Nutrition-related health issues are one of the most common reasons for rabbits to be brought to the vets and many of them stem from inadequate supply of dietary fibre. While most owners will already know that rabbits need hay in their diet, fewer understand just why fibre is so critical or how profoundly it can affect a rabbit’s overall health. Rabbits are unique herbivores with a complex and sensitive gastrointestinal tract that is reliant on constant movement, fermentation and selective digestion to stay healthy.  

Not providing enough fibre is not just an oversight, it’s a major cause of multiple rabbit health problems. Here we’ll explore the role of fibre in depth, including how it affects multiple body systems and how you can keep your rabbit’s diet carefully balanced. 

Understanding a rabbit’s digestive system  

Rabbits are hindgut fermenters, meaning they rely on the lower part of their digestive system (particularly the large intestine and caecum) to break down fibrous plant matter. Rabbits consume a diet largely made up of indigestible structural carbohydrates, namely cellulose, hemicellulose and lignin.  These materials are difficult or impossible for mammals to digest, and rabbits depend on the complex microbial community in their caecum to ferment these fibres and extract nutrients from it.  

To maintain this delicate ecosystem, rabbits must consume fibre almost continuously. Their digestive system is built to be in near-constant motion and long pauses in eating can lead to dangerous gastrointestinal stasis.  

Indigestible fibre 

Cellulose is one of the main components of plant cells walls. Just like humans, rabbits can’t produce the enzymes needed to break this down on their own. However, unlike us humans, rabbits need cellulose-rich foods to survive.  

Indigestible fibre (also called insoluble fibre) performs several important functions including: 

  • Stimulating gut motility: indigestible fibre provides bulk that triggers movement of the intestines (peristalsis) 
  • Preventing impaction and stasis: without enough fibre moving through the system, the gut slows down which causes water to be reabsorbed excessively, resulting in dry and impacted contents 
  • Regulating stomach emptying: fibre ensures that the stomach is emptied regularly, contributing to steady flow of the GI tract 
  • Helping to maintain a healthy caecal environment  

So, although rabbits can’t directly digest cellulose, it is still essential to the regular upkeep of their complex gastrointestinal tract.  

Rabbits in the wild will spend the majority of their waking hours grazing, meaning fibre keeps the digestive tract moving continuously.  

As well as being key to gastrointestinal movement, high-fibre foods can also help prevent weight gain and obesity in rabbits. Indigestible fibre can provide a sense of fullness, adds bulk without calories and encourages more regular grazing rather than overeating concentrated foods. You might notice that rabbits fed more pellets and less fibre are often prone to weight gain and gut stasis. 

Gastrointestinal stasis 

Gastrointestinal stasis (also known as ‘gut stasis’ or simply ‘stasis’) is one of the most common medical conditions seen in pet rabbits. It occurs when the gut slows down or stops moving entirely. Low fibre is one of the most common primary causes of this.  

Symptoms include: 

  • Small or absent droppings 
  • Reduced appetite  
  • Lethargy 
  • Bloating 
  • Teeth grinding (a sign of pain) 

Gut stasis is a veterinary emergency and often requires substantial treatment. Rabbits may have recurrent episodes, so it’s vital to be aware of the signs to look out for. One of the simplest and most effective ways to reduce your rabbit’s risk of gut stasis is to provide them with daily access to high-quality hay ad-lib (as much as they want).  

Digestible fibre and fermentation 

Not all fibre is indigestible. Digestible fibre (also known as soluble fibre) plays a different but equally vital role in rabbit digestion.  

Rabbits have a large caecum, which is a specialised fermentation chamber involved in digestion, that is filled with beneficial microorganisms. These microbes break down digestible fibres into volatile fatty acids (VFAs). These VFAs are essential for several reasons including energy production, caecal health and maintaining pH. Even though rabbits eat a lot of low-energy foods, fermentation helps them to compensate by extracting additional nutrients.  

Caecotrophy: recycling nutrients  

Another vital (but often misunderstood) aspect of rabbit digestion is caecotrophy: the consumption of special soft droppings called caecotrophs. If you’ve ever owned a rabbit, you might have noticed them as the softer type of poos, usually seen stuck around their bottom. These caecotrophs are actually formed in the caecum and contain a mixture of VFAs, amino acids, vitamins and beneficial bacteria. Rabbits will eat them directly from their bottom, allowing them to reabsorb nutrients that would otherwise have been lost. A fibre-rich diet ensures that the caecum produces healthy caecotrophs in the correct quantity. 

If fibre is lacking, the balance between hard faecal pellets and caecotrophs becomes disrupted. You might notice uneaten caecotrophs or soft, sticky droppings as signs that your rabbit’s diet isn’t the right fit for them. 

Fibre and dental health  

A rabbit’s teeth grow continuously throughout their life and high-fibre foods like coarse hay provide mechanical abrasion needed to wear them down naturally. Without this fibre, teeth can overgrow or develop sharp points which as you can imagine, can be very uncomfortable and painful for the rabbit. This can lead to painful cuts or ulcers in the mouth, resulting in eating becoming painful and eventually reducing their food intake which can then lead to the aforementioned gut stasis.  

How much fibre should my rabbit eat? 

Rabbit should consume a diet largely made up of unlimited hay which is accessible at all times. Small amounts (small handfuls) of fresh leafy greens can be added as well as a limited, small amount of high-quality food pellets. High-fibre foods should always make up the majority of the diet. Treats and high-carbohydrate foods like fruits, commercial treats and grains should be fed sparingly or avoided altogether. Always check your rabbit’s pre-packaged pellets for the most accurate feeding instructions as dietary content can vary hugely between foods.  

How do I know if my rabbit isn’t getting enough fibre? 

There are a few tell-tale signs that your rabbit may not be getting enough fibre. Faeces are often the best indicator of gut health but monitoring your rabbit’s appetite and food intake is helpful too. You should look out for: 

  • Reduced droppings or very small faecal pellets 
  • Soft, messy droppings that stick to the fur  
  • Decreased appetite or selective eating (only eating a certain type of food and leaving others) 
  • Unexpected weight gain or weight loss 
  • Bloating 
  • Lethargy 
  • Overgrown teeth or signs of oral pain (dropping food or food packing in their mouth) 

Any rabbit showing these signs should be taken to a vet promptly as many digestive issues can progress quickly. 

How to increase fibre in your rabbit’s diet 

Worried about making sure your rabbit is eating enough fibre? Some practical tips for increasing fibre are: 

  • Offer multiple types of hay – this can encourage interest 
  • Replace hay daily – you wouldn’t enjoy eating stale food and neither will your bunny 
  • Use hay racks or stuff hay into toys to stimulate foraging  
  • Avoid foods that encourage selective feeding (like muesli) 
  • Introduce any new types of hay or other foods gradually  

It’s plain to see that fibre is not just an optional part of a rabbit’s diet, it’s the foundation of their entire digestive, metabolic and dental health. Indigestible fibre keeps the gut moving and helps prevent life-threatening stasis. Digestible fibre is another cornerstone, supporting fermentation and generating VFAs essential for energy and gut function. Together, these fibres ensure proper peristalsis, stable caecal bacteria, healthy teeth and overall wellbeing.  

The single best way to support your rabbit’s long-term health is to supply unlimited, high-quality hay every single day. A fibre-rich diet compliments the physiology of the rabbit and gives your companion the best chance of a long, healthy and happy life.