When you were a little kid, chances are you tried to hide your peas under the potatoes. Or maybe fed them to the dog under the table. Just because someone gave us healthy and nutritious food didn't mean we ate it. Our rabbits and guinea pigs may be doing the same thing: we need to think about FEEDING unlimited hay vs. EATING unlimited hay.
A lot of rabbit and guinea pigs are picky. They'll sort through the hay and pick out only the 7 pieces they like, leaving the other 2 lbs for the hoomins to clean up. You may be putting out fresh hay every single day, and they might be eating a tiny tiny bit of it.
At least 80% of the diet should be hay. The rest can be made up of fresh greens, dried herbs and flowers, and a small amount of pelleted food. SMALL amount - like 1/8 of a cup per day for medium sized rabbits. If they are eating this diet, and maintaining a healthy weight, then they are getting enough hay. As a rough estimate, your rabbit should be eating a pile of compact hay roughly the size of their body every single day. A 6 lb rabbit should go through 10 lbs of hay per month, no problem.
Guinea pigs need a minimum of about 3 oz of hay per day, so each piggy should go through about 6 lbs of hay each month. Again, don't overdo it with the pellets. The piggies do need some Vitamin C, but make sure they get it in healthy forms, like rosehips and fresh veggies.
If your rabbit or guinea pig isn't eating enough hay, cut back on the pellets. You can also try mixing in a little orchard grass or other hay to make things interesting. We've got a few more tips and tricks as well. If you aren't sure which hay might work better, we've got a blog post about that too.
We hope that helps!