If you remember one number from this guide, make it this one: hay should be 80–90% of your guinea pig’s diet, available unlimited, around the clock. Not pellets. Not vegetables. Hay. It keeps their gut moving, wears down teeth that never stop growing, and prevents the two most common serious health problems in pet guinea pigs — dental overgrowth and GI stasis.
But “hay” isn’t one product. Here’s the complete breakdown.
The short answer: which hay for which pig?
| Pig | Best hay | Why |
|---|---|---|
| Healthy adult (6+ months) | Timothy (or orchard grass) | High fiber, low calcium |
| Baby under 6 months | Alfalfa | Extra calcium and protein for growth |
| Pregnant/nursing sow | Alfalfa | Higher calcium and calories |
| Picky eater | Orchard grass | Softer, sweeter |
| Allergy-prone household | Orchard grass | Lower dust |
For the vast majority of owners with healthy adult pigs: unlimited timothy hay, with orchard grass as a fine alternative.
Why hay matters more than everything else
A guinea pig’s digestive system is built to process a near-constant intake of fibrous grass. The long fiber strands keep the gut contracting; without it, the digestive tract slows and can stop entirely — GI stasis, which is an emergency. Hay’s abrasiveness also grinds down molars that grow continuously.
Timothy hay: the default staple
Timothy is high in fiber, moderate in protein, and low in calcium — the exact profile an adult pig needs for unlimited feeding.
Cuttings matter:
- 1st cut — coarsest, highest in fiber, most stemmy
- 2nd cut — the sweet spot: softer and leafier, still fibrous
- 3rd cut — softest and leafiest, lowest fiber
The Small Pet Select 2nd Cutting Timothy Hay is the community benchmark.
Petsofweb is reader-supported. When you buy through links on our site, we may earn an affiliate commission.
Orchard grass: the softer alternative
Orchard grass is nutritionally very close to timothy but softer, finer, and slightly sweeter. Good for picky pigs, allergy-prone households, and elderly pigs.
Alfalfa: great for babies, risky for adults
Alfalfa is a legume hay — significantly higher in calcium, protein, and calories. For growing pups under 6 months and pregnant/nursing sows, that’s exactly what’s needed. For healthy adults, chronically high calcium intake leads to bladder sludge and bladder stones.
Meadow and oat hay: variety, not staples
Meadow hay is a natural mix — great as rotation hay. Oat hay is coarser with tasty seed heads — offer once or twice a week as treat hay.
How to judge hay quality (the 30-second test)
- Color: green, not brown or yellow
- Smell: sweet and grassy (musty = mold, do not feed)
- Texture: leafy with pliable stems
- Dust: shake a handful — a small puff is normal, a cloud is not
Storage: keep it fresh, keep it dry
Cool, dry, dark. Breathable, not airtight (cardboard box or paper bag). Off the floor. Buy in reasonable quantities.
The 5 costliest hay mistakes
- Feeding alfalfa to adults — the #1 hay mistake, direct road to bladder stones
- Running out overnight — hay must be available 24/7
- Feeding dusty or moldy hay — respiratory infections can kill
- Relying on pellets instead of hay — pellets are ~5% of diet, not a replacement
- Storing hay in plastic — trapped moisture means mold
Frequently asked questions
How much hay does a guinea pig need per day?
Unlimited — literally as much as they want, 24/7. Hay is ~80% of the diet.
Is timothy or orchard hay better for guinea pigs?
Both are excellent. Timothy is the classic high-fiber staple; orchard grass is softer and often better for picky eaters.
When should I switch from alfalfa to timothy?
Around 6 months of age. Start blending at ~5 months, transition fully by 6 months.
Can guinea pigs eat hay cubes instead of loose hay?
Hay cubes are a fine supplement but not a replacement — they don’t provide the long-strand fiber needed.
Why won’t my guinea pig eat hay?
Try softer cut (2nd-cut timothy or orchard), check freshness, reduce pellets slightly, offer in pile as well as rack. If a previously hay-happy pig stops suddenly, see a vet.
The bottom line
For healthy adult guinea pigs: unlimited timothy or orchard grass hay, refreshed daily. Save alfalfa for babies under 6 months and nursing mothers. Pair it with fresh vegetables and proper vitamin C, and the diet side is solved.
This guide is for general information only and isn’t a substitute for veterinary advice.
