Abstract
A model is a tool used to study the dynamics of a system when investigations on the system itself are difficult because of scope, scale, sensitivity, or other complexities. Beef cattle production in the United States is at least a 2- to 4-phase process, consisting of economic, social, environmental, and biological relationships. As such, modeling is a logical strategy to handle many research questions focused on systems responses of beef cattle production systems. There are a number of modeling tools that can be used to research beef cattle production settings, including but not limited to: nutrient requirement models, pasture models, farm system models, and life cycle assessments. Life cycle assessments are the broadest category of models and typically fall under the umbrella of static, deterministic, empirical models that encompass the entirety of the beef production system from manufacture of the inputs through production of the outputs. There are a number of life cycle assessments of beef cattle production systems and comparison of the outcome of these models is a strategy to discern how changes in one aspect of the production system affect all downstream processes. Farm system models can assess an individual economic enterprise or an entirety of a beef production system and typically are dynamic, mechanistic models of the interactions between cattle and their external environments. Several researchers have also established deterministic, empirical farm system models, or hybrids of these two model types. Pasture models can be independent of or tightly linked with farm system models. Most pasture models are dynamic, mechanistic models; however, deterministic, empirical models also exist. Pasture models typically seek to model plant/soil/water interactions. Finally, animal response models and nutrient requirement models can be used to represent animal/feed/management interactions. These models can be dynamic or static, deterministic or mechanistic.