Could be - get an exacto and cut it all off then reharness and walk them around a bit...any better or worse? You can always get more duct tape and put it back...duct tape comes in some really awesome ghetto colors nowadays - camo, hot pink - leopard...HAHAHA!
By they way, your donkey is adorable. I hope one day to own a mule. A gaited mule, in fact ..one I can ride and drive.