Apparently there are "two" versions of the ACD

The Australian Cattle dog, tail intact (AKC recognized and standard)
The Australian Stumpy-Tailed Cattle Dog, tail docked or natural dock (not AKC recognized OR breed standard practice)

http://www.dogbreedinfo.com/stumpytailcattledog.htm
http://www.dogbreedinfo.com/australiancattledog.htm

They're the EXACT SAME BREED just have their tail docked.