While in So. CA, we never did vaccinate for Rabies.
Here in TX, they have had documented cases of horses contracting rabies. So, we
give it yearly. Talk to your vet, if they feel your area has a chance of your
horse being exposed. I was told, it is most common for a horse to get
bitten on the nose, as they have their head down, eating, and a rabid critter
(skunks high on the list) comes over and wants what ever the horse is eating,
and bites them. Or, curious horse goes to check out weird critter stumbling
around in their field. Rabies is a death sentence. Indeed, pretty cheap
insurance if your horses might be at risk.