not that i know of people here using........
are you referring to the greyish colour that look like a pellet....
not to sure if it can be eaten
rabbits can be crazy as they eat almost anything - from rubber, to plastic to even paper..
so i dont think this is encourage to use for them
some of them also will eat their own shit yes mine do at times.........
they are basically look like sawdust and i see some animal shop use it but whether healthy or not.....er....... imagine if their mouth itchy - trust me they just eat and eat all this pellet that similar like their daily food only it is grey!!!
for me i dont use this...
my rabbits will know how to shit at their cages only for a few occasions out of target....
i always wash their cage everyday yes..... making sure their cage are clean.....all the time
they eat a lot and shit a lot :)
its part of my responsibility..... and i dont mind doing for them..
they are free to roam around my house with my supervision..but poo poo but be left at their cage all the time....
anyway here is an article for you to read
http://www.ontariorabbits.org/hot_topics/hint_2.html