ABSTRACT
Optimizing the efficiency of animal production has never been more impor tant, as concern grows over diminishing natural resources and the increased output of waste products into the environment. It has been recognized for a number of years that the efficiency of nitrogen (N) utilization in ruminants can vary mark edly, and the use of synthetic steroid growth promotants has illustrated the vast potential for improvements in this area. The aim of this chapter is to examine technologies that may be used in the future to reduce N excretion in ruminants. The first section will describe a range of synthetic drugs and hormones, including (5-agonists and somatotropin (ST), which could become available for commercial use in the next few years. Next, a number of different vaccine technologies will be described that are aimed to enhance N utilization through immunological means. Finally, a brief review of transgenic technologies will be presented. Because of the number and diversity of approaches currently being explored, together with the fact that each of the methods described has its own advantages and disadvantages, the future of these technologies is difficult to predict and will be left to the reader. Instead, this chapter seeks only to describe the powerful effects of these technologies on N metabolism and to discuss the factors that affect their efficacy, practical constraints to their use, and their potential adverse effects on animal health and meat quality.
