Oxbow brand hay is typically the preferred. At both Petco and PetSmart you’ll find Kaytee brand and Oxbow. Oxbow will be the more expensive but generally it’s a higher quality.

Hay does not go bad unless it’s stored with moisture. It’s dried grass, so as long as it’s kept somewhere dark with air circulation and no contact with moisture (low humidity), then it can last forever practically. You’ll know it’s bad if there’s mold.

You’ll see two bag sizes if your store is like a general Petco/PetSmart. You’ll see small bags on a variety of oxbow hays, like a small bag of meadow hay, orchard hay, and oat hay. Then they have the very large bags on Timothy hay. Timothy is generally the go-to type, thus buying the large bag is good so you don’t need to go buy another bag for at least two weeks. I personally buy the oxbow hay stacks, and one pack lasts me one week with one bunny. Hay is the main part of their diet by far, so you’ll go at the minimum once a month unless you buy in major bulk.

There is a catch to buying in bulk, especially with a new rabbit. Some rabbits hate Timothy, and have a different taste preference. They’d rather have orchard or oat. To start, I would recommend buying the smaller bags until you figure out your rabbit’s preference.

If your rabbit is between 8 weeks old and 6 months old, you’ll need to start with alfalfa hay because younger rabbits need the dense nutrients and calcium in it to grow. If it’s closer to 6mo, you don’t need to buy a lot because the rabbit will transition over to Timothy/oat/orchard soon. Adult rabbits should not have alfalfa hay.