Freezing Bovine Semen. IV. Effect of Freezing on the Metabolic Activity of Bovine Spermatozoa during and after Storage at −79° C ,

Abstract

Summary No evidence of respiratory activity by bull spermatozoa diluted in skimmilk-glycerol during storage for 6 mo. at −79° C. could be demonstrated as measured by production of C 14 O 2 from radioactive substrates present in the frozen medium. However, freezing resulted in harmful effects on post-thawing metabolism of spermatozoa. After 6 mo. at −79° C., twice-washed spermatozoa showed 34% less C 14 O 2 production from glucose-U-C 14 during post-thawing incubation for 6 hr. at 5° C. than during a similar prefreezing incubation period. Unwashed sperm, frozen and stored for 1 hr., produced 61% less lactic acid during post-thawing incubation for 3 hr. at 37° C. than sperm from the same semen samples which were not frozen. The 36% loss of motile sperm due to freezing was not sufficient to explain the greatly reduced lactic acid production. Sperm stored frozen for 1 hr. in skimmilk-glycerol showed significantly greater post-thawing lactic acid production during incubation under air than those frozen in 1:4 egg yolk-citrate-glycerol, even though fewer sperm survived freezing in skimmilk. Adding 1.25% fructose to skimmilk-glycerol and egg yolk-citrate-glycerol diluents resulted in greater lactic acid production by both frozen, thawed and unfrozen spermatozoa. However, frozen samples still showed greatly depressed metabolic activity as compared to unfrozen samples.