if he truly has ulcers, it takes 45 days to completely get them over it. takes that long for the stomach lining to heal and grow new lining, ulcers dont go away in a couple days, maybe the acidity in the stomach has lowered, but they have not went away. About drinking- I always add water to my horses feed. some get a cup some get 4 cups, just depends on how much they normally drink daily. at least you would know he is getting something. But you have an underlying problem your vet is not seeing. you might need to visit another vet. Oh, just a thought, is there any possible way your horse can get his head out of his stall and drink out of the other horses bucket? my horses would rather drink out of someone elses bucket than their own, also Duke likes to drink out of the community bucket outside when he goes out. change your plastic bucket to a rubber bucket or put a small trough in the stall. just change up his water bucket, sometimes that helps, cause for some reason he doesnt like what he has. good luck
forgot to add, Charlotte is right, banamine is the worse thing you can give a horse with ulcers. to get control of the acidity, vet gave a huge bottle of Carafate, had to give 12cc right before feeding each day, lasted a long time. working out is totally ruled out, when a horse is exercised / worked out for the show ring is a big no-no too. when a horse is exercised, it increases the acidity in the stomach which inflames the ulcers. My vet gave me ulcerguard to use too. if you get this, there are notches on the tube. I only give 2 notches, seems very little but this stuff is really potent and works good.
the best thing is to turn out on the yuckiest weeded area, the yucky roughage is the best thing for the ulcers, or a really dried grass, not lush green pastures. so the more crappy stuff in the gut the better, ruined my 2yo gelding for a bit with the show ring, but we hand walk now up n down the hill and he can only stand in his sweats for 2-3 hours to sweat his neck.
oh yeah, other than yucky weeds, alfalfa is great too, or cubes. it has calcium in it and helps with the ulcers. when I haul al over the country to the shows, I used to fed free choice grass hay, they say that is not good, but to feed alfalfa instead because if the horse is feeling any stress, the calcium is the best thing for the lining of the stomach.
for water suggestions, i have tried hundreds of other things too. I have let baby carrots float in the water for about an hour, the horse will play with them and get water intake, cut up apples work too. I get the peppermint candies from all the Sonics I visit on the road, so sometimes I will throw a peppermint candy in it too, but take it out about 15 minutes later. some horses like it some dont, heard of gatorade, but never tried it either.
but if he is getting dehydrated, the vet will need to run fluids thru him until he potty's, and then one more bottle after that. but make sure he is not, cause his body organs will shut down on you if not taken care of