I've found that a number of cattlemen and other livestock producers really don't understand the difference between stocking rate and stock density. Some tend to use the terms interchangeably, though they're actually two very different concepts, with very different effects on the pasture-livestock system.
Simply put, stocking rate is the basic relationship between livestock and the forage resource. It's the number of animals on the entire grazing unit for the entire grazing season. Think of stocking rate in terms of either animals per acre or liveweight per acre. If we have 100 acres and 100 yearling steers weighing 700 lbs., the stocking rate is one steer/acre or 700 lbs. liveweight/acre.
Using an appropriate stocking rate for your forage resource is the first step in managing a sustainable pasture or range operation. An acre of land will only produce so much forage and support only so many livestock. Stocking rate affects the pasture's overall productivity, species composition, likelihood of soil compaction occurring, individual animal performance, and a host of other factors in the pasture-livestock relationship.
Stocking rate is often used interchangeably with carrying capacity, which is also incorrect. Stocking rate is the number of animals on the pasture, while carrying capacity is the number of animals the pasture will support year after year while achieving an acceptable level of performance.
Yes, we can increase carrying capacity via grazing management that more efficiently utilizes the forage resource. But we can't automatically double or triple carrying capacity by embracing the newest fad in grazing management.