The best hay for guinea pigs is a quality grass hay like timothy, and it should be available to them around the clock. Grass hay is the single most important thing in a guinea pig’s diet — it keeps their constantly-growing teeth worn down and their gut moving. Get the hay right and most of the day-to-day health worries take care of themselves.
This guide covers why hay matters so much, which types to feed, when alfalfa fits, the vitamin C piece owners often miss, and how to judge quality. It’s written plain, for New York keepers with one guinea pig or a whole herd.
Why Guinea Pigs Need Unlimited Grass Hay
Hay isn’t optional for a guinea pig. It’s the foundation of the whole diet — roughly 80% of what they eat should be grass hay, with a smaller amount of pellets and fresh veggies filling out the rest.
Two things depend on it. First, teeth: a guinea pig’s teeth never stop growing, and the long chewing that hay requires wears them down naturally. Skimp on hay and teeth can overgrow, leading to painful dental problems that usually need a vet.
Second, digestion. Guinea pigs need steady fiber to keep their gut moving. A diet short on hay can slow things down, which gets dangerous quickly. Keeping clean hay in front of them at all times is the easiest way to protect both. Veterinary guidance backs this up — the VCA Animal Hospitals feeding guide puts grass hay at the center of the guinea pig diet.
The Best Hay for Guinea Pigs: Timothy Is the Standard
For adult guinea pigs, a grass hay is what you want — and timothy hay is the standard choice. It has the right mix of fiber and coarseness, most pigs eat it happily, and it’s easy to find from local growers.
Timothy is the safe default, but it isn’t the only grass hay that works:
- Timothy hay — The go-to. Good fiber, widely available, and reliable for adult pigs. Compare cuttings and prices on our timothy hay page.
- Orchard grass hay — Soft and leafy, a nice option for a fussy eater or if timothy dust bothers your own allergies.
- Mixed grass hay — A blend can add variety and keep a picky pig interested, as long as it’s clean and mostly grass.
The type matters less than the habit: keep good grass hay available without limit, every day.
When Alfalfa Fits — and When It Doesn’t
Alfalfa comes up a lot, and it trips people up. Alfalfa is a legume, not a grass, and it’s much richer — higher in calcium and protein than grass hay. For a healthy adult guinea pig, that’s too much, and the extra calcium can contribute to bladder stones over time.
Alfalfa does have its place. Its richness suits animals that are building or feeding a body:
- Young, growing pups that need the extra protein and calcium.
- Pregnant sows.
- Nursing sows feeding a litter.
Even for these, treat alfalfa as a life-stage food and move to grass hay as pups mature. Because pregnancy and growth are health-sensitive, it’s worth checking the plan with your vet.
Don’t Forget Vitamin C
Here’s a quirk that catches new owners off guard: guinea pigs can’t make their own vitamin C, so they have to get it from their diet. A shortfall can lead to scurvy, a genuine health problem.
Hay is not the vitamin C source — its job is fiber and dental wear. Vitamin C comes from fresh vegetables, a fortified guinea-pig pellet, or a supplement your vet recommends. Keep the two jobs separate in your head: hay for fiber and teeth, veggies and pellets for vitamin C. If you’re unsure how much your pig needs, ask your vet.
How to Judge Hay Quality
Good guinea pig hay is easy to spot once you know the signs, and buying local lets you check before you commit. Look for these:
- Green color — A sign the hay was cut and cured well. Faded yellow-brown hay has usually lost quality.
- Leafy, not all stem — Plenty of leaf means better nutrition and a hay pigs actually want to eat.
- Sweet, fresh smell — Grass hay should smell clean and grassy, never musty or sour.
- Low dust, no mold — Dust can irritate a guinea pig’s sensitive airways, and mold can make them sick. Both are dealbreakers.
When you buy from a nearby grower, you can open a bale, smell it, and feel it before handing over money. Ask which cutting it is and when it was baled — a straight answer is a good sign.
Buying Hay by the Bale for Multiple Pigs
Small bagged hay from the pet store works fine for one guinea pig. But guinea pigs are social and often kept in pairs or small groups, and those little bags add up fast — you’re mostly paying for the packaging.
Buying a small square bale directly from a local NY grower usually costs far less per pound and often arrives fresher, since it hasn’t sat in a warehouse. Just keep it dry and off the ground so it doesn’t mold before you use it. If you also keep rabbits, the feeding logic overlaps closely — see our companion guide on the best hay for rabbits.
The Bottom Line on Guinea Pig Hay
Keep it simple: give adult guinea pigs unlimited grass hay — timothy is the reliable standard — and make it about 80% of the diet. Save alfalfa for the young, pregnant, or nursing, cover vitamin C through veggies or pellets, and feed only hay that’s green, leafy, sweet-smelling, and low in dust.
Need to restock? Browse hay for sale from New York growers near you to find timothy and other grass hay, or post a hay wanted request and let local sellers reach out. Buying direct means fresher hay, no broker markup, and a shorter trip home.
This guide is part of our complete guide to the best hay for every animal.
Ready to buy? Browse hay for guinea pigs for sale in New York from local farms on Empire State Haymarket.
