The Influence of Glycerol Level, Various Temperature Aspects and Certain other Factors on the Survival of Bull Spermatozoa at Sub-Zero Temperatures

Abstract

When added slowly to bull semen diluted with yolk citrate, glycerol (0-30%) had little effect on the percentage of motile sperm during storage at 5[degree] C. There was no significant difference in sperm survival after freezing with samples diluted to contain 10, 30, and 90 million sperm per ml. Approx. 7% glycerol resulted in opt. sperm survival after freezing and storing at -79[degree] C. Higher sperm survival rates were attained when samples were thawed in a water bath at 5[degree] C than at 38[degree] C. Adding glycerol to semen diluted with yolk citrate at 4.5[degree] C gave slightly better results than adding it at 10 or 15.5[degree] C. Adding the glycerol in 3 equal portions at 10-min. intervals resulted in slightly higher sperm survival after freezing than did a complete addition at one time. Equilibration for 6 hrs. with the glycerol was adequate for opt. survival of bull spermatozoa. Opt. results were obtained when the cooling rate from 5 to .20[degree] C was between 1 and 4[degree] C per min. Samples frozen and stored at various temps. between -23 and -79[degree] C exhibited approx. equal motility when thawed after 1 hr. However, on storage those maintained at the warmer temps. (-23 to -51[degree] C) declined in motility much more rapidly than did those at the colder temps.