Grasses are the primary staple in a guinea pig’s diet. They meet most of the needs of the rodent known scientifically as cavia porcellus. But there are a number of supplemental foods that can help supply missing nutrients and liven up their diet.
Foraging is one way to accomplish that, but it requires some care. There are a number of wild plants that are safe for cavies. Dandelions are a favorite, but are better when they’re relatively immature. Plantains are safe and white clover will be appreciated, just as it is for rabbits. Clover is rich in calcium, phosphorus and magnesium that guinea pigs need. Yarrow is fine, as are chickweeds.
But there is a variety of plants that are toxic, such as buttercups. So, unless you have a good eye for what is what, it may be best to avoid foraging until after your research is advanced.
If you feed raw grasses, foraged or not, rather than pellets, cavies will do better with young, fresh material. Green, leafy hay is much preferred to the stemmy parts. It’s important to ensure that nothing fed is contaminated with mold or mildew. Just as with humans or most other mammals, fresh food is far healthier for guinea pigs than that which is approaching spoiled. Guinea pigs are not scavengers and they don’t have robust digestive systems.
Vegetables make for excellent supplements, where the leafy greens are best. Avoid cruciferous vegetables, which may produce gas in the digestive tract. Instead, go for the turnip greens, kale or parsley. Cavies have less capacity for tolerating pesticides and levels that are fine for humans may be toxic to them. Ensure that any vegetables were grown with ultra-low quantities.
A wide array of fruits are tasty and nutritious. Small chunks of apricots and bananas, or even oranges, are fine. Avoid potatoes, which have too much starch and may contain harmful levels of oxalic acid from the skin and eyes of the tuber. Grapes are good in small quantities, no more than one or two per day. Some cavies like tomatoes and small chunks are fine in moderation.
Introduce new vegetables or fruits in small quantities and one at a time to make it easier to judge your guinea pig’s reaction to changes in diet. Though they have commonalities, each pig is an individual and may (and probably will) react differently.
A guinea pig’s back teeth grow continuously. Allowing them an ample supply of grasses and vegetables promotes not only good nutrition but good dental health. As they graze, the teeth are ground gently down in a gradual process that keeps them at the right length.
A final tip: properly stored, a bale of hay may be kept fresh and provide enough food to last for months. That’s an inexpensive way to give your cavy protein and other compounds to satisfy its dietary needs. Some hay may also be used as bedding, but take care to monitor their intake. Overeating and obesity are possible.