Applications and interpretation of computer-assisted sperm analyses and sperm sorting methods in assisted breeding and comparative research

Abstract

Theoretical and practical knowledge of sperm function is an essential requirement in almost every aspect of modern reproductive technology, if the overarching objective is the eventual production of live offspring. Artificial insemination (AI) techniques depend on the availability of high quality semen, whether fresh, diluted and stored, or frozen. Assessing such semen for quality and the likelihood of fertility is therefore also important, as much time, resources and effort can easily be wasted by using poor samples. Some semen technologies are aimed not at quality assessment, but at attempting to skew the breeding outcomes. Sex preselection by separating the male- and female-bearing spermatozoa using flow cytometry is now practised routinely in the agricultural industry, but speculatively it may eventually be possible to use other genetic markers besides the sex chromosomes. A moment's reflection shows that although sex-biasing flow cytometry technology is well developed and generally fulfils its purpose if presorting of sperm quality is adequate, other technologies aimed specifically at semen assessment are also sophisticated but provide inadequate data that say little about fertility. This is especially true of instrumentation for objective sperm motility assessment. Here we aim to examine this technological paradox and suggest that although the sperm assessment equipment might be sophisticated, the shortcomings probably lie largely with inappropriate objectives and data interpretation. We also aim to review the potential value and use of sperm sexing technology for non-domestic species, arguing in this case that the limitations also lie less with the technology itself than with the applications envisaged. Finally, the potential application of a sorting method directed at motility rather than sperm DNA content is discussed.