National Drought Mitigation Center

Inventory Herd

Current mix of "core" and "disposable" animals

A balanced operation is:  (1) A livestock enterprise that provides sufficient feed and forage resources during each season to promote continuous satisfactory maintenance and production of its livestock and game. (2) An operation that integrates the kinds, classes, and numbers of animals (livestock or wildlife) to effectively use available forage resources to maintain continuous, sustainable production. (3) An operation that integrates various livestock, wildlife, and recreational enterprises which most effectively uses available forages and other range resources to maintain continuous, sustainable production.

Calculating Animal Units

Reference: Doing the Math: Calculating a Sustainable Stocking Rate, NDSU Central Grasslands Research Extension Center

An animal unit (AU) is one mature cow of approximately 1,000 pounds and a calf up to weaning, usually 6 months of age, or their equivalent.

The table below gives some common Animal Unit Equivalents, or AUE's, for other types of livestock, or cows weighing more or less than 1,000 lbs.

If the average weight of your cows is 1,284 lbs, the AUE is 1.284. Each one of your cows will eat as much as 1.284 cows.

Approximate animal unit (AU) equivalents for livestock and wildlife species other than cattle.  Divide average mid-season weights by 1,000 lb to estimate AU equivalents for cattle.

Kind/Class of Animal

Animal Unit (AU)

Saddle and Pack Horses


Two-year olds

Mature horses






Ewe (mature)

Ewe and lamb pair

Lamb (weaned to yearling)

Lamb (yearling)









Goat (mature)






Deer (white tailed, mature)

Deer (mule, mature)

Antelope (mature)

Bison (cow, mature)

Bison (bull, mature)

Bison (herd average)










Feed Needs

An average 1,000-lb cow will eat roughly 26 lbs of oven dried forage per day (or 30 lbs of air dry forage per day). This is also known as an Animal Unit Day.  The pounds of feed needed to meet an animal's daily requirement is usually calculated by taking 2.5 to 3 percent of the animal's body weight.

An animal unit month is the amount of feed required to sustain a 1,000 lbs cow and her calf (1 AU) for one month, or roughly 780-800 lbs of over dry forage (calculated as 80% of body weight).

The amount of forage required by an animal unit for 1 year, is equal to 12 AUM’s. The NRCS uses 9,490 pounds of oven dried forage as required pounds of forage to equal an animal unit year.

Current stocking rate

Stocking rate expresses the number of specific kinds and classes of animals grazing or utilizing a unit of land for a specific period of time. Stocking rate may be expressed as animals per acre, hectare, or section, or the reciprocal (area of land/animal). When dual use is practiced (e.g., cattle and sheep), stocking rate is often expressed as animal units per unit of land or the reciprocal.

There are different ways of expressing stocking rate for a given herd of livestock but the most commonly used are:

Pasture stocking rates can vary widely and in past research, values ranged from 1.3-2.0 acres per AUM. One current recommendation is a conservative value of 1.4 acres per AUM (Nyren et al.1991) in the North Central region.

The number of acres recommended per AUM would be higher in the drier, less productive regions and lower in the wetter, more productive regions.

Management Intensive Grazing may also affect acres required per AUM.