the idea is basicaly a self propelled self loading feeder wagon , the auger / loading arm starts at the bottom of the pit face & slowly works it's way up & down ,& it should leave a clean pit face minimising wasteage ,like a sheargrab would leave it, unlike a silage / dung grab whick tears the silage out , letting air into the silage
there is a goat farm behind shepton mallet showground that has one but i have only seen it feeding , not loading . there is also another earlier model working up on the mendips, but because there were problems with the loading arm the farmer has taken it off & just uses it as a SP feeder which in fairness still releases a tractor to do other things