Coyotes are pretty common around here, but I've never heard of anyone having problems with them bothering livestock. Unfortunately it is not uncommon for people to lose chickens, cats and small dogs to them. Coyotes are pretty skittish and very easily intimidated, I am nearly positive that your horse is in no danger of being attacked.
Also, I've run into a few while I was out riding and they wanted NOTHING to do with us! They greatly outnumbered us, but they ran away.
"Horses don’t have hard mouths, they have hard, stiff bodies. The softer you can get the horse through his body, the softer he will be in your hands." Clinton Anderson
Last edited by AQHA13; 06-30-2011 at 10:09 PM.