An optimum grazing pressure is one in which available forage matches animal needs; this is analogous to the quantity of forage offered daily to animals in confinement when rations are balanced. (The Pennsylvania State University)

The different grazing pressures were obtained through different stocking rates, adjusted every 21 d according to forage mass, predicted forage production rate, and an estimated forage allowance of 10, 15 and 20 kg dry matter (DM) heifer-1 d-1 for high, medium, and low pressures, respectively. (American Society of Agronomy)

Stocking rate and annual average grazing pressure (with or without account for feral animals) did not appear to be, in themselves, good indicators of sustainability. Rather, the sustainability of different areas/systems and the impacts on sustainability of changes in management, e.g. stocking rates, may be assessed better through calculating year-to-year variability of the feed base, and periods of critical grazing pressure. (cababstractsplus.org)