Nursery questions

So I'm learning more about the nursery biz, and one thing that came up was when selling liners or plants grown out a full season(as I understand it) certain nurserymen ad a slow release fertilizer to keep plants alive. I was wondering if I had rabbits, could their manure serve as an additional assest and become that slow release fertilizer? My thoughts were, more natural and I'm already getting many functions from the rabbit anyway. Thoughts?