CRYOGENIC DAMAGE BOAR SPERMATOZOA FROZEN IN PELLETS AND IN TUBES

We studied the effect of the newly synthesized cryoprotectant EPG-20 ( polyethylene glycol ester with polyunsaturated fatty acids, mol.mass 2 0 kD) on the freezability of boar spermatozoa, Semen samples were froz en by the pelleting method of Nagase-Niwa, as well as in 20-ml aluminu m tubes. The addition of 0.5 % EPG-20 to the Serdica cryoprotective me dium preserved the semen quality to a greater extent than the control medium containing no EPG-20. It was found that freezing in aluminum tu bes resulted in higher sperm motility, survival rates and percentage o f intact spermatozoa than when cells were frozen in the form of pellet s, the differences being statistically significant (p<0.001). Electron -microscopic observations revealed that the medium supplemented with E PG-20 manifested better protective effects on sperm ultrastructure. Hi ghest cryosensitivity was recorded in sperm head plasmalemma, acrosome and mitochondria. The nucleus and axial complex displayed a relative cryoresistance.