What stocking rate means
The stocking rate is the number of animals a pasture can feed for a given period without being overgrazed. Too many animals deplete the grass, expose the soil and lower next year’s yield; too few waste forage. The calculation balances the forage available against what the animals eat.
The formula
Animals = (area × forage yield × utilization) ÷ (grazing days × daily intake per animal)
- Forage yield: pounds of dry matter (DM) produced per acre over the season. Improved pasture often produces 3,000 to 6,000 lb DM per acre, native range much less.
- Utilization: the share of the forage that animals actually eat. The rest is trampled, soiled or left to protect regrowth. The classic rule “take half, leave half” means 50% on pasture; rangeland is often grazed at 25% to 35%.
- Daily intake: about 2.5% to 3% of body weight in dry matter for cattle, often taken as 2.6%.
Example
40 acres producing 3,000 lb DM per acre, grazed at 50% for 180 days by cows of 1,200 lb:
- forage available: 40 × 3,000 × 0.5 = 60,000 lb;
- intake per cow: 1,200 × 2.6% ≈ 31 lb per day, or about 5,600 lb over the season;
- the pasture can carry about 10.7 cows, or about 3.7 acres per cow.
Animal units
An animal unit (AU) is a 1,000 lb cow, with or without a calf, eating about 26 lb DM per day. An animal unit month (AUM) is the forage one AU eats in a month, about 780 lb DM. Other animals are converted: a 1,200 lb cow is about 1.2 AU, a horse about 1.25 AU and a ewe about 0.2 AU.
Adjusting the rate
- Drought: forage yield can fall by half or more. Have a plan to destock, buy hay or rent extra pasture.
- Rotational grazing: moving animals between paddocks with rest periods often allows higher utilization and better regrowth.
- Season: grass grows fast in spring and slows in summer heat; a single seasonal average hides those swings.
- Supplemental feed: hay or grain reduces the forage needed from the pasture.
Measuring forage
Clip and weigh the grass in several small frames, dry the samples and scale up, or use a rising plate meter or pasture stick. County extension offices and NRCS publish typical yields and stocking rates for local soils.