Optimisation of freezing conditions for bovine spermatozoa

The use of a programmable forced vapour biological freezer to optimise freezing conditions for bovine semen is described. The results showed that for most bulls, optimisation is possible, including bulls whose semen shows poor survival with conventional freezing methods. The importance of inducing ice crystallisation before any significant degree of supercooling occurs is also demonstrated, as the majority of sperm are lost in this region of the freezing curve. Comparison with static vapour freezing shows enhanced post thaw sperm survival, particularly with bulls whose semen shows poor survival using conventional freezing methods.