I have a 'ulcer-prone' mini. He is and always has been, a very sensitive little horse, and could be described as 'reactive' in some ways,even though he is smart and the most willing worker I have. He has also been a near lifetime cribber--some of these are things that may predispose to ulcers.
Here's some things that have worked w/ him.I won't claim that this specific regimen will work w/ all horses, only that it seems to have worked for this little horse.
I also went the ranitidine route--4-150 mg. tabs(he weighs @ 220 lbs.) three times daily, but for a total of six weeks. JMO, but two weeks seems a really short 'treatment' period...did your vet recommend this time span? When he seemed to be showing slight symptoms of discomfort after about a month after his latest treatment period, I put him BACK on the ranitidine, and over several weeks, have very gradually decreased the dosage, and am now down to one-4 tab dose once a day.
Increasing feedings to a MINIMUM of three a day.
Feeding a high percentage of good alfalfa, as well as good grass-and for his size, a LOT of hay. I spend a good deal of time sorting through the grass(this year...UGH!), as I ended up w/ some that is over-mature and overdry, so try to sort out the 'straw-like' strands AND the 'powdered' stuff that ends up on the 'floor' of my hay prep surface(too-dry hay plus plain old DIRT.)I don't dare feed such stuff; I don't think it is safe for my horses, even those who would eat it(my ulcer horse is picky and probably would leave it, but I simply don't risk it.)
Minimizing the amount of concentrate. I have read that research shows that concentrates are MUCH harder to properly digest for horses than forage, the feed they evolved to eat. I give this horse(now a 14 YO) a minimal amount of TC 'Lite' mixed w/ a minimal amount of a senior 'pellet' by HiPro twice daily, primarily as a 'carrier'for the other 'stuff'; I add plain salt, some UGard, a small amount of Formula 747(he lost a LOT of condition, and noticable weight, during his latest bout w/ ulcers, but is looking MUCH better, although still not really 'in condition', after this winter), and, very helpful I believe, a product from Omega Fields which is a stabilized ground flax combined w/ a yeast product. At the early PM feeding, my horses all get soaked beet pulp; this horse gets about 4 1/2 cups, served extra wet, as is one other who wasn't as good on water intake--with his PM UGard, small amount of concentrate mix, and salt.
I have just 'invested in' several Slow feed hay bags from Busy Horse, but have yet to set them up for use. YEARS ago, I offered my idea of a way to feed hay from a 'small openings' hay bag to a friend who was concerned about a hay belly in a tiny gelding she'd gotten from me. MY BAD, I never followed up on it for myself--and now EVERYONE and his uncle is making 'slow feeders' and selling them! At least, there is now experience being reported--what works, what doesn't, etc.--and I am looking forward to seeing if the concept will work for my horses. I DO BELIEVE that it is VERY important to try to create a situation where a horse feeds on forage slowly, and as CONTINUOUSLY as possible! For those of us who do NOT have pasture(or hardly ever, as in my own case), this is doubly important, IMO. I think 'slow feeding' is one of the best concepts that is finally being embraced in many years, and I HOPE that I can make it work with my horses!
Lastly, letting a horse OUT to be able to move around as much as is reasonably possible, is also, IMO, VERY important. This winter, when the snow was 8" deep, I'd turn my 'barn' horses(who have 12' square stalls, roomy for minis, but still, very restrictive to be 'shut into' for very long, at ANY time, IMO) out. I have about 4 acres of 'native' grass-sparse due to drought years and the plain fact that this IS the desert SW. They could and would run around, paw through the snow for a bit of 'chewing' on the sparse grass, in general, just be able to be horses. They have roomy runs off of their stalls, but still 'need' to get out, esp. when the weather isn't allowing regular 'work'.
Best wishes to you in successfully treating this always-difficult condition!
Margo