I just wrote a thread about this same stinkin issue a couple days ago. Our one year old pup has tangled with a porcupine twice in the last month. Thankfully she didn't get more than 15 or so quills in her muzzle and we were able to pull the out ourselves.
Our two older dogs tangled with a porcupine a couple years ago and they had to go to the vet to get the hundreds of quills removed. Our vet bill was only $100 per dog ... that was awful, I'd have choked at $400!!!
Miltonchix -- you'd think they would learn.... most don't. According to my two vets out here ... almost all the dogs they see with porcupine quills are repeat offenders. Most of the dogs come back again and again to have quills removed from the vet!!
The only way that I know of to stop this behavior is to put up a fence to keep the dogs in and the porcupines out of your property. I'd certainly love to hear from anyone that's found another solution as I need it too.
amazondoc: I just wanted to edit this to respond to your good idea... our dogs are our livestock protectors. They have free run of our 40 acres to protect our other animals from coyotes, raccoons, etc. If they are locked up in a kennel - they can't do their job. Thankfully with our dogs running loose (on our property) we've never lost a chicken or other animal to a predator. A few years ago we did lock up our dogs at night and lost several cats to predators in a week's time! I won't lock them up again.