If you want to try using a blender I suggest starting with small prints first so you build up ~1 inch layer of finely chopped plastic near the blades. This way when you insert a larger print if doesn't bound around nearly as much allowing you to better grind it. This also noticeably lowers the stress on the blender when it running and helps to prevents jams.

I don't doubt it would work, but I'm curious how everyone has enough ABS prints available to make ruining even one blender worth it? On a side note if your a ranch operation, wouldn't using a hammermill be a lot easier? I'm guessing you probably have one around for feed grinding, or something similar.