I wish I had never taught Bo to chase a ball and bring it back, that is all he wants to do, now you throw the ball Bo chases it and Culotte, Ziggy and Bryony chase Bo.
I think if I tied a ball onto some of my sheep Bo would be an exelent sheep dog

I'd like to know more about predatory sequences too.

Jed will chase any live game and is totally focused on the chase so it's difficult to call him off but he's not interested in chasing toys about.

Flynn loves to chase toys and will bring them back but although he will chase game, he's not overly bothered about it and tends to leave that to the collies.

Jessie will chase rabbits and hares but doesnt chase cats or foxes or anything else really yet she is totally obsessed with playing fetch.

I will post this evening, in the interim you may be interested in considering a RELATED issue re sheep.

I have posted this link in order to demonstrate that a) not all sheep chasers are the same and b) and to demonstrate the weird anomalies that exist in the animal world.

http://www.dogpartnership.co.uk/livestock.htm

Jake loves to play fetch, and he has a high prey drive... I think he just loves the chase...

It seems to be a self-rewarding activity.
I think the dog succeeds twice at least in the game.
Chase / pounce. Pleasure - success in getting object.
Give back ball in expectation of another chase - pleasure in partnered activity.
Plus approval from owner. And the soothing effect of the object in the mouth.
What`s not to like?