The topic of forage demand comes up frequently on these pages. We know that one AUM will sustain one wild horse, one cow/calf pair, two wild burros or five domestic sheep for one month. The forage demand of one wild horse is 12 AUMs per year.
The land use plan for an HMA must allocate 2,184 AUMs per year if the AML is 182.
But you can’t write the forage budget until you know how much forage is available.
In some of the environmental assessments for wild horse management actions, forage supply varies from 12 to 18 acres per AUM per year.
Let’s pick the midpoint. A wild horse would need access to at least 12 × 15 = 180 acres to survive. Round the result to 200 acres.
Therefore, a stocking rate of five wild horses per thousand acres should be sustainable.
Why does the government limit wild horse herds to one animal per thousand acres?
What happened to the other four horses (80% of the carrying capacity of the land)?
Take a guess.
Western Horse Watchers Association 
The government says 1 cow per 20 acres and they will only give small farmers loans for that ratio. So, do theses cattle ranchers not know about rotational grazing? Why are they not required to rotate and meet the head / acreage count? They need to buy hay like the small farmer or lesson there herd because obviously they have poor herd management skills and are not managing our national lands and resources respectfully and responsibly.