Hay is the primary food source for pet guinea pigs, making up more than 90% of their daily diet. Hay provides the bulk of their fiber, protein, energy, vitamins, and minerals.
Guinea pigs are hindgut fermenters, and they're biologically designed to graze and consume large amounts of grass. Most owners, however, do not have access to fresh pastures 365 days a year—and that's where hay comes in. Hay is grass that's been dried and preserved to maximize its nutrition for animals.
Unlimited access
Hay should be provided in large piles scattered across the cage floor to encourage natural grazing behavior. Constant and easy access to hay is vital to maintain healthy gut motility and wear down their continually growing teeth.
Hay should never be rationed or restricted. Running out of hay, even for a short period, puts your guinea pigs at risk of fatal gastric stasis and dental disease. Always ensure their hay piles are replenished before they run completely empty.
We do not recommend using hay racks, mangers, wire balls or any other device that restricts easy access to hay. These accessories make it difficult for guinea pigs to thrive, and force them to eat in an unnatural and uncomfortable position. Sick or weak guinea pigs may avoid eating from these devices entirely. Plus, many hay rack designs pose serious safety hazards and are capable of trapping or suffocating a guinea pig. Your pets will be significantly happier and safer with hay freely available right on the cage floor.
Common types
Guinea pigs will thrive eating hay from any true grass species. Feel free to mix-and-match for variety. Some recommended types of hay are:
- Timothy hay
- Orchard grass
- Bermuda grass
- Kentucky blue grass
- Oat hay
- Meadow hay
Cuttings
Each type of hay also comes in a variety of cuts. The cutting designates what time of year the plant was harvested, and denotes its general quality:
- 1st cutting is the grass that was clipped just after winter. It's the most hard and stalky of any cutting. It has the least nutrition, although it can be good chewing material for guinea pigs with dental disease.
- 2nd cutting is harvested mid-season. This hay is nutrient-rich, and much softer than first cutting. Most guinea pig owners typically regard second cutting as “the best.”
- 3rd cutting is harvested just before the end of the growing season. It is the softest hay, but may have slightly less viable nutrition than second cutting.
Hay quality
When it comes to your guinea pigs health, selecting the right hay is one of the most important daily decision you will make, as it forms the cornerstone of their entire diet and wellness.
- Freshness & Color: Look for hay bales that are a luscious green color, as that indicates greater freshness and higher nutritional value.
- Texture: Check how the hay feels by giving it a gentle pat or slap; it should be soft to the touch and not poke or hurt your hand. If it feels prickly enough to hurt you, it will hurt your guinea pigs too.
- Safety: Ensure the hay is 100% sun-cured (dried naturally). Chemical drying agents that may be used for cattle and livestock hays are not safe for guinea pigs.
- Sourcing: Farm stores and local farmers offer the best value (around $5-10 per 50lbs bale) but quality hay can also be found in pet shops or online.
Hay hazards
Hay is a simple food, but not all hay is created equal. Knowing what to look for—and what to avoid—can help ensure your pets always have access to fresh, safe, and nutritious hay.
Straw: Straw is the dried stalk left over after a cereal grain (like wheat, oat, or barley) has been harvested. Unlike hay, it's not grown or cut for nutritional value—it's a low-nutrient byproduct.
Alfalfa: Alfalfa (sometimes called lucerne) is a legume, not a grass, and it's not suitable for adult guinea pigs older than 6 months due to a high oxalate content that's known to cause bladder stones. However, it can beneficial for growing young and pregnant/lactating females which require more calcium and protein in their diets.
Clover: Like alfalfa, clover is a legume and shares many of the same problems—high calcium and protein content that can contribute to bladder stones.
Stalky hay: Overly mature, woody hay (extreme 1st cutting) can be too harsh for regular feeding. It increases the risk of mouth and eye injuries and may deter picky eaters. A little stalky hay is fine for dental wear, but it shouldn't be the bulk of the diet.
Dusty hay: Dust is usually a sign of poor harvesting, drying or storage conditions. Dusty hay can trigger respiratory irritation, sneezing, and eye problems in guinea pigs. Always check a handful of hay before offering it—give it a light shake and see if a lot of dust comes off.
Moldy or musty hay: Do not feed your guinea pigs wet or damp hay, or hay that has a musty odor. Moisture causes mold and fungus to grow, even if you cannot see it. If any part of the bale is damp or has mold, you must throw the entire bale away. Mold spores and contamination spread through the whole bale.
Not providing enough hay: Guinea pigs can technically survive short periods eating wood shavings and paper bedding—much like how they were kept back in the 1970s—but this is far from ideal. Without a constant supply of proper hay, they will not thrive nor reach their full life expectancy.
Hay racks: As covered above, anything that restricts free access to hay or forces guinea pigs into unnatural eating positions should be avoided. Stick to loose piles on the cage floor.