I like to take pups to stock fairly early to see if they have it or not. If they exhibit signs like in the picture then I will not take them to stock for at least a couple of months when I will then start them on puppy stock training. These are 3-1/2 month New Zealand Heading Dog X Border Collie. You can see some pictures of these future super stock dogs at
www.flickr.com/photos/redpale09/5057672145/
www.flickr.com/photos/redpale09/5057672145/