diets. There was some agreement between the studies, and their main findings are summarized in Table 4. Interestingly, species diversity was increased by HPLC,
are known butyrate producers: Clostridium and Eubacterium may produce butyrate either from carbohydrate through the but pathway, or from protein through the buk pathway, whereas Faecalibacterium, Ruminococcus, and Blautia are producers through the but pathway.
Differences between kittens fed either diet affected 194 metabolic pathways, including pathways related to amino acid biosynthesis and metabolism, indicating that the protein:carbohydrate ratio has a significant effect on microbiome function.
Addition of plant dietary fibre to a raw red meat high protein, high fat diet, alters the faecal bacteriome and organic acid profiles of the domestic cat (Felis catus).
Addition of plant dietary fibre to a raw red meat high protein, high fat diet, alters the faecal bacteriome and organic acid profiles of the domestic cat (Felis catus).
↓ Lactobacillus, Bifidobacterium, and Collinsella ↑ Bacteroides, Clostridium, Fusobacterium, genes involved in vitamin biosynthesis, metabolism and transport
Addition of plant dietary fibre to a raw red meat high protein, high fat diet, alters the faecal bacteriome and organic acid profiles of the domestic cat (Felis catus).
Addition of plant dietary fibre to a raw red meat high protein, high fat diet, alters the faecal bacteriome and organic acid profiles of the domestic cat (Felis catus).
(see Table 4). Although the butyrate concentration was not increased in cats fed raw beef, the butyrate molar ratio was higher, indicating a shift in the proportions of different SCFAs. However, when plant fiber (2% as fed, inulin and cellulose) was added to raw beef, the microbiome became more similar to that of cats fed the control extruded diet, and fecal acetate:propionate:butyrate ratio was almost identical to that of controls.
Addition of plant dietary fibre to a raw red meat high protein, high fat diet, alters the faecal bacteriome and organic acid profiles of the domestic cat (Felis catus).
Similarly to raw diets, canned cat food has higher average protein and fat content, and lower carbohydrates content, compared with extruded dry foods. The microbiome of adult cats and kittens fed canned diets is more diverse
(see Table 4). As with other high-protein diets, many genera enriched by canned diets are associated with butyrate production, and may therefore be beneficial for intestinal health.
Addition of plant dietary fibre to a raw red meat high protein, high fat diet, alters the faecal bacteriome and organic acid profiles of the domestic cat (Felis catus).
However, several studies have evaluated the impact of dietary fiber on fecal microbiome composition in cats, and their results are summarized in Table 5. Similar to dogs, prebiotic fibers increase SCFA-producing bacterial genera,
Effects of short-chain fructooligosaccharides and galactooligosaccharides, individually and in combination, on nutrient digestibility, fecal fermentative metabolite concentrations, and large bowel microbial ecology of healthy adults cats.
Effects of short-chain fructooligosaccharides and galactooligosaccharides, individually and in combination, on nutrient digestibility, fecal fermentative metabolite concentrations, and large bowel microbial ecology of healthy adults cats.
Effects of short-chain fructooligosaccharides and galactooligosaccharides, individually and in combination, on nutrient digestibility, fecal fermentative metabolite concentrations, and large bowel microbial ecology of healthy adults cats.
Effects of short-chain fructooligosaccharides and galactooligosaccharides, individually and in combination, on nutrient digestibility, fecal fermentative metabolite concentrations, and large bowel microbial ecology of healthy adults cats.
Molecular assessment of the fecal microbiota in healthy cats and dogs before and during supplementation with fructo-oligosaccharides (FOS) and inulin using high-throughput 454-pyrosequencing.
Specialized dietary fibers alter microbiome composition & promote fermentative metabolism in the lower gastrointestinal tract of healthy adult cats (P20-045-19).
Although diet can change microbiome composition significantly, and result in changes both in metabolic pathways and production of metabolites, those changes are typically much smaller than those that accompany disease.
In sick animals, and in particular those with gastrointestinal disease (eg, chronic enteropathies), microbiome diversity is quickly reduced, and many core species, such as C hiranonis, Fusobacterium spp, and Faecalibacterium praunitzii, are decreased
Longitudinal assessment of microbial dysbiosis, fecal unconjugated bile acid concentrations, and disease activity in dogs with steroid-responsive chronic inflammatory enteropathy.
(see Fig. 1). Therefore, although dietary manipulations of microbiome composition can likely play a role in fostering a healthy and resilient microbe community, they are in most cases unlikely to generate changes comparable in magnitude to those observed in disease.
Diet modification, prebiotics, and probiotics are often used, alone or together with medications, to ameliorate clinical signs of diseases including diarrhea. The changes in microbiome composition associated with diarrhea are extensive and have been reviewed elsewhere,
and are accompanied by functional changes in digestion and motility that modify the luminal environment, further affecting microbiome composition. Hypoallergenic diets, formulated to reduce immunogenicity and facilitate digestion, do not significantly affect the microbiome of healthy dogs,
Comparison of the intestinal mucosal microbiota in dogs diagnosed with idiopathic inflammatory bowel disease and dogs with food-responsive diarrhea before and after treatment.
Similarly, prebiotic fibers can aid recovery of beneficial bacterial populations and restore SCFA production. Probiotics, which are beneficial bacterial species, also can be fed to aid recovery. Although their colonization is typically transient,
Administration of a synbiotic containing enterococcus faecium does not significantly alter fecal microbiota richness or diversity in dogs with and without food-responsive chronic enteropathy.
Randomized, controlled trial evaluating the effect of multi-strain probiotic on the mucosal microbiota in canine idiopathic inflammatory bowel disease.
The gut microbiome is a functional organ, and is responsive to the nutrient composition of diet. However, major shifts in microbiome composition are only observed with major changes in macronutrient composition, such as high-protein or high-fiber diets. More importantly, changes in bacterial composition may affect the production of metabolites in the gut. Indeed, fiber, starch, and protein content seem to be the key modulating players, and changes in those nutrient profiles cause rapid shifts in microbiome and metabolome composition, likely due to the changes in substrate availability. Because of the redundancy of the microbial communities, key metabolites can be produced by different bacteria. Butyrate, for example, can be produced from either fiber or protein, suggesting that both increased fiber or increased protein in the diet may bring similar benefits; however, the ideal levels of fiber and protein remain to be determined. The microbiome of healthy dogs and cats is resilient and adaptable, and it is capable of quickly restoring itself to baseline composition once the animal returns to its usual diet, indicating that sustained change requires long-term administration of a specific diet. Although diet affects the microbiome and metabolome of healthy dogs, changes associated with disease are of greater magnitude. In those cases, dietary change, prebiotic fibers, and probiotic bacteria can be beneficial to help improve microbial diversity and metabolite production.
Disclosure
R. Pilla and J.S. Suchodolski are employed by the Gastrointestinal Laboratory at Texas A&M University, which provides assay for intestinal function and microbiota analysis on a fee-for-service basis.
References
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Inohara N.
Nunez G.
Mechanisms of inflammation-driven bacterial dysbiosis in the gut.
Longitudinal assessment of microbial dysbiosis, fecal unconjugated bile acid concentrations, and disease activity in dogs with steroid-responsive chronic inflammatory enteropathy.
Comparison of intestinal expression of the apical sodium-dependent bile acid transporter between dogs with and without chronic inflammatory enteropathy.
Molecular assessment of the fecal microbiota in healthy cats and dogs before and during supplementation with fructo-oligosaccharides (FOS) and inulin using high-throughput 454-pyrosequencing.
Fecal microbial communities of healthy adult dogs fed raw meat-based diets with or without inulin or yeast cell wall extracts as assessed by 454 pyrosequencing.
Changes in feeding habits promoted the differentiation of the composition and function of gut microbiotas between domestic dogs (Canis lupus familiaris) and gray wolves (Canis lupus).
Efficacy of medium chain triglyceride oil dietary supplementation in reducing seizure frequency in dogs with idiopathic epilepsy without cluster seizures: a non-blinded, prospective clinical trial.
Addition of plant dietary fibre to a raw red meat high protein, high fat diet, alters the faecal bacteriome and organic acid profiles of the domestic cat (Felis catus).
Effects of short-chain fructooligosaccharides and galactooligosaccharides, individually and in combination, on nutrient digestibility, fecal fermentative metabolite concentrations, and large bowel microbial ecology of healthy adults cats.
Comparison of the intestinal mucosal microbiota in dogs diagnosed with idiopathic inflammatory bowel disease and dogs with food-responsive diarrhea before and after treatment.
Administration of a synbiotic containing enterococcus faecium does not significantly alter fecal microbiota richness or diversity in dogs with and without food-responsive chronic enteropathy.
Randomized, controlled trial evaluating the effect of multi-strain probiotic on the mucosal microbiota in canine idiopathic inflammatory bowel disease.
Specialized dietary fibers alter microbiome composition & promote fermentative metabolism in the lower gastrointestinal tract of healthy adult cats (P20-045-19).
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