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).
|Kinds/Class of Animal||Animal Unit Equivalent|
|Cow, with calf||1.00|
|Cattle, 1 year old||0.60|
|Cattle, 2 year old||0.80|
|Lamb, 1 year old||0.15|
|Kid, 1 year old||0.10|
|Deer, white-tailed, mature||0.15|
|Deer, mule, mature||0.20|
|Sheep, bighorn, mature||0.20|
Source: NRCS National Range and Pasture Handbook