Best dog for dealing with Boar?

Ok I asked a similar question about 30 minutes ago and quickly realized I asked my question the wrong way so hopefully this time I can be more clear. Im a farmer, I live in the middle of nowhere and my definition of a pet is a horse thats north of 1000 pounds. Anyway I raise bison which is a pretty nice animal to raise since its a pretty brave/dumb animal that runs at a herd of bison thinking its gunna take em down. Well apparently boar are said animal. The boar have decided to move into my 1500 acres and apparently they think its good sport to try and kill my bison. Yes I know a dog is no match for a boar and that I need a rifle (Which I have). However I cannot be everywhere on 1500 acres all the time so what I'm looking for is the best dog to essentially guard the herd and raise enough heck that the herd can get away until I can get there. I had considered mastiffs but I've heard they will "target" horses. I'm open to everything from pit bulls to Irish wolfhounds the better half is wanting me to put Black Russian Terrier on the list but I'm open to anything except for great danes (I had a bad experience). Also I am planning on getting more than one dog (read: 5+) in case someone is concerned that I'm entrusting a single animal to guard against a venerable army of razorbacks. Thanks in advance.