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Use Stocking Rate Calculations to Aid Grassland Management

09:21AM May 19, 2014

Stocker Cattle Spring Grazing( Wyatt Bechtel )

How do you determine a stocking rate?
By: Walt Fick, Range Management Specialist, K-State Research and Extension

What is meant by stocking rate? A stocking rate refers to the number of animals per unit area for a given period of time. For example, a typical stocking rate in the Kansas Flint Hills might be 7.5 to 8.0 acres per cow-calf pair for 6 months. In the High Plains of western Kansas, a stocking rate for a normal year might be 7 acres per 600 lb stocker for 5 months. Size, type, and class of animal impacts what a proper stocking rate should be. The other critical factor in determining a stocking rate is the amount of forage available.

How do you determine a stocking rate? The most accurate way to determine a proper stocking rate is to put a certain number of head on a given area for a specific period of time and see what happens. How do the animals perform? What happens to the plant community? Is the soil still protected from erosion? This approach takes time and adjustment to determine the appropriate long-term stocking rate that is sustainable and doesn’t deteriorate our natural resources. Another approach is to ask your neighbor or visit with a rangeland management specialist with NRCS or extension. Stocking rates used in a region may be based on longterm stocking rate studies done at experiment stations.

Formulas shown in Table 1 can be used for stocking rate calculations. Let’s assume available forage production for the season is 2500 lbs/acre, grazing efficiency is 25 percent for season-long grazing, and that a cow-calf pair will average 1500 lbs and consume 2.6 percent of their body weight. As the calculations show in Table 1, stocking rate 28 to 29 pairs.

Another question you might have is how many days of grazing do I have? Let’s assume you have 2000 lbs/acre, grazing efficiency is 25 percent for season-long grazing, and that 700 lb steers will consume 3 percent of their body weight. Number of grazing days calculates to be 152 days as shown in calculations in Table 1.

A couple of variables in these formulas are grazing efficiency and the percent of body weight consumed by the grazing animal. The 25% grazing efficiency is based on the animal consuming 25% of the dry matter, leaving 50% of the total production, with the other 25% disappearing because of trampling, plant senescence, etc. On native range the grazing efficiency number could be as high as 40% with a management intensive system with > 24 paddocks. The percent of body weight consumed by a grazing animal varies in the 2-5% range. A lactating cow will consume more than a dry cow. Stockers will consume 2-4% of their body weight depending on size and growth potential. A good average number to use would be 3%.
Stocking Rates
Another unknown may be the amount of forage available. Forage production varies with precipitation and ecological site. Average forage production on a loamy upland site in western Kansas may vary from 1,000 to 2,000 pounds/acre. A loamy upland site in the Flint Hills typically varies from 3,500 to 5,000 pounds per acre. Ecological sites in the same precipitation zone will also vary. Average production values are available from NRCS. Another way to determine forage production is to set up an exclosure, clip the forage at the end of the season, dry and weigh. A cattle panel can be bent into a circle and staked to the ground for the exclosure. Clip the forage at the end of the growing season from a 2 ft x 2 ft square plot placed inside the exclosure. Let the clipped material air dry for about 4 days. Weigh the dried forage in grams and multiply by 24 to obtain pounds/acre.

A number of factors influence grazing management including the kind of animal, season of use, and distribution of grazing. However, stocking rate is by far the most important factor. Knowing how to calculate a stocking rate and make adjustments is an important factor in managing our grasslands.