CRYOPRESERVATION OF PIG EMBRYOS

The changing global needs for food and animal products require the dev elopment of breeding strategies for maximizing genetic improvement whi le maintaining genetic diversity. Genetic diversity can be conserved b y using separate breeding herds; however, they may be expensive to mai ntain and inbreeding becomes a major concern. Alternative methods are needed to preserve valuable genetic resources in a reasonable and econ omic manner. Embryo cryopreservation allows indefinite storage in vitr o at subambient temperatures where metabolism and other cellular funct ions are greatly reduced or cease, and upon recovery from storage, nor mal developmental competence can be resumed. Storage and transportatio n require little maintenance and there is no expense in animal care an d little concern about disease transmission. Although there are method s for routine cryopreservation of germplasm and embryos of most livest ock species, development of this technology in the pig industry is far behind and has abated improvements in genetic potential. Pig embryos are very sensitive to hypothermic conditions, and this limits their ab ility to withstand many conventional methods of preservation. Much res earch has focused on the high lipid content of pig embryos, and its ro le in hypothermic sensitivity and cryosurvival. Many studies have repo rted the conventional freezing of pig embryos, and vitrification has s hown promise of eluding the difficulties associated with cooling sensi tivity and ice crystallization. Recent research suggests that the embr yonic cytoskeleton is susceptible to damage during cryopreservation, a nd this cellular disruption may be averted by using cytoskeletal stabi lizers before preservation. Embryos cryopreserved by conventional free zing and vitrification under the influence of cytoskeletal stabilizati on have resulted in pregnancies or live offspring from recipient femal es after surgical transfer. Although cryopreservation technology is le ss advanced in pigs than in other livestock species, promising researc h shows evidence that researchers are close to achieving a methodology for preserving pig embryos.