My puppy has a chewing/eating problem. He chews on everything and anything, to the point that he has landed in the emrgency room twice. What should I do?

I'm writing on behalf of one of my Shetland Sheepdog puppies - well, now he's almost a year old - whom I co-own but who lives with his primary owners in another state. This puppy has a chewing/eating problem that I am very concerned about. He chews on everything and anything, to the point that he has landed in the emergency room twice. The family has tried keeping him somewhat confined (x-pen) when they can't directly supervise him; they have muzzled him when out of doors but he has literally eaten through 5 muzzles of different sorts. He can't be left unsupervised at all without having him eating or chewing.

The family has a large yard. The puppy seems to have plenty of exercise and is taking regular agility lessons; he will also be (if he isn't already) taking herding lessons in addition to learning how to help with the 6 sheep owned by the family. He is one of 4 Shelties in the household, none of whom exhibit this behavior - nor have any of the other puppies that I have ever bred. This puppy is unneutered - we hope that he has the potential for the conformation ring and possibly for breeding - but I do wonder if neutering would have any effect on this very undesirable behavior. Someone said it is a form of displaced aggression and that neutering would help to diminish it.

Any suggestions would be greatly appreciated.

Cathy