Very sad for all concerned both human and animal, but I'm wondering whether any contributors to this forum might have any thoughts on what possibly could have happened here? I'm puzzled,because I thought I understood that with earth-leakage/current balance protection systems,then it would trip when the currents were just a few mA wrong. Living in very damp West Wales,I have had my system trip simply as a result of the high humidity penetrating something electrical.
The only technical theory I've seen put forward so far on the horse electrocution incident at Newbury is this one. It aims to explain why some horses saw a fatal shock whereas humans handling the horses didn't really experience much of a shock.
In reply to Brad, the article I linked to actually does mention that the metal horseshoes could have been a contributory factor to the incident. I think there is such a thing as plastic horseshoes, which would be non-conducting, but they are rarely used.
It has to be remembered that though the horseshoe is a good electrical conductor, it is fixed to a horse's hoof, which would be expected by contrast to be a fairly good insulating material. High voltage electric fencing is quite often used to keep horses in a field, and nobody would do that if horseshoes were so dangerous when it came to electricity.
When the Newbury electrocution incident was first reported in the media, some journalists tried to explain it as all being down to the horseshoes. Four horses were involved in the incident, and the two wearing steel shoes dropped dead whereas the two others wearing aluminium shoes survived, so the journalists were claiming they were saved by their aluminium horseshoes. But if the electrical conductivity of the horseshoes is the controlling factor, that's the wrong way round. Aluminium has a sixth of the resistivity of steel, so it is six times a better electrical conductor than steel.