Just to add. In today's economy calling the vet everytime they look as if they might yawn is "out" for most. I use to live where no vet was going to do a "call out" for a single horse. So, I didn't just load them up for an emergency call at the drop of a hat, either. But to me, the biggest "protection" is knowing your horse well - well enough to know if it is actually "off" or it is just a "mood", the weather, its manner of protest, what. I still err on the side of caution, though. If you know your horse well and it seems "off", it is "off".