Ruminate on Ruminant Digestion

In this activity, kids will experiment with different mixtures to replicate how ruminant digestion works.

About the Activity

The digestive tract of ruminant animals, such as cows, sheep, and goats, differs from that of other animals because instead of the single-chamber stomach that humans have, it has four. These chambers help to ferment and break down food, and eventually absorb nutrients. Pop rocks and soda aren’t the healthiest of snacks, but in this activity you are going to use them to replicate the digestive system of a cow.

Grades: 3-8
Topic: Animal Science, STEM
Estimated Time: 30-45 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.

Multiple cows eating grass


These simple supplies are all you’ll need for this activity. You may have most of them in your house, but you may need to drop by a convenience store for others.

  • 3 large, mixing bowls
  • Angel hair pasta (a dime- to nickel-sized stack of dry pasta)
  • ½ cup of water
  • 1 large funnel
  • 1 pack of pop rocks
  • 1 potato masher
  • A single, 12 oz-can of lemon-lime soda
  • 1 sponge
  • A 10-inch piece of rubber tubing ( 1 to 1.5 inches inches in diameter)
  • 2 paper towels
  • A gallon-sized sealable plastic bag
  • Masking tape
  • Permanent marker
  • Stapler
  • Scissors
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Activity Steps

The purpose of this activity is to review parts of ruminant digestion and the function. Participants will create a representation of the ruminant digestive system. Before we start, you should know that a cow’s stomach has four separate compartments to aid in digestion, each with their own unique function:

  • Rumen: The first and largest compartment holds large amounts of forage and water, and is where the fermentation and breakdown of feed occurs with the help of rumen microbes. Rumen contractions help mix the feed/forage and water.
  • Reticulum: This is the second compartment, which catches heavy items and aids in regurgitation for “chewing cud.”
  • Omasum: The omasum filters particles based on size into the fourth compartment.
  • Abomasum: This is the “true stomach” of ruminant animals, and contains stomach acid.
A cow eating grass

Now, let’s get started:
Step 1: Cook and drain the pasta
You don’t need to cook the entire package. To measure out your pasta, make a circle (or the “OK sign”) with your first finger and thumb, and tighten it up until the opening is the size of a dime or nickel. Fill the opening with dry pasta. Next, cook the pasta to the box's specifications. Most noodles cook in about 8-12 minutes in boiling water. Drain the water once the pasta has cooked.
Step 2: Label your mixing bowls
Put a piece of masking tape on each mixing bowl. Using your marker, label your mixing bowls as “Container 1,” “Container 2,” and “Container 3”
Step 3: Create your tube
You will use your plastic bag, stapler, and scissors to create the rubber tube (see pictures below).

  • Lay the bag flat on the table.
  • Roll the zippered-edge down until there is about 1 to 1.5 inches of space left at the bottom.
  • Staple down the rolled section along the edge.
  • Using your scissors, trim the short sides of the bag open to form the tube.

Step 4: Add ingredients to your mixing bowls

  • Add ½ cup of water and the cooked pasta into Container 1, and mix slightly. This is the “ingesta.”
  • Add the pop rocks to Container 2.
  • Add the lemon -lime soda to Container 3.Did you know? Even though your noodles may be cooling off, if they were to be digested by a real cow, they may go through another warming up period. The rumen environment has a pH range of 5.5 to 7.0 and the temperature range of 98 to 104 degrees Fahrenheit.

Step 5: Move your “feed” from the rumen to the omasum
Using the funnel, pour your ingesta from Container 1 through your tubing. You may need to use your hands to squeeze the ingesta through the tubing and into Container 2. Swirl the ingesta around Container 2 so that the pop rocks are mixed into it.Did you know? The inside of the rumen is covered with small, finger-like projections called papillae (pa-pil-la), which increase the surface area to aid in absorption of nutrients.

Step 6: Create your cud
This may get a bit messy!

  • Using the funnel, pour the mixture from Container 2 back into the tubing.
  • Use your hands to squeeze the mixture through the tubing and back into Container 1.
  • Crush the pasta into tiny pieces with your potato masher to officially make your cud.Did you know? A cow will chew its cud for up to eight hours per day.

Step 7: Move the cud into the stomach
Now your cud is going to go through a major part of digestion:

  • Using the funnel, pour the cud (mixture in Container 1) through the tubing. Again, you may need to use your hand to squeeze “cud” back through tubing into container 2, which is the omasum.
  • Pour the cud, which is now in the omasum in Container 2, through the strainer into Container 3, which has the lemon-lime soda.Did you know? The breakdown of feed by rumen microbes is a relatively slow process. Fiber particles remain in the rumen for 20 to 48 hours as they are broken down by bacteria.

Step 8: Move your cud through the intestines
After the feed is digested in the abomasum, it moves through the small and large intestines where nutrients and water are absorbed. Any undigested material in a ruminant animal will become excreta or manure. To see how this works, slowly pour the remaining cud (mixture from Container 3) onto your sponge and let the liquid absorb. Allow approximately 1 minute to absorb.
Step 9: Rid the digestive tract of waste
Collect solid pieces off the sponge and place the sponge on the paper towel to absorb water.

Reflection Questions
Bonus questions to inspire wonder.

  1. What are the four compartments of the ruminant stomach?
  2. What is the function of the microbes in the rumen?
  3. Why did you move content from Container 2 into Container 1 and then back into Container 2?
  4. Why is a healthy and functioning digestive system important for your beef cattle herd?
  5. Have you ever had a toy break from not playing with it the right way? If so, what happened to your toy at that time? What do you think happens if part of a beef cattle’s digestive system stops working? What process would you follow to correct the problem?
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Investigate and Explore
Take what you've learned to the next level to learn more and explore the possibilities.

Think about the last time you had a stomach ache. What happened? How did it make you feel? How long did it take for you to feel better? Now think about what might happen to a cow if it’s digestive tract was not working properly? What might happen if the feed was not broken down enough?

Let’s revisit our activity, and try it again, but this time, try skipping a step in the “digestion” process after you have set up your ingredients. What happened?

Four cattle standing on a grassy hill

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