RECENT ADVANCES IN SEX PRESELECTION OF CATTLE - FLOW CYTOMETRIC SORTING OF X-CHROMOSOME-AND Y-CHROMOSOME BEARING SPERM BASED ON DNA TO PRODUCE PROGENY

Recent progress, briefly reviewed here has led to the availability of a method of gender preselection in farm animals that can be used for producing progeny in cattle, sheep, and swine under semi-practical conditions. Sperm are separated based on the inherent difference in DNA content in the X-and Y-chromosome bearing sperm using flow cytometry/cell sorting technology. Sperm are stained with Hoechst 33342 which binds to the DNA helix in an amount proportional to the amount of DNA thus forming the basis for the method. Calves of predicted sex have been born using sorted sperm in conjunction with IVF resulting in embryos for transfer. Swine, rabbits and sheep have been produced using surgical insemination with smaller numbers of sperm than are required for artificial insemination. The inability to accrue large numbers of sperm in a short period of time precludes standard insemination techniques with sorted sperm. All offspring that have been born using this technology have been morphologically normal, and swine and rabbit offspring have shown normal reproductive function through two generations. Research to streamline hardware and improve staining technology is ongoing, while at the same time the method is being developed for the commercial embryo market.