I tried To breed some first x herder greys a few year back but the bitch didn’t take. Brought a herder bitch in and had her for a little over a year bloody nice bitch and a pleasure to be round. She was a failed man worker didn’t make the grade for some reason or another. The out and out speed for catching most bolters wouldn’t be there but I don’t see any reason why one wouldn’t make a great marking dog as with all dogs there’s some bolters they would catch and some they wouldnt.