Emus are extremely strong. We learned the hard way.
My back door neighbor is an animal refuge and has several emus, ostrich and a few other animals that run in her 10 acre pasture. The fence is secure for the most part but our boundry line, due to pepper trees, the fence has come apart in place. One of the emus somehow go through, a very small hole in the fence.
They will go right through barbwire, so I say you would need solid horse type fencing and built a little higher than you would for a horse or cow.