Resources for Calculating Stocking Rate and Carrying Capacity
To use the resources below, you will need to know the number and type of livestock you plan to graze, for how long, and the approximate amount of forage you have available. The number of animals, per area, for a certain period of time is known as stocking rate.
Understanding Forage Production
Demand Cannot Exceed Supply
Regardless of grazing strategy (rotation, continuous, etc), demand for forage by grazing animals cannot exceed supply. Supply can be challenging to calculate in Colorado, because it changes year to year. For example, in one study, the same pasture produced around 200 lbs/ acre in 2002, 1300 lbs/ acre in 2003, and ~700 in 2004, due to drought conditions. There isn’t just one number on rangelands in Colorado that will be appropriate to use every year.
If you don’t know how much forage you have available, below are resources:
- The Dryland Pasture Condition Assessment and Guidelines (below) has approximate values by region on pages 4-5.
- Web Soil Survey allows you to zoom to your area of interest, and get estimates of production for wet, average and dry years.
- The Rangelands Analysis Platform is a new tool that calculates an estimate of productivity for a specific area going back to 1986.
- Or, contact one of us.
Harvest Efficiency Rate
“The grass doesn’t know what bit it.”
In rangelands, we estimate that only a portion of total forage will be used by grazing livestock. This is to maintain long-term grass and forage health, as well as provide for use by wildlife and loss to trampling. Historically, range managers suggested ‘use’ be set at 50% of total forage, or “take half, leave half,” based on early studies where grass recovery and resilience declined drastically beyond 50% use (Crider, 1955).
Today, many rangeland managers estimate ‘allowable use’ as 25% of total forage produced. This is to allow enough forage for the plants to regrow and thrive, and for grass/forage that may be consumed by wildlife, and because efficiency of harvest for livestock decreases as you exceed 40% use. What this means is that in calculating available forage, we plan on having livestock use only 25%-30% of available forage because consuming more would reduce the amount of regrowth by plants, and leaving forage behind can help protect the land from erosion and ensure that it is productive in the future.
Tools & Calculators
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Grazing Calculator (Free app) from North Dakota State
A downloadable app that you can use to calculate stocking rate based on your input values.
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Online Forage Calculators
These calculators explore the number and type of livestock your land can support based on forage need and the forage available.
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Estimate Stocking Rate, Expenses, and Total Return
Use the below calculator, Matching Cow Size to Available Forage, by CSU Agriculture and Business Management Economists, Jesse Russel, Jeffrey E. Tranel, R. Brent Young and Norman Dalsted, to integrate stocking rate with economic information.
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Dryland Pasture Condition Assessment and Guidelines for Colorado Small Acreage by J. Cook, D., Nosal, J. Rizza, S. Bokan and E. Lockard.
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