Embryo Sexing: A Review of Current Techniques and Their Potential for Commercial Amdication in Livestock Production

The development of embryo transfer procedures has created the potential for embryo sexing as a method of controlling the sex of offspring. Five techniques have been developed for this purpose: cytogenetic analysis, assay of X-linked enzymes, analysis of differential development rates, detection of male-specific antigens, and the use of Y-specific DNA probes. These methods are reviewed and their potential for commercial application in domestic animal production is discussed. The use of Y-specific DNA probes, particularly those that employ DNA amplification techniques, has resulted in the greatest potential for commercial application. An assay based on a bovine Y-chromosome-specific DNA sequence is described. This assay has a determination rate greater than 90% with samples as small as two cells and accurately determines sex 94% of the time. For economic and technical reasons, embryo sexing has not been widely used in conventional embryo transfer, but these procedures, particularly Y-chromosome-specific DNA amplification techniques, are quite applicable to embryo cloning and will be vital when cloning becomes commercially viable.