Guinea pigs, also known as cavies, are herbivores and natural grazing animals. In the wild, they spend much of their time eating grasses and other fibrous plant material. A healthy guinea pig diet should reflect these natural feeding habits, with unlimited good-quality grass hay forming the foundation of their diet, supported by fresh grass, a variety of vegetables and leafy greens, and a small amount of suitable guinea-pig-specific food.
Providing the right diet is one of the most important things you can do to keep your guinea pig healthy. A high-fibre diet helps support normal digestion, encourages natural tooth wear and provides the nutrients guinea pigs need to maintain good health.
Grass and Natural Grazing
Guinea pigs are grazing animals and naturally spend many hours each day eating. Fresh grass can be an excellent food for guinea pigs and can provide enrichment and exercise when they are allowed to graze safely.
A secure outdoor run or movable lawn enclosure can give guinea pigs access to fresh grass while allowing them to exercise and behave naturally. However, outdoor grazing must always be carefully managed.
Never allow guinea pigs to graze in an area where poisonous plants or weeds may be present. It is important not to rely on a guinea pig's ability to recognise poisonous plants. Guinea pigs may eat plants that are harmful to them, particularly if other food is limited.
Before allowing your guinea pigs onto a lawn or garden area, make sure you know what plants are growing there and that they are safe for guinea pigs.
The grass must also be free from pesticides, herbicides, fertilisers and other chemicals. Recently treated lawns should not be used for grazing.
Lawn clippings should never be fed to guinea pigs. Once grass has been cut, it can heat and ferment rapidly and may cause serious digestive problems.
If your guinea pig is not accustomed to eating fresh grass, introduce it gradually rather than suddenly providing a large amount. This gives the digestive system time to adjust.
Hay: The Foundation of a Guinea Pig's Diet
Good-quality grass hay is one of the most important foods you can provide for a guinea pig and should be available at all times, day and night.
Hay is essential because guinea pigs require a very high-fibre diet. The fibre helps keep the digestive system moving normally and supports the healthy bacteria in the gut.
The constant chewing required to eat hay is also important for dental health. Guinea pigs' teeth grow continuously throughout their lives, so they need plenty of fibrous food to encourage natural tooth wear.
Suitable types of grass hay include:
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Timothy hay
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Oaten hay
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Meadow hay
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Pasture or other good-quality grass hays
Hay should be clean, dry and free from mould. Avoid hay that is damp, musty or contaminated.
Lucerne, also known as alfalfa, is higher in protein and calcium than grass hay. It can be useful for young, growing guinea pigs and pregnant or nursing females, but it is generally not necessary as the main hay for healthy adult guinea pigs.
Fresh Vegetables and Leafy Greens
Fresh vegetables and leafy greens should form an important part of a guinea pig's daily diet. They provide moisture, fibre and a range of vitamins and minerals.
Offering a variety of vegetables is better than relying on a single food. Different vegetables provide different nutrients, and variety also makes mealtimes more interesting.
Suitable vegetables and greens include:
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Capsicum (bell pepper)
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Cos or romaine lettuce
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Cucumber
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Celery
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Broccoli
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Coriander/cilantro
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Parsley, in moderation
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Carrot, in small amounts
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Fresh grass
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Other known-safe leafy greens and herbs
Capsicum is particularly useful because it is naturally high in vitamin C.
New foods should always be introduced gradually. A sudden change in diet can cause digestive upset.
Some vegetables are higher in calcium, sugar or other nutrients than others, so variety and moderation are important. There is no need to feed enormous quantities of any single vegetable.
Fruit Should Be a Treat
Fruit can be enjoyed by guinea pigs, but it should be considered an occasional treat rather than an important part of their diet.
Fruit contains natural sugars, and too much can contribute to an unbalanced diet and weight gain.
Small portions of suitable fruit can include:
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Apple, with the seeds removed
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Pear
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Strawberry
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Blueberry
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Melon
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Small amounts of banana
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Small amounts of orange or other suitable citrus fruit
Fruit should be offered in small quantities and only occasionally.
When offering fruit with stones or pits, such as stone fruit, the stone must be completely removed. Guinea pigs should never be allowed to chew or swallow fruit stones or potentially harmful seeds.
Herbs and Wild Plants
Many guinea pigs enjoy fresh herbs and suitable wild plants. These can provide variety and enrichment as part of a balanced diet.
Examples of plants that may be suitable include certain types of plantain and dandelion, provided they have been positively identified and are free from chemicals, pesticides, animal faeces and other contaminants.
Parsley can also be offered, but like some other leafy greens, it should be fed as part of a varied diet rather than in large quantities every day.
Do not feed a wild plant simply because it looks familiar. Some poisonous plants can resemble edible species. If you are unsure about the identity or safety of a plant, do not give it to your guinea pig.
Guinea-Pig Pellets
Contrary to some older guinea-pig feeding advice, it is not necessary to completely avoid pellets.
A small, measured amount of good-quality guinea-pig-specific pellets can be included in the diet. Choose a food specifically formulated for guinea pigs and preferably one that is high in fibre and fortified with stabilised vitamin C.
Pellets should supplement the diet rather than replace hay, grass and fresh vegetables.
Avoid muesli-style mixes that contain a mixture of grains, seeds, nuts, dried fruit and sugary ingredients. These mixes can encourage selective feeding, allowing guinea pigs to pick out their favourite ingredients while leaving the more nutritious components.
Avoid feeding guinea pigs foods such as:
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Sunflower seeds
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Nuts
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Cracked corn
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Grain mixes
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Sugary cereals
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Muesli-style pet foods
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Foods containing excessive added sugar or molasses
Guinea pigs are herbivores and do not need seeds, nuts or grain-based treats.
Vitamin C: An Essential Nutrient
One of the most important differences between guinea pigs and many other mammals is that guinea pigs cannot produce their own vitamin C.
They therefore need a reliable dietary source of vitamin C every day.
Fresh vegetables, particularly capsicum, can provide vitamin C. A good-quality guinea-pig-specific pellet should also contain a reliable source of vitamin C.
Vitamin C supplements may be appropriate in some circumstances, particularly when recommended by a veterinarian. However, vitamin C should not routinely be added to a guinea pig's drinking water.
Vitamin C can break down in water, particularly when exposed to light and heat, and changing the taste of the water may cause some guinea pigs to drink less.
If a guinea pig is ill, recovering from illness, pregnant, nursing, or unable to eat an appropriate diet, veterinary advice should be obtained regarding its vitamin C requirements.
Foods That Guinea Pigs Should Not Eat
Guinea pigs have sensitive digestive systems and should not be given many of the foods commonly eaten by people.
Avoid feeding:
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Chocolate
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Caffeine
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Alcohol
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Onions
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Garlic
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Avocado
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Potato and potato plants
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Rhubarb
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Meat or animal products
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Nuts
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Sunflower seeds
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Grain and cereal mixes
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Cracked corn
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Sugary cereals
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Sweets and confectionery
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Muesli-style pet foods
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Foods containing excessive added sugar or molasses
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Lawn clippings
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Any plant that has not been positively identified as safe
When in doubt about a particular food or plant, it is safest not to feed it until its safety has been confirmed by a reliable veterinary or animal-care source.
Guinea Pig Teeth
Guinea pigs' teeth grow continuously throughout their lives. This makes a high-fibre diet particularly important.
The best way to support natural tooth wear is to provide unlimited grass hay and plenty of appropriate fibrous foods that require chewing.
Dental problems can develop even when a guinea pig has access to hay. Some guinea pigs develop abnormal tooth growth or problems affecting the back teeth and tooth roots.
Signs of possible dental disease include:
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Difficulty eating
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Dropping food
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Eating less than usual
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Losing weight
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Drooling
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A wet chin
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Difficulty chewing
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Swelling around the face or jaw
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Changes in the type or amount of food being eaten
If any of these signs are noticed, a veterinarian should examine the guinea pig.
Do not attempt to cut or trim a guinea pig's teeth yourself. Dental disease can be more complicated than simply having teeth that appear too long.
Housing and Outdoor Areas
Good nutrition is only one part of keeping guinea pigs healthy. They also need suitable housing, exercise, companionship and protection from extreme weather.
Their accommodation should provide a clean, dry and secure environment with:
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A comfortable sleeping area
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Protection from rain and wind
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Shade from direct sunlight
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Good ventilation
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Safe hiding places
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Appropriate bedding
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Plenty of room for movement and exercise
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Protection from predators
Guinea pigs are particularly vulnerable to heat stress. During hot weather, they must have access to shade and a cool, well-ventilated environment.
Outdoor runs must be securely enclosed to prevent escape and protect guinea pigs from cats, dogs, foxes, birds of prey and other predators.
Any grass or plants accessible to guinea pigs must be safe and free from chemicals.
Keeping the Enclosure Clean
Guinea pig housing should be cleaned regularly to keep the environment dry and hygienic.
Remove wet or soiled bedding, excess droppings and uneaten fresh food as necessary.
Fresh vegetables and fruit should not be left in the enclosure long enough to spoil. Spoiled food can attract flies and other pests and may contribute to illness.
Food bowls, hay containers and water bottles should also be cleaned regularly.
A clean environment is particularly important because guinea pigs spend a great deal of time close to the ground and can easily come into contact with contaminated bedding or food.
Fresh Water
Fresh, clean drinking water must be available at all times.
Water should be changed regularly, and bottles or bowls should be cleaned frequently.
Both bottles and suitable heavy bowls can be used, provided the guinea pig can easily access the water and the container is kept clean.
There is no need to provide special or mineral-free water unless specifically recommended by a veterinarian. The most important thing is that the water is clean, fresh and readily available.
Monitor your guinea pig's normal drinking habits. A sudden increase or decrease in drinking can sometimes indicate a health problem.
Guinea pigs can become dehydrated quickly if they cannot access water, particularly during hot weather or when they are unwell.
A Simple Daily Diet
For a healthy adult guinea pig, the diet can be kept relatively simple.
The foundation should be:
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Unlimited good-quality grass hay
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Fresh grass, where safely available
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A daily variety of vegetables and leafy greens
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A small measured amount of quality guinea-pig-specific pellets
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A reliable daily source of vitamin C
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Small amounts of fruit occasionally as a treat
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Fresh, clean water available at all times
The majority of the diet should be made up of high-fibre foods, particularly hay and grass.
Special Dietary Requirements
Not every guinea pig has exactly the same nutritional needs.
Young, growing guinea pigs have different requirements from healthy adults. Pregnant and nursing females also need additional nutritional support. Older or unwell guinea pigs may require dietary adjustments depending on their health.
Lucerne/alfalfa can be useful for young, growing guinea pigs and pregnant or nursing females because of its higher protein and calcium content, but it is generally not required as the primary hay for healthy adults.
If your guinea pig has a medical condition, is losing weight, has stopped eating, or has difficulty chewing, speak to a veterinarian before making significant dietary changes.
Monitoring Your Guinea Pig's Health
Getting to know your guinea pig's normal eating and toileting habits is an important part of responsible care.
Regularly monitor:
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Appetite
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Body weight
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Water consumption
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Dropping size and quantity
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Teeth and chewing
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Eyes and nose
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Coat and skin
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Feet
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Activity levels
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General behaviour
A guinea pig that stops eating, produces significantly fewer droppings, loses weight or shows difficulty eating should receive veterinary attention promptly.
Guinea pigs can become seriously ill quite quickly when they stop eating, so changes in appetite should never be ignored.
The Bottom Line
A healthy guinea pig diet does not need to be complicated. The most important thing is to provide a high-fibre diet based on unlimited grass hay, with fresh grass and a variety of suitable vegetables and leafy greens.
A small amount of good-quality guinea-pig-specific food can complement the diet, while fruit should be reserved for occasional treats.
Guinea pigs also need a dependable source of vitamin C, fresh drinking water, safe opportunities for grazing and plenty of opportunities to chew and exercise.
Avoid seeds, nuts, grains, sugary foods, lawn clippings and any plant that has not been confirmed as safe.
With the right diet, clean and secure housing, appropriate exercise and regular monitoring, you can help your guinea pig maintain healthy digestion, good dental health and a happy, active life.