Horse Gltich

When I logged out of the game while riding a horse, in a 1 deep "lake", then logged back into that world there was an identicle horse right where the horse i was riding was. It had a saddle that i could take off, as well as ride it. It also dropped my fps from 40 to 10. I logged out again (not riding any horses) and logged back on, both horses were still there, rideable, and could remove and place saddles/armor on it.