Technical and economic models to support heifer management decisions: basic concepts.

To maximize herd profits, dairy farmers are faced with the complex dilemma of minimizing costs that are associated with rearing heifers while ensuring or enhancing lifetime economic productivity. Decisions about heifer management interact with underlying biological aspects of growth, thereby influencing future profitability. A thorough understanding of these biological interactions is lacking. Studies based on models could be useful in the evaluation of various rearing strategies. Currently available models for dairy cattle primarily focus on the dairy cow. In a dairy farm production system, management decisions concerning the rearing of livestock and the replacement of dairy cows strongly influence each other. In a model that describes the dairy herd as a multiple-component system, opportunity is greater to coordinate rearing and replacement policies. Expected benefits of such a model are discussed.