EFFECT OF POST-THAW WARMING ON VIABILITY OF BOVINE SPERMATOZOA THAWED AT DIFFERENT RATES IN FRENCH STRAWS

One study was to determine if sperm are damaged by post-thaw warming, if rate of thawing influences the susceptibility of sperm to post-thaw warming, and if sperm are damaged by a delay in warming at about 5 C. Straws were submersed in water at 35, 55, 75, or 95 C to achieve temperatures of 5 or 35 C. Additional semen thawed to 5 C was held in air for 30 s and then warmed to 35 C in the same bath used for thawing (delayed warming). Fewer sperm retained intact acrosomes after warming to 35 rather than 5 C regardless of thawing rate. However, a delay in warming, per se, was not detrimental. Thus, post-thaw warming was damaging whether it was immediate or delayed, and damage was independent of rate of thawing. A second study was to establish the influence of rates of thawing and post-thaw warming on spermatozoal motility and acrosomal integrity. Straws were submersed in water at 5, 35, or 75 C to achieve thawing to 5 C and immediately placed in air at 35 C or water at 35, 55, 75, or 95 C for post-thaw warming to 35 C. Although motility and acrosomal integrity differed with thawing rate, differences due to post-thaw warming rate were small and inconsistent. Thawing in warm water should be timed to prevent seminal temperature from rising above 5 C, and thawed semen should be used immediately. © 1979, American Dairy Science Association. All rights reserved.