Canine Gut Science Glossary: Key Terms Explained

Canine gut research uses a lot of technical language.

Terms such as microbiome, metabolomics, 16S sequencing, substrate, short-chain fatty acids and bioavailability appear repeatedly throughout the Science Hub.

They are useful terms, but only if they are understood.

The big question is:

What do the most common words in canine digestion and microbiome science actually mean?

Absorption

The movement of digested nutrients across the intestinal lining and into the body.

Amylase

An enzyme that helps break down starch into smaller carbohydrate molecules.

Anabiomics

A framework describing approaches intended to support a healthier microbiome without introducing foreign microorganisms.

In the CaniNectar Science Hub, the term is used particularly in relation to upstream digestion and substrate availability.

Bioaccessibility

The proportion of a nutrient that is released from food and becomes available for absorption.

Bioavailability

The proportion of a nutrient that becomes available for normal physiological use after digestion and absorption.

Beta-glucan

A type of complex carbohydrate made from glucose molecules joined by beta-linked bonds.

Beta-glucans occur naturally in materials including barley and oats.

Beta-glucanase

An enzyme capable of breaking particular bonds within beta-glucans.

Butyrate

A short-chain fatty acid produced by microbial fermentation.

Butyrate is widely studied because it can be used as an energy source by cells lining the large intestine and participates in wider intestinal signalling.

Cellulase

An enzyme capable of breaking bonds within cellulose.

Dogs do not produce substantial endogenous cellulase activity.

Colon

The major part of the large intestine.

It contains a dense microbial community and is an important site of water absorption and microbial fermentation.

Digestibility

A measure of how much of a nutrient disappears from the gastrointestinal tract rather than being excreted.

Digestibility is related to absorption but is not exactly the same as bioavailability.

Digestive enzyme

A biological catalyst that helps break food molecules into smaller components.

Examples include amylase, proteases and lipase.

Dysbiosis

A term used to describe an alteration in the composition or function of a microbial community compared with a reference or expected state.

It does not refer to one single microbiome pattern.

Enzyme

A biological catalyst.

Enzymes accelerate chemical reactions without being consumed by those reactions.

Enzyme activity

A measure of what an enzyme is actually capable of doing.

The presence of an enzyme protein does not necessarily mean that it remains fully active.

Faecal metabolomics

The study of small molecules present in faeces.

These compounds can originate from diet, digestion, the dog, microbial metabolism or combinations of all of these.

Fermentation

The microbial processing of substrates, often carbohydrates, in the absence of oxygen.

Fermentation can produce metabolites including short-chain fatty acids.

Fructan

A carbohydrate composed largely of chains of fructose molecules.

Fructans can become substrates for microbial fermentation if they reach the lower gastrointestinal tract.

Fructanase

Enzyme activity capable of breaking bonds within fructan molecules.

Gut-brain axis

The two-way communication network linking the gastrointestinal tract and the nervous system.

It includes neural, endocrine, immune and microbial signalling pathways.

Gut microbiome

The community of microorganisms living within the gastrointestinal tract together with their collective genetic and functional activity.

Ileum

The final section of the small intestine.

Absorption continues here before material enters the large intestine.

Jejunum

A major section of the small intestine and an important site of nutrient digestion and absorption.

Lipase

An enzyme involved in breaking down dietary fats.

Metabolite

A small molecule produced, consumed or transformed during biological processes.

Gut metabolites can originate from the dog, diet or microorganisms.

Metabolome

The collection of metabolites present within a biological system or sample at a particular time.

Metabolomics

The study of many metabolites together.

It can provide information about biological activity that cannot be obtained from microbial composition alone.

Microbial composition

A description of which microorganisms are present within a community and their relative abundance.

Microbial function

What microorganisms are doing rather than simply which organisms are present.

This includes metabolic activity and production or transformation of compounds.

Microbiota

The microorganisms themselves.

The word is often used interchangeably with microbiome, although microbiome can also include their collective genes and functions.

Phytase

An enzyme that acts on phytate and can release phosphate groups from the molecule.

Phytate

A phosphorus-containing compound found particularly in seeds and cereal grains.

It can interact with minerals and influence their availability.

Prebiotic

A substrate selectively utilised by host microorganisms that is intended to confer a health benefit.

Probiotic

A live microorganism administered in adequate amounts with the intention of providing a health benefit to the host.

Protease

A general term for enzymes that break peptide bonds within proteins.

Relative abundance

The proportion of detected microbial sequences assigned to a particular bacterial group.

An increase in relative abundance does not necessarily mean that the absolute number of those bacteria increased.

Short-chain fatty acids

A group of small fatty acids produced largely through microbial fermentation.

Important examples include acetate, propionate and butyrate.

Small intestine

The section of the digestive tract comprising the duodenum, jejunum and ileum.

It is a major site of enzymatic digestion and nutrient absorption.

Substrate

A substance that an enzyme or microorganism can act upon.

In microbiome science, substrate often refers to dietary material available for microbial metabolism.

16S microbiome analysis

A genetic method used to study bacterial communities by analysing regions of the bacterial 16S ribosomal RNA gene.

It is mainly used to investigate which bacterial groups are present and their relative abundance.

Volatile organic compounds

Small carbon-containing compounds that can readily enter the gas phase.

Some are produced during microbial metabolism and can be measured in faecal samples.

Xylan

A complex carbohydrate found within plant cell walls.

It belongs to a broader group of plant carbohydrates known as hemicelluloses.

Xylanase

An enzyme capable of breaking particular bonds within xylan.