We have a young horse going under saddle that we occassionally hear a burp, usually when standing quietly while being ridden. His weight is good, and his management should not be a contributor (out 24/7 with grass,hay and a friend) Not a stressful life.
He did come to me 1 1/2 years ago from a situation that could have contributed to ulcers then ........
I too had a burper. He was a cribber, but also had to be tube fed as a very young foal. I always wondered if the tube feeding contributed to being able to burp more easily than other horses, as he was never more gassy at the other end (which I assumed he would be if he was simply gulping air while cribbing.). Maybe having the tube passed so frequently mildly damaged the esophageal sphincter?