Make Your Best Cow Pasture

Is your “cow pasture” equipped to feed cattle? Let’s find out!

About the Activity

Did you know that grasses make up about 26% of the plant life on Earth? And since cows are grazers by nature, it’s not surprising that grasses contribute significantly to a cow’s diet, especially when they are out in the pasture. But exactly what they eat when they are foraging for themselves may not be as cut-and-dry as when the feed is premeasured.

In this activity, kids you’ll learn how to determine if a pasture is right for your cattle and how many it can support.

Grades: 3-8
Topic: Animal Science, Math
Estimated Time: 30 minutes

Brought to you by the University of Tennessee Extension 4-H Youth Development, the University of Tennessee Institute of Agriculture Department of Animal Science, and USDA's National Institute of Food and Agriculture.

A picture of grass

Supplies
These simple supplies are all you’ll need for this activity.

  • 6 plastic drinking straws (approximately 9 inches each)
  • Tape
  • Scissors
  • Ruler or yardstick
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Activity Steps

In this activity, we are going to calculate two things: species composition and forage yield. Species composition can be estimated through visual observation. Forage yield, or the total amount of forage available for grazing, can help make decisions about how many cattle a pasture can support.

There are various ways to determine forage mass, but using a grazing stick or pasture ruler is a simple method. Using a frame or quadrant can help with these observations because it breaks a large area into small, measurable pieces. Print out the worksheet, and let’s get started!

Three cows eating grass in a field

Create a frame with your straws

  1. Cut four of the drinking straws into 3-inch lengths.
  2. Tape one, 9-inch straw and one, 3-inch straw together to create a side that is 1-foot long.
  3. Repeat Step 2 three more times until you have four foot-long pieces.
  4. Tape the four pieces together to form a square. You now have your frame!

 
Tip: You can use the “bendy” part of the straw as the corner to connect it easier.
 
Place your frame
Place your frame in a random, grassy location. If you don’t have access to a pasture, a yard or a field will do just fine. Toss the frame a short distance in front of you to allow for random sampling.
 
Take stock of your sample
Observe your grass sample from above to determine the species composition.

  • Estimate the following items listed in the chart below to the nearest 5%. Record your observations in the appropriate place in the worksheet.
  • Measure the average height of the forage within the frame and record your observations in the appropriate spot in the worksheet.
  • Repeat this process three more times, until you have a total of four samples.

Example for measuring species composition: Figure 2 shows an illustration of a quadrant in a mixed pasture. The pointed plants represent desirable species and the rounded plants represent weeds. An estimation of species composition here would be 50% desirable species, 40% weeds, and 10% bare ground.
 
Tip: When measuring the forage for height, it helps to place your hand on top of the forage canopy to determine the height, making sure you are not measuring the tips of the longest pieces. The height should be a representative average of the plant height within the quadrant, which you can determine roughly by laying your hand flatly against the top of the grass.Did you know? Incorporating legumes like clover into pastures can improve forage quality and add nitrogen to the soil.
Did you know? In real situations, forage crops are categorized by three criteria:

  • Grass or legume
  • Annual or perennial
  • Warm-season or cool-season


Calculate forage mass
Use the information in the grass chart in the worksheet Figure 1 to calculate the forage mass in your plot of land. For illustration purposes, choose whichever species is most common in your pasture/yard.Did you know? As forage grows and becomes more mature, its yield increases but its quality decreases.

Reflection Questions
Bonus questions to inspire wonder.

  1. What does species composition tell you about the condition of your pasture?
  2. What does canopy height tell you about your pasture?
  3. Other than straws, what else could be used to create a frame for observing species composition?
  4. How can you use these measurements to determine the most appropriate number of animals for a pasture?
  5. What other information about the cattle or grazing system do you need to know to make grazing decisions?
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Investigate and Explore
Take what you've learned to the next level to learn more and explore the possibilities.

For this activity, you will need a camera (a camera on a mobile device will do just fine), an internet connection, note cards, and markers.

  • Take a photo of one of the weeds you found in the first activity. Research to identify the type.
  • Repeat this with other types of weeds, plants, or grasses that you observed.
  • Create a set of flashcards that includes five different grasses and five different weeds that are common where you live. To create each flashcard, put the mage on the front and name on the back.
  • If you didn’t find enough plants for your flashcard set, research additional grasses and weeds that are local to your area, and create flashcards for those.
Close-up of wheat

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No endorsement of these supporters' products or services is granted or implied by 4‑H. This work is supported by the USDA National Institute of Food and Agriculture, AFRI - Education and Workforce Development project 2021-67037-33376.9

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