Today, as I was getting ready to go to work, I checked the horses as I usually do, and Rosie, our Belgian was missing. I quickly spotted her with our next door neighbors horses. The bottom strand of wire between our pastures was pulled out of the electric fence that separates them, and apparently Rosie had crawled under a three foot gap! I would liked to have seen her do that! Luckily, I trained our horses to come when called, so I just called her, and opened the gate between the pastures, and she was back where she belonged. But I had to put the horses in the paddock until my neighbor fixes the fence. It turns out she had turned it off "Because of all the deer." I don't really understand that one.
But, the trouble with electric fences is that they can short out, and then they're not much of a barrier to horses. There's always at least one horse that will test an electric fence to see if it's on, and if it's not it's easy for them to just go through it.