|Buckmaster, D - PENN STATE UNIVERSITY|
|Allen, M - MICHIGAN STATE UNIVERSITY|
|Harrison, J - WASHINGTON STATE UNIV.|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 2, 1999
Publication Date: N/A
Interpretive Summary: The dairy industry faces two major challenges as it adapts to current social and economic changes. The first is to remain profitable in a world market where milk prices are declining. The second is to reduce potential negative influences on the environment. Solutions to these challenges can only be obtained by developing more efficient production systems. Dairy farms are very complex, consisting of many physical and biological components. These components interact with one another and their environment, so the impact of changes implemented on the farm are often not easily predicted. Simulation models, which integrate the many components, provide excellent tools for exploring, evaluating, and optimizing alternatives in dairy farming. An important component of the farm is the herd of animals. A model of the herd provides a method for predicting feed consumption, milk production, and manure nutrient excretion as a function of animal management. When integrated with models of other farm components, a tool is obtained for evaluating the long-term profitability and sustainability of alternative technologies and management strategies for dairy production. Such a tool is useful to researchers, farm consultants, and producers in planning tomorrow's dairy farms. More efficient, profitable, and sustainable dairy farms will help provide a more secure food supply while maintaining or improving our environment.
Technical Abstract: A dairy herd model was created for integration with other farm component models to form DAFOSYM, a dairy farm simulation model. The herd model determines the best mix of available feeds to meet the nutrient requirements for each of six animal groups. The groups are early, mid, and late lactation cows, dry cows, heifers over one year old, and younger heifers. Feed intake, milk production, and manure dry matter and nutrient excretions are functions of the nutrient content of the animal diets. Required feed characteristics include crude protein, protein degradability, acid detergent insoluble protein, net energy of lactation, neutral detergent fiber, total digestible nutrients, phosphorus, and potassium contents. Feed intake is predicted using fill and roughage units. These units are functions of feed neutral detergent fiber weighted by particle size and the estimated ruminal digestibility of the particle size pools. The model was verified to predict feed intakes, nutrient requirements, diets, and manure excretions similar to those recommended or expected for dairy animals. When integrated with other farm components in DAFOSYM, the model provides a useful tool for evaluating the long-term performance and economics of alternative dairy farm systems.