So you’ve been reading our blog posts and want to implement a higher density grazing system. Most people who want to integrate pasture rotation into their grazing system struggle with determining the size of paddock to make and how many animals can fit in there. Oregon Pasture Network has created a simple tool to help you figure that out.
There are a few pieces of information you will need, like how many animals you have and their average weight, and you will need some basic observations of your pasture. Since you most likely do not have a livestock scale, you may have to do some research on your specific breed of cattle to determine an average weight. But for a typical breed like an angus, you could figure about 500 pounds for a weaned calf, 1,200 pounds for a mature cow, and 1,000-1,200 pounds for a full size steer. Or, if your animals will let you take some measurements, there are some simple formulas that will help you get a rough idea of how much they weigh.
Here is a guide for calculating the weight of a sheep and here is one for cattle
When you take a walk in your field, you just need to determine an average forage height and the density of forage cover. The density is determined by the amount of bare soil, or conversely, the amount of soil that is covered by growing forage. Greater than 95% is considered excellent, 90-95% is good, and 85-90% is fair.
With those few pieces of information you can go to the calculator, plug those in, and it will tell you what size paddock those animals will need for one day. You will be entering your information into the green cells, and the orange cells will calculate automatically.
Start by entering your grass height and percentage cover, 3 for excellent, 2 for good, and 1 for fair. In this example, we have an average forage height of 10 inches and good (90-95%) soil coverage. There is a calculated total yield of 2,000 pounds of dry matter per acre.
Next, you will enter the number and size of your animals. Here, we have 12 steers that average 800 pounds each. We look at the chart to the right to determine the percentage dry matter needs for that class of animal, and for stocker cattle it is 2.5%, so we will enter the number in the right column, 0.025 into the green cell in row 14.
Row 17 calculates the dry matter needed in pounds for the entire herd for one day, and in row 18 you can adjust how much of your paddock you want them to eat. Unless you have specific goals in mind, it is suggested that you leave this at 50%, meaning they will eat half of the forage and trample/defecate/urinate on the other half.
Row 19 is the big number, and that is the size of paddock your animals will need for one day, and row 20 converts that to square feet. To make visualizing that a little easier, you can enter the dimension of one side of your paddock in the green cell in row 21 and it will tell you how long that paddock should be. Here, this rancher’s paddocks are about 40 feet wide, meaning to create a paddock that is 0.24 acres, the length would need to be 261 feet.
Below that is a calculator of your stock density per acre, so here we have the equivalent of 40,000 pounds of animal per acre.
Finally, if you want an even higher density – say, you want to trample out some undesirable plants – you can calculate how many moves per day can help you achieve that.
Using these same animals in an ultra-high density system would require 4 moves per day with a paddock of only .06 acres, or you could look at it as that .06 acres could hold that herd for ¼ of a day, or six hours.
If you have multiple classes of animals in the same pasture, use the mixed classes tab at the bottom of the page and enter the numbers and weights for each type of animal you have and it will aggregate all of them and perform the same calculations.
It is important to note that the paddock size calculated is just a starting point, there may be times you want a much higher impact to trample down some undesirable weeds or use dense hoof action to push freshly broadcast seeds into the ground and you may increase stock density by ten times or more. If you do this, though, make sure to proportionally decrease the amount of time the herd spends in the paddock. Or, you may be entering an extended period of dry weather and you know that regrowth is going to come at a slower rate. In order to leave more residue, you might change the desired amount of dry matter consumed to something like 30%, which would result in a decrease in density and a larger paddock. The key is to monitor your grazing and manage for what you want to see in your pastures.
To use the calculator, you will need to make a copy of it, as the version linked on this page can be viewed only. Go to the file menu, then click make a copy; a new version will open, which you can rename and bookmark or store in your Google Drive for easy access.