Education Standards
Nutritional Value of Livestock Feeds
Overview
How does the nutrient content of cereal grains and their by-products change as they are processed? In this lesson, students will determine the presence of starch and protein in common feedstuffs used in the livestock agriculture industry.
Overview
Essential Question
What nutrients are present in common cereal grains and their by-products?
Learning Objectives
Identify feed products that contain carbohydrates and/or proteins.
Demonstrate the use of chemical tests to indicate the presence of nutrients.
Equipment and Materials
Equipment
- (5) Test Tubes
- (1) Test Tube Rack
- (1) Mortar and Pestle
- (5) Droppers
- (4) 50 mL Beaker
Materials
- Example Samples of Livestock Feed
- Whole Corn, Ground Corn, Steam-Flaked Corn
- Whole Soybeans, Soybean Meal, Soy Hulls
- Whole Oats, Wheat Bran, Wheat Straw
- Masking Tape
- Iodine Solution (with dropper)
- Biueret Solution (with dropper)
- Distilled Water
*Any material that might be used as feed for animals may be substituted.
Per Student
- Pen/Pencil
- Lab Notebook
- Safety Goggles
Lesson Plan
Background Information
Livestock must be fed a diet that provides them with enough energy to sustain all of their physical activities and bodily functions. One type of feed may supply several of the needed nutrients, but usually a certain feedstuff only contains a concentration of a particular nutrient. This is why feedstuffs are generally combined with other types of feeds to create a more complete diet for the animal.
Interest Approach
Facilitate a discussion with students about which of them raise livestock and what they raise them for. Transition into asking them about what they feed their livestock and why they choose to give them that specific feedstuff. Explain that feedstuffs usually contain a concentrated amount of a particular nutrient, and that the type of feed we need to provide to our livestock will change based on the nutritional needs of each specific animal.
Career Connections
- Feedlot Manager
- Nutrition Consultant
- Veterinarian
Experimental Procedure
Preparing the Nutrient Solutions
- Prepare the first nutrient solution by grinding one of the feed samples into smaller particles using a mortar and pestle.
- Once the sample is completely ground, add a small amount of distilled water to the sample to turn the mixture into a waterlike solution.
- Grind until the feed and water are thoroughly mixed and the solids are small enough to pass through a dropper.
- Pour the mixture into one of the 50 mL beakers. Use a piece of masking tape to label the beaker with the name of the feedstuff the solution contains.
- Wash the mortar and pestle and repeat Steps 1-4 to prepare each of the other desired feed materials. Label each beaker appropriately.
Part 1 - Test for Starch (Carbohydrates)
*Caution - Wash chemicals immediately from your skin if any is spilled!*
- Obtain the same number of test tubes as nutrient solutions you have prepared and use masking tape to label each with the name of the feedstuff it will contain.
- Using a clean dropper for each sample, place ten drops of each nutrient solution into the appropriately labeled test tube and put them in the test tube rack.
- Label an additional test tube as "water" and then put ten drops of distilled water into the test tube. This will serve as a control group during the experiment.
- Hypothesize which feeds contain each nutrient and record your answer in Table 1.1.
- Record the color of the solution in each test tube you have prepared in Table 1.2.
- Add three drops of iodine to each of the test tubes.
- Gently swirl each test tube to mix the contents. If the color changes to a deep blue or a blue-black, starch is present. Record the results for each sample in Table 1.2.
- Properly dispose of the nutrient solutions in the test tubes into a sanitary sink and wash the test tubes thoroughly.
Part 2 - Test for Protein
- Using the same quantity of test tubes as in Part 1, label each with the name of the feedstuff contained in each of the nutrient solutions prepared in the 50 mL beakers.
- Use a clean dropper to place ten drops of each nutrient solution in its corresponding test tube and place them in the test tube rack. Add ten drops of distilled water to the control test tube.
- Record the color of the solution in each test tube you have prepared in Table 1.3
- Add ten drops of Biuret Solution to each test tube and swirl gently to mix the contents.
- Record the color of each test tube in Table 1.3. The presence of protein is indicated by a shade of purple.
- Properly dispose of the nutrient solutions in the test tubes into a sanitary sink and wash the test tubes thoroughly.
Conclusion/Check for Understanding
After the conclusion of student data collection and cleaning up of materials, bring the class back together and have students discuss their results in small groups. Discussion should be focused on which feed samples contained each of the individual nutrient classes. Have students share their results with the whole class by having them group the feedstuffs used during the experiment into distinct categories.
- Which feed samples contained starch?
- Which feed samples contained protein?
- Did the results of any of the samples surprise you? Why?
- Do any of your families feed these feedstuffs to your livestock? Why?
Extension Activity
Based on the data collected in their experiment, students should research a specific livestock species and create a proposal for the types of feedstuffs that should be included in their ration.