Salatin bases his farm's ecosystem on the principle of observing animals' activities in nature and emulating those conditions as closely as possible. Salatin grazes his cattle outdoors within small pastures enclosed by electrified fencing that is easily moved each evening in an established rotational grazing system. Animal manure fertilizes the pastures and enables Polyface Farm to graze about four times as many cattle as on a conventional farm, thus also saving feed costs. The small size of the pastures forces the cattle to "mob stock", or to eat all the grass.