Optimization of Germplasm Cryopreservation Techniques

Sustaining healthy captive populations requires genetically balanced reproduction that equalizes founder contribution and provides for reinfusion of genes into future generations. Judicious utilization of preserved sperm and oocytes to create genetically valuable offspring is dependent on optimized cryopreservation protocols.

Capturing extant diversity in the form of sperm, ova, and embryos provides the potential to sustain or reanimate valuable genetic lines. Sperm and ova are extracted postmortem for evaluation, and sperm are collected opportunistically when animals are immobilized for medical procedures. Sperm viability is then assessed by motility, swimming speed, and force analysis, as well as staining for acrosomal and plasma membrane integrity.

The work of the Reproductive Physiology Division at CRES includes:

1. development of species-specific staining protocols and rapid, simplified staining techniques for field application and validation by laboratory and electron microscopic analysis
2. derivation of cryoprotectant formulation, concentration, equilibration, and removal techniques
3. assessment of the effects of cooling, freezing, and thawing rates
4. evaluation of sperm cryosurvival by in vitro or in vivo fertilization studies
5. determination of oocyte and embryo cryosurvival by in vitro embryo development and the establishment of pregnancies following embryo transfer.