My part GSD and part kangaroo can clear five feet without batting an eye.
For a jumper I'd have to recommend 6' too. They still may be able to crawl over it, but it'll be harder than 5'.
If you don't have a jumper I'd say you could get away with four feet.
Bear, Anna, Molly, Ossie, and The Countess Lisl von Schlaf
An Unhappy German is a Sour Kraut!