Three experiments were conducted to examine the effects of dilution rates prefreezing and at thawing, pellet volume, and of thawing temperature on the survival and acrosome-morphology of ram spermatozoa. Semen was diluted with a Tris-giucose diluent and frozen in pellet form on dry ice. Best results were obtained with 3- to 8-fold dilution prefreezing. Increasing rate of dilution at thawing improved the results when low prefreezing rates were used, but the reverse occurred with high rates of dilution prefreezing. Recovery of spermatozoa after thawing in dry tubes was satisfactory only when the semen was diluted 3-fold or at higher rates before freezing, Post-thawing survival of spermatozoa frozen and thawed in this way also equalled survival of cells thawed and incubated in a solution, In the final experiment, temperature recordings showed that freezing and thawing velocities of pellet-frozen semen were affected significantly by pellet volume, thawing temperature and dilution rate at thawing. The latter two factors also had an influence on the survival and acrosome-morphology of spermatozoa. Both higher thawing temperatures and thawing of the pellets in a solution acted beneficially on the viability and maintenance of acrosome-integrity of the cells following the freeze-thaw-incubation procedures.
"Experientia docet" - Experience is the best teacher