Improving Efficiency in Saugeye Production Using Cryopreserved Milt

Periodically, saugeye (Sander canadensis x S. vitreous) production goals have been compromised by weather-related alterations in broodstock collection seasons. Sperm cryopreservation can be used to store excess milt for long term use. Recently, hypertonic extenders have been shown to increase post-thaw motility, viability and fertility of ram (Ovis aires) sperm by reducing osmotic stress associated with cryoprotectant addition. The objective of this study was to assess the effect of three different extenders on cryopreserved sauger milt post-thaw motility and viability. Ejaculates from twenty males were divided into three aliquots and diluted in Rathbun (Moore 1987) extender at different osmolarities (350, 500, or 750 mosm/kg) to one billion sperm per milliliter.  Samples were then diluted 1:1 with 10% dimethyl sulfoxide, distributed into 0.25 ml straws and cooled in liquid nitrogen (LN2) vapor for ten minutes prior to submersion in LN2. After cryopreservation, straws were thawed in a 21°C water bath for 30 seconds and post-thaw motility and plasma membrane integrity were assessed. Post-thaw motility and viability were significantly different (p < 0.05) in samples cryopreserved at different osmolalities. These methods will be further developed for scaling of cryopreservation protocols to provide production security during unfavorable weather conditions.