Influence of Equilibration, Freezing Rate, Method of Dilution, and Diluent on the Survival of Deep-Frozen Bull Spermatozoa

Abstract

From the results of four factorial experiments on the deep-freezing of bull spermatozoa: (1) Revival rates of semen treated with lecithin followed by cooling to 5°C with dilution just before freezing did not differ significantly from samples diluted at 30°C soon after collection of the ejaculate. Aging the spermatozoa at 5°C for 6 hr before freezing was beneficial and a slow freezing rate of O· 5 to 1 degC fall per minute to -15°C followed by 3 degC fall below this temperature gave better results than faster rates. Time of storage at 5°C and freezing rate interacted, as fast freezing was much better tolerated by spermatozoa which had been aged at 5°C for 6 or 18 hr.