Saying that your cattle dog chases anything is akin to saying that your goldfish swims! The behavior you’re describing is called prey drive, and certain breeds have higher amounts of it than others; herding breeds (yours) winning first place in this category. Step one – put the vacuum out of sight! He shouldn’t be allowed to obsess about it all day long. If he decides to camp outside the door where the vacuum is, then either confine him so he can’t get there or put the vacuum in another place that he can’t get to (the garage?). But now, he has a hole in his day – vacuum cleaner stalking being over with – and either you can fill it with something that provides an outlet for his instincts (exercise, herding lessons, obedience or agility training), or he will (standing on the couch and stalking the cars that drive by your window, anyone?). As for chasing the vacuum when it’s on, until you have a solid “down and stay” it’s best to confine him to a place that he can’t even see when it’s in use. Once the obedience is solid, put him on a leash and practice having him lie down first in the presence of the unplugged vacuum. Gradually work up to him being able to do that while it’s ‘on’ but not moving, and eventually graduate to him tolerating it when it’s on and being used. However, that’s just fixing a symptom, not the issue itself. This is a herding dog, and if you fail to meet his needs to run and chase, his frustrations could potentially escalate and turn into new even more dangerous behaviors.