How to Calculate Stocking Rates for Your Pastures
Determine forage yield or quantity in your pastures., Estimate the utilization rate for your pasture., Understand the amount of dry-matter forage one animal unit consumes per month., Perform the calculations to get local stocking rate., Understand...
Step-by-Step Guide
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Step 1: Determine forage yield or quantity in your pastures.
Even though it's much easier if you obtain such information from a local county extension office, it's even more precise to develop the values yourself.
Doing so takes time, diligence, a grazing stick, and a cheap microwave for the barn.
In order to get forage yield of your pastures you may need to do a bit of clipping in different sites around the pasture.
Take a 1 ft x 1 ft quadrat and anywhere the quadrat is put down, clip the forage inside that square and put it in a brown paper bag.
Label the bag to know which pasture it came from.
Ideally, you should take about 10 or more of such clippings in the same pasture to get an albeit small representative sample size.
Take those forage samples, weigh the container you are going to put them in (should be in pounds to make things simple), then weigh the samples plus the container.
Simply subtract the weight of the container to get the weight of the sample if your weigh scale does not have a "tare" function on it (most scales should).
If your scale can be tarred, then set the container on it, tare it to zero, and put the sample on.
Dry the sample in a microwave oven, each session
1.5 to 2 minutes long, and keep a cup of water with the sample in the microwave to prevent it from burning.
Weigh the sample after each session, and keep weighing until the weight of the sample is no longer decreasing.
Record the weight as a dry weight, and continue with the other samples collected.
Once you have dried and weighed all the samples, take an average of all the final dry weights.
To get forage yield in terms of pounds per acre, simply multiply the average result by 43,560 square feet per acre to convert pounds per square foot to pounds per acre.
Another method, which is much less time-consuming and tedious, but takes much more practice and head-arithmetic, is using a grazing stick.
A grazing stick is basically just a yard stick with formulas on the side to calculate the amount of forage is in your pasture.
Put the end of the stick down to the ground, and measure the height of the sward 15 to 20 times (never stretching the leaves of the plants) to get an average forage height in inches.
Next, estimate forage density based on plant cover.
Density is based on a percent basis, ranging from less than 75% to 90% cover (density is never, ever 100%).
Then, based on forage type and density estimate, multiply average plant height by the dry matter yield of the forage type.
This will give you an estimate of the amount of forage you have available per acre.
For example, with multiple measurements you came up with 10 inches of forage height.
Looking at the density, you estimate that there is around 80% plant density.
This is an orchard grass stand, so let's say the conversion factor is 160 lb per acre-inch (see Using a Grazing Stick for Pasture Management for the table used).
Thus 10 x 160 = 1600 lb/acre. -
Step 2: Estimate the utilization rate for your pasture.
The rule of thumb for utilization rate, which is basically how much forage is going to be consumed versus left behind on a percent basis, is the longer a herd stays on the pasture, the lower the utilization rate.
Also, the poorer the pasture, the lower the utilization rate.
For most pastures, most stocking rates are based on a 50-percent utilization rate.
However, if the pasture density is lower than 75 percent and height less than 6 to 8 inches, utilization rate should be closer to 25 or 30 percent.
For this instance, let's assume that this pasture is going to see a 50% utilization rate., One animal unit is equal to one 1000 lb cow or cow-calf pair consuming
2.5 percent of her body weight in dry matter forages per day.
On average, that cow or cow-calf pair is expected to consume around 800 lb of forage per month.
This is is a fixed variable that does not change when performing stocking rate calculations, especially on continuous-grazed tame or extensively grazed native grassland areas., The formula for stocking rate is forage quantity (lb/acre) x (% utilization rate/100) / AUM in terms of forage consumption.
Via the examples created in this article, the stocking rate example is (1600 lb/acre x
0.5) / 800 lb =
1.0 AUM/acre., Forage quantity and utilization rates are the two major variables that are prone to change.
This is why you must measure the amount of forage available in your pasture and do the calculations so that you have an accurate measurement of what's available in your area.
Grazing sticks can be purchased at a local county extension office or applied research organizations.
It's highly recommended every person who manages and grazes cattle have one every time they go out to check the pasture. -
Step 3: Understand the amount of dry-matter forage one animal unit consumes per month.
-
Step 4: Perform the calculations to get local stocking rate.
-
Step 5: Understand which variables are fixed and which are not.
Detailed Guide
Even though it's much easier if you obtain such information from a local county extension office, it's even more precise to develop the values yourself.
Doing so takes time, diligence, a grazing stick, and a cheap microwave for the barn.
In order to get forage yield of your pastures you may need to do a bit of clipping in different sites around the pasture.
Take a 1 ft x 1 ft quadrat and anywhere the quadrat is put down, clip the forage inside that square and put it in a brown paper bag.
Label the bag to know which pasture it came from.
Ideally, you should take about 10 or more of such clippings in the same pasture to get an albeit small representative sample size.
Take those forage samples, weigh the container you are going to put them in (should be in pounds to make things simple), then weigh the samples plus the container.
Simply subtract the weight of the container to get the weight of the sample if your weigh scale does not have a "tare" function on it (most scales should).
If your scale can be tarred, then set the container on it, tare it to zero, and put the sample on.
Dry the sample in a microwave oven, each session
1.5 to 2 minutes long, and keep a cup of water with the sample in the microwave to prevent it from burning.
Weigh the sample after each session, and keep weighing until the weight of the sample is no longer decreasing.
Record the weight as a dry weight, and continue with the other samples collected.
Once you have dried and weighed all the samples, take an average of all the final dry weights.
To get forage yield in terms of pounds per acre, simply multiply the average result by 43,560 square feet per acre to convert pounds per square foot to pounds per acre.
Another method, which is much less time-consuming and tedious, but takes much more practice and head-arithmetic, is using a grazing stick.
A grazing stick is basically just a yard stick with formulas on the side to calculate the amount of forage is in your pasture.
Put the end of the stick down to the ground, and measure the height of the sward 15 to 20 times (never stretching the leaves of the plants) to get an average forage height in inches.
Next, estimate forage density based on plant cover.
Density is based on a percent basis, ranging from less than 75% to 90% cover (density is never, ever 100%).
Then, based on forage type and density estimate, multiply average plant height by the dry matter yield of the forage type.
This will give you an estimate of the amount of forage you have available per acre.
For example, with multiple measurements you came up with 10 inches of forage height.
Looking at the density, you estimate that there is around 80% plant density.
This is an orchard grass stand, so let's say the conversion factor is 160 lb per acre-inch (see Using a Grazing Stick for Pasture Management for the table used).
Thus 10 x 160 = 1600 lb/acre.
The rule of thumb for utilization rate, which is basically how much forage is going to be consumed versus left behind on a percent basis, is the longer a herd stays on the pasture, the lower the utilization rate.
Also, the poorer the pasture, the lower the utilization rate.
For most pastures, most stocking rates are based on a 50-percent utilization rate.
However, if the pasture density is lower than 75 percent and height less than 6 to 8 inches, utilization rate should be closer to 25 or 30 percent.
For this instance, let's assume that this pasture is going to see a 50% utilization rate., One animal unit is equal to one 1000 lb cow or cow-calf pair consuming
2.5 percent of her body weight in dry matter forages per day.
On average, that cow or cow-calf pair is expected to consume around 800 lb of forage per month.
This is is a fixed variable that does not change when performing stocking rate calculations, especially on continuous-grazed tame or extensively grazed native grassland areas., The formula for stocking rate is forage quantity (lb/acre) x (% utilization rate/100) / AUM in terms of forage consumption.
Via the examples created in this article, the stocking rate example is (1600 lb/acre x
0.5) / 800 lb =
1.0 AUM/acre., Forage quantity and utilization rates are the two major variables that are prone to change.
This is why you must measure the amount of forage available in your pasture and do the calculations so that you have an accurate measurement of what's available in your area.
Grazing sticks can be purchased at a local county extension office or applied research organizations.
It's highly recommended every person who manages and grazes cattle have one every time they go out to check the pasture.
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Lori Garcia
Brings years of experience writing about crafts and related subjects.
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