Depasturing land is, as you say, putting stock on land. Depasturising is not the term, but probably springs to mind because it is the process-minus the de-of heating milk to kill the bad bacteria. In the colonial period one paid a licence fee and stock assessment for the privilege of using Crown lands for grazing. If you look in the SA archive you may find a map of your ancestor's run GRS 11676, 5 volumes, and you may find it. Cheers Kevin Brewer