I started UO with the renaissance disc and I remember there being an animal trainer outside moonglow inn..... just walked around near the door... hes not there...
This has come up a few times already and I think general consensus is that there was one there, but only in Trammel. We discussed it however and it's not out of the question to have one added down the road.
I played siege mostly and remember there being one there... could have been added later on or I could be wrong all together. But Glow was my main town on Siege and that's where I kept my horses :>