The Microbiome

Independent Research: Raw Meat vs Kibble Diets and the Canine Microbiome

A 2024 peer-reviewed study compared 55 healthy dogs fed either a raw meat-based diet or kibble. The two diet groups differed in faecal microbiota composition and in 63 serum metabolites, yet major systemic inflammatory markers were similar. The study is a useful example of why microbiome or metabolome differences should not automatically be interpreted as evidence that one diet is healthier.

Peer reviewed Open access

Independent Research: Raw Meat vs Kibble Diets and the Canine Microbiome

Year

2024

Study type

Peer-reviewed comparative dietary study

Sample

55 clinically healthy dogs

Duration

28-day standardised feeding period following at least 1 year on the respective diet type

Measured

Faecal microbiota, serum metabolomics, faecal immune markers and systemic inflammatory markers

How did raw-fed and kibble-fed dogs differ in this study?

Raw meat-based diets and conventional kibble differ substantially in ingredient composition, macronutrients and processing.

Those differences could influence both the intestinal microbiome and the metabolites circulating in the body.

Hiney and colleagues therefore asked:

Do dogs fed raw meat-based diets have different faecal microbiota, serum metabolite profiles and inflammatory markers from dogs fed kibble?

The study is particularly useful because it examined several biological layers at the same time rather than assuming that a change in the microbiome automatically represented a health benefit.

How were the diet groups selected and standardised?

Researchers recruited clinically healthy dogs that had already been eating either:

a raw meat-based diet

a kibble diet

for at least one year.

After veterinary assessment, 55 dogs were included:

28 raw-fed dogs

27 kibble-fed dogs

For the study period, the diets were standardised for 28 days.

Dogs in the kibble group received a defined kibble diet.

Dogs in the raw group received a defined raw meat-based diet.

Serum and faecal samples were then collected.

Researchers examined:

faecal bacterial composition

serum metabolites

faecal markers associated with intestinal immune activity

and

systemic inflammatory markers

Statistical models also accounted for age and body condition score because the two groups were not identical at baseline.

Which microbial, metabolic and inflammatory markers were measured?

Several types of data were collected.

Faecal microbiota composition

Researchers compared the relative abundance and diversity of bacterial communities between the two diet groups.

Serum metabolomics

A broad panel of circulating metabolites was measured to determine whether the diets were associated with different metabolic profiles.

Faecal immune markers

These included:

intestinal alkaline phosphatase

IgA

IgG

Systemic inflammatory markers

The researchers also measured markers including:

C-reactive protein

galectin

soluble receptor for advanced glycation end-products

haptoglobin

serum IgG

Looking at these measures together allowed the researchers to distinguish between:

microbial differences

metabolic differences

and

evidence of systemic inflammation

What differences were observed between the diet groups?

The two diets produced clear biological differences.

The faecal microbiota differed

Overall microbial community composition differed between raw-fed and kibble-fed dogs.

Raw-fed dogs had greater relative abundance of several Fusobacteria-associated groups.

Kibble-fed dogs had greater relative abundance of several Firmicutes-associated groups, including Erysipelotrichaceae and Catenibacterium.

Some measures of microbial diversity also differed between the groups.

The serum metabolome differed substantially

Researchers identified 148 known metabolites.

After adjustment for age, body condition and multiple statistical comparisons, 63 serum metabolites remained significantly different between diet groups.

Many of these differences reflected the very different macronutrient composition of the diets.

Some local intestinal markers differed

Faecal intestinal alkaline phosphatase, IgA and IgG were higher in raw-fed dogs.

The biological significance of these findings is not yet clear.

Systemic inflammation was broadly similar

Major systemic inflammatory markers, including C-reactive protein, haptoglobin and several other measures, did not differ significantly between diet groups.

This is particularly important.

The diets clearly produced different microbial and metabolic profiles, but those differences did not translate into a clear difference in systemic inflammatory status.

Why does a biological difference not automatically mean a health benefit?

This study demonstrates very clearly that diet is a major environmental influence on the canine gut microbiome and metabolome.

Dogs eating substantially different diets developed different microbial communities and different circulating metabolite profiles.

But the study also demonstrates something equally important:

Different does not automatically mean better or worse.

A microbiome shift is not inherently evidence of improved health.

A metabolite difference is not inherently evidence of benefit.

To understand biological significance, those measurements need to be considered alongside health outcomes and other physiological markers.

In this study:

Diet changed microbiome composition

and

Diet changed the serum metabolome

but

Systemic inflammatory markers were broadly similar

That makes this a useful example of why microbiome science requires cautious interpretation.

It also reinforces the wider Science Hub framework:

Diet → Digestion and nutrient exposure → Microbiome → Metabolites

Changing the input changed several downstream layers of biology.

The health meaning of those changes, however, requires separate evidence.

Another dietary comparison comes from research on how different fibres shape the canine microbiome and metabolome.

What limits the comparison of raw and kibble feeding?

Several limitations are important.

The dogs were not randomly assigned to their long-term diets

Owners had already chosen raw or kibble feeding before recruitment.

Dogs in the two groups may therefore have differed in ways beyond diet.

The groups differed at baseline

Raw-fed dogs were older and leaner on average.

The statistical analysis adjusted for these factors, but adjustment cannot necessarily remove every source of confounding.

The diets differed in many ways

Raw and kibble diets differed in processing, protein, fat, carbohydrate and ingredient composition.

The study therefore cannot identify one particular dietary feature as the cause of the observed microbiome or metabolome differences.

Short standardisation period

Although dogs had eaten their respective diet types for at least a year, the specifically standardised study diets were fed for 28 days.

Microbiome differences do not establish health effects

The presence or relative abundance of particular bacterial groups should not automatically be labelled beneficial or harmful.

Long-term outcomes were not measured

The authors explicitly note that further work is required to determine whether the observed differences have meaningful consequences for long-term canine health.

Original research

Study details

Study

Fecal microbiota composition, serum metabolomics, and markers of inflammation in dogs fed a raw meat-based diet compared to those on a kibble diet

Authors

Kris Hiney
Lara Sypniewski
Udaya DeSilva
Adel Pezeshki
Pratyaydipta Rudra
Parniyan Goodarzi
Erin Willis
Dianne McFarlane

Institutions

Oklahoma State University

University of Florida

Reference

Hiney K, Sypniewski L, DeSilva U, Pezeshki A, Rudra P, Goodarzi P, Willis E, McFarlane D. Fecal microbiota composition, serum metabolomics, and markers of inflammation in dogs fed a raw meat-based diet compared to those on a kibble diet. Frontiers in Veterinary Science. 2024;11:1328513.

Published 17 April 2024.

Fifty-five clinically healthy dogs were included: 28 fed a raw meat-based diet and 27 fed kibble. Researchers compared faecal microbiota, serum metabolomics, faecal immune markers and systemic inflammatory markers.

DOI: 10.3389/fvets.2024.1328513

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