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Determination of optimum stallion semen freezing regimes

100%

Kutra J. , Pileckas V. , Urbsys A. , Siukscius A. , Nainiene R.

tom 64

nr 02

Semen cryopreservation opens new possibilities for the development of breeding work and preservation of the gene pool in horse breeding. Currently a relatively small number of mares are being inseminated with frozen semen. Therefore, the improvement of semen deep-freezing and thawing regimes is important for further studies of stallion semen cryopreservation processes. The methods of animal semen freezing on dry ice and in convectional liquid nitrogen vapor stream are carried out by simple technical means, and, what is more, large quantities of semen can be frozen at a time. However, programmed equipment involving a larger input allows the implementation and reproduction of desirable freezing regimes more accurately and to extend the range of their parameters. The semen was frozen in two ways: in convectional liquid nitrogen vapor stream on a metal perforated shield, fitted in biostorage KS-40 equipment and in Minicool AS-25. Three freezing regimes characterized by the super cooling temperature of the free water in the semen were realized using the Minicool AS-25 equipment. The efficiency of the freezing regimes was determined by post-thaw motility of spermatozoa. The results from the study indicated that the quality of frozen semen of most stallions was invariable regardless of freezing methods and regimes. Thus, semen can be frozen by convection flow of nitrogen vapor using common equipment and lower amounts of freezing agent. Optimum freezing regimes should be sought for cryopreservation of stallion semen known as “unstable freezing”. These regimes could be ensured by using the equipment suited to the reproduction of the identical freezing regime for every specific stallion’s semen. During the experiment there was only one stallion identified as having an optimum semen freezing regime, yet the experiment showed that in order to reach optimum conditions, a freezing parameter changing gradient could be determined in stallion semen cryopreservation. In the latter case the parameter characterizing freezing regimes could be the super freezing temperature of the free water in the semen and the optimum criterion could be post-thaw motility of spermatozoa.