I have actually read a few things which completely contradict some of the replies to your post and that actually you should never give rabbits lawn mower clippings! From what I’ve read, the heat from the lawnmower can actually cause the clipped grass to release a chemical which is actually harmful to rabbits and can cause stomach upset/ other problems so I would definitely advice against it, even if the grass isn’t treated at all. I think it is completely okay to pick your own grass for your bunny/cut some with scissors (no heat involved), but not from a lawnmower to be safe.