by Brian Campbell, NRCS Grazing Specialist
There are helpful calculations available to help farmers design a new pasture system or avoid damaging existing pastures by not overstocking, overgrazing, or under-sizing. Grazing math can be used to answer questions like:
· How many animals can my pasture/paddock support?
· How many days will my pasture/paddock last?
· How many acres should my pasture/paddock be?
The calculations use some assumptions about (1) how much forage your livestock need to meet their daily dry-matter needs – based on the class of livestock; (2) how efficiently those animals can utilize the pasture – based on how intensively livestock are rotated through paddocks (i.e. pasture subdivisions); and (3) how much forage the pasture has available – based on pasture height and density:
Once you find the appropriate numbers for your situation, input them into the calculations below. Remember, when you enter percentages into a calculator, that they often need inputted as decimals – for example, 3% as 0.03. You will probably only need to use one of the calculations at a time because you will often only be changing one variable at a time: the number of animals on a pasture/paddock, the number of days your animals remain on a pasture/paddock, or the size of a pasture/paddock.
Our example calculations will assume the following scenario: five retired horses averaging 1,100 pounds graze a pasture of mixed cool-season forages; these horses are expected to meet their dry-matter needs on pasture alone (without supplemental feed) and are moved to a new paddock once a week.
If you would like assistance in improving your pasture management, please contact your local USDA Service Center.
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