An electric fens does a good job of keeping most chicken thieves at bay. A 5 wire fens 3 foot high and with a strong and well grounded charger will repel almost everything that touches it. The exception is when the varmint fails to make contact with the fence or makes contact at top speed. Space the bottom wire 3 1/2 inches off the ground and the second wire the same distance from the bottom one.
You can also inter space hot or positive wires with ground or negative wires like this: +
-
+
-
+
-
+
-
+
The idea is to force small chicken thieves to contact both a hot or positive and a negative or ground wire while trying to get through your fence. This will complete the circuit and give the thief a jolt to remember. This also closes up the fence and discourages your chickens from giving the fence a try. Dogs (yours included) that touch your fence will likely be repelled from that spot for the rest of their lives. Even after the fence is removed they will hesitate or refuse to cross that line. One learning experience with an electric fence is enough for most dogs. Do be prepared to either weed eat often under the fence during the growing season or else keep the grass and weeds burned down with Round-Up. If you have large trees like oaks, pines, or maples, the little twigs that these trees shed can be a problem if one hangs on a wire and provides the electricity a better path to ground. Snow is a problem for the same reason. Since mammal predators are all 4 legged and they don't wear Nike's, predators are even better grounded than you or I. Most predators that makes contact with your fence will discover that they have pressing business elsewhere. It is almost impossible to build an electric fence that will stop every weasel because they are already so low to the ground that they are unlikely to contact the bottom hot wire at every spot and if you move the bottom wire to close to ground you defeat the fence.
If you live in a arid or sandy area the effectiveness of an electric fence decreases in proportion to how dry the earth is. The use of inter spaced hot and ground wires shown above will correct this problem. An electric fence can also be a fire hazard in arid areas if you don't keep vegetation under control 3 or 4 feet on either side of the fence.
Coyotes can be a little harder to dissuade and they may learn to vault the fence or if hungry enough pin their ears back and run over or through your electric fence. This is a prime reason that a catch and release mind set should be discouraged among Back Yard Chicken fanciers. The varmints play for keeps, they don't play tag your it, or dodge ball with your chickens. Catch and release varmint breeding only helps develop a super predator with more disdain for humans, a greater love for our poultry, and advanced degrees in how to catch poultry while evading the pitfalls we put in their way.
A good lighting arresting system is a must especially in the South East or Mid-West and be sure that you keep an extra charger fuse or two laying around. Finally everything to build an electric fence is cheap and easy to install, but do splurge and buy a little more charger than you think that you will need.