APPLIED DYNAMICS OF DAIRY REPLACEMENT GROWTH AND MANAGEMENT

The applied objective of rearing dairy replacement heifers is to minimize investment inputs while maximizing profitable outputs. To reduce inputs one fundamental methodology is to reduce rearing time. Research efforts to reduce the age at first calving below 22 to 24 mo have generally resulted in reduced milk yield. Research suggests that reductions in milk yield may be the result of high energy planes of nutrition, employed to reduce calving age, on mammary parenchyma tissue development. This research is vital to an understanding of the effects of growth and development on the output potential of the replacement heifer, but it is not the only consideration in applied management. Other management factors, such as feed efficiency, dystocia, calving weight, and economics, also have a large influence on the decision-making process in management schemes for replacement heifers. When management schemes are developed, all of these factors must be taken into account, but at present, the interrelationships of management factors are poorly understood. As a consequence, only modest progress has been made in dairy replacement heifer management programs over the last three decades. Making positive changes for the future requires creative thought, investigations of new concepts, and application of those concepts by innovative producers in a management program that results in acceptable performance and profitability.