As the grazing season approaches, here are two variables that must be considered to properly estimate forage availability.
April 25, 2018
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.
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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).
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“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.”
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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.