Key words: artifcial insemination, chromosomal sex-sorting, cryobiology Introduction Reproductive biotechnologies have been developed for routine, mi- crobiologically-safe propagation of genetic material among breeding populations. Moreover, they also shorten generation intervals and allow for selection of specifc traits in a given population. Semen still is the “cheapest” component of artifcial breeding. Therefore, AI is the most prevalent reproductive biotechnology used on a global scale and, depend- ing on the species, requires the preparation of liquid, chilled, or frozen- thawed insemination doses (Rodríguez-Martinez, 2012a). Consequently, research efforts still focus on improving the quality of sperm exposed to manipulations required during their preparation for AI, especially the ones associated with sperm cryobiology. Successful freezing of semen from of all livestock is a high priority due to its numerous advantages including biosecurity and disease monitoring, conservation of specifc genetics, and global commercialization of superior genotypes. Cryo- preservation success is linked not only to acceptable survival and lifes- pan post-thaw, but also to acceptable fertility after AI. If fertility levels with frozen semen are ever going to be similar to those with fresh semen, then a holistic approach for improving semen processing technologies must be used. This requires a critical assess- ment of semen and sperm function. Semen is heterogeneous popula- tion of sperm bathed in seminal plasma of heterogeneous composition (Rodríguez-Martinez et al., 2011). The spermatozoa in semen have the following unique characteristics that need to be considered during their manipulation: 1) their head contains substantially less free water than their neck and tail segments (Morris et al., 2012); 2) they use both an- aerobic glycolysis and aerobic respiration for energy production (Silva and Gadella, 2006); 3) their plasma membrane contains water channels including glycerol-transporting aquaglyceroporins (Ekwall, 2007); and Semen technologies in domestic animal species Heriberto Rodríguez-Martínez * and Fernando Peña Vega † * Department of Clinical and Experimental Medicine (IKE), Faculty of Health Sciences, Linköping University, SE-581 85 Linköping, Sweden † Laboratory of Equine Reproduction and Equine Spermatology, Veterinary Teaching Hospital, Faculty of Veterinary Medicine, University of Extremadura, Cáceres, Spain © Rodriquez-Martinez and Peña Vega doi:10.2527/af.2013-0030 Implications • Artifcial insemination (AI) has increased the dissemination of ge- netic material and enhanced the selection of best sires and dams. • Use of cooled liquid semen for AI still dominates in most species, while cryopreservation is the rule in dairy cattle. However, ad- vances in the development of new containers, freezing methods, and AI strategies are likely to increase the use of frozen semen in other species. • Gradient separation methods are renascent to harvest the most robust spermatozoa from semen from sires, even those with low sperm quality or when sperm with a specifc chromosomal sex are needed. • Sperm sexing is commercially available today in dairy cattle and, following application of novel fndings in sperm- and seminal plasma diagnostics, will likely lead to its commercialization in other species. • Current research in the epigenetic capabilities of sperm should lead to improved diagnostic tests for male fertility, which could lead to new procedures for producing transgenic animals via AI. 26 Animal Frontiers Wikipedia Downloaded from https://academic.oup.com/af/article/3/4/26/4638652 by guest on 25 June 2022