I use Zabre, turns out there junk like every thing else they sell at the local fleet store. If I have a problem now with them pushing on the fence I'll plug it in. I have a 100 mile fencer hooked into about 600 feet of wire, it hits them pretty good. If I hook it up to the 10 acre pasture it doesn't work as well. It seems like if a twig or a piece of grass is against it , thats all it takes. Could be my ground too. I only have 2 six foot copper rods in the ground tied together with barbed wire.
That reminds me, My wifes nephew used to touch the fence for beer. They would have a party next door, and every ten minutes he would ask for a beer, and I would tell him to touch the fence, he was desperate for beer so he would touch it. Makes for a good tester and some cheap entertainment. ( he was standing closer to the ground rods)