Unless your dog has grown up as a pup seeing chickens milling around the garden the desire to hunt and kill them as prey is going to be huge when exposed to them.

Sorry if you are going to be offended but IMHO you need to be a bit dim to assume that a dog that has not met a live chicken before will simply think it a new friend/playmate.

In three years I've had one problem with one of my dogs chase and injure a chicken (it was a near neighbours) that popped out of a hedge while we were walking in one of our fields. The chicken lost a large lump of skin so rather than playing chicken doctor I broke it's neck, the resultant infection would have been worst there was no way it would have recovered if left alive.

My dogs are not chicken killers and are quite happy to sit in the den with our chickens milling around and pecking the scraps from the dog's bowl. But these chickens are not jumping out of a hedge at random but are seen every day. The surprise out in the field while walking triggered the prey response.

Do not feel guilty about the injuries caused it was in the dog's nature and unless you knew that before the event it could not be stopped. The lesson is learnt and now you know to secure the dog/garden.

There might be mileage in addressing the prey drive by exposure to chickens, not something I've had to try but have had dogs live along side loose chickens with no problems. I can think of a few ideas to help wean him off the novelty but it takes chickens and a lot of time. The old farmer's wives tale is to tie a dead chicken around a dog's neck for a few days. (not something I suggest trying - I have to add this proviso otherwise I get more hate mail)

Sorry if you feel these words are not supportive but I hope it might help in your situation.

Edit: Are long legged JRT as good a diggers as the short ones?

In my house chickens are dog food and although he has never seen a live one (partly through luck but mostly by design) I have no doubt that if he did, the chicken would not survive.

The instinct to chase, catch and kill small furries and birds is hard wired into every dogs brain and in terriers it is exceptionally intense, yes they can learn to control it if they are exposed from an early age, but it is still there nonetheless. I have a friend who has three rotties and a JRT who live happily alongside chickens and geese, but they have done so since they were 8 weeks old and still have to be supervised. I can understand that you thought you were just introducing a new element into your dogs life but unfortunately you underestimated his prey drive, which is something that is going to be very difficult, if not impossible to train out of him.

Management is your only option, keeping him away from chickens is the ideal but if that is not possible and there is the possibility of him finding his way to them again then you might want to consider muzzling him in order to limit the damage he can do.

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