Systems in Focus: Agriculture Model

This model could be used as the basis for methane production control, trade agreements about milk and how that impacts herd size, increasing production with demand, etc. In some of these scenarios, you would need to also look at feed, which is not included in this simple model.

There is a seasonality to this system, represented by the graphical function fraction impregnated. This adds a level of detail and discreteness that is normally not found in continuous System Dynamics models. For some applications, this level of detail may not be needed and yearly averages could be used. However, if you need to know when calves are available for sale or how much feed you need and when, this detail is needed.

Note the long delay from recognizing the need for an additional milking cow and the time for that cow to be born and grow to maturity. There is fairly sophisticated planning logic to keep the size of the herd relatively constant despite aging out one quarter of the milking herd each year.

The parameters in this model are a fair representation of the situation in the United States.