Function and application of sex-sorted sperm

The development and application of flow cytometric sperm sorting for the pre-selection of sex has progressed at an increasing rate since the first report of live pre-sexed offspring of rabbits (Johnson et al, 1989). The technique has been extended to production of pre-sexed offspring of numerous domestic and wildlife species, and sorted bull semen is now widely available commercially around the world. Due to the stresses involved in the sex-sorting process, sex-sorted sperm may be functionally compromised in terms of reduced motility and viability, and their fertilising lifespan within the female reproductive tract may be reduced. Further, the time-consuming procedures involved in sperm sorting result in reduced numbers available for insemination. Consequently, fertility in vivo may be compromised. However, improvements to the technology and greater understanding of its biological impact on the sperm have facilitated recent developments in sheep, and we have demonstrated that sex-sorting is capable of selecting functionally superior ram sperm population in terms of both in vitro and in vivo function. This has resulted in high fertility after intrauterine insemination of frozen and thawed sex-sorted ram sperm (de Graaf et al, 2007). Unfortunately, to date, these results have not been matched in other species, though various techniques have been used to increase efficiency of use of sorted sperm. These include deep uterine insemination and in vitro fertilisation techniques.