in my inexpert view, but with sheepdogs young ones, and seeing the instinctive reaction of breeds of sheepdogs at their herding tests recently in feb...i would say...

the sheepdog is not a killer, my dog chases, predatory, anything that moves fast attracts as said here...but my dog let GO of even small live mice she unearthed...and sheep...she will nip but not bite to kill...

and the most amazing reaction i saw nad have on video on my webpage...a 6 month old labrit berger des pyrnees...the sheep played DEAD....as they can do to avoid being rounded...and the dog...focused on the alleged injured sheep apart from the flock without aggression trying to lift it in fact...

CSAU CANT - FEE NOIRE,belgische herdershond,chien de berger belge,belgian shepherd,groenendael,France

the video of yout ube i put up of this pup...
YouTube - labrit,chien berger des PYRENEES CANT Biscarosse.MOV

now my latest puppy...a belgian shepherd...and i regret to say i saw NO GERMAN SHEPHERDS at the sheep herding tests...and i lvoe the breed...minus hyenna deformed hind legs the standard ruined...altdeutsche schaeferhund i may get next...when my young dogs are sheep herding expert trained...

well look at a 2 month old pup...barking yes...but not aggression....trying to control...confront...
YouTube - falcon pup age 2 months may 2011 confronts goats alone.AVI

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"me and you and a dog named not BOO but BLACK FAIRY...travelling and a living off the land ! great song that !"

http://www.belgische-herdershond.com

The problem is the stress that being chased puts on the livestock, they may not be killed outright, but repeated chases may kill the animal.

If you think about it, a reason for the BC's dominance as the Brit herding dog, is it's gentle stand offishness and fine control, pointing & giving the "Eye" to unnerve the sheep. It stalks, rather than chases often, though when ignored escalates, in trials dogs that "grip" are disqualified even if it is "justified" to avoid gripping being part of day to day work. The lifting of sheep off boundaries to gather them, does in effect require a drive to chase and loose strays most definitely learn to stay in the flock, rather than be a highly visible target.

I would like to thank everyone for their comments, which have been helpful..

As mentioned earlier I was relieved that nothing untoward happened to the lamb, and having done my smallholding course and lambing course, I am even more aware about the damage chasing can do, let alone catch a sheep..

I was more curious as to why she didn't attack, having seen her catch a rabit - I know that she is more than capable of killing something.

As for recall 95% the time it is perfect, unfortunately she was intent on chasing the sheep... and no amount of recall or treats was bring her back.

I am obviously even more vigiliant than I was, like many have said you can never be too careful and I would hate for something to happen to either livestock and because of that my dog...

Thanks again.. :-)