Introduction to Sperm Sexing

Sperm sexing is an assisted reproductive technology that involves the sorting “X” and “Y” chromosome-bearing live sperm cells of semen samples. Insemination of sexed semen would help to produce animals of predetermined sex, and the use of sexed semen is an essential solution for the animals with sex-linked diseases. Animals of the desired sex are of great interest for animal farmers to increase the economic benefits. Furthermore, production of genetically superior quality animals could be possible by the use of sexed semen. Use of sexed semen is a feasible solution to maintain the optimum sex ratio of the animals. Potential differences of “X” and “Y” chromosome-bearing sperm cells form the basis for sperm sexing. It is evident from previous reports that Y chromosome-bearing sperm cell contains relatively less DNA, and it is smaller in size and swims faster than X chromosome-bearing sperm cell. Based on the surface charge, Y chromosome-bearing sperm moves slower than “X” chromosome-bearing sperm cells toward the cathode. Absence of HY antigen on the surface of X chromosome-bearing sperm cells also forms the basis for immunological sexing. So far, Flow cytometric sorting of semen is proven to be successful in sperm sexing on a commercial scale. This technology is based on the staining of the sperm cells with a fluorescent dye and sorting according to the DNA content. Real-time polymerase chain reaction (PCR), fluorescence in situ hybridization (FISH), and Raman microspectroscopy are being developed to validate sperm sexing. Sexed semen is in high demand for the breeding of production animals like cattle, sheep, and pigs. Applications of sexed semen may expand to sports and companion animals like horses, dogs, and cats. Nanoparticle-based sperm sexing, genome editing, and microfluidics are some of the emerging new strategies being developed for safe and efficient sperm sexing. Even though the animal welfare societies raised some ethical issues, sexed semen can be used with ethical policies laid down by recognized national and international animal welfare agencies.