One of the fundamentals of raising cows is the balance between the number of cows in a given area versus the ability of the land to recover. You always want slightly fewer cows than the land can handle so it will have adequate time to reseed and regrow.
Stocking rate is a measure of animals assigned to a grazing unit for a period of time. This is often expressed as the number of cows per acre or the number of acres per cow in areas that have less grass. The average weight of the cows is also important because obviously a 500 pound cow eats a lot less than a 1000 pound cow.
The standard animal unit (AMU) was developed as a consistent way to express stocking rates. Technically a AMU is “the forage requirement for maintenance of one animal unit for 30 days.” But just to confuse things some folks use a 1100 pound lactating cow (producing milk requires more food so this is the most conservative view) while the majority of producers use a 1000 pound pregnant cow with an average body condition (5).
In reality things aren’t so simple. Stocking rates (or carrying capacity) varies a lot with the state of the land and the forage. Dry years and wet years obviously have different forage levels so the carry capacity of the land can vary dramatically. And using an average can be misleading because the land is a lot different in summer and winter.
Cattle producers need to understand all that, have ways to measure the land at the time and in the near future, and have clear goals in mind regarding their livestock. Balancing all of that is difficult but is a major differentiator favoring the producer who works hard at it.
And you thought raising livestock wasn’t that hard!
A real expert on this subject is Jim Gerrish. He has a great book called Management Intensive Grazing you can get HERE.