OP - these sores in their mouths... (sorry, don't have time to read whole topic right now)... were they fairly small (quarter size and smaller?), and how many? Any on their tongues?
The place I do some work for has a very sick mare too. She was okay a month ago when I was last here but has gone downhill - skinny, shivering, and her mouth is FULL of sores (I had the vet out yesterday). She also has a snotty nose.
The vet thinks either: strangles (due to scabs under her jaw) or some other infection. But, could it be foxtail??? The owner of the place had two very foxtaily round bales that were meant to be burned, but the horses got into them and ate them about a month and a half ago or so.
I had a dog when I was a kid that got foxtail in it's mouth.. it formed an abcess and eventually burst out the side of his jaw (gross, I know) and he was fine.
We had the mare coggins tested but the owner said no to the $450 blood work and culture on the runny nose... which is sad, but I understand. This mare is part of a working string of 25 horses and unfortunately, they are viewed as more "disposable" than many of us would view our horses. I've gotten the go-ahead to get some penicillin though.
This thread got me thinking... could it be foxtail?? All the other horses looked pretty good... I only brought this mare out of the herd because she looked so poor.