I just did a dog pen and the charger is on the opposite side of the gate and there's no wiring jumping across the gate. The wiring threw me at first because of basically being an open circuit. When an animal touches either the positive wire and the negative wire OR the ground, THEY complete the circuit. Or in the case of a visitor I had here today that insisted on petting the dogs,
she completed the circuit. Here's a super basic diagram as it has no ground wires on the fence itself. They should have had the red arrows coming off the cows feet actually and not have had that red arrow in front of it's neck. Down the fence, in through the cow's nose, out it's feet.
If the soil is super dry, the circuit has trouble completing when an animal touches it. That's why we alternate hot & ground wires on the fence.
Here's another that shows more realistic circuit components
I'm not finding any good images with the ground wiring on the fence but in the above image, say that middle wire would get connected to the ground rods instead of being jumped out with the other two hot wires. Everything else is the same, including charger hookup.