**Part 4**

**Farm / Pet / Laboratory Animal ART** 

228 Current Frontiers in Cryobiology

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**9** 

*Sweden* 

**Cryopreservation of Porcine Gametes,** 

Heriberto Rodriguez-Martinez

*Linköping University, Linköping* 

**Embryos and Genital Tissues: State of the Art** 

Preservation of germplasm (e.g. a term hereby applied to collectively gather spermatozoa, oocytes or early embryos whose use would –eventually- lead to offspring) for research, repository building and propagation of genetic material using Assisted Reproductive Techniques (ART) has been a long lasting priority (Mazur et al 2008). The first approaches, besides those historically anecdotic (see Flowers 1999) were directed to the application of artificial insemination (AI) of domestic species (Foote 1999) pertaining dissemination of genetics to a general population of, particularly, production animals. Positive effects for simple cryo-protectant agents (CPA) such as glycerol on animal sperm cryoprotection were demonstrated already by the end of the 1930`s (Bernschtein & Petropavloski 1937) and a decade later it became apparent that spermatozoa could be cooled, frozen and thawed in solutions containing egg yolk and glycerol (Polge et al 1949). For some species, such as bovine, the fact that bull semen could be easily frozen with an acceptable sperm survival post-thaw and accompanied by acceptable fertility after intra-uterine AI led to the rapid development of such primary reproductive biotechnology (Rodriguez-Martinez & Barth 2007). Attempts in other species of domesticated animals followed, and it was soon realised that the success seen with bovine could not be reached, primarily due to low sperm survival, difficulties in attaining an optimal deposition or proper timing towards spontaneous ovulation. Differences in survival and fertility varied not only among species but also between individuals of a given species or even ejaculates within sires (Holt 2000). Porcine male germplasm freezing started already by the 1950´s (Polge 1956) but their postthaw fertility was not reassured using cervical AI until a decade later (Crabo and Einarsson 1971, Graham et al 1971, Pursel & Johnson 1971), which revealed major constrains when applying cryopreservation on boar spermatozoa. Today, despite documented efforts to reach acceptable fertility and prolificacy after AI (Eriksson et al 2002, Roca et al 2011), the cryosurvival of boar spermatozoa is still consistently low in comparison to other species, owing to damage during a processing that is time-consuming, costly and yields few doses per ejaculate (see Rath et al 2009, Rodriguez-Martinez & Wallgren 2011). Number of piglets born is lower than for cooled or neat semen implying that sperm lifespan, deposition site and closeness to ovulation are yet significant hurdles to be overcome (Roca et al 2006b, Wongtawan et al 2006). Preservation of male genetics can also be performed by freezing of

**1. Introduction** 

*Department of Clinical and Experimental Medicine, Faculty of Health Sciences,* 
