On a horse farm, gates take a lot of abuse and require extra thought and care. Horses see the gate as a way to get back to their feed and hay and may lean against the gate while waiting for it to be opened.
The gate should be as tall as the fence itself, and hung on extra-sturdy posts. It needs to be at least four feet wide; wider is better, although wide gates can be difficult to shut while handling a horse. Gates should not be made of netting; horses are likely to paw at the gate and can catch their feet or pull off shoes.
A gate used with an electric fence needs an insulated handle so you can unhook the gate without getting shocked. It must also be wired to become dead when unhooked, so it won't shock you or a horse or spark and start a fire in dry grass.
You can bypass the gate by burying the electric wire or by erecting a tall lintel over a standard gate, high enough for the tallest horse to pass under and then some, and running the electric wire over that spot. However, you will then have permanently shock-free area at the gate, which may partially defeat the purpose of the electric fencing. On the other hand, once a horse is shocked going through a gate, he may never want to go through it again.
See also Fencing Materials