Guinea pigs should have unlimited fresh grass hay every day. Hay should make up the bulk of their diet, around 80 percent or more, because it keeps their gut moving and wears down teeth that never stop growing. Timothy hay is the standard choice for adults.
Why Hay Matters So Much
- Teeth: Guinea pig teeth grow continuously. Chewing long, fibrous stems grinds them down and helps prevent painful overgrowth.
- Digestion: Fiber keeps food moving through the gut. Too little can lead to GI stasis, a serious emergency.
- Enrichment: Foraging and burrowing in hay gives them something to do all day.
The Best Types of Hay
Timothy Hay
The go-to option for adult guinea pigs. It is high in fiber and moderate in protein and calcium. First cut is the stemmiest and best for teeth, second cut is softer and leafier, and many owners mix the two.
Orchard Grass
Soft, sweet-smelling, and a good alternative for pigs that are picky or sensitive to timothy. Our guide to orchard grass hay for guinea pigs covers it in more detail.
Meadow and Botanical Hays
Mixed grass hays that add variety. Good for rotating flavors, as long as they are fresh and free of dust or mold.
Alfalfa Hay
Alfalfa is a legume, higher in protein and calcium. It can suit growing babies, pregnant or nursing sows, but is generally too rich for healthy adults and is not a daily staple for them.
How to Pick Good Hay
- Green to golden in color, with a fresh grassy smell.
- Long stems, not mostly crumbs or dust.
- No mold, dampness, or musty odor, and no bits of plastic or other plants.
- Store it in a dry, ventilated spot, not a sealed bag in a hot room.
How Much to Offer
Offer a pile at least as big as your guinea pig’s body, refilled whenever it runs low. A hay rack or a corner of the cage works well. Avoid small metal feeder balls where a pig could get stuck. Pair hay with a measured amount of plain pellets and fresh vegetables, as described in What Do Guinea Pigs Eat? and Best Vegetables for Guinea Pigs.
Bottom Line
Keep fresh timothy or orchard grass hay in front of your guinea pig at all times. If your pig suddenly eats less hay or stops eating, see our post on why a guinea pig isn’t eating and call an exotics vet right away.
This article is general information, not veterinary advice. Ask your vet about your guinea pig’s diet and any health concerns.
