I'm not talking an emergency "horse is throwing itself on the ground", "horse is 3 legged lame" or "horse is missing -insert body part here-", but just when they're not themselves and you can tell something's up with them.
Do you call asap? Or, do you take a wait an see approach?
I take a wait and see approach, to a degree. For example, Beau wasn't acting like his usual self last night - he would seem a touch colicky (only presented 1 colic symptom, which is more a "Beau symptom" for when he doesn't feel well in-general) every now and then, but a minute later seem fine. He bounced back and forth quite a few times... about an hour later I called the vet, if for no other reason then to give her a heads up. She diagnosed over the phone as weather related (it's been funky here in MD) and to give him banamine. I'm still not totally convinced it was colic, but it passed.