See its all fun and games in the city, but in the countryside its a bit more serious. I have socialised all my dogs from a young age, even the little russell played with my neighbours kittens as a pup. Then one day things got serious and suddenly its wasnt playing, it was nipping and trying to pin down. I saw something in his eyes change (an evil glint), and from then on he chased any cat he sees. So i would argue that its not under socialising that does it. My gsdxstaff has caught a baby bunny in his mouth and spat it out again not knowing what to do with it. Before you think 'thats great' both he and the russell pulled down a sheep two years ago and started eating it. Not so funny. Luckily as i was honest and went straight to the farmer (it wasnt dead and i wouldn't see it left in pain) he charged me for it, but warned me that when the females are pregnant (like now) the whole flock can abort, and that would not be good.
I have to admit i was extremely lucky as most farmers would have ordered the dog to be put down (i may have omitted that there were two, i only blamed the russell as i knew that a farmer would think the sheep was perhaps lame for a such a little dog to take it down, but in my defense i would have done anything to preserve the dogs, even left the country (i'm not kidding).
Anyway after all that, i don't trust the dogs one smidgeon around livestock (although they adore my horse). The bigger one, Jaz, is obedience trained, and i can 'heel' him around sheep, and he won't touch them. But put him with Prinz and its like he switches off his hearing (i do know that Prinz thinks he has authority over Jaz even though Jaz is bigger, so Jaz could just be following the leader) Anyway, i now have a controversial static shock collar that the little russell wears if we go anywhere (i do alot of hill walking) and who wants the dog on the lead all the time. I have had to use it once for sheep chasing and it worked a treat. For those not familiar it gives out a static shock like we get off the car or tv. It doesn't actually hurt (tried it) but more distracts the dog. To make it work efficiently you cant just use it, you have to relate it to negative experiences. Anyone familiar with clicker training will know that the clicker itself means nothing, but using it with positive rewards makes the noise suddenly very appealing. Its the opposite with the collar, you make it mean 'no' to back up a command that is being ignored. I bought hamsters and taught him to leave the cage alone (he ignored me) and i would 'zap' to back up my verbal command. To me it is an extreme measure, and in the wrong hands could be disastrous, however it has worked a treat and more sheep are alive because of it.