You have gotten great advice here.
Gastric ulcers can be in the squamous part of the stomach or the glandular part or both. Glandular ulcers are much harder to treat than squamous.
I had a similar horse. He was not aggressive to me but terribly so to other horses and also terribly herd bound. I treated him with Gastrogard but it didnt really help. I put him on Succeed and that helped a little. Scoping revealed glandular ulcers. It took three months of Gastrogard and Sucralfate to clear them up. It still did not change the behaviour.
In the meantime I did a CBC which showed a mild eosinophilia. My husband is an onc/hem so he had some insight in to what this might mean but I wasnt sure what to do other than monitor.
When the behaviors did not resolve and the eosiniphilia continued I had an internist come and ultrasound his abdomen lungs, etc. We found odd small circular spots, a little galaxy of spots, in his liver. A couple of unidentifiable things in his lungs. We sent the US everywhere and no one had seen anything like it.
He was fat, shiny, sound, never had a fever, skin issue, nasal discharge, nothing.
But he was clearly miserable. He had three statesā¦aggression, anxiety, depression. He was always sweet to handle and ride. But he was just a miserable horse. My vets were game but not sure if euth was the right thing, but they trust me and know me so went ahead.
His necropsy showed MEED. Every organ, brain, liver, stomach, intestines, heart! his entire body was riddled with the granular eosinophiliac tumors. He must have been in chronic agony. When I sent the nec results to the internist she just wrote back WOW.
He was 12. He had not one exterior symptom. ONLY behaviour.
If I were you, I would do a CBC, and do the omep/sucralfate, and put him on Succeed.
He is clearly telling you he is miserable. Youre a good mom to try to figure out why.