Can Guinea Pigs Eat Grass? Vet-Reviewed Nutrition Facts & FAQ

Guinea pigs are some of the most popular small mammals to keep as pets, and it’s not hard to see why. They’re cute, friendly, and social compared to many rodents, and they’re relatively hardy and adaptable too. When it comes to feeding your guinea pig, the right diet can be a little confusing. After all, they can eat so many different things that knowing how to build a balanced guinea pig diet can seem intimidating.

But when it comes to grass, the answer is easy—every guinea pig should have a diet with hay or grass in it. In fact, most of what guinea pigs eat is grass. But don’t start saving your lawn clippings—it’s important to make sure the grass your guinea pig is getting is clean and not contaminated.

Why Guinea Pigs Need Hay & Grass

If you want to feed your guinea pig a balanced diet, it’s about more than just getting the right nutrients in. That’s because the guinea pig’s digestive system requires continuous movement. If your guinea pig stops eating, it will enter a life-threatening gastrointestinal stasis long before it starves to death. That means that guinea pigs are nibblers that need to have something always available—and grass and hay are the best choices. (Hay is made of dried grass grown to feed animals.)

Guinea pigs are built to eat tough, dry grasses in the Andes mountains of South America as their primary food. They have a unique set of gut bacteria that helps them break down much tougher food than we can eat. That means that grass serves two purposes in a guinea pig diet. First, it keeps the digestive system moving and prevents GI stasis. Second, it provides a lot of nutritional value to guinea pigs.

Letting Your Guinea Pigs Graze

Most guinea pig owners rely on hay, or dried grasses, for most of their guinea pig’s food. Hay is a healthy, nutritious choice for guinea pigs, and your guinea pig doesn’t need any fresh grass in its diet to meet its nutrition requirements. But say you want to save a little money on hay and you already have a big lawn. Is it okay to supplement your guinea pig’s food by letting it eat some of the grass you already have? It depends.

Guinea pigs can eat grass from your yard, but it’s important to make sure that your grass is safe for guinea pigs. You’ll want to avoid grass with a lot of alfalfa and clover in it—these both have enough calcium to make guinea pigs sick if they eat too much of it regularly. You also shouldn’t feed your guinea pig grass if you use pesticides in your yard or anything else that might poison your pig. Finally, you should make sure that your yard is safe for grazing—you don’t want your guinea pig escaping your yard and getting lost. It’s also generally safest to only let your guinea pig outside during the day; night (including the hours right around dawn and dusk) is prime hunting time for predators.

It is recommended to gradually build up the time that your guinea pig spends each day out in their run on the grass. This is particularly important if they have been kept indoors all winter and now you want to put them out on the spring grass. The high water and carbohydrate content of spring grass can easily result in diarrhea and gastrointestinal distress such as bloat. Start with around 5 minutes twice a day and then increase gradually.

The Problem With Lawnmower Clippings

If your yard isn’t suitable for free-range guinea pigs, you might be tempted to bring in your lawnmower clippings instead. However, that’s not recommended. Lawnmowers can be very messy in their trimming, mixing roots and dirt in with the rest of the grass. They also can get exhaust, grease, or other contaminants into the grass. It’s better to be safe than sorry.

Other Parts of a Healthy Guinea Diet

Guinea pigs eat a lot of grass, but they need other food too. You should include a mix of fresh veggies and high-quality guinea pig pellets in your guinea pig’s diet, along with unlimited fresh water. Be extra sure to include vitamin C sources in your guinea pig’s food, as they can’t produce their own. The general guideline is that the diet of a guinea pig should consist of 85% Hay/grass, a cup of mixed vegetables and a tablespoon of guinea pig pellets.

Last Thoughts

After looking at all the details, it’s clear that, yes, guinea pigs can and should have grass in their diet, but you have to be careful with the source. Lawnmower clippings, grass with pesticides, and certain types of grass like alfalfa aren’t the best choices for guinea pigs. However, many guinea pig owners can happily let their pigs graze as an alternative or addition to fresh hay.