A. I hope he soiled his drawers, and
B. I hope he sees his humiliation online.
Oops, addendum, you can buy what the sign owner used--a low voltage cattle fence charger--at any farm supply store for about $20. Tractor Supply here has them in my neck of the woods.
And, yes, I've walked into an electric fence on Uncle's dairy farm...ONCE! That's all it took to sharpen my eye. ;)