In survival if you went on a horse the experience bar would turn in to a stamina meter fot the horse but if you step of the horse your experience bar would be gone and you would not be able to see the progress from the level nor the level it self.
This happened by following these steps
1 tame a horse.
2 put a saddle on the tamed horse.
3 mount the tamed horse by right clicking it with the saddle on it.
4 Hold the space bar to charge up the stamina bar of the horse.
5 press the left shift (default button) to dismount
Notice the you don't have the experience bar anymore but when you ride the horse the stamina bars does appear but if dismount it it does not bring the experience bar back up I tried mounting and dismounting a few times but it didn't work. Even if you exit the world and load it again the glitch stays there. This was my bug report I hope you fix this bug before the 1.6 pre-realease and the official Realease