Hay isn’t basically dried grass but the thing about hay is that it’s safer. You never know what has touched the grass outside and it has bugs and mushrooms and stuff like that. And if you use pesticides or any chemicals on your grass then your rabbit can’t eat that. I know this is just an extreme story but my friends rabbit went outside and ate grass but it ate a mushroom and started bleeding all over and of course died. It was very sad and gruesome. I’m not saying its definitely going to happen to your rabbits but it’s a possibility. There may even be other animals out there who use your grass and they could have infections. It’s your choice though. I just believe that hay is safer. Pellets depend on your bunny’s weight and age. If they are under a year they should get almost unlimited alfalfa pellets. And hay or grass in your case. If older then about a cup of pellets a day. So yes if they eat a lot of grass cut down on pellets a bit. Pellets aren’t extremely important but they help put weight to your bunnies! Hope it helps!

How old is your bun? Pellets contain a lot of vital nutrients and really the only thing that can replace pellets is a large variety of leafy greens per day.

Adult rabbits should get about 1/8 cup of timothy-based (not alfalfa-based unless they’re pregnant or lactating, and definitely not that junk with all sorts of other unhealthy/unsuitable things like nuts and seeds mixed in that some vendors try to push) pellets per 4 pounds of body weight per day. The vast majority of their diet needs to be grass hay – timothy is the best overall and most widely-used and available but other grass hays like orchard, oat, Bermuda, brome, etc. are good – and 2 cups of fresh, washed/wetted dark green vegetables per 4 pounds body weight per day. You can feed grass to your buns, but as noted above you have to be VERY careful about where it comes from and to make sure that it’s not contaminated by pesticides or chemicals, other animals’ droppings, and doesn’t contain plants that are poisonous to rabbits.

Grass can be higher in sugars than hay, it depends a lot of the time of year and how often the grass is mowed.

If a bun needs to lose weight, reducing amount of pellets and other greens and substituting it with grass can result in weight loss. (The bun should still have hay and water at all times). My Bam has been on a grass-heavy diet since the end of August, and he’s lost a significant amount of body fat.

^ Timothy isn’t “the best overall” Its just the most common. All grass hays are pretty much equal

Pellets should be the smallest component of the bun’s diet. For an adult bun, you can give less pellets and more hay + grass. Hay doesn’t look like much, but it actually has about 7% protein in it. It’s the best food for the bun’s GI canal, including the teeth. 2 tablespoons (=1/8 cup) of a good quality pellets per 4 lbs healthy, adult bun is a good amount of pellets. The very young, the elderly, pregnant or lactating does and buns that have been poorly need more pellets.

Going completely pellets free is demanding of the owner. Today there are good quality commercial house bunny feed available, like Oxbow or Burgess or Supreme Science Select. The amount of indigestible fiber should be at least 20%. In “the olden days” commercial food was too rich and aiming at plumping up rabbits quickly. There are still show bunny foods available, but it should be avoided because it’s not designed for bunny longevity, and we of course want long term great health for our sweet pet buns.

Regarding the original question, I would think the best way to decide is to monitor their weight and poops to make sure they are getting enough fiber. I know with my two, their poops get darker and smaller when they aren’t eating as much hay, or when they hay is richer and softer (orchard grass vs. timothy, for example).

I would treat the grass as a part of their “leafy green” category, since it’s fresh and full of moisture.

I think of pellets as a multivitamin for them. I believe the oxbow bag says 1/4 cup per 4 lbs, but some bunnies gain weight on this amount, and don’t eat enough of their hay this way. Also remember, pellet companies want to sell pellets! So they will always give generous portions as recommendations.

I tend to feed abut 1/4 cup for my 9 lb bun, so in line with what others are saying about 1/8 cup. If you weigh your bunnies you should be able to calibrate how much they need to stay stable.

In summer, my six get one portion of pellets a day, as they are outside in the garden for maybe 10 hrs a day, chomping away at lots of fresh grass. The grass doesn’t grow enough in winter to feed six hungry buns, so mine get a handful of bought dried grass each morning, plus a second portion of pellets a day, i.e. they eat double the amount of pellets when not getting plenty of fresh grass, mine are around 3-4 years old, hard to give exact ages for the 5 rescues. All portions are small, almost as treat-size helping, if this helps?