Average Daily Gain

Average Daily Gain

Target Grade Level / Age Range:

9-12 th Grades


55 minutes

Virtual Learning:

Use this document to convert the lesson into a virtual learning module for your students. Use the steps outlined to create the different elements of a Google Classroom or other online learning platform. You can also send the steps directly to students in a PDF, present them in a virtual meeting, or plug them into any other virtual learning module system. 


Students will use livestock weight gain data to construct and interpret line graphs.


  • 10 toy beef animals or beef cattle pictures, numbered 1-10
  • 10 toy pigs or pig pictures, numbered 1-10
  • 10 toy chickens or chicken pictures, numbered 1-10
  • Sheets of graph paper with ¼ “squares.
  • Rulers

Vocabulary (with definitions)

  • Average Daily Gain – the weight of an animal divided by the number of days on feed to represent the weight in pounds gained by that animal each day
  • Slope/intercept form - the equation of a straight line in the form y = mx + b where m is the slope of the line and b is its y-intercept. 
  • Line of best fit – a straight line that best represents the data on a scatter plot.  This line may pass through some of the points, none of the points, or all of the points.

Interest Approach or Motivator:

  1. Before students arrive, copy data for each animal from the Feed Data Excel Sheet onto individual pieces of paper. Number the chicken, pig and beef steer figures so that each animal has its own set of data.
  2. Students will enter the classroom and chose from either a chicken, a pig or a beef steer figure. They will then collect the slip of paper with their animal’s data on it.

Background – Agricultural Connections:

The efficiency of meat animals can be computed several ways. One of those is with average daily gain (ADG), which is simply days on feed/change in weight. For farmers, ADG shows how quickly an animal is gaining weight. The faster an animal gains, the quicker it is ready for market, which can decrease input costs.

The ADG of beef cattle, swine and chickens has improved greatly over the last 50 years. In 1950, ADG for chickens was .044 and in 2014 it was .129. These increases indicate an improvement in livestock genetics and nutrition. ADG can be impacted by animal health, animal nutrition, feed rations, animal environment, and other outside factors, as well as the genetics of the animal.

The ability of animals to gain weight quickly key to producing enough protein to feed a growing middle class. As animals become more efficient, the supply of meat increases and therefore, the overall price decreases. The agriculture industry must work to provide nutritious food for upwards of 9 billion people by the year 2050, so increasing animal efficiency is very important.

The efficiency of beef cattle can be improved by using synthetic hormone implants. These implants are small, injected into the ear, and dissolve after releasing all of the hormone. The hormone implants replace some of the hormone production lost after castration without aggressiveness or poor quality meat characteristics. Implanted beef has a very small amount of additional estrogen and progesterone present in the meat.

Procedures (main points, step by step activities, and the full content to be presented to students)

  1. Students will use the data on their slip of paper to construct a set of axes and plot the given 10 points. Days will be listed on the x-axis and weight will be plotted on the y-axis.
  2. Students will plot points on their graph.
  3. Students will then draw a line of best fit on the graph paper. Once this line is drawn, students should choose two points to write an equation of the best-fit line.
  4. Students will then predict the y-values of six points by choosing 3 x-values that are less than the maximum x-value and 3 x-values that are greater than the maximum x-value.
  5. Once each student has completed their individual graph, ask students to share their findings with the class. Record each student’s equation for line of best fit on the board. Ask students to use their data to calculate the average daily gain for each period (each data set) and the overall average daily gain over the animal’s life.
  6. Start a class discussion on the significance of the data. Ask students:
    1. What does this data represent?
      1. The weight in pounds an animal gains per day, or average daily gain (ADG)
    2. Why might ADG be important to farmers and consumers?
      1. Efficiency lowers price
      2. Efficiency promotes environmental sustainability
      3. ADG can indicate health problems in the herd (sick animals don’t eat/gain)
      4. ADG can indicate the effectiveness of a feed ration
    3. Would a higher ADG or lower AGDG be beneficial?
    4. How might the efficiency of meat animals impact world hunger and the ability to feed an increasing population?
    5. Which animal is most efficient? Least efficient? Why do you think that is?
    6. How can science and technology improve ADG?
      1. Hormonal implants (estrogen) that can improve animal’s feed intake and efficiency
      2. Feed rations balanced to maximize animal nutrition by meeting all animal health needs

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



Jim Walser – Ridge View High School

Kelsey Faivre - IALF

National Agriculture Literacy Outcomes

  •  Science, Technology, Engineering & Mathematics Outcomes:
    • Discuss population growth and the benefits and concerns related to science and technologies applied in agricultural systems
  • Culture, Society, Economy & Geography Outcomes
    • Discuss how agricultural practices have increased agricultural productivity and have impacted the development of the global economy, population, and sustainability

Iowa Core Standards

  • Math:
    • F-IF.B.4 For a function that models a relationship between two quantities, interpret key features of graphs and tables in terms of the quantities, and sketch graphs showing key features given a verbal description of the relationship.
    • F-IF.B.4For a function that models a relationship between two quantities, interpret key features of graphs and tables in terms of the quantities, and sketch graphs showing key features given a verbal description of the relationship. Key features include: intercepts; intervals where the function is increasing, decreasing, positive, or negative; relative maximums and minimums; symmetries; end behavior; and periodicity.
    • F-IF.B.5 Relate the domain of a function to its graph and, where applicable, to the quantitative relationship it describes. For example, if the function h(n) gives the number of person-hours it takes to assemble n engines in a factory, then the positive integers would be an appropriate domain for the function.
  • Science:
    • HS-ESS3-3: Create a computational model or simulation of a phenomenon, designed device, process, or system.
    • HS-ESS3-6: Use a computational representation of phenomena or design solutions to describe and/or support claims and/or explanations.

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