The Microbiome

Independent Research: What Did a Probiotic Actually Change in Healthy Dogs?

A 2024 controlled study tested three doses of the probiotic Pediococcus acidilactici GLP06 in 24 healthy beagles. Although the highest dose altered several microbiome, short-chain fatty acid, antioxidant and immune measurements, probiotic supplementation did not significantly improve overall nutrient digestibility, nitrogen utilisation or feed intake. The findings illustrate both the potential and the limitations of directly adding live bacteria to an already established canine gut ecosystem.

Peer reviewed Open access

Independent Research: What Did a Probiotic Actually Change in Healthy Dogs?

Year

2024

Study type

Peer-reviewed randomised controlled dietary intervention study

Sample

24 healthy adult beagles

Duration

5 weeks

Measured

Nutrient digestibility, faecal score, nitrogen metabolism, microbiome composition, short-chain fatty acids, serum antioxidant markers, immunoglobulins and metabolome

The research question

Probiotics attempt to influence the gut by introducing live microorganisms.

But does adding more bacteria necessarily improve digestion or produce a meaningful change in a healthy dog?

Zhao and colleagues investigated a canine-derived strain called Pediococcus acidilactici GLP06.

Twenty-four healthy adult beagles were randomly assigned to receive either:

no probiotic

a low dose

a medium dose

a high dose

The researchers examined digestion, microbiome composition, short-chain fatty acids, immune markers, antioxidant measurements and the metabolome.

The study therefore allows a useful question to be asked:

When live bacteria are introduced into an already established canine gut ecosystem, what actually changes?

What did the researchers do?

Twenty-four healthy adult beagles were randomly divided into four groups of six dogs.

Each group contained three males and three females.

The control group received the standard diet without probiotic supplementation.

The three intervention groups received the same diet plus different quantities of Pediococcus acidilactici GLP06:

Low dose

2 × 10⁸ colony-forming units per dog per day.

Medium dose

2 × 10⁹ colony-forming units per dog per day.

High dose

2 × 10¹⁰ colony-forming units per dog per day.

The experiment lasted five weeks, including an initial adaptation period.

The probiotic bacteria were administered directly rather than incorporated into a normal commercial feeding format.

Researchers measured:

faecal characteristics

apparent total tract nutrient digestibility

nitrogen metabolism

serum antioxidant markers

immune proteins

faecal short-chain fatty acids

microbiome composition

and faecal metabolite profiles.

What did they measure?

The researchers looked at a broad range of outcomes.

Faecal scores

Stool consistency was followed during the intervention.

Digestibility

The apparent total tract digestibility of:

dry matter

crude protein

fat

ash

and carbohydrate

was measured.

Nitrogen metabolism

Researchers measured nitrogen intake, faecal and urinary nitrogen, retained nitrogen, net protein utilisation and biological value.

Short-chain fatty acids

Faecal concentrations of compounds including acetate, butyrate and other short-chain fatty acids were assessed.

Microbiome composition

16S analysis was used to compare bacterial communities between groups.

Metabolome

Researchers examined broad changes in faecal metabolites.

Serum and immune measurements

Several antioxidant enzymes and immunoglobulin measurements were also compared.

What was observed?

The results were mixed.

Digestibility did not improve

There were no statistically significant differences between the probiotic and control groups in apparent total tract digestibility of:

dry matter

protein

fat

ash

or carbohydrate.

This is important because one might expect a gut-directed nutritional intervention to improve nutrient utilisation.

That was not demonstrated here.

Nitrogen utilisation did not improve

Nitrogen intake, faecal nitrogen, urinary nitrogen, retained nitrogen, net protein utilisation and biological value were also not significantly different between probiotic and control groups.

Feed intake did not change

Average daily food intake was similar across all groups.

Stool differences emerged later

Faecal scores did not differ significantly during the first two weeks.

Differences were reported during weeks three and four.

Many positive findings were concentrated at the highest dose

The most pronounced differences in antioxidant measurements, immune proteins, microbiome composition and short-chain fatty acids generally occurred in dogs receiving the highest probiotic dose: 2 × 10¹⁰ colony-forming units per dog per day.

Short-chain fatty acids increased at the high dose

Acetate was higher in the high-dose group than in all other groups.

Butyrate, isobutyrate and total short-chain fatty acids were also significantly higher than in controls.

The microbiome changed

The high-dose group had higher alpha diversity and greater relative abundance of several bacterial groups that the authors described as beneficial.

Lower and medium doses produced different taxonomic changes rather than one consistent dose-independent microbial response.

The metabolome changed substantially

Comparison of the high-dose and control groups identified 111 metabolites reported as increased and 171 as decreased.

These are substantial chemical differences, but the biological meaning of many of those metabolite shifts remains uncertain.

What does this study tell us?

This study shows that introducing a probiotic organism can alter parts of the canine gut ecosystem.

At sufficiently high amounts, Pediococcus acidilactici GLP06 changed:

microbiome composition

short-chain fatty acid concentrations

metabolite profiles

and several blood and immune measurements.

But those changes did not translate into broad improvements in nutrient digestion or nitrogen utilisation.

That distinction matters.

A microbiome change is not automatically equivalent to improved digestive function.

Nor does an increase in a bacterial group labelled “beneficial” establish a meaningful health outcome on its own.

The dose response is also noteworthy.

Many of the stronger findings occurred only in the group receiving 20 billion live organisms per dog per day.

The lower doses produced fewer and different effects.

This illustrates an important feature of probiotic interventions:

the organism, dose and existing microbial ecosystem all matter.

Simply adding live bacteria does not guarantee that they will produce the desired functional outcome.

The study therefore supports the possibility that probiotics can modify the gut environment while also demonstrating that modification and functional improvement are not necessarily the same thing.

What doesn't this study tell us?

Several limitations substantially restrict what can be concluded.

Only six dogs per group

Twenty-four dogs were divided across four treatment groups.

That leaves only six animals in each comparison group, making results particularly vulnerable to individual variation.

Healthy research beagles

All dogs were healthy adult beagles living under controlled conditions.

The study does not show whether the same effects would occur in pet dogs, different breeds or dogs with digestive problems.

Short study duration

The intervention lasted only a few weeks.

The persistence of the microbial changes after supplementation stopped was not established.

Very high probiotic exposure

The strongest effects generally occurred at the highest dose of 2 × 10¹⁰ colony-forming units per dog each day.

Results at this level should not automatically be extrapolated to lower-dose commercial probiotic products.

No broad improvement in digestibility

Despite numerous changes in microbiome and biochemical measurements, macronutrient digestibility was not significantly improved.

No meaningful clinical endpoint

The study did not test whether the dogs became healthier, more comfortable, calmer, more resilient or less likely to develop disease.

It principally measured biological markers.

Microbiome terminology requires caution

The authors describe some increased bacterial groups as “beneficial”.

However, bacterial genera are not universally beneficial or harmful, and relative abundance alone does not establish biological effect.

Large numbers of measurements

The study examined many microbiological, metabolic, biochemical and immune outcomes.

When large numbers of variables are tested, apparently significant findings require careful interpretation and ideally independent replication.

For these reasons, the study provides evidence that this probiotic can alter biological measurements in healthy dogs, but much weaker evidence that those alterations produce a meaningful functional benefit.

Original research

Study details

Study

Impact of Pediococcus acidilactici GLP06 supplementation on gut microbes and metabolites in adult beagles: a comparative analysis

Authors

Mengdi Zhao

Yuanyuan Zhang

Yueyao Li

Keyuan Liu

Kun Bao

Guangyu Li

Institutions

College of Animal Science and Technology, Qingdao Agricultural University, Qingdao, China

College of Animal Science and Technology, Jilin Agricultural University, Changchun, China

Reference

Zhao M, Zhang Y, Li Y, Liu K, Bao K, Li G. Impact of Pediococcus acidilactici GLP06 supplementation on gut microbes and metabolites in adult beagles: a comparative analysis. Frontiers in Microbiology. 2024;15:1369402.

Published 3 April 2024.

Twenty-four healthy adult beagles were randomly allocated to a control group or one of three probiotic doses ranging from 2 × 10⁸ to 2 × 10¹⁰ CFU per dog per day.

The study measured nutrient digestibility, nitrogen metabolism, serum antioxidant and immune markers, faecal short-chain fatty acids, microbiome composition and metabolomics.

DOI: 10.3389/fmicb.2024.1369402

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