I mean I could but I have a nearly limitless supply of rabbits in my yard. Their fur makes great gifts. My plants love the compost I get from everything else. As a bonus the blood compost deters rabbits from eating my cabbage.
Funny thing, I can’t seem to find any type of vegan certification that is concerned with the use of animal byproducts or waste in fertilizer. A few specifically say they do not check fertilizer.
For anyone like this to be a good thing there needs to be a system of checks and balances. There should be an appeal process that is low effort and low or zero cost. There should also be a verification process by a third party before anything can be added.