animal units

March 10, 2015 Print Friendly and PDF

An animal unit is 1,000 pounds of grazing animal. Ruminant grazing animals consume about 2.6% of their body weight per day; therefore, an animal unit consumes 26 pounds of forage per day or 780 pounds of forage in a month (1000 pounds of animal x 2.6% x 30 days = 780 pounds). Thus, the term "animal unit month" (AUM) refers to the amount of forage an animal unit consumes in a month. This measure of forage demand can then be converted according to the relative demands of different animal classes.

Below are some common equivalents to animal units: (Table 1).

Animal Unit Equivalents
Kinds/Class of Animal Animal Unit Equivalent
Cow, dry 0.92
Cow, with calf 1.00
Bull, mature 1.35
Cattle, 1 year old 0.60
Cattle, 2 year old 0.80
Horse, mature 1.25
Sheep, mature 0.20
Lamb, 1 year old 0.15
Goat, mature 0.15
Kid, 1 year old 0.10
Deer, white-tailed, mature 0.15
Deer, mule, mature 0.20
Elk, mature 0.60
Antelope, mature 0.20
Bison, mature 1.00
Sheep, bighorn, mature 0.20

Source: NRCS National Range and Pasture Handbook

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.