Sorry to resurrect the burping horse thread, but what posture does your horse display? After my horse's evening treats, he stretches his neck out long (and up) and makes a wind sucking sound - is this burping?
I've got a horse who does this exact same thing after being fed. I put him on a trial omeprazole which made absolutely no difference. This is a low key guy who has always been on 24/7 turn out with free choice hay; his weight is good; his poop is good; his coat is good. He's only 2.5 yrs old and a gelding. His pasture group is stable. He doesn't strike me as a ulcery kind of guy. But he urps and gurgles and stretches his neck out funny after meal times and I've even noticed it some during the day when he is resting from grazing. He doesn't lay down any more than his pasturemates, but did lay down a lot as a baby but not in a distressed kind of way and never belly up. He's half draft (Percheron) and was the easiest baby I've ever raised. He's had only one episode of choke ever that I noticed and it resolved without issue. I do feed pellets but since he and his full brother both had an incident of choke on them, I now water everyone's feed down which they seem to actually prefer. The full brother has absolutely no issues. I owned another full brother who again had absolutely no issues either. I plan to haul him to a clinic and get him scoped soon to hopefully get an answer.
We had one that burped and his breath after it was foul.
He was scoped and they found his stomach was very small.
It was recommended by Tuft's that he come off pasture - continuous grazing was overfilling his stomach and be put on a dry lot with small meals of mash. They basically said it was a matter of time before he had a crisis - he could not consume enough calories to survive. Sadly, he kept losing weight and having gas colics and was put down about a year after the scoping.
I've noticed my horse burping occasionally in the past; definitely sounded like a burp, not a wind-sucking noise at all. This year it was thought he might have low grade ulcers due to Cushings. He's now on Uckele's G.U.T. and finishing meals again. Haven't noticed any burping but then it wasn't happening regularly. So, he burped and had ulcers. Not saying all burpy ones have ulcers, but this one did.