The wolves will easily kill pigs, even a big boar or sow. Even coyotes can do this. Pigs don't do team work. Wolves do. Wolves bring down buck moose, muskox, etc. Pigs don't stand a chance.
I know. I have wolves. Wolves guard our livestock. Your best defense against wild wolves, two-leggers, bear, coyotes and other predators is a combination of good fences and a good pack of your own. A single dog won't do. It takes a pack.
See:
http://sugarmtnfarm.com/animals/dogs/
If you don't have good fences or your own pack to guard your livestock then consider bringing the livestock in close to the home base at night.
-Walter