We have Greyface Dartmoor Lambs behind an electric fence. We thought the wool might insulate them but I guess not since none of them will go anywhere near it now! Never seen one touch it (one of our big rams did and he jerked back very quickly). Now our problem is getting them out of the field! If the fence is there, even lying flat on the ground they will not go anywhere near it - you need to roll the darned thing way back. The only alternative is to pick them up and throw them over (not literally!) or if they are larger we have to cover their eyes and reverse them over it so they simply don't see it!
Having said all that, I wouldn't trust it to keep a ram from ewes - lust conquers all!!