Optimization of a Protocol for the Cryopreservation of Sperm in Pellets for the Common Pheasant (Phasianus colchicus mongolicus)

SIMPLE SUMMARY: The cryopreservation of avian semen is currently used to preserve species, breeds, and breeding lines. Bird sperm have unique characteristics, and each species responds differently to the freezing–thawing process; in this context, little information about the cryopreservation of the semen of the common pheasant is available. In this study, we tested different parameters at each step of the process of freezing into pellets and thawing with the aim of detecting the least deleterious parameter settings. The pheasant sperm exhibited a high susceptibility to the damage caused by the process of freezing into pellets; however, the survival rate of the sperm was 29%, and the greatest recovered mobility was 22%. The mobility of the sperm was affected by the dilution and the concentration of the dimethylacetamide cryoprotectant; the viability of the sperm was affected by both the equilibration at 5 °C and the dimethylacetamide equilibration. The protocols that caused the least damage to the pheasant sperm were found to be those with higher dilution rates, 10 min of equilibration at 5 °C and equilibration of 6% dimethylacetamide for 1 or 5 min. In the present study, we individualise some applicable parameters for certain critical steps of the freezing–thawing process; however, further investigations are needed in order to improve upon and complete a suitable protocol for the cryopreservation and thawing of pheasant sperm. ABSTRACT: The sperm of each avian species and breed have unique characteristics that render them more or less susceptible to the freezing–thawing process; therefore, a suitable cryopreservation protocol that is specific for the sperm of each type of bird is needed. In this context, little information about the common pheasant’s sperm is available. Therefore, the aim of this study was to test different parameters at each step of the process of freezing into pellets and thawing to detect the least deleterious parameter settings. Sixteen different protocols were tested by studying two levels in each of the four steps (dilution, equilibration at 5 °C, final dimethylacetamide concentration, and dimethylacetamide equilibration time) comprising the freezing process. The pheasant sperm exhibited a high susceptibility to the damage caused by freezing into pellets; however, the survival of the sperm reached 29%, and the greatest recovered mobility was 22%. The mobility of the sperm was affected by the dilution and the dimethylacetamide concentration, and the viability of the sperm was affected by the equilibration at 5 °C and the dimethylacetamide equilibration. The protocols that caused the least damage to the pheasant sperm were found to be those with higher dilution rates, 10 min of equilibration at 5 °C, and 6% dimethylacetamide equilibrated for 1 or 5 min. In the present study, we individualise some applicable parameters for certain critical steps of the freezing–thawing process; however, further investigations are needed in order to improve upon and complete a suitable protocol for the cryopreservation and thawing of pheasant sperm.