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How to Calculate Stocking Rates for Your Pastures
Two Methods:
Stocking rates are largely dependent on the amount of forage an "animal unit" will consume, or utilize, for one month. The amount of forage is the largest variable that is prone to change based on annual precipitation for your area; forage production can change drastically within a growing year, thus it's important to know how to develop your own stocking rate numbers for your farm or ranch. This article will assist you with this, in addition to providing examples for different scenarios you may encounter, and where to take the stocking rate calculations from here. Two methods of calculating stocking rate is mentioned, using the standard AUM, and using actual animal weights of your stock.
Steps
Calculating Stocking Rate Using Standard Animal Unit Month

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 timeconsuming and tedious, but takes much more practice and headarithmetic, 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 acreinch (see for the table used). Thus 10 x 160 = 1600 lb/acre.
 Another method, which is much less timeconsuming and tedious, but takes much more practice and headarithmetic, 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.

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 50percent 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.

Understand the amount of drymatter forage one animal unit consumes per month.One animal unit is equal to one 1000 lb cow or cowcalf pair consuming 2.5 percent of her body weight in dry matter forages per day. On average, that cow or cowcalf pair is expected to consume around 800 lb of forage per month. This is a fixed variable that does not change when performing stocking rate calculations, especially on continuousgrazed tame or extensively grazed native grassland areas.

Perform the calculations to get local stocking rate.The formula for stocking rate isforage 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.

Understand which variables are fixed and which are not.Forage quantity and utilization rates are the two major variables that are prone to change. This is why youmustmeasure 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.
Calculating Stocking Rate Using Actual Animal Weights

Determine forage quantity or yield of your pastures.The methods already discussed above are exactly the same for this method. Assume that you came up with an estimated 1600 lb/acre of forage.

Determine the number of acres to graze.This is basically total amount of area to graze, or how many acres one set paddock is. Let's assume, for this example, that you are wanting to graze 20 acres.

Estimate the percent utilization desired.As already mentioned, the lower the forage quantity, the lower the utilization rate should be. For this example, let's stick with the 50% standard already mentioned.

Get the weights of your animals.At this time it's safe to remind you that this method of stocking rate calculation is not excluding other livestock species. You can use sheep, goats, horses, etc. to estimate stocking rate. Mind, though, the rate of intake as mentioned in the next step. To continue this example, let's assume you're wanting to graze 1250 lb lactating cowcalf pairs.

Estimate the rate of intake as percent of body weight per animal per day.Cattle are expected, on pasture, to have a rate of intake ranging from 2 to 3.5 percent dry matter intake of body weight per day; dairy cows especially are going to be closer to 2.5 to 3.5 percent of forage DM of body weight per day. Horses are going to be about the same, and sheep and goats (lactating) are expected to have a rate of intake of 3.5 to 4 percent of their body weight in DM forage per day. Let's assume you have these cows consuming 2.5 percent of their body weight in DM forage per day.

Calculate it all together.The stocking rate formula, for this method, isStocking Rate (animals/acre) = (Total DM lb of forage/acre x # of acres x (% Utilization rate/100)) / (Animal weight (lb) x (intake rate as % BW/animal/100)). Using the example created for this article, calculate stocking rate as follows: Stocking rate = (1600 lb/acre x 20 acres x 0.5) / (1250 x 0.025) = 512 animals/acre.
 Do note that this is on adailybasis. If you wanted to include the number of days animals are on pasture, then simply add a multiplication of number of days to the denominator (which is multiplying animal weight to rate of intake) to get the number of animals needed to that particular paddock for x number of days. If we were to add 2 days to the example above, then the number of animals per acre is 256 instead of 512.

Understand the variables prone to change.Unlike the first method above, all of the variables that are used in the formula in the previous step are prone to change. Everything from knowing the weight of your animals to knowing forage quantity is important to get an accurate estimate of stocking rateon a daily basisfor a particular paddock or pasture.
Community Q&A
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QuestionWhat time of year should I clip/measure the forage to determine density?Top AnswererLate spring to early summer is the best time, when all plants are up and, for most tame pastures (with a lot of tame forages), the best time to clip is when grasses are in their 3rd to 4th leaf stage, and not quite pushing up a seed head. For fun and for a neat comparison, you can also clip later in the year when plants have headed out and started flowering, just to see what kind of differences you get.Thanks!

QuestionHow do I calculate carrying capacity?Top AnswererCarrying capacity = AUM/acre, based on current forage yield in that area. It changes year to year, unlike stocking rate, which assumes forage yield does not change.Thanks!

QuestionWhat is the minimum stocking rate for 40 acres?Top AnswererIt really largely depends on your location and how much forage is available annually, determined by longterm carrying capacity values that typically are available from your local agricultural extension or county office. For areas with moderate to good moisture, the minimum stocking rate should be 1 to 2 AUM/acre; drier more arid areas is going to have a minimum of 0.5 to 0.25 AUM/acre or less.Thanks!
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 A grazing stick is a great, simple tool to use to measure forage quantity. If you can't get a grazing stick through a forage association or local county ag extension office, all you need is a metre or yard stick for the same purpose.
 Never use the microwave you use for food in the kitchen. Purchase a cheap one to use for feed analyses in the barn or shop, so that the smell from drying forage samples doesn't upset your spouse/partner, or makes your food taste or smell weird next time you use it for heating food or drinks.
 Forage density is never at 100 percent, and it's very rarely at 90%. You're always going to get some "bare ground" or litter exposed, and, because the forage density is based on leaf area, the amount of leaf area that all forage plants in that spot you are looking down on is going to be less than 90%.
 Animal Unit Months (AUM) is used on continuousgrazed and rangeland or extensive pastures, primarily, because of the premise that cattle are going to be grazed for a month or two, not moved around on a daily basis. The latter method is more ideal for rotational or managedintensive grazing systems, and highly recommended for that exact purpose.
Warnings
 Calculations are based predominantly as a guideline, not something set in stone. These calculations are going to change throughout a single growing season, so it's important to monitor pasture quality and forage quantity with every pasturecheck in that one season.
 In other words, never ever assume that a onetime measurement is going to stay at that one measurement all grazing season!
 Continuous grazing is not the best type of grazing management to choose because it leads to severe uneven pasture utilization. It has its advantage in some areas, like in certain native grasslands, but not in tame pastures where more even forage utilization is encouraged. Continuous grazing can also encourage growth of undesirable plant species that livestock are not willing to consume.
Video: Stocking Rate
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Date: 14.12.2018, 14:12 / Views: 75341