Emerging strategies for enhancing growth: is there a biotechnology better than somatotropin?

During the past 20 years, there have been many impressive advances in a number of scientific disciplines that have led to the discovery and development of exciting new biotechnologies that offer the potential to improve productive efficiency of animal agriculture. Some technologies have been developed from advances made in our understanding of how the endocrine system regulates growth and lactation. This information then has been used to devise viable strategies that alter circulating hormone concentration(s) to enhance animal production and productive efficiency. The most notable success to date using this approach has been bovine somatotropin, which has been adopted for use in the dairy industry in certain countries. Advances in transgenic biology, gene therapy, "knock-out" gene technologies, and cloning may lead to other novel products/strategies that enhance productive efficiency. The purpose of this paper is to discuss what future strategies might emerge that will increase meat and milk production and the efficiency of these processes.