When discussing canine and feline digestion, insoluble fibre is one of the most misunderstood topics in modern pet nutrition.
For decades, processed pet food companies have added plant fibres like cellulose, beet pulp, pea fibre, wheat bran and psyllium husk into commercial diets. These ingredients are often marketed as “healthy fibre,” “digestive support,” or “gut health ingredients.”
But are dogs and cats actually designed to consume large amounts of vegetable insoluble fibre?
Or is there a major difference between plant fibre and the natural animal-based roughage carnivores evolved consuming?
At RogueRaw, we believe understanding this difference is critical for your pet’s digestive health, stool quality, microbiome function and long-term vitality.
What Is Insoluble Fibre?
Insoluble fibre is a type of roughage that does not dissolve in water and is poorly digested by the body.
Its primary role is mechanical:
- adding bulk to stools
- altering transit time
- stimulating bowel movement
- affecting fermentation inside the GI tract
There are two very different forms of insoluble fibre commonly discussed in pet nutrition:
1. Vegetable Insoluble Fibre
Derived from plants such as:
- cellulose
- pea fibre
- beet pulp
- wheat bran
- psyllium husk
- soy hulls
These fibres are carbohydrate-based plant structures made from:
- cellulose
- hemicellulose
- lignin
2. Animal Fibre (Fur)
Naturally found in prey animals:
- fur
- feathers
- connective tissue
- cartilage
- hide
Fur is primarily made from keratin — a structural protein rather than a plant carbohydrate.
This distinction matters enormously.
Dogs & Cats Are Carnivores First
Dogs and cats evolved consuming prey animals — not bowls full of plant matter.
Wild canids and felids naturally consume:
- fur
- feathers
- skin
- connective tissue
- cartilage
- bone
- stomach contents
This provides a natural form of roughage often referred to in raw feeding as “animal fibre” or “prey fibre.”
The anatomy of dogs and cats reflects this:
- short digestive tracts
- acidic stomachs
- carnivorous teeth
- protein and fat metabolism dominance
RogueRaw Why Raw Feeding Guide explains how modern processed diets evolved around convenience and fillers rather than biological appropriateness.
The Problem With Excess Vegetable Insoluble Fibre
Small amounts of plant matter are not inherently toxic to dogs or cats.
However, high levels of vegetable insoluble fibre may create several issues in carnivores.
1. Reduced Nutrient Digestibility
Research has shown higher insoluble fibre diets can reduce digestibility of:
- protein
- fat
- dry matter
- gross energy
A University of Illinois canine study found increasing insoluble fibre significantly increased fecal output while reducing nutrient digestibility.
This means:
more food in…
less nutrition absorbed.
2. Larger Stool Volume
One major giveaway of high-fibre processed diets:
massive stools.
Plant fibres absorb water and increase fecal bulk significantly.
Raw-fed animals commonly produce:
- smaller stools
- firmer stools
- less waste volume
This is because raw diets contain fewer indigestible plant fillers.
Fur: Nature’s Original Fibre
Unlike vegetable fibre, fur behaves differently in the digestive tract.
Fur:
- is protein-based
- has very low fermentability
- provides mechanical roughage
- contributes bulk without excessive water-binding
Many raw feeders report fur-containing prey items help:
- firm stools
- reduce sloppy stools
- improve anal gland function
- support bowel movement naturally
Wild carnivores consume fur routinely as part of whole prey feeding.
Cats especially evolved consuming:
- rodents
- birds
- fur
- feathers
- connective tissues
This is biologically normal.
Insoluble Fibre & The Microbiome
Plant fibre is often marketed as essential for the microbiome.
Reality is more nuanced.
Some fermentable fibres can help beneficial bacteria.
However:
- excessive fermentable plant material may also contribute to
- bloating
- gas
- altered stool quality
- microbiome imbalance in sensitive animals
Carnivore digestive systems evolved around animal tissue fermentation far more than heavy plant fermentation.
Balance matters.
Signs Your Dog or Cat May Be Struggling With Excess Plant Fibre
Some common signs include:
- excessive stool volume
- frequent bowel movements
- loose stools
- bloating
- flatulence
- inconsistent stools
- anal gland issues
- chronic hunger despite eating large meals
- poor coat quality
Not every animal reacts the same, but many improve dramatically when fillers are reduced and species-appropriate nutrition is prioritised.
What Should Dogs & Cats Eat Instead?
At RogueRaw, our philosophy is simple:
Feed closer to nature.
Carnivores thrive on:
- animal proteins
- raw meaty bones
- organs
- connective tissue
- cartilage
- moisture-rich foods
- species-appropriate nutrition
Not heavily processed filler-heavy diets.
Our raw feeding philosophy focuses on:
- digestibility
- nutrient density
- biological appropriateness
- lower waste output
- natural feeding instincts
Fur vs Vegetable Insoluble Fibre
| Fur (Animal Fibre) | Vegetable Insoluble Fibre |
|---|---|
| Protein-based (keratin) | Carbohydrate-based |
| Naturally found in prey animals | Derived from plants |
| Evolutionarily natural for carnivores | Less biologically typical |
| Very low fermentability | Variable fermentability |
| Usually produces smaller stools | Often produces larger stools |
| Acts as mechanical roughage | Mechanical roughage + water binding |
| Contains animal proteins & minerals | Contains plant compounds & fibres |
| Naturally present in whole prey diets | Common in kibble and plant-inclusive diets |
| Minimal water-holding capacity | Holds and absorbs water |
| Often results in firmer stools | Can increase stool bulk significantly |
Frequently Asked Questions
Is insoluble fibre bad for dogs?
Not always. Small amounts can help bowel movement and stool quality. Problems often arise when large amounts of cheap plant fillers dominate the diet.
Do dogs need vegetable fibre?
Dogs can tolerate some plant matter, but they do not have the same biological requirement for high plant fibre intake as herbivores.
Do cats need plant fibre?
Cats are obligate carnivores. Their digestive systems evolved primarily for animal tissue digestion rather than large quantities of plant fibre.
Why do raw-fed pets often produce smaller stools?
Raw diets are generally more digestible and contain fewer indigestible fillers compared to processed kibble diets.
What is prey fibre?
Prey fibre refers to natural animal-based roughage such as:
- fur
- feathers
- connective tissue
- cartilage
These are naturally consumed in whole prey feeding.
Can fibre cause anal gland problems?
Excessively soft stools may contribute to poor anal gland expression. Firmer stools often help naturally express the glands during defecation.
Why does kibble create larger stools?
Many kibbles contain significant plant fillers and insoluble fibre ingredients which increase stool bulk and waste output.
Is fur digestible?
Fur is mostly indigestible because it is made from keratin. It functions primarily as mechanical roughage rather than a nutrient source.
The Bottom Line
Dogs and cats evolved eating prey — not highly processed plant-heavy diets.
While some plant fibre can play a role in digestion, there is a major difference between:
- natural prey fibre
and - large amounts of processed vegetable insoluble fibre.
Understanding this distinction may explain why many raw-fed dogs and cats experience:
- smaller stools
- firmer stools
- improved digestion
- better body condition
- healthier coats
- reduced GI issues
Nature designed carnivores to consume animal tissue first.
Everything about their digestive system reflects it.