Guinea pigs are popular pets in the UK, with an estimated 400,000 kept in UK households. As their popularity as pets in the UK increases it is vital that we talk about the differences between Guinea pigs and our other pets, so that we can look after them properly and provide them with all the tools they need to live a happy and healthy life. 

What are Guinea pigs? 

Guinea pigs are rodents, part of the Caviidae family. They are small furry mammals, weighing around 1kg, with different breeds having different coat coloration and length, with some even having no fur at all! They have one of the most unique and amazing digestive systems of all mammals which is designed specifically for guinea pigs to survive in their native environment of the Andes in South America, where the species first originated.  

What is so special about Guinea pigs’ digestive systems? 

Guinea pigs have specialised digestive systems that allow them to take low value food and turn it into energy and nutrition to fuel them.  

The digestive system starts in the mouth with their narrow oral cavity and jaws which contain continuously growing teeth. They have large incisors for gnawing and cutting and then rely on their molars to chew and grind down fibrous materials such as long strands of grass which contain lots of cellulose and is typically challenging for most simple stomached mammals to digest. 

Guinea pigs rely on the grinding action of their molar teeth to break down these harsh plant materials before they enter their stomach and intestines. The teeth continuously grow to allow for the wear that they receive by grinding down harsh materials constantly. As Guinea pigs are grazing animals they eat continuously other than when they are sleeping, so the teeth are constantly in wear.  

Once the plant material has been chewed up enough it enters the oesophagus of the Guinea pig and moves down into their stomach and intestines before it enters their large intestine. Guinea pigs have a very large caecum which is specifically designed to continue to break down the fibrous plant material into nutrients that the Guinea pig can absorb and use for growth and energy. The caecum contains thousands of microbes (bacteria) that are specifically designed to digest fibrous plant material. Without these microbes the Guinea pig cannot break down the foodstuff and will be unable to get useful nutrients from it. 

Finally, Guinea pigs excrete their waste products the same as other mammals in the form of faecal pellets, however they also produce caecotrophs, which are nutrient packed balls of digested fibrous material that the Guinea pig will excrete and then ingest (in a similar way to rabbits). This means they can now absorb the nutrients that were locked inside the fibrous material through the stomach and intestines like other mammals – incredible! 

It’s always important to note when discussing Guinea pigs’ digestive systems that one of the nutrients that Guinea pigs are unable to synthesise is Vitamin C. As a result, it is vitally important that Guinea pigs receive a vitamin C supplement in their diet to ensure they don’t end up with a deficiency. Supplements and fortified foodstuffs are available over the counter in most pet stores, but please speak to your veterinary surgeon if you have any specific concerns or queries about this.  

So why do Guinea pigs need fibre? 

As you can see from the above, Guinea pigs’ digestive systems are built on the assumption that they are going to ingest lots and lots of fibrous plant material. If a Guinea pig does not receive this high amount of fibre in their diet then their digestive systems stop working properly which can be catastrophic for the Guinea pig. 

What should I feed my Guinea pig to ensure they have enough fibre in their diet? 

Guinea pigs should always have access to a good quality grass or grass hay, such as Timothy hay, at all times. This should never run out, and they should be able to eat as much as they need as it makes up 85-90% of their diet. Fresh grass, dandelions and leafy greens are also good sources of fibre. You can read more about feeding guinea pigs here. 

What happens if Guinea pigs don’t get enough fibre? 

If Guinea pigs don’t get enough fibre then their digestive systems stop working in the way that they should. This can present in many ways including: 

Overgrowth of their teeth  

As their teeth continually grow, if they are not being worn down appropriately by fibrous material then they will overgrow and cause pain and discomfort  

Bloat  

This can be a life-threatening condition in guinea pigs where the abdomen distends with gas. It can occur secondary to gastrointestinal stasis where the whole system has slowed down due to inadequate fibre or other factors. It has also been reported in cases where guinea pigs have eaten inappropriate foodstuffs which have caused excessive gas production. 

Diarrhoea 

This can occur as a result of dysbiosis, a dangerous condition where the microbes in the caecum become disrupted. This can occur as a result of dietary changes including not enough fibre. Other causes include stress and inappropriate antibiotic use. 

Gastrointestinal stasis  

This is a very dangerous symptom where digested material in a Guinea pig’s digestive tract slows down or stops moving because the digesting organs have stopped working/slowed down. As a result, the Guinea pig can stop producing faeces, become very painful with abdominal discomfort and less interested in their food. If this condition is not addressed quickly it can be fatal. 

Risk factors for gastrointestinal stasis can include: 

  • low fibre diet 
  • dental disease 
  • Pain 
  • Stress 
  • reduced water or food intake 
  • change in diet 
  • environmental changes 
  • Anaesthesia 
  • other underlying health issue etc.  

The list above is not complete and shows how many things can impact a Guinea pig’s digestion.  

Symptoms of GI stasis in a Guinea pig include: 

  • teeth grinding 
  • reduced appetite 
  • Quiet/withdrawn 
  • vocalisations  
  • reduced faecal output 
  • Bloat 

If you suspect your Guinea pig may have gastrointestinal stasis it is important they are seen by a veterinary surgeon for assessment without delay. GI stasis can rapidly become a life-threatening disease process, and it is important your Guinea pig is assessed as soon as possible so treatment can be initiated. 

Treatment and management options for gastrointestinal stasis vary and are often dependent on what the underlying cause of the symptom is 

For example, if dental disease is the cause then addressing the underlying dental issue will be needed. Before the underlying issue is addressed however your Guinea pig will need to be stabilised with fluids and supportive nutritional care which often involves support feeding. They will be given a range of pain relief and supportive medicines to help encourage their digestive system to start moving again. As part of this process your veterinary surgeon may undertake additional diagnostic tests which may include diagnostic imaging (radiographs, ultrasound, CT), blood tests, full clinical exam including auscultation of the chest and abdomen and urinalysis if necessary. 

Summary: 

  • Guinea pigs have a unique anatomy with a particularly amazing gastrointestinal system 
  • Guinea pigs GI tracts are specifically adapted for high fibre diets 
  • Essential sources of fibre in Guinea pig diets include grass and grass hay and they should have access to this at all times 
  • If Guinea pigs do not get enough fibre in their diet they are susceptible to a number of harmful conditions including gastrointestinal stasis, bloat, dysbiosis and dental disease 
  • If you suspect your Guinea pig may have any of these conditions it is important they are assessed by a veterinary surgeon without delay