Recent advances in the technology and techniques of genetic manipulation have caused an unprecedented expansion of possibilities for improvement in the breeding and development of livestock. This volume provides an up-to-date summary of work being done in this field, indicating how new discoveries can be integrated with established methods of breeding to create commercially competitive lines. It also considers future possibilities in research and development, and encourages researchers and graduate students in animal breeding, livestock improvement, molecular genetics, and reproductive physiology to consider new research methods.