In article ,
"The Medway Handyman" writes:
Andrew Gabriel wrote:
This is a very important issue, much more so because of the
horses. Tiny leakage currents which humans can barely feel
are fatal to most livestock including horses, so this has
to be got right.

Really? I didn't know that. What about electric fences for example?

An electric fence is pulsed, and the animal has a choice to
move away from it. A leak from mains generally isn't pulsed.
It will create a potential difference across the ground where
it's earthed and the animal can't decide to let go of the ground
and may not have the knowledge or be too confined to move away.

I would have guessed that horses & cattle could have taken larger shocks
than humans because of thier greater mass. How does that work?

No, it's the opposite. In addition to the large wheelbase
problem which Guy mentions, it only needs a volt or two across
that to kill large animals, whereas a human would never have
any concern about touching the terminals of a 1.5V battery, or
even a 12V battery. This first showed up when a field of dead
animals was occasionally found with no explanation being obvious.
It has then been found that an insulator on an overhead wire is
leaking tiny amounts down the support pole, generating a small
potential difference across the ground not even noticable by
humans, but fatal to the livestock.

Someone on this newsgroup was involved with litigation resulting
from death of a horse due to earth leakage creating a small ground
potential, but I can't recall who it was.

--
Andrew Gabriel