How to Estimate & Allocate Your Forage with a Grazing Stick
Estimating pasture forage yield and allocation can be challenging for beginner graziers. Luckily, tools like the grazing stick exist to assist producers in overcoming these first-timer difficulties and advancing their pasture management knowledge. Commonly given out at grazing workshops and pasture field days, grazing sticks are an educational and supportive tool useful for making immediate pasture management decisions.
While they appear to be just a simple measuring device at first, grazing sticks provide much more than just a ruler to measure forage heights. Grazing guidelines and conversion formulas are also displayed on the stick. Together, this combination of information gives pasture managers a simple way to measure pasture yield, determine how to allocate that pasture to livestock, and track changes in forage growth over time.
Grazing sticks vary somewhat across regions and states, however, the majority allow the following information to be obtained from a pasture:
- Forage height measurements
- When to start and/or stop grazing
- When livestock should be moved to a new pasture
- Average pasture growth rates
- Rotation and rest period lengths
- Estimates of amount of available dry matter
Using a Grazing Stick
STEP 1: The first step in using a grazing stick is estimating forage yield. It's good to note, that this estimate is only as good as the sample taken. For a uniform, fairly flat pasture, at least one sample per acre is suggested. More measurements will need to be collected in fields with varying soil types, topography, and forage species.
Use the ruler on the side of the grazing stick to measure forage height. Spread your hand and lower the grazing stick into the plant canopy. Height will be measured at the point where some resistance from the plant canopy is felt on your hand. Measurements should be taken in multiple places across the pasture, at least one sample per acre, recording measurements as you go. Then add up the measurements and divide by the total number of samples to obtain an average forage height for the entire pasture.
STEP 2: The next step is to determine stand density. This is the amount of ground surface covered with standing forage. Ideally, a pasture should fall in one of three density categories: less than 75%, 75-90%, or more than 90%.
This reading can be done visually, or by using the table with dots that appears on the side of most grazing sticks. To use the table, slide the stick sideways into standing forage that is approximately 5-8 inches tall. With the stick flat on the ground and the forage covering the stick, look straight down and count the number of dots you readily see. Record the density or number of dots seen for each location plant canopy height was measured, and then calculate the average to determine stand density for the pasture. Once this number has been obtained, the density yield table on the grazing stick can be used to estimate forage yield per acre (lb DM/acre-inch).
STEP 3: Now find the table on the stick which gives estimates for pounds of dry matter per acre-inch according to the average stand density or number of dots. Rotate the stick to find the best description of the forage present (e.g., Orchardgrass and clover, bluegrass mix, perennial ryegrass, tall fescue, etc.). It's important to note, these tables assume pastures have received some level of management (i.e. liming, nitrogen application).
Figure out the amount of forage available for grazing per acre by subtracting 3-4 inches for remaining leaf and stubble from the average height of the pasture. Then multiply this number by the estimated pounds of dry matter per acre inch value determined from the table.
Example: 5 inches x 150 lb/acre-inch = 750 lb DM/acre
Pasture Allocation Examples
After these steps and measurements have been completed, other estimates can be made with calculations by knowing the number, type, and size of animals to be grazed. Some rules of thumb for pasture intake as a percentage of body weight are as follows:
|Class/type of livestock||Intake as % of body weight|
|Dairy cow||2 to 4%|
|Sheep/lamb||3.5 to 4%|
Pasture Size Needed to Feed a Set Number of Animals
|Acres required =||(weight) x (intake in % of body weight) x (animal #) x (days/paddock)|
|paddock||(available DM/acre) x (% utilization)|
Example: 50 cow-calf pairs (2.5% intake of body weight), average weight 1200 lb. Animals are moved every 3-5 days. Pasture is an orchardgrass-clover mix estimated to have 750 lbs DM/acre and managed using intensive grazing methods for a utilization of 60%.
|1200 lb x 0.025/day x 50 pairs x 4 days =||28.5 acres required per paddock|
|750 lb DM/ acre x 0.60|
Number of Animals Needed to Utilize the Available Forage
|# of animals required to graze a pasture =||(DM/acre) x (acres) x (% utilization)|
|(animal weight) x (intake in % body weight) x (days)|
Example: A 20-acre paddock with a grazing period of 4 days. For simplicity, we'll use the same cattle and pasture numbers as the above example.
|750 lb DM/acre x 20 acres x 0.60 =||75 cow-calf pairs|
|1200 lb x 0.025/day x 4 days|
Number of Days a Pasture Will Last
|Days of grazing per pasture =||(DM/acre) x (acres) x (% utilization)|
|(animal weight) x (intake in % body weight) x (# animals)|
Example: A herd of 100 cow-calf pairs on a fast rotation. Paddock size is 20 acres and we will use the same cattle and pasture info again.
|750 lb DM/acre x 20 acres x 0.60 =||3 days|
|1200 lb x 0.025/day x 100 cows|
In time, new graziers will find the grazing stick to be a handy and useful tool. However, it's important to remember, this tool only provides an estimate of pasture yield. Its recommended producers still take steps to improve management by incorporating a grazing plan into their record keeping and farm practices. Combined with the grazing stick, graziers will be better able balance forage supply to their livestock's needs in the long term.
More info on the use of grazing sticks can be found here, as well as by contacting your local extension or National Resource Conservation Service office. Tables and calculations featured in this article were sourced from extension and resource materials provided by the University of Kentucky and USDA-NRCS.