With a degree in biochemistry, Leah works for a small biotechnology company and enjoys writing about science.
Guinea Pig Diet
With wild ancestors native to the Andes of South America, guinea pigs (also known as “cavies”) are rodents that require large volumes of fibrous grass to naturally wear down their teeth and stimulate their digestive tract. Their digestive tract is extremely long to digest the tough grass fibers, and it is difficult for guinea pigs to extract a lot of nutrition out of their primary food source. To increase the absorption of nutrients, they will excrete a type of stool known as a caecotrope. This excreted pellet allows the pig to obtain vitamin B, fiber, and beneficial bacteria. Most grass hay has similar nutritional content, so the type of hay is not as important as ensuring a consistent supply to keep the pig’s digestive tract moving and their teeth worn down.
Hay Types for Guinea Pigs
- Timothy grass (Phleum pratense) is the most common hay used by pet owners. It is native to Europe and the Mediterranean, with a flower head that is particularly beloved by cavies. Unfortunately, the pollen produced by the flower head can be very allergenic and bothers some humans. This hay can be purchased by the bale at farm supply stores or in smaller quantities at pet stores. If purchased as a large bale, it is important to maintain a dry storage location to prevent the growth of mold and fungus.
- Orchard grass (Dactylis glomerata) is excellent for owners who are allergic to Timothy Hay and offers the same nutrition to cavies. It is native to Europe, Asia, and northern Africa. It is slightly sweeter than other grasses and is often preferred by livestock.
- Alfalfa (Medicago sativa) is technically a legume and not a grass, but is adored by cavies. It is native to South Asia. It is high in calcium content, and is not recommended as a daily food for adult guinea pigs, as it might lead to bladder stones. Pregnant and baby pigs benefit from the additional calcium in alfalfa, but this food should be phased out once the sow has delivered and/or the babies have reached six months of age.
First Cut vs. Second Cut vs. Third Cut
“Cuts” of hay are often mentioned on the labels for bags of Timothy hay, the most common grass fed to small pets. This term refers to the time the hay was cut, and the quality varies according to the cut.
Thin stem with high fiber and low protein and fat. If cut too late, this cut will be very tough.
Excellent for pets who need to lose some weight or who are constipated.
This is the “standard” hay fed to most small pets. Slightly lower in fiber and higher in fat and protein than first cut hay. Stems should be thin.
The perfect hay for healthy adult pets.
Extremely leafy and soft with a low fiber content. This cut has the highest concentration of fat and protein. It may cause constipation issues with small pets and should be fed as a treat only.
Fed as a “treat” only.
Pellets are not a replacement for hay and should always be offered as an addition to a constant supply of clean, fresh dried grass in the cavy’s habitat. Select pellets that are plain green without additional “fancy” additives. Avoid bags containing brightly colored additives and seeds—these are not nutritional for the pig. Pellets should contain 16% fiber and 20% protein, in addition to having vitamin C. Our family feeds our guinea pigs Oxbow Essentials, which is a high-quality pellet that does not contain dyes or unnecessary "filler" ingredients.
Vitamin C Needs
Like humans, cavies cannot biosynthesize their own Vitamin C. Guinea pigs require 10-15 mg of Vitamin C every day. If they do not get enough of this nutrient, they can develop a form of scurvy and die. Look for pellets fortified with this material (it may be listed as “ascorbic acid” on the ingredients list) and supply plenty of bell peppers as treats. Do not feed your guinea pig citrus fruits on a regular basis, as these are often acidic and can cause sores in the mouth.
Fruits and Vegetables for Guinea Pigs
Healthy treats include fruits and vegetables that are low in sugar content and provide nutrients (like Vitamin C) to the guinea pig. Take care when feeding these treats, as too many may cause diarrhea in your cavy. The concentration of oxalic acid must also be monitored, as some vegetables have a high concentration. Too much oxalic acid leads to bladder stones and severe health problems in guinea pigs.
All food containing calcium and phosphorus should be reviewed: the concentration of calcium should be higher than the concentration of phosphorus in any food to prevent the formation of phosphate stones.
- Parsnip is an excellent vegetable, as it has only 0.04 g/100 g oxalate. This is a food that may be provided to your pet every day.
- Corn husks are absolutely fantastic, as they are high in fiber and have very low oxalate and calcium levels. Recycle your corn husks by feeding them to your cavies and keeping them out of the trash! These may be given every day to your pigs.
- Carrots may be fed as a treat. They have 0.50 g of oxalic acid per 100 g. They also contain sugar, which can cause problems with obesity and diabetes in your pet. Carrots should be used as a treat and not fed every day.
- Green beans may be fed in moderation. They do contain calcium and phosphorous, which must be excreted, but also contain vitamin C.
- Bell pepper is one of the best treats for cavies, as the fruit provides vitamin C and does not have a high concentration of calcium. The seeds inside a bell pepper are considered “soft,” and are safe for a pig to eat.
- Cucumber may be provided occasionally, and is low in oxalate. It is a watery fruit and may cause diarrhea if given too frequently. The seeds are soft and safe for your pet to eat.
- Red leaf lettuce, butter leaf lettuce, and curly kale may be fed to your guinea pig. Iceberg Lettuce should be avoided as it is extremely low in nutrient content and may cause bloat or diarrhea. Likewise, avoid cabbage as it has the same issues as iceberg lettuce: poor nutritional quality and a propensity to cause bloat.
Read More From Pethelpful
Safe Vegetables for Guinea Pigs
Fruits and Vegetables to Avoid
Spinach, parsley, purslane, and clover contain high levels of oxalic acid and may cause bladder stones. If fed too frequently, oxalic acid can cause kidney failure in your pet. The quantity of this component, in addition to calcium content, should be monitored.
Pineapples, oranges, and many other citrus fruits should be given only rarely and with caution, as the acidity may cause mouth sores.
Dangerous and Poisonous Foods for Guinea Pigs
Your pet should never be fed bread, animal products, or any high-sugar food. Their digestive system cannot handle these food items. The wrong foods can cause injury or death to a pig—if unsure about any food item, it is better to be safe than sorry. Do not feed your pet any item you are not certain is safe.
Do not let your pet have hard seeds as they can get stuck in your pet’s teeth or in the digestive tract. Cavies might choke on large seeds, as they don’t have the right kind of teeth to break down the seed and might try to swallow it whole. Many seeds have a high fat content, which can lead to obesity in some pigs.
When allowing your cavy access to the lawn, ensure there are no poisonous weeds in the patch of grass they are exploring. The following food items are poisonous to guinea pigs and should never be allowed near your pet:
- Potatoes and sweet potatoes
- Tomato leaves
Remember a simple adage for giving your guinea pig a treat: when in doubt, leave it out! No treat is worth the risk of harming your pet, so only feed your pig foods you are certain are safe.
- Rogers, K.D., Jones, B. et. al. (2011). Composition of Uroliths in Small Domestic Animals in the United Kingdom. The Veterinary Journal, 188(2):228-30.
- Wolf, P., Seisenop, U., et. al. (2014). Hygienic Quality of Feedstuffs for Small Mammals Sent to the Consultation Service. Tierärztliche Praxis. Ausgabe K, Kleintiere/Heimtiere, 42(2):101-6.
- Okewale, P.A., Odeyemi, P.S., et. al. (1991). An Outbreak of Streptococcus Pyogenes Infection Associated with Calcium Oxalate Urolithiasis in Guinea Pigs (Cavia porcellus). Lab Animal, 25(2):184-6.
- Kawasaki, K. Min. X., & Sakaguchi, E. (2018). Effect of Fructo-Oligosaccharides on Nutrient Digestibility and Digesta Retention Time in Adult Guinea Pigs. Animal Science Journal, 89(3):547-551.
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
© 2018 Leah Lefler
Leah Lefler (author) from Western New York on November 13, 2018:
Thank you, Liz! We have two female guinea pigs we adopted two years ago and they are thriving. We always ensure they have plenty of hay and fresh vegetables. Good nutrition leads to a long life in these animals.
Liz Westwood from UK on November 13, 2018:
This is a detailed and helpful guide.