You could maybe scale back the pellets. 1/2 cup is on the high end, but for a big bunny isn’t too crazy. I think most of us here feed between a tablespoon and 1/4 cup per day. The shelter I volunteer at does 1 tablespoon per bun, no matter how big they are (but buns that are known to be underweight or are growing get more). Since yours are fully grown, they don’t need as many pellets. I tend to think of pellets as a multivitamin rather than a staple of the diet. Once they get settled, you might ask your vet what he thinks of their weights and they can advise about pellet amounts. My vet really likes to see lean bunnies, especially the larger breeds which are prone to obesity. As big bunnies get older, the extra weight really wears on their joints, so he likes to see them trim to help with their mobility. That said, don’t just put bun on a diet without advice from your vet. 🙂
I’m guessing the shelter feeds veggies twice a day, because they prob (hopefully) have hay 24/7. I feed mine prob about 2 handfuls of greens a day (split into two feedings). I agree their mix of veggies is weird… brussel sprouts are prob pretty gassy. If you check out this list you will get lots of ideas for veggies: https://binkybunny.com/bunnyinfo/veggie-list/
I would start with one or two they have had before, then you can slowly add variety to their diet (stick to adding no more than 1 new veggie a week).
The most important thing is to see good hay consumption. So if you are feeding the same amounts as the shelter but not seeing them eat much hay, you can reduce the pellets and greens a bit to see if that helps.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.