DAFOSYM: A Model of the Dairy Forage System

A tool is needed for evaluating the biological and economic consequences of alternative technologies and management strategies on the dairy farm. This report views the development of a dairy forage system model (DAFOSYM) and demonstrates the use of this tool by examining alternatives in alfalfa hay production. DAFOSYM was produced by integrating models of crop growth, harvest, storage, and feed use. Growth models for corn (CERES‐Maize) and alfalfa (ALSIM1) simulate crop production over historical daily weather for given soils. Alfalfa harvest includes mowing, field drying, and baling where losses and quality changes are functions of the mechanical treatment, field curing time, and daily weather. Storage losses and quality changes are influenced by the type of storage and the crop moisture content. Stored feeds are supplemented with soybean meal and purchased feeds to provide a balanced diet for a given herd. Quality parameters carried through the system to balance rations are crude protein (CP) and neutral detergent fiber (NDF). Costs of crop production, machinery, storage facilities, and purchased feeds are compared to income from the sale of milk and excess feeds to determine net return. A multiple year simulation evaluates the long‐term benefit and risk of a new technology or strategy on a representative dairy farm. For example, simulation of a 5‐d delay in alfalfa harvest beyond optimum maturity reduced net return by $37/acre of alfalfa while use of the new harvesting technique of chemical conditioning increased return by $13/acre. DAFOSYM may be used in extension and classroom teaching to evaluate and compare alternatives for the dairy farm and by researchers to prioritize research activities.