To answer your question, NO, typically you do NOT have to apron out anything on a livestock fence. You do it on a chicken enclosure to keep predators from digging in/under (weasles/mink/coons/possum/fox/coyotes/dogs/cats/etc.) for a chicken dinner. That's not normally going to be an issue with goats/sheep/cattle/etc. Some folks will apron on the inside of a pig enclosure to keep them from digging out, but it's typically with welded wire fencing (2"x4") or even hog panels...
Some goats can jump over a 4' fence, and a decent sized coyote can jump 4' straight up from a stand still. Stray dogs typically will not jump over the fencing but will try to go through it or under it. For the above reasons as well as others, many folks like to put a hot wire at the top of their fencing to keep things from trying to go over, another hot wire outside down low to keep things from trying to go under, and one about goat knee height inside to keep the goats from rubbing against the fence thereby stretching it and eventually damaging it.