Shouldn't be a problem as long as the inside of the trailer doesn't have any potentially harmful bits sticking out and the floor is strong enough to carry the weight - but make sure the rear door is safe and the sheep can't break out - also, you are supposed to have ramp gates, but a couple of hurdles will do the trick.
I suggest you use the power washer at the abattoir to clean out; domestic appliances are simply not strong enough. Good luck
Farmer
