Work out grazing land requirement instantly with clear inputs, formula shown and shareable results.
Grazing area is annual forage demand divided by usable forage per hectare. Only part of what grows can be eaten — the take-half-leave-half rule puts utilisation near 50% for sustainable grazing, because leaving residual leaf area is what allows the pasture to regrow.
Grazing demand
Annual demand = animal units x daily intake x 365
Land requirement
Usable forage = yield x utilisation %; land = demand / usable forage
Conventionally a 450-500 kg cow with calf, consuming about 11-12 kg of dry matter a day. Other classes are converted with animal unit equivalents — a dry cow is around 0.9, a yearling 0.7, a ewe 0.15.
Grazing beyond about 60% removes the leaf area the plant needs to regrow, shifts the sward to weeds and shallow-rooted species, and cuts long-term productivity even though it feeds more animals this season.