Hay Is Not a Side Dish — It Is the Whole Meal
If there is one thing I wish someone had hammered into my head before I got guinea pigs, it is this: hay is not supplemental. It is not a nice-to-have. Hay should make up roughly 80 percent of your guinea pig's diet, and it needs to be available in unlimited quantities at all times. Day and night. No exceptions.
Guinea pigs have a digestive system built around constant fiber intake. Their gut needs a steady stream of long-strand fiber to function properly, and their teeth — which grow continuously throughout their lives — need the grinding action of chewing hay to stay worn down to a healthy length. Without adequate hay, you are looking at GI stasis, dental disease, or both. These are not minor issues; they can become life-threatening surprisingly fast.
The good news is that hay is relatively cheap, easy to source, and most guinea pigs love it. The challenge is figuring out which type of hay to buy, because walk into any pet store or browse online and you will find half a dozen options. Let me break down each one so you know exactly what you are getting.
Timothy Hay — The Default Choice
Timothy hay is the most widely recommended hay for adult guinea pigs, and there is a good reason it holds that top spot. The nutritional profile hits exactly the right notes: high fiber, moderate protein, and low calcium. That low calcium content is particularly important because excess dietary calcium in adult guinea pigs can contribute to bladder stones and urinary sludge — painful conditions that require veterinary intervention and sometimes surgery.
Timothy hay comes in three cuttings, and understanding the differences will save you from buying hay your pigs refuse to eat.
First Cutting
First cutting timothy is coarse, stalky, and high in fiber. It has thick stems with fewer leaves and seed heads. This is the most structurally robust cutting and is excellent for dental health because pigs have to really work to chew through those thick stems. The downside is that many guinea pigs find it less palatable than softer cuttings. My own pigs would pick through first cutting to find the leafy bits and leave the stems behind.
Second Cutting
Second cutting is the sweet spot for most owners and most pigs. It has a good balance of stems and leaves, with a softer texture than first cutting but enough structural fiber to promote healthy chewing. The color is typically a nice green, and it has a pleasant, slightly sweet aroma when fresh. If you are not sure which cutting to try, start with second cutting. It has the highest acceptance rate among guinea pigs.
Third Cutting
Third cutting is the softest, leafiest, and most aromatic. Guinea pigs tend to love it — it is basically the dessert of timothy hay. However, it is lower in fiber and higher in protein and fat compared to earlier cuttings. I use third cutting as an enticement for picky eaters or as a way to boost hay consumption in a pig that is not eating enough. But for day-to-day feeding, second cutting is a better nutritional choice.
Orchard Grass — The Best Alternative
Orchard grass is my personal favorite alternative to timothy hay, and here is why: it is softer, sweeter smelling, and seems to be universally loved by every guinea pig I have ever offered it to. The texture is finer than timothy with long, slender blades that are easy for pigs to pick up and chew. Nutritionally, it is very similar to timothy hay — comparable fiber, protein, and calcium levels.
Where orchard grass really shines is for owners or family members with hay allergies. Timothy hay is a grass, and many people who are allergic to grass pollen find that handling timothy hay triggers sneezing, itchy eyes, and congestion. Orchard grass produces significantly less allergenic dust and pollen, and many hay-allergic owners report being able to handle it without symptoms.
I mix orchard grass with timothy hay about 50/50, and my pigs have never been happier with their hay situation. The variety keeps them interested, and both grasses provide excellent nutritional value. If your pig is a picky hay eater, introducing orchard grass into the mix often solves the problem.
Oat Hay — The Treat Hay
Oat hay is distinctive because it includes the oat seed heads still attached to the stalks. Guinea pigs go crazy for those crunchy seed heads — watching a pig discover an oat head for the first time is genuinely entertaining. The stalks themselves are thick and crunchy, providing good dental exercise.
The catch is that oat hay is higher in fat and protein than timothy or orchard grass, particularly the seed heads. It should not be the primary hay in your pig's diet. Think of it as a hay topping — sprinkle some oat hay into the regular timothy or orchard grass to add interest and encourage more hay eating overall. A handful mixed into the regular hay a few times per week is a good approach.
Meadow Hay — The Variety Pack
Meadow hay is not a single grass species. It is a mix of whatever grasses, herbs, and plants were growing in the field when the hay was cut. This means every batch is slightly different, which can be both a pro and a con.
The pro is variety. Meadow hay exposes your pig to a range of flavors and textures, and some pigs find it more stimulating than a single-species hay. The con is inconsistency. You cannot be sure exactly what is in each batch, and the nutritional profile varies. Some batches may be higher in calcium or lower in fiber than ideal.
I use meadow hay as an occasional addition rather than a staple. It is a nice way to mix things up, but I want the predictable nutrition of timothy or orchard grass as the foundation.
Alfalfa Hay — Special Cases Only
Alfalfa is not a grass — it is a legume, and that makes it nutritionally very different from the hays we have discussed so far. It is high in protein, high in calcium, and higher in calories. For adult guinea pigs, this profile is too rich for daily feeding. The excess calcium can contribute to bladder problems, and the extra calories can lead to obesity.
However, alfalfa is appropriate in two situations. First, for guinea pigs under six months of age. Growing pigs need the extra calcium and protein for bone development and growth, and alfalfa provides that. Second, for pregnant or nursing sows who have increased nutritional demands.
Once a guinea pig reaches six months of age, transition gradually to timothy or orchard grass over a two-week period by mixing decreasing amounts of alfalfa with increasing amounts of adult hay. A cold-turkey switch can upset their digestion.
How to Buy and Store Hay
Quality matters enormously with hay. Fresh, high-quality hay is green, fragrant, and free of excessive dust. Brown, musty-smelling hay has lost much of its nutritional value and may contain mold spores that can cause respiratory problems. If you open a bag of hay and it smells off or dusty, do not use it.
Pet store hay is convenient but often overpriced and not always the freshest. Buying from online hay suppliers — companies like Small Pet Select, Rabbit Hole Hay, or Oxbow — typically gives you better quality at a lower price per pound. Many of these companies ship directly from the farm, so the hay arrives fresher than anything sitting on a store shelf.
If you live in a rural area, connecting with a local farmer who grows timothy or orchard grass can be the most economical option of all. A single bale can last months for two guinea pigs and costs a fraction of bagged hay. Just make sure the hay has been properly dried and stored — damp hay develops mold quickly.
Store hay in a cool, dry place with good air circulation. A breathable container like a cotton bag or a ventilated bin works better than an airtight container, which can trap moisture. Keep it off the floor and away from direct sunlight. Properly stored hay maintains its quality for several months.
Encouraging Picky Hay Eaters
Some guinea pigs are enthusiastic hay eaters from day one. Others are frustratingly selective, picking through the hay for choice bits and ignoring the rest. If your pig is not eating enough hay, here are strategies that have worked for me and for other owners I know.
- Try a different cutting or species. A pig that ignores first cutting timothy might devour second cutting orchard grass.
- Mix a small amount of oat hay into the regular hay for added interest.
- Place hay in different locations around the cage. Some pigs prefer eating hay while sitting in a hideout. Others like it near their water bottle.
- Use a hay rack rather than piling it on the floor. Some pigs eat more when they can pull strands from a rack.
- Stuff hay inside a toilet paper tube for foraging enrichment. The challenge of pulling it out often sparks interest.
- Ensure the hay is fresh. Hay that has been sitting in the cage for more than a day often gets ignored. Refresh it daily.
If your pig is eating very little hay despite these efforts, a vet visit is in order. Loss of interest in hay can indicate dental problems that make chewing painful, and early intervention makes a big difference in treatment outcomes.