This result should be interpreted carefully.
This was not a randomised probiotic trial
Dogs were already receiving probiotics as part of their normal routine.
The researchers did not allocate dogs to treatment.
The probiotic products were not standardised
Different dogs may have been receiving different:
species
strains
formulations
doses
and frequencies
This is a major limitation.
The study cannot determine whether one particular probiotic product was effective or ineffective.
Duration of probiotic use was not controlled
Dogs may have been receiving probiotics for very different lengths of time.
Only faecal bacterial composition was examined
The study did not comprehensively measure the metabolome or other functional outcomes.
A probiotic could potentially alter microbial activity without causing a large shift in bacterial composition.
Cross-sectional design
Dogs were compared with one another rather than being measured before and after starting a probiotic.
Individual baseline differences therefore remain important.
Healthy dogs
The results should not automatically be applied to dogs with gastrointestinal disease or other clinical conditions.
Small effect does not mean no effect
An intervention could produce a biologically meaningful change in a narrow pathway without explaining much of the total variation in the entire microbiome.
Commercial involvement
The study was funded by AnimalBiome, and all authors were employees of the company.
That does not invalidate the findings, but it is relevant context when interpreting the study.
The correct conclusion is therefore not:
probiotics do nothing
It is:
probiotic use was associated with very little of the overall variation in faecal microbiome structure in this population of healthy dogs.
