There is absolutely no reason a dog can't be trained out of a certain behaviour.
It just takes patience.
But most behavioural problems originate with the owner
I say that, because chasing stock is usually a sign of boredom (unless its a Collie

).
First you need to look at why he suddenly decides to go for a skid and chase the stock....
Is he bored??
Dogs need ALOT of mental and physical stimulation, if you aren't supplying that stimulation, they go amuse them selve's. (unless its a Labrador, it'l just go eat something instead

)
It might seem obvious, but if a dog is tired, it's not going to go chase the stock for fun is it??
He would much rather be chill-laxin in the shade watchin you do the hard work
That should solve the problem
But you do also need to teach him that he is not allowed to chase the stock for enterinment.
First you need to train him on a command to "stop".
Teach him that what ever he's doing, playing, eating, walking what ever, that when he here's the command to stop, thats it, he must stop.
Once you think he's got the hang of that, step up the repercussions for failing to stop.
Set him up so you can catch him in the act of some other bad behavior, give him the command to stop.
When he doesn't stop, boss dog (thats you

) gets very unhappy, practice your growl and dominating stance and make him feel very small and threatened.
You can then set him up for a fall with the stock. Do it in a controlled environment, give him the command to stop, wneh he doesn't, you know what to do.
Depriving him of some of his perceived dominance will also go along way to preventing his urge to go hunting the stock alone with out the boss dog as his guide.
Keep him tired and entertained, easiest way to get rid of boredom behavior.
Doesn't always work though, I lost a good dog because I couldn't train her out of jumping fences and she ended up out on SH1
