Fresh and frozen storage of salmonid spermatozoa

This study was carried out to evaluate techniques for fresh and frozen storage of salmonid spermatozoa and develop methods to assess sperm viability following storage. Three in vitro methods (motility, fluorometry, and enzyme leakage) were evaluated. Fluorometry and motility were simpler to perform than enzyme leakage and gave reliable results. Motility and fluorometry measurements indicated that semen stored above the oxygenated fluorocarbon layer exhibited significantly (p $<$ 0.05) longer duration of motility and significantly (p $<$ 0.05) lower proportions of dead spermatozoa after 37 days of storage. Measurement of lactate dehydrogenase leakage did not identify any one treatment as superior for semen storage and was difficult to perform. Fifteen diluents (five extenders x three levels of cryoprotectant) were evaluated to cryopreserve Atlantic salmon semen and two superior diluents as identified by fluorometry were used to cryopreserve spermatozoa from six individual fish at a freezing rate of $-$30$\sp\circ$C per minute to $-$196$\sp\circ$C. There was a significant difference (p $<$ 0.05) detected by fluorometry in the post-thaw viability of spermatozoa from the six fish. Motility and LDH leakage indicated non-significant relationships in the post-thaw viability of spermatozoa from the six fish. A new cryoprotectant, dimethyl acetamide (DMA) was evaluated as a cryoprotective agent for rainbow trout semen.

A combination of fluorometry and motility are recommended to assess the viability of stored spermatozoa of salmonids to predict fertility. (Abstract shortened by UMI.).