Don't give up hope! Our Spanish Water Dog was also 3 when we first got hens. She was a nightmare, barking and generally running round and around then hen house, barking madly for ages. Eventually she got, if not bored, then at least calmer. At this point, we started to let the girls out but always supervised the dog when she was in the garden. We rewarded the dog when she ignored them and told her off if she tried to give chase - and put her immediately inside the house. Now she is truly indifferent and we are happy for her to be in the garden on her own with the hens. If anything, they menace her rather than the other way round!