The Salt Lake Field Office authorizes livestock grazing on approximately 2.4 million acres of public lands. In total, the Field Office manages 153 allotments. Livestock grazing allotments range in size from less than an acre to 230,000 acres. These permits are held by 223 different individuals or corporations for a total of 175,191 Animal Unit Months (AUMs). Grazing permittees purchase AUMs of livestock forage. An AUM is the amount of forage needed to sustain one cow and calf, five sheep, two burros, or one horse for one month.