Hi
I don't now about minature schnautzers but have border terriers these are also small hunting dogs that would love to run of at the first site, or scent of prey (including sheep given the chance)
But now dogs should be of the lead untill you have trained them to have suficiant control over them, to get them to stop & return on comand. (sometimes they do get further than you want after instructed)
But then you can revert back to long leads & refresher training again to remind them.
I would not like to have dogs that could not go on a free run off the lead

karl