ChaoSS - Yeah, I love me some electric fence. When I caught the neighbor's newfie in the chicken coop I put the fear of God in him, swatted him on the head and screamed and yelled and chased him out, he hasn't so much as looked in the general direction of the chicken coop since. We have an 8 foot fence around it, but our little ameracauna hen can fly out. And she does. She's out every morning with the dogs (not like we can prevent it until we get a hotwire over the top) and he won't even look at her. At this point if she gets eaten it's her own stupid fault, since she's escaped him TWICE and should know better so whatever. I do think a hot wire will keep him away, though.
Hotwire will stop a newfoundland. The dog may have to get zapped a couple of times first but it learn to stand off. Dog must be getting zapped and using a step above the minimum Joules used for dogs should be considered.
My dogs will also be persistent trying to get through fence when a raccoon is on other side but once they get a couple of zaps the dogs recover their senses and go to opening I have for them to get around fencing.