Principles of Genetics and Breeding

9.1.7.1 Equilibration

• For effective protection during cooling sufficient time must be allowed to facilitate the penetration of cryoprotectants into cells.
• It is a time interval between mixing the milt in the diluent and putting the mixture into liquid nitrogen.
• Smaller molecules such as methanol will enter cells at a faster rate than larger compounds like glycerol.
• Calibrated duration of equilibration time helps for efficient function of the cryoprotective agents.
• The longer the equilibration time the lower the fertility as because the cryoprotectant might be becoming toxic to cells. For most circumstances it can be set at 15 to 30 min, but it can be varied depending on the type and concentration of cryoprotectant being used.
• If the concentration of cryoprotectant is toxic to the cells, the equilibration time of rapidly permeating cryoprotectants such as DMSO can be shortened to the minimum time required for filling of straws.