Some battles just aren’t worth trying to fix!
Nexium/esomeprazole is one option. The question is, do you use the common 3-4 capsules and hope that’s enough, or do you hedge your bets and use the whole bottle? (assuming 1000-1200lb-ish horse)
I wouldn’t do the injectable - way too many horses are just not fine after the 2nd injection 
You could try Abler “pop rocks”.
Both those alternatives would be placed right on top of the meal. When I’ve used them - Abler years ago, esomeprazole much more recently - I put them front and center, so the first hangry bites are less likely to get chewed (well), so more of the drug gets into them intact. And, enough horses are scoped before/after showing healing, to prove that method can work.
The question is - what kind of ulcers are there? These drugs don’t work well/at all on glandular or pyloric ulcers, but do work well on squamous ulcers. If you’re just basing “it’s ulcers” on symptoms, I’d add in sucralfate, which will help glandular ulcers as well