50mA (.05) can kill an adult!! especially if current flow is through the heart.
There is almost no way to kill with electricity
unless current passes through the heart. Anywhere else, you need a lot more current; enough to cause tissue damage through heating.
Cattle fences are about 10,000V - I have designed a few of the units
One uses a car ignition coil, usually. The current is very low. But they can kill a horse (via a heart attack, presumably) if it gets tangled up in the wire and I am aware of one case near here.