Hay is vital in their diet!
UNLIMITED Timothy Hay (or a grass hay) is recommended for cavies. For young cavies under the age of 4 months and pregnant or lactating mothers, alfalfa hay is also recommended. For those cavies, you could mix half Timothy and alfalfa. Since alfalfa hay (a legume, not a grass hay) is too high in calcium, it should only be given to adult cavies as an occasional treat. Timothy and alfalfa are types of hays, not brands of hay. Other grass hays include orchard hay or meadow hay.
According to Dr. Curt Nakamura, an exotic vet specialist at Adobe Animal Hospital in Los Altos, California, grass hay is an important part of a cavy's diet:
"One of the most important items in the guinea pig diet is grass hay, which should be fed in unlimited quantities to both adults and baby guinea pigs. It is important to provide an unlimited source of hay because pellets do not provide enough long fiber to keep their intestines in good working order. The long fibers stimulate muscle contraction of the intestines to improve and maintain gut motility (to prevent gastrointestinal obstruction).
"I cringe when I see photos of cages with nothing but pristine shavings and maybe a small hay rack on one end. Pigs LOVE hay and LOTS of it! They love to PLAY in it, SLEEP in it and under it, EAT it, RUN through it, and of course, poop and pee in it! Be generous in the cage. Change it or refresh it every few days. Your pigs will love you for it."
Teresa, Cavy Spirit
Chewing hay is also important. Like rabbits, the molars in guinea pigs are constantly growing and must be ground down by chewing. Constant chewing on hay promotes healthy and normal wear on their molars. Treats and chew sticks are not efficient at wearing the teeth.
Alfalfa hay is rich in protein and calcium, but when combined with pellets it doesn't have the proper ratio of calcium and phosphorus. This can lead to improper gastrointestinal motility, such as diarrhea. It also may predispose certain guinea pigs to calcium oxalate bladder or kidney stones. Timothy hay is a better choice and is becoming more readily available. It's important to keep your guinea pig sleek, so cut down on the amount of protein and calorie-rich pellets while feeding timothy hay."
Packaged Timothy hay found in stores is dry and stale and less nutritious compared to what you can order from a farm. In addition, most farm hay can be delivered to your door in just a few days at a fraction of the cost of pet store hay in a variety of quantities.
If you must buy hay at a pet store, look for the greenest, freshest hay possible. Ordering direct will save you 50-75% or more, especially if you order larger quantities.
Buy the Bale! If you have a lot of guinea pigs and can store some extra hay, then finding a local source of good Timothy or grass hay by the bale is definitely the cheapest way to go. A bale of hay from a farm or hay distributor is around $25 to $40 and that's for approximately 200 pounds of hay! Some feed stores will let you buy partial bales or in bulk. Feed store prices may be slightly higher. Some farm or hay sources will let you buy half bales.
Timothy 2nd-cut is generally preferred over Timothy 1st-cut. First-cut still has the seed heads on the hay. Second-cut is softer and greener. Shipping time and/or cost may factor into your decision on where to buy hay. Please supply your cavy with fresh hay. They will love you for it!
According to Oxbow, "The first cutting is harvested in mid summer and is more mature, containing a higher stem to leaf ratio and is coarser in texture. It is actually healthier as it is higher in fiber and lower in protein than a second cutting timothy. But many small animals do not find it as appetizing.
The second cutting Timothy is an immature cutting of hay and therefore contains a higher leaf to stem ratio. It is harvested in the late fall and is very soft and palatable to small animals. It is our leafiest hay and our most popular hay."
If you use hay for bedding or as a top layer of bedding, or if you are liberal with hay on the floor of your cage, be sure to change it frequently. Hay does not absorb urine; it can mold and cause a damp environment for your guinea pigs. So be generous with fresh, clean hay!
Hay can be stored for many months, depending on how fresh it is and if kept in the proper conditions (see some of the links below). It should be opened to breath when you get it. Keep it in a dry and well-ventilated place, not in plastic. A wooden or cardboard box is ideal. If you get a bale or a partial bale, it will stay fresher longer if you break up the bale as little as possible. If you get a whole bale, try standing it on end, pop the strings, and use a section (or flake) at a time off the top. Just be careful as some bales expand more than others. If you get a shipment from APD or Oxbow, open the bag, leave the hay in the box, cut and remove the plastic.
Hay QualityDepending on the season and the weather at the farm, sometimes the hay may be drier or less fresh than at other times. Don't give up on trying hay from a source if you get one shipment that may not seem up to snuff. Ask them about their season. Mother nature can't be guaranteed to deliver!
If you notice any clumps of hay that seem "welded" together, that hay has likely been exposed to moisture and may be moldy. Any moldy or questionable hay should be discarded.
Also, sometimes there are discussions about the possibility of getting mites or other "bugs" or parasites from hay. Hay does NOT harbor mites. Mites need a living host to survive.