Sex preselection in bovine by separation of X- and Y-chromosome bearing spermatozoa.

Flow cytometrically-sorted sperm has been involved in the production of sex preselected offspring. More than 30,000 bovine offspring have been produced using AI and other means using spermatozoa separated by flow cytometer. Flow cytometric sperm sorting based on differences in their DNA content is the best method for separation of X- and Y-chromosome bearing spermatozoa. At first, flow cytometers were modified for DNA confirmation and sorting of sperm with high resolution. The beveled insertion needle can regulate orientation of flat-shaped bull sperm heads. The forward fluorescence detector is essential for measuring the DNA content of sperm. Recently, high-speed sperm sorting with orienting nozzles has resulted in production of 90% pure X- and Y-sperm at rate of 15-20 million sperm per hour. Application of this new technique will enable conduct of more conventional technologies for both artificial insemination and cryopreservation in the bovine and in other farm animals using X- or Y-sperm.