Im a total newb.. but Ill give some advice anyway, since I have been thru this lots with my *lovably* neurotic border boy n_n

First off... I strongly, strongly disagree with shock collars. they should only be used under supervision for training.. Ive heard of so many dogs becoming agressive and fearful because of them. Id also worry about them harming a dog if he is really worked up and barks a lot.

your dog is probably barking because he is either bored or feels his territory is being invaded. if its boredom, be sure to supply him with lots and lots of stimulating toys before you go.. Buster Cubes, cookie-filled kongs, nylabones, noisemaking toys, and hidden treats are always good. If he is barking due to territorial reasons, and he barks a lot, you should consider keeping him inside during the day... as its pretty hard to correct when you arent home. he could also just be frustrated by the fence barrier between him and the neighbors. you could always make a fenced run for him, maybe on the side of your house, where he cant clearly see the neighbors in their yards.

my dog likes to bark just to hear his own voice sometimes. he also barks avidly at the squirrels, birds, raccoons, and dogs that often pass by our fence on the street. to spare our neighbors, we just keep him inside while no one is home.. his area is our kitchen and family room, because the floors are hardwood and there isnt much to get into. We babygate the entry to the kitchen and family room, give him lots of toys and he is really good. our kitchen cupboards are already kidproofed and impossible for him to open, since I have a baby brother. If we're only going to be gone for an hour or so, we crate him inside.

if none of this works and he must be kept in the backyard during the day, citronella collars are probably a more humane way of dealing with barking as opposed to shock collars. they still arent a solution to the problem, but it will probably deter him from barking when hes in the back alone. good luck with your boy hope any of this works for ya!