With colliex greys [1x] they need alot of success early on at catching. Once they have,they make great rabbiting dogs[day-night]. My 1x collie grey Bryn, has had 95 rabbits,3 hares, in the lamp, he caught them at 16 months old, not bad for a young dog. With young dogs [especially] 1x collie grey ,TRY and pick your rabbits at first , say 15-20. As been said , you will go very slow now with each dog. Take them out on there own, 1 to 1 and try them on some daft summer time rabbits, this is prob some times when you take on a older dog. Some times it works, and some time doesnt.
Stick with