Optimal Mode to Thaw Cryopreserved Sperm of Holstein Bull Sires

Abstract

A b s t r a c tAs milk yielding increases, the number of animals with defective sexual cycles and quiet manifestations of hunting grows, and therefore there is a need for semen with high quality. Also, at artificial insemination, after dilution of the native semen, packaging, cryopreservation and thawing, the number of spermatozoa per sperm dose decreases. This also necessitates semen with high quality parameters. One of the key stages of the standard processing of cryopreserved bovine semen prior to artificial insemination is the thawing procedure. Therefore, cryopreservation and thawing procedures should be optimized with regard to the proposed modifications of these methods and the changing reproductive abilities of animals. In our study, we compared the effects of previously recommended thawing protocols and those proposed by us on the safety of spermatozoa of Russian Holstein sires and identified the modes that reliably provide a prolonged positive effect on the quality characteristics of spermatozoa and better preservation of their viability after thawing. The semen of 6-7 year-old Holstein bulls was cryopreserved in polypropylene straws (72 doses) with the use of the IMV Technology equipment (France) and in uncoated pellets (90 doses) on the dry ice plates according to GOST State Standard 26030-2015 and the National Technology for Freezing and Handling Semen of Pedigree Bull Sires. Thus, 162 semen doses 0.25 ml each were analyzed. The sperm motility and movement velocity parameters were assessed immediately and after in vitro post-thawed incubation for 5 to 24 hours at 38 С. The percentage of motile semen was visually assessed with the Olympus microscope CX41 (Japan) at ½150 magnification. Thereafter, in the same samples the motility (%), the number of the highly motile sperm (%), and the sperm velocity (mcm/sec) were automatically measured with the SFA-500 Sperm Analyzer (Biola Company, Ltd, Russia). The dynamic of thawing temperature up to the final value was measured with the Center 304 thermocouple. It has been ascertained that the effects of different procedures used for thawing straws and pellets are quite steady and approximately the same. However, the best results of the male sex cell survival after the long in-vitro incubation period (for 24 hours at the animal body temperature of 38 С) are in the samples thawed in a water bath at 38 С for 10 sec when compared to those for the other methods (p < 0.001).For more than 70-year history of cryopreservation for male germ cells, the method has been widely used both in research programs on biodiversity conservation [1] and for commercial purposes in the creation of sperm banks of different animal species [2] and human [3]. Such a long history of the issue allows researchers to discuss not only the achievements but also the risks of artificial insemination [4,5]. It is believed that the increase in milk production has a neg-