A useful term in determining stocking rate is the animal unit (AU). An animal unit is a 1,000-pound cow with an average dry matter forage requirement of 26 pounds per day. The animal unit equivalency of various classes of livestock are as follows:
• A 1,000-pound cow with calf is equal to 1.0 animal unit.
• A 1,000-pound dry cow is equal to 0.77 animal units.
• A 600- to 900-pound heifer is equal to 0.6 to 0.8 animal units.
• A 1,500-pound bull is equal to 1.1 animal units.
• A 130-pound ewe is equal to 0.20 animal units.
• A 75-pound weaned lamb is equal to 0.12 animal units.
• A 175-pound ram is equal to 0.25 animal units.
• A 70-pound nanny is equal to 0.17 animal units.
• A 35-pound weaned kid is equal to 0.10 animal units.
• A 125-pound billy is equal to 0.25 animal units.

However, animal unit equivalents will vary significantly depending on the weight and physiological stage of the animal.