It's listed as being toxic to animals. The leaves are certainly very toxic and can cause heart failure, as can the fruit and seed depending on how much is ingested. But I also read of rabbits that were fine after eating some of the fruit or seed, so may be possibly less affected by small amounts of the fruit being ingested than some other animals. But I also can't say anything for sure.
If you're concerned at all, it's best to call ASPCA animal poison control(fee is charged) or your rabbit vet, for instructions on how best to procede. Certainly if you see any indication of lack of appetite, respiratory difficulty, mouth breathing, swelling around the face, or bluish/gray/pale mucous membranes, then it's an emergency and you need to get your rabbit to the vet immediately(have your emergency vet number handy just in case).
https://www.merckvetmanual.com/toxicology/food-hazards/avocado-toxicosis-in-animals
https://www.aspca.org/pet-care/animal-poison-control