Create Your Own Herd

Create Your Own Herd

Target Grade Level / Age Range:

6-8 th grades

Time:

90 minutes

Purpose:

Students will be able to understand how heredity affects agricultural decisions regarding wanted traits in animals, and will understand that DNA contains genes which carry traits from generation to generation.

Materials:

  • Create Your Own Herd Worksheets.docx
  • Skype, Google Hangouts, etc. (for FarmChat program)
  • Poster paper
  • Coloring utensils (crayons, markers, colored pencils, etc.)

Suggested Companion Resources (books and websites)

Vocabulary (with definitions)

  • Allele: One of two or more alternative forms of a gene that arise by mutation and are found at the same place (locus) on a chromosome
  • Locus: A specific place on a chromosome. Plural: loci
  • Heredity: The passing on of a physical or mental characteristic from one generation to another through DNA
  • Genotype: The genetic constitution of an individual organism
  • Phenotype: The set of observable characteristics of an individual resulting from the interaction of its genotype and the environment. (Example: A person’s skin tone is genetic, but by sitting in the sun during the summer, it can be altered.)
  • Dominant allele: An allele that is expressed fully if there is at least one copy at a given locus
  • Recessive allele: An allele that requires two copies at a given locus to be expressed phenotypically
  • Homozygous: Two copies of the same allele at a given locus. (Example: YY or yy)
  • Heterozygous: Two different alleles at a given locus. (Example: Yy)
  • Sire: Male parent
  • Dam: Female parent
  • Polled: Naturally hornless
  • Stocking legs: Color pattern on legs that gives the appearance of socks, or stockings
  • Rib Eye Area (REA): Measurement taken on meat animal carcasses of the loin, or muscle area on either side of the spine
  • Docile: Tame, gentle, generally not dangerous
  • Bovine: Term for cattle species
  • Bull: Fully intact male bovine
  • Steer: Castrated male bovine
  • Heifer: Young female bovine, has not yet had a calf
  • Cow: Mature female bovine, has had a calf

Background – Agricultural Connections (what would a teacher need to know to be able to teach this content)

  • This lesson will help students understand basic genetic concepts and the idea of artificial selection through the lens of animal agriculture.
  • Though it’s not required, it might be beneficial to cover mitosis and meiosis before this lesson, to give students the background to understand how DNA is passed on.
  • Activity 1: FarmChat®
    • This lesson includes a FarmChat (or video call session) with a beef producer, preferably someone who works with artificial selection or artificial insemination in some way. Depending on your classroom and what works with timing, this session could be either before or after the activity portion.
      • To find a producer near you, you can work with a local Agriculture in the Classroom representative, Extension, or the Iowa Agriculture Literacy Foundation. They may also be willing to assist you in planning & leading the FarmChat® program.
      • This session’s purpose is to help students understand the practical application of genetics and the technology currently being used in agriculture that utilizes it. It should help students also understand what role humans play in modifying characteristics in livestock herds.
    • Artificial insemination is a process by which sperm is harvested from a donor sire, packaged in “straws,” is frozen, and sold for use in recipient heifers or cows. These straws are then used to inseminate the female animal and hopefully will result in a pregnancy.
      • There are many ways to market or purchase straws of semen. One common way is through sire catalogs. Essentially, they are catalogs of various bulls (and occasionally some females) that show photos and list EPDs, or expected progeny differences. These EPDs give numerical values to each trait. Generally, traits like birthweight (BW), weaning weight (WW), calving ease maternal (CEM), calving ease direct (CED), and feed cost ($EN) will be monitored. However, those are just a small number of EPDs available. Each breed will have an average for each trait, and the difference from that breed average is displayed with the animal’s EPD.
      • Example of how to read EPDs: If bull 1 has a BW EPD of -5, and Bull 2 has a BW EPD of -8, you would say Bull 2’s offspring will weigh three pounds less than Bull 1’s offspring on average.
        • That can be a little confusing, but just remember that it’s a safer bet to compare the EPDs of two different animals than to say for sure what the progeny of one will be based on their EPD alone.
      • Also note that because EPDs are measured on breed averages, each breed will be different.
      • Information on Angus EPDs: https://extension.tennessee.edu/Greene/Documents/What%20Do%20The%20Angus%20EPDs%20Really%20Mean.pdf
      • Information on Hereford EPDs: http://www.hereford.org/content/epd-basics
        • Some cattle producers also use estrous synchronization tools to help ensure that they can breed all of their animals at the correct time and that all of their calves will be born near the same date.
          • Calving season can be a stressful time for cattle producers, as cows may calve in the middle of the night, may need assistance, or calves may be born with issues (born backwards, too large, trouble eating, born in rain or snow, etc.). Because of these long and stressful hours, producers try to keep calving season short. This also helps keep the animals at a similar size and development, which will help in marketing them later.
          • In dairy operations, producers will not synch the herd to cycle at the same time, because they need milk year-round to be profitable. Therefore, calving season is year-round for dairy producers.
            • Dairy producers will also purchase “sexed semen,” which means they will purchase a straw of semen only containing sperm that would produce either a male or female calf. This is more common in the dairy industry, as heifer calves are more profitable than bull calves.
  • Activity 2: Create Your Own Heard
    • This activity is organized such that students can learn about heredity, the randomization of traits, and more of the agricultural applications of genetics.
    • Included in the activity are 10 traits. They are:
      • Polled vs. horned: Polled means naturally hornless and is the dominant trait. This is generally seen as a positive trait because if animals are not polled, they are likely to be de-horned. De-horning is not a glamorous process but is seen as necessary because of safety issues to producers and the other animals.
      • Black vs. red hide: In areas with high heat, producers may want non-black hided animals so they can withstand higher heat.
      • Solid vs. spotted coat: How the spots are arranged may depend on the composition of breeds in the animal.
      • White face vs. colored face: This trait is gaining more attention, as there has been a correlation of animals with pinkeye and animals with white faces. Some producers are breeding for animals with a ring of color around their eyes, dark faces, or even for the way their eyelashes turn out. Pinkeye costs money to treat and takes time for the antibiotics to leave the animal’s system before it can be taken to market. Therefore, it is much more profitable to breed for animals that don’t get pinkeye.
        • Animals with white faces are often referred to as “baldies.”
      • Solid legs vs. stocking legs: This trait has little production value, but “stocking” legs will essentially look like socks.
      • Large REA vs. Small REA: Rib Eye Area is definitely a profitable category. Just like you would pay more money for a large loin eye steak, meatpackers will, too.
      • High birthweight vs. Low birthweight: This trait is deceptive, in that most producers look for low birthweights. Cattle are finicky in that they don’t always calve (or give birth) easily. One large factor in difficulty calving (also called dystocia) is birthweight. Depending on the breed, an average birthweight may be around 75-85 pounds. As a rule of thumb, any calf over 100 pounds is very large, and the mother will generally need assistance in calving. As you would expect, it's not fun to help pull a calf, so producers try to avoid this as much as possible by breeding for easy calving females and low birthweights. This helps all animals be born more safely and comfortably, and lets the farmer get more sleep!
      • Heat tolerant vs. heat susceptible: This trait isn’t critical in Iowa, but in areas like Arizona, New Mexico, and Texas, it’s very important. In these areas, they will even cross more heat resistant types of cattle (like the Brahman of India) to European breeds (like the Angus) to create a heat-resistant and hardy animal with better meat quality (like the Brangus – part Brahman, part Angus).
      • Docile vs. rowdy: As you might imagine, farmers don’t necessarily want to keep wild or dangerous animals around very long. Generally, they will only keep animals with calm demeanors for their breeding stock. The unpredictable ones will get sent to the sale barn.
      • Male vs. female: The dairy industry relies heavily on females, therefore this trait is very important to them. In the beef industry, there are uses for both males and females, so this is monitored less overall among beef producers.
        • Though the inheritance of gender is different than the others in the list, it is an important part of genetics.
        • Mothers can only give an X chromosome; therefore, fathers will always decide gender of offspring.
    • Punnett Squares work by aligning the sire and dam’s genotypes. One gene with two alleles will require a two-by-two box. The sire’s first allele will be assigned the left two boxes, and his second allele will be assigned the right two boxes. The dam’s first allele will be assigned the top two boxes, and her second allele will be assigned the bottom two boxes. When combined, you can visually see various genotype combinations and probability of passing on a certain genotype.
      • Genotype ratio: Ratio of all of the genotypes present. For example, in a monohybrid cross of two heterozygotes (Yy x Yy), they will yield one YY, two Yy, and one yy. Therefore, their genotypic ratio would be 1:2:1.
      • Phenotype ratio: Ratio of the phenotypes possible. In the same monohybrid cross, the phenotypic ratio would be 3:1, as homozygous dominant and heterozygous genotypes will be expressed the same way.
      • Probability: The probability of inheriting a specific genotype. In the same monohybrid cross, YY would have a probability of 25%, Yy would have a probability of 50%, and yy would have a probability of 25%. The space for this on the worksheet is limited, so if it would work best for your class to only write the probability for the most probable genotype, that would be acceptable.

Interest Approach or Motivator

Ask students if humans can choose what characteristics they want when breeding animals. Ask them what characteristics those might be and why. Lead the conversation into the upcoming FarmChat.

Procedures

Activity 1: FarmChat

  1. If possible, schedule a Skype, Google Hangout, FaceTime, or other video chat with someone who artificially inseminates cows. The goal is that students will learn how humans monitor and influence genetic traits within livestock.
    1. Any beef producer (regardless of if they AI) could be a good person to talk with, as they know which traits they look for in their herd, and could touch on some of the techniques farmers use.
    2. Attached is a sample outline for the FarmChat. Reorganize or tailor it to your classroom and current topics. Share the outline with the professional you plan to chat with.
    3. Before the FarmChat, prepare the students for what they should expect. Help them compile a list of things they would like to learn, along with some questions to ask.
  2. During the FarmChat, have students take notes.
  3. After the FarmChat, have students write a short paragraph summary, along with 3 facts they would like to remember.

Activity Two: Create Your Own Herd

  1. This activity will help students understand heredity, traits, and basic genetics.
  2. Before you hand out the attached worksheet (Create Your Own Herd Activity.docx), discuss some key topics from the FarmChat. Use this time to also explain any vernacular in the worksheet that the students might not be familiar with.
  3. Partner the students up (either by assignment, or allow them to choose a partner), and hand out the worksheet set. Each partner group will get only one worksheet set. Then hand out one piece of poster paper to each group. Have crayons, markers, etc., also available for students to use.
  4. Go through the worksheet quickly as a class to explain the process.
  5. They will be given 10 traits to monitor, they will flip a coin to find the genotypes of the parents, they will then complete Punnett Squares for each trait, complete ratios and probabilities of each, and use that information to create the most probable calf (F1 generation). Then, they will draw the parents and the offspring for the class to see.
  6. Give students the opportunity to ask questions about vocabulary, procedure, or other clarifying questions at this point.
  7. Allow the students to work on their activity. Walk around the room to make sure the students are understanding the activity. They will be completing the following steps:
    1. Traits of Interest: They will observe 10 traits, and learn which is dominant and recessive, including corresponding allele notation.
    2. Dam and Sire: Students will flip coins to determine the genotypic makeup of both parents. They will then analyze what phenotype will result because of the genotype.
    3. Draw the Parents: Students will draw the parents on the top portion of their poster. For non-visual traits, they can use labels. They are encouraged to do a good job with their illustrations, so they can be presented or displayed in the classroom.
    4. Punnett Squares: Students will use the genotypes from the parents to create Punnett Squares for each trait. Students will also find the genotypic and phenotypic ratio for each trait, as well as probability. If this has not yet been covered in class, working through a couple of scenarios on the board could be helpful.
    5. The Calf: Students will take the most probable genotype for each trait and apply it to the calf. They will also notate the phenotype for each.
    6. Draw the Baby: Students will use the traits found to draw a picture of their calf on the bottom half of the poster.
    7. Think it Through: Listed are some questions to help students think of some alternate scenarios. These can be used as class discussion questions, or a writing prompt, as well.
  8. If a particular section is proving difficult for the class, stop them and try to work through it as a class.
  9. At the end of class, have each group present their herd.
    1. If there is time, each group can stand up and show what they found, and describe why this could be beneficial or not.
    2. If there isn’t time, posters could be collected and taped up in the classroom for others to see later.
  10. Wrap up with some discussion about what students realized or learned in the activity.
    1. What did you expect? What didn’t you expect? Did things work out well, or not as well as you had hoped? If you had more options than those two parents, would you have picked them to become parents? If you were a farmer, what traits do you think you would want or not want?

Essential Files (maps, charts, pictures, or documents)

 Did You Know? (Ag facts)

  • Artificial insemination (AI) has been around since 1939.
  • Less than five percent of the nation's beef cows are bred by AI, but 66 percent of the nation’s dairy cattle are bred AI. This carries over the swine industry, where 70-75% of the nation’s swine are bred AI.

Extension Activities (how students can carry this beyond the classroom)

  • Students could write a 1-2-page summary explaining the traits of their calf and answering some of the questions at the end of the worksheet. If they do not know the answers, help them find ways to do simple research and cite their sources.
  • Another lesson could be made explaining EPDs (expected progeny differences). There are cattle magazines where bulls’ EPDs are listed, so producers can choose to only purchase semen from a bull with traits they want. An activity could be made where 2-4 bulls are chosen to be potential sires for one specific cow. Students could then weigh pros and cons of each bull and choose the one they think would be best. Students would need to back their choice with legitimate arguments.

Sources/Credits

Author(s) (your name)

  • James Sleep      
  • Chrissy Rhodes

Organization Affiliation (your organization)

Bedford Middle School
Iowa Agriculture Literacy Foundation

National Agriculture Literacy Outcomes

  • Science, Technology, Engineering & Mathematics:
    • T4.6-8.b: Describe how biological processes influence and are leveraged in agricultural production and processing (e.g., photosynthesis, fermentation, cell division, heredity/genetics, nitrogen fixation)
    • T4.6-8.g: Identify science careers related to both producers and consumers of agricultural products
    • T4.6-8.i: Provide examples of science and technology used in agricultural systems (e.g., GPS, artificial insemination, biotechnology, soil testing, ethanol production, etc.); explain

Iowa Core Standards

  • Science:
    • MS-LS1-2: Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to function.
    • MS-LS2-2: Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems.
    • MS-LS2-4: Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations.
    • MS-LS3-2: Develop and use a model to describe why asexual reproduction results in offspring with identical genetic information and sexual reproduction results in offspring with genetic variation.
    • MS-LS4-5. Gather and synthesize information about the technologies that have changed the way humans influence the inheritance of desired traits in organisms.
    • MS-LS4-6. Use mathematical representations to support explanations of how natural selection may lead to increases and decreases of specific traits in populations over time.

Creative Commons License


This work is licensed under a Creative Commons Attribution 4.0 International License.