On the ranch we live on they have a breeding program.. PLEASE NOTE: These are not my horses nor do I have any control over their health or care!!
They kept the weanlings (about 20) in a dry lot with some hay after being weaned. The hay was crap hay or left over from last year or something and it had a lot of cheat grass in it. They were eating it OK but not cleaning it up as well as they were the other stuff. One filly started looking real bad, skinny and swollen in the mouth, so the owner took it out into the corrals and found it's mouth was covered in ulcer type abrasions and pustules containing cheat grass. There was just too much of it so they took her to the vet, the vet cleaned her up as best as she could, took a biopsy and put her on antibiotics (I think, I wasn't there)
Two days later she was too weak to get up and too weak to even stop the birds from attacking her. She died that night.
That same day another was found almost dead (they had to shoot him to end the suffering)
There are two others that are on this track and all 20 of them have these in their mouths.
I helped them dig as many cheat grass out of the sores as I could but they are deep in there and it's been this way for too long.
My question is are these caused from the bad hay or did they have the ulcers before the hay. They do not have any on the outsides of the lips, nose or anything else, no outward signs besides dull eyes and depression, and obviously they are getting skinny from not being able to eat.
The wounds are on the insides of the lips, under the tongue, cheeks and even on the bars. Nothing on the tongue.
I don't have pictures.