Influence of glycerol concentration and freezing rate on post-thaw motility of bovine spermatozoa in Continental straws.

Semen from each of six bulls was used to study the effects of percent glycerol and rate of freezing on spermatozoa extended in egg yolk-sodium citrate extender and packaged in .25-ml Continental straws. Treatments were arranged factorially and included 5, 6, 7, 8, 9, 10, or 11% (volume/volume) glycerol; freezing rates (time from 5 to -130 C) of 1, 2, 3.5, 7, 12, or 20 min; and post-thaw incubation times of 0 and 2 h at 38 C. Post-thaw motility was similar for spermatozoa frozen in 2 to 20 min, and all means were greater than for spermatozoa frozen in 1 min. Post-thaw motility of spermatozoa frozen in 7% glycerol did not differ from that with 5 to 9% but was superior to that with 10 or 11% glycerol. Although glycerol and freezing rate interacted, 7% glycerol provided survival equal to or greater than that with the other percents of glycerol, regardless of freezing rate.