2 keys to calculating stocking rates

As the grazing season approaches, here are two variables that must be considered to properly estimate forage availability.

Amanda Radke

April 25, 2018

4 Min Read
2 keys to calculating stocking rates
Amanda Radke

Winter Storm Xanto has come and gone, and although we’re left with plenty of standing water and mud for calving out cows, it is such a blessing to see the grass starting to green up and grow as the grazing season approaches.

Knowing how truly fortunate we are, my heart is with the ranchers who are battling wild fires and whose pastures will be charred and bare this summer.

From flooding to drought, producers have to deal with all kinds of weather extremes, which often makes calculating stocking rates on available pastures and forages quite variable from year to year.

Determining the appropriate stocking rate does not have to be complicated, says Jace Stott, University of Nebraska-Lincoln (UNL) Extension educator. It simply comes down to two main elements — forage demand and forage availability.

READ: Good grazier? Most ranchers aren't there yet

1. Forage demand

In a recent UNL Beef Watch newsletter, Stott explains, “Calculating forage demand captures three important elements: animal size, length of time grazing and number of animals. Animal size is taken into account using an Animal Unit Equivalent (AUE). The AUE is an estimate of the amount of forage an average cow will eat.”

The baseline for the AUE system is a 1000-pound animal. In other words, a 1000 pound animal equals 1.0 AUE which will eat, on average, 680 pounds of forage (dry matter) or 780 pounds of forage (air dry). Each hundred pounds over or under the 1000 pound baseline is either an addition or subtraction of 0.1 (e.g. an 1100-pound cow equals 1.1 AUE).

READ: 11 grazing tips from top land managers

“To combine AUE with amount of time grazing and number of animals grazing, one simply needs to multiply. For example, if 30 cows weighing 1200 pounds were grazing for six months, the forage demand equation to calculate Animal Unit Months (AUM) demand would look as follows: 1.2 AUE x 30 head x 6 months = 216 AUM’s. This is our demand.”

READ: 13 things to consider to holistically manage your herd

2. Forage availability

Stott writes, “The productivity of a given piece of land is dependent on site characteristics which vary with location. To gain more accurate data for your property’s forage availability, there has to be some estimation of forage production as a starting point.

“If your pasture was previously hayed, use production records to calculate the average forage production (pounds per acre) of previous years. Clipping forage inside the dimensions of a small frame or hoop is the most common method for determining forage production if no previous production records exist. Try to clip at least 10 to 20 frames/hoops in areas that are typical of the pasture.

“After clipping, forage should be dried (for calculating on dry matter basis) and weighed in grams (remember to take into account weight of sample bags!), average your sample weights and use the conversion factor in the link below to calculate pounds per acre. Pounds per acre of forage is multiplied by 25%; this takes into account 50% utilization as a proper grazing practice to leave enough residual for plant vigor, and 25% of remaining forage which is not ingested due to trampling or insect damage (e.g. 100,000 pounds of forage will more realistically be 25,000 pounds of forage available for grazing due to this calculation (100,000 lb x 0.25 = 25,000 lb)).

“After available forage is determined, calculate how much a cow will eat per month to find the AUM’s for forage availability. A common standard is a 1000-pound animal will eat 780 pounds of air dry forage per month.

“With forage production and amount of forage consumed per month per head, we can now calculate the AUM’s for availability. Simply divide the available forage by the pounds of forage consumed by a single animal/month (e.g. 25,000 lb available forage/780 lb forage consumed by one animal in a month = 32.1 AUM’s). This is our availability.”

In the article, Stott provides links with videos that further explain how to calculate stocking rates, as well as a demonstration on how to use the hoop method to calculate pounds per acre. View the article and corresponding links here.

READ: How to get the most out of your limited hay supply

With the cold spring we’ve had in my neck of the woods, combined with some overgrazing due to drought last summer, we are anticipating that our grazing season will start much later than normal this year. In the meantime, we are utilizing stockpiled hay until we are ready for turn out.

According to North Dakota State University (NDSU) Extenion Service, we aren't alone in this struggle. In a recent article, John Dhuyvetter, NDSU Extension livestock systems specialist said, "At times like this, it may be necessary for producers to think outside of their traditional feeding strategy. Utilizing alternative feeds such as distillers grains, wheat midds or corn are cost-effective methods of stretching hay supplies."

How is the grazing season shaping up in your neck of the woods? How are you sitting for moisture? Share with us in the comments section below.

The opinions of Amanda Radke are not necessarily those of beefmagazine.com or Farm Progress.

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